Develop And Research On Nonlinear Seismic Program Of Steel Frame Structure

Earthquake disaster and their secondary disaster do enormous economic losses and casualties to human beings, and seismic design of building structures is an active measure.With the development of economy in our nation, steel structure is taking a bigger and bigger quotient of the construction market, and seismic research of steel structures turns to extremely significant problem. Although steel structure shows excellent seismic performance, it is still not enough under infrequent earthquake, and would enter plastic state. It is been proven by enormous analysis and earthquake disasters that the plasticity will concentrate at weakness storey. Code for seismic design of buildings (GB50011-2001) specifies the checking method of storeys displacements, such as pushover method and time-history method, when structures are under infrequent earthquakes. However, they are not generalized considering the function limit of present structure design softwares and the time cost in engineering design.With the widespread of cheap personal computer and the development of finite element theory and structure design theory, work in modern structure analysis and design must be finished with software. Therefore, structure analysis software is necessary considering the requirement of either structure design or theoretical research. Because of the continuous improvements of finite element theory and structure design theory, maintainability and expendability is required for the software. Object-oriented method is undoubtedly the best choice in all the software engineering method.Based on the above consideration, a nonlinear analysis program is developed and the simplified method checking plastic deformation when the structure is under infrequent earthquakes is discussed in this thesis.The principle of pushover method is presented first in this paper, and the effect of different horizontal load distributions is compared. It is easy to bring capacity spectrum method into seismic design, so detailed explanation about equivalent single degree of freedom manner and the flow process diagram is provided.P-δeffect is contained by adding geometry stiffness to global stiffness, and is calculated by updated Lagrange method. Nonlinear hinges are used to contain the material property. Obviously, there are many nonlinear hinge models, thus the section assemblage method is chosen considering accuracy and stability in numerical calculation method.When developing the finite element software using object-oriented technology, the standard object-oriented software process is abided by. A code level release is obtained through use-case model and analysis model. Thanks to pushing mission from client to server and restricting the sharing between server and client method etc. a software release with excellent maintainability and reusability is obtained.A set of steel frames are analyzed with pushover method using the nonlinear analysis program, and the performance states under infrequent earthquake are got. With the help of capacity spectrum, the elastic and elastic-plastic displacement is derived when frames are under ultimate load-carrying capacity state. The enhancement coefficient can be used to check the deformation under infrequent earthquake. At the same time, the recommended method, specifying the location of the weakness storey, is carried out. Unfortunately, it is proved to be an unsuitable one when the whole bending effect and second order effect of dead load are obvious, and full pushover analysis is required..