Dr Ana M. Ruiz-Teran Transverse schemes for bridge decks. Part 3: Box girders

Types of transverse schemes for bridge decks

Types of transverse schemes for bridge decks: Beam deck: Slab deck: Box girder:

Transverse structural behaviour under uniform load

Transverse structural behaviour under eccentric point load

(1) Transverse local bending (2.1) Transverse local bending (2.2) Longitudinal bending (2.3.1) Saint- Venant torsion (2.3.2) Distorsion

Additional systems to reduce the transverse local bending in the slab:

Bracing in steel and composite decks to resist distorsion forces:

Diaphragms on box girders at the support sections

Aims: To resist distorsion To transmit horizontal and vertical internal forces to the bearings at the support sections providing resistance to the induce transverse internal forces To allow access through an opening

Modelling box girders

Location of the transverse elements: Transverse members located at diaphragms, mid-span section plus intermediate sections The ratio between the transverse spacing and the longitudinal spacing should not be larger than 2 and smaller than 0.5 Location of the longitudinal elements: One longitudinal element per web, located in the centroid of the section

Second moment of inertia of the transverse members = Second moment of inertia of the corresponding slab section, with respect of the centroid Shear area of the transverse members = equivalent shear area to model the transverse distorsion of the section Torsional constant of the transverse members = Part of the ½ Torsional constant (close circuit through the support diaphragms) proportional the member width Properties of the transverse elements: Properties of the longitudinal elements: Second moment of inertia of the longitudinal members = Second moment of inertia of the corresponding section Torsional constant of the longitudinal members = ½ Torsional constant of the corresponding section (50% of the ½ of the total torsional constant for every member)

REFERENCES: CHEN, W. F. AND DUAN L Bridge Engineering. CRC Press LLC HAMBLY, E.C Bridge Deck Behaviour. Spon Press. PARKE G, HEWSON N ICE manual of bridge engineering. ICE. MANTEROLA, J. BRIDGES. (6 Volumes, in Spanish). ETSICCP, Madrid