Compatibility Torsion Study Of Reinforced Concrete Spandrel Beam

Spandrel beam appears compatibility torsion because of compatibility deformation in reinforced concrete frame, its elastic torque lies on the ratio of spandrel beam torsional stiffness and floor beam bending stiffness. After concrete beam cracks, spandrel beam plastic torque is hard to be calculated because of the nonlinear character of reinforced concrete structure and the difference of degraded ratio of torsional stiffness and bending stiffness. In order to direct practice engineering our nation concrete code for structure design specified that the torque of restricted spandrel beam should be considered its inner force redistributed. The code points out that the maximal adjustment coefficient of elastic compatibility torsion moment is 0.4.But it always overreinforced according to the design method in practice engineering.In order to settle this question, pure torsion and compatibility torsion emulate test of reinforced concrete beam have been done with nonlinear finite element code(concrete mode) based on the analysis of model test. The research indicates that the crack width of concrete beam is related to its twist angle, the crack width can be controlled by limit the twist angle of the concrete beam, so the design key of compatibility torsion of reinforced concrete is to control the twist angle. The twist angle of spar boom under working load is independent of design method. There is tiny difference between kinds of design method on torsion crack control. Compatibility torsion crack width of the spar boom should be controlled by limiting its twist angle under working load and constitution measure.The linear relation of twist angle and the maximal crack width is found base on the analysis of model test and emulation analysis, the maximal crack width is related to ratio of torsion reinforcement, statistic formula is given. The twist angle controlling value of reinforced concrete beam is discussed under regular service state. The twist angle of spar boom under regular service state is related to the designing load of the compatibility torsion specimen, grade of concrete intensity, the span length rate of spar boom and junior beam and the sectional dimension, the twist angle of spar boom is independent of concrete strength gradation. The statistic formula of unit length twist angle of spar boom under regular service state is provided.The effctiveness of bending resistance reinforce is better than torsion resistance reinforce. Torsion resistance reinforcement should be used as little as possible on satisfy deformation, crack width, ductility requirements. Better economical effectiveness can be gained when torsion resistance reinforcement is used adequately.The calculation formula of unit length twist angle of spar boom under regular service state, the twist angle control value, the design and analysis method of compatibility torsion beam and corresponding constitution measure are provided.