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PROF. JAMES O. JIRSA James O. Jirsa holds the Janet S. Cockrell Centennial Chair in Engineering at the University of Texas at Aus?n. He has engineering degrees from the Universi?es of Nebraska and Illinois and was on the faculty at Nebraska and Rice University before joining UT Aus?n in 1972. He served as director of the Ferguson Structural Engineering Lab and as Chairman of the Department of Civil Engineering at UT. He is a member of the Na?onal Academy of Engineering and served as Chair of Sec?on 4—Civil Engineering. He is an Honorary Member and Past-‐President of the American Concrete Ins?tute. He served on the ACI Board of Direc?on and was chairman of the ACI Technical Ac?vi?es CommiUee. He is a member of ACI CommiUee 318 Standard Building Code. He is an Honorary Member of the Earthquake Engineering Research Ins?tute and served on the Board of Directors. Other memberships include the Interna?onal Associa?on of Bridge and Structural Engineering, Interna?onal Federa?on of Concrete, Structural Engineers Associa?on of Texas. His teaching and research interests are in the areas of behavior and design of reinforced concrete structures with special emphasis on rehabilita?on of exis?ng structures in seismic zones, durability of structures in corrosive environments, and detailing of reinforcement in structures.
IMPACT OF THE 1985 EARTHQUAKE ON
STRUCTURAL REHABILITATION IN THE US AND MEXICO
James O. Jirsa
University of Texas at Aus?n
CONMEMORATIVO SIMPOSIO XXX ANIVERSARIO DE LOS SISMOS DE SEPTIEMBRE DE 1985
1966 RILEM Simposio Organized by
RILEM and
Ins?tuto de Ingenieria UNAM
Hotel Con?nental Hilton
September 15-‐17, 1966
Purpose RILEM Permanent CommiUee in Moscow 1964
• “to cover problems related to the – behavior of materials, structural members and structures,
– under abrupt, infrequent and transient loading, including impact and nonlinear vibra?on processes
– involving large amplitudes, which can cause heavy damage..”
• Low-‐cycle fa?gue
Par?cipants • Engineers from all over the world who were or became leaders in earthquake engineering
• Many events to introduce par?cipants to Mexican culture, history, and food
• We watched the parade from the Hotel Con?nental and could see the mountains looking down Reforma
• Occurred during Independence Day celebra?ons—Dr. Emilio Rosenblueth carried the flag and led El Grito
• Special thanks to Juan Casillas
Pre-‐1985
• Some research on rehabilita?on underway in US
• No evalua?on or rehabilita?on guidelines were available
• Most rehabilita?on work in the US was being done by a few firms in California
Important Events
• Most code changes triggered by earthquake events
• Damage or failure of hospitals and schools raises public demands for ac?on
• Experience for other countries important but building inventory may be different
Damage to Schools
1968 Tokachi-‐oki
Hakodate University
Misawa High School
1933 Long Beach
Field Act for school safety
Damage to Hospitals
Veterans Administration
Olive View
1983 Nihonkai-chubu 1971 San Fernando
Policy Ac?ons
• 1974 Applied Technology Council started work on ATC-‐3 “Tenta&ve Provisions for the Development of Seismic Regula&ons for Buildings” –published in 1978
• 1977 US Congress passed the Na&onal Earthquake Hazards Reduc&on Act (NEHRP). – “to reduce the risks of life and property from future earthquakes in the United States”
NEHRP Agencies
• Federal Emergency Management Agency (FEMA)
• Na?onal Ins?tute of Standards and Technology (NIST) Lead agency
• Na?onal Science Founda?on (NSF) • United States Geological Survey (USGS)
Research Ac?vi?es
• NEHRP agencies and US/Japan Coopera?ve Program in Natural Resources (UJNR) began mee?ngs in early 1970’s on wind and seismic effects
• 1978 Japan passed Large-‐Scale Earthquake Countermeasures Act and built new facili?es at Tsukuba Science City – First large scale test—7-‐story RC structure (1984)
Tsukuba Science City
Building Research Ins?tute
Public Works Research Ins?tute
Na?onal Science Founda?on
• Funding for rehabilita?on research in early 1980’s
• Project University of Texas in collabora?on with H J Degenkolb Associates of San Francisco
• Transfer of findings to prac?ce was needed
2/3 Scale, 2 Story RC Frame
Office Building Retrofit UC Berkeley
Concrete Infill Walls
Mexico September 19, 1985 • Many casual?es
• Destroyed vital buildings—hospitals, government offices
• Vulnerable building types – Medium-‐rise buildings – Light columns, thin floors – Poor column and joint details
Widespread damage to modern
construc?on
• Waffle slab systems
• Upper floors • Pounding • Column failures • Reinforcement
details • Infill walls
Column Failures
Joint Failures
Detailing
DAMAGE STATISTICS
0
20
40
60
80
100
120
No. of Buildings
RCFrames
SteelFrames
WaffleSlabs
Bldgsw/Shear
walls
Masonry
SevereCollapse
Damage/Height of Buildings
0
20
40
60
80
100
120
No. of Buildings
<5 6 to 10 11 to 15 >15No. of Stories
SevereCollapse
Reconnaissance Teams • By 1985, NEHRP had increased awareness of earthquake risks in the US
• Damage and loss of life in Mexico City was a ?mely reminder of what could happen in a large US city
• Many US researchers and engineers visited Mexico City to see the impact of a seismic event on a city similar to many in the US
• Team from University of Texas toured damage area
Rehabilita?on • US NSF and Mexican CONACYT quickly made funding available for further study of the damage and the rehabilita?on
• Many different rehabilita?on techniques were implemented
• Rehabilita?on had to sa?sfy updated requirements of the Mexico City Building Code.
• Experimental data was badly needed to support the designs, however, the work could not wait for research results.
March 1989 Workshop • NSF/CONACYT Collabora?on • Organized by Universidad Autonoma Metropolitana (Prof. Jesus Iglesias)
• Site visits to buildings under rehab • Frank, extensive discussions with engineers in charge
• Review of codes and guidelines used • Need to document rehab work done
Jesus Iglesias Oscar Gonzalez Cuevas Francisco Robles Salvador Durate Manuel Jara
Jorge Aguilar
Designers/Researchers Mexico US
• Julio Damy • Oscar de la Torre • Carlos Tapia • Enrique del Valle • Victor Pavon • Jose Luis Sanchez Mar?nez • Jose Maria Rioboo • Max Tenenbaum • Enrique Mar?nez Romero • Eduardo Rukos • Horacio Ramirez • Roberto Meli
• Gary Hart • William Holmes • Chris Poland • Larry Reaveley • Thomas Sabol • Nabih Youssef • James Jirsa • Michael Kreger • Stephen Mahin • James Wight • Ugo Morelli
Beam and Column Jacke?ng
New Bracing Systems
New Walls
Mixed Systems
Reinforcement Details
Cable Bracing
Removal of Top Stories
Founda?on Rehab
website: hUps://fsel.engr.utexas.edu/publica?ons/detail.cfm?pubid=708093600
Contents
• Overview of damage • Mexico City codes and requirements • General descrip?on of rehab techniques • 12 Case studies
Case Studies
• Building descripton • Descrip?on of damage aper 1985 Eq. • Temporary measures (if needed) • Strengthening procedures • Construc?on procedures (as available)
Types of Rehabilita?on A. Beam and column jacke?ng B. Diagonal steel bracing, founda?on rehab C. Removal of top floors, column strengthening D. Cable bracing E. Addi?on of new RC frames F. New RC walls G. New RC infill walls H. New walls and column jackets in lower floors I. New walls at ends and addi?onal piles J. Steel bracing interior bays K. K-‐bracing L. New walls lower floors, X-‐braces upper floors
Remarks on Experience • Opportunity to study impact of regula?ons and ordinances on rehabilita?on approaches
• Wide variety of rehab types observed • Open exchanges between engineers and researchers
• Very sa?sfying professional experience with long-‐las?ng friendships
• Similar efforts should follow future events wherever they occur
Rehabilita?on—State of the Art 1985
• Changes in seismic design codes triggered by important seismic events
• Deficiencies evident aper damage studied • In Mexico City, rehabilita?on projects had to meet the same code requirements as new construc?on.
• In the US, there were no special requirements for rehabilita?on in 1985 but work was underway to provide guidelines for evalua?on and rehabilita?on of exis?ng buildings.
Mexico City • 1942 Code published aper 1941 earthquake
– First Code to include seismic design • 1957 Emergency Norms published aper July earthquake
– Sop, transi?on and hill zones iden?fied – Seismic coefficients based on importance and type
• 1966 Code very similar to 1957 Norms • 1976 Complementary Technical Norm for most common materials
– Detailing requirements – Seismic Coefficients modified by duc?lity factor
• 1985 Emergency Norms published aper 1985 – 60% of collapsed or damaged buildings were built between 1957 and 1976, 17% aper 1976
• 1987 Code – Seismic forces same for new or exis?ng buildings
USA • No na?onal code—Local building codes based on model code (in 1985—Uniform Building Code
• Now called Interna?onal Building Code (IBC) – Reference to ACI or AISC or ASCE documents
• No documents covering evalua?on or rehabilita?on
• Most rehabilita?on work done by California firms using “engineering judgement”
US Seismic Codes since 1985 • Building Seismic Safety Council (BSSC) established in 1979 under contract with FEMA – NEHRP Recommended Seismic Provisions for New Buildings and Other Structures
– primary resource for the design standard ASCE/SEI 7 Minimum Design Loads for Buildings and Other Structures
• Provisions for different materials developed by technical socie?es – such as, ACI, AISC, TMS
Rehabilita?on and Evalua?on • FEMA 154 Rapid Visual Screening of Buildings for Poten&al Seismic Hazards: (1998), 3rd Edi?on (2015)
• FEMA 273 & 274 NEHRP Guidelines for the Seismic Rehabilita&on of Exis&ng Buildings: (1997)
• FEMA 356 Prestandard and Commentary for the Seismic Rehabilita&on of Buildings: (2000)
• FEMA 310 Handbook for the Seismic Evalua&on of Buildings—A Prestandard: (1998)
• FEMA 172(1992), FEMA 547 (2007Techniques for the Seismic Rehabilita&on of Exis&ng Buildings:)
ASCE 31
FEMA 310
FEMA 356
ASCE 41
• Following the 1985 earthquake, students from Mexico came to US for graduate study and on the joint NSF/IMCYC program
• University of Texas project on rehabilita?on of beam-‐column joints (Sergio Alcocer)
Research on Seismic Rehabilita?on
Current Status of Research on Rehabilita?on in US
• Network for Earthquake Engineering Simula?on (NEES) in 1994-‐1014 funded by NSF
• Research on seismic issues is no longer a “hot” topic in the US
• Many vulnerable buildings but no impetus for rehabilita?on of infrastructure – hospital rehabilita?on is decades behind schedule and funding for replacement hospitals inadequate
• Challenging life extension issues remain to be solved.
The Future
• Policy and funding changes needed – 1986 California Unreinforced Masonry Building Law
• Use of “new” materials • Reduce cost of construc?on • Realis?c modeling and analysis procedures needed for evalua?on and retrofit projects
2015 Technical Seminar Series: Update on Vulnerable Concrete Buildings
• Efforts to improve our ability to iden?fy the most vulnerable buildings
• Updates to the processes and documents used to evaluate the risks posed by these buildings
• Ongoing community level efforts to reduce hazards through public educa?on, policy and legisla?on.
7-‐story RC Frame/Shear Wall building Building Research Ins?tute, Tsukuba, Japan
Roof Displacement
B
ase
Shea
r
Pushover Response—Prior to Test
TEST
Side View
ΔM
Na?onal Research Ins?tute for Earth Science and Disaster
Preven?on (NIED) Hyogo -‐ Japan (near Kobe)
Two 4-‐story buildings with shear
walls in one direc?on and frame
in other
Reinforced Concrete Walls
Post-‐Tensioned Walls
Japan E-‐Defense Shake Table Test
Test vs Pushover Analysis
50% 30%
ACI Structural Journal: March-‐April 2015 Vol. 112 No. 2
• One could conclude that we have not made much progress in 30 years!
• ATC-‐114 Development of Accurate Models and Efficient Simula&on Capabili&es for Collapse Analysis to Support Implementa&on of Performance Based Seismic Engineering
• Much remains to be learned
Concluding Remarks • My career has been deeply fulfilling and enriched by many colleagues who have shared the desire to reduce earthquake risks
• We have many important issues that need to be solved.
• The next big earthquake will teach us some of the same old lessons and confound us with new ones.
Gracias de nuevo por haberme invitado a par?cipar en este simposio Le deseo éxito en el tratamiento de estas cues?ones y la minimización de los efectos de los terremotos en los que dependen de nuestro trabajo. Buenas noches
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