Reinforced Concrete Circular T-Shaped Deep Beams – Finite Element Investigation

The current work investigates the behavior and strength of T-shaped cross section ring deep beams through a Finite element parametric study. Currently, ring diameter, loading type, concrete compressive strength and number of supports are taken into consideration. It is found that increasing ring diameter of beam by 12.5-25% leads to increase the maximum positive moment, maximum negative moment, maximum torsional moment and midspan deflection by 1.1-2.2%, 2.2-4.3%, 3-6% and 16-33%, respectively, while the load ultimate capacity increases by 11-17%. The positive and torsional moments at midspan and midspan deflection decrease by 23-36%, 3-11% and 6-14%, respectively when the loading type varies from concentered to full uniformly load over a span length of 33, 50, 67 and 100%, respectively. In a related context, this change in load type leads the negative moment at support and the load ultimate capacity to increase by 2-21% and 6-85%, respectively. The midspan positive moment, negative moment, torsional moment and load ultimate capacity increase by 20.4-71.3%, 20-69.7%, 15.6-43.8% and 21-73%, respectively, whereas deflection decreases by 1.4-11%, when increasing the compressive concrete strength by 45-190%. Finally, it is found that the load ultimate capacity increases by 82-348%, when number of supports increases by 25-100%, while torsional moment, maximum positive moments, maximum negative moments and midspan deflection decrease by 11-50%, 38-76.4%, 38.6-76.8% and 14-39%, respectively due to this increase in the number of supports.

Elastic Analysis of Steel-Concrete Composite Beams with Partial Interaction

The paper presents an exact analytical method for the elastic analysis of steel-concrete composite beams with partial interaction. Accepting the basic assumptions of the Newmark analytical model and adopting the axial force in the concrete slab as the main unknown, the second order nonhomogeneous differential equation of the steel-concrete composite element with partial interaction is derived. Further, the complete solutions for simply supported and fixed-ended composite beams subjected to concentrated and uniform loads respectively, are developed. The solution of the homogeneous equation is determined by imposing proper Dirichlet or Neumann boundary conditions depending on the static scheme of the element. The particular solutions are then derived for the considered loading conditions. It is shown that the internal axial force in concrete slab associated to composite beams with partial interaction can be expressed as a fraction of the axial force in concrete slab under full interaction through a non-dimensional function f(aL) which takes into account the connection’s stiffness, the mechanical properties and also the length of the element. Moreover, the solutions are included in a flexibility-based approach to derive the force-displacement relations of the beam element with partial interaction. For the resulted 2-noded beam-column element with 6DOF, the stiffness matrix is derived, showing that the partial composite action may be included at the element level by means of a series of correction factors applied to the standard full-interaction stiffness matrix coefficients. A numerical example is provided to demonstrate the accuracy and performance of the proposed method. Within the elastic range, the predicted load-midspan deflection curve is in very good agreement with both experimental and other numerical results retrieved from international literature. A parametric study was conducted to investigate the influence of the shear connection degree on the beam’s midspan deflection and the results were compared with those computed by using code provisions.

Reinforced Concrete Semi Circular Deep Beams - Finite Element Investigation

This paper represents a parametric study utilizing finite element analysis for twenty-five reinforced concrete semi-circular deep beams. The parameters that were taken into consideration in the current work are radius, height, width, concrete compressive strength and number of supports. It is found that decreasing radius of beam by 16-66% leads to decrease the midspan positive moment, support negative moment, torsional moment and midspan deflection by about 0.3-20%, 2.4-25%, 2-24% and 29-85%, respectively, while the load capacity increases by about 23-158%. The midspan positive moment, support negative moment, torsional moment and load capacity increase by about 20-682%, 20-81%, 20-81% and 21-84%, respectively, whereas midspan deflection decreases by 7-17% when the beam height increases by about 16-66%. The positive moment, negative moment, torsional moment and load capacity increases by about 43-197%, 40-185%, 29-187% and 46-214%, respectively, whereas deflection decreases by about 1.4-3.3% when the beam width increases by about 16-66%. The positive moment, negative moment, torsional moment and load capacity increases by about 10-84%, 9-77%, 9-79% and 11-92%, respectively, whereas deflection decreases by about 0.1-0.5% when the compressive strength increases by 20-220%. Finally, it is found that the positive moment increases by about 36-47% when number of supports increased by 33-66%, while the negative moment increases by about 16-31% when number of supports decreases by 14-29%, whereas the torsional moments and deflection decreases by about 6-55% and 37-84%, respectively when number of supports increases by 33-133%, while load capacity increases by 156-969% when number of support increases by 33-133%.

Mechanical and Self-Sensing Properties of Multiwalled Carbon Nanotube-Reinforced ECCs

This paper investigates the effect of type and dosage of multiwalled carbon nanotubes (MWCNTs) on the mechanical and self-sensing properties of engineered cementitious composites (ECCs). Two types of MWCNTs (MWCNTa and MWCNTb) were employed. The tensile and flexural strengths of CNT-reinforced ECCs were improved compared with normal ECCs, while the ultimate tensile strain and midspan deflection were reduced. Compared with the dosage of MWCNTs, the type had less effect on these properties. The percolation threshold was around 0.3 wt.%. ECCs containing MWCNTs had good self-sensing ability under different loading conditions. When the midspan deflection increased from 0.1 to 0.6 mm, the fractional change in resistivity reached 9%. The dosage of MWCNTs had a significant effect on the self-sensing ability. As the MWCNT content increased, the amplitude of fractional change in resistivity decreased.

Peak Response Prediction for RC Beams under Impact Loading

In this paper, a novel and simple method for predicting the peak response of RC beams subjected to impact loading is proposed. The theoretical basis for calculating the peak impact force originates from the contact law, the principle of conservation of energy, the impulse-momentum theorem, and the wave theory. Additionally, the conventional beam theory, in conjunction with the well-known layered-section approach, is utilized to obtain the force-deflection relationship of the RC beam. Subsequently, by taking into account the strain rate effect, the maximum midspan deflection of RC beams under impact loading is determined based on the conservation of energy approach. A comparison with 143 impact tests has shown that the proposed method is able to estimate the maximum midspan deflection of RC beams under impact loading with high accuracy. The prediction of the peak impact force is shown to be slightly overestimated, which however can be used in the anti-impact design to preclude the shear failure near the impact point.

Performance of RC Beams with Embedded Steel Trusses Using Nonlinear FEM Analysis

The current study investigates the shear performance of reinforced concrete (RC) beams with embedded steel trusses at small shear span to depth ratios a/d using nonlinear finite element (FE) model. Twenty-one (FE) models have been built using ABAQUS software to investigate the effect of different a/d ratios and web reinforcement on the shear performance and failure load of RC beams with embedded steel trusses. This research focuses on obtaining failure loads, failure modes, crack propagation, and midspan deflection from the developed FE models. The numerical results indicated that, using RC beams with embedded truss with different a/d ratios increased significantly the ultimate shear strength compared with the common RC beams. Furthermore, the numerical results confirmed that embedment of steel trusses in RC beams would significantly improve the structural behavior of RC beams at different a/d ratios. In addition, the results indicated that the shear reinforcement has a small effect on failure and midspan deflection of RC beams with embedded angle trusses at different a/d ratios.

Strength and Serviceability of Reinforced Concrete Deep Beams with Large Web Openings Created in Shear Spans

Deep beams are used in wide construction fields such as water tanks, foundations, and girders in multi-story buildings to provide certain areas free of columns. In practice it is quite often occurring to create web opening in deep beams to supply convenient passage of ventilation ducts, cable channels, gas and water pipes. Experimental studies of ten 10 deep beams were carried out, where two of them are control specimens without openings and eight with large web openings in the shear spans. The variables that have been adopted are the ratio of the shear span to the overall depth of the member cross-section, location and dimensions of the opening. Test results showed that there was a decrease in the load carrying capacity of deep beams with openings compared to the control deep beams. This reduction may reach 66% in particular cases. It is clear that, the position of opening in shear span has less effect on the performance of structural concrete deep beams at different serviceability stages. Only 11% increase in load capacity at failure was observed in specimens with openings adjacent to the interior edges of shear spans in comparison with specimens with openings at the center of shear span because the discontinuity of the load path is less. Also the midspan deflection at service load level of the reference beam in specimens with openings adjacent to interior edge of shear spans was less than the midspan deflection of reference specimens by 10% - 33%. Evaluating all these advantages facilitates to recommend, if it is very required, the creation of openings at the interior edges of shear spans of the structural concrete deep beams.

Corrosion Effects on Residual Structural Capacity of Resins / Exudates Inhibited Steel Reinforcement Flexural Beam

The study investigated the effects of corrosion on the residual structural steel bar capacity of resins/exudates inhibited and non-inhibited reinforced concrete beam members. Steel reinforcements were coated with moringa oleifera lam resins/exudates from trees extract (Inorganic inhibitors), embedded into concrete beam members and exposed to sodium chloride medium representing laboratory harsh saline marine environment. Corrosion acceleration potential test was conducted on 27 samples of non-corroded, uncoated and coated resins/exudates paste thicknesses of steel bar and simulated for 60 days, after 30 days, initial concrete cured. Results obtained showed corrosion potential presence on uncoated members with cracks and spalling. Further recorded results on non-corroded flexural strength test of failure load 29.09%, midspan deflection 28.30%, tensile strength 12.03% and elongation 31.50%, for coated beam members, failure load 29.42%, midspan deflection 27.42%, tensile strength 12.09% and elongation 31.80%, for corroded beam members, failure load decreased by 22.50%, midspan deflection increased by 39.30%, tensile strength decreased to 10.17% and elongation by increased 46.30%. The entire experimental results showed that corroded specimens has lower flexural load, higher midspan deflection, lower tensile strength and higher elongation due to loss of steel bar fibre from degradation effect from corrosion, inhibitors served as protective coating against corrosion, but no strength was added to steel members.

Retrofitting of shear strength self-compacting reinforced concrete deep beams with FRP

Experimental program were carried out to investigate the behavior of self-compacting reinforced concrete deep beams retrofitting with carbon fiber reinforced polymer (CFRP). Six simply supported deep beams were tested under symmetrically two point loads, three beams were tested up to failure without strengthening as a control beams with different shear span to effective depth ratio (a/d) while the other two beams were loaded up to 60% from the ultimate load of control beams for each a/d ratio and then retrofitted by the same configuration of CFRP to study the effect of a/d ratio on the properties of deep beams retrofitted. a/d for tested beams were (0.8, 1, 1.2). Study was focused on determining failure loads, cracking loads, failure modes, load midspan deflection. All the beams had the same compressive strength, overall dimensions and flexural and shear reinforcement. It was concluded that using this retrofitted method is very efficient and a gain in the ultimate load capacity of the deep beams was obtained also the results showed that when a/d ratio increase from 0.8 to 1.2, the ultimate load was decrease by 25% and midspan deflection was increased approximately at all load stages for control and retrofitted beams.