Engineering Structures 29 (2007) 663–674 www.elsevier.com/locate/engstruct Load deflection behaviour of partially restrained slab strips K.U. Muthu a,∗ , K. Amarnath a , Azmi Ibrahim b , Hashem Mattarneh b a Department of Civil Engineering, MSRIT, Research Centre, M.S. Ramaiah Institute of Technology, Bangalore – 560054, India b Department of Civil Engineering, University Teknologi MARA, Selangor, Malaysia Received 24 January 2006; received in revised form 26 May 2006; accepted 30 May 2006 Available online 2 August 2006 Abstract The paper gives the results of an analytical method proposed to predict the load deflection behaviour of partially restrained slab strips. The effect of deflection prior to yield line load on the development of compressive membrane forces was incorporated in the theoretical analysis. An experimental programme was designed to cast and test ten partially restrained slab strips with different edge rigidity. A comparison has been made between the results of the proposed and one of the other methods available in the literature. The results indicate that the proposed method can predict the load deflection behaviour satisfactorily. A parametric study has been made on the load enhancement beyond yield line load and the results are presented. c  2006 Elsevier Ltd. All rights reserved. Keywords: Analysis; Concrete; Comparison; Deflection; Experiments; Partially; Restrained; Parameters; Slabs; Ultimate load 1. Introduction In a restrained slab, as the slab deflects under the application of load the edges of the slab try to move outwards. In the case of an isolated slab beam system the edge beams provide a lateral restraint to this outward movement and consequently certain inplane compressive forces are introduced across the slab cross section. The inplane forces in turn act on the edge beams and as a result the beams deflect laterally outwards. Thus the development of compressive membrane forces amongst other factors is dependent on the flexural rigidities of the beams. A few studies have been reported on isolated slab–beam systems of rectangular panels and circular slabs with ring beams. Park [1] presented an analysis for the prediction of ultimate loads of partially restrained slabs assuming the restraint at the edges to be of constant stiffness. Hayes and Taylor [2] reported the results of tests of ten reinforced concrete slab beam panels. The variables included the relative strength of beams and slabs, the layout of the slab, reinforcement and details of their connections. They reported that the concentration of reinforcement in the central region has a desirable effect upon the behaviour and would affect the ∗ Corresponding author. E-mail address: kumuthu@rediffmail.com (K.U. Muthu). economy of reinforcement. They pointed out that a good corner connection controls the propagation of cracking in the slab and can increase the load carrying capacity considerably. Girolami et al. [3] reported the tests on specimens subjected to both transverse and inplane loading. A number of point loads were applied over the panel surface to simulate uniform vertical loading. Equal horizontal loads were applied over the panel surface to simulate uniform membrane forces. The membrane loads were held constant during the test. Their tests indicated that the load capacity of a panel can be estimated accurately if the membrane forces acting on the panel [3] are known. Hopkins and Park [4] tested a one fourth scale concrete slab–beam floor system. Their study showed that lack of information concerning the long term behaviour of the slab may limit the applicability of compressive membrane action in design. Datta and Ramesh [5,6] have proposed a method to predict the ultimate load of slab–beam panels and checked the validity of the method with their tests on nineteen square isotropic slab–beam panels. In the analysis they assumed a suitable value of deflection at ultimate to calculate the ultimate load. They assumed a value of deflection equal to 0.8 times the slab thickness for specimens with low edge beam stiffness and the experimental deflection for the slab–beams with higher degree of value of stiffness. Desayi and Kulkarni [7] reported a method to predict the complete load deflection behaviour 0141-0296/$ - see front matter c  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.engstruct.2006.05.017