Bridge Design

8Design Examples: Concrete and Composite Options

8.1 Introduction

Two design solutions are presented for a continuous three span bridge deck. A twin‐girder deck is adopted for both solutions: a prestressed concrete and a steel‐concrete composite deck. The aim is to present the design steps of a road bridge deck with straight alignment, initially discussing possible solutions and justifying different options at a conceptual design level. Then, key aspects of structural safety and serviceability for both options are checked.

The bridge, its function and the materials adopted are presented in Section 8.2; hazard scenarios and actions are referred to in Section 8.3.

Section 8.4 covers the pre‐design of the concrete solution, the structural analysis and safety verifications for ultimate and serviceability limit states (ULS and SLS) of the deck. Section 8.4.3 highlights the distribution of internal moments and forces, explains how to obtain the hyperstatic effects for a longitudinal prestressing layout and discusses the influence of the construction stages.

Section 8.5 presents the pre‐design of the steel‐concrete composite solution. ULS and SLS design verifications are presented for concrete slab and steel girders. Section 8.5.3 highlights the distribution of internal moments and forces, and explains the effects of slab shrinkage and imposed deformations.

Iterative design procedures are not covered by this example, with checks being carried out only for the final proposed geometries. ...