Test And Analysis Of Compatibility Torsion Of Spandrel Beams In The Floor System Without Cast-in-place Slab Strengthened With External Prestressing CFRP Sheets

At present,the study on the compatibility torsion of spandrel beam is still not sufficient, and there is still no specific provision for this in the Concrete Structure Design Code of China.Two test of compatibility torsion in large scale specimens of floor systerm without monolithic slab have been done in our university and a series important results are obtained but not sufficient.Besides, the external presstressed CFRP strengthen techniques base on the WSG system still need further test and research,because of the lack of quantity and species of specimens,and the original specimen of WangHaiYang reinforcement provides a good platform for WSG of reinforcement effect of actual inspection.Therefore, the original specimen is strengthened by the external presstressed CFRP strengthen techniques base on the WSG system,and experimental study of compatibility torsion of spandrel beams in the floor system without cast-in-place slab was carried out .The following conclusion can be drive from these tests and analysis:①When the CFRP sheets are laterally pulled with optimized WSG clamp in the test,the axial force of the screw bolts increase linearly with the pulling force of CFRP sheet,which can be used to control the pulling force of the CFRP sheet in existing strengthening methods to achieve quantitative control.②In the case of concrete beam severely damaged,WSG clamp and CFRP sheets did not slip at the end WSG,and concrete destruction of local compression has not occurred at the end of anchor, it shows that WSG clamp has its unique advantage on the anchorage presstressed CFRP sheet.③Using the external presstressed CFRP strengthen techniques base on the WSG system strengthening concrete beam,the crack resistance,bearing capacity,rigidity and deformation capacity of severely damaged concrete beams can be enhanced, which fully demonstrates the effectiveness of the reinforcement technique and it can provides experimental and theoretical basis for the application of engineering strengthening.④In conventional concrete floor system with monolithic slab, the spandrel beam is always subjected to torsion-bending-shear; the compatibility torsional moment in the spandrel beam can NOT be neglected.⑤In the once experimental research of cracked spandrel beam,spandrel beams'torque increase with the load all along the test.The elastic method, the zero torsional moment design method or the ACI limit design method have a bit different from the actual situation,and the reduced elastic torsional stiffness design method can be used in the conventional floor system specimens with monolithic slab.⑥Base on three-dimenal finite element analysis program SAP2000,a linear analysis of the test model is carried out.With the comparison of experimental and analysis'the 2nd secondary beams'deflection - load curves and spandrel beams'load- angle of twist per unit length curves for the specimen, it can be drawn that the spandrel beam's torsional stiffness after cracking is proposed to be 15 percents to 20 percents of the elastic value.