Haunched Beams Research Articles

Experimental study of a novel prestressed precast concrete beam-to-column joint based on plastic hinge relocation

To avoid the difficulties and high costs associated with traditional prestressed dry joints in construction, a novel post-tensioned precast concrete frame based on plastic hinge relocation (PPFBP) beam-to-column joint is proposed in this study. The precast columns and beams were integrated solely through the application of post-tensioned (PT) strands. The combined use of the haunched beams and the vertical slots for plastic hinge relocation simplifies the connection of the joint and enhances assembly efficiency. The mechanism of the proposed joint is analyzed first, followed by the development of a complete design procedure that complies with the criteria for plastic hinge relocation and self-centering. Three full-scale interior beam-to-column joints were designed and tested under cyclic loading to investigate the seismic performance in hysteresis curves, ductility, energy dissipation capacity, and residual displacement. The results indicate that the bearing capacity and ductility of the proposed joint are similar to those of cast-in-place structures, with the advantage of minimal residual displacement, enabling rapid post-earthquake repairability. The hysteresis curve of PPFBP joint with plastic hinge relocation exhibits a flag shape, indicating significant self-centering capability and energy dissipation ability. The cumulative energy dissipation of PPFBP joint with plastic hinge relocation is much higher compared to that without it, achieving a maximum equivalent viscous damping coefficient of about 15 %, which is similar to that of hybrid dry joints. The insufficient strength of the prestressed grouting material led to bond slippage in the specimen with bonded PT strands, exhibiting a hysteresis response similar to that with partially bonded PT strands. Finally, the prediction of the bearing capacity in PPFBP joint is consistent with the experimental results, validating the effectiveness of the proposed design method.

Shear performance and strength of reinforced concrete non-prismatic beams with basalt fiber reinforced polymer rebars

Tapered beams, which are horizontal structural elements, possess varying moments of inertia across their length. Among these, the pier cap mode is widely employed in engineering applications. This research explores the influence of incorporating basalt fiber reinforced polymer (BFRP) bars on the shear strength of eight concrete haunched beams. While two of these beams were straight beams, the others have different inclination angles. The study aimed to examine two main factors: the angles of tapered part in the compression chord and the effect of BFRP stirrups. Results from the experiment revealed a direct correlation between increasing tapered angles and the enhancement of shear capacity in haunched beams. Consequently, a comprehensive analysis was conducted using three different codes, leading to the formulation of proposed equations derived from semi-empirical methods. The analysis demonstrated a high level of accuracy in predicting shear strength with a satisfactory safety margin.

Ability of pre-cast strain-hardening cementitious composite plates to enhance the shear performance of RC haunched beams

The purpose of this paper is to test ten identical reinforced concrete haunched beams (RCHBs) to determine the effectiveness of pre-cast strain-hardening cementitious composite (PSHCC) plates for shear strengthening. For this purpose, the PSHCC plates have been manufactured in accordance with the test parameters, let to cure for roughly 30 days, and then dipped into the strengthened RCHBs' concrete cover at the critical shear span. The used PSHCC plates are rectangular in shape with a 20 mm thickness and a 100 mm width, and they are reinforced with a single layer of steel wire mesh. The considered key parameters were the effect of shear reinforcement in the test region, the PSHCC plate orientation angle (450, 600, or 900), and the spacing between PSHCC plates (200, 250, or 300 mm). In addition, it was interesting to observe how the strengthening plates, if they exist, are positioned in relation to the inner stirrups (aligned, un-aligned, or inclined). The application of PSHCC substantially enhanced the ultimate shear capacity of the strengthened beams, according to the results of experimental tests. Moreover, the inclined configuration of the PSHCC demonstrated higher shear performance than the vertical configuration, both in terms of the shear cracks characteristics and ultimate capacity. As well, the ductility and serviceability characteristics of the strengthened RCHBs were obviously affected by the application of PSHCC plates. Finally, a proposed analytical model was developed to estimate the shear capacity of the strengthened RCHBs using PSHCC plates.

Effect of size factor and tapered angles on the shear behavior and strength of haunched beams reinforced with basalt fiber reinforced polymer rebars: Experimental and analytical study

Haunched beams are beams that exhibit varying effective depth over their span. This study includes an experimental and analytical analysis aimed at investigating the influence of size factor on the shear behavior of tapered beams reinforced with basalt fiber reinforced polymer BFRP bars. The main focus of this study revolves around investigating the effects of both inclination angle and size factor as key variables. In this study, a total of eight simply supported beams were tested. The beams were longitudinally reinforced with a 1% ratio of BFRP reinforcement, and separated into two equal groups. Each group consisted of one straight beam and three haunched beams. The haunched beams had varied tapering angles, namely 4⁰, 7.96⁰, and 11.86⁰. The first group is designated for the allocation of large beams, while the second group is designated for the allocation of small beams, which have a cross-section that is one-fourth the size of the large beams. The test results indicate that an increase in tapered angles leads to an increase in shear strength. Additionally, it was observed that smaller beams exhibited a greater normalized shear strength compared to larger beams with a significant rate as compared with straight beams. Subsequently, two equations were developed using the tested data, whereby one of them represents an optimal equation including a logical safety margin, while the other equation is characterized by a conservative equation, providing a substantial safety margin for predictions.

Shear strength and behavior of recycled strap fiber reinforced concrete haunched beams

Haunched beams also known as tapered beams, are structural elements characterized by varying depths along their span. In light of the growing concern over plastic accumulation on a global scale which provides a threat to the environment, and the challenges associated with employing traditional stirrups in the construction of tapered elements, this research paper has emerged.The approach of this study is divided into two main parts: an experimental phase and an analytical phase. In the initial stage, eight beams were subjected to testing to investigate the influence of tapered angles and the presence of recycled strap fiber on the shear behavior of tapered beams. The outcomes of this experimentation revealed a significant trend: as the tapered angles and fiber contents increased, the shear strength of haunched beams also increased.The subsequent phase of the study focused on an analytical examination, incorporating models proposed in various literature sources. A comprehensive database of 91 beams was assembled to facilitate the selection of the most suitable shear model for modification. Building upon the analysis of this extensive dataset, an equation was proposed. Additionally, a smaller dataset featuring tapered beams with fiber was collected to apply further analysis and demonstrate the models' performance. The predicted results by the proposed model showed good agreement with experimental test results.

Reliability‑based probabilistic numerical plastically limited analysis of reinforced concrete haunched beams

This research proposes a novel method that considers the optimal reliability-based design of reinforced concrete haunched beams subjected to probabilistic concrete properties and complementary strain energy values. The theory is applied twice, once to evaluate a deterministic solution, where the plastic behaviour is constrained by the complementary strain energy of residual stresses induced within steel bars. Secondly, the same method is considered for a probabilistic solution where the concrete characteristics—compressive strength and modulus of elasticity—and complementary strain energy value vary randomly. The reliability index acts as a bound for the solution. It is important to mention that the model utilised in this publication is derived from recent research after being calibrated using Abaqus. This work represents an extension of that recent research that exclusively considered deterministic work. This research led deterministically to new estimates for the complementary strain energy, which will be interpreted as reflecting the behaviour of plastic thresholds and quantifying the associated loads. Afterwards, uncertainty is studied when probability interferes, showing various load values and damage in concrete and steel when the complementary strain energy and concrete properties are probabilistically evaluated, giving a less reliable solution as the load reduces. These effects are reflected in the varying plastic behaviour of the investigated haunched beams.

Limited Optimal Plastic Behavior of RC Beams Strengthened by Carbon Fiber Polymers Using Reliability-Based Design.

The plastic behavior of strengthened haunched beams utilizing carbon fiber-reinforced polymers (CFRP) was investigated using a probabilistic design that took into account random concrete properties, CFRP properties, and complementary strain energy values, with the reliability index serving as a limiting index, as the proposed method considers a novel method that deals with probabilistic parameters for models with limited plastic behavior designed based on the reliability index. The data used in this research were gathered and evaluated in a recent study on simply supported haunched beams reinforced with carbon fiber-reinforced polymers. The purpose of this research was to use the reliability limitation index for simulated strengthened haunched beams by taking into account randomness in concrete and CFRP properties and the complementary strain energy value, which is considered a plastic behavior controller that provides an illustration of the damage amount within the reinforcement steel bars. The results indicate how randomness affects the behavior of the presented models, which are chosen to have different numbers of CFRP strips. The variable randomness affects load and deflection values where the reliability index value increases as the corresponding load value decrease, reflecting the increased probability of failure in models subjected to higher loading conditions, while tension concrete damage percentages are reflected in the damage pattern presented in the results, showing that as the produced load increases, so does the damage intensity. It is also obvious that the reliability index served as a limitation index while taking concrete characteristics and complementary strain energy as random variables.

A Study of the Structural Behavior of Recycled-Concrete Haunched Beams with Web Opening

The structural behavior of Reinforced Concrete Haunched Beams (RCHBs) was investigated in this study. One prismatic control beam and fourteen Haunched Beams (HBs) were used in the experimental test and numerical analysis. The variables considered are Recycled Concrete Aggregate (RCA) ratio which is taken as 0, 30 %, and 60 %, opening shape (square and circular with the same area of 4560 mm2), and haunch angle (α) of 6.34° and 9.46°. The samples of dimensions (1750x200x300) mm were tested under a two-point load. The samples were simulated numerically using the Abaqus/CAE tool. The experimental outcomes show that using 30% RCA decreased the resistance by 8.24% - 26.45% compared with the control sample. While at 60% RCA, the resistance decreased by 16.35% - 34.71%. HBs with α=6.34° give a strength quite close to the control beam (PN) by 1.93%, while α=9.46° decreases the strength by 12.94% compared with PN. Compared with the solid beam, square holes in HBs provide a strength reduction range of 5.83% - 18.79% for α=6.34° and α=9.46°, respectively. The beams with circular apertures have a resistance decrease of about 3.43% - 14.70%, which corresponds to α=6.34° and α=9.46°. The numerical findings were 8.41% of the experimental data.

Experimental and numerical study on innovated steel Shear Resisting Frame with Haunched Beams (SRFHBs)

Steel shear panels are one of the most significant lateral resisting systems with high ductility and energy dissipation capacity. This paper describes and discusses innovated steel Shear Resisting Frame with Haunched Beams (SRFHBs) with a particular focus on very short link beams. Regarding shear panels performance, the conception of SRFHB emerged with the aim of improving the link beam behavior in Eccentric Bracing Frames (EBFs) as well as architectural constraints and overcoming the span-to-depth ratio limitation provided by the seismic provisions in Moment Resisting Frames (MRFs) which notified especially in tall buildings with framed-tube structural system. SRFHB is comprised of two strong side columns connected to the link beam as the shear fuse in the middle of the span through haunched beams. Application of the haunched configuration makes it comfortable to reach very short links. Shear fuse plays the governing behavior as sacrificing element to keep adjacent members safe. Shear yielding and out-of-plane deformations due to the tension-field action, control the amount of energy dissipation. An experimental program and extensive nonlinear dynamic analyses were conducted to validate the test results and evaluate the seismic behavior of the proposed system and idea in comparison of the conventional EBF. Results indicated that SRFHBs could develop considerable performance with more desirable seismic response than traditional EBFs.

Limit design of reinforced concrete haunched beams by the control of the residual plastic deformation

In this paper, a novel computational (optimization) model is presented to control the plastic behaviour of reinforced concrete haunched beams using complementary strain energy of residual forces formed inside the steel reinforcing bars. For this purpose, a numerical model validation process was held and then two non-linear optimization problems were outlined. In these optimization problems, different objective functions were considered applying the optimal elasto-plastic analysis and design of haunched reinforced concrete beams aiming to find the maximal loading or the minimum volume of the steel used to reinforce the beams as the plastic deformations are controlled by using constraints on the complementary strain energy of the residual internal forces of the steel bars. Moreover, the effect of these constraints on different haunch angle beams is studied. The applied method is described in terms of nonlinear mathematical programming and providing solutions when the plastic reserves of the body are not fully exhausted. It is worth mentioning that in this study a concrete damage plasticity constitutive model is applied in the numerical problems and calibrated in accordance with the data gained from laboratory tests. The optimal solutions of the nonlinear mathematical problems were calculated by MATLAB programming codes written by the authors taking into consideration different objective functions and equality and inequality constraints for each case. Finally, by performing a parametric study, the different optimization problems showed how beams behaved differently under different complementary strain energy limit values shifting from elastic into elasto-plastic state and then reaches the fully plastic state where results showed different comparisons taking into consideration the effect of the different complementary strain energy limit values on the maximum applied load, geometry of the beam and steel volume used to reinforce the beams. Thus, complementary strain energy limit value is used to control the plastic deformation inside steel bars during loading progress where avoiding the formation of the plastic deformation in the steel bars would reflect on the general behaviour of the haunched reinforced concrete beams.

Comprehensive Shear and Flexural Study: Experimental and FE Modeling of RC Haunched Beams Rehabilitated by Basalt Fabric

Comprehensive Shear and Flexural Study: Experimental and FE Modeling of RC Haunched Beams Rehabilitated by Basalt Fabric

Numerical simulation and mechanical model of steel beam-to-column joints retrofitted by haunches

Within the retrofitting of steel structures, welding haunches to retrofit weak panel zones in beam-to-column joints are deemed to provide reliable cyclic behavior based on previous tests. Also, the force transferring mechanism in haunched beam sections is substantially changed under the influences of the haunch and panel zone. For the investigation of the behavior of the haunched beam section and the haunch, finite element models (FEMs) were established with considerations of material and geometry nonlinearities and then verified against previous tests. The force distributions were obtained and also predicted by mechanical models. Results showed that the moment resistance and initial rotational stiffness increased by 34.3%–76.9% and 51.6%–83.3% through retrofitting. Moreover, a noticeable difference in force distributions was observed in the haunched beam section. The direction of the shear force within the shear plate was reversed and its value could be even greater than the beam load. After the yielding of panel zones, the force redistribution appeared and subsequently led to increased forces in the shear plate and haunch flange. Furthermore, the comparisons among mechanical models indicated that the AISC model might underestimate the contributions of both the haunch flange and the shear plate in the elastic stage, and the plane-section-assumption model showed better agreements. However, without considering the force redistribution in the post-yielding stage, the above two models underestimated forces by 8.8%–32.0% and 9.7%–64.2%, respectively, and the simplified model was proposed with better predictions concerning the impact of the force redistribution to provide a greater safety margin in design.

Strengthen strategies for reinforced concrete haunched beams using fibre reinforced polymer fabric and engineered cementitious composites

External strengthening of reinforced concrete haunched beams with and without shear reinforcement has been investigated by using carbon and basalt fiber reinforced polymer fabrics. In addition, the flexural behavior of reinforced haunched beams which are partially and entirely produced from engineered cementitious composite has been tested. The samples, which were produced from self-compacting concrete, engineered cementitious composite, and a combination of them, were prepared and tested via four-point loading tests. Reinforced haunched beams were divided into two strengthening groups. Group 1 included the shear strengthening of self-compacting concrete reinforced haunched beams (beams without stirrups) by the consideration of various strengthening configurations with both fiber-reinforced polymer fabric types. Group 2 included the flexural strengthening of reinforced haunched beams via fiber-reinforced polymer fabrics and/or engineered cementitious composite. The obtained results were depended on the ultimate load capacities, load-displacement curves, crack patterns, and failure modes of strengthened reinforced concrete haunched beams. Experimental results show that the strengthening material and strengthening configuration influence the mechanical behavior of reinforced concrete haunched beams considerably. However, the effect of strengthening configuration was higher. The highest increase in load capacity was 72.8% for shear strengthening (group 1), while the highest increase was 28.8% for the flexural strengthening group (group 2). Furthermore, the U-shaped anchorage with fiber-reinforced polymer fabrics prevented the premature failure of engineered cementitious composite layer and fiber-reinforced polymer fabrics covering the bottom face of reinforced haunched beams and increased the load capacity of reinforced haunched beams, while some losses were observed in ductility. The replacement of the concrete with engineered cementitious composite on the tension side increased the load capacity of reinforced concrete haunched beams.

Strengthen strategies for reinforced concrete haunched beams using fibre reinforced polymer fabric and engineered cementitious composites

External strengthening of reinforced concrete haunched beams with and without shear reinforcement has been investigated by using carbon and basalt fiber reinforced polymer fabrics. In addition, the flexural behavior of reinforced haunched beams which are partially and entirely produced from engineered cementitious composite has been tested. The samples, which were produced from self-compacting concrete, engineered cementitious composite, and a combination of them, were prepared and tested via four-point loading tests. Reinforced haunched beams were divided into two strengthening groups. Group 1 included the shear strengthening of self-compacting concrete reinforced haunched beams (beams without stirrups) by the consideration of various strengthening configurations with both fiber-reinforced polymer fabric types. Group 2 included the flexural strengthening of reinforced haunched beams via fiber-reinforced polymer fabrics and/or engineered cementitious composite. The obtained results were depended on the ultimate load capacities, load-displacement curves, crack patterns, and failure modes of strengthened reinforced concrete haunched beams. Experimental results show that the strengthening material and strengthening configuration influence the mechanical behavior of reinforced concrete haunched beams considerably. However, the effect of strengthening configuration was higher. The highest increase in load capacity was 72.8% for shear strengthening (group 1), while the highest increase was 28.8% for the flexural strengthening group (group 2). Furthermore, the U-shaped anchorage with fiber-reinforced polymer fabrics prevented the premature failure of engineered cementitious composite layer and fiber-reinforced polymer fabrics covering the bottom face of reinforced haunched beams and increased the load capacity of reinforced haunched beams, while some losses were observed in ductility. The replacement of the concrete with engineered cementitious composite on the tension side increased the load capacity of reinforced concrete haunched beams.

Nonlinear Finite Element Analysis of Reinforced and Plain Concrete Haunched Beams Under Torsion

Abstract The present paper is focused on analysis of reinforced and plain concrete haunched beam under torsion based on non-linear finite element analysis NLFEA approach. Ten cantilever beams (five of them are steel reinforced and the rest are not reinforced) were modelled by using ANSYS software with different haunched angles to achieve the purpose of the present study. The verification was done for two prismatic beams under torsion, and two reinforced concrete haunched beams (RCHBs) under static shear load to ensure the correctness of modelling. The verification work illustrated a good agreement between the NLFEA results by using ANSYS and previous experimental work results. No specific details in torsional design for RCHB in many codes, and no/very less works have done regarding analysis or design of RCHB under torsion. The main purpose of the present work is checking the capability of using ACI-318 code in analysis and design of concrete haunched beam for torsion. The presented paper confirms the validation of using ACI-318-2019 in analysis and design of RCHB and plain concrete haunched beam PCHB as well, where the FEA results by using ANSYS were at accuracy not less than 92 % with the ACI-318-2019 results for all specimens. The torsional mechanism failure and shear stresses distribution of RCHB are discussed in the present paper.

Strengthening of reinforced concrete prismatic and haunched beams using light jacketing

An experimental study is presented where eight reinforced concrete beams (two prismatic and six haunched) previously designed and tested to fail in shear with substantial damage were repaired. The strengthening technique used was external beam jacketing, consisting of a light-gauge steel wired mesh covered with a 2 cm thick grout. Beams were tested under monotonic loading. The obtained load-displacement curves for the repaired jacketed beams are compared with those obtained for the original beams. It was found that the external jacketing technique was effective, as higher deformation and load capacities were achieved by the repaired beams in comparison to the original beams.

Equations for Shear Design of Continuous Reinforced-Concrete Haunched Beams Based on Stress Fields and Truss Models

Simple methods are required to reasonably estimate the shear strength of reinforced-concrete haunched beams (RCHBs) for design in order to inhibit shear failures in favor of a flexural behavior. In this paper, design equations developed from stress fields and truss models, also known as strut-and-tie models, are assessed and related with the processed experimental data for the cyclic testing of continuous RCHBs failing in shear. It was found that, for design purposes, plausible estimates for the shear strength of RCHBs could be assessed with the proposed equations.

Experimental and numerical evaluation of innovated T-resisting frames with haunched horizontal plate girders

In this article, a novel configuration for innovated T-resisting frames is proposed. New configuration uses haunched beams with three configurations as horizontal plate girders with prismatic link beam. Using haunched beams confirms T-resisting frame main concept with shear yielding which results in better seismic performance. Haunch configuration leads to achieve any link length ratio especially for very short links. To evaluate seismic response of the haunched beam, a half scale T-resisting frame specimen with haunched configuration at side column face is subjected to a proper cyclic loading protocol. In addition, the same frame is modeled in ABAQUS software to validate the modeling techniques. Results of verification showed good conformity between numerical analysis and test result. Finally, several numerical examples are studied to investigate the effect of height and span length on T-resisting frames with different haunch locations and various link lengths in seismic response. It was found that shear yielding of haunched beams results in high ductility and more energy dissipation and a proper behavior in comparison with prismatic ones.

Shear Failure Mechanism of Reinforced Concrete Haunched Beam by using Steel Fibre and Carbon Fibre

Shear Failure Mechanism of Reinforced Concrete Haunched Beam by using Steel Fibre and Carbon Fibre

Experimental investigation of rehabilitated RC haunched beams via CFRP with 3D-FE modeling analysis

This paper investigates the behavior of damaged Reinforced Concrete Haunched Beams (RCHBs) rehabilitated by Carbon Fiber Reinforced Polymer (CFRP) strips. The study consists of two parts. In the first part, a comprehensive experimental study was carried out on ten RCHBs and two control beams (prismatic) which were designed to fail in shear. The second part concerns with the finite element (FE) modeling of rehabilitated RCHBs. A novel finite element based approach is proposed to form a limit zone that exhibits all possible load capacities of rehabilitated RCHBs. Lower and upper intervals of this zone are determined by the maximum and minimum limits of load capacities of rehabilitated RCHBs. FE modeling of undamaged and strengthened haunched beams by CFRP represents the maximum limit, while FE modeling of the damaged beams rehabilitated by CFRP only without crack repair by epoxy represents the minimum limit. Experimental results show that shear load capacity of RCHBs rehabilitated with CFRP strips increases as compared to the capacity of them before rehabilitation. The amount of increase varies with respect to the type of RCHBs and the rehabilitation strategy. The nonlinear FE models show a good agreement with test results (R2 = 0.8349) where load-deflection curves of all experimentally rehabilitated RCHBs lie between maximum and minimum limits of FE analysis. Furthermore, there is a very good correlation between load capacity of rehabilitated RCHBs and the capacity of undamaged and strengthened RCHBs which is obtained from maximum limit of FE analysis results (R2 = 0.859).