Influence of section depth on the structural behaviour of reinforced concrete continuous deep beams

YesAlthough the depth of reinforced concrete deep beams is much higher than that of slender beams, extensive existing tests on deep beams have focused on simply supported beams with a scaled depth below 600 mm. In the present paper, test results of 12 two-span reinforced concrete deep beams are reported. The main parameters investigated were the beam depth, which is varied from 400 mm to 720 mm, concrete compressive strength and shear span-tooverall depth ratio. All beams had the same longitudinal top and bottom reinforcement and no web reinforcement to assess the effect of changing the beam depth on the shear strength of such beams. All beams tested failed owing to a significant diagonal crack connecting the edges of the load and intermediate support plates. The influence of beam depth on shear strength was more pronounced on continuous deep beams than simple ones and on beams having higher concrete compressive strength. A numerical technique based on the upper bound analysis of the plasticity theory was developed to assess the load capacity of continuous deep beams. The influence of the beam depth was covered by the effectiveness factor of concrete in compression to cater for size effect. Comparisons between the total capacity from the proposed technique and that experimentally measured in the current investigation and elsewhere show good agreement, even though the section depth of beams is varied

NUMERICAL SIMULATION OF CONCRETE BEAMS WITH DISCONTINUITY REGIONS REINFORCED WITH NONMETALLIC REINFORCING BARS

Nonmetallic Glass Fiber-Reinforced Polymer (GFRP) reinforcing bars are considered a viable alternative to the conventional steel reinforcement because of their high strength-to-weight ratio and noncorrosive nature. This research aimed to investigate the nonlinear structural behavior of GFRP-reinforced concrete beams with discontinuity regions (D-regions) through numerical analysis. Three-dimensional (3D) numerical models were developed to simulate the nonlinear structural behavior of GFRP-reinforced deep beams with and without web openings. The models adopted realistic constitutive laws that accounted for the nonlinear behavior of the materials used. Predictions of the numerical models were validated against published experimental data. A parametric study was conducted to examine the effect of key variables on the structural behavior of GFRP-reinforced deep beams with and without web openings. The interaction between the concrete compressive strength (fc’), shear span-to-depth ratio (a/h), size and location of the web opening was elucidated. Simplified analytical formulas capable of predicting the shear capacity of GFRP-reinforced beams with D-regions were introduced based on an inverse analysis of results of the numerical simulation models. Predictions of the proposed analytical formulas were in good agreement with the results of the simulation models

Dynamic displacement analysis of reinforced concrete deep beams made of high strength concrete. Part III: Analysis of dynamic displacement of a reinforced concrete deep beam made of high strength C300 grade concrete

This work demonstrates an analysis of the displacement state of rectangular concrete deep beams made of very high strength concrete grade C300 under a dynamic load, including the physical nonlinearity of construction materials: concrete and reinforcing steel. The analysis was conducted with the method presented in [1]. Numerical solution results are presented with particular reference to the displacement state of a rectangular concrete deep beam. The work confirmed the accuracy of the assumptions and deformation models of concrete and steel as well as the effectiveness of the methods of analysis proposed in the paper [1] for the problems of numerical simulation of the behaviour of reinforced concrete deep beams under dynamic loads. A comparative analysis was conducted on the effect of the high-strength concrete and the steel of increased strength on the displacement of a grade C300 concrete deep beam vs. the results produced in [10] for grade C100 and C200 concrete deep beams. Keywords: mechanics of structures, reinforced concrete structures, deep beams, dynamic load, physical nonlinearity

Estimate of dynamic load capacity of reinforced concrete deep beam made of very high strength construction materials

The paper presents an analysis of the dynamic load capacity of a dynamically loaded rectangular reinforced-concrete deep beam made of high-strength materials, including the physical nonlinearity of the construction materials: concrete and reinforcing steel. The solution was acquired with the use of the method presented in [15]. The dynamic load capacity of the reinforced concrete beam was determined. The results of numerical solutions are presented, with particular emphasis on the impact of the very high strength of concrete and steel on the reinforced concrete beam’s dynamic load capacity. The work confirmed the correctness of the assumptions and deformation models of concrete and steel as well as the effectiveness of the methods of analysis proposed in the paper [1, 15] for the problems of numerical simulation of the behaviour of reinforced concrete deep beams under dynamic loads. Keywords: mechanics of structures, reinforced concrete structures, deep beams, dynamic load, physical nonlinearity

Dynamic displacement analysis of reinforced concrete deep beams made of high strength concrete. Part II: Dynamic displacement analysis of reinforced concrete deep beams made of high strength C200 grade concrete

The dynamic load displacements were analysed of rectangular concrete deep beams made of very high strength concrete, grade C200, including an evaluation of the physical non-linearity of the construction materials: concrete and reinforcing steel. The analysis was conducted using the method presented in [1]. The numerical calculation results are presented with particular reference to the displacement state of rectangular concrete deep beams. A comparative analysis was conducted on the effect of the high-strength concrete and the steel of increased strength on a class C200 concrete deep beam versus the results produced in [10] for a class C100 concrete deep beam. Keywords: mechanics of structures, reinforced concrete structures, deep beams, dynamic load, physical non-linearit

MODIFIED FIXED-ANGLE STRUT-AND-TIE MODEL FOR HIGH STRENGTH REINFORCED CONCRETE BEAMS

Nonlinear finite element analysis was applied to various reinforced concrete beams using a set of constitutive models established in the modified fixed-angle softened-truss model (MFA-STM). The model was implemented by modifying the general-purpose program FEAPpv. The model can take account of the six important characteristics of cracked reinforced concrete: (1) the softening effect of concrete in tension-compression; (2) the tension-stiffening effect of concrete in tension; (3) the average stress-strain curve of steel bars embedded in concrete; (4) the shear modulus of concrete; (5) the aggregate interlock; and (6) dowel action. The comparison shows the aggregate interlock and dowel action can reduce the overestimation of the shear capacity of high strength reinforced beam, especially the high strength reinforced deep beam without web reinforcement. Moreover, the model is suitable for being implemented numerical procedures due its simplicity

Effect of Size and Location of Square Web Openings on the Entire Behavior of Reinforced Concrete Deep Beams

This paper presents an experimental and numerical study which was carried out to examine the influence of the size and the layout of the web openings on the load carrying capacity and the serviceability of reinforced concrete deep beams. Five full-scale simply supported reinforced concrete deep beams with two large web openings created in shear regions were tested up to failure. The shear span to overall depth ratio was (1.1). Square openings were located symmetrically relative to the midspan section either at the midpoint or at the interior boundaries of the shear span. Two different side dimensions for the square openings were considered, mainly, (200) mm and (230) mm. The strength results proved that the shear capacity of the deep beam is governed by the size and location of web openings. The experimental results indicated that the reduction of the shear capacity may reach (66%). ABAQUS finite element software program was used for simulation and analysis. Numerical analyses provided un-conservative estimates for deep beam load carrying capacity in the range between (5-21%). However, the maximum scatter of the finite element method predictions for first diagonal and first flexural cracking loads was not exceeding (17%). Also, at service load the numerical of midspan deflection was greater than the experimental values by (9-18%)

Steel fibres for the shear resistance of high strength concrete beams

Available research on the use of steel fibres to increase the shear resistance of concrete structures shows that the effectiveness of this type of reinforcement increases with the increase of the concrete compressive strength, as long as the fibre rupture is avoided. Experimental research has also indicated that the effectiveness of the fibre reinforcement for the shear resistance is more pronounced in shallow beams than in deep beams. In terms of analytical research, some models have been proposed and, recently, RILEM TC 162 TDF recommended an analytical approach for the prediction of the fibre reinforcement contribution in terms of shear resistance of concrete beams. The present work has the purpose to contribute for this topic, discussing the performance of RILEM TC 162 TDF approach, by using the results obtained in an experimental program composed of three point bending tests with shallow beams of high strength concrete (HSC). Six different HSC compositions were developed, varying the dosage of steel fibres (0, 60 and 75 kg/m3) and concrete strength class. The experimental program also included tests to characterize the flexural behaviour of the developed high strength steel fibre reinforced concrete (HSSFRC). Using the force-deflection relationships obtained in the three point-notched beam bending tests, and performing an inverse analysis, the values of the fracture mode I parameters of the HSSFRC were determined. These values were used on the numerical simulation of the tests carried out with HSSFRC beams failing in shear, under the framework of the material nonlinear finite element analysis, in order to evince the influence of using a softening constitutive law for modeling the crack shear sliding. In the present work, the experimental program and the numerical research are described, and the main results are presented and discussed.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/57518/2004 “FICOFIRE : High performance fiber reinforced concrete of enhanced fire resistance

Inclined reinforcement around web opening in concrete beams

YesTwelve reinforced-concrete continuous deep beams having web openings within interior shear spans were tested to failure. The main variables investigated were the opening size and the amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the amount of inclined web reinforcement and opening size is proposed and used to analyse the structural behaviour of continuous deep beams tested. It was observed that the end support reaction, diagonal crack width and load capacity of beams tested were significantly dependent on the proposed effective inclined reinforcement factor. As this factor increased, the end support reaction and increasing rate of diagonal crack width were closer to those of companion solid deep beams. In addition, a higher load capacity was exhibited by beams having an effective inclined reinforcement factor above 0.077 than the companion solid deep beam. A numerical procedure based on the upper-bound analysis of the plasticity theory was proposed to estimate the load capacity of beams tested. Comparisons between the measured and predicted load capacities showed good agreement

Influence of inclined web reinforcement on reinforced concrete deep beams with web openings.

yesThis paper reports the testing of fifteen reinforced concrete deep beams with openings. All beams tested had the same overall geometrical dimensions. The main variables considered were the opening size and amount of inclined reinforcement. An effective inclined reinforcement factor combining the influence of the amount of inclined reinforcement and opening size on the structural behaviour of the beams tested is proposed. It was observed that the diagonal crack width and shear strength of beams tested were significantly dependent on the effective inclined reinforcement factor that ranged from 0 to 0.318 for the test specimens. As this factor increased, the diagonal crack width and its development rate decreased, and the shear strength of beams tested improved. Beams having effective inclined reinforcement factor more than 0.15 had higher shear strength than that of the corresponding solid beams. A numerical procedure based on the upper bound analysis of the plasticity theory was proposed to estimate the shear strength and load transfer capacity of reinforcement in deep beams with openings. Predictions obtained from the proposed formulas have a consistent agreement with test results