Trusses: An Angle on Stress During Earthquake


                                  the picture is taken to show the deformation

Objectives/Goals

 The intent of this project is to examine whether different angles change the strength of a truss during an earthquake. The hypothesis is that trusses formed of 60º angles will last the longest during a simulated earthquake. 

Methods/Materials 

The materials used in this project are as follows; an earthquake simulator and enough wood to build 60 trusses(I used 3mm by 3mm wood.) You will also need super-glue, corkboard and wax paper for making the trusses. Pins are very helpful for holding the joints together while the glue dries. A stopwatch/timer is also needed to time how long a truss lasts. A table saw capable of cutting at various angles is also needed. The testing procedure begins, after manufacturing the actual trusses, with placing a truss on the P-wave simulator. The simulator is then activated. Once the simulator is activated, a timer is set. Once the truss breaks, the timer is stopped and the time recorded. This process is repeated with half of all trusses, 10 of each type. Once all P-wave testing is finished, S-wave begins. The second half of the trusses are used, and the procedure is the same as for the P-wave testing. 

Results 

The results of this experiment are that the 30º trusses perform the best under S-wave testing, but the worst under P-wave testing. The 45º trusses perform the best under P-wave testing but the worst under S-wave testing. The 60º trusses, however, perform better overall. They are slightly lower than the 30ºs in the S-wave testing, and slightly below the 45ºs in the P-wave testing. Since an earthquake consists of both Pand S-waves, withstanding both is crucial. 

Conclusions/Discussion 

The findings show that while the 60º trusses are not the best at either type of wave, they are the best for the entire earthquake, which consists of both waves. This proves the hypothesis that an equilateral truss, or 60º truss, will perform the best during a simulated earthquake. This means that trusses(either in roofs or bridges)built-in earthquake-prone areas should be made from 60-degree angles. 

David M. Mikulka

Original Text link: http://csef.usc.edu/History/2003/Projects/J1818.pdf


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