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)
•10000 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 DAMAGEMAJOR CAUSES of SEISMIC DAMAGE TO RC BUILDINGSTO 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 REHABILITATIONSEISMIC REHABILITATION
•MEMBER REHABILITATION(Column, Beam Jacketing,
Wrapping with CFRP Sheets, etc.)
•SYSTEM IMPROVEMENT
SYSTEM IMPROVEMENTSYSTEM 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 CASES IN WHICH SYSTEM IMPROVEMENT BECOMES IMPROVEMENT BECOMES FEASIBLEFEASIBLE•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
RESEARCH AT METU ON RESEARCH AT METU ON RC RC INFILLED FRAMES (1969 – 2000)INFILLED FRAMES (1969 – 2000)
• 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 TECHNIQUERC INFILLED FRAME TECHNIQUE•HUNDREDS OF BUILDINGS HAVE BEEN REHABILITATED USING THIS TECHNIQUE AFTER THE FOLLOWING EARTHQUAKES:
•1969 Bartın•1992 Erzincan•1995 Dinar•1998 Ceyhan•1999 Marmara•1999 Düzce
THE GREAT THE GREAT TRUTHS OF TRUTHS OF ENGINEERING ARE SIMPLE...ENGINEERING ARE SIMPLE...AN ENDLESSLY COMPLEX AN ENDLESSLY COMPLEX PRESENTATION OF AN PRESENTATION OF AN ENGINEERING FACT INDICATES ENGINEERING FACT INDICATES COMPLICATION IN THE BRAIN COMPLICATION IN THE BRAIN OF THE PROPOUNDER RATHER OF THE PROPOUNDER RATHER THAN COMPLEXITY OF THAN COMPLEXITY OF NATURE. NATURE.
Hardy CrossHardy Cross
METU RECOMMENDATIONS FOR METU RECOMMENDATIONS FOR RC INFILLED FRAMESRC INFILLED FRAMESMINIMUM INFILLED WALL AREA:IN EACH DIRECTION, Aw >=0.0025 Api
>=0.01 Apt
Aw - SUMMATION OF CROSS SECTIONAL AREA OF INFILLS Api – SUMMATION OF PLAN AREAS OF ALL FLOORS Apt - FLOOR AREA OF THE BUILDING AT THE BASE
IN CASE OF WEAKNESSES SUCH AS SOFT STORY, SHORT COLUMNS, INCREASE THE CONSTANT FROM 0.0025 TO 0.003.
DOWELS CONNECTING THE INFILL DOWELS CONNECTING THE INFILL TO FRAME MEMBERSTO FRAME MEMBERS
TOTAL CROSS-SECTIONAL AREA OF DOWELS IN THAT DIRECTION SHOULD NOT BE LESS THAN THE WALL REINFORCEMENT IN THAT DIRECTION: Adx >= Asx Ady >= Asy
AT FOUNDATION LEVEL, Ady >= 1.5 Asy
ANCHORAGE OF DOWELS: Ld >= 35 BAR DIAMETER (INFILL) >= 15 BAR DIAMETER (FRAME MEMBERS, EPOXY)
SHEAR CAPACITYSHEAR CAPACITY
Vr <= fct (Ac)
fct = TENSILE STRENGTH OF CONCRETE Ac = SHEAR AREA = txL = SHADED GRAY AREA
“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,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,SOLUTION,
TO STRENGTHEN THE EXISTING NON-STRUCTURAL INFILLS AND PARTITION WALLS WHICH WOULD BEHAVE AS STRUCTURAL WALLS
STRENGHTHENING OF EXISTIMG STRENGHTHENING OF EXISTIMG NON-STRUCTURAL INFILLS BY,NON-STRUCTURAL INFILLS BY,
•CFRP SHEETS •PRECAST PANELS
WHICH WILL BE CONNECTED TO THE FRAME MEMBERS
METU RESEARCH PROJECTS METU RESEARCH PROJECTS (2001-2006)(2001-2006)
Financed by: •TUBITAK (Turkish Science Foundation)
•NATO BUDGET ≈ $ 1.5 Million
Other Contributers: •TURKEY:
Kocaeli and Boğaziçi Universities and ITU
•FOREIGNUSA (University of Texas),
Greece and Republic of Macedonia
3/50
3/55
4
4
3/50 3/50
4
3
3
4
4
4
4
245
320
745
105
20
Type 1 panel
Type 2 panel
10
All dimensions are in mm.
PC PANELSPC PANELS
Cross Beam
Prestressing Cable
Universal Base
Foundation Beam
Load CellRam
Pins
RamStrong Wall
Spreader Beams
LOADING SYSTEMLOADING SYSTEM
-250
-200
-150
-100
-50
0
50
100
150
200
250
-50 -40 -30 -20 -10 0 10 20 30 40 50
Top Displacement (mm)
Lat
eral
Loa
d (
kN
)
CR CIACIB CICCID CIC3CIC4 CEE1CEF CEECEER LRLIC LID
ENVELOPE CURVESENVELOPE CURVES
Relative to masonry Relative toinfilled frame bare frame
Lateral load capacity 2.5 times 15 times
Lateral stiffness 3 times 20 times
Ductility 2 times 0.2 times
PERFORMANCE IMPROVEMENTPERFORMANCE IMPROVEMENT
SHAKE TABLE TESTSSHAKE 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.