Theoretical Analysis of Load-Displacement Hysteresis Curve of Concrete Filled Steel Tubular Columns and Beam Joints
The study of the load-displacement hysteresis curve of the beam end of the concrete-filled steel tubular column beam and the hysteresis curve is the basis of the elastoplastic seismic response analysis of the CFST structure. Theoretical analysis of the load-displacement hysteresis curve is of great significance for studying the hysteretic behavior of concrete-filled steel tubular beam-column joints and the design of test specimens. In addition, by comparing the theoretical calculation results of the load-displacement hysteresis relationship curve with the experimental results, the correctness of the restoring force model of the node core region can also be verified.
For the theoretical calculation of the load-displacement hysteresis curve of the concrete-filled steel tube and column beam joint beam, no one has done this research. 51. In order to make the theoretical calculation as close as possible to the actual situation, the numerical analysis method is used to calculate the load-displacement curve.
1 Calculation method of load-displacement hysteresis curve of concrete-filled steel tube and column beam joint beam Li Traditional calculation method The traditional calculation method is obtained by referring to the method 52 of calculating the beam end displacement of reinforced concrete beam-column joints. Take a side column node as an example, the fund project: the National Education Commission Outstanding Young Teacher Fund Funded Project; the Heilongjiang Provincial Excellent Returned Scholars Funded Project to explain the steps of the traditional calculation method. Considering the side column joint under the vertical load of the beam end, the beam end displacement can be decomposed into the following three components.
The displacement of the beam end caused by the deformation of the beam is caused by the deformation of the beam. The displacement of the beam end is caused by the shear deformation of the core region. The displacement of the beam end can be expressed as follows: Fixed, freely cantilevered beam at one end. Under the vertical reciprocating load of the beam end, the beam itself is deformed into! ". Beam end displacement caused by column rotation 2) The column is regarded as hinged at both ends. Under the vertical reciprocating load of the beam end, the rotation of the center point of the column is. If the length of the beam is and the stiffness is infinite, the column is rotated. The induced beam end displacement is the beam end displacement caused by the shear deformation of the core area of ​​the joint. 3) Due to the large shear force of the core area of ​​the joint, the shear deformation cannot be ignored. Under the vertical reciprocating load of the beam end, the core area of ​​the node When the rotation is ".", the beam end displacement caused by the shear deformation of the core region is superimposed on the above three parts, and the final actual displacement of the beam end is obtained. The traditional calculation method is characterized in that the column deformation includes the bending deformation of the core region. That is to say, when calculating the deformation of the core area, only the shear deformation can be calculated.
Beam deformation column deformation core deformation 1.2 improved calculation method The so-called node core area is the connection between the beam and column, it is a section of the shear force is relatively large, it also has bending deformation.
The traditional calculation method is to separate the bending deformation and shear deformation of the core region of the node, and calculate the bending deformation of the core region of the node in the entire column, and calculate the shear deformation separately. Although the concept of this analysis method is clear, in the actual test, the two deformations cannot be measured separately, that is to say, the deformation of the core region measured in the test includes both the bending deformation of the core region and the shear deformation thereof. In response to this situation, an improved calculation method is proposed.
Taking the side column node as an example, the beam end displacement can be decomposed into the following three components under the vertical load of the beam end.
The deformation of the beam itself is the same as the traditional calculation method. Under the vertical reciprocating load of the beam end, the rotation of the joint A of the column and the core zone is the deformation of the beam end caused by the rotation of the column. Under the action of the reciprocating load, the rotation of the core area of ​​the node is! 'j includes joint bending deformation and shear deformation). Then, due to the deformation of the core region, the displacement of the beam end is the superposition of the three parts of the actual displacement of the beam end, and the final actual displacement calculation method of the beam end is obtained. The bending deformation and shear deformation of the core region of the joint are comprehensively considered. , the calculation does not distinguish, so you can examine the comprehensive deformation ability of the core area of ​​the node.
Resilience calculation model 2.1 Resilience model of steel beam The commonly used restoring force model for steel beams is a two-line resilience model, as shown.
2.2 Moment-curvature restoring force model of concrete filled steel tubular members
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