Assessment of the rotational stiffness within the reinforced concrete slab : masonry wall joint subjected to vertical loading

Abstract

This paper aims to test the rotational restraint behaviour between a reinforced concrete slab and a masonry wall within the inter-face at the recessed masonry pocket, commonly known as ‘Ingal’ in Maltese. Local traditional construction has developed to integrate materials such as reinforced concrete and steel. The interaction between traditional structural members such as masonry walls, with reinforced concrete slabs is highlighted within third party property walls, and their assumed boundary conditions. Different boundary condition will influence the forces, deformations and movements expected within the structural members and their connections. Eurocode Eight guides structural engineers to assume a full fixity between a reinforced concrete slab, which is embedded on half the supporting wall width, regardless of the anticipated load on the wall and on the slab. Through a set of experiments, the boundary conditions and the rotational restraint within the recessed masonry pocket will be measured, in sight of comparing the obtained data with the Eurocode Eight principle. The rotational restraint of the slab within the X-direction is the sole area of focus, with governing parameters of structural members, vertical loading and anticipated failure modes being discussed and documented. The experimental data was obtained through a configuration of the existing University of Malta Concrete lab pit. The testing set up included a full-scaled cantilevered reinforced concrete slab resting upon a supporting layer of bricks/ stone, which lays under a concrete spreader beam. The applied load is provided on two areas of the experiment which were on the concrete spreader beam directly above the recessed pocket and on a steel beam at the free end of the cantilever reinforced concrete slab. Measuring apparatus such as linear variable differential transformers and clinometers were set along the span of the slab, recording the displacement due to the rotation. Three sets of experimental configurations were tested in sight of understanding the rotational behaviour due to different supporting embedments, which include; a full embedment of slab onto 230mm brick, a half embedment on brick (115mm) and a full embedment of slab onto 180mm of stone. Following incorporated safety parameters and quality control checks, the findings include a descriptive analysis of each test specimen at a comparable and constant restraining load on the segmented masonry wall. Graphic representations of the data produced comparable regions upon loading and unloading, which defined the influencing factors of rotation due to different embedment depths. Through this study, the rigid body movement of the wall and slab is account to the embedment depth of slab onto wall, the restraining vertical load experienced by the wall and due to the vertical load applied on the slab. The study includes suggestions for further research work which are relevant to the scope of the research.