Daños estructurales y tipos de fallas observadas en …Purpose!...

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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