bridge design
I'm lookin' for input from people who have no idea what I'm talking about here to tell me if things are unclear. As part of my engineering service, I chose to rewrite a design problem, since so many people in my class (ALL of us...) took this in different ways. I'd appreciate any input.
The bridge you will be designing. is to span the distance between two piers. It is required that a truss be used. This truss will be constructed using steel members that are pin connected. The end supports are required to be a pin and a roller. A vertical loading of 5 kN will be acting downward on the top of the bridge, that is, applied at the level of the roadway acting down. This load will be applied to joints only. It can be distributed among several joints over the middle three meters of the bridge. Pick how this load will be distributed on your truss. The top of the bridge must be level with the roadway, with the truss underneath. The piers A and B may be set at any desired height. The forces from wind and weight of members are to be neglected.
The maximum tensile force in each member cannot exceed 4.25 kN, and the maximum compressive force cannot exceed 3.5 kN. These forces are regardless of the length of the member. Design an economical truss that will support the 5 kN loading. Members cost $16 per meter, and the pin connections cost $4 each. When calculating the cost of the members, a member’s length will be defined as the distance between joint centers. As an engineer, your time is valuable. It may not be cost effective to spend a lot of time maximizing these forces.
In addition to designing the truss, you are to build it. I recommend using a scale of 4”=1m. This will result in a truss that is 4 feet long. The cost of the bridge will be calculated using the full-scale bridge design, not the scale model. You are to build just one truss - not the entire bridge. You may make it out of wood, metal, plastic, PVC pipe or any other rigid material. For instance, you could use “rough lathe” for the members, which is quite inexpensive and can be purchased at any lumberyard. When actually building your bridge, you may bolt the members together, use gusset plates or pin connections, at the joints. It may be easier to use gusset plates when building your truss, but using pin connections may be beneficial to see if your truss is rigid.
Keep in mind that this is a statics class, not deformable body mechanics or anything like that. It's an introductory design problem. Things do not have stress or rotate or anything like that. Thanks!
The bridge you will be designing. is to span the distance between two piers. It is required that a truss be used. This truss will be constructed using steel members that are pin connected. The end supports are required to be a pin and a roller. A vertical loading of 5 kN will be acting downward on the top of the bridge, that is, applied at the level of the roadway acting down. This load will be applied to joints only. It can be distributed among several joints over the middle three meters of the bridge. Pick how this load will be distributed on your truss. The top of the bridge must be level with the roadway, with the truss underneath. The piers A and B may be set at any desired height. The forces from wind and weight of members are to be neglected.
The maximum tensile force in each member cannot exceed 4.25 kN, and the maximum compressive force cannot exceed 3.5 kN. These forces are regardless of the length of the member. Design an economical truss that will support the 5 kN loading. Members cost $16 per meter, and the pin connections cost $4 each. When calculating the cost of the members, a member’s length will be defined as the distance between joint centers. As an engineer, your time is valuable. It may not be cost effective to spend a lot of time maximizing these forces.
In addition to designing the truss, you are to build it. I recommend using a scale of 4”=1m. This will result in a truss that is 4 feet long. The cost of the bridge will be calculated using the full-scale bridge design, not the scale model. You are to build just one truss - not the entire bridge. You may make it out of wood, metal, plastic, PVC pipe or any other rigid material. For instance, you could use “rough lathe” for the members, which is quite inexpensive and can be purchased at any lumberyard. When actually building your bridge, you may bolt the members together, use gusset plates or pin connections, at the joints. It may be easier to use gusset plates when building your truss, but using pin connections may be beneficial to see if your truss is rigid.
Keep in mind that this is a statics class, not deformable body mechanics or anything like that. It's an introductory design problem. Things do not have stress or rotate or anything like that. Thanks!