This work presents the results of experimental tests on reinforced concrete slabs with different longitudinal reinforcement ratio ρ under concentrated load. Five series of specimen were made and tested, a total of ten slabs. The measurements of the specimens were 2135×2135×140 mm (Fig. 3). Longitudinal reinforcement ratio ρ = 0,449–1,90 %, the diameter of reinforcing bars was 8–16 mm, reinforcement bore yield stresses, spacing between bars was 100 mm. The protective concrete layer of the longitudinal reinforcement in all slabs was 20 mm. The cubic compressive strength of concrete fc,cube = 33,4–46,6 MPa. In the course of the experiment the measurements of the collapsing punching force, the radial and tangential deformations of the compression zone were made, the curves of their expansion were given, displacements of the column head were measured. The surface of the punching cone, irrespective of the longitudinal reinforcement ratio ρ, makes a ˜35° angle with the bottom (compression zone) surface of the slab. Deformations of radial and tangential directions in the compression zone during the course of cracking of the slab do not reach the ultimate compressive strains of concrete (3,50 ‰), the mean value of deformations in the radial direction is 1,6 ‰, the mean value of deformations in the tangential direction is 1,8 ‰, which allows to make a conclusion that the slab is punched-through under transverse collapsing force. The strength criterion of biaxial stress state proposed by Zalesov et al. (1973) and the expression of the resultant transverse force of the dowel action of the longitudinal reinforcement ratio ρ as proposed by Theodorakopoulos et al. (2002), were used to get the expression of the collapsing transverse force Vu which is given in equation (2). The factor of the influence of longitudinal reinforcement ratio ρ expressed through the resultant transverse force Vd of the dowel action makes 40–50 % of the collapsing force, Vd increases with increasing of the longitudinal reinforcement ratio ρ. The resultant transverse force Vc of the compression zone of concrete in the critical section makes 50–60 % of the collapsing force, Vc increases with increasing of the longitudinal reinforcement ratio ρ.

Abstract. The paper analyzes the dependence of punching shear strength reliability index β, calculated according to En 1992En -1-1:2004En (2004 and sTR 2. 05.05:2005 (2005) in reinforced concrete floor slab-to-column joint on the values of random factors. The paper deals with theoretical research of the influence of independent random variables, such us the value of the characteristic compressive strength f ck of concrete, the area A s of the longitudinal reinforcement, effective cross-section depth d and the ratio of the self-weight and the effective load on the value of the reliability index β. The paper presents experimental results of reinforced concrete slabs with different longitudinal reinforcement ratio ρ subjected to a concentrated load. it was determined that when the effective load makes around 50% of the construction self-weight load, i.e. G k /Q k = 2 and when minimal variation coefficient estimates are taken (for concrete strength δf c = 0.1, for effective depth δd = 0,1 and for the area of longitudinal reinforcement cross-section δA s = 0.05 or δA s = 0.075 and when G k = Q k i.e. G k /Q k = 1 where δf c = 0.1, δd = 0.1 and δA s = 0.05) the reliability index β of the analyzed slabs calculated according to En 1992En -1-1:2004En (2004 as well as β calculated according to sTR 2.05. 05:2005 (2005), is bigger than En 1990En :2002En (2002 recommendation for the minimum value of reliability index -3.8 for RC2 construction reliability class ultimate. in other cases the reliability index β is close to 3.8 or much smaller than 3.8.

This paper analyses the compliance of the design codes calculation methods for punching shear resistance in reinforced concrete slabs STR 2.05.05:2005, E DIN 1045–1, ENV 1992–1‐1 EC 2, prEN 1992–1 [Final draft] EC 2, Model Code CEB‐FIP 1990, BS 8110, ACI 318–99 to the experimental data. It has been analysed whether the difference in the results of the mean punching shear resistance received according to these methods and through experiments is statistically significant, when the level of significance value is 0,05. To analyse the significance of the difference of the means Student t test was used. An analysis was carried out to find out which methods show the least different resistance results from the experimental data. According to this analysis, a classification of methods was made. Student t test was applied to analyse in which methods the ratio between the punching shear resistance results obtained and the punching shear resistance results received through experiment is statistically insignificant. The level of significance value considered was 0,05. It has been determined that almost in all cases the difference between the punching shear resistance results received experimentally and theoretically is statistically significant. It has also been found out that generally the punching shear resistance can be calculated by applying the prEN 1992–1 [Final draft] EC 2 method. The best method to describe the punching shear resistance in minimally reinforced slabs is ACI 318. The worst results are obtained by applying ENV 1992–1‐1 EC 2 and E DIN 1045–1 methods.