Test And Analysis Of Compatibility Torsion Of Spandrel Beams In The Floor System With Cast-in-Place Slab

In reinforced concrete floor system of spandrel beams and floor beams, the compatibility torsion arises due to the restriction of the spandrel beams on the floor beams and the value 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 on the spandrel beams caused by the monolithic slab. The value of the compatibility torsion is difficult to calculate exactly due to the non-linear behavior of the concrete and the variation of the post-cracking flexural and torsional stiffness. There is no given method to calculate the problem like the compatibility torsion of the spandrel beams in the code GB50010-2010 to date.Based on the experimental analysis of 4 long-span P.C. beams floor system specimens and 2 reinforced concrete floor system specimens without monolithic slab forcing on the compatibility torsion finished in Chongqing university, one experiment researching on compatibility torsion which adopted the reinfoced concrete floor system specimen with monolithic slab was conducted. The main conclusions obtained via non-linear finite element analysis are listed as follow:①In the system of the reinforced concrete floor with monolithic slab, the spandrel beams are always subjected to the flexural moment and the shear force and the compatibility torsion cannot be neglected.②After the cracking of the spandrel beams, the compatibility torsion increases with the growth of the force. It is quite different from the fundamental assumption in the American code ACI318-08 that the designed value of compatibility torsion stays the same. Meanwhile, the constant value suggested by the ACI318-08 is relatively low and this would make the design of the spandrel beams unsafe.③Before the cracking of the spandrel beams, the torsion angle of the spandrel beams is minor due to the anti-torsion from the monolithic slab. However, after the cracking, the effect of the anti-torsion gets weaker with the development of the cracks and it could be ignored in the limite status.④There is some disadvantages in"the elastic method","the zero torsional moment design method"or"the ACI limit design method". It is suggested to use the torsional stiffness reduction method to solve the spandrel beams compatibility torsion problem of the reinforced concrete floor system with the monolithic slab which is studied in this paper.⑤Modeling and analyzing the specimens with the non-linear finite element program for the space line structures and comparing the experiment observation and the calculated results of the"unit length torsion angle of the spandrel beams - loading"relationship curve, it is suggested that value of the torsional stiffness could be set as 0.2 to 0.3 of the pre-cracking value...