Slabs punching shear capacity for normal strength concrete (NSC) and high strength concrete has been investigated in this paper. Due to the significance of concrete technology in the construction industry, more attention has been paid to high strength concrete in this paper. Then, detailed comparison is carried to evaluate the outcome by referring to several existing standards.Slabs punching tests have been collected from the reported results in the literature. Forty-seven tested slab specimens have been grouped from the available published information. In this work, the collected specimens are studied thoroughly, and a conclusion has been drawn from the preliminary investigation that punching shear failure is a common feature in the forty-seven specimens. The collected concrete slab specimens have diversified cylinder compressive strength (𝑓 𝑐 ′ ) ranged from 14.4 MPa to 119 MPa. However, the application of (𝑓 𝑐 ′ ) in existing codes is restricted to a limit as mention hereafter. American Concrete Institute (ACI-14) limits the practical application of 𝑓 𝑐 ′ to 69MPa, while The Australian Concrete Structures Standard (AS-94) limits 𝑓 𝑐 ′ to 50 MPa. The recent evolvement in concrete technology has made the production of HSC with 𝑓 𝑐 ′ much greater than the aforementioned values affordably reachable. Therefore, the present research attempts to bridge this gap and goes beyond the standards restrictions. This has been achieved by proposing a new design equation for punching shear through applying a regression analysis. The accuracy of the proposed equation and the existing equations have been examined by utilizing statistical analysis [Arithmetical mean (𝑥̅ ), Variation (VAR), Standard Deviation (SD) and Coefficient of Variation (COV)] to the punching shear failure strength values. The proposed method results for 𝑥 ̅ , VAR, SD and COV are 1.575, 0.364, 0.1299 and 23.128% respectively, and these are smaller when compared with the other 6 existing code methods.

Concrete Technology has been developing for more than a century. One of the most exceptional achievements in concrete technology is the evolving of Ultra-High Performance Concrete (UHPC) which has been a research focus in a wide applications diversity. In this paper, an experimental work has been carried out for investigating the transverse and longitudinal reinforcements’ variation influence on the axial capacity of UHPC columns. Eight columns (five UHPC columns and three Normal Strength Concrete (NSC) columns) have been poured and tested under a concentric axial compression load till a failure is reached. Then, the results are reported herein. The experimental results show that UHPC columns failed in a controlled manner and no concrete chips or a concrete cover spalling are observed. Also, the longitudinal reinforcements have not buckled away beyond the peak load because of the presence of the reinforcing steel fibers in UHPC. Correspondingly, the steel ties spacing proportionally affects the load carrying capacity of columns as presented hereinafter.

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This paper presents the results of experimental study on reinforced concrete columns rehabilitation with carbon fiber reinforced polymer (CFRP) under concentrated load. Twelve short circular reinforced concrete columns (150 mm diameter and 600 mm height) were tested. Three specimens were unstrengthening and tested until failure as control specimens. Nine specimens were rehabilitation by carbon fiber reinforced polymer after loading about 75% from ultimate axial load capacity of control specimens. The test parameters were the type of concrete are normal strength concrete (NSC), high performance concrete (HPC) and high performance concrete containing engine oil (HPCEO) in additional to effective the ratio CFRP confining (fall wrap (100%strengthening), 50mm strips wrap 50mm spacing (50%strengthening)and 40mm strips wrap-60mm spacing(40%strengthening)). Test results showed that Adding used engine oil to concrete have significantly effect on workability of concrete where work as plasticizer. HPCEO mix showed lower strength (compressive, splitting tensile and flexural) and ultimate axial load of column than those HPC mix but greater than NSC mix. Where the compressive strength of concrete was (27.3 MPa, 45.8 MPa and 69.7 MPa) for NSC, HPCEO and HPC respectively. The ultimate axial load capacity of unconfined reinforced concrete columns was (52 ton, 78 ton and 117 ton) for NSC, HPCEO and HPC respectively. Reducing efficiency of rehabilitation by CFRP with increasing in compressive strength of concrete. The ratios of increasing in ultimate axial load capacity of rehabilitation RC columns with 100% and 50% wrapping in comparison with 40%wrapping are 20% and 4% respectively for NSC, while these ratios become 15% and 5% respectively for HPCEO and for HPC , these ratios are 10%and 3% respectively.