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Building Codes

Building Codes. Building Codes. 1927- First UBC required, fire safety updated every 3 years recognition of new weaknesses in designs Save lives and reduce injuries Lateral forces Ductility Drift Acceleration Ground response. Hazard Map: expected accelerations. Originally by zones 0-4

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Building Codes

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  1. Building Codes

  2. Building Codes • 1927- First UBC required, fire safety • updated every 3 years • recognition of new weaknesses in designs • Save lives and reduce injuries • Lateral forces • Ductility • Drift • Acceleration • Ground response

  3. Hazard Map: expected accelerations

  4. Originally by zones 0-4 California uses these zones 4 uses the highest values for seismic safety What is wrong with this map (Seattle)? Uniform Building Code Zone Map (1988)

  5. Seismic Zone Maps: change with new information Seattle and Portland area are now in zone 4

  6. Building codes: collapse prevention

  7. Federal Funding • NEHRP: National Earthquakes Hazards Reduction Program • Helps develop building codes • 1997, 2000, 2003 National Science Foundation National Institute of Standards and Technology

  8. Summary of California Building Codes 1927 First Uniform Building Code (UBC) issued, primarily about fire safety.1935 UBC requires foundation bolting and reinforcement of masonry foundations.1946 UBC requires some reinforcement of masonry chimneys.1961 UBC requires all structural members to resist earthquake forces.1973 UBC requires bracing of cripple walls. 1976 UBC requires 50% increase in earthquake design forces for box-type structures and stronger force loads for hospitals and concrete-moment frame buildings1988 UBC adds a new soil profile type for considering site resonance for tall or long-period structures.1991 UBC increases bracing requirements for cripple walls and requires bracing of water heaters.1997 UBC requires testing of steel welds and increased design forces for concrete tilt-up wall anchorage. Heavy plate washers required for foundation anchor bolts.

  9. Building Codes • Earthquake in India • builder-politician link, many buildings illegally built • Recognition of weaker structures • Lack of reinforcement • Notice collapse of first story

  10. Armenian Earthquake • December 7, 1988 • M 6.9 • 11:41 A.M. • 70 % of buildings destroyed • >100,000 people killed Building codes not followed or enforced

  11. Building Codes • Most efficient tool for mitigating earthquake losses • Funding is currently focused on improving structural designs

  12. Federal Funds • Cornell University • 2.1 million dollars • Simulate earthquakes • Building and infrastructure response The lab allows scientists to use powerful hydraulic presses and a 20-foot-tall wall of concrete to produce shearing forces that would exceed even the strongest recorded earthquake.

  13. One million pound ½ scale precast concrete parking garage Simulated earthquakes expected in different regions 2.3 million project Change building codes Testing: UCSD

  14. 1933 Long Beach Earthquake • Building response • Un-reinforced masonry • Field Act • Seismic Element Code (F=CW) • First acceleration records • Expertise and classification of “structural engineer” developed

  15. Earthquake Codes • F=CW • F = force • C = constant depending on building material, earth material, and number of building stories • W = weight of building • Recognition of lateral forces

  16. A framed wall extending from the top of the foundation to the underside of the floor framing of the first story above grade Cripple Wall

  17. 1973: bracing for cripple walls 1991: increased bracing with the addition of shear walls Cripple Walls

  18. Uniform Building Code • 1935- Foundation bolting

  19. 1935: bolt house to foundation 1997: washers required with expansion bolts 4-6 feet apart Bolting House to Foundation

  20. 1991: strapping to studs in wall Water Heaters

  21. Uniform Building Code • 1991-Bracing of water heaters

  22. Uniform Building Codes • recognition how earth materials influence seismic waves

  23. Uniform Building Code • 1935- reinforcement of masonry foundations • 1986- Unreinforced Masonry retrofit law • 1993- how retrofitting is done

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