Concrete T-beams Research Articles

Finite Element Analysis of Reinforced Concrete T-Beams with Multiple Web Openings under Impact Loading

In this study, a three-dimensional finite element analysis using ANSYS 12.1 program had been employed to simulate simply supported reinforced concrete (RC) T-beams with multiple web circular openings subjected to an impact loading. Three design parameters were considered, including size, location and number of the web openings. Twelve models of simply supported RC T-beams were subjected to one point of transient (impact) loading at mid span. Beams were simulated and analysis results were obtained in terms of mid span deflection-time histories and compared with the results of the solid reference one. The maximum mid span deflection is an important index for evaluating damage levels of the RC beams subjected to impact loading. Three experimental T-beams were considered in this study for calibration of the program. All models had an identical cross-section and span similar to those of the experimental beams. The diameter of the openings of the experimental beams was 110 mm. Three other diameters were varied (50, 80 and 130) mm. The location of the face of the opening with respect to the location of impact loading was investigated (the face of the opening at distance varied 0d, 0.5d, 1d and 1.5d from the location of loading, where d is the effective depth) and the number of web openings was varied (2,4 and 6) openings. All modeled beams subjected to dropping mass of 24.5 kg with height of drop of 250 mm (as for the experimental beams). Results obtained from this study showed that the behavior of beams with circular openings of diameter equal to 22% the web depth has a small effect on the response of the RC T-beams. On the other hand, introducing circular openings with a diameter equal to 35% and 57% of the web depth (80 and 130 mm) increases the maximum mid span deflection by 23% and 43% respectively. Results also showed that, openings with a distance greater than or equal to 1.5 d from the location of impact loading have no effect on the deflection of the RC beams.

Numerical Analysis of Delamination of High-Performance Concrete (HPC) Strengthened Reinforced Concrete (RC) Beam

Abstract This study investigates the numerical analysis of delamination behavior of high-performance concrete (HPC) strengthened reinforced concrete (RC) cantilever T-beam by using finite element method. A length of 1000 mm reinforced concrete cantilever T-beam and height of 1600 mm reinforced concrete column will be created. Besides that, the truss members such as the stirrups and the rebars will also be added into the structure as a reinforcement. The HPC layer will be assigned on the top of the cantilever T-beam as a coating material. The study is to investigate the influences on the delamination behavior when the thickness, width, and coefficient of friction of the HPC layer has been applied on the model as a coating material. Finite element model (FEM) will need to be created and justified in ABAQUS software before applying the parameters for analysis. Limited studies had been conducted on the delamination behavior of using HPC layer as a strengthening mechanism and analyze the output such as the COPEN and SDEG. Based on the results extracted from the software, the delamination behavior can be observed and analyzed and investigate the influence of difference parameter has been assigned. Therefore, this research paper will analyze the influence of the layer thickness, width of the layer, and the coefficient of friction between the substrate and the layer.

Experimental analysis of the shear resistance of precast concrete T-beams with a top cast-in-place slab

Precast concrete T-beams with a cast-in-place slab on top are structural elements that are often employed in composite construction. Despite their widespread use, some aspects of their structural behaviour upon shear forces have not yet been studied in depth. Six composite specimens with different T-shaped cross-sections and concrete qualities, and with web reinforcement, were tested to analyse the shear transfer mechanisms and to assess the contribution of the cast-in-place slab to shear strength. The shear strength mechanisms deriving from experimental observations and measurements are provided. This study indicates that: placing a concrete cast-in-place slab on top of a prefabricated T-beam increases its shear strength; interface shear strength plays an essential role in concrete composite elements’ vertical shear strength; widening the cast-in-place slab width does not increase shear strength in this test programme specimens; the compressive strength of the precast beam’s concrete significantly influences composite beams’ shear resistances. The ACI 318-19 formulation best captures the influence of concrete strength on shear strength of the three formulations considered (EC2, MC-10 (Level III) and ACI 318-19). However, all of them tend to underestimate shear strengths compared to the experimental results.

Numerical Investigation of Flexural Behavior of Reinforced Concrete (RC) T-Beams Strengthened with Pre-Stressed Iron-Based (FeMnSiCrNi) Shape Memory Alloy Bars

Shape memory alloy (SMA) is a material that can change shape in response to external stimuli such as temperature, stress, or magnetic fields. SMA types include nitinol (nickel-titanium), copper-aluminum-nickel, copper-zinc-aluminum, iron-manganese-silicon, and various nickel-titanium-X alloys, each exhibiting unique shape memory properties for different applications. Reinforced concrete (RC) T-beams strengthened and pre-stressed with Fe-SMA bars are numerically investigated for their flexural response under the influence of various parameters. The bars are embedded in a concrete layer attached to the beam’s soffit. Based on the numerical results, it was found that increasing the compression strength from 30 to 60 MPa slightly improves the beam’s strength (by 2%), but it significantly increases its ductility by approximately 45%. As opposed to this, the strength and ductility of the pre-stressed T-beam are considerably improved by using a larger diameter of Fe-SMA bars. Specifically, using 12 mm Fe-SMA bar over 6 mm resulted in 65% and 47% greater strength and ductility, respectively. Furthermore, this study examines the importance of considering the flange in the flexural design of pre-stressed beams. It is seen that considering a 500 mm flange width enhanced the ductility by 25% compared to the rectangular-section beam. The authors recommend further experimental work to validate and supplement the calculations and methodology used in the current numerical analysis.

Shear behavior of prestressed concrete T-beams strengthened by steel plate-concrete composite

The shear performance of prestressed concrete T-beam strengthened by steel plate-concrete composite is experimentally and numerically investigated in this research. Two specimens are designed and tested before and after strengthening. It is observed that the shear performance and ductility of the strengthened specimen are improved. Failure of the strengthened specimen is caused by the detachment of the strengthening portion. Nonlinear finite element models are developed and benchmarked with test results. Parametric analysis is conducted to study the effect of the connection strength and material strength. It is found that the shear strength of the member increases with increasing connection strength, while the strength of the grout concrete and steel plate also affects the shear strength. The test results and finite element results show that the proposed strengthening technique effectively improves the shear performance of the specimen, and its improvement effect is governed by the connection strength between the existing and grout concrete.

Influence of flanges geometry on the shear behavior of reinforced concrete inverted T-beams

Influence of flanges geometry on the shear behavior of reinforced concrete inverted T-beams

Employing Carbon Fiber Reinforced Polymer Composites toward the Flexural Strengthening of Reinforced Concrete T-Beams.

Reinforced concrete structures are exposed to various loads under critical environmental conditions, which might lead to the deterioration of the structures prior to their designed service life. Hence, to improve the serviceability of the reinforced concrete (RC) structures and meet the design requirements, the structures are strengthened using carbon fiber reinforced polymer (CFRP) composites. The application of CFRP is done using two major techniques, namely externally bonded (EB) reinforcement and near surface mounted (NSM) techniques. The purpose of this study was to examine and compare the behavior of RC T-beams that had been flexurally reinforced utilizing EB and NSM techniques. Six full-size RC T-beams were evaluated, including a reference beam and four beams that had been flexurally reinforced using laminates made of EB and NSM CFRP. The findings of the experimental tests reveal that, when using the same quantity of CFRP, the beams strengthened with NSM laminates outperformed those strengthened with EB laminates in terms of ultimate load.

Shear strengthening of reinforced concrete T-beams with anchored fiber-reinforced polymer composites

T-shaped beams are widely used in reinforced concrete (RC) structures, both buildings and bridges. Under-designed shear reinforcement and long-term aging make these structural elements susceptible to shear failure during earthquakes. The currenlty availalbe experimental work investigating the retrofit of these beams against shear failure is very limited. In this work, the external strengthening of RC T-beams with splay anchored strips of fiber reinforced polymer (FRP) composites under cyclic shear loading for the cases of normal and high strength concrete was studied. Six beams with 3.05 m length and 0.46 m that were conservatively reinforced against flexural failure were designed. The shear reinforcement of the beams was sufficiently high to ensure the dominance of shear failure. Three of the beams were built using a normal strength concrete and the other three were built using a high strength concrete with 28-day strengths of 30.5 MPa and 44.0 MPa, respectively. From each group of normal and high strength RC beams, one beam served as the reference. The other two beams were retrofitted with external strips of FRP composites that were bonded on the web and anchored under the flange of the beams. The beams were tested under cyclic four-point loading to evaluate the performance of the FRP retrofitting system against shear failure under simulated seismic loading. The deflection and the strain in the FRP composites were recorded while monitoring the strain of the longitudinal reinforcement to ensure an elastic response in flexure. The reference beams failed by shear cracking and the retrofitted beams failed by shear cracking and FRP delamination. The retrofitting technique increased the shear capacity of the beams by up to 37% and 20% for the normal and high strength beams, respectively, and promoted the beam ductility prior to failure.

Shear behavior of externally prestressed ultra-high-performance concrete (UHPC) T-beams without stirrups

Externally prestressed ultra-high-performance concrete (UHPC) beams without stirrups (EPUBs-WS) that simplify the reinforcement design and construction procedure are becoming a competitive option in bridge engineering. To investigate the shear behavior of EPUBs-WS, five specimens were designed and tested considering several critical parameters, such as the shear span-to-depth ratio (λ), shear stirrups, and longitudinal reinforcement ratio. The EPUBs-WS exhibits diagonal tension failure as the fibers pull out and the specimen shears off into two parts along the critical diagonal crack. However, the beam with λ = 3.67 exhibited flexural failure due to the large λ. The stiffness, shear-cracking strength, and shear strength of EPUBs-WS decrease as λ increases. Stirrups enhance the shear resistance of EPUBs but result in a more brittle shear failure mode. A higher reinforcement ratio augments the dowel action in EPUBs-WS, which contributes to a ductile shear failure mechanism. The web-shear cracking force accounts for 46% to 87% of the shear capacity, implying that the shear-cracking strength is a significant factor in the design of EPUBs-WS. An equation for predicting the shear-cracking strength of prestressed UHPC beams is proposed and validated using a database of experimental results reported in the literature. A parametric analysis is performed using 40 available specimens to investigate the effects of compressive strength, λ, reinforcement ratio, fiber reinforcing index, and prestressing level on the shear strength of prestressed UHPC beams without stirrups. By considering the key parameters, equations for estimating the shear strength are proposed and exhibit good accuracy.

Early hydration heat temperature field of precast concrete T-beam under steam curing：Experiment and simulation

Precast concrete T-beam steam curing can improve production efficiency, realize large-scale production of T-beams, and achieve better economic benefits. We performed tests and numerical simulations on a 30-meter-long full-size precast concrete T-beam to study the economical and reasonable steam curing scheme. The study found that in the early stages of steam curing, the temperature at the mid-span section increases faster than that at the end-span section. The highest temperatures of the tested beams were found in end-span section., and the core-surface temperature difference increased and then decreased, with the maximum temperature difference occurring at the junction of the top and web slabs of the concrete T-beam. To meet initial prestress tensioning requirements, the steam curing of increasing the temperature for 2 h to 50 ℃, keeping the temperature constant for 7 h, and cooling the temperature for 1 h is the most economical scheme, as seen from the comparison and analysis of the development law of concrete hydration heat temperature and the results of concrete test blocks under the same curing. Under this steaming scheme, the end-span section of the concrete T-beam reached a peak temperature of 68.5 °C at 14 h, and the core-surface temperature difference reached a maximum of 8.6 °C at 4.5 h; the peak temperature of the mid-span section was 60.2 °C, with a maximum temperature difference of 8.3 °C. In order to accurately predict the law of T-beam concrete temperature development under steam curing, two subprograms, HETVAL and UMATHT, were compiled on the ABAQUS secondary development platform. When calculating by natural age t, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 30.0% and 27.7%, respectively. After considering the equivalent age te of concrete, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 8.2% and 1.9%, respectively. Therefore, the UMATHT subprogram, considering equivalent age and hydration degree, can accurately predict the development of the concrete hydration heat temperature field under the steam curing process.

Experimental Study on Long-Term Performance of Concrete T-Beam

In recent years, long-span concrete bridges that have been built frequently expose the problems of excessive deflection and concrete cracking, which even lead to bridge collapse in serious cases. The reason is that, in addition to the insufficient estimation of creep and long-term deflection in current regulations, the rapid growth of traffic volume and the tight use of early-age concrete in construction schedules also have a great impact on long-term deflection. However, at present, the calculation methods of long-term performance are mostly based on the results of material performance tests. However, there are relatively few studies that take bridge components as research objects and consider the influence of load and age factors. The long-term performance of concrete beams is examined and the calculation methods of long-term performance are given by considering various loading levels and ages. Specimens are fabricated using a 1:4 scale model of a standard T-beam with a length of 20 m to conduct the experiment. Based on the long-term observation of the test beam, the variation laws of the mid-span deflection of the concrete T-beam and the concrete strain in the compression zone with time are obtained under the aforementioned conditions. Following a comparative analysis of experimental results with computational results based on existing studies and relevant national and international codes, this study proposes and discusses a set of formulas for the assessment of shrinkage and creep. The obtained creep coefficient test results fall between the values of the Chinese specification and those of AASHTO, where ASSTO is the lower limit and the Chinese specification is the upper limit. The long-term deflection is as follows: 40% of the one-year value at one month, 66% of the one-year value at three months, and 80% of the one-year value at six months. However, the long-term deflection coefficient of beams with an early loading age is larger than the current standard, and the deflection coefficient of T-beams with three-day loading age reaches 6.0. We compare and discuss the test results with the calculation results and related codes obtained in different studies conducted at home and abroad. Based on our present findings, we propose formulas for shrinkage and creep evaluations.

Analysis of Fire Resistance of Prestressed Concrete T-Beam Based on ABAQUS Numerical Simulation

The analytical fire resistance calculations were carried out on 57 prestressed concrete T-beam models using the finite element software ABAQUS. The effects of different fire modes, different concrete strengths, different flange plate thicknesses, different ratios of the prestressing bar, and different concrete protection layer thicknesses were investigated in three cases with load ratios of n = 0.4, n = 0.6, and n = 0.8. The fire resistance of prestressed concrete T-beams shows a large variability under different fire modes. The fire mode significantly affects the fire resistance of the structure and should be given more consideration in the subsequent fire resistance design of the structure. The configuration of prestressing bars will significantly increase the fire resistance of concrete T-beams, while the thickness of the concrete protective layer and the concrete strength will significantly affect the fire resistance of prestressed concrete T-beams. Therefore, the fire resistance can be improved by adding prestressing bars, increasing the concrete strength, and increasing the thickness of the protective layer in the design. Finally, a fitting equation for fire resistance of the prestressed concrete T-beams based on the finite element model calculation data was created. The equation has good prediction accuracy and can provide a reference for the fire resistance design of prestressed concrete T-beams.

Parametric study on reinforced concrete T-beam girder bridges

The development of any country is indicated by its infrastructure. Highways are a significant part of the infrastructure in India. Usually, most of the bridges on highways are T-beam girder bridges. This paper deals with the investigation of a T-beam girder bridge for dead load and Indian Road Congress (IRC) live loads. In this study, linear finite element analysis of a skew bridge with T-beam girders has been carried out using finite element software CSiBridge22 as per IRC provision. The skew angle, span, span-depth ratio, loading conditions, and girder spacing are all factors that influence the behaviour of a skew bridge. Two parameters i.e., span length and skew angle are used in the analysis, and the effect of these parameters on the bending moment, shear force, torsional moment, and deflection is studied. For validation, manually calculated results following the analytical method are compared with those obtained from a finite element model. A convergence study is performed to get the optimum mesh size. The findings of the study demonstrate that skew angle has a more significant effect on the bridge than other characteristics. The bending moment (BM) at the mid-span of the bridge and deflection decrease as the skew angle increases, whereas the shear force (SF) and torsional moment (TM) increase with the increase in skew angle.

Long-Term Prestress Loss Calculation Considering the Interaction of Concrete Shrinkage, Concrete Creep, and Stress Relaxation

In order to accurately calculate the long-term prestress losses of prestressed tendons, a time-varying model of long-term prestress loss considering the interaction between concrete shrinkage, creep, and the stress relaxation of prestressed tendons was constructed. Then, a method for calculating the long-term prestress losses of concrete structures was developed. A long-term prestress loss test of a prestressed concrete T-beam in a long-term field test environment was carried out. The measured values of long-term prestress losses are compared with the calculated results of JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model. The results show that the long-term effective tension of the T-beam decreases gradually with the increase in the load holding time. At the beginning of loading, the tensile force changes rapidly and then gradually slows down. The later the tensile age or the higher the initial loading stress level, the smaller the long-term prestress losses of the prestressed tendons. The long-term prestress loss values calculated by JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model increase with the increase in the load holding time. In the early stage of loading, the rate of change slows down and tends to be stable. The calculated results of JTG 3362-2018 and AASHTO LRFD-2007 are significantly different from the measured values. However, the calculated results of the time-varying law model are in good agreement with the measured values. The average coefficients of variation of the long-term prestress loss calculated by JTG 3362-2018, AASHTO LRFD-2007, and the time-varying law model are 17%, 10%, and 5%, respectively. The time-varying law model of the long-term prestress losses of prestressed tendons is accurate, and the long-term prestress loss of prestressed reinforcement can be predicted effectively.

Nonlinear FE Prediction of Shear Strength of RC T-Beams with Flange in Compression Zone

This research predicts the shear strength of reinforced concrete T-beams with flanges under compression stresses using nonlinear finite element (FE) analysis. A FE model is developed and verified against specially designed experiments (beams with varying flange width and depth). Results of the FE models were found to be in excellent agreement with their corresponding experimental results. The average load capacity and deflections (FE/experiments) ratios were 1.03 and 0.87, respectively. We then conducted an extensive parametric study to investigate the structural performance of flanged beams under the effect of two concentrated point loads. This parametric study examined four parameters: flange dimensions, longitudinal reinforcement in flange, concrete compressive strength, and shear span to depth ratio. Our findings indicated that the presence of compressed flanges in T-beams increases the shear strength by up to 260% of the shear strength of the web alone. The shear strength of flanged beams increases with the increase in flange dimensions, where the effect of flange thickness is more pronounced than that of flange width. Moreover, the presence of longitudinal reinforcement in the flange enhanced the beam's shear strength by up to 40%, compared to similar beams without flange reinforcement. Additionally, the shear strength increased up to three-fold for various beam conditions when the shear span to depth ratio was reduced from 2.0 to 0.5. These findings provide valuable insights for designing and constructing reinforced concrete T-beams with flanges under compression stresses.

Detect the stiffness transition in beam structures by using the passive tap-scan method

Damage detection of bridges through the response of a passing vehicle has drawn much attention in recent years. Most related researches focus on the impact of the bridge stiffness on vehicle responses. However, this paper demonstrates that the vehicle response is more sensitive to the stiffness transition in bridge girders. The theoretical basis is established on a vehicle-bridge interaction model, in which the change of an effective vehicle stiffness is introduced to represent the change of beam stiffness. The solution to this problem clearly shows that the acceleration of vehicle has an abrupt change at the stiffness transition point due to the discontinuity of the stiffness gradient. This effect will be enhanced when applying a tapping force near the vehicle resonance frequency. This tapping force can be economically generated by coordinating the vehicle velocity and the geometric pattern of toothed wheels, which was called the “passive tap-scan method” in a recent paper. This theory also reveals that the amplitude of the acceleration of vehicle is a quadratic function of the stiffness change ratio. Hence, a novel damage detection method is proposed to give a quantitative evaluation of the damage. These theoretical findings are quantitatively verified by numerical simulations and experimental tests on a standard pre-stressed concrete T-beam. Then, the practical capability of this damage detection method is further demonstrated through a field test on a real bridge.

Transient response and performance of prestressed concrete deep T-beams with large web openings under impact loading

Abstract This study reports testing results of the transient response of T-shape concrete deep beams with large openings due to impact loading. Seven concrete deep beams with openings including two ordinary reinforced, four partially prestressed, and one solid ordinary reinforced as a reference beam were fabricated and tested. The effects of prestressing strand position and the intensity of the impact force were investigated. Two values for the opening’s depth relative to the beam cross-section dimensions were inspected under the effect of an impacting mass repeatedly dropped from different heights. The study revealed that the beam’s transient deflection was increased by about 50% with greater amplitudes for response oscillations due to impact loading as the impact force increased twice. The results showed that the transient strains in the reinforcement and concrete increased when increasing the opening depth with higher amplitudes for the response oscillations, whereas it had a minimal effect on the beam’s transient deflection. The reinforcement and concrete strain results indicated a higher damping for the strains as the prestressing strands were introduced. Comparison with solid deep beam response showed remarkable increase in the beam deflection and strains with greater amplitudes for response oscillations when large openings were introduced in the web.

Fire Resistance of Reinforced Concrete T-Beams with Circular Web Openings

The flexural performances of a solid reinforced concrete (RC) T-beam and three RC T-beams with circular openings subjected to the ISO-834 standard fire were experimentally studied. The failure mode, fire resistance, time-deflection curve, and mid-span deflection recovery of the RC T-beams were analyzed by considering the factors such as the bottom chord depth and the stirrup status (refers to whether the stirrups were cut off when drilling). The results showed that the fire resistance of the RC T-beam with a 220 mm bottom chord was almost the same as that of the solid beam and both failed in ductile modes; however, the fire resistance of the RC T-beam with a 100 mm bottom chord was 18.9% lower than that of the solid beam and failed in a brittle mode. Whether the stirrups of the pure bending section were cut off when drilling had little effect on the fire resistance of the RC T-beam. Numerical simulations were also validated to study the mechanical properties influenced by the bottom chord depth. Finally, a simplified method of high precision was proposed to deduce flexural capacities of RC T-beams with circular openings under fire.

Experimental and Finite Element Study on the Shear Performance of Existing Super-Span Concrete T-Beams Retrofitted with Glass Fiber-Reinforced Plastic

Super-span, reinforced concrete, T-shaped cross-section beams (T-beams) with a service life of more than 30 years are widely used in highway bridges in China. Most of these beams have been retrofitted with glass fiber-reinforced plastic (GFRP) to prevent performance degradation. However, the actual shear performance, ultimate state, and failure mechanism of the existing retrofitted super-span concrete T-beams are currently unclear for many inextricable problems. To fill these gaps, in this study, one super-span concrete T-beam, in service for 31 years and retrofitted with GFRP, was extracted from a highway bridge to conduct shear experimentation in a structural laboratory. To assess the particularity of the specimen, finite element analysis was also conducted using ABAQUS software as a supplement to the shear tests. The failure procedure of the specimen was investigated, and the influence of the loading mode on the shear performance of a super-long and old T-beam was also studied. It is concluded that the failure of the super-span T-beam begins with small cracks at the bottom of the mid-span, rather than a loading point.

Flexural behaviour of geopolymer concrete T-Beams reinforced with GFRP bars

The flexural performance of geopolymer concrete (GPC) T-beams reinforced longitudinally with GFRP bars under a four-point static bending test was investigated. Six full-scale simply supported T-beams were cast and tested; one control specimen was made with ordinary Portland cement concrete (OPCC), while the other five beams were made of geopolymer concrete. The G-GPC2 was designed to attain the same theoretical moment capacity as the G-OPCC6 control beam. The main parameters investigated were the reinforcement ratio of ρf/ρb = 0.75, 1.05, 1.12, 1.34 and 1.34 for G-GPC1, G-GPC2, G-GPC3, G-GPC4, and G-GPC5, respectively, and compressive strength of geopolymer concrete. Based on the results of the experiments, the ultimate strain of GPC did not show the same behaviour as that of OPCC, which affects the mode of failure. The beam capacity and deflection were, respectively, overestimated and underestimated using the ACI 440 2R-17 predictive equations.