The real strength of laterally restrained reinforced concrete slabs

  • Ahmed Shaat

Student thesis: Doctoral ThesisDoctor of Philosophy


It is widely recognised that Compressive Membrane Action (CMA ) is the reason for the strength enhancement exhibited by laterally restrained slab system . This strength enhancement is in excess of that estimated by standard flexural and shear design methods.

Although of the fact that the consideration of CMA in design can lead to substantially reduced quantities of flexural reinforcement, it has not been considered by many of the design codes.

This investigation was aimed at extending the knowledge of compressive membrane action in continuous slab systems subjected to concentrated loading such as flat slab systems. This research was also concerned with producing lab with much reduced reinforcement rather than steel-free lab. Those lab which contain reduced quantities of steel reinforcement, raise fewer concerns about cracking and
fatigue loading than steel-free labs.

A simple restraint model that is capable of evaluating the inherent lateral restraint available in different slab configurations was developed. This restraint model was based on the geometrical deformations of the surrounding structure. When this model was incorporated into the method developed at the Queen’s University Belfast for the prediction of the enhanced punching strength of laterally restrained slabs subjected to concentrated loading, good correlation with experimental data was achieved. The proposed method can predict both modes of punching failures, i.e flexural and shear. This suggests that the proposed method is more suitable for general use than the BD81/02 standard, which can only predict the punching shear mode of failure.

The aims of this research also included the examination of the capability of a nonlinear finite element analysis package, ABAQUS, to model slab systems, particularly those restrained in-plane.

The results obtained numerically were compared with those given by the analytical methods developed at the Queen's University and good correlations were achieved. These good correlations indicated that these analytical method are quite accurate.
Date of AwardDec 2005
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorDavid Cleland (Supervisor), Barry Rankin (Supervisor) & Su Taylor (Supervisor)

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