Simulation About Compatibility Torsion Of Spandrel Beams In A Cast-in-place Reinforced Concrete Beam-slab System

In reinforced concrete floor system of spandrel beams and floor beams, the spandrel beam is subjected to the compatibility torsion arises from the member twisting to maintain compatibility of deformations; the compatibility torsional moment depends on the ratio of the linear torsional stiffness of the spandrel beam and the linear flexural stiffness of the floor beam, and the anti-torsion action caused by the rigid-plane effect in the monolithic slab. Because of the nonlinear material character of concrete and the drop in torsional and flexural stiffness after cracking, the torsional moment in the spandrel beam is difficult to calculate accurately. Until now, there is no specific provision for compatibility torsion in the Concrete Structure Design Code of China (GB50010-2002).In this paper, the research was developed around two cast-in-place no slab floor system and 16 simulations girder systems,and the following are the relevant research results:①Element size of 100mm was adopted during the analysis for save time still without reducing the precision.②Nonlinear finite element program especially for three-dimensional frame was used to analyses such structure system, load-torsion angle curves of unit element obtained by analysis and experiment were compared carefully.It is clear that,after crack the torsional rigidity can be calculated by multiplying the pre-crack torsional rigidity by 0.2 for simplification.③For the cast-in-place no slab floor system, simplified coordinated torque calculation method was put forward to adapt to actual requirement. In which, internal forces can be calculated based on structure mechanics.At ultimate limit state,as for the torsional rigidity of side beams, which can be taken as 60% of that calculated by means of Saint Venant principle or 40% of the torsional rigidity by sand heap analogy method.At serviceability limit states,the torsional rigidity of side beams,which can be taken as 80% of that calculated by means of Saint Venant principle or 50% of the torsional rigidity by sand heap analogy method.④16 no slab floor beam system designed by SATWE were first calculated by simplified method,then checked using non-linear finite element program.Based on the ACI code,SATWE and simplified method to find out reasonable simplified method for calculation of torque of side beams of the cast-in-place no slab floor system. ⑤It was found that the calculated torque according to ACI318-08 was deflected from the actual one, even insecurity sometimes because of its failing in considering of the influence factors on compatibility torsion.