Study On Analysis Method And Design Theory Of Structures With Supplemental Viscous Damping

In traditional structures, there are such typical members as beam, column, plate, wall, shell, and cable. Due to absorbing excessive earthquake energy, some members may enter into elastic-plastic state, even yield or fail under strong earthquake, with a consequence of repair failure later or direct collapse. Dampers added to structures are responsible for consuming energy introduced by earthquake or other dynamic inputs. The supplemental energy dissipation systems can be used to control story drift, improve or upgrade the structural seismic performance of new or existing building. This technology has been becoming one tendency of earthquake engineering research and practice. Scholars and engineers of this domain in many countries are being engaged in this field of research and practice.The basic principle of consuming energy is firstly discussed in this paper. Increasing supplemental viscous damping will significantly reduces the dynamic displacement response of the system when the excitation period is nearly the same as the natural period of the system. The damping in a viscous damper is the same as the inherent damping that is assumed as viscous damping, which is likely to make it easier and exacter analyzing a structure with added viscous dampers.A direct numerical integration of the equations of motion is a general method for analyzing damper-added structures. The motion equations of damper-added structures and the dynamic time-history analysis procedure are discussed in detail. The procedure can solve a SDOF system, a MDOF system, a system considering torsional responses, or a three-dimensional finite element system. When the structure keeps elastic except for the local nonlinearities, the so-called fast nonlinear analysis (FNA) method is desirable for an elastic response history analysis.For linear structures, the modal analysis in the time domain and response spectrum analysis are well known, which are the carefully researched objects of this paper. The paper demonstrates that only using acceleration response spectrum is not enough for analyzing damper-added structures, and that for analysis of such structures it is appropriate simultaneously applying acceleration response spectrum, velocity response spectrum and displacement response spectrum. This approach works well for a MDOF system analysis by using modal superposition. The basic theory on damper-added structure is quite perfect in America and Japan. However, the response spectrum analysis method advanced in this paper is an important contribution, because time-history analysis has to carry through before even for the relatively rigorous and completesolution of linear structures.When a viscous damper is placed in different floors, the change characteristic of displacement, velocity and acceleration is studied. The study shows that displacement changes regularly along with a damper in a different floor, and that velocity does similarly, but acceleration changes irregularly. A structure example shows supplemental viscous damping can control interstory drifts of three-dimensional structures, which may be caused by both interstory translational and torsional responses.This paper suggests that dampers are likely candidates for meeting one seismic fortificationgoal------Goal A, Goal B, or Goal C. The corresponding design stages and the details of seismicdesign are advised. For a SDOF system, damper parameters can be acquired from a series of assumed parameters. For a MDOF system, how to determine the desired additional damping ratio is proposed. The damper placement strategy is proposed in which a performance index is maximized at each step to determine the optical location of a damper. The basic idea is to place each damper at a location experiencing the largest relative displacement between the clamper's attachment points. The design of a damper-added structure can now be carried out on the basis of the above development. The research leads to significant progress in design theory of supplemental energy dissipation system.The direct displacement-based seismic design method and the energy design method of damper-added structures are discussed. The direct displacement-based seismic design method undoubtedly is a help to design a structure, but much work demand before the method is used widely. As to the energy design method, assumed that about 80% of earthquake energy is dissipated by adding dampers, the damper sizes can be deduced. The energy design is an approximate and assistant procedure, which needs thorough research.Four design examples of damper-added structures, which can be referenced by designers, exhibit the theory presented in this paper.In a word, this paper mainly studies the seismic performance, the analysis method and the design approach of structures with supplemental viscous damping, and founds a perfect and practical theory on analysis and design of damper-added structures, which is of particular value to structure engineers and researchers. Energy dissipation is an effective means for improving earthquake response performance and damage control of structures. The Spring of this technology is being coming on.