What s New In ASCE 7-16?

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Emily Holt
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com The Big Changes Title Change Chapter 1 Performance Goals Service & Function Reliability Targets Updated Hazard

1 What s New In ASCE 7-16? Ronald O. Hamburger SE, SECB Senior Principal Simpson Gumpertz & Heger Inc. Presented to: TMS San Diego, CA Nov The Big Changes Title Change Chapter 1 Performance Goals Service & Function Reliability Targets Updated Hazard Maps New Chapter on Tsunami Loads New Appendix on Fire Effects Complete Revision of Seismic Response History Analysis Procedures New Seismic Site Class Coefficients New Cladding Wind Pressure Coefficients 1

2 Title Change (also 2 Volumes) Minimum Design Loads and Associated Criteria for Buildings and Other Structures Hazard levels Intended Performance Goals Seismic detailing Protection against wind borne debris Chapter 1 Performance Goals 2

1.3.3 Functionality Risk category IV structures and systems designed to provide reasonable probability of functionality given any of the design level hazards (ice, flood, rain, seismic, snow,

3 1.3.3 Functionality Risk category IV structures and systems designed to provide reasonable probability of functionality given any of the design level hazards (ice, flood, rain, seismic, snow, tsunami, wind) Affects: Outdoor generators Radio communications towers Roof-mounted HVAC (if necessary for function) Reliability Goals Load other than Seismic Table Target Reliability other than Seismic, Tsunami or Extraordinary Events 3

3-2 Target Reliability for Structural Instability

4 Reliability Goals & Performance Reliability Goals Seismic Table Target Reliability for Structural Instability Caused by Earthquake Table Target Reliability for Noncritical Member Failures Caused by Earthquake 4

5 Updated Hazard Maps Impact on ASCE 7-16 New hazard maps for: Atmospheric Icing ¼ to ½ increase in susceptible areas Moderate increase in geographic coverage Seismic +/- 10% changes many places +/- 20% a few places Wind mph reduction across non-hurricane prone regions Snow 10 5

6 Wind Maps ASCE 7-10 ASCE Snow Maps 6

7 Snow Maps Chapter 6 Tsunami 7

8 Scope Risk Category III & IV Structures within the Tsunami Design Zone Other structures designated by building official Tsunamic Design Zone Based on 2,475 year tsunami run-up hazard Digital maps for: Alaska, California, Hawaii, Oregon, Washington Tsunami Design Zone 8

forces Buoyancy Waterborne debris impact Load Case 1 Maximum inundation depth + buoyancy Load Case

9 Tsunami Design Procedure Based on Tsunami Amplitude, shoreline distance, ground elevation and friction, determine: Flood elevation Flood velocity Design Evaluations Design for: Hydrodynamic forces Buoyancy Waterborne debris impact Load Case 1 Maximum inundation depth + buoyancy Load Case 2 2/3 Maximum inundation depth Maximum velocity Load Case 3 Maximum inundation depth 1/3 maximum velocity 9

II or III buildings Collapse Prevention Risk Category

10 Evaluation Approach Linear static or nonlinear static procedure ASCE 41 Acceptance Criteria Risk Category II or III buildings Collapse Prevention Risk Category IV buildings Immediate Occupancy Chapter 12 Seismic 10

Classical Design Response Spectrum S a (T) S DS S D1 S D1 /T S D1 T L /(T) 2 0.

11 Classical Design Response Spectrum S a (T) S DS S D1 S D1 /T S D1 T L /(T) T L T Where hazard is controlled by large-magnitude earthquakes, and site soils are soft, the standard spectral shape is not appropriate Response Spectrum Rules S a (T) S DS S D1 S D1 /T S a (T) S DS S D1 S D1 /T S D1 T L /(T) 2 S D1 T L /(T) T L T T L T Site specific site response analysis required where: Site Class E and S S > 1.0 Site Class D or E S 1 > 0.2g 11

Response Spectrum Rules Exceptions Site Class E, Site Class C Fa is used Site Class D, for values

5T S Scaling of Response Spectrum Results Forces scaled to 100% of ELF Base Shear Response History

Must perform linear analysis first Ground Motions Uniform Hazard or Conditional Mean Spectrum 11

12 Response Spectrum Rules Exceptions Site Class E, Site Class C Fa is used Site Class D, for values of T< 1.5T s Cs factored by 1.5 for T>1.5T S Scaling of Response Spectrum Results Forces scaled to 100% of ELF Base Shear Response History Analysis Linear procedure moved to Chapter 12 Completely rewritten nonlinear procedure (Chapter 16) Must perform linear analysis first Ground Motions Uniform Hazard or Conditional Mean Spectrum 11 motions minimum Global Evaluation Unacceptable Runs Transient Drift Residual Drift Component Evaluations Reliability-based with load and resistance factors 24 12

13 Chapters Wind ASCE 7-10 v ASCE 7-16 Except in hurricane areas, wind speeds have reduced by about 10% More weather stations available now Increased forestation & urbanization Reliabilities of old maps not right At high altitude locations wind pressures can be reduced considering the reduced density altitude 13

14 High Altitude Wind Reduction Reno, Tahoe, Denver, Santa Fe 27 Flat Roof Pressures

requirements of building code, or Performance-based

15 Appendix E Fire Effects Appendix Fire Effects All structures comply with applicable fire protection requirements of building code, or Performance-based approach Design fire scenarios Structural stability Egress 15

16 On-line Hazard Tool On-line Hazard Tool Replaces USGS and ATC Seismic and Wind Hazard applets Input: Lattitude Longitude Site Class Output: Seismic: S S S MS, S DS, S 1, S M1, S D1 + response spectra Ground Snow Load Basic Wind Speed Atmospheric Icing Thickness 16

17 Summary Significant changes in wind and seismic design Enhanced recognition of performance-based procedures First ever adoption of Tsunami criteria Web-based Hazard Lookup Is now available for purchase Is referenced in IBC 2018 Thank you! 17

Project 17 Development of Next-Generation Seismic Design Value Maps

Project 17 Development of Next-Generation Seismic Design Value Maps Geo Structures 2016 16 February 2016 R.O. Hamburger, SE, SECB www.sgh.com Some History Prior to 1988 - maps provided broad seismic zones