Time dependent deformations due to creep and shrinkage modify the response of structuressensitive to small geometrical changes such as the hyperbolic-parabola. In this investigation,a general finite element program is extended to consider time dependent andtime independent characteristics of concrete in shell-beam structures. Cracking, concretecompressive nonlinearity, steel nonlinearity, and concrete-steel interaction areconsidered in the time independent model, while aging, creep and shrinkage are includedin the time dependent one.With the model implemented, a series of studies are developed considering the structuraleffect of several parameters on the time dependent response of gabled roofs. Among theparameters considered, the manner of constraint in the support, and the size and positionof the crown beams are important. A decrease of 25% to 50% in the load carryingcapacity level has been observed considering time dependent effects, displacements areincreased four to eight times from the time independent ones, and large stress redistributionshave been found to occur with a shift in the load carrying mechanisms frommembrane to flexural. Design considerations emerging from the numerical results arehighlighted in an effort of improve our design criteria basis for this kind of structures.
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