Dr Ana M. Ruiz-Teran

Transverse schemes for bridge decks.

Part 2: Slabs

Types of transverse schemes for bridge

decks

Types of transverse schemes for bridge decks:

Beam deck:

Slab deck:

Box girder:

Types of slabs

According to the materials and the cross-section:

Solid Slab

Voided Slabs

Multicellular Slabs

According to the bridge cross-section:

Differential equation governing the structural

behaviour

yyxyxxy

xxyxyxx

yxxy

yx

DDGjDEiD

DDGjDEiD

DDDDH

where

yxqy

wD

xx

wH

x

wD

2

1

21

4

4

22

4

4

4

2

),(2

x

z , w

y

Anisotropic slab:

),(24

4

22

4

4

4

yxqy

wD

xx

wD

x

wD

x

z , w

y

Isotropic slab:

Transverse distribution of internal forces in slab

decks

• Transverse flexural stiffness of the slab: The larger the transverse flexural stiffness of the deck, the larger the required transverse shear load (V) for guaranteeing compatibility, the larger the transverse distribution of the applied load, and the smaller the transverse-distribution coefficients

• The transverse distribution is larger in solid slabs than in voided slabs (the transverse-distribution coefficients are smaller in solid slabs than in voided slabs)

•The transverse distribution is larger in voided slabs than in multicellular slabs (the transverse-distribution coefficients are smaller in voided slabs than in multicellular slabs)

•The transverse distribution is larger in slabs than in beam decks (the transverse-distribution coefficients are smaller in slabs than in beam decks)

Factors affecting the transverse distribution of longitudinal bending moments (I):

Diaphragms on voided slabs at the support

sections

Aim:

• To transmit horizontal and vertical internal forces to the bearings at the support sections providing resistance to the induce transverse internal forces

Modelling slab decks

Location of the longitudinal elements:

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

• Second moment of inertia of the transverse members = Second moment of inertia of the corresponding slab section, with respect of the centroid of the slab

• Shear area of the transverse members = equivalent shear area to model the transverse distorsion of the section (only for multicellular slabs)

• 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 slab section (part of the ½ of the total torsional constant proportional to the enclosed area in the corresponding section)

REFERENCES:

CHEN, W. F. AND DUAN L. 2003. Bridge Engineering. CRC Press LLC

HAMBLY, E.C. 1991. Bridge Deck Behaviour. Spon Press.

PARKE G, HEWSON N. 2008. ICE manual of bridge engineering. ICE.

MANTEROLA, J. BRIDGES. (6 Volumes, in Spanish). ETSICCP, Madrid