An experimental investigation was conducted at the structural laboratory at Memorial University of Newfoundland to examine the behaviour of high-strength concrete two-way slabs. It was evident that a new mechanical model is required to predict the punching shear capacity of such slabs. The experimental results of the tested slabs with regard to deformations, strains, ultimate capacity, and modes of failure were examined. Based on the test results, a mechanical model was adopted and developed for high-strength concrete slab applications. The formulation takes into account the actual behaviour of the high-strength concrete and steel. The proposed model gives a fairly good agreement between the predicted and experimental punching loads.A la suite d'une etude expCrimentale rCalisCe au laboratoire des structures du Memorial University of Newfoundland afin d'examiner le comportement de dalles de bCton h deux voies h haute rksistance, les chercheurs ont constatt la nCcessitC d'un nouveau modkle mkcanique afin de prCdire la contrainte de poin~onnement de ces dalles. Les rksultats experimentaux des essais relatifs h la dCformation, h I'effort, h la capacitC ultime et aux modes de dtfaillance ont CtC examinCs. Compte tenu de ces resultats, un modkle mCcanique a CtC adopt6 et ClaborC pour les dalles de bCton h haute resistance. La formule tient compte du comportement actuel du bCton h haute rCsistance et de l'acier. Le modkle proposC permet d'obtenir une assez bonne concordance entre les charges de poin~onnement prCvues et celles mesurCes en laboratoire.Mors clPs : flkches, dkformations, mCcanismes de dkfaillance, plaques de bCton plates, bCton h haute rCsistance, charges (forces), modkle mtcanique, contrainte de poin~onnement, bCton armC.[Traduit par la rCdaction]Can. 1. Civ. Eng. 18, 954-963 (1991)
IntroductionSummary of experimental investigation Research on punching shear has yielded a number of methods by which the ultimate shearing strength of slabs can be predicted. In general, the various suggested approaches can be described as either the results of an empirical study, in which a statistical analysis of the available test results is used to establish a relationship between the load or stress at failure and the parameters of the slab, or the result of a rational study, in which the strength of the slab materials and the mechanism of failure are idealized and described mathematically.The ACI 318 (American Concrete Institute 1989) and CSA (CAN3-A23.3-M84) (Canadian Standards Association 1984) codes are based mainly on Moe's work (1961), while the BS 81 10 (British Standard Institution 1985) code is based on Regan's work (1974). These present building code specifications for the shear strength of reinforced concrete slabs are based on the test results of slabs made with relatively low compressive strengths, varying mostly from 14 to 40 MPa. Test results revealed that the present North American codes overestimate the influence of the concrete strength, as a factor, on the ultimate capacity of two-way slabs. Hence, it is...