what’s new in asce 7-16? - · pdf filewind asce 7-10 v asce 7-16 • except in...
TRANSCRIPT
10/30/2017
1
www.sgh.com
What’s New In ASCE 7-16?
Ronald O. Hamburger SE, SECBSenior Principal
Simpson Gumpertz & Heger Inc.
Presented to:TMS
San Diego, CANov. 4 2017
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
10/30/2017
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 1Performance
Goals
10/30/2017
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)
Table 1.3-1– Target Reliability other than Seismic, Tsunami or Extraordinary Events
Reliability Goals – Load other than Seismic
10/30/2017
4
Reliability Goals & Performance
Table 1.3-2– Target Reliability for Structural Instability Caused by Earthquake
Table 1.3-3– Target Reliability for Noncritical Member Failures Caused by Earthquake
Reliability Goals Seismic
10/30/2017
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
• 10 – 15 mph reduction across non-hurricane prone regions
– Snow
10
10/30/2017
6
Wind Maps
11
• ASCE 7-10 • ASCE 7-16
Snow Maps
10/30/2017
7
Snow Maps
Chapter 6Tsunami
10/30/2017
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
10/30/2017
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
10/30/2017
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 12Seismic
10/30/2017
11
Classical Design Response Spectrum
T
Sa(T)
TL10.2
SDS
SD1
SD1/T
SD1TL/(T)2
��� � 23� ���
�� � 23� ���
Where hazard is controlled by large-magnitude earthquakes, and site soils
are soft, the standard spectral shape is not appropriate
• Site specific site response analysis required where:
– Site Class E and SS > 1.0
– Site Class D or E S1 > 0.2g
Response Spectrum Rules
T
Sa(T)
TL10.2
SDS
SD1
SD1/T
SD1TL/(T)2
T
Sa(T)
TL10.2
SDS
SD1
SD1/T
SD1TL/(T)2
10/30/2017
12
Response Spectrum Rules
• Exceptions
– Site Class E,
• Site Class “C” Fa is used
– Site Class D,
• � ����
� �⁄� for values of T< 1.5Ts
• Cs factored by 1.5 for T>1.5TS
• 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
10/30/2017
13
Chapters 26-30Wind
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
10/30/2017
14
High Altitude Wind Reduction
27
Reno, Tahoe, Denver, Santa Fe
Flat Roof Pressures
2010 2016
10/30/2017
15
Appendix EFire 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
10/30/2017
16
On-lineHazard Tool
On-line Hazard Tool
• Replaces USGS and ATC Seismic and Wind Hazard
applets
• Input:
– Lattitude
– Longitude
– Site Class
• Output:
– Seismic: SS SMS, SDS, S1, SM1, SD1 + response spectra
– Ground Snow Load
– Basic Wind Speed
– Atmospheric Icing Thickness
10/30/2017
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!