Design Report

1. A written report is required for each K'NEX structure submitted for evaluation. The content and quality of the report will account for 70% of the project score. The remaining 30% of the project grade will be determined by the strength of the structure based on the ultimate strength-to-weight ratio (SWR). There are two strength criteria for structures: 1) all structures supporting the design loads (15% all-or-nothing); and 2) the structure with the highest SWR is awarded full points (15%) and the remaining structures will be awarded scores commiserate with their performance (first place will be awarded 15 points, second place 14 points, third place 13 points, etc. . .). If a structure does not meet the construction rules, listed below, the submitting student will receive no strength points.

2. The design report should include, but not limited to the following:

1. Title page - name, date and course information

2. Introduction - design and report requirements

3. Structural Design - a complete set of plans for the structure

4. Structure Analysis - a complete design and analysis of the structure including the force in each member for the applied load. Assume the modulus of elasticity of the K'NEX plastic is E = 377 ksi. Figure 1 show the typical cross-section of a K'NEX rod. The cross-sectional properties for this section are: I = 8.8 x 10^-5 in⁴ and A = 0.031 in². Also, include a prediction of the ultimate load of your structure. Show evidence that you refined and optimized your structure during the design process.

 

Figure 1. Typical K'NEX Rod Cross-Sectional Area

5. Summary - summarize the strengths and weaknesses of your design and give a prediction for the ultimate load and SWR.

3. Your report should be printed on a laser quality printer. If possible, all structural sketches should be produced using graphical software.

4. A progress report should contain a preliminary structural design. Although the progress report should contain all the components of the final report, the objective is to help students refine their designs. Students are encouraged to turn in the progress report before the deadline so they can begin the final design analysis for the final report.

Construction Rules

1. Structures must be constructed using only K'NEX pieces.

2. Glue is not allowed in construction of the structure.

3. K'NEX members cannot be coated or treated in any way.

4. The structure must be designed to fit on the support shown in Figure 1.

Figure 1. Structure loading scenario and dimensions

5. Members may not brace off the any part of 14-inch bottom support, expect for the top of the abutments.

6. The structure must not be taller than 18 inches. A 4-inch by 4-inch loading block will be placed on top of the structure at mid-point.

7. All structures will be loaded to the design load of 75 lb or to the point of failure which occurs first. Failure is defined as the point when the structure can no longer support an increased load or collapse.

8. Each student may submit only one structure.

9. Structural performance will be measured by a strength-to-weight ratio computed in the following manner:

         

where SWR is the strength-to-weight ratio, P is the ultimate load (lb), and W_structure is the weight of
the structure (lb).

10. The cost of each structure will be estimated using the following cost sheet. A cost factor will be computed as follows:

             
     

11. An adjusted SWR computed as follows:
    
             
     

12. The structure with the highest SWR ratio will win the event.

13. Any modifications or repairs to the structure must be done before registration. Once the structure is registered, no other changes may be made.

Schedule

This web site was originally developed by Charles Camp for CIVL 3121. This site is maintained by the Department of Civil Engineering at the University of Memphis. Your comments and questions are welcomed.