Aim of the Course is to propose a systematic and balanced presentation of the essential background of the mechanics of the main types of bridges and to provide students with the basic tools for bridge design.

The main themes are: basics of influence lines; transversal load redistribution in multi-beam, multi-cell and box decks; curved and skew deck bridges; continuous girders; arch bridges; cable stayed bridges; suspension bridges; elements of bridge aeroelasticity.

The objective is introducing students to the basic computations for a sound preliminary design, suitable to produce dimensions of the main structural members, weight estimation, bearing capacity, detailing of the most critical parts and costs. The preliminary design of a bridge represents its actual “design”. The successive analyses confirm, correct and enhance the initial choices done before.

• Knowledge of the characteristics of the main bridge typologies and understanding of their basic mechanical behaviour.
• Starting from the proposed worked examples and using the skills acquired during design practice sessions, capability of translating theory into practice.
• Capability of independently drafting a design proposal, and to critically compare the chosen structural typology to different options.
• Capability of designing a Prestressed Box Girder Bridge, consisting in a Computational Report and Tables/Drawings of the bridge structures and of their most important details.

1. Introduction. Role of a bridge. Bridge costs. Life cycle. Bridge typologies. Reinforced and prestressed concrete bridges. Composite and steel bridges. Sectional geometries: grillage slabs, voided slabs, box girders. Arch bridges. Cable stayed and suspended bridges. Construction methods. Cast-in-place and precast prestressed bridges. Span by span construction. Prestressed segmental bridges.
2. Structural reliability. Highway and railway bridge loads. Serviceability and limit state design. International codes of practice.
3. Influence lines theory. Influence surfaces theory (Pucher, Homberg).  Analysis of the local effects on deck slabs and on deck slab cantilevers.
4. Bridge deck analysis. Orthotropic plate analysis. Grillage and space frame analysis. Voided slab decks. Special methods of analysis. Transversal load distribution theories. Engesser-Courbon and Massonnet methods.
5. Box girder bridges. Thin walled structures theory. Shear and torsion in mono- and multicell box girders. Shear lag, warping and distortional effects. Folded plate theory. Finite strip method. Thermal stresses.
6. Skew and curved decks.
7. Long span bridges. Segmentally erected bridges. Balanced cantilever bridges. Dimensioning criteria. Time dependent behaviour.
8. Bridge piers. Mechanical and geometrical nonlinearities. Piers with varying sections.
9. Arch bridges. Line of thrust. Axis of the arch as funicular line of the applied loads. One/two/three hinges arches. Hingeless arches. Influence lines. Analytical approach to Maillart arch analysis. Transversal load distribution in Maillart type bridges.
10. Cable theory. Mechanical properties. Non linear behaviour of the cables. Catenary. Parabola. Comparison of cable shapes. Influence of the sag on the cable stiffness. Dischinger-Ernst E-modulus.
11. Cable stayed bridges. General background. Construction techniques. Preliminary design of stays, antenna and deck. Numerical modelization.
12. Suspended bridges. General background. Construction techniques. Rankine, Melan and Timoshenko theories. Analytical solutions. Numerical modelization.
13. Aeroelastic stability of suspension bridges. A simplified approach to critical wind speed calculation.
14. Abutments. Foundations. Approaching slabs. Bearing supports. Antiseismic devices. Detailing.

Basics of: Engineering Mathematics, Mechanics and Reinforced and Prestressed Concrete Structures.

Students must show a prompt understanding of the mechanical behaviour of the main types of bridge structures. They must prove to be able of choosing suitable analytical or numerical methods of analysis and of formulating critical judgments on a certain type of structure in comparison to other different engineering choices.

The exam consists in a written test. Subjects of the exam are: Solution of an Influence Line + two questions (theory and/or numerical exercises). The completeness, the effectiveness and the quality of the drawings in the Design of a Prestressed Box Girder Bridge, developed during the design practice sessions, will also contribute to the final evaluation.