The System Reliability Analysis Of Steel Frames With Semi-rigid Connect

Steel frame 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 and the using steel qualities of bracing system and joints are small. So adopting a semi-rigid jointed steel frame is economical and stable. But for semi-rigid connections are complex and variable, 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.The building as a whole must meet the enough structural reliability. We must study the system reliability of the structure to avoid the shortcoming of design nowday.In the paper, I employ the theory of finite element of steel frames and Monte carlo method, describe the production method of the random variable of the average-distribution N(0,1) and write program with Fortran 90. The random numbersis tested in many ways for its quality ; The result is good. They can produce random with all kinds of probability distribution. Then after a semi-rigid joint behavior can be modeled as a finite stiffness rotation spring, base on rotation and displacement equation derive the element stiffness matrixes with semi-rigid connections where the effects of jointed flexibility and shear forces in the connection deformations have been considered in and fixed-end forces are modified. Finally, a program for calculating system reliability of semi-ridge steel frames with Monte carlo method and finite element analysis has compiled for calculating and analyzing.By calculating results of several examples for steel frame in semi-rigid joints case show the change of joint stiffness and other kinds of factors affect the systemreliability of semi-rigid steel frames. The examples also show that in some range of joint stiffness the system reliability index of semi-rigid steel frames increases. The purpose of the paper give a calculating method that accords practical engineering and easily put into effect. Worthwhile it is going to promote the development of semi-rigid jointed steel frame in design and heighten structural stability.