Updates on Ground Motion and Geotechnical Data Requirements in the 2013 CBC Jorge F. Meneses, PhD, PE, GE, D.GE, F.ASCE Carlsbad, California consulting engineers and scientists AEG Inland Empire Chapter Continuing Education Series May 31, 2014

Overview Design earthquakes Maximum direction Risk-targeted General procedure Examples Geotechnical Requirements Summary Outline

Building Code Cycle 2012 NEHRP 2009ASCE 7-10IBC 2012 (Effective January 1, 2014)

Source, Path and Site

Evaluating Seismic Hazard and Ground Motions

Some definitions Definitions –Hazard: a phenomenon that has the potential to cause damage –Risk: the probability that damage will occur In general, it is accepted that Earthquake Hazard cannot be avoided Hence, the philosophy behind building codes is to “mitigate risk” –We can’t avoid earthquakes, so we will build structures that can withstand earthquakes Key concept: acceptable risk

MCE R The most severe earthquake effects considered by ASCE 7-10 determined for the orientation that results in the largest maximum response to horizontal ground motions and with adjustment for targeted risk (ASCE 7-10, Chapter 11, p.60) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE R ) GROUND MOTION RESPONSE ACCELERATION

MCE G The most severe earthquake effects considered by ASCE 7-10 determined for geometric mean peak ground acceleration and without adjustment for targeted risk The MCE G PGA adjusted for site effects (PGA M ) is used for evaluation of liquefaction, lateral spreading, seismic settlements, and other soil related issues. MAXIMUM CONSIDERED EARTHQUAKE GEOMETRIC MEAN (MCE G ) PEAK GROUND ACCELERATION (ASCE 7-10, Chapter 11, p.60)

Orientation of Maximum Response (Max. direction)

Maximum direction

Geomean and maximum S a (Whittaker et al 2009)

Landers, Joshua Tree

Loma Prieta, LGPC

DUZCE, BOLU

Directivity Effects on Ground Motions

Comparison of various models S aRotD100 /S aRotD50 (Shahi and Baker 2013)

Ground motion values contoured on maps incorporate factors to adjust from a geometric mean to the maximum response regardless of direction These factors are 1.1 for 0.2 second spectral response acceleration (S S ) and 1.3 for 1.0 second spectral response acceleration (S 1 ) Maximum Response (ASCE 7-10, Figures 22-1 through 22-6)

General procedure Use mapped values and tables from code USGS Seismic design maps web application

Seismic Ground Motion Values (ASCE 7-10, Chapter 11, p.65-66)

S S, S 1 Fa, Fv S MS, S M1 S DS, S D1 Site Class B

Site Classification (ASCE 7-10, Chapter 20, p.204)

Site Coefficient F a Site class Mapped risk-targeted MCE R S a at short second S s ≤ 0.25S s = 0.50S s = 0.75S s = 1.0S s ≥ 1.25 A0.8 B1.0 C D E FSite-specific study required (Chapter 11, p.66)

Site Coefficient F v Site class Mapped risk-targeted MCE R S a at 1 second S 1 ≤ 0.1S 1 = 0.2S 1 = 0.3S 1 = 0.4S 1 ≥ 0.5 A0.8 B1.0 C D E FSite-specific study required (Chapter 11, p.66)

S DS = 2/3*S MS = S D1 =2/3*S M1 =0.454 S S1S1 S M1 =F v *S 1 T o =0.10T S =0.48 S a = S DS ( T/T o ) PGA = 0.4 S DS = S DS /2.5 PGA = 0.378g SAN DIEGO SITE SITE CLASS C (F a = 1.0, F v = 1.3) Period (seconds) Spectral Acceleration (g) MCE R Site Class B MCE R Site Class C DE = 2/3 MCE R 5 percent damping S a = S D1 /T T o = 0.2 S D1 /S DS T s = S D1 /S DS *F a = S MS

Risk Category of Buildings Use or occupancy of buildings and structuresRisk category Buildings and other structures that represent a low risk to human life in the event of failure I All buildings and other structures except those listed in Risk Categories I, III, and IV II Buildings and other structures, the failure of which could pose a substantial risk to human life III Buildings and other structures designated as essential facilities. Buildings and other structures, the failure of which could pose a substantial hazard to the community IV (Chapter 1, p.2)

Seismic Design Category based on S 1 Value of S DS Risk category I or II or IIIIV S 1 ≥ 0.75EF S 1 < 0.75See following tables (Chapter 11, p. 67)

Seismic Design Category based on S DS Value of S DS Risk category I or II or IIIIV S DS < 0.167AA ≤ S DS < 0.33BC 0.33 ≤ S DS < 0.50CD 0.50 ≤ S DS DD (Chapter 11, p. 67)

Seismic Design Category based on S D1 Value of S DS1 Risk category I or II or IIIIV S D1 < 0.067AA ≤ S D1 < 0.133BC ≤ S D1 < 0.20CD 0.20 ≤ S D1 DD (Chapter 11, p. 67)

Seismic design category D through F For liquefaction studies PGA M = F PGA PGA PGA M = MCE G PGA adjusted for site effects PGA = Mapped MCE G PGAs F PGA = Site coefficients (see table) (ASCE 7-10, Section , p.68-69)

Site coefficient F PGA Site class Mapped MCE G PGA PGA ≤ 0.1PGA = 0.2PGA = 0.3PGA = 0.4PGA ≥ 0.5 A0.8 B1.0 C D E FSite-specific study required (ASCE 7-10, Chapter 11, p.68)

Location of three selected sites Rose Canyon- Newport-Inglewood Fault Zone Coronado Bank Fault Zone San Diego Trough Fault Zone

Comparison of design response spectra

Site 2

Site 3

Site 2

Site Class E? Watch out!

Site Class E?

Site Class E? S M1 > S MS !

Comparison of S DS (Luco 2009)

Comparison of S D1

S DS – Southern California (OSHPD 2012)

S DS – Northern California

Maxima and Minima Values for California Maxima S s = 3.73 g S 1 = 1.28 g Minima S s = g S 1 = g S DS = 0.22 g S D1 = 0.17 g

Seismic design category D through F For seismic lateral earth pressures: The determination of dynamic seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet (1.83m) of backfill height due to design earthquake ground motions (2013 CBC, Section 1803A.5.12, p. 177)

Seismic design category D through F An assessment of potential consequences of liquefaction and soil strength loss, including, but not limited to: -Estimation of total and differential settlement -Lateral soil movement -Lateral soil loads on foundations -Reduction in foundation soil-bearing capacity and lateral soil reaction -Soil downdrag and reduction in axial and lateral soil reaction for pile foundations -Increases in soil lateral pressures on retaining walls (2013 CBC, Section 1803A.5.12, p. 177)

Seismic design category D through F Discussion of mitigation measures such as, but not limited to: -Selection of appropriate foundation type and depths -Selection of appropriate structural systems to accommodate anticipated displacements and forces -Ground stabilization -Any combination of these measures and how they shall be considered in the design of the structure (2013 CBC, Section 1803A.5.12, p. 177)

Geotechnical Peer Review (DSA-SS and DSA-SS/CC) When alternate foundations designs or ground improvements are employed or where slope stabilization is required, a qualified peer review by a California-licensed geotechnical engineer, in accordance with Section 3422, may be required by the enforcement agency. In Section 3422, where reference is made to structural or seismic-resisting system, it shall be replaced with geotechnical, foundation, or ground improvement, as appropriate. (2013 CBC, Section 1803A.8, p. 178)

Retaining Walls – Design lateral soil loads Retaining walls shall be designed for the lateral loads determined by a geotechnical investigation in accordance with Section 1803A and shall not be less than eighty percent of the lateral soil loads determined in accordance with Section 1610A. (2013 CBC, Section 1803A.8, p. 178)

Table 1610A.1 Lateral Soil Load (2013 CBC, Section 11610A, p. 87)

Contact Jorge F. Meneses, PhD, PE, GE, D.GE, F.ASCE (760) For further information