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STATICS - CASE STUDY

    Introduction


Car Driving over Bridge


Dimension Diagram

 

At the local highway department, the bridge designer is required to calculate the force in the top horizontal member of a new bridge truss. The member force is need to help determine the correct type of material and the size of the member.

What is known:

  • The car mass is 1,500 kg.
  • The car is located at joint 2.
  • The bridge length is 16 m (4 bays).
  • The bridge height is 4 m.
  • Joint 1 is a pin support, and joint 5 is a
    roller support.
   
  Question

 

When the car is over joint 2, what is the force in member 6-7?

     
    Approach

 
  • First, solve for the support reactions.
  • Next, section off part of the truss and apply the three equilibrium equations:

        ΣFx = 0

        ΣFy = 0

        ΣM = 0
     
   
 
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