Research And Application On Seismic Capability Of Steel Frames With Semi-rigid Connections

There are many forms of tall steel structures, however frame structure is the most basal one. In conventional analysis and design of steel structures,it is usually assumed that the connections between columns and beams are either rigid or pinned . The analysis of steel frames adopting the assumption can simplify the procedure of analysis and design, but cannot precisely reflect structural practical circumstance and the errors of calculating results are large, even, get incorrect conclusions.In recent years, quite a lot of earthquakes in the world indicate that steel frames with welding joint easily occur brittle collapse because of having a low ductility at joints. Then, a semi-rigid connected steel frame has large the energy absorption capacity which can resist dynamic loads. The purpose of this paper gives some theoretic reference for seismic design of steel frame structure through the elastic-plastic analysis on the seismic capability of steel frame with semi-rigid connections under severe earthquakes.In the paper, at first, some models of relations between moment and rotation of semi-rigid connection are introduced. Then a semi-rigid joint behavior can be modeled as a finite stiffness rotation spring. Basing on rotation and displacement equation, we obtain the element stiffness matrixes with semi-rigid connections where the effects of material nonlinear, hysteresis behavior and shear forces in the connection deformations have been considered in and at the same time we modify the fixed-end forces. Finally, a program for calculating the elastic-plastic earthquake seismic of semi-rigid connected steel frame structure by step and step integration of wilson-θ.In this paper, the author compares and analyzes the effect of semi-rigid in the behavior of steel frame structures. The calculation results indicate that for steel frame in semi-rigid joints cases, the top story deflection, the displacement between two stories, the moment at the center of a beam and the initial end moment at column is larger, nevertheless the end moment at beam and the shear force between two storiesmay be smaller when compared to the rigid joints case. Effect of the semi-rigid joint can be reduced by some measures such as the use of bracing members. In this way, we can make good use of the excellent dynamic behavior of semi-rigid connect steel frame structure and decrease the cost of engineering. At last, some new design methods and demand in the constructing which are in accord to practice and easy to applied to design are put forward.