Constructional Design Method Of Reinforced Concrete Torsional Member Associated With Torsional Shear Deformation

The mechanical properties analysis of torsion members is a basic issue in the design of engineering structural members.Earthquake damages to torsion members are often severe and difficult to repair.The torsional deformation of the cube element is associated with the reverse shear deformation,and the reverse shear deformation is one of common macroscopic deformation forms in engineering.However,in China’s existing specifications,the content of resistance design related to macro effects of reverse shear has not been included.Supported by the National Natural Science Foundation project "51878621",this thesis intends to study the design method and full-scale test verification of the reverse shear problem in reinforced concrete torsional members.Conclusions are summarized as follows:1.Based on previous work on deformation decomposition of our research group,this thesis proves that when a rectangular cross-section member undergoes torsional deformation along the cross-sectional plane,the opposite sides of the member will produce reverse shear accompanying deformation.2.Combined with engineering practice,the reinforcement construction method is studied for the reverse shear effect of bending and torsion members.Inspired by the bending shear resistance,considering the macro-antisymmetric of reverse shear,X reinforcement components are used to resist reverse shear deformation.3.Four different X-rib structure layout schemes are designed.Since X bars also have shear resistance,on the premise of satisfying the shear verification review,the minimum spacing of stirrups is appropriately increased to alleviate the problem of increased steel consumption.4.Considering the prevention of distortion caused by the similarity ratio of the stirrup shear resistance and the X reinforcement shear resistance,the full-scale test method is utilized to conduct a comparative test between concrete bending and torsion members with X reinforcement schemes and that with traditional stirrup schemes.Test results show that,compared with the traditional stirrup scheme,the reasonably arranged X-rib scheme has a more uniform distribution of shear cracks and shear cracks develop more slowly.Especially for the small mesh X-ribbed reinforcement scheme,although the body reinforcement ratio has increased compared with the stirrup scheme,the bending-torsion load value corresponding to the first 0.2 mm structural crack has been significantly improved.It is indicated that X bar can effectively resist the reverse shear deformation of the beam side,and furthermore increase the ability to resist the torsional deformation of the cross section associated with the reverse shear deformation It is a recommended reinforcement scheme for bending and torsion members.