Week 8

In the past week, we began working on designing and building our 36" span bridge.  We used the same basic design from the 24" span bridge but we expanded it so the span reached the 36" minimum.  We chose to work on our bridge in class instead of the truss analysis because we agreed that this was using our time more efficiently.  It would be easier to work on the truss analysis on our own at home and work together on the bridge in class.  The truss analysis was relatively simple to do on our own.  This week we are planning on focusing on slightly changing our bridge design in order to increase the load it is capable of supporting.  We will perform practice tests in class to prepare for the formal testing in week 9.  By performing practice tests and using the method of joints, we can see where the weak spots are and concentrate on making them stronger.  Our major accomplishment was getting a good start on our 36" span bridge and completing the method of joints in order to improve and analyze our design.  An issue that we encountered this week was using the bridge designer program, it does not allow any combination of nodes and members.  Our original design did not satisfy the specifications needed to successfully perform the calculation.  We had to slightly simplify our design in order to get results.

After becoming familiar with the Method of Joints for truss analysis, I do not thing this type of analysis is sufficient for a real bridge.  This method of analysis only takes into account the horizontal and vertical forces.  There are many other forces acting on bridges in the real world.  This method also only applies the load on the bridge to one spot on the bridge, this does not compare to loads on real bridges.  The loads are constantly changing position because traffic is constantly changing position and the load changes.  The bridge designer and the method of joints also does not account for the weight of the bridge itself.  This would be an important factor in the real world.  I would like to analyze the forces acting on the bridge in other directions other than horizontal and vertical.  In the real world, there is forces from wind and torsional forces that also exert forces on the bridge.  The method similar to the method of joints could be used but in a third dimension.  The force from the wind is going to be hard to predict because it is always different but we could use a rough overestimation to ensure the bridge will be able to withstand the maximum force applied to it.