T-shaped Beam Research Articles

Innovative Fiber-Reinforced Polymer Rope-Based Closed-Form Retrofitting Methods Applied in Reinforced Concrete T-Shaped Beams under Torsion.

The fiber-reinforced polymer (FRP) strengthening of reinforced concrete (RC) elements with torsional deficiencies has not yet been extensively studied. Existing studies have primarily focused on rectangular RC beams. The few studies on L or T-shaped beams have used open-form retrofitting methods. However, premature debonding of the retrofitting from concrete surfaces often leads to detachment before achieving enhanced torsional capacity. This study introduces an innovative application of closed-form FRP retrofitting for RC T-beams against torsion. Two novel closed-form torsional upgrading methods were proposed and investigated through a comprehensive experimental program involving eight large-scale T-beams. One method employs FRP ropes embedded in transverse grooves near the surface, while the other combines U-shaped EB-FRP strips with FRP ropes. Additionally, two configurations were examined replicating scenarios where the upper part of the slab is accessible or inaccessible. The results demonstrate that the closed-form methods improve torsional strength by 9% to 25% and twist at failure by 92% to 536% compared to unstrengthened beams, with beams retrofitting through the slab exhibiting superior performance. Step-by-step technical guidelines of the proposed methods are presented to minimize construction defects and ensure effective implementation in real RC structures.

Experimental study on flexural behavior of corroded post-tensioned T- shaped beam

A comprehensive literature review on pre-stressed concrete beams subjected to corrosion reveals that most experimental studies are on rectangular sections even though T-shaped and box sections are more widely used in engineering practice with post-tensioned prestress, in particular for heavy structures like bridges. In this paper, five post-tensioned T-shaped beams were prepared, four of which were subjected to accelerated corrosion, and then all the beams were subjected to the four-point bending test. Special attention was directed to the cracking propagation and failure patterns, load-deflection, load-strain of concrete and steel strand, ductility and flexural capacity of the test beams. The experimental results show that the flexural behavior of the test beams deteriorates with the corrosion degree of prestressed strands, especially when the corrosion degree exceeds 2 %. When the corrosion degree is 8.42 %, the failure pattern of crushing of compressed concrete is changed to the rupture of the wires. The corrosion effects on the load-strain of steel strands depend on corrosion loss, strand position and loading stress state. Corrosion of steel strands reduces the compressive strain of concrete at the same compression position and the ultimate strain of the prestressed strands at the position of beam end. Finally, a numerical model is proposed, which can provide accurate and effective predictions of the failure pattern and flexural capacity of the corroded post-tensioned T-shaped beam.

Flexural capacity design model of reinforced concrete beams strengthened with hybrid bonded CFRP

In order to improve the calculation methodology for the flexural capacity of RC (Reinforced Concrete) beams strengthened with HB-CFRP (Hybrid Bonded-Carbon Fiber Reinforced Polymer), three-point bending tests were conducted in this study. The experimental setup involved 9 HB-CFRP strengthened T-shaped beams and 1 unstrengthened beam for comparison. The effects of anchor spacing, anchor pressure, CFRP thickness, and anchor distribution pattern on the flexural performance of strengthened beams were investigated. Additionally, the development of the full range load-deflection curves of the HB-CFRP strengthened specimens was analyzed. Two bond strength models (the Wu model and Liu model) were modified. Six parameters were considered in the modified model, namely, the CFRP elastic modulus, CFRP thickness, number of mechanical fasteners in the shear span, CFRP-concrete width ratio, concrete cylinder compressive strength and normal pressure applied to the mechanical fasteners. The accuracy of the modified models was compared on the basis of three specifications. Results indicated a notable enhancement in the flexural capacity of the strengthened beams, ranging from 61.1 % to 158.1 % compared to the unstrengthened beam. Taking the ACI specification as an example, the mean value and coefficient of variation (COV) of the flexural capacity obtained by directly using the Wu model were 1.187 and 0.169, respectively; the results obtained by using the modified Wu model based on the measured FRP strain were 1.038 and 0.125, respectively; and the results obtained by using the modified Wu model based on the ACI reversed-calculated strain were 1.012 and 0.106, respectively. After the strengthened beam reached the peak load, the load then decreased abruptly to the vicinity of the moment mid-span deflection curve of the reference beam. As the loading continued, the resistance improved by 27.4 %∼79.3 % due to the increase in interface friction in the mechanical fasteners and concrete.

Early detection of structural damage in UHPFRC structures through the combination of acoustic emission and ultrasonic stress wave monitoring

Ultra-High-Performance Fiber-Reinforced Cementitious Composite (UHPFRC) offers several advantages compared to concrete, notably due to the strain hardening behavior under tensile actions. Structures made of this composite material are lightweight and highly durable, thanks to the UHPFRC waterproofing quality. Nonetheless, the tensile behavior leads to a different cracking pattern than conventional concrete that is not fully understood yet. This paper presents an innovative monitoring approach that combines passive acoustic emission and active ultrasonic stress wave to localize and quantify damage on a full-scale UHPFRC beam during the loading protocol. This monitoring technique involves 24 transducers that are embedded throughout a UHPFRC t-shape beam of 4.2 meters. Continuous monitoring using this unique passive and active approach enables accurate location events, such as micro-cracking within the beam. Moreover, this sensor network is able to determine the location of the macro-crack that is linked to the structural collapse just after the end of the elastic domain. This novel sensor network opens new possibilities to monitor the structural behavior and detect damage on UHPFRC structures before they affect the structural behavior in terms of deflection and strain.

A novel T-shaped beam bistable piezoelectric energy harvester with a moving magnet

Vibration energy harvesting holds the promise of providing autonomous power for low-power electronic devices. To improve the issue of the limited bandwidth of the piezoelectric energy harvester, this work proposes a novel T-shaped beam bistable piezoelectric energy harvester with a moving magnet. The moving magnet can not only provide nonlinear force to adjust bandwidth, but also increase the number of system resonance peaks, which improves the utilization of the magnet, enhancing the adaptability of the vibration energy harvesting device to the environment. Established a mathematical model and validated it through experiments. Some parameters, such as external resistance, magnet spacing, and spring stiffness, are analyzed by theoretical analysis. The results indicate that, at an acceleration amplitude of 0.3 g and a frequency of 15.7 Hz, the peak output power of the main support beam is 2.36 mW. Similarly, at an acceleration amplitude of 0.3 g and a frequency of 15.6 Hz, the peak output power of the parasitic cantilever beam is 0.56 mW, demonstrating its potential to power low-power electronic components. The moving magnet provides an additional resonance peak for the harvester, offering a new method for the design of broadband magnetic nonlinear piezoelectric energy harvesters in the near future.

Experimental-numerical analyses on energy harvesting characteristics of non-conventional T-shaped beams with varied piezoelectric patch location and anchor position

Recently, researchers have studied innovative beam structures in a quest to maximize the energy conversion capability of piezoelectric (PZT) transducers coupled with the shims. A T-shaped beam is one of the structural elements used for harvester design owing to its exceptional geometrical advantage. While a number of research papers have reported its performance characteristics, its potential for harnessing the vibration energy at much lower resonance frequency and damping has not been explored. This paper presents non-conventional T-shaped beam harvesters, namely, the Uniform Tapered T-shaped Beam (UTB) and the Reversed Tapered T-shaped Beam (RTB), with the purpose of enhancing the T-shaped beam functionality. A performance analysis between the UTB, RTB and a conventional T-shaped beam (CTB) harvester of equal mass was conducted, where experimental results show that the RTB harvester has a lower fundamental resonance frequency of 12.3% and 28.3% when compared to the CTB and UTB, respectively. Also, a maximum terminal voltage of 82.8 V and an output peak power of 4.6 mW were produced by the RTB harvester when the PZT patch was placed near its clamped end. In addition, we investigated the effect of the anchor position of the beams on their energy harvesting performance using a finite element analysis (FEA) tool. The numerical results show that the position of the anchor has a considerable effect on the overall characteristics of the configurations.

Flexural Strengthening for Reinforced Concrete T-Shaped Beam by Tightened Strands Position Change

Flexural Strengthening for Reinforced Concrete T-Shaped Beam by Tightened Strands Position Change

Pullout Tests on Concrete Breakout Strength of Headed Reinforcement Bars Embedded in Roof Exterior Beam-Column Joints

Recently, the use of headed bars as mechanical anchorage in reinforced concrete beam-column joints has increased rapidly. This type of anchorage is used for T-shaped beam and exterior column joints at middle floors and for L- and T-shaped beam-column joints at the rooftops of buildings. However, few experimental data are available regarding the anchorage capacity of headed bars embedded in L-shaped beam-column joints. Nine pullout tests are conducted to investigate the anchorage capacity of headed bars embedded in L-shaped beam-column joints. Parameters affecting the anchorage capacity, such as the diameter, embedment length, location of the headed bars, and the number of supplementary bars are considered. The anchorage capacity of the headed bars is evaluated using empirical formulas proposed by Kubota and Murakami and a formula for concrete cone failure. The failure behavior of the specimens is concrete failure with cracks propagating in the diagonal direction at the maximum applied load. The anchorage capacity increases with the embedment length and diameter of the headed bars, number of supplementary bars, and concrete area. For most specimens, the Kubota and Murakami formulas overestimate the anchorage capacity, whereas formula for concrete cone failure yields lower anchorage capacities as compared with the test results.

Wet joint performance of 3D printed concrete beam segments under flexural loading

A segmented 3D-printed concrete (3DPC) beam is designed whose structural reliability depends on a rebar that can withstand tensile stress at the joints between segments under bending moments. In this study, a new approach is for the first time presented on rebar placement after concrete hardening. It details an innovative testing procedure of joint behavior and bonding strength through the use of 3DCP beam segments assembled to form T-shaped beams with an underside groove into which a rebar is inserted. The bonding strength of the rebar embedded in mortar within the semi-circular groove and the wet joints between segments are characterized and validated. Different variables are considered in the modularization of the 3DPC beam segments and bonding stresses between rebar and concrete are studied. To do so, the beam test procedure was adapted to 3DPC beam segments with 3 rebar diameters and 2 segment lengths subjected to 3-point and 4-point bending flexural tests. As a main finding, the results of this research indicated that both rebar and matrix, when properly designed, underwent bonding failure at loads above their theoretical ultimate limit design values, at the yield point of the rebar steel, demonstrating that placement of rebars after hardening of the 3DPC segments can therefore form a structurally reliable joint.

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.

Experimental Research on Fatigue Performance of Reinforced Concrete T-Shaped Beams under Corrosion-Fatigue Coupling Action.

Highway bridges in coastal areas are seriously affected by the marine environment, while most of the existing test methods for bridge-reinforced concrete beams considering both corrosion and fatigue factors are carried out in an alternating manner, which cannot reflect the actual service conditions of the bridge structure. This paper focuses on an experimental study of the coupled influence of reinforcement corrosion and fatigue loading in reinforced concrete T-shaped beams. A novel loading test device that can realize the corrosion-fatigue coupling effect is designed, and then six reinforced concrete T-shaped beams are fabricated and tested. For the corrosion-fatigue coupling test beams, the variation law of beam cracks, failure modes, steel strain development law, load-deflection relationship, and fatigue life are analyzed and compared with that of the simple fatigue test beams. The test results show that the cracks of the test beam develop continuously with the fatigue loading times under the corrosion-fatigue coupling environment. The fatigue failure modes are all brittle fractures of the main steel bars, which present the shape of uneven oblique section tearing. The new testing device and approach can provide direct insights into the interaction of reinforcement corrosion and cyclic loading on the fatigue behavior of T-shaped RC beams, which can be further used to understand the long-term performance of bridge structures under complex marine environments.

Calculation Method of the Residual Bearing Capacities of Concrete T-Shaped Beams Considering the Effect of Fire Cracks

Calculation Method of the Residual Bearing Capacities of Concrete T-Shaped Beams Considering the Effect of Fire Cracks

Investigations on Nonlinear Dynamic Modeling and Vibration Responses of T-Shaped Beam Structures

A novel nonlinear dynamic modeling approach is proposed for the T-shaped beam structures widely used in the field of aerospace. All of the geometrical nonlinearities including the terms in the deformation of the beams, the terms at the connections, and the free ends of beams are considered in the dynamic modeling process. The global mode method is employed to determine the natural frequencies and global mode shapes of the linearized system. The validity and accuracy of the derived model are verified by comparing the natural frequencies obtained with those calculated from FEM. Adopting the Galerkin truncation procedure, a set of reduced-order nonlinear ODEs is obtained for the structure. A study on the variation of dynamic responses taking the different numbers of global modes into account is performed to determine the number of modes taken in nonlinear vibration analysis. A comparison between the responses of the system with linear or nonlinear matching and boundary conditions is given to evaluate the importance of neglecting and reserving the nonlinear terms in matching and boundary conditions. It is shown that ignoring the nonlinear terms in both matching and boundary conditions may significantly alter the responses while developing the discretized governing ODEs of the structure.

Mechanical Performance Study of Beam-Column Connection with U-Shaped Steel Damper.

The article proposes the use of a semi-rigid energy-dissipation connection combined with a U-shaped metal damper to avoid brittle failure of rigid steel beam–column connections under seismic loading. The U-shaped metal damper connects the H-section column and the H-section beam to form a new energy-dissipation connection as an energy-dissipation member. Compared with the existing research, this connection has a stable energy-dissipation performance and great ductility. To clarify the mechanism of energy dissipation, mechanical models under two U-shaped damping deformation modes are established. The calculation formulas for the yield load and stiffness are derived for the corresponding deformation mode using the unit load method. Taking the T-shaped beam–column connection and the application of U-shaped steel damper in the beam–column connection as an example, the mechanical model of the connection is established and the calculation formulas for the yield load and stiffness are derived. At the same time, the connection is subjected to a quasi-static test under cyclic loading. The results show that the hysteretic curve of the test is complete and that the skeleton curve is accurate compared to the theory. The error range of the initial stiffness and yield load obtained by the test and the theoretical formula is kept within 20%, indicating that the theoretical formula is reasonable and feasible. In addition, the correctness of the finite element model is verified by establishing a finite element model and comparing it with the test. The mechanical responses of purely rigid connections and rigid semi-rigid composite connections are compared and analyzed using a multi-story and multi-span plane frame as an example. The results show that the model with semi-rigid connections, compared to the model with rigid connections, avoids the gradual loss of bearing capacity caused by the failure of the connection area of the second floor of the main structure and improves the seismic performance of the main structure.

Systematic calibration procedure for CFRP sheets and rods strengthened RC T-beams by using RBSM

In this study, a nonlinear 2D rigid body spring model (RBSM) was developed to verify the experimental works of Carbon Fiber Reinforced Polymer (CFRP) sheets and rods strengthened reinforced concrete (RC) T-shape beam (RC T-beam) section under a combination of bending and shearing loads. Modified Mohr–Coulomb criteria were adopted for modeling the plastic damage of concrete material. The orthotropic smeared layers representing the steel and CFRP materials were laminated on the concrete surface to model the reinforcing steel bars, stirrup steel, and CFRP sheets and rods. A mechanical behavior-based approach to fit the experimental results was discussed using the numerical results at each calibration stage. This study shows how the gradient of compressive and ultimate tensile strength of concrete affects the initial flexure behavior of the load-displacement curve of an RC T-beam. In contrast with finite element modeling, the RBSM can exhibit the crack propagation processes of element separation during the simulation. The calibrations showed the agreement of the models used in predicting the flexural behavior, ultimate load, and strengthening effects of the CFRP sheets and rods to the RC T-beam under bending loads. A systematic calibration procedure combined with the recommended use of energy-based criteria to evaluate the results of calibrated load-displacement curve was proposed.

Bending Behaviour of Prestressed T-Shaped Concrete Beams Reinforced with FRP-Experimental and Analytical Investigations.

Materials such as high performance (HPC) or ultra-high performance concrete (UHPC), and fibre-reinforced polymer (FRP) reinforcement can be used to improve the resource efficiency in concrete construction by, for example, enabling the production of thin-walled structures. When building filigree concrete beams two essential factors must be considered: the low stiffness of the structure and the bond between the materials. By prestressing the structural stiffness is improved while an adequate concrete cover ensures sufficient bond strength. Based on this the bending behaviour of prestressed T-shaped beams reinforced with FRP, focussing on determining the influence of four parameters on the bearing capacity, bond behaviour and failure mode, is investigated in this paper. Comprehensive experimental investigations prove the potential of the approach and show that a reduction of the web thickness down to 40 mm, a lower concrete quality, and the use of glass FRP instead of carbon FRP allow a more resource-efficient structure while the applied prestressing leads to a higher utilisation of the high performance materials.

Research on vibration energy collector of T-shaped piezoelectric beam

In this paper, in order to obtain a larger amplitude–frequency width, a T-shaped vibration energy harvester device with 1:2 internal resonance buckling was investigated and designed in a parametric study way, whose natural frequency can be adjusted by changing the geometric parameters and buckling load exerted on the T-shaped piezoelectric beam. The effects of different model lengths and widths on the output voltage of the energy harvester were studied systematically. By comparing the difference between the variation trend of displacement value and output voltage value of harvester model, it can be concluded that internal resonance can broaden the frequency band of vibration energy collection of buckling T-shaped piezoelectric beam. Additionally, when the internal resonance ratio is 1:2, the amplitude width and voltage output value can be effectively increased. The results show that when the buckling T-shaped piezoelectric beam resonates at a ratio of 1:2, the vibration energy collection frequency band of the buckling T-shaped piezoelectric beam can also be broadened.

Experimental study on the shear strength of reinforced concrete composite T-shaped beams with web reinforcement

The current increasing use of precast concrete elements and cast-in-place concrete slabs, namely concrete composite elements, in construction requires a better understanding of their behaviour in shear. In this work, 19 T-shaped composite and monolithic specimens failing in shear were experimentally tested. Their results were compared to study the influence on the shear strength of: the flange width, the presence of an interface between concretes and the strength of the concretes of both beam and slab. The shear transfer mechanisms were analysed by adapting to these specimens a mechanical model previously proposed by the authors for rectangular composite beams. It was concluded that: the composite specimens’ shear strength did not increase with widening flange width when the specimens showed an extended interface cracking, but increased when their crack pattern was similar to that of the monolithic specimens; the presence of an interface decreased the shear strength; the slab’s concrete compressive strength modified the composite specimens’ shear strength when the slab failed in shear, but not when the slab failed in bending or when the interface failed. The shear formulations of EC2, MC-10 Level III and ACI 318–19 gave good estimations when using the weighted average of the compressive strengths of the beam and slab concretes, similarly to those obtained with the proposed model. From the experimental results, the improvement of the interface shear strength of composite beams is proposed as a practical recommendation for increasing their shear strength. At the same time, the slab width and the slab’s concrete strength could be increased with the same purpose. This work experimental findings and the adaptation of the mechanical model to T-shaped beams lay the groundwork for a future development of a shear design and assessment formulation for concrete composite elements.

A Model for the T-shaped Beams with Straight Haunches for Uniformly Distributed Load

This paper shows a model for the T-shaped beams with straight haunches under uniformly distributed load that considers shear and bending deformations to obtain the fixed-end moments, carry-over and stiffness factors, which is the main part of this investigation. The methodology used is the conjugate beam method to obtain the rotations in supports and by the superposition method is solved this problems type. The current model considers only the bending deformations, and some authors consider bending and shear deformations for some proportions that are shown in tables. A comparison among the proposed approach that considers shear and bending deformations against the current model that considers bending deformations only are presented in the tables and graphics. A significant advantage of this paper over any other document is that is not limited to certain dimensions or proportions, and it can also be used for TT-shaped or TTT-shaped beams, which is commonly applied in highway bridges.

DESIGN OF THE DOBRA CHANTI SUSPENSION BRIDGE IN DISTRICT TEHRI GARHWAL, UTTARAKHAND, INDIA

Since the Tehri dam was constructed on the River Bhagirathi in 2006, considerable productive land areas, many villages, including old Tehri town in Tehri-Garhwal district has been submerged. It has also disconnected the travel and transportation routes along the east slopes of the reservoir, making the local residents lose access to the New Tehri town, which is equipped with resident-friendly facilities including health and education institutions and markets. Accordingly, the Uttarakhand Government has proposed to build the Dobra-Chanti H.M.V. Suspension Bridge to meet the local demand for an easy intra-regional accessibility, especially between the left and right sides of the River Bhagirathi. The project consists of a single-span suspension bridge, an approach bridge at each end of the suspension bridge, and slope protection work on each side. The suspension bridge has a 440m-long stiffening truss girder, 57m-tall steel towers, locked coil cable systems including suspenders, and anchor blocks. The approach bridges are reinforced concrete bridges with T-shaped beams. And river side slopes installed on both banks are protected and stabilized through CC blocks, shotcrete, and anchor bolts. All cek dimension has met the requirement