الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
During the last five decades, a lot of efforts were exerted to develop advanced analysis methods that can explore the uncertain information of structures response due to geometric and material nonlinearities. Finite element methods can be employed for the advanced analysis using beam-column or using a fine mesh of shell or solid elements. Analysis using beam-column elements can save much time required for analysis using shell or solid elements. This work presents a new model to perform inelastic large deflection analysis of space steel frames depending on the spread of plasticity method. A stiffness matrix of a beam-column element with only two nodes and six degrees of freedoms for each node is derived to represent the frame member. The proposed matrix includes the effect of section yielding along the member as well as the effect of large deflection. Stiffness degradation at the cross-section due to yielded parts is calculated using a formula for the tangent modulus which is affected by the sectional internal forces. The proposed technique of accumulation of rigidity factors is submitted as a first step to get exact first order stiffness factors for a member with variable cross section. The effect of large deflection is included by considering the axial force while deriving the stiffness factors. Both cubic and higher order displacement functions are tried to produce an element that can represent the member without discretization. A finite element program based on stiffness matrix method is developed to predict the inelastic large deflection behavior of steel space frames using the derived stiffness matrix. The proposed finite element technique exhibits good correlation when compared with the conventional spread of plasticity model results. Verification by solving benchmark steel frames is carried out. In case of high axial force, the proposed technique has more accurate results for the models based on the higher order displacement function than the model based on cubic displacement function. The difference is due to the limited representation of geometric nonlinearity in the cubic displacement function. The analysis results indicate that the new model is accurate with simple equations and it achieves a significant improvement to the run time.