Orthotropic analysis of voided slab bridges

Circular voids are often incorporated in concrete bridge deck slabs to reduce their self weight without greatly reducing their flexural stiffness. These slabs are orthotropic as their flexural stiffness is different in the longitudinal and transverse directions, The degree to which this orthropy affects the behaviour of the bridge deck is largely dependant on the size of the voids relative to the slab depth. This paper presents a method of modelling voided slabs using orthotropic finite elements, A range of voided slab bridge decks with different void diameter to slab depth ratios is considered and analysed using this method. Comparisons are made of transverse moments and transverse flexural stresses from these analyses with those from a simpler isotropic analysis. Results from elaborate three-dimensional solid finite element analyses are also presented for comparison. The paper concludes with recommendations relating to modelling of voided slabs.