土建--毕业设计总依据及设计步骤(案例2

土建--毕业设计总依据及设计步骤(案例2内容摘要：

d is a function of area , length, moment of inertia, and Young’s modulus of an element and and ＝ transformation matrix and the geometric stiffness matrix. The internal force vector in Eq. (1) corresponding to the frame can be defined as where =homogeneous part of the internal nodal force vector and =deformation difference vector. The detailed expressions for evaluating all the matrixes in Eqs.(1) through (3)for the frame are given by Gao and Haldar(1995) and are not repeated here due to lack of space. A fournode plane stress element is used to incorporate the presence of shear walls in the frame. An explicit expression of the stiffness matrix of the plate elements is necessary for efficient reliability analysis. To achieve this, the shape of the shear wall is restricted to be rectangular. Two displacement (horizontal and vertical) dynamic degrees of freedom are used at each node point. These are plane stress elements. Based on an extensive literature review and discussions with experts on finiteelement methods, it was concluded that the rotation at a node point could be overlooked. The rotation of the bined system at the node point is expected to be very small and was independently verified using a mercially available puter program discussed later. To bring the shear wall stiffness into the frame structure, the ponents of the shear wall stiffness are added to the corresponding frame stiffness ponents in Eq. (1). The explicit form of a stiffness matrix of a fournode plane stress element can be obtained as (Lee 2020) where 2a and 2b＝ long and short dimensions of the rectangular shear wall, respectively, t＝thickness of the wall, g＝ the ratio of b and a。 ., g＝ b/a. The matrixes A, B, C, and E in Eq. (4)can be represented as and where =modulus of elasticity and ＝ Poisson’s ratio of shear walls. Different types of shear walls are used in practice, but the reinforced concrete(RC)shear wall is the most monly used and is considered in this study. Thus, two additional parameters ,namely, the modulus of elasticity and the Poisson’s ratio of concrete ,are necessary in the deterministic formulation as in Eq.(8). The tensile strength of concrete is very small pared to its pressive strength. Cracking may develop at a very early stage of loading. The behavior of a RC shear wall before and after cracking can be significantly different and needs to be considered in any realistic evaluation of the behavior of shear walls. There has been extensive research on cracking in RC panels. It was observed that the degradation of the stiffness of the shear walls occurs after cracking and can be considered effectively by reducing the modulus of elasticity of the shear walls. Based on the experimental research reported by Lefas et al. (1990), the degradation of the stiffness after cracking can vary from 40 to 70% of the original stiffness depending on the amount of reinforcement and the intensity of axial loads. In this study, the behavior of a shear wall after cracking is considered by introducing the degradation of the shear wall stiffness based on the observations made by Lefas et al. (1990). The shear wall is assumed to develop cracks when the tensile stress in concrete exceeds the prescribed value. The rupture strength of concrete , according to the American Concrete Institute (ACI, 1999) is assumed to be = , where =the pressive strength of concrete. Once the explicit form of the stiffness matrix of shear walls is obtained using Eq. (4), the information can be incorporated in Eq.(1) to study the static behavior of the bined system. The finiteelement representation of the RC shear walls is kept simple in order to minimize the number of basic random variables present in the SFEM formulation. More sophisticated methods can be attempted in future studies, if desired. One of the main objectives of this study is to demonstrate the advancement of the reliability evaluation of plicated structural systems, and in that context, the method is appropriate. Reliability evaluation procedures are emphasized in this paper. The governing equation of the bined system consisting of the frame and shear walls, ., Eq. (1), is solved using the modified NewtonRaphson method with arclength procedure. Verification of Deterministic FiniteElement Method Formulation The success of any reliability method depends on the accuracy and efficiency of the deterministic method used. The basic deterministic method used in this study was discussed briefly in the previous section. A very sophisticated assumed stressbased nonlinear FEM algorithm was used to represent the steel frame. The shear walls are represented using information from experiments. The adequacy and accuracy of the FEM representation are necessary at this stage. A twostory twobay frame structure with shear walls in each floor is considered, as shown in Fig. 1. All columns are made of a W12 58 section and all beams are made of a W18 60 section. The pressive strength of concrete in shear walls and its Poisson’s ratio are assumed to be Mpa and , respectively. Principal stresses are calculated at node points. When the stress in the principal direction exceeds the prescribed tensile stress, the reduced modulus of elasticity of concrete is assumed to be 40% of for the element. All material and sectional properties required to analyze the bined system are given in Table 1. The bined system is subjected to dead, live, and horizontal load applied statically to represent wind or seismic load. The pattern of loading is shown in Fig. 1 and the intensities are given in Table 1. A puter program denoted hereafter as Shdyn is specifically developed to implement the concept. The program provides the structural responses at each node in terms of displacement and force. For the verification of the deterministic algorithm considere。