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Building Design and Construction Handbook - Merritt - Ventech!

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STRUCTURAL THEORY 5.173<br />

TABLE 5.15 Values of Site Coefficient F a as a Function of Site Class <strong>and</strong> Mapped<br />

Spectral Response Acceleration at Short Periods (S S)<br />

Site class<br />

Mapped spectral response acceleration at short periods<br />

S S � 0.25 S S � 0.50 S S � 0.75 S S � 1.00 S S � 1.25<br />

A 0.8 0.8 0.8 0.8 0.8<br />

B 1.0 1.0 1.0 1.0 1.0<br />

C 1.2 1.2 1.1 1.0 1.0<br />

D 1.6 1.4 1.2 1.1 1.0<br />

E 2.5 1.7 1.2 0.9 a<br />

F Note a Note a Note a Note a Note a<br />

a Site specific geotechnical investigation <strong>and</strong> dynamic site response analyses shall be performed to determine<br />

appropriate values.<br />

Note: Use straight-line interpolation for intermediate values of mapped spectral acceleration at short<br />

period, S S.<br />

TABLE 5.16 Values of Site Coefficient F v as a Function of Site Class <strong>and</strong> Mapped<br />

Spectral Response Acceleration at 1-Second Periods (S 1)<br />

Site class<br />

Mapped spectral response acceleration at 1-second period<br />

S 1 � 0.1 S 1 � 0.2 S 1 � 0.3 S 1 � 0.4 S 1 � 0.5<br />

A 0.8 0.8 0.8 0.8 0.8<br />

B 1.0 1.0 1.0 1.0 1.0<br />

C 1.7 1.6 1.5 1.4 1.3<br />

D 2.4 2.0 1.8 1.6 1.5<br />

E 3.5 3.2 2.8 2.4 a<br />

F Note a Note a Note a Note a Note a<br />

a Site specific geotechnical investigation <strong>and</strong> dynamic site response analyses shall be performed to determine<br />

appropriate values.<br />

Note: Use straight-line interpolation for intermediate values of mapped spectral acceleration at 1second<br />

period, S 1.<br />

Site Specific Procedures for Determining <strong>Design</strong> Spectral Response Accelerations<br />

• A site specific study shall account for the regional seismicity <strong>and</strong> geology; the<br />

expected recurrence rates <strong>and</strong> maximum magnitudes of events on known faults<br />

<strong>and</strong> source zones; the location of the site with respect to these; near source effects,<br />

if any; <strong>and</strong> the characteristics of subsurface site conditions.<br />

• The probabilistic maximum considered earthquake ground motion shall be taken<br />

as that motion represented by an acceleration response spectrum having a 2%<br />

probability of exceedance within a 50-year period. The probabilistic maximum<br />

considered earthquake spectral response acceleration at any period, S aM, shall be<br />

taken from the 2% probability of exceedance within a 50-year period spectrum<br />

(where S aM exceeds the deterministic limit shown in Fig. 5.114.)

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