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

RC INFILL

FOUNDATION

SECTION A-A

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

METU INFILLED FRAME TESTSMETU 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 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

METU APPROACHMETU 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,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 

SP – 6, SP – 7SP – 6, SP – 7

TEST SETUPTEST SETUP

TEST RESULTSTEST RESULTS

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.

HISTORY OF SCIENCE IS FULL OF BEAUTIFUL THEORIES, BUTCHERED BY SMALL UGLY FACTS !  

Sir S. Thomas