Presentation on theme: "A. T. Tankut Middle East Technical University, Turkey"— Presentation transcript:
1 A. T. Tankut Middle East Technical University, Turkey 68th SOEAA, Florianapolis, Brazil SEISMIC REHABILITATION OF RC STRUCTURES- AN OVERVIEWA. T. TankutMiddle East Technical University, Turkey
2 A NOTE ON THE CONTENTSInitial intention was to discuss the philosophy behind seismic strengthening under the title “Seismic Rehab Strategy”Considering the audience consisting of various disciplines, policy was changed.Basic concepts and methods that may interest the audience will be reviewed.
3 OUTLINE Introduction and Basic Concepts Common Structural Systems Rehabilitation Techniques AvailableAn Innovative Rehabilitation Technique
5 INTRODUCTION “Earthquake” is a natural phenomenon It is tolerable in countries where the people and the built environment are prepared for it;It leads to a disaster in countries where the built environment and the people are not prepared for it.
6 INTRODUCTION “Earthquake Preparedness” consists of Disaster Management (post-quake) – Search & rescue, sheltering, food, medical care etc. (Easy but not effective)Risk Management (pre-quake) – Safe towns, safe structures, well educated public, well trained engineers, effective financing etc. (Hard but very effective)
7 INTRODUCTIONSeismic rehab of the existing bldg stock is the most critical item in risk mitigation.A huge unsafe building stock exists.A systematic assessment reveals that- A small number is seismically safe,- A certain portion is to be demolished,- The majority is to be strengthened.
9 COMMON TYPE OF STRReinforced concrete framed building structures are common in southeast Europe including Turkey.Partitioning walls of hollow brick masonry make the structure infilled frame and changes its behaviour.
10 COMMON DEFICIENCIESOf these RC framed building structures with hollow brick masonry infill,* Low-rise (12 floor) are not vulnerable;* High-rise (> 1012 floor) buildings are carefully designed and constructed;* Mid-rise (38floor) bldgs of inferior material, poor design and construction quality present the major problem.
11 COMMON DEFICIENCIES Mid-rise buildings of inferior quality Constitute the majority in small towns;Collapse in the pancake mode; thusAre responsible from the high number of human losses and severe damage,Are generally too good for demolition;Are greatly in need of rehabilitation.
12 COMMON DEFICIENCIES Common deficiencies of such buildings: Insufficient lateral stiffnessDeficient reinforcement detailingDeficient design practicePoor concretepoor workmanship etc.
20 SYSTEM IMPROVEMENT Devices reducing seismic loads Base isolation Active / passive controlSmart structuresDampersEnergy absorbers etc.
21 SYSTEM IMPROVEMENT Lateral stiffness increasing elements Cast-in-place reinf conc infilled framesMasonry infills, reinforced with high strength precast concrete panelsSteel cross bracingPost tensioningExternal rigid frame to support the str
23 INTRODUCTION The basic question: Cast-in-place reif conc infilled frame technique is suitable for post-quake repair of the evacuated buildings; but not for pre-quake rehabilitation of the buildings still in use.Suitable techniques should be developed.
24 THE CHALLENGE To develop a rehabilitation method, Suitable for the common building type (Hollow brick infilled RC frame)Practical & economical, and above allOccupant friendly (no more disturbance than an ordinary painting job)
25 THE ANSWER The answer is OFR (occupant friendly rehab) To reinforce existing masonry infill wall with epoxy bonded PC panels, which are,- Light enough to be handled by two- Small enough to go through doors- Relatively thin, 40~50 mm (high str)- Connected to infill wall by epoxy, andto frame by epoxy bonded dowels
35 CONCLUSIONPC panel technique is a very effective and practical seismic rehabilitation method for existing buildings.Leads to a significant improvement in seismic performanceIs easily applied to buildings in use with minimal disturbanceIs cost effective (Comparable to cast-in-place RC infills)