Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Punching shear

Punching Shear Resistance of Reinforced Concrete Flat Slabs Strengthened by CFRP and GFRP: A Review of Literature

Hadi N. G. Al-Maliki; Ali Al-Balhawi; Asma M. Ali

Engineering and Technology Journal, 2021, Volume 39, Issue 8, Pages 1281-1290
DOI: 10.30684/etj.v39i8.2011

Flat reinforced concrete (RC) slabs or plates are still widely used in buildings and are most popular in single or multiple story floor construction systems. This is due to the ease and speed of implementation as well as the continuous smoothness that is provided in relation to the locations of members. Flat slab systems have an inadequate shear strength in both directions. Thus, they are subjected to a shear failure at their intersections with columns, which results in the collapse of a larger part of the structure. Shear failure occurs due to many reasons including changing the functions of the facility, the technical errors in the design and implementation procedures, an increase in the load, deterioration of materials, and poor quality. The carbon fiber reinforced polymer (CFRP) sheets/strips and glass fiber reinforced concrete polymer (GFRP) are used as a composite section formulated when there is a structural deficiency. Strengthening by using CFRP and GFRP provide an improvement in the punching shear resistance in both directions as well as flexural strength, ductility, and hardness. They are more suitable for a practical use as a substitute for other costly and difficult approaches such as increase the cross-sectional area of columns and so on. This paper reviews the up to date studies of enhancing the shear resistance of flat slabs by CFRP/GFRP and discusses the used materials for strengthening flat slabs and the used methods, which are used to implement these materials. Also, a summary for the cited studies are stated and the possible future works are suggested.

Nonlinear Finite Element Analysis for Punching Shear Resistance of Steel Fibers High Strength Reinforced Concrete Slabs

Eyad K. Sayhood; Samer P. Yaakoub; Hussien Fadhil Hussien

Engineering and Technology Journal, 2014, Volume 32, Issue 6, Pages 1411-1432

This study is devoted to investigate the punching shear resistance of high strength reinforced concrete slabs with steel fibers by using the well-known (P3DNFEA), a non-linear finite element program for three-dimensional analysis of reinforced concrete structure.
Nine high strength reinforced concrete slabs with steel fibers and one without steel fibers, have been analyzed in the present study. The finite element solutions are compared with the available experimental data. In general, accepted agreement between the numerical results and the experimental results has been obtained.
Parametric studies have been carried out to investigate the effect of concrete compressive strength, steel fiber content, amount of steel rebars, slab depth and column dimensions on the behavior and ultimate strength of reinforced
concrete slabs.
The numerical analysis indicated that the increase in the concrete compressive strength (f'c) from 40 to 80 MPa has led to an increase in the strength by 69% and 84% for slabs without and with 0.5% steel fibers respectively. The numerical analysis indicated that by using 2.0% steel fibers, the ultimate capacity is increased by 81.7%, compared to a slab without fibers.
Also, the finite element solution revealed that increasing the longitudinal reinforcement ratio in the slab from 1% to 2% led to an increase in the ultimate shear strength of about 57%.

Punching Shear Resistance of Reinforced Concrete Flat Plate Slabs Strengthened with CFRP

Eyad K. Sayhood; Mohammed J.Hamood; Aseel A. Abdul Ridha

Engineering and Technology Journal, 2014, Volume 32, Issue 2, Pages 511-529

The purpose of this study is to present a model suitable for analyzing reinforced concrete (RC) slabs strengthened with Carbon fiber reinforced polymer (CFRP) failing in punching shear using the finite element method. a nonlinear three-dimensional finite element analysis has been used to conduct an analytical investigation on the overall behavior of reinforced concrete slabs strengthened with CFRP strips. ANSYS (version 11, 2007) computer program is utilized.The 8-node isoparametric brick elements in ANSYS are used to represent the concrete, the steel bars and CFRP strips are modeled as axial members discrete within the concrete brick elements by assuming perfect bond between the concrete and steel and between the concrete and CFRP strips. The numerical analysis incorporates material nonlinearity due to concrete cracking in tension, nonlinear stress-strain relations of concrete in compression, crushing of concrete and yielding of steel reinforcement. Also, the evaluation of the CFRP strips enhancement in shear strength of RC slabs is investigated.
Different types of RC slabs strengthened with CFRP strips have been analyzed. Available experimental results are chosen to check the validity and the accuracy of the adopted models. In general, a good agreement is obtained between the finite element and the experimental results. The maximum percentage difference in ultimate load-carrying capacity is 8.83%. Several parametric studies have been carried out to investigate the effects of some important material parameters on the behavior of strengthened RC slabs. These parameters are the concrete compressive strength, the concrete tensile strength, the number of layers of CFRP strips, the configuration of CFRP strips and the effect of diagonal stirrups of CFRP.