Research On The Seismic Design Issues Of Complex Structures

Complex building structures,such as high-rise building structures and large span structures,develop rapidly nowadays,which needs higher requirements on structural design.Based on the problem-oriented method and case studies,some seismic design issues of complex structures are discussed in this dissertation.It helps structural design professionals to cultivate the engineering systems thinking,avoiding following the specifications and soft wares blindly.The main work and results are as follows:1)Structural design methodology is discussed,which indicates that solid mechanics is the fundamental principle and the main goal is to design structures most economically on the basis of safety and reliability.Structural design is a technical problem and mechanics is basically important,so we are supposed to solve problems by realizing and utilizing the engineering mechanism.2)Seismic response analysis is discussed,as seismic design of structures is complicated.Response spectrum analysis(RSA)procedure and response history analysis(RHA)procedure are two main methods for seismic response analysis.RSA or RHA can be used for calculation of regular short-period structures,but RSA is not good enough for irregular structures or long-period structures.In this case,RHA is necessary.Elastoplastic analysis should emphasize discovering the weakness of structures,which is beneficial to determine the rationality of the design.3)Essences and expressions of structural assembly regularity are discussed.Regularity of building configuration and structural assembly govern the seismic performance of structures,which must be paid close attention to.It is important to recognize the essences of structural assembly regularity.Regularity can be generally described as simple,uniform and direct,while irregularity is opposite.There are some recommendations for structural design,such as decreasing stress and strain,avoiding stress concentration or uneven deformation,avoiding stiffness or bearing capacity mutations and assuring direct force transmission.4)Seismic design of high-rise building structures is discussed.Resistance to horizontal dynamic forces is important for high-rise building structures,and there are some basic methods to improve its efficiency,such as fully using axial force,making materials away from the neutral axis to increase the moment of inertia,enhancing the integrity of the structure and assuring direct force transmission.Comparative analysis of the frame-corewall structure and megaframe-corewall structure is conducted,which indicates the characteristics of force and deformation.Factors affecting the performances of these two types of structures are discussed and some design proposals are come up as well.5)Foundation design problems are discussed,and recommendations for reliability design are proposed.Subsoil bearing capacity and deformation of foundation are critical for foundation design,and it is important to assure that the deformation of foundation is uniform or controlled.Foundation design must always be dominated by conceptual analysis and be supplemented by numerical calculation.By means of mathematical statistics,Delphi method and shared database,the reliability design of foundation may be established.