FLEXURE BASED ENERGY DISSIPATING DEVICE IN SELF-CENTERING BRACES

Abstract

SELF–CENTERING BRACES, IN THE CURRENT STAGE OF DEVELOPMENT CAN ACCOMMODATE LARGE DEFORMATION AND FORCE LEVELS. HOWEVER, THERE IS STILL A NEED FOR IMPROVEMENT OF THE ENERGY DISSIPATION MECHANISMS COMMONLY INCORPORATED IN THESE BRACES. YIELD BASED ENERGY DISSIPATION SYSTEMS CAN OVERCOME SOME OF THE PROBLEMS FACED WITH FRICTION-BASED DEVICES, SUCH AS SUSCEPTIBILITY TO BOLT RELAXATION, LONG-TERM CREEP OF FRICTION MATERIAL AND EXCESSIVE FLEXING ARISING IN THE OUTER TUBES DUE TO FRICTION BOLTS. HOWEVER, IN THESE ALTERNATIVE SYSTEMS MULTI-WAVE BUCKLING OF THE YIELDING CORE IS PRESENT, WHICH IS THE LEADING CAUSE OF AN ASYMMETRIC HYSTERESIS OF THE BRACE. HENCE, IN THIS STUDY, U-SHAPE FLEXURAL PLATES (UFPS) ARE ANALYZED AS AN ALTERNATIVE ENERGY-DISSIPATING DEVICE IN REAL SCALE SELF-CENTERING BRACES WITH A FINITE ELEMENT MODELING APPROACH. UFP PLATES YIELD IN FLEXURE AND WHEN COMPARING TO DIRECT TENSION/COMPRESSION YIELDING MEMBERS, THEY SHOW LOWER STRAIN DEMAND, RESULTING IN A LARGER DISPLACEMENT CAPACITY. IMPLEMENTATION OF THE UFP UNITS IN THE BRACE PRODUCES A FLAG SHAPE HYSTERESIS WITH MINIMAL RESIDUAL DEFORMATION. THE PROPOSED SYSTEM PROVIDES SOME ADVANTAGES WHEN COMPARED TO PREVIOUS MODELS IN TERMS OF INCREASED REDUNDANCY, SYMMETRIC HYSTERESIS AND A MORE GRADUAL STIFFNESS CHANGE.