| The steel-concrete structure has the characteristics of high strength and excellent toughness,and is therefore widely used in high-rise and large-span structures.For steel-concrete frames,the seismic performance of beam-column joints plays an important role in the overall structural safety.Currently,domestic and foreign scholars have made certain achievements in the research on steel-concrete planar right-angle nodes,but there is still insufficient research on steel-concrete oblique beam-column nodes.In this paper,taking a hospital in Fuyang as the background and using numerical simulation methods,the load-bearing performance and shear carrying capacity of steel-concrete oblique beam-column nodes were studied in depth.The following are the main achievements and contents of this study:(1)Summary of the research on steel-concrete composite nodes by domestic and foreign scholars,the ABAQUS finite element software was used to model and analyze the existing steel-concrete composite beam-column nodes.Based on this,the hysteresis curves of numerical simulation and experiments were compared and analyzed,and the results showed a good agreement between the two curves,which verified the accuracy and reliability of the numerical simulation method.(2)By adopting the finite element modeling method,a series of models were established with a step of 6°,including six boundary nodes and six central nodes with inclined beam offset angles from 0° to 30°.Through the establishment of finite element models,the failure mode,load-bearing characteristics,and seismic performance of the steel-concrete composite inclined beam-column under different offset angles were studied.(3)The failure modes and load-carrying characteristics of the edge and middle nodes of the inclined steel-concrete beams were studied under monotonic loads.Both types of nodes failed by plastic hinges formed at the beam end,but with an increase in the offset angle,the maximum equivalent plastic strain region of the nodes shifted from the uniformly distributed section below the beam section to the beam offset side.The peak and failure loads of both types of nodes increased with increasing offset angle,and the higher the offset angle,the stronger the load-carrying capacity.Nodes with offset angles have differences in the development path of concrete and steel compared to those with 0° offset angle,but the effect of offset angle on the maximum stress values of concrete and steel is limited.(4)The study investigated the mechanical behavior of the two types of nodes under cyclic loading.From the steel stress of the steel-concrete composite inclined beam-column,the maximum stress value of the steel in both types of nodes is at the flange and web of the built-in steel beam end.The maximum stress values of the built-in steel in each node are basically consistent.The stress cloud diagram of the beam steel transfers to the offset side,and the stress cloud diagram of the column steel concentrates in the core area of the node towards the offset side.From the perspective of concrete stress,the maximum stress of the column concrete is along the 45-degree direction of the beam section,because the column concrete surface is in a composite state of shear force and bending moment transmitted from the beam end.The stress cloud diagram of the beam concrete presents a symmetric distribution along the Y direction of the beam section.Finally,the tensile and compressive stresses inside and outside the concrete present a skewed band-shaped distribution,indicating that the concrete follows the "oblique strut" mechanical model.(5)The hysteresis performance of two types of nodes under cyclic loading was studied.The load-displacement curves of the 12 nodes show a full hysteresis loop without pinching,indicating good seismic performance at different displacement angles.Increasing the displacement angle increases the load-carrying capacity and energy dissipation capacity of the node,causing the skeleton curve to expand outward.The average ductility coefficient of the two nodes is between 4.26 and 5.88,and increases by 4.8% for every 6° increase in displacement angle.The average equivalent viscous damping coefficient of the 12 specimens is between 0.31 and 0.36,indicating good energy dissipation capacity of the nodes.Increasing the displacement angle leads to the degradation of strength and stiffness,and the degradation curve expands outward.In terms of ductility,increasing the displacement angle causes the average yield displacement and peak displacement to decrease,with a decrease of 2.84% and 2.06% on average,respectively,for every 6°increase in displacement angle.(6)Based on the results of finite element analysis,the shear bearing capacity of two types of nodes was analyzed.The calculation formula of the shear bearing capacity of the steel-concrete composite beam-column nodes was obtained by the superposition method.At the same time,the calculated values of the formula were compared with the finite element simulation values to verify the correctness of the calculation formula for the shear bearing capacity of the nodes.Figure[68] Table[13] References[64]... |
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