778 J. Eng . Te c hno l. Sc i., Vo l. 50, No . 6, 2018, 778-796 Received June 7 th , 2018, 1 st Revision October 29 th , 2018, 2 nd Revision November 19 th , 2018, Accepted for publication December 26 th , 2018. Copyright ©2018 Published by ITB Journal Publisher, ISSN: 2337-5779, DOI: 10.5614/j.eng.technol.sci.2018.50.6.3 Hollow Core Slabs on Winkler Foundation Adel A. Al-Azzawi Department of Civil Engineering, Al-Nahrain University, Ministry of Higher Education and Scientific Research, Al-Jadriya 10070, Baghdad, Iraq E-mail: dr_adel_azzawi@yahoo.com Abstract. This research dealt with the linear elastic behavior of hollow core slabs resting on a linear Winkler type foundation. A finite difference method was used to model the slabs as wide beams and the foundation as elastic springs. The finite element method was also used to model the problem using ABAQUS 6.10 software program. A comparison between the method proposed in this paper and methods from previous studies was made to check the accuracy of the solutions. Several important parameters were incorporated in the analysis, viz. the hollow core size and shape, subgrade reaction and slab depth, to trace their effects on deflections, bending moments and shear forces. A computer program coded in Fortran was developed for the analysis of hollow core slabs on an elastic foundation. It was found that the maximum difference in deflection between the present study and the exact solution was 3% for the finite difference and 7% for the finite element method. Keywords: hollow core; finite differences; finite elements; slabs; Winkler foundation. 1 Introduction The footing slabs of concrete buildings are supported directly by the soil medium. Modeling the soil medium is a very complicated problem. Therefore, structural engineers have tried to simplify soil behavior through using a simplified Winkler subgrade model. This model treats the soil as a linear elastic material that displaces independently at different points. The problem of reducing the dead load of a thick footing on soil is very important, especially for soils with low bearing capacity. The most efficient weight reduction for flexural members can be achieved through removing mass near the centroid of such members. One-way hollow core slabs are examples of this technique, which can be modeled using two-dimensional plate members or as wide beams. The latter approach approximates the problem through one-dimensional members or elements that support the applied loads through flexural and shearing impedances that develop in the slab cross-section. The famous formula (d4w/dx4 = q/EI) has been derived for the flexure of shallow or thin beams subjected to transverse distributed load (q) (per unit length). This classical equation discards the effects of deformation due to transverse shear [1,2].