![]() In this case geometric non linear analysis has to be carried and an elastic catenary behaviour of the cable is considered. More detailed analysis may require cable elements be m odelled. The model is checked if the stiffness of the truss is sufficient to resist the initial Dead load. ![]() Usage in Cable Bridges For preliminary design of the cable bridges we go for modelling of cables as equivalent truss elements. suspension and cable-stayed bridges, where in large deformation effects can not be neglected. If you assumed the direction of all forces correctly up front, you are going to get all positive numbers. For the compression case, you call it a negative force, for the tension case, you call it a positive force, by convention. It’s effective in case of cable bridges i.e. If it points outward away from the joint or member, it is a tensile force. General Usage Used for both cable bridges as well as for modelling struts and ties of general bridges. Non linear behaviour, no superimposition When non linear behaviour of cable is considered, superimposition of load cases are ruled out and combined effect of loads has to be considered. Load Combinations Superimposition possible Linear combinations of load cases can be made to compare truss force results. Hence consideration of sag becomes important. Sag is predominant Cable elements are inherently non linear and the stiffness changes with the load applied. Main differences in these elements are as tabulated below: Feature Truss Element Cable Element Sag Effect No Sag Truss element, is linear in general and has constant stiffness. ![]() Truss element can resist both tension and compression, while a cable element can resist only tension. ![]()
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