PCI eLearning Course T356: Curved Bridge U-Girders-Design Details-T356.14 Course reference material

T356.14 Course reference material

Pdf Summary

Strut-and-tie modeling (STM) is a design method widely used in structural engineering to visualize load transfer mechanisms and guide the detailing of reinforced and prestressed concrete members. It is included in the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications since 1994. This design approach allows structural designers to consider the transfer of loads from their points of application to the structural foundations. <br /><br />When designing for combined shear and torsion, the AASHTO LRFD specifications provide guidance on load transfer mechanisms based on STM. The selection of load transfer options depends on the specific design scenario. For example, when a U-beam is rigidly connected to an integral straddle bent, the load transfer can be applied at different nodes of the connection. <br /><br />The design option chosen affects the detailing of reinforcement within the U-beam and the straddle cap. For instance, if the reaction of the U-beam is divided in half and applied at nodes A and B, a substantial amount of hanger reinforcement must be provided within the U-beam and cap to accommodate the load transfer. <br /><br />Alternatively, if the reaction is divided into four equal loads and applied at nodes A, B, C, and D, the amount of hanger reinforcement is reduced, making the detailing and construction more feasible. <br /><br />By using STM, structural designers can ensure the appropriate load transfer and detailing of concrete members, resulting in more efficient and reliable structures.

Keywords

Strut-and-tie modeling

structural engineering

load transfer mechanisms

reinforced concrete members

prestressed concrete members

AASHTO LRFD Bridge Design Specifications

combined shear and torsion

load transfer options

U-beam

hanger reinforcement