| ECC(Engineering Cementitious Composites)is a fiber reinforced cementitious composites,and the fiber distributes disorderly.ECC has earned widespread attention since1990 s.ECC has significant deformation ability,high toughness,good energy absorption ability and crack harmless dispersion ability.It can be used to improve the durability and seismic behavior of structure.In this paper,we use high volume fly ash instead of partial cement,Polyvinyl Alcohol Fiber(PVA)and polycarboxylate superplasticizer to make a new class of ECC-Green High Performance Fiber Reinforced Cementitious Composites(GHPFRCC).Through the experimental study and numerical simulation,we studied the mechanical properties of GHPFRCC and the seismic performance of earthquake damaged RC column strengthened by GHPFRCC.The main research content is as follows:(1)The experimental study on elastic modulus of GHPFRCC.We measured the axial compressive strength and elastic modulus of GHPFRCC through prism static compressive elastic modulus test,and analysized such influence factors as water/cement ratio,sand ratio,dosage of PVA fiber,dosage of agent,fly ash replacement ratio.We test 16 groups with different mixture ratio GHPFRCC,the compressive strength of GHPFRCC is between 14 MPa to 40 MPa,and elastic modulus of GHPFRCC is around 16~35GPa which is lower than concrete.The analysis results show that water/cement ratio is the biggest impact on the compressive strength and elastic modulus;PVA fiber content is from 1.5% to 2% when tests results are good;the lower the dosage of fly ash the better mechanical performance.(2)The experimental study on constitutive relation of GHPFRCC.In the Prism static compressive test,in order to research the constitutive relation of GHPFRCC,we use the force sensor to measure force,displacement sensor to measure displacement and data acquisition instrument to collect data,and then obtain the stress-strain curve based on data processing.The influence of water/cement ratio,sand ratio,dosage of PVA fiber,dosage of agent,fly ashreplacement ratio on compressive strength and peak strain.The results show that the stressstrain curve of GHPFRCC is skewness unimodal curve,the descent part of curve is gently;peak strain ranges from 0.004 to 0.01,which is obvious bigger than concrete;above factors on GHPFRCC,the biggest impact on the peak strain is the dosage of fly ash,and the second is the water/cement ratio.(3)The finite element analysis software ABAQUS is used to simulate and analysis the seismic performance of RC column,to prepare for the next test.The simulation results show that: the bearing capacity of column reinforced by GHPFRCC is 33% higher than that of concrete column with same size,and ultimate displacement increased 1.88 times.(4)The experimental research on seismic performance of RC column damaged by simulated earthquake and strengthened by GHPFRCC with secondary load.There are four damaged RC columns reinforced by GHPFRCC(among of them,there are two columns have vertical load,namely secondary load),reinforcement height has 300 mm and 500 mm,altogether four reinforcement schemes.We obtain the hysteretic curve and skeleton curve after pseudo static test,analysis the stiffness and ductility of GHPFRCC columns,contrast each reinforcement scheme,and explore the secondary load effect on seismic performance.The results show that: when the reinforcement height is 500 mm,the bearing capacity,stiffness and ductility of columns exceed the level before damage;the seismic performance did not fully recover when the reinforcement height is 300mm;The secondary stress effectively improve the early crack resistance of the components,and the effect on stiffness and late limit displacement is not obvious;the ductility of components with secondary load is lower than that with first load,but better than the level before damage;the higher reinforcement height,the better seismic performance recover,and the retrofitted height at least more than a third column height can meet the seismic requirements. |
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