INTERNATIONAL CONFERENCE ON LIGHT WEIGHT CONSTRUCTION AND EARTHQUAKE | Year:2010 | دوره:0 |Papers Count:12

EACH IN THIS STUDY ELASTIC-PLASTIC IMPACT ON THICK RECTANGULAR PLATE WITH TWO OPPOSITE EDGES SIMPLY SUPPORTED UNDER IN-PLANE LOADS RESTING ON PASTERNAK ELASTIC FOUNDATION HAS BEEN CONSIDERED. THE OTHER EDGES OF PLATE CAN BE COMBINATIONS OF CLASSICAL BOUNDARY CONDITIONS SUCH AS FREE, SIMPLY SUPPORTED AND CLAMPED BOUNDARY CONDITIONS. DIMENSIONLESS EQUATIONS OF MOTION OF THE PLATE WERE OBTAINED BY APPLYING THE REISSNER-MINDLIN PLATE THEORY WHICH CONSIDERING THE FIRST-ORDER SHEAR DEFORMATION AND ROTATING INERTIA EFFECTS. FOR SOLVING GOVERNING EQUATION, THE EXACT CLOSED FORM SOLUTION WHICH IS PRESENTED BY HOSSEINI-HASHEMI [S. HOSSEINI-HASHEMI, K. KHORSHIDI, M. AMABILI, EXACT SOLUTION FOR LINEAR BUCKLING OF RECTANGULAR MINDLIN PLATES, JOURNAL OF SOUND AND VIBRATION 315 (2008) 318–342.] BECAUSE OF MORE ACCURATE RESPONSES AND LESS CALCULATING TIME IN COMPARISON WITH RAYLEIGH-RITZ METHOD HAS BEEN APPLIED. AFTER MAKING NUMERICAL VERIFICATION WITH THOSE AVAILABLE IN LITERATURE, EFFECTS OF DIMENSIONLESS PARAMETERS SUCH AS UNIAXIAL AND BIAXIAL IN-PLANE LOADS AND EFFECT OF FOUNDATION STIFFNESS PARAMETERS ON FORCE-HISTORY HAS BEEN SCRUTINIZED.

WRAPPING RC COLUMNS USING FIBER REINFORCED POLYMER (FRP) MATERIALS IS ONE OF THE RECENT METHODS OF STRENGTHENING, IN RC COLUMNS. MOST OF THE UNDERTAKEN STUDIES IN THE PAST WERE CONCENTRATED ON STUDYING FRP CONFINED RC COLUMNS SUBJECTED TO UNIAXIAL LOADING, HOWEVER, IN PRACTICE; THE COLUMN STRUCTURES USUALLY UNDERGO COMBINED AXIAL LOADING AND BENDING MOMENT. THIS PAPER REPRESENTS THE RESULTS OF NUMERICAL EVALUATION OF RETROFITTED RC COLUMNS SUBJECTED TO ECCENTRIC LOADING. ALSO AN INVESTIGATION ON PERFORMANCE OF DIFFERENT CONFINEMENT MODELS HAS BEEN CARRIED OUT AND THE RESULTS WERE COMPARED WITH THOSE EXISTING EXPERIMENTAL AND ANALYTICAL MODELS IN LITERATURE FOR VALIDATION OF PROPOSED ANALYSIS. IN EACH CASE, THE NUMERICAL MODEL HAS BEEN ANALYZED UNDER AXIAL LOADING AND DIFFERENT ECCENTRICITIES. THEN, THE SET OF BENDING MOMENT-AXIAL LOAD INTERACTION CURVES HAVE BEEN DRAWN. INVESTIGATION ON THE EFFECT OF COMPOSITE OVER WRAPPING ARCHITECTURE SUCH AS LAY UP STACKING SEQUENCES, NUMBER OF COMPOSITE PLIES AND ALSO COLUMN SLENDERNESS HAS BEEN CONSIDERED. ACCORDING TO THE OUT COMING RESULTS, USING A SYMMETRIC LAY UP COMBINED OF LONGITUDINAL AND TRANSVERSE FIBER DIRECTIONS, IS MORE APPROPRIATE FOR CONFINING A RC COLUMN SUBJECTED TO A CONCENTRIC AND ECCENTRIC LOADING. SUFFICIENT NUMBER OF LAYERS SHOULD BE USED TO OBTAIN WELL CONFINEMENT. IT IS OBSERVED THAT FRP EXTERNALLY BONDING IS LESS EFFECTIVE IN LONG COLUMNS THAN SHORT ONES.

IN THIS PAPER THE ABILITY OF PIEZOELECTRIC ACTUATOR MATERIALS TO ENHANCEMENT OF BUCKLING LOAD OF LONG SMART COMPOSITE COLUMN IS INVESTIGATED.THE THEORETICAL MODEL IS THREE LAYERS COMPOSITE BEAM MADE UP ONE LONG ELASTIC HOST CORE AND TWO SURFACE PIEZOCERAMICS PATCH WHICH ACT AS EXTENSIVE ACTUATION MECHANISM. THE FINITE ELEMENT MODELING OF SMART COMPOSITE COLUMN IS FOUND USING ANSYS® SOFTWARE. THE BUCKLING LOADS OF HOST AND SMART COMPOSITE COLUMN ARE CALCULATED. AT THE NEXT STAGE, FOR SMART COMPOSITE COLUMN, THE PIEZOELECTRIC PATCHES AT TOP AND BOTTOM ARE ACTIVATED BEFORE FIRST BUCKLING MODE OCCURS. THIS ACTION WILL DECREASE THE OUT OF PLANE DEFLECTION OR CHANGE THE BUCKLING MODE OF COLUMN FROM THE FIRST BUCKLING MODE TO HIGHER ONES THEREBY THE BUCKLING LOAD WILL INCREASE. THE ANALYSES ARE PERFORMED FOR SIMPLY- SIMPLE SUPPORTS.

IN THIS PAPER, BUCKLING LOAD OF SMART LIGHTWEIGHT COMPRESSIVE MEMBERS OF SPACE STRUCTURES IS INVESTIGATED. THE THEORETICAL MODEL IS THREE LAYERS COMPOSITE BEAM MADE UP ONE LONG ELASTIC CORE AND TWO SURFACE PIEZOCERAMICS PATCH WHICH ACT AS EXTENSIVE ACTUATION MECHANISM. THE FINITE ELEMENT MODELING OF SMART LIGHTWEIGHT COMPRESSIVE MEMBERS IS FOUND USING ANSYS® SOFTWARE. THEN, THE FIRST BUCKLING LOAD OF MEMBER IS CALCULATED BY BUCKLING ANALYSIS OPTION OF ANSYS® SOFTWARE. THE ANALYSES ARE PERFORMED WITH VARIATION IN GEOMETRICAL PARAMETER OF SIMPLY- SIMPLE SUPPORTED SMART COMPRESSIVE MEMBERS. REGARDING TO COMPLEXITY OF THIS PHENOMENON, EXISTENT MODELS ARE OFTEN INSUFFICIENT.NOWADAYS, ARTIFICIAL INTELLIGENCE SUCH AS ARTIFICIAL NEURAL NETWORK AND GENETIC PROGRAMMING ARE USED FOR MODELING THIS COMPLEX PHENOMENON. IN THE PRESENT STUDY, GENETIC PROGRAMMING (GP) WAS USED TO ESTIMATE THE BUCKLING LOAD OF SMART LIGHTWEIGHT COMPRESSIVE MEMBERS.

AN INNOVATIVE NON-EVACUATION RETROFITTING TECHNIQUE HAS BEEN DEVELOPED FOR REINFORCED CONCRETE BUILDING STRUCTURES, WHICH CONSTITUTE THE MAJOR PORTION OF THE EXISTING BUILDING STOCK IN TURKEY AND IN THE REGION. THE INTRODUCTION OF CAST-IN-PLACE REINFORCED CONCRETE INFILL WALLS, CONNECTED TO THE EXISTING FRAME MEMBERS, IS KNOWN TO BE VERY EFFECTIVE IN IMPROVING THE OVERALL SEISMIC STRUCTURAL PERFORMANCE. HOWEVER, THIS TECHNIQUE IS NOT SUITABLE FOR STRENGTHENING OF THE EXISTING BUILDING STOCK, SINCE IT INVOLVES MESSY CONSTRUCTION WORKS AND REQUIRES EVACUATION. THE IDEA BEHIND THE PROPOSED METHOD IS TO TRANSFORM THE EXISTING HOLLOW MASONRY INFILL WALLS INTO STRUCTURAL WALLS BY REINFORCING THEM WITH RELATIVELY HIGH STRENGTH PRECAST CONCRETE PANELS EPOXY GLUED TO THE WALL AND DOWEL CONNECTED TO THE FRAME MEMBERS IN ORDER TO ENHANCE THE LATERAL STIFFNESS OF THE FRAME. THE PANELS TO BE ASSEMBLED ON THE WALL ARE SMALL ENOUGH TO BE HANDLED BY TWO WORKERS. ALL SPECIMENS WERE TESTED TO FAILURE UNDER REVERSED CYCLIC QUASI-STATIC LATERAL LOADING RESEMBLING SEISMIC ACTION, BESIDES CONSTANT VERTICAL LOAD. APART FROM MINOR VARIATIONS IN BEHAVIOUR RESULTING FROM VARIOUS PARAMETERS STUDIED, ALL STRENGTHENED SPECIMENS EXHIBITED SUPERIOR PERFORMANCE COMPARED TO THE REFERENCE SPECIMENS WHICH WERE DESIGNED TO REPRESENT THE PRESENT STATE OF ORDINARY REINFORCED CONCRETE BUILDING FRAMES WITH HOLLOW BRICK INFILL WALLS PLASTERED ON BOTH SIDES.

ACCORDING TO RECENT EARTHQUAKES, NON-DUCTILE REINFORCED CONCRETE FRAMES SUFFER FROM EXCESSIVE DAMAGES AND CAUSE LOSS OF LIFE. CONCENTRIC BRACING SYSTEMS HAVE BEEN USED TO STRENGTHEN AND REHABILITATE WEAK RC STRUCTURES DURING PAST DECADE. IN THIS ARTICLE, THE SEISMIC BEHAVIOR OF AN ORDINARY MOMENT RESISTING RC FRAME STRENGTHENED WITH STEEL BRACES HAS BEEN INVESTIGATED. FOR THIS PURPOSE, NONLINEAR STATIC ANALYSIS (PUSHOVER) WAS CARRIED OUT ON THREE FRAMES WITH DIFFERENT HEIGHT, THREE, SIX AND NINE STORIES. SEISMIC BEHAVIOR FACTOR (R) OF PLAIN AND RETROFITTED FRAMES IS OBTAINED FROM PUSHOVER CURVE AND A COMPARISON HAS BEEN CARRIED OUT FOR DIFFERENT HEIGHT. IN ADDITION, ACCORDING TO BASE SHEAR-TOP DISPLACEMENT CURVE, DUCTILITY OF FRAMES IS DETERMINED.FINALLY, PERFORMANCE LEVELS OF FRAMES ARE OBTAINED USING THE CAPACITY SPECTRUM METHOD OF ATC-40. RESULTS SHOW THAT STRENGTHENING WITH STEEL BRACES CAN INCREASE THE PERFORMANCE POINT OF RC FRAMES.

NOWADAYS, THE APPLICATION OF COLD-FORMED STEEL MEMBERS IS WELL ESTABLISHED IN LIGHT STEEL FRAMING STRUCTURES AROUND THE WORLD. ONE OF THE METHODS TO BRACE THESES STRUCTURES AGAINST WIND AND EARTHQUAKE LOADS IS TO USE DIAGONAL STEEL STRAPS. THIS PAPER IS AIMED AT INVESTIGATING THE SEISMIC CHARACTERISTICS OF LIGHT STEEL FRAMING BRACED WITH STEEL STRAPS THROUGH ANALYSIS ON THE RESULTS OF CYCLIC TESTS. THE FRAMES SECTIONS USED IN THIS STUDY WERE C-SHAPED COLD-FORMED STEEL MEMBERS WITH THICKNESS OF 0.55 MM. THE DIFFERENCE BETWEEN DIFFERENT SPECIMENS RELIED ON THE CONNECTION DETAILS OF STEEL STRAP TO FRAME, NUMBER OF STUDS AND TYPE OF STRAP. AS A RESULT OF CYCLIC LATERAL LOAD, DIFFERENT FAILURE MODES WERE OBSERVED IN THE FRAMES MAINLY RESULTING FROM DIFFERENT CONNECTION DETAILS. IN SOME SPECIMENS, BRITTLE FAILURE MODE CAUSED A NOTABLE DECREASE IN THE DUCTILITY OF THE FRAME. IN THE CURRENT PAPER, BEHAVIOR FACTOR OF THE STRUCTURE WERE DETERMINED THROUGH A NUMERICAL EVALUATION.

IN THIS RESEARCH, ELECTROMECHANICAL FINITE ELEMENT MODELING OF UNSTIFFENED SMART STEEL SHEAR WALLS (SSSWS) IS INVESTIGATED USING ANSYS®. THE SSSWS ARE MADE OF AN ELASTIC HOST PLATE AND PIEZOELECTRIC ACTIVE LAYERS. THE PIEZOELECTRIC ACTIVE LAYER ACT AS EXTENSIVE OR SHEAR ACTUATION MECHANISM BASED ON THEIR POLING DIRECTION (EXCITANT PIEZOELECTRIC CONSTANTS IN PIEZOELECTRIC MATRIX) AND APPLIED ELECTRICAL FIELD. THESE PIEZOELECTRIC PIECES ARE USED PARALLEL TO THE DIAGONAL DIRECTION OF STEEL PLATE. IN OTHER WORDS, THE PIEZOELECTRIC SEGMENTS WILL BE PLACED PARALLEL TO THE TENSION FIELD OF PLATE WHICH WILL HAPPEN AFTER BUCKLING. THIS NEW COMBINATION CAN BE IMAGED AS COMBINATION OF SSWS WITH DIAGONAL PIEZOELECTRIC BRACES. LOAD BEARING CAPACITY OF PLATE WILL BE INCREASED WHEN AN ELECTRIC FIELD INTENSITY VECTOR IS APPLIED.

THE INTEGRITY OF THE STRUCTURE IS DIRECTLY AFFECTED BY THE DESIGN AND FABRICATION OF THE CONNECTIONS. IN THIS STUDY, A GROUTED TYPE OF THE PRECAST CONCRETE CONNECTION CONSISTS OF STEEL CONNECTION ONLY BEFORE GROUTING HAD BEEN PUT IN PLACE. THE ANALYSIS IS BASED ON NONLINEAR FINITE ELEMENT ANALYSIS (NLFEA) USING COSMOS/M. THE BEHAVIOUR OF THE CONNECTION IS OBSERVED TO PREDICT THE ULTIMATE STRENGTH AND TO DETERMINE ITS FAILURE MECHANISM. BOTH CONCRETE AND STEEL ARE MODELED AS SOLID ELEMENT. THE BEHAVIOUR OF THE CONNECTION SHOWS THAT THE CONNECTION UNDERGOES A LOCALIZED FAILURE SUCH AS CONCRETE CRACKING AND CRUSHING, AND POSSIBILITY OF YIELDING OF STEEL.

THIS ARTICLE IS INTENDED TO PROVIDE THE READER WITH PRELIMINARILY KNOWLEDGE ON SEISMIC MODELING OF CONCENTRICALLY BRACE FRAMES, CBFS. AS CBFS ARE ON OF THE MOST FREQUENTLY USED LATERAL LOAD RESISTING SYSTEMS IN IRAN AND SEVERAL DAMAGED AND COLLAPSED CASES ARE REPORTED IN PAST IRANIAN EARTHQUAKES, BETTER INSIGHT AND INFORMATION ON THEIR SEISMIC BEHAVIOR SEEMS TO BE A VITAL ENGINEERING CONCERN. A BRIEF INTRODUCTION ON SEISMIC FEATURES CONTRIBUTED TO BEHAVIOR OF DIFFERENT ELEMENTS IN CBFS IS PRESENTED. AFTER THAT, GENERAL MODELING TECHNIQUES FOR DIFFERENT ELEMENTS IN CBFS ARE DESCRIBED AND APPLIED IN MODELING OF TWO FULL SCALE BRACED FRAMES USING OPENSEES FRAMEWORK.

IN THIS RESEARCH THE LINEAR AND ELASTIC NONSTRUCTURAL DISPLACEMENTS ARE STUDIED UNDER NONLINEAR BEHAVIORS OF THEIR SUPPORTIVE STRUCTURES. IN THIS REGARD THE NONSTRUCTURAL COMPONENTS ARE INVESTIGATED IN TWO PHASES. IN THE FIRST ONE THE DYNAMIC INTERACTIONS BETWEEN STRUCTURES AND NON-STRUCTURES ARE IGNORED. IN THE SECOND PHASE THE EFFECTS OF DYNAMIC INTERACTIONS ARE CONSIDERED AND THE NANOSTRUCTURES OF DIFFERENT MASSES WITH THE SAME PERIODS OF SUPPORTIVE STRUCTURE'S MAIN MODE ARE LOCATED ON THE STRUCTURES' ROOFS. THEN, THE MAXIMUM RELATIVE DISPLACEMENTS ARE COMPARED IN TWO PHASES. FOR THIS PURPOSE, FOUR DIFFERENT MODELS OF 4, 8, 12 AND 16 STORIES ARE CONSTRUCTED DESIGNED IN THE FORMS OF ELASTIC AND RIGID BENDING FRAMES. THEN, AN ENSEMBLE OF THIRTY-TWO DIFFERENT GROUND MOTIONS, REPRESENTING HAZARD LEVELS OF 2, 10, AND 50% PROBABILITY OF EXCEEDANCE ARE USED AS INPUT TO THE BUILDING MODELS AND NONLINEAR DYNAMIC ANALYSIS CONDUCTED. IN THIS RESEARCH THE STRUCTURES AND NON-STRUCTURES PARAMETERS THAT AFFECT ON THE HEIGHT WISE DISTRIBUTION OF INTER-STORY DRIFT ARE INVESTIGATED.

AT THE PRESENT TIME, THE APPLICATION OF LIGHT STEEL FRAMING STRUCTURES HAS GROWN WIDELY AROUND THE WORLD, PRIMARILY BECAUSE OF THEIR HIGH CONSTRUCTION SPEED, QUALITY AND LIGHTNESS. ONE OF THE MAIN ADVANTAGES OF THESE STRUCTURES, PARTICULARLY IN HIGH SEISMIC REGIONS, IS LIGHTNESS THAT CAN CAUSE DECREASE IN EARTHQUAKE FORCE. IN THE CURRENT PAPER, A NUMERICAL ANALYSIS OF BEHAVIOR OF STUD INCLUDING COLD-FORMED STEEL FRAME UNDER THE AXIAL LOAD WAS PERFORMED USING ANSYS SOFTWARE. MOREOVER, THE EFFECTS OF DIFFERENT PARAMETERS SUCH AS STUD DIMENSIONS, MATERIAL CHARACTERISTICS, THICKNESS OF STUD MEMBERS AND BOLT SPACING WERE STUDIED AND THE OBTAINED RESULTS VERIFIED BY THE EXPERIMENTAL RESULTS IN THE LITERATURE.