U-shaped Steel Research Articles

Mechanical properties of a novel fiber-bridging interface for connecting FRP profile and concrete

The connection between FRP profile and concrete is critical for structural performance. This study introduces a novel fiber-bridging interface to enhance the FRP-concrete interfacial behavior. The interface comprises an epoxy resin adhesive layer, a carbon fabric layer, a mixture of adhesive and sand layer, and U-shaped steel fibers. Central pull-out tests were conducted to investigate the mechanical performance of this novel interface. The investigated variables included bond length and fiber volume fraction. Test results indicate that all specimens failed in a brittle mode at the adhesive layer, with load plateauing after reaching the peak. The number of steel fibers had limited influence on the interfacial behavior. Based on the load-slip curves, a bond stress-slip model for the tangential behavior was developed. An interfacial expansion model was further developed by means of FE analysis and machine learning. The three most widely used machine learning models, i.e., the BP neural network model, the random forest model, and the XGBoost model were selected. Comparisons show that all three models provide reasonable predictions, with the XGBoost model demonstrating the best performance. These models for the tangential and normal behavior of FRP-concrete interface were implemented into FE models for numerical analysis. Comparisons between numerical and experimental results show that the proposed models accurately describe the interfacial behavior of the fiber-bridging interface under brittle failure mode. The innovative interface proposed in this paper can be used for connecting concrete and FRP in various scenarios, and the proposed methodology of calibrating local bond behavior parameters from global response offers a new approach for establishing interfacial bond models.

Research on the Support Technology for Deep Large-Section Refuge Chambers in Broken Surrounding Rock in a Roadway

The phenomenon of peripheral rock instability is more common in crushed bedrock roadways, and the fundamental reason for this lies in the significantly different characteristics of its peripheral rock stress field. Taking the newly dug belt inclined shaft of PingDingShan TianAn Coal Co., Ltd. No. 6 Mine as the engineering background, a mechanical model of a broken perimeter rock roadway was established by using classical rock mechanics theory. Stress distribution around the roadway of the broken perimeter rock medium was systematically analyzed, and radial and tangential stress formulas of the broken perimeter rock were deduced. Through the formula calculation, it was deduced that there was a stress drop in the intact surrounding rock outside the disturbed zone, and the radial stress of the intact surrounding rock in its deep part was relatively increased, while the tangential stress was relatively decreased. The existence of crushed surrounding rock increased the minimum principal stress and decreased the maximum principal stress of the unfractured surrounding rock, which proves that a well-maintained disturbed zone can play a lining role. Thus, a “U-shaped steel + inverted arch + bottom arch linkage beam + floor bolt compensation” support program was proposed. This joint support program easily forms a closed support structure, which is more effective in controlling the deformation of tunnel perimeter rock. The support structure can effectively resist the deformation of the surrounding rock and enhance bottom drum resistance. Through numerical simulation, it was concluded that the horizontal displacement of the two gangs was reduced by 70%, and the displacement of the top and bottom plates was reduced by 77% after optimization of the support, which effectively controlled the stability of the broken surrounding rock.

Experimental study on the seismic performance of prestressed wood joints with buckling-restrained rods

Adding energy dissipaters to prestressed wood joints with reinforced beam-column interfaces is the main way to improve their seismic performance. In this paper, three quasistatic tests for beam-column edge joints with buckling-restrained rods (BRRs) were performed, and the effects of different reinforcements for beam-column interfaces and BRR connection methods on the stiffness, bearing capacity, energy dissipation, and self-centering performance of the joints were analysed. First, for BRRs connected with steel supports, the core member exhibited significant multi-wave deformation; for BRRs connected with steel pins, the slippage of the steel pins can easily lead to bending failure of the BRR end. Second, after adding BRRs, the bearing capacity of the joints increased by 24.8% on average, the final degradation rate of the secant stiffness decreased by 13.8% on average, and the equivalent viscous damping ratio at 0.03 rad drift increased by 17.3% on average. Third, compared with the joint reinforced by the combination of the U-shaped steel plate and screws, the skeleton curve of the joint reinforced by the combination of the flat steel plate and screws had little difference, but the final prestressing loss and residual drift were reduced by 14% and 74%, respectively. It was recommended to use the simpler reinforcement combining the flat steel plate and screws to improve construction efficiency. Finally, compared with steel pins, BRRs connected with steel supports were more conducive to improving the seismic performance of joints at large drifts. Among them, the equivalent viscous damping ratio increased by 29.3% on average. This study can give designers flexibility when selecting the interface reinforcements and BRR connection methods. These research results highlight the good seismic performance of prestressed wood joints with BRRs, which is conducive to further promoting the application of prestressed wood structures.

Gradient failure mechanism and control technology of deep roadways under the action of deviatoric stress field

Deformation control of deep roadways is a major challenge for mine safety production. Taking a deep roadway with a burial depth of 965 m in a mine in North China as the engineering background, on-site investigation found that significant creep deformation occurred in the surrounding rock of the roadway. The original supporting U-shaped steel support failed due to insufficient supporting strength. The rock mass near the roadway experienced a transition from triaxial stress conditions to biaxial and even uniaxial stress states as a result of excavation and unloading, leading to a gradient stress distribution in the surrounding rock. From the perspective of the roadway's deviatoric stress field distribution, we investigated the gradient failure mechanism of the roadway and validated it through theoretical analysis and numerical simulations. The study found that the ratio of horizontal principal stress and vertical principal stress determines the distribution shape of the surrounding rock deviatoric stress field. The gradient distribution of the stress field in the roadway will cause time-related deformation of the roadway, which will lead to large deformation and failure of the roadway. Based on this, the control mechanism of roadway gradient failure was studied, and then a combined support technology of CFST supports with high bearing capacity was proposed.

Step by step and combined supporting technique with allowable deformation + limiting shape for soft rock roadway

Aiming at the difficult problems of the large deformation in weakly cemented soft rock roadways, the reasons of large deformation are analyzed for roadways in Hongqingliang coal mine. On this basis, the principle of step by step combined support technology based on allowable deformation + limiting shape for weakly cemented soft rock roadway is proposed, and the optimal support parameters of step by step combined technology are determined by FLAC3D. Step by step combined support technology includes the primary support of anchor bolt + anchor cable + initial shotcrete and the secondary support of U-shaped steel shed + filling flexible material behind shed + control of key parts. The comparative analysis on the site shows that the deformation rate and final deformation amount of the surrounding rock after the step by step combined support are less than those of the primary support, and the deformation of the surrounding rock can be controlled effectively after the secondary support is added. Step by step combined support is superior to the traditional bolt + anchor cable combined repair in terms of economy and efficiency. The optimal construction period of each working procedure of the step by step combined technology is 28 days after the completion of the first support, and the step by step combined support based on allowable deformation + limiting shape is an effective way to control the surrounding rock of soft rock roadway.

Bending Properties of Cold-Formed Thin-Walled Steel/Fast-Growing Timber Composite I-Beams

A cold-formed, thin-walled steel/fast-growing timber composite system has recently been presented for low-rise buildings. It aims to increase the use of fast-growing wood as a green building material in structures, thus contributing to the transformation of traditional buildings. This study proposed a composite I-beam combined with fast-growing radiata pine and cold-formed thin-walled U-shaped steel. A four-point bending test was used to measure the bending properties of steel–timber composite I-beams under various connection methods. Based on experimental results, this study examined the specimen’s failure mechanism, mechanical properties, and strain development. In addition, a method for calculating flexural bearing capacity based on the superposition principle and transformed section method was suggested. It is evident from the results that fast-growing timber and cold-formed thin-walled steel can have significant composite effects. Different connecting methods significantly impact beams’ failure mode, stiffness, and bearing capacity. Furthermore, the theoretical method for calculating the flexural bearing capacity of composite beams differs from the test value by less than 10%. This paper’s research encourages the applications of fast-growing wood as light residential components, and it serves as a reference for the development, production, and engineering of steel–timber composite structural systems.

New reinforcements combining a steel plate and screws to enhance beam-column contact surfaces for prestressed timber joints

ABSTRACT The beam-column contact surface of joints in prestressed timber frames is one of the key factors determining structural performance. In this paper, a new reinforcement combining a steel plate and screws was proposed, and the effect of the reinforcements on the performance of joints was investigated by quasistatic tests for 5 beam-column edge joints. First, compared with the conventional joint, the joints reinforced by the steel plate and screws had an average increase in capacity of 25.8% and an average reduction in the degradation rate of the secant stiffness of 14.5%, which were beneficial for resisting repetitive loading. Then, the rate of the final prestressing loss and residual drift of the joint reinforced by the flat steel plate and screws were reduced by 20.5% and 85.7%, respectively, compared with those of the conventional joint. The enhancement effect of the reinforcement combining a U-shaped steel plate and screws was difficult to realize due to the susceptibility to the initial clearance. Finally, the mechanical mechanism of the new reinforcement was clarified, and a method for calculating the compression zone height of the beam in joints with the reinforcement was suggested, which improved the calculation accuracy by 13.7%.

Mechanism of bolt breakage in deep mining roadway under dynamic load and advanced strengthening support technology

To reveal the problem of local instability caused by bolt breakage and failure in deep mining roadway under impact dynamic loads, and explore strengthening support technologies that can reduce bolt breakage and improve the stability of roadway support bodies. This article adopts theoretical analysis, numerical simulation, and on-site industrial experiments to conduct research, investigate and obtain the fracture failure characteristics of bolt in deep mining roadway, quantitatively characterize the deformation pressure of roadway surrounding rock and dynamic load of overburden fracture, establish the mechanical criterion of bolt fracture, and analyze the influence law of different anchoring factors on bolt force under static load and dynamic and static load combination. The results show that when the anchor angle is different, the range under dynamic load increases by 169.3 % compared with static load, when the anchor length is different, the range increases by 863.3 % relatively, and the influence is significant; while the anchor support resistance increases by 11.6 % at different times, and the range decreases by 41.5 % at different pre-tightening torque. Then, based on this criterion, the influence law of bolt failure on the stability of surrounding rock is analyzed, and the optimal support scheme is obtained by simulation research, that is, bolt cable +U steel support scheme. After adopting this scheme for support, the deformation of surrounding rock is reduced by about 60 %, and the maximum concentrated stress of surrounding rock of roadway is reduced by 15.0 %. Based on this, the support parameters of the on-site roadway were optimized and a strengthening support scheme was determined, which includes “roof bolt surface support reinforcement + anchor cable combined with U-shaped steel deep reinforcement, and two strong bolts advanced reinforcement”. The on-site strengthening support practice showed that the bolt fracture rate was reduced by 87.3 %, the deformation of the surrounding rock was effectively controlled, and the stability was significantly improved.

A new hybrid steel–timber rocking seismic force resisting system equipped with U-shaped fuse connections

This paper introduces a new low-damage hybrid steel–timber rocking braced frame with self-centring capability and proposes a design methodology in the framework of Canadian design standards. This system consists of a gravity load-resisting timber frame and a steel concentrically braced frame acting as the lateral load-resisting system that is connected using U-shaped steel fuses. The self-centring capability is achieved by post-tensioning strands and rocking bases within the lateral load-resisting system. The system, along with its components, is first introduced. The proposed design method and system performance objectives are then presented. The seismic performance of the system and the proposed design procedure are validated through numerical analyses considering the interaction between the lateral and gravity load-resisting systems. The results of dynamic analyses confirm the enhanced seismic performance of the proposed hybrid system with almost no residual deformations after the earthquake. Moreover, the proposed design guidelines can accurately predict the system’s seismic response and demands imposed on the members.

Experimental evaluation of a U-shaped steel plate as a seismic fuse

This paper evaluates experimentally the cyclic response of a novel U-shaped steel plate proposed to dissipate seismic-induced energy through a unique mechanism called scissor bending. The cyclic behaviour of the U-shaped plate, including hysteresis response, plastic mechanism, strength and stiffness, ductility and energy dissipation capacities are examined. Four U-shaped steel plates varying in thickness are tested under cyclic loading. Furthermore, a mechanics-based method is proposed to estimate the stiffness and yielding strength of the fuse. The finite element model of the specimens is developed to reproduce their hysteretic behaviour and verify the stiffness and yielding capacity of the fuse. The results confirm that the proposed U-shaped steel plate demonstrate stable hysteretic behaviour and exhibit appreciable deformation ductility and energy-dissipating capacities. The U-shaped plate can be used as a seismic fuse in the design of frame structures.

Experimental Study on the Mechanical Performance of Column Underpinning Joints with Prestressed U-Shaped Steel Bars

To meet the requirements of highly efficient force transmission, easy operation and low damage in RC column underpinning engineering, a new underpinning joint with prestressed U-shaped steel bars was proposed. Static testing of seven specimens was carried out, and the number of the U-shaped steel bars, their arrangement and the pre-pressure acting on the joint were considered as the main parameters. The results demonstrated that the U-shaped steel bars might greatly increase the load-bearing capacity of the underpinning joint, and the more the number, the higher the capacity; the arrangement of the U-shaped steel bars also had a significant effect on the load-bearing capacity. Two pairs of the U-shaped steel bars arranged on the opposite sides of the column was better than that arranged on four sides. And the horizontal part of the UsSBs embedded in the column grooves was better than in the underpinning beams; the pre-pressure could effectively improve the sliding stiffness of the underpinning joint, while the effects on the load-bearing capacity was not obvious. Based on the curve of load-displacement, force process of the underpinning joint was divided into four phases: no slip, initial slip, interfacial slip expansion and punch slip, consequently a constitutive force-slip model was constructed. As a result, a simple mechanical model of the underpinning joint was established, and the calculation formula for the load-bearing capacity of the new joint was proposed. Finally, the engineering design expression was prepared according to the characteristics of the real underpinning project.

Performance of angle shear connectors for U-shaped steel concrete infilled composite beams

The current design codes i.e. AISC 360-16, CSA-S16-19, EC-04 etc. provide empirical relationships to estimate the capacity of shear connectors which were developed based on pushout tests of headed studs and channels connectors in exposed type sections. Therefore, these equations may result inaccurate predictions for strength of connectors in infilled-type sections. This study presents a detailed experimental study investigating the performance of angle connectors in composite sections. The testing program consisted two series of pushout tests. A total of 36 specimens were tested, considering the influence of several important parameters i.e. the length (Lc), height (hc), and web-thickness (tw) of angle connector, length of the weld (w) and the direction of shear connector (forward/backward) etc. The tests results demonstrated that with increasing connector height hs, and thickness, the maximum load Pmax and slip δu were increased. The connector direction didn’t change much the load-slip behavior. The prediction accuracy of the existing shear capacity models was evaluated by comparing the predictions with experimental results. The current equations were noticed to be highly inconsistent in predicting the shear capacity of angle connectors, especially in case of infilled type sections. When the entire length of connector was taken as the effective length, the models overestimated the shear capacity. While in case when the welding length was taken as effective length in calculations, the models underestimated the shear strength of angle connectors.

Experimental and numerical study of L-shaped irregularly concrete-filled steel tube columns under axial compression and eccentric compression

This paper proposes a new kind of L-shaped irregularly concrete-filled steel tube column (L-ICFSTC), which is formed by standardized steel (I-shaped and U-shaped steel) and infilled concrete, and studies its behavior under axial and eccentric compression through experimental and numerical investigation. Compared with L-shaped CFST column proposed by previous researchers, this kind of L-ICFSTC has more convenience in installation and construction as well as excellent behavior in mechanical performance. Firstly, the experiments of two full-scale specimens under axial compression and two full-scale specimens under eccentric compression are carried out. The L-ICFSTC specimens exhibits overall stability failure mode because the rapid increase of the horizontal deflection and strain at the midspan of the specimens is observed at the time of failure. In addition, the ultimate load of the L-ICFSTC under eccentric compression is related to the eccentric direction. Secondly, the finite element (FE) models of the specimens are established to simulate the loading process of experimental specimens. The results obtained from FE models agree well with the experimental results. Thirdly, through the parameter analysis based on the FE models validated above, it is found that the height of column, length of column limb, thickness of steel tube, material strength and eccentricity have influence on the stability performance of L-ICFSTC. The experimental and FE numerical results obtained in this study could provide the reference for establishing a complete design method of the L-ICFSTC in near future.

Seismic performance test of bolted U-shaped steel assembled shear wall

A new type of assembled shear wall with energy dissipation and seismic damping function was proposed for the damage mechanism and weak points of typical assembled shear wall structures under strong earthquake effects. Using a combination of model tests and numerical simulations, four new assembled shear wall specimens with a scaling ratio of 1:1.54 and a shear-to-span ratio of 1.52 were designed and fabricated. The corresponding seismic performance tests were carried out. The effects of the number of bolts, axial compression ratio and longitudinal reinforcement ratio of edge members on the damage mode, hysteresis performance, bearing capacity, deformation performance, stiffness degradation and energy dissipation capacity of the specimens were systematically analyzed. The test results show that the damage mode of each specimen is basically the same as that of the common shear wall with the same shear-to-span ratio, which is bending-shear type damage However, the new assembled shear wall has more excellent hysteresis performance and energy dissipation capacity. Friction between the steel plates of the horizontal joints consumes a lot of energy and further inhibits wall damage. The energy dissipation value at the point of destruction of the wall is significantly higher than that of ordinary cast-in-place wall. The energy consumption value of the specimen PFSW is about 6 times that of a cast-in-place wall. When the number of bolts decreases, hysteresis performance decreases and wall deformation increases. The decrease of axial pressure ratio or longitudinal reinforcement ratio of edge members leads to the decrease of bearing capacity and increase of ultimate displacement of shear wall. Finally, the finite element model of the corresponding specimens was established by ABAQUS software. The simulation results were in good agreement with the test results, which indicated the correctness of the proposed model. And it can be applied to the analysis of new assembled shear walls.

Experimental and Numerical Study of Strengthening Prestressed Reinforced Concrete Beams Using Different Techniques

This study aimed to evaluate the static response of prestressed reinforced concrete beams strengthened in their flexure and shear properties using different strengthening techniques, steel plates, and externally bonded woven carbon fiber fabric (WCFF). The experimental work involved testing twenty large-scale prestressed reinforced concrete beams with a length of 3000 mm, and cross-sections measuring 400 mm in height and 200 mm in breadth were cast in the factory and tested in the laboratory. Four beams without prestressing served as the reference beams; two unbonded pre-tensioned beams served as the control beams, and the remaining fourteen beams were strengthened with steel plates and externally bonded woven carbon fiber fabric (WCFF). Eight of the beams were strengthened with 4 mm thick steel plates and tested under a monotonically increasing load with manual readings recorded. The remaining six beams were strengthened with 0.5 mm thick WCFF and tested under a monotonically increasing load with manual readings recorded. The variables considered included the strengthening techniques (FRP composite sheets, steel plates), the types of strengthening (slices, U-shaped), and the flexural and shear capacities of the strengthened beams. All the implemented strengthening techniques yielded enhancements in both the flexural and shear strength outcomes of the beams compared to their respective controls. The most significant increase in load capacity, whether in terms of ultimate load or first crack load, for the prestressed concrete beams’ flexure properties occurred when strengthening with U-shaped steel plates. Additionally, the greatest reduction in deflection at the point of reaching the maximum load for the prestressed concrete beams, in terms of their flexure properties, was observed when strengthening with U-shaped steel plates. Similarly, the maximum load increase for the prestressed concrete beams, in terms of their shear properties, was achieved through strengthening with U-shaped woven carbon fiber fabric wrapping. Furthermore, a finite element model was created to simulate various experimental specimens. The finite element model’s results exhibited harmony with the experimental results, affirming the efficacy of the presented finite element model.

An experimental and numerical study on the rotational behavior of bolted glulam beam-to-column connections reinforced by double U-shaped welded steel sections

The study presented the results of the experimental and numerical study on the rotational behavior of the bolted glulam beam-to-column connections reinforced by double U-shaped welded steel sections. To demonstrate the enhancement efficiency of double U-shaped steel sections on the performance of bolted glulam beam-to-column connections, both unreinforced and reinforced bolted glulam connections were tested under the monotonic pure bending scenario and the cyclic loading scenario with combined shear and bending, respectively. Besides, detailed finite element (FE) models of the reinforced bolted glulam beam-to-column connections were developed and then validated by the experimental results. The rotational behavior of the unreinforced connections and that of the reinforced connections were compared in terms of damage modes, performance parameters, stiffness degradation, and cumulative energy dissipation, respectively. The effects of two configurational parameters on the rotational behavior of the reinforced connections were analyzed, which were the diameter of the holes predrilled in the beams and the width-to-thickness ratio of the top plates of the U-shaped steel sections. In the monotonic pure bending tests, the rotational stiffness of the reinforced connections is 1.20–2.22 times that of the unreinforced connections. The rotational stiffness of the reinforced connections is enhanced as the width-to-thickness ratio of the top plates is reduced. Furthermore, when the diameter of the holes predrilled in the beams is enlarged from 22 mm to 30 mm, the rotational stiffness and the ultimate moment resisting capacity of the reinforced connections are reduced by 27.8% and 16.6%, respectively. As for the cyclic loading tests, when reinforced with U-shaped steel sections, the ultimate moment resisting capacity and the rotational stiffness of the bolted glulam connections are enhanced by 26.7% and 17.0%, respectively. The degradation of the secant stiffness of the unreinforced connection is more severe, indicating that the reinforcement with double U-shaped steel sections is an efficient damage-resistant technique for both new and existing bolted glulam connections. based on the developed FE models, both the failure modes and the moment-rotation curves of the reinforced connections under the monotonic pure bending scenario can be predicted.

Research on Reinforcement Technology of Existing Frame Structure with Externally Attached U-Shaped Steel Plate Sub-Structure

With the improvement of building technical requirements and the updating of standards, the demand for the reinforcement of existing buildings is increasing. In order to solve the problem regarding the low economic applicability of the traditional seismic retrofit method, this paper proposes a seismic retrofit method for an externally attached U-shaped steel plate sub-structure that follows the concept of “reinforcing while using”, is composed of a U-shaped steel plate and herringbone channel steel, and can meet the needs of multiple retrofits. Based on the results of a pseudo-static test, the mechanical properties of one unreinforced frame and three reinforced frames with different specifications for the U-shaped steel plate sub-structure were comparatively studied, and the effectiveness and rationality of the reinforcement method were analyzed. The results show that the externally attached U-shaped steel plate sub-structure has good deformation and energy dissipation capacity and can effectively improve the horizontal bearing capacity of an existing frame without changing the original failure mode. The bearing capacity of the three reinforced frames was 1.43, 1.89, and 2.57 times that of the unreinforced specimen. The initial lateral stiffness of the frame also increased significantly, namely, to 1.41, 2.02, and 2.08 times that of the unreinforced specimen, and the stiffness degradation rate decreased. The seismic performance of the original frame was greatly improved.

Seismic performance of T-shaped CFST column to U-shaped steel composite beam joints

U-shaped steel-concrete composite beams have the advantages of high bearing capacity, excellent fire resistance and quick construction, when it is used with special-shaped concrete-filled steel tube columns could achieve the architectural effect of no exposed beams and columns in the interior, showing great application potential in residential buildings. In this study, three full-scale T-shaped CFST column to U-shaped steel composite beam joints with different configurations were tested under cyclic loads. The damage modes, and hysteresis performance of the joint were discussed in detail. The test results indicated that the three joints with side plate connection all showed plastic hinge damage at the beam ends of which hysteresis curves show bowed shape, with excellent energy dissipation. The setting of truss reinforcement within the U-shaped steel beam could effectively improve the ductility of the member. Based on the validated finite element model, the effects of side plate configuration, the side plate position, and tube wall thickness on the seismic performance of the joints are investigated. The design methods for the bending capacity of the joints have also been proposed.

Fire experiment and fire design method of U-shaped steel-concrete composite beams

Four U-shaped steel-concrete composite beams (USCB) were designed and tested under the ISO-834 standard fire curve and distributed vertical load. The research parameters were the load ratio and shear connector form. The temperature distribution, fire resistance, and failure modes of the USCB specimen were investigated. The fire tests showed that the failure mode of the specimen is flexural damage and the connection interface between the flange and web of the composite beam remains intact. The temperature of the fire-resistance reinforcements is below 500°C when the specimens reached the fire resistance, which is in the early stage of material degradation and has high residual strength. The fire resistance increased (improve by 51%) with the decrease of load ratio (0.7 to 0.4) and was not affected by the shear connector form. Then a numerical simulation was applied to establish the temperature field model and fire resistance model of USCB, and the simulation results of the temperature field and fire resistance were in good agreement with the test results. The parameter analysis indicated that the load ratio, the diameter of fire-resistance reinforcement and fire protection layer have an obvious impact on the fire performance. Based on the heat transfer mechanism analysis, the temperature calculation methods for U-shaped steel, fire-resistant reinforcement and concrete were proposed. Moreover, a flexural bearing capacity calculation method for the USCB under the standard temperature rise curve is proposed, which can be applied to calculate fire resistance.

Flexural Capacity of Bolted U-Shaped Steel–Concrete Composite Beams under Monotonic and Cyclic Loading

Flexural Capacity of Bolted U-Shaped Steel–Concrete Composite Beams under Monotonic and Cyclic Loading