Vibration Control Effect of Viscous Damper on Space Structure

Supplemental damping is becoming an increasingly tested and reliable seismic design strategy,which has resulted in the evolution of building guidelines to include supplemental damped structures.The usage of supplemental viscous dampers to dissipate energy and reduce building response to dynamic inputs is gaining worldwide acceptance.The concept of supplemental dampers added to a structure is such that the dampers,rather than the structure itself,absorb much of the energy input to the structure from a transient.The placement of dampers is a critical design concern because the distribution of damping may significantly affect a building's dynamic response and the necessary damping cost.However,current building codes and guidelines have not yet prescribed a particular method for optimal placement of dampers.Although the 2003National Earthquake Hazards Reduction Program(NEHRP)provisions offers a methodology for determining the total damping value corresponding to a desired effective damping ratio,it does not address the optimal distribution of the dampers.This paper presents an application of viscous dampers in a space structure to suppress anticipated earthquake action.The northwestern Chinese region is an area affected by many earthquakes;therefore,seismic retrofitting of existing buildings presents many difficulties in this region.Any intervention in their structural system should neither violate their forms nor create dramatic changes in their structural behaviors.To study the vibration control of large-span space structures with viscous dampers,dynamic time-history analyses were performed for a gymnasium building subjected to three-dimensional earthquake ground motions.To evaluate the seismic performance of the space structures,three dimensional mathematical models were prepared by using FEA ANSYS software.The models incorporated geometric(P-Δ),material(member yielding),and viscous dampers(axial force-axial displacement hysteresis) nonlinearity.Seismic masses were calculated on the basis of the dead plus one-second live load combination.The finite element analysis results were used to investigate the response of the building and to determine the extent of nonlinear response in members.The targets of the vibration control were to reduce horizontal displacement and member forces for the roof structure,as well as storey displacement and storey shearing force for lower frame structures.The results indicate that the seismic response reduction of the roof structure was obvious under various seismic waves,although the effect of vibration control of the lower frame structure was sensitive to earthquake frequency characteristics.The use of viscous dampers can dramatically reduce displacements and internal forces of the upper and lower structures various different seismic intensities.Uniform placement of the viscous dampers showed better vibration control performance when compared with centralized placement on the roof of the space structure.Moreover,the mode of vibration was complex for space structures,and interaction between the upper and lower structures needs to be considered in vibration reduction analysis because of its great effect on seismic response of space structures.The viscous damper system proves to be a very effective method for reducing seismic response.These research results will provide a useful reference for practical application of viscous dampers in super-long-span space structures.