Serviceability behavior of normal and high-strength reinforced concrete t-beams

Serviceability behavior of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) T-beams was experimentally evaluated. The crack pattern was observed, the effect of flange dimensions (breadth and thickness) on the crack pattern and load-deflection response was evaluated experimentally for 10 beams comprising the two studied groups, NSC and HSC T-beams. The short-term deflections were measured experimentally and predicted empirically under mid-span concentrated loading. It was found that increasing the flange width and thickness resulted in higher loads and lower deflections under service loads to a different extent. Prior to failure, the increment in the maximum loads was up to 22% while the deflection reduced by 31% for NSC and 23% for HSC beams. The available equations for determining the effective moment of inertia (Ie) were reviewed and used in predicting the Ie of the cracked beam. The results were compared with the experimental values (Iexp). The Ie showed a noticeable difference, especially for the HSC T-beams. New equations were proposed in which the tensile reinforcement ratio was considered. Compared with the other available equations, the proposed equations demonstrated a better agreement and repeatability of predicting experimental results studied herein. In addition, the proposed equations were used to predict the Ie for experimentally tested T-beams available in the literature. The proposed models showed a high degree of accuracy

Shear behavior of reinforced concrete continuous deep beams

Test results of nine reinforced concrete continuous deep beams are presented and analyzed. The main variables studied were shear span-to-depth ratio (a/d), vertical web reinforcement ratio (ρv), horizontal web reinforcement ratio (ρh), and concrete compressive strength (fcu). The results of this study show that the stiffness reduction was prominent in case of lower concrete strength and higher shear span-to depth ratio and that the variation of strains along the main longitudinal top and bottom bars was found to be dependent on the shear span-to depth ratio. For beams having small (a/d) ratio, horizontal shear reinforcement was always more effective than vertical shear reinforcement. Finally, the obtained test results are compared to the predictions of finite element analysis using the ANSYS 10 program and a well agreement between the experimental and analytical results was found

Shear behavior of high strength fiber reinforced concrete beams under different levels of axial compression forces

This study is part of a larger research work aimed to study the effects of fiber content, fiber type (corrugated shape and hooked-end), amount of web reinforcement and axial compression stress, on the shear behavior of high strength fiber reinforced concrete (HSFRC) beams. To the author’s knowledge, the effect of applying axial compression forces, to the HSFRC beams, has not yet been studied. Nineteen simply supported HSFRC beams were subjected to axial compression forces and tested under two-point vertical loading for three values of shear span to depth ratio. It was found that the shear strength of beams subjected to axial compression stress level equals 0.1, is higher than that in the literature for beams tested without applying axial stress by a range of 22% -98%. Increasing the axial compression stress level to 0.2 led to an increase in the first crack load, ultimate load by 24% and 10%, a reduction in the deflection by (19-30%), compared with those subjected to axial compression stress level equals 0.1. In addition, a combination of web reinforcement and fibers resulted in a significant increase in the cracking and ultimate loads by 123 and 59%, respectively, over those of the reference beam. A new formula is proposed for predicting the experimental shear strength of HSFRC beams subjected to axial compression forces. The results obtained by the proposed formula are in better agreement with the test results when compared with the predictions based on the empirical equations proposed by other investigators

Analysis of reinforced concrete slabs on grade in industrial buildings

Aim： A parametric study was conducted to investigate the theoretical behaviour of industrial slab on grade to industrial trucks with single wheel axles loading Objective： 1. Applying NLFEA to study the structural response of industrial slab on grade to lift trucks with single wheel axle loading 2. The studied parameters were the load position in relation to slab edges, slab proportions, reinforcement content and its method of arrangement, and the modulus of subgrade reaction 3. The subgrade was represented by boundary spring elements of a non tension feature to simulate the soi

Behaviour and analysis of reinforced concrete continuous deep beams

Test results of nine reinforced concrete continuous deep beams are presented and analyzed. The main variables studied were shear span-to-depth ratio (a/d),vertical web reinforcement ratio (ρv), horizontal web reinforcement ratio (ρh), and concrete compressive strength (fcu). The results of this study show that the stiffness reduction was prominent in case of lower concrete strength and higher shear span-to depth ratio and that the variation of strains along the main longitudinal top and bottom bars was found to be dependent on the shear span-to depth ratio. For beams having small (a/d) ratio, horizontal shear reinforcement was always more effective than vertical shear reinforcement. Finally, the obtained test results are compared to the predictions of finite element analysis using the ANSYS 10 program and a well agreement between the experimental and analytical results was found

Educating engineering students in Egypt: recommendations for improvement

Egyptian schools of engineering (government faculties, private faculties and private higher engineering institutes) award degrees to 35000 graduates annually. There have been concerns from the Egyptian Engineers Syndicate, experienced engineers, local & international employers, parents and other society stakeholders about the knowledge and skills gained by engineering graduates. In this article, first the institutions were analyzed from a fresh business perspective. The analysis highlighted several constraints that hinder radical reforms. In part two of this article the aspirations of stakeholders were collected and identified. In part three, recommendations were made based on the experiences of engineering education providers worldwide

Experimental behavior of full-scale exterior beam-column space joints retrofitted by ferrocement layers under cyclic loading

A majority of the traditional reinforced concrete frame buildings, existing across the Middle East, lack adequate confinement in beam-column joints, or in other words, are shear deficient because they were constructed before the introduction of seismic codes for construction. This research studies the experimental behavior of full-scale beam-column space (three-dimensional) joints under displacement-controlled cyclic loading. Eleven joint specimens, included a traditionally reinforced one (without adequate shear reinforcement), a reference one with sufficient shear reinforcement according to ACI 318, and nine specimens retrofitted by ferrocement layers, were experimentally tested to evaluate a retrofit technique for strengthening shear deficient beam column joints. The studied variables were the number of layers, orientation angle of expanded wire mesh per layer, and presence of steel angles in the corners of joint specimen prior to wrapping with ferrocement layers. The experimental results showed that proper shear reinforcement for the test joints, according to ACI 318, enhanced the behavior of the specimen over that of the traditionally reinforced specimens without adequate shear reinforcement. The joints retrofitted by ferrocement layers showed higher ultimate capacity, higher ultimate displacement prior to failure (better ductility), and they did not suffer heavily damage as observed for the traditionally reinforced one. Increasing the number of ferrocement layers for retrofitted specimens led to improving performance for such specimens compared to the traditionally reinforced ones in terms of enhancing the ultimate capacity and ultimate displacement. Specimens retrofitted by ferrocement layers reinforced by expanded wire mesh of 60° orientation angle showed slightly better performance than those of 45° orientation angles. Retrofitting using steel angles in addition to ferrocement layers improves the seismic performance of the specimens, achieves better stability for stiffness degradation, attains higher capacity of the dissipated energy, and reduces the vulnerability of joints to excessive damage. Based on the experimental work in this study, it is recommended to retrofit beam-column joint specimens by two ferrocement layers in addition to steel angles as stiffeners taking the orientation angle of expanded wire mesh into consideration. Keywords: Retrofitting, Beam-column space joints, Ferrocement layers, Orientation of expanded wire mesh, Ultimate capacity, Stiffness degradation, Cyclic loading, Shear deficient, Traditionally reinforced building

Strengthening of reinforced concrete slab-column connection subjected to punching shear with FRP systems

This study aims to determine the efficiency of using Fiber Reinforced Polymers (FRP) systems to strengthen the slab–column connections subjected to punching shear. The used strengthening systems consisted of external FRP stirrups made from glass and carbon fibers. The stirrups were installed around the column. Also, external steel links were used as a conventional strengthening method for comparison. Over the last few years, the use of FRP for strengthening of concrete structures has been investigated by many researchers, whichconcerning with the strengthening of reinforced concrete slabs, beams and columns. The use of FRP in strengthening concrete slabs in flexure is done by bonding it to the tension face of the slabs. The use of FRP for strengthening the flat slabs against punching shear can be considered as a new application. This research shows the results obtained from an experimental investigation of 4 half-scale two-way slab-column interior connections, which were constructed and tested under punching shear caused by centric vertical load. The research included one unstrengthened specimen, which considered as control specimen, one specimen strengthened with steel links, one specimen strengthened with external stirrups made from Glass Fiber Reinforced Polymer (GFRP), and one specimen strengthened with external stirrups made from Carbon Fiber Reinforced Polymer (CFRP). So, the type of strengthening material is the basic parameter in this study. The experimental results showed a noticeable increase in punching shear resistance and flexural stiffness for the strengthened specimens compared to control specimen. Also, the strengthened tested slabs showed a relative ductility enhancement. Finally, equations for punching shear strength prediction of slab-column connections strengthened using different materials (Steel, GFRP & CFRP) were applied and compared with the experimental results

Studies on new antifreeze protein from the psychrophilic diatom, Fragilariopsis cylindrus

Antifreeze proteins (AFPs) are found in a wide range of species including fishes, plants, etc. They have very characteristic feature that inhibit the growth and recrystallization of ice that forms in intercellular spaces. Two expressed sequence tags (ESTs) were previously identified from salt stress cDNA library in Fragilariopsis cylindrus to have similarities with snow mold AFP. Using bioinformatics tools, we analysed these two AFP-ESTs. Accordingly, by using specially designed primers, the open reading frames (ORFs) subcloned into bacterial and plant expression vectors. The predicted gene product, AfpA, had a molecular mass of 27 kDa. Expression of afpA in Escherichia coli yielded an intracellular 27-kDa protein modified with His-tag. According to bioinformatics data, a comparison between AFP-A and carrot AFP has been carried out.Key words: Antifreeze protein, Fragilariopsis cylindrus, recrystallization inhibition

Absorption and sorptivity of cover concrete

The absorption characteristics and sorptivity of cover concrete obtained by the initial surface absorption test (ISAT), the covercrete absorption test (CAT), and the sorptivity test have been studied and compared. Two types of concrete, namely ordinary portland cement (OPC) control and low water concrete (LWC) of grade 35 have been tested. The laboratory work has shown close agreement between the ISAT and sorption results but the CAT yields higher results. An analytical model has been developed based on the mechanisms of capillary suction and pressure-driven flow, In this model water entering concrete during the tests is assumed to be concentrated in a well-defined volume. This volume is fully saturated and is separated from the surrounding concrete by a wetting front at which capillary suction occurs. By applying the physical equations for capillary suction pressures and permeability the experimental. results are explained in terms of the basic properties of the concrete. The model gives good agreement with the experimental results