CAD-2012-WPBD-Boyson

= **CAD - Design a Truss Bridge Unit** =

//2nd Semester 2012//
__ **Part I** __

Answer the following questions:

1. What are the 7 steps in the problem-solving process? 1. Identify the problem. 2. Define the problem. 3. Identify possible solutions. 4. Analyze and compare alternative solutions 5. Select the best alternative. 6. Implement the solution. 7. Evaluate the results 2. What is engineering design? What is involved besides math, science and technology? It is a specialized form of problem-solving -- the application of math and science to create something that meets a human need. Other than math and science, it is a creative process -- one requiring the ability to conceive of the problem solutions that no one has previously imagined. Theodore von Karman, an eminent scientist and engineer, said, "The scientist describes what it is; the engineer creates what never was." 3. What are the three major stages of the engineering design process. Project planning stage, design stage, construction and operation stage. 4. Name the three components of each stage in the engineering design process. Project planning stage: Needs analysis. Development of conceptual alternative. Selection of the preferred alternative. Design stage: Preliminary subsystem selection. Detailed subsystem analysis. Detailed subsystem design. Construction and operation stage: procurement. Construction. Operation and maintenance. 5. What type of engineers were included on Anne's Design team? Give a brief description of each engineer's job. Her team includes structural, transportation, geotechnical, hydraulic, and environmental engineers. Unable to find second answer. 6. What did the Design team do during Phase 2 of the project? Develop conceptual alternatives. They develop a range of distinctly different alternative bridge types and configurations. These alternatives are analyzed and compared, with the ultimate objective of selecting the bridge type that is best suited to the needs of the owner and the characteristics of the site. 7. Name the most economical bridge for each span: a. under 1000 ft - beam and truss bridges b. 1500-3000 ft - cable-stayed bridges c. over 2000 ft - suspension bridges d. 1000-2000 ft - arch and cantilever truss bridges 8. How much detail is developed during the conceptual phase? Conceptual alternatives are only developed in enough detail to ensure that the completed structure will meet the owner's needs and to perform a reasonably accurate cost estimate. 9. What is the purpose of a type study? The type study describes the alternative bridge configurations that were considered by the designers. It explains the advantages and disadvantages of each and provides the design professional's recommended alternative. this recommendation is based on thorough consideration of many criteria. 10. What is an iteration? What happens with each new iteration? An iteration is a repetition of the analysis-design cycle. With each new iteration, the cycle between analysis and design changes. 11. What is the purpose of a foundation? How does the geotechnical engineer choose the type of footing used? The purpose of a foundation is to distribute the weight of a structure, and all the loads acting on it, to the soil on which the structure rests. The footing used depends mostly on the quality of the soil. If there is firm soil or rock close to the surface, the geotechnical engineer will choose a spread footing -- a flat slab of concrete placed directly on the firm soil or rock. If the soil near the surface is soft, the bridge will need to be supported on pile, which are long steel or concrete shafts that are driven down through the soft soil layers and into firm soil or rock below. 12. Name the components of a complete draft of the design. Drawings, reports, and draft specifications are all components of a complete draft of the design. 13. Describe the steps in the design-bid-build project delivery process. The owner advertises the project through public notices and ads in industry publications. Construction contractors obtain copies of the plans, specifications, and other bidding documents from the owner. Construction contractors prepare and submit their bids. On a designated day, the owner conducts a bid opening. Bids are opened and read aloud. each bid is checked to ensure that it includes all required information and that the bid amount is not unreasonably low. The owner awards the construction contract to the lowest responsive, responsible bidder. This contractor becomes the constructor for the project. 14. How often are bridges inspected and what do the technicians look for during these inspections? Bridges are inspected every two or three years, looking for signs of deterioration and identifying needed repairs. Maintenance crews regularly clean the storm drains and expansion joints, repaint weathered steel, and repair cracked asphalt. 15. How do CAD programs enhance the design of bridges? Easier to create 2D and 3D drawings of the bridge. Easier updating. More accurately visualization of a completed structure. Highly accurate structural models. Determine internal forces, then automatically select steel or concrete members strong enough to carry these forces. CAD also makes it easier to share designs between other engineers. 16. Have CAD programs made engineers obsolete? Why or why not? Engineers have not become obsolete because of CAD programs. CAD software is only a tool. Like any tool, it can improve human efficiency, but it can never substitute for human creativity and good judgement. And like any tool, CAD can be misused. Some aspects of structural modeling and design simply cannot be automated. They require in-depth understanding of engineering principles, an appreciation for constructability, and good old-fashioned common sense. 17. What is the most important feature of the West Point Bridge Designer (WPBD)? The most important feature of the WPBD is the simulated load test. Once you have created a complete, stable, structural model, you can run the load test with the click of a single button. 18. Describe what happens within the program when the load test is initiated. The load test creates supports at the appropriate locations in your structural model. Calculates the weight of all the members, and applies forces to the structure as loads. Calculates weight of concrete bridge deck, asphalt road surface, and floor beams, then apply the corresponding loads to the structure. Applies standard truck loading to the structure at multiple positions, representing the movement of the truck across the bridge. Checks the structural model for stability. Performs a structural analysis, considering the combined effects of the bridge self-weight and truck loading. For each truck position, it calculates the displacement of each join and the member force for each member in the structural model. For each member, it compares the calculated member forces for all truck positions, and determines the absolute maximum tension force and the absolute maximum compression force. Calculates the tensile strength and compressive strength of each member. For each member, it compares the absolute maximum tension force with the tensile strength and compares the absolute maximum compression force with the compressive strength. If the force exceeds the strength, the member is unsafe. Displays the load test animation. 19. When you use the WPBD to design a truss, what phase of the nine-phase engineering process are you doing? Development of conceptual alternative. 20. How do the load test results help you with the bridge design? It saves time from building a model and testing weight on the model. It is also more accurate, giving you more information on how to strengthen your bridge.