International Journal of Current Engineering and Technology E-ISSN 2277 – 4106, P-ISSN 2347 – 5161 ©2018 INPRESSCO ® , All Rights Reserved Available at http://inpressco.com/category/ijcet Research Article 313| International Journal of Current Engineering and Technology, Vol.8, No.2 (March/April 2018) New Methods to Resisting Punching Shear Stress in Reinforced Concrete Flat Slabs Fatma M. Eid #* , Tayel Magdy ^ and Ebada Ahmed^ # Civil Engineering Department, Faculty of Engineering, Menoufia University, Shebein Alkom, Egypt Received 01 Feb 2018, Accepted 01 April 2018, Available online 02 April 2018, Vol.8, No.2 (March/April 2018) Abstract Punching shear failure is a major problem encountered in the design of reinforced concrete flat slabs. The utilization of shear reinforcement via shear studs or other means has become a choice for improving the punching shear capacity. In this study, a new alternative of reinforcement modalities were tested and demonstrated the effect of self- compact concrete on the punching shear capacity, beside that compared between the difference codes to identify the suitable one for determining the position of critical section of punching shear. Nevertheless, in this investigation, the proposed reinforcement system is examined for interior columns only. An experimental work consisting of six specimens: five of them were cast with normal reinforced concrete and one was cast with self-compact strength concrete. The obtained results indicate that the proposed shear reinforcement system has a positive effect in the enhancement of the punching shear capacity of interior slab–column connection of self-compact strength concrete. Keywords: Flat slab; Punching shear; Crack pattern; Ductility; Self-compact concrete. Introduction 1 Punching shear is a critical design factor of reinforced concrete flat slabs since it is associated with brittle failure. The punching shear strength and deformation capacity are strongly influenced by the type and characteristics of the shear reinforcing system. Ruiz and (Muttoni et al, 2010) carried out a series of a six full scale slab tests (3.0 x 3.0 x 0.25 m) with the same flexural and shear reinforcing ratio. The slabs were different punching shear reinforcing systems; e.g., separated stirrups, continuous stirrups, bonded reinforcement with anchorage plates, vertical studs and inclined studs. The improvement in punching shear strength and ductility as a result of these systems increased with the same order as they have been mentioned, with the vertical and inclined studs giving the best results; 77% and 119% improvement, respectively. Bent-up bars also improve the punching shear strength and deformation capacity as reported by (Tassinari et al, 2011). (Lips et al, 2012; Muttoni et al 2010) demonstrated the positive effect of both shear studs and continuous stirrups on the punching shear strength and deformation capacity of slab–column connection. The same conclusion was achieved by (Pilakoutas et al, 2003) for inclined shear band reinforcement. The shear strength is proportional to the flexural reinforcement ratio; in contrast, the rotation capacity is inversely proportional to the *Correponding author’s ORCID ID: DOI: https://doi.org/10.14741/ijcet/v.8.2.19 flexural reinforcement (Kinnunen et al, 1960). This study explored the possibility of enhancing the punching shear strength by introducing horizontal mesh reinforcement at the middle of the depth of slab– column connection zone. This reinforcement arrangement is easy to apply and economic in comparison with the other reinforcement types. (Kueres et al, 2017) evaluated the punching shear design provisions according to Eurocode 2 by means of comparisons with test results. To verify the changes in the current design provisions, the new design method was evaluated using large databanks for flat slabs and column bases without and with shear reinforcement as well as systematic test series. The evaluation of the large databanks indicates a well-balanced level of safety of the proposed design method for all investigated types of members. (Mabrouk et al, 2017) asses the contribution of horizontal flexural reinforcement and vertical shear reinforcement on the punching behavior of reinforced concrete flat slabs. The result from this study showed that the failure of all the tested specimens was a brittle punching failure, adding vertical shear reinforcement in the form of stirrups improved the punching capacity of the slabs, increasing the width of stirrups caused a slight increase in the punching strength, also as the flexural reinforcement ratio was increased, the punching capacity was increased. Finally the current Egyptian code is more conservative than the ACI code in estimating the punching shear capacity.