| China is one of the countries that are most affected by the earthquake.Since Wenchuan earthquake happened,we have put more emphasis on requirements for fortification against earthquake of buildings and structures dramatically.In typical steel braced frame structures,braces are easy to lose bearing capacity because of out-of-plane instability when they are bearing larger compressive load,so traditional steel braced frame structures usually cannot reflect their strength of materials or live up to our expectations.With the improvement and popularization about technique of seismic energy dissipation,buckling-restrained braces(BRBs)have come into sight on visions of scholars and been put into use on construction projects.Professor Zhou of Guangzhou University raised a point that reducing brace sections of core parts is equal to reinforce the rest of parts,which becomes a spotlight on study of buckling-restrained braces.This new kind of BRB has lower yield point after reducing its core-part sections by slotting or trepanning,therefore,this new-type BRB has advantages on designated yield location and protecting each side of end region.In this article,software ABAQUS is used to execute a finite element simulation about unidirectional loading and low-cycle cyclic loading of a typical cruciform-section brace,a BRB with cruciform section,a BRB with single-row trepanning cruciform section and a BRB with double-row trepanning cruciform section.The results indicate that the bearing capacity and rigidity of typical cruciform-section declines dramatically when compressive displacement is increasing.BRB with double-row trepanning cruciform section has the lowest yield load among three BRB models,and the bearing capacity on twenty millimeters is only 1.4 percent less than BRB with cruciform section,as well as the dimension of hysteresis loop is only no more 3 percent than BRB with cruciform section.To sum up,it performs gorgeous mechanical properties and energy dissipation capabilities.Meanwhile software ABAQUS is used to establish a transverse piece of steel-frame structure,the steel frame with typical cruciform-section brace,the steel frame reinforced by BRBs with single-row trepanning cruciform section and the steel frame reinforced by BRBs with double-row trepanning cruciform section models,and execute the finite element simulation about unidirectional loading and low-cycle cyclic loading testing of above four sets of models.The results illustrate that the bearing capacities of the frame structures which are reinforced with BRBs perform well mechanical properties especially in rigidity and ultimate bearing capacities in stark contrast to the pure steel-frame structure.The steel frame reinforced by BRBs with double-row trepanning cruciform section performs well ultimate bearing capacities and hysteretic behavior,also has merits of designated yield location and reducing stress of end region according to the von Mises colored stress patterns.The software Midas/Gen is utilized to set up a five-storey-steel-frame structure,the steel frame reinforced by typical cruciform-section braces and the steel frame reinforced by BRBs with double-row trepanning cruciform section models to analyze their elastic properties under frequent earthquake actions and their elastoplastic properties under rare occurrence earthquake actions.The results show that the steel frame reinforced by BRBs with double-row trepanning cruciform section has lower interlayer displacement angle,roof displacement,roof acceleration compared with the steel frame reinforced by typical cruciform-section braces when structures is in elastic-plastic phase,which performs gorgeous anti-seismic properties.The hysteresis loops of lower-storey BRBs are fully symmetric.The BRB with double-row trepanning cruciform section has lower yield load and means yielding much earlier than major structure,which performs excellent anti-seismic properties to protect major structure and components safely. |
PDF Full Text Request