Experimental Study And Analytical Model Of Deep Beams Of Lightweight Aggregate Concrete With Openings

Deep beams are widely used in bridge structures of high-rise buildings.In order to reduce the size of cross-section members and reduce the seismic load effect,lightweight aggregate concrete(LWAC)is often used for pouring.However,in order to increase the use space of building structure in practical engineering,it is necessary to opening in the web of deep beams,which leads to the geometric discontinuity and non-linear stress distribution,resulting in complex load transfer mechanism.Through experimental research and theoretical analysis,this paper reveals the shear failure mechanism of LWAC deep beams with openings,defines the stress transfer path,and puts forward the shear analysis model of LWAC deep beams with web openings.1.The shear performance tests of nine LWAC deep beams with opening height of1000 mm were completed.The crack distribution and development trend of the specimens during loading were observed.The influence of opening size,opening position,reinforcement arrangement around the opening and shear span ratio on the shear performance of the specimens was analyzed.The results show that the failure mode of each specimen has nothing to do with the change of opening parameters,and the whole specimen fails because of the shear failure of the upper and lower limbs of the opening;2.The theoretical analysis model is established,in which the upper and lower limbs of the specimen are equivalent to the eccentric specimens,and compared with the shear calculation model of typical deep beams with openings.The calculation results show that the mechanical model of typical calculation method is not clear enough,and the influence factors of bearing capacity are not comprehensive,and the calculation results of the proposed analysis model are close to the test values.3.The main stress transfer path in the specimen is defined,and the corresponding strut and tie model is established,and the calculation is completed by CAST software.The results show that: the tension compression bar model can clearly represent the internal stress transfer path of the specimen,the proposed algorithm can fully consider the influence of various parameters on the bearing capacity of the specimen,and the calculation results are more accurate and stable.4.Based on ABAQUS software,the finite element analysis of the deep beams of the LWAC is realized by introducing the damage plasticity model of LWAC.The results show that the load deflection curve obtained by the finite element model is in good agreement with the test results.The introduction of damage plasticity model can reasonably describe the internal stress distribution of concrete and specimen shear failure characteristics.5.The damage plastic model of LWAC is introduced,and the analysis of the shear parameters of the bent members is completed by ABAQUS finite element analysis software.The results show that the numerical model can reasonably describe the distribution law of stress and the shear failure characteristics of the concrete.Based on the above,a design method of the deep beam of the LWAC with opening based on the pull-compression bar model is proposed.The research results of this paper are of great practical value and theoretical significance to guide the design method of deep beams,to improve the shear theory of concrete structure and to promote the engineering application of LWAC.