The railroad trestle bridge shown in the photo is supported by reinforced concrete bents...

The railroad trestle bridge shown in the photo is supported by reinforced concrete bents. Assume the two simply supported side girders, track bed, and two rails have a weight of 0.5k/ft and the load imposed by a train is 7.2 k/ft. Each girder is 20ft long. Apply the load over the entire bridge and determine the compressive force in the columns of each bent. For the analysis assume all joints are pin connected and neglect the weight of the bent. Are these realistic assumptions?