SEISMIC REHABILITATION BY SYSTEM IMPROVEMENT (METU APPROACH) Presentation atUniversity of Texas and Purdue University November 2008 UĞUR ERSOY Bogazici University, Civil Engineering Dept. Istanbul - Turkey

ONE OF THE MAJOR EARTHQUAKES IN ISTANBUL WAS IN 1715 ACCORDING TO SOLAKZADE (HISTORIAN WHO EXPERIENCED THE 1715 EARTHQUAKE) PEOPLE GOT KILLED A GREAT MAJORITY OF THE BUILDINGS WERE DESTROYED 109 MOSQUES AND 30 CHURCHES EITHER COLLAPSED OR SUFFERED HEAVY DAMAGE A PORTION OF THE CITY WALLS COLLAPSED, WAVES WENT OVER THE CITY WALLS

MAJOR CAUSES of SEISMIC DAMAGE TO RC BUILDINGS MISTAKES MADE IN CHOOSING THE BUILDING CONFIGURATION (ARCHITECTURAL AND/OR STRUCTURAL SYSTEM) INADEQUATE REINFORCEMENT DETAILING AND DETAILING ERRORS MISTAKES MADE AT THE CONSTRUCTION STAGE (INADEQUATE INSPECTION) SOIL PROBLEMS

SEISMIC REHABILITATION MEMBER REHABILITATION (Column, Beam Jacketing, Wrapping with CFRP Sheets, etc.) SYSTEM IMPROVEMENT

IN THIS TECHNIQUE, THE EXISTING LATERAL LOAD RESISTING SYSTEM IS REPLACED BY A NEW LATERAL LOAD RESISTING SYSTEM CONSISTING OF RIGID VERTICAL MEMBERS.

CASES IN WHICH SYSTEM IMPROVEMENT BECOMES FEASIBLE WHEN THE LATERAL STIFFNESS OF THE FRAME SYSTEM IS INADEQUATE WHEN TOO MANY MEMBERS NEED TO BE REHABILITATED WHEN THE FRAME SYSTEM HAS INHERITED WEAKNESSES SUCH AS SOFT STORY, SHORT COLUMNS, ETC.

MOST COMMONLY USED SYSTEM IMPROVEMENT TECHNIQUE IN TURKEY IS “REINFORCED CONCRETE INFILLED FRAME TECHNIQUE”. IN THIS TECHNIQUE: SELECTED BAYS OF THE FRAME SYSTEM IN EACH DIRECTION ARE FILLED WITH CAST IN PLACE REINFORCED CONCRETE WALLS PROPERLY CONNECTED TO FRAME ELEMENTS BY INSERTED DOWELS

RC INFILL FOUNDATION SECTION A-A

RESEARCH AT METU ON RC INFILLED FRAMES (1969 – 2000)

METU INFILLED FRAME TESTS THREE BAY DEFICIENT, DAMAGED FRAME, 1999

INFILL WAS INTRODUCED TO DAMAGED FRAME. NO REPAIR WAS MADE DEGREE OF DAMAGE IN THE FRAME: COLUMN LONGITUDINAL BARS YIELDED INFILLED FRAME BEHAVED WELL 90 – 95 % OF LATERAL LOAD WAS RESISTED BY THE WALL

RC INFILLED FRAME TECHNIQUE HUNDREDS OF BUILDINGS HAVE BEEN REHABILITATED USING THIS TECHNIQUE AFTER THE FOLLOWING EARTHQUAKES: 1969 Bartın 1992Erzincan 1995Dinar 1998Ceyhan 1999Marmara 1999Düzce

THE GREAT TRUTHS OF ENGINEERING ARE SIMPLE... AN ENDLESSLY COMPLEX PRESENTATION OF AN ENGINEERING FACT INDICATES COMPLICATION IN THE BRAIN OF THE PROPOUNDER RATHER THAN COMPLEXITY OF NATURE. Hardy Cross

METU RECOMMENDATIONS FOR RC INFILLED FRAMES MINIMUM INFILLED WALL AREA: IN EACH DIRECTION,  A w >=  A pi >=0.01 A pt  A w - SUMMATION OF CROSS SECTIONAL AREA OF INFILLS  A pi – SUMMATION OF PLAN AREAS OF ALL FLOORS A pt - FLOOR AREA OF THE BUILDING AT THE BASE IN CASE OF WEAKNESSES SUCH AS SOFT STORY, SHORT COLUMNS, INCREASE THE CONSTANT FROM TO

DOWELS CONNECTING THE INFILL TO FRAME MEMBERS TOTAL CROSS-SECTIONAL AREA OF DOWELS IN THAT DIRECTION SHOULD NOT BE LESS THAN THE WALL REINFORCEMENT IN THAT DIRECTION: A dx >=  A sx A dy >=  A sy AT FOUNDATION LEVEL, A dy >= 1.5  A sy ANCHORAGE OF DOWELS: L d >= 35 BAR DIAMETER (INFILL) >= 15 BAR DIAMETER (FRAME MEMBERS, EPOXY)

SHEAR CAPACITY V r <= f ct (A c ) f ct = TENSILE STRENGTH OF CONCRETE A c = SHEAR AREA = txL = SHADED GRAY AREA

METU APPROACH

Building Model ANALYSİS FILTER DECISION

“RC INFILLED FRAME TECHNIQUE” IS PROVED TO BE, ECONOMICAL, PRACTICAL AND SAFE BY TESTS AND NUMEROUS APPLICATIONS AFTER THE EARTHQUAKES DRAWBACK : THE BUILDING HAS TO BE EVACUATED

“RC INFILLED FRAME TECHNIQUE” WILL NOT BE FEASIBLE TO REHABILITATE THOUSANDS OF EXISTING BUILDINGS, SINCE IT WILL NOT BE PRACTICAL TO EVACUATE THEM!

YEAR 2000, RESEARCHERS AT METU WERE SEARCHING FOR A NEW REHABILITATION TECHNIQUE WHICH WILL NOT REQUIRE EVACUATION AND WILL GIVE MINIMUM DISTURBANCE TO THE OCCUPANTS DURING APPLICATION

SOLUTION, TO STRENGTHEN THE EXISTING NON- STRUCTURAL INFILLS AND PARTITION WALLS WHICH WOULD BEHAVE AS STRUCTURAL WALLS

STRENGHTHENING OF EXISTIMG NON- STRUCTURAL INFILLS BY, CFRP SHEETS PRECAST PANELS WHICH WILL BE CONNECTED TO THE FRAME MEMBERS

METU RESEARCH PROJECTS ( ) Financed by: TUBITAK (Turkish Science Foundation) NATO BUDGET ≈ $ 1.5 Million

Other Contributers: TURKEY: Kocaeli and Boğaziçi Universities and ITU FOREIGN USA (University of Texas), Greece and Republic of Macedonia

SP – 6, SP – 7

TEST SETUP

TEST RESULTS

PC PANELS

LOADING SYSTEM

ENVELOPE CURVES

Relative to masonryRelative to infilled frame bare frame Lateral load capacity  2.5 times  15 times Lateral stiffness  3 times  20 times Ductility  2 times  0.2 times PERFORMANCE IMPROVEMENT

SHAKE TABLE TESTS INSTITUTE OF EARTHQUAKE ENGINEERING AND ENGINEERING SEISMOLOGY, SKOPJE, MACEDONIA

SEISMIC REHABILITATION REQUIRES A SOUND BEHAVIOR KNOWLEDGE REHABILITATION MADE WITH LIMITED KNOWLEDGE AND EXPERIENCE CAN MAKE THE STRUCTURE MORE VULNERABLE

THE ENGINEER IS FACED WITH MANY UNKNOWNS IN THE ANALYSIS OF AN EXISTING BUILDING PRIOR TO AND AFTER REHABILITATION. THEREFORE IN MODELING THE STRUCTURE THE ENGINEER HAS TO MAKE NUMEROUS ASSUMPTIONS SUCH AS, MATERIAL STRENGTHS, FLEXURAL RIGIDITY (EI), etc.

DUE TO THESE ASSUMPTIONS, THE NUMBERS WHICH COME OUT AS A RESULT OF THE ANALYSIS ARE BY NO MEANS EXACT OR NEARLY EXACT. THESE NUMBERS, ALTHOUGH NOT EXACT, SERVE AS A GUIDELINE FOR THE ENGINEER IN MAKING JUDGEMENTS AND DECISIONS.

HISTORY OF SCIENCE IS FULL OF BEAUTIFUL THEORIES, BUTCHERED BY SMALL UGLY FACTS ! Sir S. Thomas