"It’s not so much a question of getting online, it’s knowing what to do once you get there," spoke David Friedman, the Director of the Center for Improved Engineering and Science Education (CIESE) at Stevens Institute of Technology (Alex, 1999). The usability of an educational web site is important to achieve successful use in the classroom. A usable design cycle is the guideline for this project to create a useable, motivational, educational web site. The first stage of the process, gearing-up, consists of the research and background detailed in Chapters Two and Three. The initial design phase and the iterative design phase culminate in the final design of the Cracking Dams module and WebQuests as described in this chapter. The evaluation and redesign cycle results of the iterative design phase and the integration results of the system installation phase, the fourth step in the design process, are detailed in Chapter Five.

The objectives of the web site are to teach engineering skills, an understanding of civil and environmental engineering, the use of simulation in engineering, and the impacts of engineering on society. The subjects of fracture mechanics and dams are used to do this because of their compelling nature and applications for computer simulation as discussed in the last chapter. With the objectives in mind, the main sections of the module are designed: Introduction, Dams, Cracks, Case Histories, Scenarios, and Simulation. As seen in Chapter Two, successful web projects are often based on the integration of a number of learning theories. A combination of several learning theories is thus employed to design the WebQuests to support motivation, focus, and critical thinking in the education of K-12 on fracture mechanics and dams.

These learning theories include collaborative, constructivist, problem-based learning, case-based reasoning, and scaffolding theories; examples of the application of these theories in the web site project are noted below. In addition, the Cracking Dams module and the WebQuests take advantage of the non-linear, interactive, multimedia nature of the web. This chapter details the design and structure of the web site, including the appearance, navigation, content of the module, and WebQuests for use with the module. First, the tools used to create the web site are discussed.

HTML, web-forms, Java, JavaScript, animation, Adobe Premiere®, and Adobe Photoshop® are used to create the web site. Each of the webpages is written in HTML (HyperText Markup Language). Several editors are available for writing pages in HTML; most word processing packages can convert a text document to an HTML document. For this project, the pages were written without an HTML editor, which entails adding the HTML tags by hand. Tags are indicators denoted by < > and specify a font size, image location, or other details like these. There are two main formatting options in HTML, tables and frames. Tables are used in this web site to avoid alienating those with browsers that are incapable of handling frames.

The rest of the tools listed above were used to create the interactive multimedia for the site. A web-form is written in HTML and allows the user to input information using interfaces such as radio buttons, check boxes, and text boxes. That information can be manipulated using a CGI-script written in a language such as Perl©. CGI stands for Common Gateway Interface; a CGI-script is a program that can output dynamic information to a web server. In the Scenarios section, for example, a CGI-script takes the information from a web-form and produces an estimation of the loss of life due to a dam failure.

Java is an object-oriented programming language that is used to create applets, which are graphical applications embeddable in a webpage. Java applets tend to be very interactive. In this project, Java applets provide a Search function and allow the user to perform a computer simulation. Several versions of Java are available; the later the version of Java used to write an applet, the later the version of browser required to use the applet. For example, Java 1.1 is understood by the browsers Netscape 4.0 and later versions and Internet Explorer 4.0 and later versions. For this project, Java 1.0.2 is used, which is compatible with Netscape 2.0 and later and Internet Explorer 3.0 and later, to ensure that the large majority of people are able to use the applet. It is reasonable to assume Netscape users will at least have version 2.0 because upgrades are freely available from the web. The applets are discussed further in sections 4.4.6.2 and 4.4.7.1.

JavaScript is programming language that can be embedded in webpages to create executable content. Some people turn the JavaScript feature of their browser off and Internet Explorer 2.0 does not support JavaScript. In these cases, an error would normally appear when a person enters a page that uses JavaScript; this often sends the user away. To avoid this, the JavaScript programs in this web site do not run unless the browser is capable and the function is turned on; thus no error message appears. In this project, JavaScript is used to open new browser windows and create roll-overs. In some cases, if a user clicks on a hyperlink, the new webpage they would normally move to opens in a new browser window instead, as directed by a JavaScript program. This allows the user to view two pages simultaneously, such as a page of text and a glossary word definition. As explained earlier, a roll-over program allows one image to be replaced by another when the user rolls the mouse over a specified location on the webpage. In some cases roll-overs are used to help the user realize where he or she is point on the page, making it an important navigational tool. Roll-overs also foster interactivity by causing a dynamic change in the page in response to a user’s action. Roll-overs are used in the side menu, title image, and the change the main image of a page.

A GIF (Graphics Interchange Format) is a file format used to display color graphics and images on the web. An animated GIF is a series of GIF images that have been strung together to appear like a movie when played back. Animated GIFs use motion to draw the user’s attention to it. As noted earlier, animations may be ignored if they resemble advertisements; care has been taken to avoid that issue on this web site. The program GIFmerge© is free software created by Mark Podlipec and was used to create animated GIFs in this project. The creator can specify how long each GIF, or frame of the movie, is displayed. One may also specify how many times the movie should be played, or looped. The size of the animated GIF is often only slightly larger than any one GIF that is used in the animation; thus download time is not compromised by using animated GIFs instead of regular GIFs. Examples of animated GIFs on this web site are the cracking dam on the main page and the "quick movies" of each step of the simulation. The former is used to grab the user’s attention and interest; the latter shows the user how the simulation applet is used.

Finally, the commercial packages Adobe Premiere and Adobe Photoshop were used to create Quicktime movies and images, respectively. On this site, Quicktime movies include clips from Superman, Asteroid, Dambusters, and video footage of the Teton Dam failure in 1977. Adobe Photoshop allows one to create and manipulate images. The SimScience logo, the Cracking Dams logos, and the side menu images were created and modified in Photoshop. Many photographs were also scanned for display on the web site. Photoshop was used to add a shadow to the photographs, giving the pages a three-dimensional quality.

Important aspects of the appearance of the web site are organization, communication, and consistency (Baecker et al, 1995). Organization is achieved with a clear and consistent layout on each individual page and a logical structuring of the entire site. Effective communication requires clarity of content and meaningful use of interaction and multimedia. Consistency is necessary to achieve both organization and effective communication by helping the user know what to expect and how to respond. Certain consistencies across all four SimScience modules are maintained. There are also a number of points of consistency within the Cracking Dams module itself.

Consistency among all four modules of SimScience is achieved with a basic layout and supporting sections. The basic layout for most pages of each module is a one-inch black band along the left edge of the page with a white background on the rest of the page. Merged with the black band on the left, each page has the module’s title image at the top, a side menu underneath, and the SimScience logo at the bottom. In the center of the bottom of the page, following any content, are the forward and back button icons which link to the next and previous pages, respectively. Finally, the decision to use tables instead of frames on all the modules was made three years ago at the inception of the project, when use of frames had more negative implications. Although recent browser versions have eliminated most problems with frames, all of the modules still use tables in the event a school may still be using an older browser.

Each module is divided into three levels of complexity, Beginning, Intermediate, and Advanced. Each level has a corresponding color: rainbow/green for Beginning, blue for Intermediate, and red for Advanced. For each level, the module title image and the side menu are in the color of the level. Color is suggested by Marcus (1995) to group related items, in this case, web pages of the same level of complexity. The title logo for each level also includes the name of the level. The main version of the logo is used on all pages that may be accessed by any level of the module, such as the Search or Cracking the News. This logo does not have a level name on it and is not associated with any of the levels, which helps the user realize that this page can be accessed at any level of the module. The title images and SimScience logo were originally designed in Photoshop by a team from the Syracuse University Art Media Studies Department. The consistency across modules with respect to the colors and other features mentioned gives the user clues to the fact that he or she is in a SimScience module and clues to determine in which module and level he or she is.

Sections that are included in each of the modules include Help, a Glossary of definitions that pop-up in a new window, a Search feature, and a Site Index or Map. Each of these can be accessed from the side menu that is located directly under the title logo for each module. As a result, the user can expect to find any of these supporting sections in any of the modules, providing reliable aid with navigation or content. This consistency in layout and core content achieve organization by setting standards that are followed by all modules of SimScience. Effective communication through layout and core sections results when a user expects to find navigational clues or aid from these and consistently does.

Particular to the Cracking Dams module, a certain consistency is also maintained with respect to the layout and the use of text and multimedia. In general, a page has no more than two columns of text and images. The images are not included just to take up space; they are referenced by the text. Most images are kept to a file size of 200 KB or below in an effort to minimize download time. Pages were designed for a screen width of 700 pixels; thus when the pages are viewed with 14 inch or greater monitor with a resolution of at least 800x600 pixels, no horizontal scrolling is required. The resolution width of 700 pixels was chosen based on an informal survey of local schools. A 14 or 15 inch monitor with a resolution of 800x600 pixels was the most common in this survey. Resolution width was reduced from 800 to 700 pixels because some space is occupied by the browser window. Many pages require vertical scrolling, although this is much more accepted than horizontal scrolling (Nielsen, 1999).

With respect to the text itself, suggestions found in literature were followed. In most cases, the length of a line of text is less than 60 characters, uses less than three typefaces, and is aligned left (Marcus, 1995). Text is only underlined if it is a link, an important navigational clue. In an effort to keep the reader interested in the Advanced and Intermediate levels, text is presented in chunks (short paragraphs) or bulleted form as suggested by Guzdial et al (1997); each chunk is usually accompanied by an image as Baecker et al (1995) suggest. Text is kept to a minimum in the Beginning level and is always accompanied by an image or icon in consideration of the reading level of K-4. A small cee icon is used to point out sections in the text that refer to a process or application in civil and environmental engineering. This icon helps the user make connections between what he or she is learning about cracks and dams and what a civil engineer does.

Once again, the organization of the layout is consistent across the module, achieving effective communication of both the educational content, by using formatting shown to have positive benefits, and of the navigational clues, by helping the user know what to expect.

As suggested in the literature (Laurillard, 1998), a number of navigational options are provided to allow the user to take advantage of the hyperlinked nature of the web. This facilitates non-linear movement and the ability to browse. Options for navigation include the side menu, the site index, links, the forward and back buttons, and the title images. The side menu is found on the left of each page under the title image. Roll-overs are used to make the use of the side menu interactive and helps the user know where the mouse is pointing. As the user rolls over a menu option, the option changes to a reversed black and white to help the user realize where he or she is pointing. On the menu, the current section of the module is highlighted in red, blue or green for the Advanced, Intermediate, and Beginning levels, respectively; the other sections are in white and black. By highlighting the current section the user sees what part of the level he or she is in and where that is in relation to the other parts of the level. Each option links to the beginning of that section or subsection. Each option also has a meaningful name to help the user choose, as suggested by Schneiderman (1995). The menu allows the user to move in and out of the sections more easily than if he or she had to proceed linearly through all of the pages to reach the next section.

One choice in the side menu is the Site Index. This choice leads to an index of links to all pages of the module that are not part of a specific level (Acknowledgements, Cracking the News, etc…) as well as links to a separate index for each level. In this way, the main index is visible in one screen, with no vertical scrolling, as suggested in the literature (Baecker et al, 1995). An index that requires vertical scrolling suggests to the user that the links at the top of the page are more important than those not visible. In this case, no precedence for the links is desired so the links are kept to one page. The indices for each level include links to all pages in that level and a link back to the main index. These indices are much longer and do require vertical scrolling. Links to the sections on Cracks and Dams appear at the top, encouraging the user to visit these sections first.

Within the text there are numerous links to other parts of the module, other modules, and other web sites. Linking within the module reflects the interrelated nature of fracture, dams, and their societal effects. Links outside SimScience are followed by a (#) to indicate that the user will be leaving the SimScience site by following that link. This is especially important on the CD-ROM version of SimScience; users of the CD-ROM will likely not have Internet access and will need to know which links they cannot follow. External pages often open in a new browser window so that the user does not get lost trying to get back to Cracking Dams; this is accomplished using JavaScript.

The forward and back buttons follow the main content of every page, linking to a next and previous page. An "alt tag," a short description of an image, pops up when the user points to one of these buttons with the mouse. The alt tag gives the name of the page to which the forward or back button links. These buttons create the option for linear movement through the site, offering some constraint for the user. This linear option is discussed further in the Content section below. If this option is used, the alt tags help the user know where he or she has come from or is going.

Finally, the module title logo and SimScience logo appear on every page. The module title logo appears in the upper left corner of the page and links to the main page of the module, as the user might expect (Nielsen, 1999). The SimScience logo, appearing below the side menu on the left, links back to the main page of the SimScience site. Each of these options for navigation promotes non-linear, independent movement through the web site.

At the main SimScience page (https://sethna.lassp.cornell.edu/SimScience), the user sees a brief description of each module of SimScience. From here the user enters the Cracking Dams module. The main page of the Cracking Dams module displays an animated GIF of a simulated crack opening in a dam. This is a foreshadowing of the simulation the user is able to perform in the Simulation section. A small fish swimming into the crack helps the user realize that this is a dam with water on one side. The user is asked to choose a level, Beginning, Intermediate, or Advanced, to continue. Links to several of the supporting sections are also provided on this page.

The Cracking Dams module (https://sethna.lassp.cornell.edu/SimScience/cracks/) intends to present ideas by building on the user’s existing knowledge, starting out simply, and building in complexity. The Advanced level is the most complex and assumes basic knowledge of high school level math and science, particularly the basics of algebra, geometry, trigonometry, calculus, physics, and chemistry. Concepts used in the module from these subjects are explained for the lower end of the suggested age group (grades 9-12). The Intermediate level is similar to the Advanced level in content and layout, although there is less content and it is less complex, being aimed at grades 5-8. The Intermediate level assumes basic knowledge of the following math skills: computation, fractions and decimals, geometry, and measurement. It assumes basics knowledge of the following science concepts: forces, energy, motion, work. Most of these skills are introduced beginning in 5^th grade. The Beginning level does not contain all the sections that are in the Advanced and Intermediate levels and content is simple and often iconic, images dominating the text. The sections of the Advanced and Intermediate levels are discussed below; it is noted when the Advanced level includes something the Intermediate level does not. The Beginning level is discussed on its own.

Some content in the Advanced level was developed by students who worked on the module prior to the start of this thesis project. Content existed in the Dams section introduction and in the Dam Types sections. This content was modified slightly and built on by the author.

Each level is structured to allow a linear progression through each section using the forward and back buttons at the bottom of the page. Thus the order of the sections is important to create a logical progression through the site. From the Intro page, the forward button takes the user to the Dams section to begin with the less technical of the two subjects of cracks and dams. Once the user has learned about dams, these structures become a vehicle for the user to learn about cracks; thus the Cracks section is next. The Cracks and Dams sections are meant to build on existing knowledge. They also provide a base of knowledge on which to build in the Case Histories, Scenarios, and Simulation sections. The Case Histories section then shows the user examples of real world applications of fracture mechanics to concrete dams. Finally, the user can apply both the social and technical knowledge learned in these sections in the Scenarios and Simulation sections. At the end of each section, the user is not given the option to move forward to the next section using the forward button; he or she must choose the next section from the side menu and is instructed to do so. Thus the user realizes that he or she is moving to the next section and the change of topic does not seem so abrupt. There are also several supporting sections, such as the Dam News, that are not part of the linear movement but can be accessed at certain points to help or motivate. Use of the linear path of the site provides the user with a wide range of information on dams and fracture, provokes thought on the societal impacts of both, and culminates in the user examining a scenario of dam failure and performing a simulation of dam cracking on their own.

Several WebQuests (Bernie Dodge and Tom March’s concept), have been developed to provide a framework, much like a lesson plan, for using the module in the classroom. The WebQuests have specific tasks to provide motivation for collaborative problem-solving. The Advanced level WebQuests also encourage case-based reasoning. The WebQuest provides an outline of how the group should move through the module to complete the task. Although not every section is touched on in the WebQuest, the sequence suggested in the WebQuest is very similar to that of the linear path through the site. The WebQuests are discussed further in section 4.5. On the intro page of each level, it is noted that the user may choose to follow the linear path using the forward buttons or use a WebQuest suggested for that level.

The sections discussed below include the Intro, Dams, Cracks, Case Histories, Scenarios, Simulation, and supporting sections. The content of and motivation for each section of the module are described in consideration of the learning objectives and theories described earlier.

From the main page of the module, the user must choose a level, Beginning, Intermediate or Advanced. The Intro page is the first page the user encounters in all three levels; it needs to draw the user in and excite him or her to learn about cracking and dams. This page gives a preview of what the module is all about. A link is provided to a page called Applications, which gives the student and the teacher an idea of what math and science subjects are applied in that level. A still image from the movie Superman dominates the Intro page; a play button links to a clip from the movie of the Hoover Dam cracking and failing. This clip allows the user to begin with something that is likely familiar entertainment, the depiction of a dramatic scene relevant to the subjects of the module. Entertainment becomes educational in the context of the module; scaffolded by the questions next to the still image, the user wonders, why is the dam cracking? What are the forces involved? He or she is led on to learn about dams as societal structures.

From the intro page, the user may choose to begin moving linearly through the level by using the forward button; jump to a particular section from the side menu or Site Index; or move to the WebQuests page to choose an activity as described later in this chapter. The Intro page thus draws the user in with something familiar, building on existing knowledge, and provides several choices for his or her next move. The Intro page of each level can be returned to by choosing Intro from the side menu.

The Dams section is the first section the user sees in the module, in both the linear option and in the WebQuests. This section teaches the user concepts about Dams that are then applied in the Cracks, Case History, Scenario, and Simulation sections. It is non-technical at first, drawing the user in by pointing out ways the user might receive the services dams provide. The social and environmental impacts of dams are discussed, to present the big picture of dams to the user. As the section develops, dams become a vehicle through which the user can learn about cracking.

The Dams section begins with an introductory page; this page lists and links to the subsections, Societal Nature, Opposition, and Dam Types. It also links to the dam joke, the Dam News, Dam Entertainment and Hometown Dams; these pages provide motivation and current events and are discussed later. Finally, in a typical two-column arrangement, the right-hand column is dominated by a still image of a dam from the movie Dambusters.

The still image links to a Quicktime video clip of the British bombers attacking a German dam during World War II from the movie Dambusters. Below the still is a link to an entire page about the Dam Busters, the historical bombers, and their attempts to destroy enemy dams using "barrel bombs" to cripple the enemy’s factories and plants during wartime. The Dambusters webpage includes three movie clips from the movie Dambusters with an explanation of their story. Permission to use the clips was granted by Canal +, United Kingdom. Titles were added to the clips to help the viewer understand the actions in the clip. These clips accomplish several purposes: a dramatic introduction to the section on dams, a connection between education and entertainment, an example of the historical and societal effects of dams, and a gateway between the Cracking Dams and Fluid Flow modules. Seeing the use of dams in entertainment, the user again realizes the dramatic nature of a dam failure. As the second example of the societal impact of dams used in entertainment, the Dambusters clips provide motivation to learn more about dams and how they affect people. The original movie is based on history, giving the user an understanding of how dams were used as a wartime weapon because of society’s dependence on the services they provide. Finally, the dams were attacked using spinning cylindrical bombs, which allowed the bombs to skip across the water right up next to the dam before exploding. More on this use of fluid flow is described in the Fluid Flow section; a link is provided to make the connection between the Cracking Dams and Fluid Flow modules of SimScience.

This first subsection of Dams, Societal Nature, uses existing knowledge of dams to provide a basis for learning more on dams. A basic definition for dams is given and the term "societal" is described as meaning, "having a great impact on society." Other societal structures are compared to dams. The page also gives an introduction to dams as a product of civil and environmental engineering, which is emphasized for the user by the cee icon on the page. On the next page, the services of dams are described, alerting the user to the fact that he or she probably is the recipient of one of the services, directly or indirectly. This creates a personal connection to the information.

Following the linear sequence of the site, the user next enters the section on the Opposition to dams.

A page on occurrences of dam failure is first in the Opposition subsection. This page begins the counterbalance of the advantages of dams with the disadvantages, the most dramatic and catastrophic being failure. The historic failures of the St. Francis dam in California and the Johnstown flood and dam failure in Pennsylvania are described. These dam failures had great impacts on society – devastation – reinforcing the connection between engineering decisions and their results. The user is reminded that it is also the engineer’s responsibility to be concerned with the safety of dams. Consideration of the safety of dams and the impact of a dam failure are available in the Scenarios section; a link is provided. After seeing dam failure as one reason for opposition to dams, the user is led to the next page, which details several controversial dams and the reasons why people are opposed to them.

These controversies serve to give the user an idea of societal impacts of dams other than failure in a current-events context: endangerment of species, resettlement issues, and inundation of archaeological sites, among others. The dams that are subjects of current debate include the Glen Canyon dam, the Lower Snake River dams, the Three Gorges Dam, and the Edwards Dam. A description of the controversy, both positive and negative aspects of the dam, is given and external links to sites about the controversy are provided. Numerous examples of measures that have been taken recently to improve the environmental impact of dams are provided as well, like fish ladders and dam breaching, for example. All of these measures have been reported in the news recently, which emphasizes the current nature of these problems; a link is provided to the Dam News, which includes the headlines about the environmental impact of dams, among others. The user is also prompted to post a message on an electronic bulletin board concerning their thoughts on the impacts of dams. This promotes reflection on the two sides of the dam issue.

Engineers must consider the advantages, disadvantages, and technical issues when constructing a dam. Having learned about the advantages and disadvantages of dams, the user is led to a technical subsection on the different types of dams. This section supplies much of the information that the user needs to perform a computer simulation of fracture in a dam. The four types of dams the module discusses are concrete gravity, concrete arch, concrete buttress, and embankment. Emphasis is given to concrete dams, as these are often the subjects of computer analysis of fracture. There is an intro page for each dam type that presents the photo of that dam type, a description of the type of rivers or gorges for which that dam type is appropriate, what its advantages and disadvantages are, and links to the pages on its Anatomy, Forces, and History. A photo of a real dam is provided for each type and included on each of the section pages, providing an association between the technical names and forces and reality. The linear buttons lead the user through the Anatomy, Forces, and History sections of each dam type in turn.

The Anatomy page introduces the user to the parts of the dam. The page includes a picture of that dam type, diagrammed with the names of the parts of the dam. Each part name links to a glossary definition that opens in a new, smaller browser window. This arrangement helps to keep the Anatomy page relatively short; if all of the definitions were included directly on that page, too much vertical scrolling would be necessary. In addition, this page discusses other geometrical features of the dam to help the user model a dam for a two-dimensional simulation. An example of a dam modeled for a two-dimensional simulation is shown.

The attachment of the dam to the ground, its fixity, is also discussed on the Anatomy page. The user is shown an example of what fixities to apply for a simulation. The term fixities is not intuitive, so the term attach is used in the Intermediate level and in the simulation applet. Both terms, fixity and attach, are introduced in the Advanced level. How to draw a model of a dam in two dimensions and apply fixities are the first two steps the user learns for performing a simulation. The rest of the steps to perform a simulation are also embedded in the Dams and Cracks section to scaffold the eventual use of the simulation applet. In this way, the entire process of learning about cracks and dams scaffolds the user on how to do a simulation of a fractured dam.

The Forces page follows the anatomy; now familiar with the parts of a dam, some physics are introduced. The main forces on a dam are shown where they act on a dam in a force diagram. The force diagram uses roll-overs to portray each force separately or all of them together as the user rolls over the names of the forces. Using roll-overs creates interactivity and helps uncomplicate the force diagram so the user can learn piece by piece. The forces on the dam are listed, reservoir forces, uplift, and weight of the concrete; each of these links to another page that describes each of these forces. This separate page teaches the user which of the forces to use in a simulation, how to calculate each force, and where each force is applied on the dam in a simulation. This is the third scaffold for how to do a simulation. A new page is used for these explanations to keep the Forces page from getting too long and to give the user the choice of learning about the forces in more detail or moving on.

In the Intermediate level, the force diagram is simplified to reflect the fact that students have not had Physics yet and to simplify the diagram. The triangular distribution of water pressure is not shown and uplift is not shown. Students should be generally familiar with the concept of forces.

Finally, a history of each dam type provides a chronological hypertext description of the development of that dam type accompanied by pictures. This page is the most like a traditional textbook with the added advantage of hyperlinks to the other sections of the module. The hyperlinks enable the user to associate the history of the dam type with the societal impacts as well as the engineering design.

At the end of the Dam Type sections, it is suggested that the user move on to the Cracks section by choosing from the side menu. The forward button does not link to the Cracks section to help the user realize he or she is moving to a new section.

The Cracks section follows the Dams section both in the linear sequence and in the WebQuest because it builds on the knowledge the user has gained in the Dams section. A dam is not only a structure that provides drinking water or kills fish, it is a structure that can crack due to a variety of forces. When he or she arrives at the Cracks section, the user has the chance to learn what makes the cracks grow in dams. The Cracks section teaches the user the final steps needed to do a simulation.

The introduction to the Cracks section begins similarly to the Dams section: links to subsections, a media clip, and links to supporting sections. The subsections include Concrete, Theory, and History. The supporting sections, Cracking the News and Hometown Cracks, help provide motivation and personalization; these are discussed further below in section 4.4.8.2. The media clip is an animated GIF of the propagation of a penny-shaped crack in a block under tension, courtesy of Dr. David Chen. The propagation was simulated in three dimensions using FRANC3D/BES; the animation shows the growth of the crack in color stress contours. This animation provides a dynamic introduction to the capabilities of fracture simulation, motivating the user to learn more about cracking so that he or she will be able to do a simulation as well. An introductory page of cracks in common places follows in an effort to help the user realize the omnipresent nature of cracking and lead them into the first subsection realizing they have a base of existing knowledge of cracks. Another animated GIF created by Dr. David Chen is included on this page to again motivate the user to learn how to do a simulation.

Concrete is the material of choice for dams in the last few decades (International Journal on Hydropower and Dams World Atlas, 1999; Redlinger et al, 1975); concrete is also extremely prone to cracking. In this subsection, first concrete itself is described in terms of the components of which it is composed and the chemical reaction that occurs when they are mixed. Images of concrete mixers and concrete sidewalks draw connections to existing associations to concrete for the user. Next, a description of concrete testing leads to the properties of concrete, giving the user more knowledge about things a civil and environmental engineer must investigate. The design of a concrete mix and the testing of concrete to determine its properties are two things commonly done by civil engineers. Thus the sections describing these processes are marked by the cee icon so the user make the connection to civil and environmental engineering. Finally, the causes of cracking in concrete are described, which leads the user to the theoretical mechanisms of cracking in the next subsection. The main ideas in the Concrete section of the Advanced level remain in the Intermediate level, although the latter has less content on each of the main topics.

This subsection details some basic theory of fracture mechanics in terms of the science and math that should be familiar to the user. Slightly different explanations of fracture mechanics are given in the Advanced and Intermediate levels in recognition of the suggested grade levels. Some physics and calculus are included in the Advanced level that are not included in the Intermediate level; also, some concepts are described more briefly in the Intermediate level than in the Advanced level.

First, the forces that cause cracking in concrete dams, the three modes of fracture, the stress intensity factor, and the energy associated with cracking are described. A discussion of the forces that cause cracking is limited to those that act on dams. There is a hyperlink to the section on dam types, where forces on dams are discussed. Thus the user sees the application of theory to real life. The three modes of fracture describe the three types of load that cause cracking. In Mode I, forces are perpendicular to and in the plane of the crack, opening the crack. In Mode II, forces are again in the plane of cracking, sliding the top face of the crack backward and sliding the bottom face of the crack forward (or vice verse). In Mode III, forces slide the top face of the crack out of plane in one direction and slide the bottom face of the crack out of plane in the other direction (or vice versa). These descriptions alone would not suffice to achieve understanding by the user. Thus they are accompanied both by images that depict the modes and by experiments that the user can perform. For example, the first mode of fracture can be demonstrated using just a piece of paper; a description of a quick experiment provides the user with the opportunity to prove it to himself or herself. The experiment consists of placing a tear in the center of a piece of paper; pulling on the paper parallel to the tear; and pulling on the paper perpendicular to the tear. The learner sees that the tear only grows when force is applied perpendicular to the tear, the first mode of fracture.

Next, the stress intensity factor and crack energy are introduced in basic terms. The stress intensity factors, K_I, K_II, and K_III, are descriptions of the likelihood that a crack can grow in modes I, II, or III, respectively, in a material in a given state. The user can apply this knowledge in the Simulation section, where he or she can actually see the history of K_I in their computer simulation of cracking. Next, the notion that a crack requires energy is introduced, both building on the user’s existing knowledge of the energy in a mass-spring system from physics.

The next topics are crack initiation in dams and crack propagation both generally and in dams. The user sees where cracks are likely to start in different types of dams, another tool for performing a simulation of a cracked dam. Here, the user also sees examples of cracks added to a model for simulation in the web-FRANC2D applet. Then, fracture toughness, K_Ic, is introduced as a property of a material in a given state. When K_I reaches K_Ic, the crack can propagate or grow. Again analogies are used to describe these concepts. For example, for a crack to grow, it needs enough K_I to reach K_Ic; for person to buy something, he or she needs enough money to pay the price. These pages include many links to previous sections, allowing the user to review other things easily and non-linearly. These topics show the user some engineering applications of their math and science skills.

The last page in this section explains stresses and stress contours, introduces the notion of computer simulation of fracture mechanics, and gives some examples of applications of fracture mechanics. Stress is described as the force applied over an area, a prime example of an application of both math and science. A stress contour is described as showing the levels of stress in a model according to color. Stress contours are often the output of computer analysis programs like FRANC2D and web-FRANC2D. Learning about stress contours, the results of a simulation, is the last step in performing a simulation; this knowledge scaffolds the eventual use of the simulation applet. An example image is presented of a web-FRANC2D contour. These contours are displayed on the exaggerated deformed shape of the model to make the crack growth easier to see. Examples of other uses of FRANC2D and FRANC2D show the user real-world needs for fracture simulation in many disciplines, such as mechanical engineering or geotechnical engineering.

The History section of Cracks describes both some of the forefathers of the development of fracture mechanics as well as some of the current researchers in the field. Development of this fracture theory requires as much experimentation as theoretical work, indicative of all types of engineering. Some of the simple experiments that contributed to fracture mechanics are described, such as Inglis’ experiment with a thin glass plate. The learner can see the similarities between Inglis’ experiment and the paper experiment he or she may have tried. Links to current researchers in the field allow the user to explore some of the cutting-edge work being done in fracture mechanics.

The fourth topic in the side menu is Case Histories, the true stories of four dams that have cracked from all over the world as detailed in Chapter Three. El Atazar, Fontana, Kolnbrein, and Malpasset dams have all cracked in the last few decades, Malpasset Dam failing catastrophically, making them subjects of computer simulation for one reason or another. The cases are real-world examples of fracture mechanics applications to concrete dams. Each case has something unique about it, be it the cause of cracking or the solutions employed. But at the same time, each case exhibits similarities in the engineering skills and the iterative design necessary to solve a problem or understand an event. In each case, the engineers had to be creative and persistent to solve the problems in the dams; things did not work out on the first try. Review of these stories provides examples for case-based reasoning of how cracking occurred in concrete dams and what can be done to try to remedy it or understand it.

The user may move to one of the four case histories by clicking on the photo of that dam on the Case History introductory page. Then, on the introductory page for each dam, there are links to the four parts of each story: Background, Problem, Simulations, and Current Status. The Malpasset case history actually does not have a Simulation section as no simulations are publicly available. The simulations performed to try to understand Malpasset’s failure are described in Malpasset’s Problem section. The user can jump to any of these sections of the case history from the introduction page of that case. The Background summarizes the construction and general statistics on the dam, such as dam type, reservoir capacity, and services provided. The Problem recounts the initial notice of cracking through each remedy and its repercussions, making note of the engineering teamwork, reasoning, iterations, and simulations. Images and further description of computer simulations of the dam are presented in Simulations. What is known of the present state of the cracking and the dam is discussed in the Current Status. Throughout the sections, appropriate links to general background on fracture or dams or to similarities in the other case histories are provided to enable non-linear learning and review. The information in each section is in bulleted format for quick comprehension of the steps taken at each point in the history. Since the histories are quite complicated at some points, the bulleted format helps to present the problem and solutions piece by piece.

Malpasset plainly affected society with its failure; El Atazar also had some effect on society considering the initial secrecy regarding cracking. The cost of repair and rehabilitation and lost services if the dam had to be taken out of service for repair certainly had their societal impacts. But no documentation exists detailing any other major societal impacts of these four dams. The Sierra Club’s book, The Social and Environmental Effects of Large Dams, makes no mention of any of these four dams other than Malpasset’s failure (Goldsmith and Hildyard, 1984). This is not to say that no other impacts were made by these dams; certainly, some resettlement probably occurred for the construction of the dam and filling of the reservoir. Most likely there have been environmental effects as well, but these are not widely documented. Thus, the civil and environmental engineering skills and simulation are emphasized in these case histories and provide substantial opportunities for the use of case-based reasoning of the engineering of cracks.

Following the Case Histories, Scenarios appears on the side menu. The Scenarios section leads the user to think more about the different times in the life of a dam, now that he or she has seen some examples of how engineers have historically responded to fractures in dams. This section is intended to evoke a personal response to the different issues surrounding dams and fracture. Users have the opportunity to share their responses on the bulletin board, which has topics dedicated to the issues raised in the Scenarios section.

The topics of the Scenarios section include Planning a dam, Construction of a dam, estimation of loss of life due to dam failure, and a brief look at some recent dam failures. The Intermediate level does not include Planning or Construction to make this section shorter. The Scenarios opening page gives the user links to each of these choices. It also presents an unusual scenario from Hollywood: the failure of a dam due to the impact of an asteroid. The NBC made-for-TV movie Asteroid includes a clip showing the dramatic failure of a dam that has been hit by an asteroid. Such a scenario, though unlikely, shows an unexpected implication of trying to harness a river. The clip of the failure from the movie is available for viewing in the form of a Quicktime movie, used under the Fair Use Doctrine (US Copyright Office, 1999). Viewing the clip helps the user to consider the implications of such a scenario; should dams be built knowing that they may be impacted by foreign objects, causing catastrophic failure that may not have occurred otherwise? A link is also provided to another unimaginable but, this time, true scenario, the story of the Dam Busters, bombers who succeeded in breaching enemy dams in wartime.

The Planning and Construction pages give the user a brief outline of the steps in these general scenarios. Each step on the Planning page also provides a point for reflection and then comment to an electronic bulletin board. For example, the engineers and officials must weigh the services the dam will provide against the initial startup and maintenance costs, resettlement of peoples, and environmental effects; is the construction of a dam that will primarily provide flood control and possibly save lives but displace 80,000 people justified? What other factors should be examined in this decision? Historical examples are used whenever possible. A direct link to the bulletin board is provided for comment; a special thread is set up on the bulletin board for this particular issue to gather all the related comments in one place. Each step on the Construction page is accompanied by a photo and a historical fact.

The consideration of lives lost due to failure of a dam is a morbid but important one, so this page is interactive to draw the user’s attention. A simple web-form/CGI-script allow the user to estimate loss of life according to an algorithm by Brown and Graham (1988). The web-form allows the user to input values for several variables, including the number of people at risk, the warning time, and the landscape. The user submits their values for computation in Brown and Graham’s formula. Computation is executed by a CGI-script written in Perl that returns an estimated value for the loss of life under those conditions on a new web page. The basis for the script is available on the web as written by Seth Golub at http://www.thehouse.org/txt2html/; for this project, the author modified the script to perform the needed calculation. Brown and Graham’s algorithm is as follows: loss of life estimation = population at risk/{6.207*[(5.838*warning time)-X]}. The algorithm is presented on the site this way as well as using variables: E = P/{6.207*[(5.838T)-X]}. With the equation in both forms, the user sees an application of algebra. The user is also encouraged to look up the population of their city or of a city near a dam in which he or she is interested in the US Census Bureau database. Using this population for the number of lives at risk in the estimation provides a personal connection.

The user is then asked to consider the factors taken into account in the algorithm. What is the sensitivity of the algorithm to each factor? What other factors would the user include in the algorithm? Again, a thread in the bulletin board is provided for discussion of this topic. The next page describes another algorithm by DeKay and McClelland (1993) and their predictions for lives lost in several dam failures, with comparisons to actual lives lost. There is an opportunity for the user to compare the two algorithms and actual lives lost due to failure. DeKay and McClelland’s algorithm is slightly more complicated than Brown and Graham’s and is again presented both this way and in algebraic format: loss of life estimation = .146 - .478*[ln(population at risk)] - 1.518*(warning time). The following page shows a diagram of a wide range of factors that affect the failure of a dam published by Stedinger et al (1996). The diagram helps give the user some idea of how many factors can affect the estimation and probability of an event (not included in the Intermediate level). It leads into the final page of the Scenarios section on recent dam failures.

Each of the dam failures on the final Scenarios page has occurred relatively recently. The Los Frailes tailings dam in Spain failed in April of 1998 and has made the news frequently in the year since the failure, during attempts to place blame for the failure. A hyperlink is provided to the recent news headlines listed in the Dam News page. The Teton Dam failed in 1977, one of the most recent failures that resulted in a loss of life, fourteen people. KIDK-TV in Idaho provided the SimScience project a short clip of actual footage from the failure. A spillway gate on the Folsom Dam in California failed in 1995 resulting in flooding; this dam has made the new recently, as well, and links are provided to the headlines in the Dam News. Links to several dam safety organizations are listed to counterbalance this negative point about dams. By showing the user not only failures of dams but also engineers concerned with dam safety, the user can see the response of the engineering community to a historical problem.

The Simulation section has four main pages, two pages of introduction, the simulation applet page, and the understanding results page. This section is the interactive culmination of what the user has learned about cracking in dams so far. This is the chance for the user to truly be the engineer, to create a model of a dam and simulate cracking in it. The cee icon is placed in this section to remind the user that these are functions of an engineer.

The first introductory page helps the user understand what computer simulations are and why engineers use them. Next there is a review of the major steps to do a simulation using the web-FRANC2D applet: drawing the scale model; adding fixities; applying loads; specifying the crack(s’) length(s) and location(s); and understanding the results. Each step is accompanied by an image of what the model should look like in web-FRANC2D and an animated GIF showing how each step is performed. These steps and the still images were previously introduced to the user at appropriate points in the web site. Hyperlinks are provided back to these points for both arch and gravity dams. For example, the user needs to apply forces to their model; an image of a model with forces on it depicts this step. This image is also in the section about the forces on dams, allowing the user to associate this step in the simulation with the reality of forces on dams. The inclusion of the images of the simulation steps within the parts of the web site leading to the simulation and then again just before the simulation scaffolds the student’s use of the web-FRANC2D applet. By the time the user does the simulation, he or she has seen all the tools to do a simulation with web-FRANC2D applet twice.

The user interface for web-FRANC2D is a Java applet, which is a program written in the platform-independent language Java. This means the program can run on most Internet browsers, whether the person is using a Mac, Windows, or some other platform. The main applet was written by Cornell Physics graduate student Paul Houle. Matthew Kuntz, also a Physics graduate student, contributed a Configuration section to the applet, mainly for use during the development stages of the applet. The author of this thesis made several minor changes and undergraduate Gregory Clinton contributed to the applet in the final stages of the project. The applet is written in Java 1.0.2, although newer versions of Java are available, in an effort to keep the applet usable on Netscape 2.0 and later and Internet Explorer 3.0 and later. Three CGI-scripts written in Perl and several C programs interface between the Java applet and the web-FRANC2D program. These programs all reside on a computer running Red Hat Linux©, where they will remain for the life of the web site.

There are several "quick movies" available on the applet page. These "quick movies" are the animated GIFs that show the user how to perform a step of the simulation (also available from the previous page) including the following: drawing and deleting; adding fixities; adding loads; adding cracks; running FRANC2D; and viewing output. Each of these animated GIFs opens in a new, smaller browser window to avoid clutter on the page. After viewing these clips, users should be better able to perform a simulation. In the WebQuests, students are encouraged to use consistent units of kilo-pounds and feet in the calculations for their analysis, although most measurements in the module are given in both English and metric units.

The user initially sees a grid on a black background with several buttons to the left. The buttons to the left are always arranged in two groups, a top group and a bottom group. The top group remains the same throughout the applet. This group consists of Autoscale and Zoom buttons that allow the user to change his or her perspective of the model as the button names indicate. The bottom group of buttons changes as the user progresses through the applet.

On the grid, the user draws the outline of his or her model, which must be a closed shape. To close the shape with the final line, the user must click "Close." Interior edges may be added and lines may be deleted. Once the model outline is complete, the user presses "Mesh" and the applet sends the information to a meshing program via a CGI-script. The applet receives a mesh for the structure, which it displays for the user. The mesh is a set of six-noded triangles that allows the web-FRANC2D program to perform a finite element simulation on the model. A brief explanation on why the structure is broken into triangles is given in the tutorial, which is explained below. Several new buttons appear to the left of the grid: Attach, Add Loads, Add Cracks, and Move on. The user should choose each of these, as directed by the movies, from top to bottom.

In attach, the user must apply fixities, in essence, tell the program where the structure is attached to the ground. Although "fixities" is the technical term, it is not intuitive, so "attach" is used. Points that are attached bear a red dot. Earlier explanation on dam foundations in the Anatomy page for each dam type tells the user that the dam should be attached to the ground along the dam’s bottom edge. Thus he or she must click along the bottom edge to "attach" the model, telling the program that the dam cannot move along that edge. The user can "undo" a step by clicking on the Undo button. The user clicks on "Done" to move on to the next option.

In Add Loads, the user must tell the program where there are forces acting on the dam, which appear as yellow dots. The main forces the module suggests to include in a simulation are the force of the water from the reservoir and the weight of the dam. The free body diagrams in each Dam Type Forces section gives the user an idea of where these forces should act on a dam. He or she may also want to calculate the weight of the dam or try to figure out the best way to apply the force of the water as proportional to the depth of the water. The user is shown how these calculations are performed previously. Again, the user can Undo and must click Done to move on.

In Add Cracks the user places cracks in his or her structure; the cracks appear in green. The cracks must start from an outside edge and be approximately the same size as one of the triangles. Normally, FRANC2D only accepts cracks that start on corner nodes (corners of the triangles), but Dr. Bruce Carter adapted web-FRANC2D to accept a crack that starts on a mid-side node (the middle of a side of a triangle) and then move the crack to the nearest corner node. This adaptation was necessary to try to account for human error. The user can remove the previous crack added by clicking on Undo. The user must click on Done to continue.

To continue, the user should click on Move on. A new set of buttons appears to the bottom left of the grid. Of the bottom set, only the "Run FRANC2D" button should be enabled, although some browsers do not support this. The user should click on this button to send the information to web-FRANC2D, again via a Perl CGI-script. At this time, the Run button is disabled. This is done to disallow the user to click the button repeatedly as was happening during the evaluations. Each time the button is clicked web-FRANC2D begins another analysis. The more analyses running, the slower the results are returned. Web-FRANC2D processes the information and does the finite element analysis, automatically propagating the crack five increments of 0.1 length unit, regardless of K_Ic. Interested users may see the details of the analysis, such as material properties and problem type, by clicking on the link to simulation details. When the simulation is finished, web-FRANC2D returns five stress contours of the first principal stress on deformed shapes of the dam, although the concept of first principle stress is not introduced in the module. The user may move through the contours by clicking on the Next button, which should now be enabled. The Previous button should also be enabled and will move the user back through the contours to the first. The user should understand the notion of stress contours based on what he or she learned in the Cracks Theory section. It is also explained further in the Simulation results page, which is next.

If multiple cracks are modeled in web-FRANC2D, the crack with the greatest K_I grows the most and other cracks grow an amount proportional to their K_I.

The user may also request to see the stress intensity factor (sif) history for all cracks; the stress intensity factor (K_I) is a fracture parameter that he or she learned about in the Cracks Theory section. When the user clicks on the button that says, "show me the sifs," a new browser window opens with the sif history for his or her crack or cracks. If multiple cracks were modeled, the user is able to deduce that the crack that grew the most has the highest sif, applying what he or she learned earlier.

A possible point for comparison of analyses is if a crack can be modeled with and without water pressure. This possibility was investigated during this project but not adequately complete. This addition to the applet is suggested for future work.

There are several other links on the simulation applet page. First, there is a link to the simulation applet tutorial. The simulation applet tutorial is intended for the teacher, as he or she is not expected to have performed an engineering simulation before. The tutorial walks him or her through the steps of doing a simulation with the applet, to give him or her an idea of what to expect and do at each step, making use of the applet more comfortable and familiar. There are also links to download Netscape and to post comments or results on the electronic bulletin board from the simulation applet page.

This page of the simulation section is intended to review the results the applet returned. Some explanation of why the crack may or may not have grown is presented. Suggestions are provided on how to change the simulation to make the crack grown if the crack did not grow during the simulation. There are also suggestions on variations to try in the simulation applet so that comparisons may be made. The stress contours are again discussed as being color contours of where the dam feels forces/stresses. Various links are provided to direct the user to earlier points in the module that might help the user reexamine concepts. Suggestions for other variations of the simulation are listed. The user is asked to post his or her results on the bulletin board to share with others.

Supporting sections for Cracking Dams provide information to help, further motivate the user, provide general information, or promote communication. Supporting sections for help include Search, Glossary, Site Index, and Help. Supporting sections for motivation include the Quiz, Summary, WebQuests, Hometown Cracks, Hometown Dams, Dam News, Cracking the News, and Dam Entertainment. General information sections include Authors, Acknowledgements, Goals, and References. Communication is promoted by an electronic bulletin board as described below.

The Search page allows the user to search the module for keywords using another Java applet. The applet was written by Dr. Simeon Warner, during the time he was a Post-Doc in Physics at Syracuse University. The search may be restricted to a particular level or may span all levels, Advanced, Intermediate, and Beginning. Results of the search are returned in the form of links to the pages in the site that includes the keyword(s). If the user moves to one of the links and then returns to the Search page, his or her search results list is still available for review. All four modules of SimScience include the Search feature.

The Glossary provides brief definitions for words students may not understand. From the top of the Glossary page, the user can jump down to each letter of the alphabet and a list of words in the glossary that begin with that letter. When the user clicks on a word, a new smaller window opens up with the definition of the word and often a descriptive image. The Glossary page is accessible from the side menu and each word in the glossary is also linked directly from the text in which it appears.

The main page of the Site Index is accessible directly from the side menu on each page and provides an overview of the site as discussed in section 4.2 on Navigation.

The Help page is a simple, text-dominated page intended to give the user some clues about the navigation and features of the Cracking Dams module. First, it is suggested that the user choose a level either based on their grade level or experience with fracture and dams. Second, the page points out that the Cracking Dams logo will always link the user back to the main page of the module and the SimScience logo will always link the user back to the main page of SimScience. Next, the methods of navigation are reviewed: side menu, forward and back buttons, and Site Index. Then the page notes that external links are followed by (#) and that these links should not be followed if the user is viewing the site from the CD-ROM. It explains that a cee icon is placed with sections throughout the module that describe the things a Civil Engineer might do. It also notes that Glossary words are followed by (*) and the definition will open in a new, smaller window if the link is clicked. It shows the play button that links to Quicktime movies or animated GIFs. Finally, the Help page notes that the Scenarios and Simulation sections will be best understood if the sections on Dams, Cracks, and Case Histories are reviewed first.

No side menu is available on this page because the level the user intends to view is unknown. The user must use the browser back button to return to whatever page from which he or she came. The Help page is accessible from both the side menu and from the main page of the module. The Help page is the same for the Intermediate and Advanced levels; a separate Help page is provided for the Beginning level.

The Quiz links from the Simulation results page. It is intended to test the knowledge the user gained from the site and point him or her back to sections where they may have missed something. The Quiz consists of eight questions from throughout the module. The answers appear in a new window. Links are provided to the appropriate section with information on each question. Evaluation of the SimScience site by the STAR (Students That Are Ready) Academy in Bethlehem, PA found the quizzes to be very motivational. Students found some guidance and interest in seaching the module for answers to the quiz questions.

The Summary page directly follows the Quiz page; the forward arrow on the Simulation results page links to the Summary. This final page in the linear progression through the site concludes the module by recounting the sections and providing links back to the main areas of interest.

The WebQuests page provides a brief description of the WebQuest format and use and links to several WebQuests for the Cracking Dams module. The WebQuests provide a framework for use of the module in the classroom and are discussed in detail below.

The Hometown Cracks and Hometown Dams pages display images of cracks and dams from all over the world. It is intended that students send in photos of cracks or dams to be included in these sections. This will provide another personal connection to the site and its content.

The Dam News and Cracking the News sections report current news clips on dams and cracks, respectively. These sections help to show the impact that fracture and dams have on everyday life. There is a link to search for headlines on cracks or dams in the Yahoo news database.

Dam Entertainment lists movies and books that portray dams both positively and negatively. These forms of entertainment are opportunities for interested users to further their knowledge about dams and see the influence of dams on Hollywood and writers.

The general information pages include Authors, Acknowledgements, Goals, and References. The Authors page lists all of the people who have worked on the module and provides links to their webpages or email as available. The Acknowledgements page notes the National Science Foundation support that made this project possible. The Goals page describes the learning objectives of the module: to teach engineering skills, civil and environmental engineering topics, engineering simulation, and societal impacts of engineering. Finally, the References page lists the books, articles, and other web sites that provided information used in the site.

An electronic bulletin board has been set up for use with the Cracking Dams module; it is powered by Ultimate Bulletin Board™ (http://www.ultimatebb.com/). Electronic bulletin boards have the same main purpose as regular bulletin boards: to provide a place where users can post messages to communicate asynchronously with other users. Electronic bulletin boards have the added advantages of threads, user response, and numerous capabilities for maintenance. A thread is like a subject heading; all postings relevant to a certain subject are found under that particular thread. Users have the option to register when they use the bulletin board. If a user does register, other users can see the first user’s profile or respond directly to his or her email. Maintenance capabilities include deleting postings, banning certain words, and sending messages to registered users. Bulletin boards can provide a medium for communication outside the classroom. If a user is asked to post a message on the bulletin board, he or she must give that subject some though, reflection. Bulletin boards do require maintenance to ensure that unwanted postings are removed. The bulletin board is also intended to be a medium for teachers to communicate on their uses of the applet and the module. The bulletin board also scaffolds the student use of the site, available for comments on things to try with the applet, for example.

As the Beginning level is intended for K-4, the reading level must be kept as low as possible while maintaining communication through other methods. The level is short in length and dominated by images and roll-overs to facilitate understanding and interaction and keep the student’s attention. A narrating character (created by Andrew S. Polaha), called Dammy the Beaver, leads the user through the site. This was incorporated at the suggestion of several K-4 teachers. There is also a greater use of color in this level than in the other two levels. For example, the Cracking Dams logo for the Beginning level is rainbow colored whereas it is red for the Advanced level and blue for the Intermediate level.

The Dams section begins with something that is familiar to many children:

beavers. Dammy the Beaver is introduced as the narrator on the first page of the level. He appears on every page, in one position or another. The intro page also teaches the children several things that will help them use the site. After Dammy’s introduction, the user sees Dammy sitting in front of a computer using a mouse. The user is told that whenever he or she sees Dammy like this, he or she should move the mouse on to the colorful words nearby to change the picture. The user is asked to do a roll-over as an example. Next, the use sees Dammy holding a movie camera; this image indicates that there is a movie or an animation for the student to watch. The user is told to press the play button whenever he or she sees Dammy with the movie camera. There is a movie clip from Superman for the student to watch to show an example of a movie and provide an introduction to cracking in dams. Finally, Dammy appears again and ells the user to click on the forward arrow at the bottom of each page to continue. There is a label next to the forward arrow to help the student locate it.

On the next page, the building of dams by beavers is discussed and then built on to introduce "people dams." Roll-overs are use to describe the services dams provide as well as the problems dams cause. Dammy the Beaver guides the user to roll over each of the items in the lists of services or problems to see the associated image. The clip of the failure in Asteroid is presented to show the dramatic effects. The materials for dams are presented using images of the different types. Finally, three types of concrete dams are introduced: gravity, buttress, and arch. Dammy tells the user to try to trace the fundamental shapes associated with each type of dam on each picture of a dam: triangle for gravity and buttress and part of a circle for arch dams. Roll-overs produce the shape on the photo.

The cracks section begins with familiar images of cracks, again using roll-overs as guided by Dammy the Beaver. The notion that cracks are caused when a force is applied to an object is introduced. A simple experiment with paper allows the user to see Mode I fracture. Next, the concrete is described and a connection between fracture and dams is drawn. What the user learned in the simple experiment about fracture is applied to dams on the next page in the Cracks section.

The four case histories are shown in the Examples section. A brief amount of information about each dam is presented in terms of things the students might be more familiar with: reservoir size in terms of bathtubs of water, height of the dam in terms houses high. Each case history includes an animated GIF of a simple web-FRANC2D analysis of that dam.

Finally, the Simulation section is composed of animated GIFs of each step of an analysis: drawing the model, applying forces and boundary conditions, adding cracks, running the analysis, and viewing the results. This allows the young student to see the progression of an engineering simulation. Dammy the Beaver leads the student to watch each of the movies. There is a link to the simulation applet for those who may wish to try it.

The Beginning level also includes a Search, Glossary, Site Index, Help, quizzes, and worksheets. Search, Glossary, Site Index, and Help are all available from the side menu. The Help page is a simplified version of the Intermediate and Advanced levels’ Help page with additional comments about Dammy the Beaver, roll-overs, and watching movies. There are interactive quizzes following both the Dams and Cracks sections of four questions each. On the introduction page of the Beginning level, there is a link to a page "for the teacher." This page suggests using the Beginning level in three parts: first, Dams; second, Cracks; and third, Examples and Simulation. A worksheet is available for each of these three parts. The worksheets were found to scaffold use of the level well during evaluations. The breakdown of the level into three sections is suggested because this amount of information appeared to be appropriate for the students’ attention spans in the evaluations.

The goal of linear movement through the module using the forward buttons is to gain knowledge on cracking and dams and its societal impacts, including the tools to perform an engineering simulation of cracking in a dam. The WebQuest goes a step further in guiding the user through the site by providing a motivating Quest, explicit steps and links to follow to complete their tasks, and opportunities for collaboration, problem-solving, hands-on learning, case-based reasoning, reflection, and sharing. The student is further scaffolded by a worksheet to use with the WebQuest.

Several short-term WebQuests have been developed for both the Intermediate and Advanced levels. Because of the amount of reading required to use a WebQuest, one has not been written for the Beginning level. The WebQuests are intended to be basic lesson plans for using the Cracking Dams module in the classroom; teachers may use these WebQuests as guides to develop other WebQuests for the module on their own. The parts of the WebQuests are the Quest, the Tasks, the Roles, the Process, the Worksheet, and the Conclusion. The traditional Introduction and Sources sections are not included because they have been incorporated into the Quest and Process sections, respectively. This helps to limit the length of the WebQuest page and eliminate repeated information that the students skipped over in an evaluation of the WebQuests. The number of roles that are described in the WebQuest defines the size of the group to use each WebQuest. The WebQuests are written for groups of three or four.

The final revisions of the WebQuests written for the Advanced level and the Intermediate level are detailed here.

There are several WebQuests available for use with the Advanced level that are slight variations of each other. One of the WebQuests is detailed here; descriptions of the variations appear following the details.

The Quest serves to draw the user in, set the stage for the activity, and present a question that needs answering. For this WebQuest, the Quest is presented by the "government engineers" to the group: the Narrows Dam, a concrete gravity dam on the Little Missouri River, has two problems, it is cracking and it is causing the depletion of salmon in the river. The group must research the case and simulate the cracking in the dam to decide if the dam should be repaired or decommissioned. A real-world aura surrounds the government request for the group. From here the group embarks on the problem that must be solved, their Quest.

The Tasks describe what should be accomplished by the group. In this case, the group must first assign roles to each of the members. Other tasks are to follow the Process, fill in the Worksheet, and post statements to the electronic bulletin board on several occasions. The final task is to state their position on the dam’s repair or decommissioning and post it on the bulletin board. The author uses the Tasks section to explicitly state that groups should assign the roles and follow the Process step by step because students did not realize these points during an evaluation of the WebQuest.

The Roles describe the different "hats" that each member of the group should wear and the parts of the process that should be lead by the person in that role. The Roles of this WebQuest are all Civil Engineers who work for different organizations: the US Bureau of Reclamation Engineer, the US Army Corp Engineer, and the Association of Dam Safety Officials Engineer. Each of these organizations are prominent in the industry of dams are mentioned in the web site as so; thus the students feel that these roles are based on reality. All of the roles are engineers in an effort to emphasize the fact that engineers should be concerned with the environmental aspects, the technical simulation, and the societal impact of a dam failure. Another option might be to have a role of an environmentalist who was concerned with the environmental impacts of the dam, but this gives the impression that engineers are not concerned with the environment, which should not be the case. The US Bureau of Reclamation Engineer is to take the lead in gathering the tools for the simulation and performing the simulation. The US Army Corps Engineer is to take the lead on research of the services provided by the dam and the ecological impact of the dam. The Association of State Dam Safety Officials Engineer is to take the lead on reviewing the case histories to learn about remedies for cracking and estimating the loss of life if the dam fails. The roles are not meant to split up the work, merely to have one person take charge of each part of the process and of the collaboration of the group for that part.

The Process section presents detailed instructions on how an expert might try to solve the problem at hand. The Process includes opportunities for constructivist experiences, case-based reasoning, reflection, and sharing. An outline of the Process is described here. The level of detail and numbering of the steps of the Process is a direct result of an evaluation conducted with a group of high school students on this WebQuest. The Worksheet is integral to following the Process and should be filled out at each step of the Process; the amount of detail and instruction included on the Worksheet is a result of the same evaluation, which is discussed in the next chapter. One might wonder why the Process section is necessary if the instructions are included on the Worksheet. The answer to this is that the Process section, being on the web, provides hyperlinks to the appropriate parts of the module or external web sites, which the Worksheet cannot do, being on paper. At the beginning of each step on the worksheet, the students are reminded to return to the Process on the web.

First, the group must gather information about the Narrows Dam from the National Inventory of Dams database available online. This step provides valuable database searching experience. Next, the group is directed to the Dams section of the module to learn about the positive and negative impacts of dams. The group must consider the importance of the services the Narrows Dam provides juxtaposed to the decrease in salmon numbers the dam is causing. The group must answer questions on the Worksheet regarding these issues, promoting reflection and group collaboration.

Next, the group proceeds to the section of the module on gravity dams to learn the first three tools of performing a simulation of a cracked dam. The Worksheet scaffolds the student in obtaining the appropriate information from the module for this step. An earlier version of the Worksheet that did not provide this scaffold resulted in many students missing crucial parts of this step. Next the group is lead to the section on Cracks to learn the final two tools to perform a simulation, again with the Worksheet scaffolding them. The group is now ready to perform a simulation, but first reviews the steps of a simulation at the beginning of the Simulation section. They move on to the simulation applet to model the cracked dam they have, by now, sketched on their Worksheet. This hands-on opportunity allows the students to practice what they have learned from the module so far. They model two cracks, one on the upstream side and one on the downstream side; usually, only the crack on the upstream side grows noticeably. They are asked to post a message on the bulletin board about their simulation results and comment on the use of simulation in engineering, promoting both reflection and sharing with other groups.

Next, the group moves on to the Scenarios section to estimate the loss of life due to a failure of the Narrows Dam. They look up the population of the city nearest to the dam to use as the number of people at risk if the dam fails in the estimation algorithm; this makes the estimation more realistic. Also, the group tries the algorithm several times, varying different parameters, to see which ones affect the algorithm the most. The group must then consider and answer some questions about their trials. They should post a message on the bulletin board about other parameters they believe should be taken into account when one estimates the loss of life due to a dam failure.

Next the group reviews the Fontana Case History. They are told that the Narrows Dam suffers from an intense amount of solar radiation. By reviewing the Fontana Case History, they learn that the Fontana Dam also had the same problem, which was a cause of cracking. They also learn what was done to try to remedy the problem. This is a chance for the students to see the iterative design required to solve an engineering problem.

Finally the group is asked the consider what they have learned about the Narrows Dam: the services it provides, the problem it is causing with salmon, how the cracks in the dam might grow, the remedies for cracking in a similar case, and the estimated loss of life if the dam fails. Now they must decide if the dam is worth repairing or if it should be decommissioned based on these issues. The group should also list what other factors they would want to consider in their decision. They post their decision on the bulletin board for sharing with the other groups. It is intended that the groups read through each other’s decisions and then discuss the implications.

The Conclusion reiterates the lessons the group has learned from the WebQuest and suggests that the groups discuss their decisions.

The teacher’s section, on a web page separate from the actual WebQuest, describes the math and science skills used in the Quest and interdisciplinary nature of the activity. For example, students learn about the forces that act on a concrete gravity dam; they must calculate the magnitude and location of two of these forces and sketch them on a scaled drawing of the dam. This part of the Process uses skills of scaling the dam to draw it, calculating the magnitudes of forces and the centroid of the dam, and using the concept of a force body diagram. These details help the teacher provide a connection between the WebQuest and the classroom topics. The author suggests two 45-minute periods for the completion of this WebQuest, but it may be modified to make it longer or shorter.

There are several variations of this WebQuest; this WebQuest concentrates the learner on gravity dams. Another version of the WebQuest concentrates the learner on arch dams. The Sawpit, an arch dam in California, is the subject of the arch dam WebQuest instead of the gravity Narrows Dam. The Sawpit provides similar services and has similar ecological impacts as the Narrows Dams. The groups use the section on Arch Dams to learn about the tools for simulating an arch dam. The students are directed to the Case Histories of the El Atazar and Kolnbrein dams to learn about cracking and remedies in arch dams. The goal of the WebQuest on arch dams is the same, to weigh the impacts of the dam and decide on its fate. Both of these WebQuests provide roles for three people. A four-person version is also available for both the arch dam WebQuest and the gravity dam WebQuest. In the four-person version, the role of the Bureau Engineer is split into two roles; one of the roles is concerned with finding the first three tools about dams for simulation and the other is concerned with finding the last two tools about cracking for simulation. The two Bureau roles lead the performance of a simulation together.

There are also several WebQuests available for use with the Intermediate level that are, again, slight variations of each other. One of the WebQuests is here detailed; descriptions of the variations appear following the details.

For this WebQuest, the quest is to learn about a concrete gravity dam near the group’s town or in their county, providing an immediate connection to the group. They must research the services and problems of dams and simulate cracking in a gravity dam to help them consider if dam problems outweigh their services. To simplify the quest, the government story is not used in the Intermediate level. The group must solve the problems of simulating a crack in a dam and weighing the consequences of dams.

The tasks are to assign roles to the group members, follow the Process, fill in the Worksheet, and post statements to the electronic bulletin board on several occasions.

The Roles are the same as those for the Advanced WebQuest although the names are shortened: Bureau Engineer, Army Corp Engineer, and Safety Association Engineer. Again, all of the roles are Civil Engineers in an effort to emphasize the fact that engineers should be concerned with all aspects of impact of a dam. The Bureau Engineer leads the gathering of the tools for the simulation and the performing of the simulation. The Army Corps Engineer leads the research on the statistics on the group’s dam from both the National Inventory of Dams and from the loss of life algorithm. The Safety Association Engineer leads the research on the services and environmental impacts of dams.

The Process section again includes opportunities for constructivist experiences, reflection, and sharing. The level of detail of the Process is a direct result of an evaluation conducted with a small group of 7^th and 8^th grade students on this activity, as described in the next chapter. The worksheet should be filled out at each step; the amount of detail included on the worksheet is also a result of the same evaluation. The students are reminded on their worksheets to return to the Process on the web at the beginning of each step.

First, the group assigns roles. Then the group moves to the National Inventory of Dams database online to find a gravity dam to become the subject of their quest and simulation. It is suggested that the group look for a dam near their hometown to provide a personal connection to their investigation; it is referred to as "their" dam from then on to maintain the connection. This step also provides valuable database searching experience. Next, the group is directed to the Dams section of the module to learn about the positive and negative impacts of dams. The group must answer questions on the Worksheet regarding these issues, promoting reflection and collaboration within the group.

Next, the group proceeds to the section of the module on gravity dams to learn the first three tools of performing a simulation of a cracked dam. The Worksheet scaffolds the student in obtaining the appropriate information from the module for this step. Less calculation is required in this WebQuest than in the Advanced level WebQuest. Evaluation has shown that students can get bogged down doing calculations and lose their perspective in the overall simulation process. Next the group is lead to the section on Cracks to learn the final two tools to perform a simulation, again with the Worksheet scaffolding them. The group reviews the steps of a simulation at the beginning of the Simulation section. They move on to the simulation applet to model the dam sketched on their Worksheet. This hands-on opportunity again allows the students to practice what they have learned from the module so far. They are asked to post a message on the bulletin board about their simulation results: did the crack grow, in which direction did it grow, why?

Next, the group moves on to the Scenarios section to estimate the loss of life due to a failure of their dam. They look up the population of their city to use as the number of people at risk if the dam fails in the estimation algorithm; this makes the estimation very personal. The group tries the algorithm several times, varying different parameters, to see which ones affect the algorithm the most. The group must then consider and answer some questions about their trials. They should post a message on the bulletin board about other parameters they believe should be taken into account when one is trying to estimate the loss of life due to a dam failure.

Finally the group is asked the consider what they have learned about their dam and dams in general: the services dam provides, the problems dams cause, how a crack grows in a dam, and the impact if the dam fails. Now they must answer one of two questions and post their answer on the bulletin board for sharing with the other groups. The first question asks what they think about the use of computer simulation; the second question asks their opinion on a dam that provides drinking water but is killing fish. It is intended that the groups read through each other’s answers and then discuss the implications.

The Conclusion reiterates the lessons the group has learned from the WebQuest and again suggests discussion with the other groups.

The teacher’s section again describes the math and science skills used in the Quest and interdisciplinary nature of the activity. Concepts at this level include scaling, forces, and following the steps to do the simulation, among others. The author suggests one 45-minute period for the completion of this WebQuest, but it may be modified to make it longer or shorter. This WebQuest is kept to the length of one period to avoid carry-over to the next day. The exclusion of certain parts of the Process that are included in the Advanced level WebQuest are the result of this intention.

There again are several variations of this gravity dam WebQuest. Another version of the WebQuest concentrates the learner on arch dams. Both the arch dam version and the gravity dam version are available for groups of three or four by using one or two Bureau Engineers, as in the Advanced level versions.

The Cracking Dams module presents a great deal of information on dams and cracking with many opportunities for critical thinking and sharing of the experience the module provides. The Case Histories present opportunities for case-based reasoning. The Simulation and Scenarios create several hands-on opportunities. The electronic bulletin board promotes reflection and sharing for many of the experiences within the module. The WebQuests provide scaffolding for the student and the teacher to use the Cracking Dams module in the classroom. The Quest and Roles provide a certain personal motivation in a problem-solving situation. The Process promotes collaboration, case-based reasoning, reflection, sharing, and hands-on activities for the groups. The Worksheet scaffolds the student during the Process. The final version of the module, including its appearance, navigation options, content, and WebQuests as described above is the direct result of several trial-runs and evaluations of the module and WebQuest activity with students. The next chapter elaborates on these evaluations and their outcomes.