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Structural Concrete - Hassoun

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894 Chapter 22 Prestressed <strong>Concrete</strong> Bridge Design<br />

police, fire, and rescue vehicles to homes, businesses, and industrial plants [2]. Such classification<br />

should be based on social/survival and/or security/defense requirements [1].<br />

For the strength limit state:<br />

η I ≥ 1.05 for important bridges<br />

= 1.00 for typical bridges<br />

≥ 0.95 for relatively less important bridges<br />

For all other limit states:<br />

η I = 1.00<br />

22.4.2 Load and Load Designation (AASHTO 3.3.2)<br />

In AASHTO LRFD bridge design specifications, loads are classified as permanent and transient.<br />

The following permanent and transient loads and forces are used in Tables 22.8 and 22.9 for the<br />

load combinations and corresponding factors:<br />

Permanent Loads<br />

DD Downdrag<br />

DC Dead load of structural components and nonstructural attachment<br />

DW Dead load of wearing surfaces and utilities<br />

EH Horizontal earth pressure load<br />

EL Accumulated locked-in force effects resulting from the construction<br />

process, including the secondary forces from posttensioning<br />

ES Earth surcharge load<br />

EV Vertical pressure from dead load of earth fill<br />

Transient Loads<br />

BR Vehicular braking force<br />

CE Vehicular centrifugal force<br />

CR Creep<br />

CT Vehicular collision force<br />

CV Vessel collision force<br />

EQ Earthquake<br />

FR Friction<br />

IC Ice load<br />

IM Vehicular dynamic load allowance<br />

LL Vehicular live load<br />

LS Live-load surcharge<br />

PL Pedestrian live load<br />

SE Settlement<br />

SH Shrinkage<br />

TG Temperature gradient<br />

TU Uniform temperature<br />

WA Water load and stream pressure<br />

WL Wind on live load<br />

WS Wind on structure<br />

22.4.3 Load Combinations and Load Factors (AASHTO 3.4.1.1)<br />

The load factors for various load combinations and permanent loads are given by AASHTO<br />

and reproduced in Table 22.8 and Table 22.9, respectively. Note that both a maximum and a

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