Ultimate Bearing Capacity And System Reliability Analysis Of Frame Structure Based On Elastic Modulus Reduction Method

The ultimate bearing capacity of the structure reflects the maximum capacity of its resistance of external loads, which is an important indicator for measuring the safety and reliability of engineering structures. Recently, the Elastic Modulus Reduction Method (EMRM) has been proposed, where the element bearing ratio (EBR) is defined by the generalized yield criterion. Using the reference EBR and uniformity of EBR, a dynamic criterion is proposed to identify the potential failure elements effectively. Then based on the principle of deformation energy conservation, a modulus adjustment strategy is established to imitate the structure failure process. Finally, the corresponding limit load are determined. Based on the research of the task group, the generalized yield criterion homogeneous are developed for the upper and lower limit analysis of. frame structure in this paper. Meanwhile, two new methods including stochastic ultimate bearing capacity and system reliability analysis method are proposed based on stochastic finite element method(SFEM) and EMRM. The results of the study are theoretically significant and valuable for the safety and reliability assessment of structures. The main contents of this thesis are as follows:(1) The EMRM for upper and lower ultimate bearing capacity of frame structure are established. And a method for the calculation of strain energy and dissipation work of linear elastic beam element structural is presented. Combining the sparse discrete grid built by beam and truss element and the EMRM format, the upper bearing capacity is achieved(2) Based on the homogeneous generalized yield criterion(HGYC), the EMRM for ultimate bearing capacity of frame structures is presented. Using regression analysis and least square method, the HGYC for I-shaped section is developed. Further, the EMRM is extended to the limit analysis of the frame structure.(3) Combining the SFEM with the elastic modulus adjustment strategy, two new methods including stochastic ultimate bearing capacity method and system reliability analysis method are proposed. Then a proportional relationship between the stochastic response of structures and external loads is determined. With the EBR at point of the mean value field being adopted as control parameter, the modulus adjustment strategy is established according to the conservation criterion of strain energy. Meanwhile, the Significant failure mode of stochastic structural is studied. Finally the stochastic ultimate bearing capacity field and system reliability of the structure are determined.