Ahmed B. Shuraim

A novel approach for evaluating the concrete shear strength in reinforced concrete beams

The paper presents a rational procedure for evaluating the concrete shear strength in reinforced concrete beams. Previous research has shown that the shear in concrete is resisted by various mechanisms and the resistance degrades with the increase of flexural deformation. The paper introduces a novel approach in utilizing the knowledge about shear resistance degradation by coupling the shear resistance with the shear demand. Both the shear resistance and shear demand are correlated with flexural tensile strain from compatibility and equilibrium requirements. The basic shear strength, under a given loading is determined from the intersection of the demand and resistance curves. The procedure was verified against a database of 232 beams collected from 10 sources with a broad range of parameters. It showed good prediction capability and can be useful to design practice.

Behavior of Wide Shallow RC Beams Strengthened with CFRP Reinforcement

One-way reinforced concrete joist floors with wide shallow beams (WSBs) are used widely in building construction throughout the Middle East. The short- and long-term behavior of WSBs externally strengthened with carbon fiber-reinforced polymer (CFRP) reinforcement was studied on isolated beams and as part of full-scale building. This paper presents the results of the experimental investigation on the flexural performance of isolated WSBs externally strengthened with CFRP reinforcement. A total of six full-scale beams were constructed and tested to failure. The test variables were the amount, type, configuration, and the elastic modulus of CFRP reinforcement. The test results were presented in terms of deflections, ultimate capacities and modes of failure, crack width development, and strains in reinforcement and concrete. The test results showed significant improvement in the flexural performance of the strengthened beams with respect to flexural capacity, flexural stiffness, and crack width. All but one of the strengthened beams failed because of the debonding of CFRP reinforcement; however, the load carrying capacity of WSBs were more than that predicted by relevant design guidelines.

Effect of stirrup corrosion on the shear strength of reinforced concrete short beams

AbstractThe effect of stirrups damage due to corrosion on the shear strength and behaviour of reinforced concrete beams was experimentally investigated. A total of fourteen full-scale reinforced concrete beams were constructed and tested under four-point bending up to failure. The test beams were 200 mm wide, 350 mm deep, and 2800 mm long. The reinforcing stirrups of nine of the beams were subjected to accelerated corrosion prior to structural testing. The test variables were the corrosion damage level, spacing of stirrups, and shear span to depth ratio. The beams were tested under shear span to depth ratio of 2 or 1 representing short or deep members. The test results indicated that the corroded beams exhibited degradation in stiffness and shear strength in comparison to the uncorroded control specimens. This degradation appeared to increase as the corrosion level increases and as stirrup spacing as well as shear span to depth ratio decreases.

Numerical forensic model for the diagnosis of a full-scale RC floor

The paper presents the results of an investigation on the diagnosis and assessment of a full-scale reinforced concrete floor utilizing a 3-D forensic model developed in the framework of plasticity-damage approach. Despite the advancement in nonlinear finite element formulations and models, there is a need to verify models on nontrivial challenging structures. Various standards on strengthening existing structures consider numerical diagnosis as a major stage involving safety and economical aspects. Accordingly, model validity is a major issue that should preferably be examined against realistic large-scale tests. This was done in this study by investigating a one-story joist floor with wide shallow beams supported on columns. The surveyed cracking patterns on the entire top side of the floor were reproduced by the forensic model to a reasonable degree in terms of orientation and general location. Concrete principal plastic tensile strain was shown to be a good indirect indicator of cracking patterns. However, identifying the underlying reasons of major cracks in the floor required correlating with other key field parameters including deflections, and internal moments. Therefore, the ability of the forensic model to reproduce the surveyed damage state of the floor provided a positive indication on the material models, spatial representation, and parameter selection. Such models can be used as forensic tools for assessing the existing conditions as required by various standards and codes.

Efficiency of CFRP Strengthening in Controlling the Deflection of RC Beams in a Redundant Structural System

AbstractOne-way reinforced concrete joist floor with wide shallow beams (WSBs) are used widely in building construction throughout the Middle East. Situations arise when it is desirable to strengthen a specific member or a group of members in a floor to reduce their deflections. Extensive work has been made on the strengthening of isolated members using fiber-reinforced polymers (FRP) for providing much needed data on the member performance and characteristics where the ultimate goal is to apply these findings to actual complex existing structures. Judging by studies on individual isolated members strengthened with FRP, a substantial improvement in deflection control is expected. However, this cannot be directly applied to members in redundant structural systems before confirming that experimentally. This paper presents the results of an investigation on the effectiveness of carbon FRP (CFRP) external strengthening for the purpose of reducing deflection of WSBs as part of joist floor of a prototype reinfo...