1. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Short Course for Earthquake Preparedness Recognizing Common Structural Hazards Feb10

2. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Earthquake – General Rules Earthquake shaking causes damage to structural load resisting system Then Gravity causes structural collapse The Heavier the building, the greater are the Forces Light, tough structures perform better Wood Bldg w/ plywood sheathing Small Metal Bldgs, w/ good connections The newer the better – lots of plywood wall sheathing Discontinuities in structures and the use of dis-similar materials are vulnerable to quake shaking Wood structures w/ 1 st story garages Brick Chimneys with wood houses Split level wood houses Use of brick and concrete finishes on wood bldgs

3. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Higher Risk Wood Structures Wood structures w/ 1 st story garages 3-story are worst, but 2-story also Wood houses w/ Brick Chimneys Split level wood houses Wood structures with brick veneer Taller are higher risk – falls on your head Wood structures w/ heavy tile roofing They are fire-resistant, but falling hazard

4. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. One or more Story can Collapse in Aftershock - M 5+ Elec Gas Water Heavy Roofg ? Balcony contents Racked walls ? plywood diag shtg stucco only stucco on gyp Broken glass Wood Apartments – Hazard Checklist

5. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Wood Apartments Over Conc Parking Over Weak 1 st Story Parking Higher Risk Moderate Risk

6. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Racked 2 story Apt Not as high risk as 3-story Rear Front

7. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. 4 Story Apt – High Risk Bldg has weak 1 st story & “Open Sides”- can offset

8. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. 3 Story Collapse Worst Case Weak 1 st story, older construction, and on poor soil

9. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Aftershock Collapse does happen 4 Story Buildings 1100hrs Sat, 21Oct 89 San Francisco 1105hrs Sat, 21Oct 89 San Francisco

10. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Split-level House Split-level House Collapse Hazard Initial condition Collapse projects weak story away roof & floor over weak garage are projected away chimney breaks at roof or fire box

11. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Split level, Collapsed on garage Racked Split Level House Damaged and ready to collapse

12. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Most likely Aftershock hazards = Falling heavy objects Cripple Wall TypeHi - Footing Racked cripple wall Separated Entry Roof Roof Tile falls off Gas & Water Masonry veneer falls off Elec Brick chimney cracked & may fall Wood House Hazard Checklist

13. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. 1 to 3 Story House w/ weak crawl space Most have been retrofit in CA – Banks require cripple wall Weak cripple wall racks and allows house to move as much as it’s height chimney can fall as far as it is tall discontinuous roof can be knocked off

14. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. House Cripple Wall Failure Most of these have been Retrofit

15. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Brick Chimneys are very Hazardous 1 story w/ code reqd ties 2-story is also Hazard to Adj.House

16. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Roof Tile Hazards Northridge Quake Hurricane Iniki

17. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Other Structures – Poor Performance Mobile Homes & Manufactured Units Unreinforced Masonry Walls - URM Most have been retrofit or replaced in CA due to Statewide Ordinance Critical issue is connection of walls to bldg Tilt-up Wall Buildings Many 1 and 2 story in SF Bay Area, inc Moffett Field Critical issue is connection of walls to bldg Some have been retrofit – no Ordinance Precast Parking Garages Poor performance in most of U.S. – better in CA.

18. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Mobile Homes & Manufactured Units Typical quake issue is connection at base On Jack stands About 2 ft off ground Vulnerable to racking & utility connection issues

19. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Fell off Jack Stands Racked at base Mobile Homes & Manufactured Units Typical quake issue at base

20. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. URM Building Hazard Checklist Most Hazards are Brittle & Lethal falling objects Elec Gas Water Slip off bearing Unsupported roof & floor URM corner Cracked wall piers Cracked parapets & split or peeled walls URM can fall 20 ft from bldg. face Loose equip

21. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Typical URM -“Wall Fall” Hazard Coalinga, CA 1984 San Francisco Loma Prieta 1989, 3 killed Most of these have been Retrofit

22. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. TU Buildings Hazard Checklist Cracked walls Leaning walls Separation of roof members from wall bearings Slip at all interior roof connections Wall top tension failure Aftershocks can cause added wall & roof collapse

23. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Wall Connection Failure Wall falls out, adjacent roof collapses Corner prevents collapse, Redundancy helps

24. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Elec Gas Cracked walls w/ broken conns Overload from upper collapse Loose debris Partly fallen slabs & beams Cracked corbels Beam collapse ? Leaning wall check conns Water Aftershocks cause loosely connected parts to shift & fall. Debris piles of large parts can shift & trap rescuers Precast Concrete Hazard Checklist

25. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Damaged in Whittier 87 EQ Collapsed in Aftershock May Co Garage

26. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Precast Armenia Apartments Parking Garages (Common in U.S.)

27. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Cast in Place Concrete Structures Are heavy, so potential hazard May be 1 to 30 stories Ones w/ concrete walls perform better Generally better in CA than other locals Weak concrete in Haiti, Iran, Pakistan, etc CA bldgs built prior to 1985 are higher risk

28. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. What about Concrete Shearwall Bldgs? They perform better than most, since they are cast in place

29. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. Concrete Shearwall Bldgs 12-story, Alaska EQ Good performance NASA Ames Lower Risk

30. Introduction to Earthquake Hazards in Common Structures Prepared by David J Hammond, Structural Engineer Ret. The Heavier the building, the greater the Forces Light, tough structures perform better Wood Bldg w/ plywood sheathing Small Metal Bldgs, w/ good connections The newer the better – lots of plywood wall sheathing Discontinuities in structures and the use of dis-similar materials are vulnerable to Quake. Wood structures w/ 1 st story garages Brick Chimneys with wood houses Split level wood houses Use of brick and concrete finishes on wood bldgs Key Learning Points