Failure of flat slabs usually occurs by punching shear mode. Current structural codes provide an experience-based design provision for punching shear strength which is often associated with high bias and variance. This paper investigates the effect of adding a horizontal reinforcement mesh at the top of the slab-column connection zone on punching the shear strength of flat slabs. A new equation considering the effect of adding this mesh was proposed to determine the punching shear strength. The proposed equation is based on the Critical Shear Crack Theory combined with the analysis of results extracted from previous experimental and theoretical studies. Moreover, the equation of load-rotation curves for different steel ratios together with the failure criterion curves were evaluated to get the design points. The investigated parameters were the slab thicknesses and dimensions, concrete strengths, size of the supporting column, and steel ratios. The model was validated using a new set of specimens and the results were also compared with the predictions of different international design codes (ACI318, BS8110, AS3600, and Eurocode 2). Statistical analysis provides that the proposed equation can predict the punching shear strength with a level of high accuracy (Mean Square Error =2.5%, Standard Deviation =0.104, Mean=1.0) and over a wide range of reinforcement ratios and compressive strengths of concrete. Most of the predictions were conservative with an underestimation rate of 12%. Doi: 10.28991/CEJ-2022-08-01-013 Full Text: PDF

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This study aims to determine seismic hazard in Aqaba city which is located in the southern part of Jordan at the Gulf of Aqaba. Nineteen active seismic area sources are considered in this study. The seismic sources within a circle of 300 km radius covering the faults to determine the Peak Ground Acceleration (PGA) and Response Spectra curves for different return periods (475, 975, and 2475 years) for nine selected sites in Aqaba city was considered. These nine sites represent different soil profiles of the city. It is resulted that 95% of the seismic hazard of the studied area is due to the sources lies within the influence circle (i.e., 300 km). The calculated PGA value for 10% of being exceeded in 50 years (i.e., return period=475 years) is 0.3g, meanwhile it is considered in the Jordan Building Code for Seismic Resisting Design (JBC) as 0.2g. Furthermore, the PGA for 5 % (return period=975 years) and 2% (return period=2475 years) are 0.45g and 0.52g, respectively. The results for soil profiles hard rock (SA), and stiff soil (SD) for periods 0, 0.2, and 1 second were 0.3g, 0.7g, 0.2g, and 0.35g, 0.79g, 0.2g (for return period of 475 years) respectively. It is noted that the maximum spectral acceleration is 0.87g at Aqaba southern coast for stiff soil profile, while its minimum value is 0.7g at the northern part of Aqaba for stiff soil profile for return period 475 years.