Introduction

This course provides practical information regarding the decking options and design considerations for steel bridges, presenting deck types such as concrete deck slabs, metal grid decks, orthotropic steel decks, wood decks, and several others. The choice of a particular deck type to use can depend on several factors, which may include the specific application, initial cost, life cycle cost, durability, weight, or owner requirements. For the deck types discussed herein, a brief description of the particular deck type is given, in addition to general design and detail considerations. Reference should be made to the AASHTO LRFD Bridge Design Specifications (7th Edition, 2014), Section 9: Decks and Deck Systems (1), for specific design requirements associated with the various deck types.

The primary function of a bridge deck is to support the vehicular vertical loads and distribute these loads to the steel superstructure. The deck is typically continuous along the length, and across the width, of the span of the bridge. In most applications, the bridge deck is made composite with the steel superstructure through positive attachment to the girders, such as using shear connecters to attach the concrete deck slabs to steel girders. In such cases, the deck serves as part of the top flange in the composite section and can be utilized for strength and stiffness. The deck is subjected to local flexural bending of the slab spanning over the girders in the transverse direction caused by the vehicle wheel loads. When the deck is made composite, it is also subjected to longitudinal stresses caused by flexure along the span. The deck, when positively attached to the girders, provides continuous bracing of the top flange in the finished structure, and provides stability to the overall bridge system. The deck will also act as a horizontal diaphragm that is capable of transferring lateral loads, such as wind or seismic loads, to the supports.