The assessment of reinforced concrete solid floor slabs subjected to combined actions of vertical and lateral load

Abstract

Reinforced concrete floor slabs carry gravity load and behave as rigid floor diaphragms to provide stability and lateral resistance to wind actions, earthquakes and lateral soil loads. Floor slabs are often analyzed and designed as uniform plate elements which only possess out-of plane stiffness to carry forces acting normal to the plane. However, an important issue which is often overlooked by the design engineers is that in order for a slab to provide ideal diaphragm actions, the slabs must possess adequate thickness. When slabs are subjected to out-of-plane bending moment due to gravity load and significant compressive forces, they would behave like a slender columns or walls. As consequences of additional deflection and secondary stresses on slabs, particularly at basement floor where lateral forces due to earth and water pressure are significant, the concrete slabs might crack. The project studied the assessment of strength and behaviour of conventional basement floor solid slabs that are subjected to combined actions of vertical and lateral forces. A typical conventional basement floor was proposed and analysed. The solid slabs panels were analysed and designed according to equation and coefficient in code of practice BS8110. Besides, first order and second order analysis using finite element method were carried on the proposed model subjected to gravity force and combined gravity and lateral forces. The results indicate that non-linear analysis could significantly increase the vertical deflection slabs upto 12.29%, bending moment upto 8.45% and shear forces upto 5.86% in minor or major axis of the slabs spanning. Possible visible cracking would occur near to the column support area and soffit of corner slab panels.