Ahmed Shuraim - Profile on Academia.edu (original) (raw)

Papers by Ahmed Shuraim

Analysis of Slender Prestressed Concrete Columns

Structural Design, Analysis and Testing, 1989

This paper briefly describes an analytical model developed to study slenderness effects in prestr... more This paper briefly describes an analytical model developed to study slenderness effects in prestressed concrete columns and walls and predict the characteristics of such members over a range of behavior not currently covered by design codes. A limited comparison between predicted and experimental tests is also presented.

Size effect on shear resistance of high strength concrete deep beams

Materials and Structures, Apr 28, 2015

ABSTRACT Size effect on the shear strength of high strength concrete deep beams was investigated.... more ABSTRACT Size effect on the shear strength of high strength concrete deep beams was investigated. A total of 12 full-scale reinforced concrete beams without web reinforcement were constructed and tested up to failure. The test variables included the beam depth and the concrete compressive strength. The beams were simply supported and were tested in four point bending. The test results showed that the shear stresses at failure decreased with the increase in beam depth indicating the existence of size effect. Beams of higher concrete strength exhibited more size effect than beams of normal concrete strength. The shear strength of the beams was analyzed using the ACI 318 strut and tie model (STM) provisions, Zhang and Tan’s STM, and kinematic model. The results of the analysis showed that conservative predictions by ACI 318 STM provisions were obtained for the tested deep beams. However, the ACI 318 STM did not capture the size effect. On the other hand, both Zhang and Tan’s STM and kinematic model were found to reflect the effect of beam size in their predictions.

Construction and Building Materials, 2014

h i g h l i g h t s The addition of CFRP plates has no significant effect in reducing the long te... more h i g h l i g h t s The addition of CFRP plates has no significant effect in reducing the long term deflections. Increasing the sustained load level increased immediate and long term deflections of the beams. Effective modulus analysis was found to reasonably predict the long term deflection of the beams. The Gergely and Lutz equation can be used with the EMM to predict the long term crack width of the beams.

Effect of Local Aggregate and Silica Fume on the Creep of High Performance Concrete–A Comparison with ACI and LRFD Models

In presenting the thesis in partial fulfilment of the requirements for an advanced degree at the ... more In presenting the thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I. further agree that; permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.

Journal of King Saud University - Engineering Sciences, 2003

The behavior and the appropriate Jnethod of analysis for two-way slab systems supported by a grid... more The behavior and the appropriate Jnethod of analysis for two-way slab systems supported by a grid of Inain and secondary beatns are not tttlly understood. The overall objective of this two-part study is to investigate the applicability of the ACI code Inethods for evaluation of design tTIoments for such slab systenls. This part analyzes five beam-slab-systems of ditferent configurations through the code and finite elelnent procedures. One slab systeln was without secondary beatns while the relnaining four have secondary beanls with bearing bealn-to-slab depth ratios from 2.6 to 5. The secondary beams ,,,ere found to reduce the floor weight by upto 30 % when the five slab systems were of equal stiffness. However, achieving slab-systems of equal stiffness is not straightforward and cannot be evaluated froln section properties only. It was found that derivation of equal stiftness of the slab systelns based on section properties alone resulted in an error of 38 % in computed deflection. In bealn-slab systenls~the rib projection of the beam poses a tnodeling challenge. T\vo options were considered: physical offset with rigid link option or equivalent bealn option in \vhich the size of the beam was increased to compensate for the rib otfset. In this part the stlldy~the advantages and drawbacks of both modeling approaches are discussed.

Coupled Effect of Coarse Aggregate Type and Silica Fume on Creep Coefficients of High-Strength Concrete

Journal of Materials in Civil Engineering, 2016

AbstractStandard concrete creep prediction models are essential for structural design; however, i... more AbstractStandard concrete creep prediction models are essential for structural design; however, it would be unrealistic to expect accurate prediction results without calibration and validations through experimental studies involving local materials and conditions. This paper reports on the long-term creep of high-strength concrete based on experimental work of six independent concrete mixtures involving three types of aggregate, where three mixtures of them incorporated 10% silica fume. Creep testing was conducted with consideration of standard guidelines for loading and strain measurements for up to 2.5 years. Creep coefficients computed from measured strains indicated a substantial influence of the silica fume and aggregate types. The study found that two of the examined models were capable of producing reasonable predictions of the creep for concretes without silica fume. On the other hand, the a current industry model showed reasonable prediction of the creep of concretes with silica fume while undere...

International Journal of Engineering and Technology, 2013

An experimental investigation of radiation shielding properties of high performance concretes (HP... more An experimental investigation of radiation shielding properties of high performance concretes (HPCs) was mad under effect of different variables. HPCs were produced from different normal and heavyweight aggregate with three low water-to-cementitious materials ratios (w/cm) to obtain different compressive strengths. The linear attenuation coefficients were measured at 0.663 MeV γ-rays energy of 137 Cs radioactive using NaI (Tl) scintillation detector. It was found that the compressive strength of heavyweight HPCs plays an important role in enhancing the attenuation of γ-rays. The compressive strength and attenuation of γ-rays have a near to linear relation. While in the normal concrete, the strength has no effect on the attenuation of γ-radiation. The mass attenuation coefficients were also compared with the values obtained by the United States National Institute of Standards and Technology (NIST). The comparison showed a reasonable agreement. It was observed that the attenuation of γ-rays is considerably affected by concrete density.

A New Design Methohdology for the Ultimate Capacity of Slender Prestressed Concrete Columns

Pci Journal, Feb 1, 2003

The nonlinear static analytical procedure (Pushover) as introduced by ATC-40 was applied for the ... more The nonlinear static analytical procedure (Pushover) as introduced by ATC-40 was applied for the evaluation of existing design of a reinforced concrete frame, in order to examine the applicability of the pushover for evaluating design of new buildings. Potential structural deficiencies in the frame were assessed by the code seismic-resistant design and pushover approaches, for the sake of comparison. In the first approach, the potential deficiencies were determined by redesigning under one selected seismic combination in order to show which members would require additional reinforcement. In the second approach, a pushover analysis was conducted to assess the seismic performance of the frame and detect the locations of the plastic hinges. The paper shows that vulnerability locations revealed from the two procedures are significantly different, where the latter procedure tends to overestimate column strength, consequently, concealing earlier detection of column weaknesses. The paper p...

γ-Radiation Shielding Properties of High Strength High Performance Concretes Prepared with Different Types of Normal and Heavy Aggregates

18  Abstract— This paper presents an experimental study on the gamma ray radiation shielding pro... more 18  Abstract— This paper presents an experimental study on the gamma ray radiation shielding properties of normal and heavy high performance concretes (HPCs). HPCs were produced with different low water-to-cementitious materials ratios (w/cm) and tested for 0.663 MeV γ-rays energy of 137 Cs radioactive using NaI(Tl) scintillation detector. It was observed in this research that the compressive strength of heavy HPCs plays an important role in enhancing the attenuation of gamma rays. The compressive strength and attenuation of gamma rays in heavy weight HPCs have a near to linear relation. On the other hand, it was also found that the compressive strength of the normal concrete has almost no effect on the attenuation of gamma rays. The Linear and mass attenuation coefficients were calculated and compared with the past research and a good agreement has been found. However, the HPCs density considerably affects the attenuation of gamma rays. With the increase in the density, the attenuation coefficients increases linearly. This endorse that the relationship between the HPC density and the gamma attenuation coefficients is linear.

ATINER's Conference Paper Series CIV2014-0967

Journal of Structural Engineering, 2012

This paper addressed the influence of stirrup configurations in wide beams on the effectiveness o... more This paper addressed the influence of stirrup configurations in wide beams on the effectiveness of stirrups in contributing to shear resistance as a ratio of the nominal shear stirrup strength. The evaluation was made by testing 16 continuous, wide, shallow, reinforced, concrete beams supported on interior narrow columns at their centers and simply supported at the ends. The 16 beams were composed of: three beams without stirrups, six beams having a constant amount of stirrups with either two-leg or four-leg configuration, and seven other beams with various configurations to verify the trend. The general trend is that reducing the transverse spacing of stirrups improves the stirrup efficiency to resist shear forces. For beams with a constant amount of stirrups, four-leg configuration showed a high increase in its efficiency to resist shear force over stirrups with two-leg configuration. Although code design equations assume that stirrups are fully effective, it was evident that wide shallow beams reinforced with two-leg stirrups were susceptible to becoming shear deficient if transverse spacing was not accounted for. On the basis of findings of this study, guidelines for computing the stirrup contribution in shear resistance were proposed and verified by comparisons with tested beams from the present study and a previous study by Serna-Ros et al.

Efficacy of CFRP configurations for shear of RC beams: experimental and NLFE

Structural Engineering and Mechanics, 2011

ABSTRACT This paper presents the results of an investigation on shear strengthening of RC beams e... more ABSTRACT This paper presents the results of an investigation on shear strengthening of RC beams externally reinforced with CFRP composite. A total of six full-scale beams of four CFRP strengthened and two unstrengthened were tested in the absence of internal stirrups in the shear span. The strengthening configurations contained two styles: discrete uniformly spaced strips and customized wide strips over B-regions. The composite systems provided an increase in ultimate strength as compared to the unstrengthened beams. Among the three layouts that had the same area of CFRP, the highest contribution was provided by the customized layout that targeted the B-regions. A comparative study of the experimental results with published empirical equations was conducted in order to evaluate the assumed effective strains. The empirical equations were found to be unconservative. Nonlinear finite element (NLFE) models were developed for the beams. The models agreed with test results that targeting the B-region was more effective than distributing the same CFRP area in a discrete strip style over shear spans. Moreover, the numerical models predicted the contribution of different configurations better than the empirical equations.

Computers and Concrete, 2016

This paper reports on punching shear behavior of reinforced concrete panels, investigated experim... more This paper reports on punching shear behavior of reinforced concrete panels, investigated experimentally and through finite element simulation. The aim of the study was to examine the punching shear of high strength concrete panels incorporating different types of aggregate and silica fume, in order to assess the validity of the existing code models with respect to the role of compressive and tensile strength of high strength concrete. The variables in concrete mix design include three types of coarse aggregates and three water-cementitious ratios, and ten-percent replacement of silica fume. The experimental results were compared with the results produced by empirical prediction equations of a number of widely used codes of practice. The prediction of the punching shear capacity of high strength concrete using the equations listed in this study, pointed to a potential unsafe design in some of them. This may be a reflection of the overestimation of the contribution of compressive strength and the negligence of the role of flexural reinforcement. The overall findings clearly indicated that the extrapolation of the relationships that were developed for normal strength concrete are not valid for high strength concrete within the scope of this study and that finite element simulation can provide a better alternative to empirical code Equations.

Latin American Journal of Solids and Structures, 2012

The paper presents the results of an investigation on the diagnosis and assessment of a full-scal... more 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.

Coupled effect of coarse aggregate and micro-silica on the relation between strength and elasticity of high performance concrete

Construction and Building Materials

Abstract This paper examines the relation between strength and elastic modulus of high performanc... more Abstract This paper examines the relation between strength and elastic modulus of high performance concrete (HPC) tailored from various heavy and normal weight aggregates coupled with the effect of micro-silica as a supplementary cementitious material (SCM). Elastic modulus of concrete is an important mechanical property and plays an important role for the calculation of deformations in the structural components. Experimentation was conducted in precise laboratory environment and all other parameters were kept constant in the mixtures. This investigation was prompted to supply the construction industry with appropriate information on how specific properties of HPC mixtures can be improved using local normal and heavy weight aggregates and incorporating supplementary cementitious materials. In other words, this paper will encourage the local aggregate consumption in mega projects that to be constructed for special purposes. In this investigation, dissimilar types of normal and heavy weight coarse aggregates were used. It was found that it is worthy to study experimentally the relation between strength and MOE of HPC when different types of coarse aggregates are used for an indicated HPC mixture with a corresponding combination of supplementary cementitious material. The comparison of experiment results with the ACI prediction models showed that the models should be enhanced for accurate prediction for the effect of aggregate type with and without the use of micro-silica as supplementary cementitious material. An assessment of the need for an aggregate and micro-silica based modification to the ACI models is also proposed. The experimental work conducted in this investigation confirmed that the type of aggregate and its combination with a supplementary cementitious material would have important influence on the HPC characteristics. Hence, the use of appropriate values for the strength-MOE relation for a HPC mixture based on the nature of used aggregates and SCM is recommended. However, such values might be not available in some cases, if so the experimental trend lines presented in this study can be used to calculate them.

International Journal of Concrete Structures and Materials, 2016

The resistance-demand approach has emerged as an effective approach for determining the shear cap... more The resistance-demand approach has emerged as an effective approach for determining the shear capacity of reinforced concrete beams. This approach is based on the fact that 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. This paper verifies the applicability of resistance-demand procedure for predicting the shear capacity of high strength concrete beams without web reinforcement. A total of 18 beams were constructed and tested in four-point bending up to failure. The test variables included the longitudinal reinforcement ratio, the shear span to depth ratio, and the beam depth. The shear capacity of the beams was predicted using the proposed procedure and compared with the experimental values. The results of the comparison showed good prediction capability and can be useful to design practice.

Experimental verification of strut and tie model for HSC deep beams without shear reinforcement

Engineering Structures, 2016

Influence of Stirrup Corrosion on Shear Strength of Reinforced Concrete Slender Beams

ACI Structural Journal, 2016