Study Of Optimization And Controlling Research In Structural Seismic Reliability

Objectively considering the random phenomenon during structural design,construction and using structural reliability theory can meet the optimization relationship of safety and economic. Structural reliability theory has become theoretical foundation of design code and the hot issues of domestic and international research. As load-control of most engineering, earthquake is one of the major natural disasters which cause destruction of building structure and casualties, such as wenchuan earthquake 2008. Improving the aseismic capacity by reliability has important significance.Based on the characteristics of structure seismic failure mode, failure mode correlation is expressed by generalized reliability index vector in complicated conditions, then, the characteristics of structure seismic failure mode is studied by modal pushover analysis. The weakest failure modes theroy is presented by the characteristics of failure modes. Based on above outcomes of study, sturctural performance optimization and control of weakest failure modes is proposed, concrete contents is as follows:Firstly, the generalized reliability index vector is putted forward based on correlation calculation of dependent random variables, the unified computation model is studied. The reliability index vector reveals the vector character of reliability index, which solves the failure mode correlation in some extent. As the existing of the dependent of random variables,the complexity of failure modes and the contains of same component of failure modes, correlativity existed among components or failure modes. The generalized reliability index vector is proposed in generalized stochastic space namely affine space based on reliability index vector. Correlation coefficient of random variable is projected to angle of the generalized stochastic space, and the optimization design model is proposed. The correlation of failure modes and the model of resistance and load are studied under the complicated conditions (coupling of resistance and load) of constitutive relation.Secondly, theoretical studies and practices indicate that structural reliability can be expressed as weakest failure mode under single random load, structural system can be optimized by optimization of the weakest failure mode. The application of weakest failure mode theory meets with difficulties during structural analysis under complicated mechanical effects. The theory of weakest failure modes is proposed based on probability measure, the structural reliability is solved by weakest failure modes, and the structural reliability can be optimized by optimization of the weakest failure modes. The reliability index vector-PNET method is proposed to identify the weakest failure modes. The feasibility is verified by optimization example.Thirdly, a model of structure-property design based on weakest failure modes is proposed. Performance-based seismic design of structures fully meets the requirement of owner,user and designers. The extinguishment loss expectation of this model is composed of weakest failure modes loss, instead of product of the failure modes and failure loss. The characteristics of structural performance is fully considered, which embodies principles of performance-design,safety and economic, on the other hand, the complexity of structural reliability and failure loss calculation is avoided.Fourthly, this paper provides a seismic reliability evaluating method based on higher order Pushover analysis. The modal Pushover analysis (MPA) is used to identify the dominant failure modes, and the dynamic analysis of structure was transformed into static extremum analysis. The MPA program is implementation based on OPENSEES. The relationship of failure modes and basic vibration modes was established due to the theory of weakest failure modes of structure and research results of MPA, the analysis of structural seismic reliability was transformed into combination of edf (equivalent degrees of freedom) member reliability. The parameters and methods of structural seismic reliability reference for anti-earthquake code and seismic model parameters in our country. The paper has certain significance to the theory of seismic reliability and the earthquake safety evaluation in our country.Fifthly, this paper investigates reliability-based optimization of structural anti-disaster. At first, the random Pushover analysis method was developed, and the Pushover-bound analysis was proposed, which is used to identify structural dominant failure modes by generation of failure path; secondly, a process of seismic reliability-based optimization of structural system base on control was proposed, by nesting the optimization of the weakest failure modes in control model, the control of structural system reliability was realized. Actual calculation example showed that structural reliability can be improved effectively by this method. The research has certain significance of basic research of structural anti-disaster reliability.