Research On The Effect Of Cast-in-Situ Slab On "Strong Column-Weak Beam" Mechanism Of Reinforced Concrete Frame Structure

In the reinforced concrete frame structure,the cast-in-place slab and the adjacent frame beam are strong,forming a cooperative force mechanism.The cast-in-place slab has greatly influenced the force and deformation performance of adjacent beams,and the yield mechanism of "strong column and weak beam" is difficult to realize.At present,the study of this subject is based on the influence of the cast-in-place slab on the beam load distribution of the beam-column joints,or through the finite element software to establish a large-scale structural model to analyze the effect of the cast-in-place slab on the structural yield mechanism.The mechanism of the cast-in-place slab itself and the interaction between the cast-in-place slab and the beam and column on the structural performance of the lack of research,it is difficult to study the actual work of the cast-in-place slab on the adjacent beam.Based on the advantages of the above two methods,this paper uses the ABAQUS software to model the reinforced concrete frame structure for accurately analyzing the working mechanism of the cast-in-place slab and the influence of the cast-in-place slab on the frame beam and overall performance of the structure.Based on a large number of related literatures,ABAQUS finite element software is used to build the RC frame structure model with cast-in-place slab,empty frame and empty frame with additional cast-in-place slab quality.The influence of cast-in-place floor on the yield mechanism of RC frame structure "strong column and weak beam" is studied from several angles by means of modal analysis and lateral static loading.The main work and achievements are as follows:(1)By means of modal analysis and lateral static loading,the finite element software ABAQUS is used to calculate and analyze the natural frequency and capacity curve of different models.The influence of cast-in-place slab on the lateral stiffness of the structure is studied and the structure The lateral stiffness increase coefficient is used to evaluate the reinforcement effect of the cast-in-place slab on the structural rigidity.Finally,the empirical formula of the lateral stiffness increase coefficient and the plate thickness and the beam height is given by regression analysis.The results show that the effect of the cast-in-place slab on the lateral stiffness of the RC frame structure increases with the increase of the plate thickness,and decreases with the increase of the beam height.(2)By analyzing the damage of the frame model with the cast-in-place slab and the empty frame model and comparing the concrete tensile damage,concrete compression damage and the steel yield of the beam end,the results show that the influence of cast-in-place slab on the yield mechanism of RC frame structure is significant,which is not conducive to the realization of yield mechanism of "strong column and weak beam".Besides,the stress distribution of the steel bar is analyzed.At the same time,the influence of different node types,plate type and vertex displacement is analyzed synthetically.(3)By analyzing the stress distribution of the plate bar under different plate thickness and beam height,the variation law of the stress distribution of the plate with thickness and beam height is given.And further uses the effective flange width to measure the strengthening effect of the cast-in-place slab on the bending capacity of the frame beam.The results show that the effective flange width increases with the increase of the plate thickness,and the change with the beam height increase is different at different types of nodes,On this basis,the linear fitting empirical formula of the effective flange width of different types of joints with beam height and plate thickness is given.