Structural Systems Reliability-based Optimization Design For Planar Steel Frames

Uncertainties in engineering structures are objective phenomenons, which affect the safety of the structures. The probability design method for engineering structures has considered the uncertain factors in the actual projects, such as in structural design, in construction and in the process of use. Therefore probability design method has a wide range of value. The reliability analysis for structures is based on the theory of probability. So the reliability analysis follows trend of structural analysis. At the same time, the theory of optimization design, such as minimum weight design, considered the economic value of the buildings, so it attaches importance to engineers. This thesis is for the purpose of discussing optimization design method for planar steel frames, corresponding to computational methods for the reliability of engineering structures.First, this thesis introduces the concept of structural reliability and calculation methods for reliability of engineering structures. Radom variables and stochastic processes in structures design, including their probability distribution, are discussed. In this thesis random variables'denpendent is considered, and introduces normal tail approximation method for non-normal random variables. This thesis introduces the limit state of structures and reliability index. Based on the existing computational methods, structural reliability is analyzed. This thesis introduces the following things. The significant modes are identified by using the Branch-and-Bound method. The reliability of structures is evaluated by First-Order Second-Moment method, including the basic formula iteration and the procedure of Design point method. The reliability of structural systems is evaluated by PENT method and Monte-Carlo simulation method.Second, this thesis introduces the concept and the computing model of optimization design. Minimum weight design takes the structural systems reliability as the control parameter. Greatest structural systems reliability design is based on the structural weight given. At the same time, considering the particularity of steel frames, the stability of the thin plate is regarded by design variable link.Finally, this thesis analyzes the reliability of the single-storey planar steel frame. Based the analysis of the structural systems reliability, minimum weight design method is discussed. As a case, a single-storey planar rigid steel frame is designed and the result demonstrates that optimization design method presented in the thesis is effective. In the case, the computer software named"matlab"is used to solve the problem of optimization design with the constraint of I-type section structural systems reliability. Then the monte-carlo method is used to simulate reliability index of the structural systems.