Experimental Study On The Seismic Behavior Of RAC Modified Columns With The Difference Replacement Rate

The study and application of recycled concrete technology is not only can relievethe lack of resources but also well resolve the pollution brought by demolished concrete,as well it is of great importance to energy saving, reducing the pressure of livingenvironment and the ecological balance. However, there are still some imperfections ofrecycled aggregate concrete (RAC) in strength and density and some differencesbetween the recycled aggregate concrete and ordinary concrete, therefore, in order toenlarge the range of the application of recycled aggregate concrete practically, it isnecessary to study the mechanical property of recycled concrete and the seismicbehavior of RAC modified columns with the difference replacement rate.This text basing on the mechanical property and the performances of components ofupdated RAC, studies the seismic behavior of RAC modified columns, explores thepower failure mechanism and feature of RAC modified columns with distinct seismicforce, researches the dynamic property, such as the responsive acceleration, speedresponse, displacement response, frequency, damping and mode of vibration andevaluates the seismic behavior under the both conditions of frequent earthquake andrare earthquake, to provide certain basis for design approach of the seismic behavior ofRAC modified columns.I make the recycled aggregate out of the waste concrete and under the distinctreplacement rate, design a structural model with two spans, three stories, which used tostudy the seismic behavior with different replacement rate by using the change ofreplacement rate of every columns between different stories. Basing on what mentionedabove, the main work and research content of this text are as follows:(1)With the different replacement rate (ordinary concrete,30%,50%,70%, 100%), I design and make13pairs (39) of prism specimens. In this experiment, I studythe elasticity modulus and peak strain of prism specimens with different replacementrate, analyze the influence on the mechanical property of RAC, explore the pressedstrain curve and meanwhile put up with the ascent equation of RAC.(2) Basing on the frame structure model, a reinforced concrete structure with twospans, three stories is chose as the experimental model to analyze, which is made of C30RAC with the replacement rate of50%,(the height of1st floor is900mm, the2nd,900mm, and3rd,900mm). Through the model analysis of the pseudo-static test, I studythe energy consumption with the replacement rate of50%and according to the finalresult of the experiment, analyze the influential law of the hysteresis behavior withdistinct replacement rate and work out some valuable conclusions and recommend--ations.(3) Based on the constitutive model of the experiment, combining the researchresults, I reform the main parameters of RAC strain curve with different replacementrate by using ANSYS, according to which analyze the hysteretic behavior of both RACand ordinary concrete under the quasi static test and compare them putting up with thefeasibility of RAC.(4) I take one project as the prototype, design the model of the frame column testaccording to the proportion of1/4scale and operate the shaking table test, from which Istudy the natural frequency of vibration, acceleration, maximum displacement and thediscipline of the frame structure with the influence of seismic wave when the concretegrade is C30, the replacement rates of1stfloor column are30%,50%and70%, as wellin35gal,100gal and70gal condition, which provide data base for later research.Meanwhile, I compare the results with the requirement from Building StructureDesign Codes（GB50011-2010) and Technical Specification for Concrete Structures ofTall Building（JGJ3-2010), and work out the accurate first three order formation, naturalfrequency of vibration, acceleration envelop value and the maximal displacement value.(5) Taking the constitutive relation and parameters with different replacement rategiven by the article, I analyze the numerical simulation of the test frame structure modelby using ANSYS finite element, and under the effect of EL-Centro simulatedearthquake action, work out the frame structure formation contrast, acceleration and the maximal displacement. After the analysis, the constitutive model given by the article isproved to be reasonable and can be applied to the analysis of non-linear finite elementin frame structure.The results prove that with different replacement rate, the elastic modular ratio ofRAC and NC is less than one. While the replacement rate of RAC is30%,50%, and70%, its elastic modulus is less than NC about6.8%,22.4%and15.9%, however, whenthe replacement rate is100%, the elastic modulus is greater than3.64%, which affectsthe energy dissipation. As for ordinary concrete, the energy dissipation is better inquasi static load while the replacement rate is50%.The analysis and experiment results show that the natural frequency of vibration andthe first three order formation are similar to the ordinary concrete with differentreplacement rate; the frame structure of RAC has less safety with the effort ofearthquake because of the weak density, but with the rise of the earthquake magnitude,the reduce of seismic behavior is less and less, which is a valid approach to improve theenvironment and effective resources usage.