Experimental Study On Mechanical Behaviors Of Aluminum Foam Composites And Their Application In Seismic Energy Dissipation

Structural energy dissipation technology(SEDT)as an effective anti-earthquake technique has been widely used in civil engineering.As we know,the performance of SEDT mostly depends on its damping material.The development of the SEDT will be promoted,when an innovative material both had high damping and stiffness is developed.The Aluminum Foam/Polyurethane composites(AF/PU)were fabricated by the infiltration method that infuses polyurethane(PU)into the spherical open-cell aluminum foam(AF)scaffold.AF/PU are the typical interpenetrating phase composites that combine both properties from PU and AF.In order to make AF/PU has a broad application in SEDT of civil engineering,there are two aspects are systematically and deeply researched in this paper,including the mechanical behaviors of AF/PU and their application in seismic energy dissipation.The experimental and theoretical studies of AF/PU under the monotonic and cyclic compression are presented in the aspect of mechanical behavior.In the second aspect,it does not only contain the performance test and mechanical model of the AF/PU friction dampers,but also include the vibration control of the hybrid AF/PU damper in adjacent buildings.Therefore,the main research works and achievements are as follows:(1)The mono tonic compression behaviors of AF/PU were tested and compared with those of the pure AF and PU.The contribution of PU cover to the mechanical behaviors of AF/PU is analyzed and the variation of the compression behaviors of AF/PU with their aluminum volume fraction is discussed.The results show that the compressive strength and stiffness of AF/PU are mainly affected by their aluminum volume fractions,but the contribution of PU is so negligible that the influence of PU cover can be ignored.The Avalle's macroscopic phenomenological constitutive model is used to simulate the monotonic compression behaviors of AF/PU,and the model results are in good agreement with the experimental results.(2)The cyclic compression tests of AF/PU were carried out.The effects of strain amplitude,strain rate and cyclic number on the mechanical parameters of AF/PU are investigated.The mechanical parameters contain peak stress,deformation modulus,energy dissipation capacity and residual strain.The results reveal that the energy dissipation mechanism of AF/PU in cyclic compression is mainly from the interfacial damping of AF and PU.Based on tested results,the simplified four linear model for engineering design is established.This model can reflect the macroscopic behavior and hyper-elastic behavior of AF/PU during the cyclic compression process,and this model is found to adequately capture the cyclic compression response of AF/PU by comparisons with experimental data.(3)An innovative AF/PU friction damper is designed and fabricated.Experiments were taken to investigate the influence of pre-compression,loading frequency,displacement amplitude and cyclic number on this damper' s mechanical behaviors,including damping force,stiffness and dissipated energy.According to experimental results,the Bouc-Wen model is modified to simulate the mechanical characteristics of AF/PU friction damper.The parameters of Modified Bouc-Wen model are identified by narrowing the range of parameters value in two steps when using the genetic algorithm.All of the results demonstrate that AF/PU friction damper is a typical displacement-correlated and variable-stiffness's friction damper,and it has some advantageous properties such as high-dissipated energy and variable stiffness.(4)A new type of hybrid AF/PU damper is developed,which composes of a friction element in parallel with a compression element.The influence of loading frequency and displacement amplitude on the mechanical behavior of hybrid AF/PU damper is examined.Based on OpenSees software,the linear segments model is compiled to simulate the hysteretic response of hybrid AF/PU damper.Finally,the adjacent 8-storey and 3-storey frame buildings are selected as the modeling example.The hybrid AF/PU damper is adopted to analyze the pounding-involved and seismic response of these two buildings under the ground motions with different peak acceleration.The hybrid AF/PU damper is found to have a better earthquake mitigation effect and seismic pounding avoidance in adjacent buildings when compared to vibration absorbing material and fluid viscous damper.