Study On Energy Dissipation Performance Of A New Type Of Pure Steel Buckling-restrained Braces

Compared with the traditional brace,buckling restrained brace can achieve the yield point without buckling under axial compression or tension.Its well hysteretic energy dissipation performance and stability of mechanical properties are more and more popular with the engineers.In addition,easy installation,economy,flexible construction design,and without affection on aesthetics of the main structure make the buckling restrained brace to be not only one of the first choice of new building aseismic design,but also an important means of aseismic reinforcement and transformation to the buildings which have been built.In this paper,I develop a new type of pure steel buckling restrained brace,which is economic with using the ingot iron and Q235 B as the inner core plate.Combining with pseudo static test and finite element numerical simulation,I have conducted a preliminary research about the energy consumption performance of the new buckling restrained brace.The main researches are as follows:First of all,on the basis of existed theory and references,as regards the overall stability,local buckling stability of inner core,the local stability and local bending bearing capacity of the external constrains and torsion bearing capacity of the connection segment,I have conducted the design and calculation about the specimen.As for the details of new buckling restrained brace,it is designed in two ways: mechanics and geometry.Second,taking advantage of the ABAQUS software to make finite element modeling of new buckling restrained brace,I have conducted detailed analysis about parameters which have impacts on the energy consumption of the new buckling restrained brace to verify the reliability and accuracy of the existing theory.These parameters cover: the initial bending flaw of inner core,the friction coefficient between inner core and external constraint unit,the clearance between inner core and external constraint unit,the width-to-thickness ratio of the inner core,the buckling restrained ration,and the thickness of external constraint unit.Then,according to the pseudo-static test results of the new type buckling restrained brace specimen,I have made a study of the hysteretic energy dissipation on the condition that the inner core plates are made up with different material,the external constraints units constitute different angle iron,or the inner core plates have different width-to-thickness ratios.The results of the pseudo-static tests show that,compared with the series of specimen whose inner core plate is made up with Q235 B,the inner core plate made up with ingot iron manifests that the hysteresis curve is plump but not stable,fatigue performance is well,as well as the ductility.Using two different angle irons as external constraint unit of the specimen,the relevant mechanical parameters and energy performance evaluation indicators are basically identical,on the same conditions.The specimens whose width-to-thickness value of the inner core plate is 8 emerge that the hysteretic curve is relatively plump,the maximum stress of the inner core plate is smaller,and the local stability of inner core is better,compared with the specimens whose width-to-thickness value of inner core plate is 10.Finally,based on ABAQUS finite element simulation to the new type of pure steel buckling restrained brace,the finite element simulation results are consistent with the experimental results,with regard to the relevant mechanical parameters,energy consumption evaluation index,and the hysteresis curve.Due to the material characteristic test of ingot iron,its mechanical performance is not stable.Regarding the results of the material characteristic test of ingot iron as the constitutive parameters,the finite element simulation results such as yield strength are slightly different with the experimental results.