| Reinforced concrete(RC)frame structures are widely used in various buildings.As the key bearing parts of RC frame structures,the mechanical properties of RC joints have a decisive influence on the overall safety of RC frame structures.Therefore,ensuring the excellent mechanical properties of RC joints is a necessary condition to ensure the safety and durability of RC frame structures.However,a large number of earthquake damage shows that many RC frame structures have node shear failure under the action of ground motion.The reason is that the design of nodes in the existing design specifications of concrete structures is based on the plane nodes with unidirectional force on the main shaft.However,in the actual structure,the form of nodes has spatial property,and due to the randomness of ground motion,they may withstand ground motion from any direction,namely,bidirectional or oblique(bidirectional simultaneous)force.Therefore,in order to clarify the mechanical performance of RC frame space nodes under two-way stress,the research contents and achievements are as follows:1.The monotone loading tests of one plane node and three RC space nodes under bidirectional loading are carried out.The results show that the shear capacity,stiffness and energy dissipation capacity of space nodes are worse than those of plane nodes under bidirectional loading.It shows that the RC space nodes under the bi-directional force are more disadvantageous.2.The mechanical properties,such as shear capacity,energy dissipation capacity,stiffness,ductility,etc.of RC space joints under two-way stress were determined under different loading angles and stirrup ratio.The results show that with the increase of the loading Angle(0°～45°),the shear capacity,stiffness and early energy dissipation capacity of the space node decrease under the two-way loading.With the increase of stirrup ratio(1.88%-3.35%),the shear capacity,stiffness and early-stage energy dissipation capacity of space nodes under bidirectional stress increased.3.By analyzing the stress characteristics of RC space joints and combining with the existing stress mechanism of plane joints,a numerical calculation model of the shear capacity of RC frame beam-column space joints based on the softening tension-compression rod model is established,and the corresponding calculation method of shear capacity is given.4.By using ABAQUS finite element software,the parameters affecting the shear performance of RC frame beam-column space joints were expanded and analyzed,and the influences of axial compression ratio,loading Angle and stirrup ratio on the shear capacity,stiffness,energy dissipation capacity and ductility of the joints were determined. |
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