Study On Performance Improvement Of Existing RC Frame Structure Retrofitted By Ultra-lightweight Insulation Cementitious Composites

In China,there exist a large number of reinforced concrete(RC)frames with structural degradation after decades of service.The seismic performance and thermal insulation performance of these RC frames can not meet the requirements of codes and standards.If the performance improvement is needed,the general method is thermal insulation after retrofit.This method will take a long period.Quality of post glued insulation board cannot be guaranteed,meanwhile it may cause environmental pollution.How to retrofit existing RC frame to improve the seismic and thermal insulation performance rapidly has become an important issue to be solved.Ultra-Lightweight Insulation Cementitious Composites(ULICC)was mixed using Hollow Glass Microsphere(HGM)as fine aggregate is introduced in this thesis.Mechanical and thermal properties are studied.ABAQUS is used to establish RC frames with infills retrofitted by ULICC layers.Seismic performance of FEM models are taken into concern.The main research works in this thesis are shown as follows.(1)Eight groups of specimens considering different water binder ratio and HGM proportions,with density of 1071kg/m~3～1358kg/m~3are prepared for experiments.Mechanical experiments indicate that the compressive strength are35.2MPa～57.1MPa.The value of compressive strength decreases with increasing of HGM proportion.A linear correlation exhibited between compressive strength and HGM proportion.The size effect is not obvious.The value of compressive strength deceases with the water binder ratio increases.However,water binder ratio effect on compressive strength slightly.The tensile strengths of specimens are2.25MPa～3.09MPa,with ultimate tensile strains of 1.8%～2.85%.The strain hardening effect is obvious,which shows a good deformation ability.Tension constitutive equations are proposed for FEM analysis.(2)Thermal conductivity coefficient between 0.193W/mk to 0.227W/mk are obtained by tests.Thermal conductivity coefficient decreases with HGM proportions and density decrease.A linear correlation exhibited between thermal conductivity coefficient and HGM proportion.Thermal conductivity coefficient also decreases due to water binder ratio increases.Values by existing formulas are fit test results well.Kinds of materials of wall are prepared to illustrate the excellent performance of ULICC.The thermal insulation performance can be improved obviously by using ULICC.(3)Availability of FEM models is verified by comparing with previous experiment.FEM models of RC frames with full-filled infills retrofitted by ULICC layers are established.The main parameters considered are the dimensions of retrofit panels and the thickness of layer.Hysterestic loops,skeleton curves,stiffness degeneration curves,characteristic values,ductility coefficient,and energy dissipation capacity are compared by FEM analysis data.Analysis data illustrates that the initial stiffness,peak load,ductility coefficient,and energy dissipation capacity are increased after retrofit.Strip layers lead to a good energy dissipation capacity and ductility.However,stiffness of each frame is almost the same at the end of loading.Initial stiffness increases due to thicker retrofit layers.Stress of infills decreases because of retrofit layers.The seismic and thermal performance of existing RC frames are improved after retrofitted by ULICC.