Repairing of one-way reinforced concrete slab using externally CNC perforated steel plate. Theoretical study.

Abstract

This research includes the design steps for using solid and perforated steel plate to repair an under reinforcement one-way concrete slab in flexure. All slabs were assumed to be subjected to 85 percent of ultimate load in flexure, therefore the section of the slab to be repairing assumed to be cracked, and the additional external reinforcement represented by the steel plate will be designed according to this assumption and according to the limitations of ACI 318 code specifications. Results of the theoretical calculation indicated that increasing the thickness of the solid plate causes increasing the interface stresses by (72.6%) when replacing the dimensions (width x thickness) of the plate section from (300mm×1mm) to (200mm×1.5mm), while increasing the width of the plate reduces the interface stresses by (48%) when changing dimensions of the plate section to (400mm×0.75mm). Using perforated plate will increase the ductility and reduce the interface shear stresses. Using the plate width to thickness ratio { (bP/dP)=300} will reduce these stresses by (14.8%) when using perforated plate instead of solid one. Increasing the ratio of (bP/dP) lead to reduce the interface shear stresses, as well as reduce the difference between the effect of using solid or perforated steel plates on interface stresses, also when reducing ratio of (bP/dP) the interface shear stress will be increase. Changing the number and diameters of the holes from (10 # 10 mm) to (2 # 50 mm) with keeping the cross-section area of the steel plate constant for both cases increased the resistance of the epoxy nails to the shear stresses that transmitted to them from the axial stresses in the plate by (400%). A new expression is presented in study to calculation the interface shear stress.