Task Order DTFH61-02-T-63032 4-1 Design Step 4 DECK SLAB DESIGN Design Step 4.1 In addition to de... more Task Order DTFH61-02-T-63032 4-1 Design Step 4 DECK SLAB DESIGN Design Step 4.1 In addition to designing the deck for dead and live loads at the strength limit state, the AASHTO-LRFD specifications require checking the deck for vehicular collision with the railing system at the extreme event limit state. The resistance factor at the extreme event limit state is taken as 1.0. This signifies that, at this level of loading, damage to the structural components is allowed and the goal is to prevent the collapse of any structural components. The AASHTO-LRFD Specifications include two methods of deck design. The first method is called the approximate method of deck design (S4.6.2.1) and is typically referred to as the equivalent strip method. The second is called the Empirical Design Method (S9.7.2). The equivalent strip method is based on the following: • A transverse strip of the deck is assumed to support the truck axle loads. • The strip is assumed to be supported on rigid supports at the center of the girders. The width of the strip for different load effects is determined using the equations in S4.6.2.1. • The truck axle loads are moved laterally to produce the moment envelopes. Multiple presence factors and the dynamic load allowance are included. The total moment is divided by the strip distribution width to determine the live load per unit width. • The loads transmitted to the bridge deck during vehicular collision with the railing system are determined. • Design factored moments are then determined using the appropriate load factors for different limit states. • The reinforcement is designed to resist the applied loads using conventional principles of reinforced concrete design. • Shear and fatigue of the reinforcement need not be investigated. The Empirical Design Method is based on laboratory testing of deck slabs. This testing indicates that the loads on the deck are transmitted to the supporting components mainly through arching action in the deck, not through shears and moments as assumed by traditional design. Certain limitations on the geometry of the deck are listed in S9.7.2. Once these limitations are satisfied, the specifications give reinforcement ratios for both the longitudinal and transverse reinforcement for both layers of deck reinforcement. No other design calculations are required for the interior portions of the deck. The overhang region is then designed for vehicular collision with the railing system and for
Task Order DTFH61-02-T-63032 4-1 Design Step 4 DECK SLAB DESIGN Design Step 4.1 In addition to de... more Task Order DTFH61-02-T-63032 4-1 Design Step 4 DECK SLAB DESIGN Design Step 4.1 In addition to designing the deck for dead and live loads at the strength limit state, the AASHTO-LRFD specifications require checking the deck for vehicular collision with the railing system at the extreme event limit state. The resistance factor at the extreme event limit state is taken as 1.0. This signifies that, at this level of loading, damage to the structural components is allowed and the goal is to prevent the collapse of any structural components. The AASHTO-LRFD Specifications include two methods of deck design. The first method is called the approximate method of deck design (S4.6.2.1) and is typically referred to as the equivalent strip method. The second is called the Empirical Design Method (S9.7.2). The equivalent strip method is based on the following: • A transverse strip of the deck is assumed to support the truck axle loads. • The strip is assumed to be supported on rigid supports at the center of the girders. The width of the strip for different load effects is determined using the equations in S4.6.2.1. • The truck axle loads are moved laterally to produce the moment envelopes. Multiple presence factors and the dynamic load allowance are included. The total moment is divided by the strip distribution width to determine the live load per unit width. • The loads transmitted to the bridge deck during vehicular collision with the railing system are determined. • Design factored moments are then determined using the appropriate load factors for different limit states. • The reinforcement is designed to resist the applied loads using conventional principles of reinforced concrete design. • Shear and fatigue of the reinforcement need not be investigated. The Empirical Design Method is based on laboratory testing of deck slabs. This testing indicates that the loads on the deck are transmitted to the supporting components mainly through arching action in the deck, not through shears and moments as assumed by traditional design. Certain limitations on the geometry of the deck are listed in S9.7.2. Once these limitations are satisfied, the specifications give reinforcement ratios for both the longitudinal and transverse reinforcement for both layers of deck reinforcement. No other design calculations are required for the interior portions of the deck. The overhang region is then designed for vehicular collision with the railing system and for
Uploads
Papers by Ashish sh