Experimental Research On Seismic Performance Of Framework Architecture With Ordinary RAC And EC-RAC

With the increasing of urbanization in our country, the urban pollution has becomeincreasingly serious due to the construction waste. However the recycled aggregateconcrete (RAC) is a new type of building materials with effectively using constructionwaste, which is in line with energy reduction, sustainable development of the nationalstrategy. Meanwhile it is also a effective way of saving non-renewable resources、improving the urban environment、promoting the development of economy. But, thebasic mechanical propertie of ordinary RAC is quite different due to different regionalwith different construction waste sources. Meanwhile, the current outcome of ordinaryRAC research shows that it had poor crack-resistance and ductility. Therefore, firstlyaiming at the local geographical characteristics of Xi’an, secondly based on the researchof different sources with waste concrete, this paper prepared three type of recycledaggregate with different sources、different service life with the processing of artificialfragmentation、 mechanical crushing、 washing、 and screening. Meanwhile thecorresponding research of basic mechanical properties of ordinary RAC was carried out.After that, based on the needs of performance, using of four different recycledfibers-polypropylene three aging fiber (PPF-1), modified polypropylene (crude) TANKfiber (PPF-2), radial steel fibers(RSF-1) and nylon fibers (RNF-2), mixed them into theordinary RAC, the enhancement RAC (EC-RAC)was obtained and correspondingmechanical properties were carried out. Based on the obtained basic material propertiesof test results, the experimental study on seismic behavior of RAC frameworkbeams(one ordinary concrete beam, three ordinary RAC beams and two EC-RACbeams),RAC framework columns(one ordinary concrete column, three ordinary RACcolumns and two EC-RAC columns). Finally, one RAC framework (reduced scale ratio 1:4) with variety of ordinary RAC and EC-RAC was completed and was study onseismic behavior experiment with shaking table test. Some innovative research wasobtained. The main research works are shown as follows:(1)Collecting three type of recycled aggregate with different sources、differentservice life with the processing of artificial fragmentation、mechanical crushing、washing、and screening,40groups recycled coarse aggregate and12groups recycledfine aggregate was carried out, and corresponding physical properties of graincomposition、apparent density、porosity、water content、clay content、crushing valueindex of air dry and saturated with surface dry were tested. The corresponding particleuniformity coefficient and the coefficient of curvature were calculated, which couldevaluate the basic indicators of inhomogeneous of recycled aggregate gradation、apparent density. etc. The results showed the gradation of recycled aggregate in thispaper was good for the preparation of recycled aggregate concrete.(2)With using the prepared three different service life of recycled coarse aggregate,considering different recycled aggregate replacement ratio, and according to the mixdesign method of ordinary concrete, with through test、adjust it, the final mix methodfor RAC was determined. After that91groups with273ordinary RAC blocks wereprepared, which were taken with relevant mechanical test of compressive strength、splitting tensile strength、flexural strength and deformation properties. All results wereestablished for the relationship and conversion formula between replacement rate rand f c/f cu; conversion formula between cube compressive strength and splitting tensile;conversion formula between cube compressive strength and flexural strength;conversion formula between cube compressive strength and modulus of elasticity;conversion formula between axial compressive strength and peak strain; conversionformula between the stress-strain curve of RAC and the replacement rate r.(3)Taking four different recycled fibers(PPF-1, PPF-2, RSF-1, RNF-2) into thereplacement rate of0%、30%、50%ordinary RAC respectively,150groups of450EC-RAC blocks were prepared to consider the impact of a single fiber、binary andternary hybrid fibers for the strength and deformation properties of ordinary RAC,which determined the variational rule of the strength index、peak strain、elastic modulus,established the EC-RAC of stress-strain (ascent) relationships with single、binary and ternary hybrid fibers under different replacement rate(0%、30%and50%).(4)Using the obtained results of basic material test, and taking different recycledaggregate replacement rate、different hybrid fiber content into account for simplysupported beam of bending and deformation properties, one ordinary concrete beam,three ordinary RAC beams and two EC-RAC beams were designed and produced andthe corresponding static loading experiment was also carried out. The damage rule andcharacteristics of the RAC beam was studied in the testing process. Compared crackingmoment、ultimate bearing capacity、cross-deformationother and the other characteristicsof load value between RAC beams and ordinary concrete beams and determined thevariational rule of them with different replacement rate and hybrid fiber content;Especially bearing capacity and deformation properties of ordinary RAC affected withhybrid fiber content. Through the results of the test, with using the least squares method,the formula of arm coefficient η, section of elastic-plastic resistance moment coefficientζ and steel fitting strain inhomogeneity coefficient were fitted. Meanwhile, short-termstiffness formula was established fitting for RAC beams, and the deflection of RACbeams under the normal use limit state was calculated. Finally, compared the results(simulated by ABAQUS finite element software) with experimental results, both ofthem were in good agreement.(5)Mainly considering different recycled aggregate replacement rate、hybrid fibercontent,6RAC columns(one ordinary concrete column, three ordinary RAC columnsand two EC-RAC columns) were designed and produced and the correspondinglow-cycle loading experiment was also carried out. Through the test, failure process andcharacteristics、the variational rule of damage process and character、hysteresis curves、skeleton curves、ductility、energy and other seismic performance indicators wereobtained. Especially bearing capacity and seismic performance of ordinary RACcolumn affected with hybrid fiber content.Through the analysis and fitting for the testresults, three fold linear of P-Δ restoring force model was established, which wasapplicable for RAC framework for column. Meanwhile, stiffness degradation formulasfor forward and reverse with loading and unloading process were fitted, and theskeleton curves and hysteresis curves for each column were calculated by usingrestoring force model. Finally, each column was simulated by ABAQUS finite element software under low-cycle loading and corresponding skeleton curves and hysteresiscurves were obtained. Compared the calculated results with experimental results, whichshowed that two results were basically same, which could verify the rationality andreliability of restoring force model and finite element model, and they could beanalyzed for the seismic performance of such elements.(6)A three-story framework was shrunk with1:4reduced-scale on the basis of aactual three-layer framework structure with the similarity theory. A three-story RACframe model was designed and produced. In order to effectively compare the seismicperformance of beams and columns, they were designed with different rates anddifferent fiber contents RAC concrete. In the shaking table test of the model structure,before each condition, the sweep of white noise was used to test the vibrationcharacteristics of the model structure; In accordance with seismic intensity from smallto large order, shaking table text was carried out with EL Centro wave, Taft wave,Lanzhou wave (artificial waves) under unidirectional and bidirectional input. And theearthquake disaster phenomena and trait of the model in all kinds of conditions havebeen obtained. Model layers acceleration and displacement response had been measured.Meanwhile the model acceleration amplitude(acceleration amplification factor)、displacement amplitude、 layer displacement displacement amplitude and layerdisplacement angle of displacement have been solved and the vibration law of the RACframework has been got. The seismic performance of ordinary RAC and EC-RACframework structure was analyzed and compared.(7)By means of the white noise sweep after various conditions, the auto-oscillationtrait of the structure(natural frequency、mode of vibration、damping ratio)was calculatedby MATLAB. Making use of the layer displacement amplitude and the experimentalphenomena, the division of RAC framework5levels of damage was established byreferencing related standard. Utilizing the frequency and damping ratio calculated invarious stages of experiment of the whole structure, and taking into account the impactsof the different stiffness in ways of X、Y, the number of structure mode of vibration、structure form and the test methods of natural frequency, the damage model of thewhole RAC framework was established. Base on the damage model, the damage indexof the structure in various conditions was calculated. Combining the preliminary division of the5degree of the damage grade of the RAC framework, the damage degreedivision of the comprehensive assessing the RAC framework was established.According the damage index of the RAC framework in various conditions and thecorresponding acceleration peak value, fitted the formula of quick-evaluated structuredamage for practical engineering. Finally, the model was simulated by ANSYS finiteelement software with7degrees multi-case、rare-case earthquake under X main input.Comparing the calculated results with experimental results, it could verify thecorrectness of such method with finite element, which could provide a new way fornonlinear analysis of RAC framework.The results shown that the preparation of recycled aggregate、ordinary RAC、EC-RAC in this text was effective and reliable.Meanwhile, the established mechanicalproperties and constitutive formulas were in good agreement with the experimentalresults. The seismic performance of beams、columns and frame structures was able tomeet the requirements of the 《Code for seismic design of buildings》(GB50011-2010)and other codes. Especially the incorporation of hybrid fiber can effectively enhance thecrack resistance and ductility of materials and components to improve the overallseismic performance of frame structure, and reduce the impact of the earthquakedisaster. Meanwhile the preparation techniques、constitutive relations、restoring forcemodel、the integrated evaluation criteria of structural damage, etc. can provide anecessary technical reference for the engineering application.