Full-scale Specimens Research Articles

Experimental study of friction damping connections for prefabricated self-centering rocking structural elements

Self-centering rocking structural systems provide solutions for prefabricated buildings to achieve better seismic resilience. A well-designed connection of the self-centering rocking structural elements is critical to provide stable supplemental damping to the system. In this study, an innovative friction damping connection was proposed that could better match the gap-opening-closing motion of the rocking elements. Firstly, prototype experiments were carried out to investigate the connection’s mechanical behavior. The brake pad-stainless steel interface exhibited smooth sliding without chatter, stick-slip, or damage. The average static and kinetic friction coefficients were 0.30 and 0.28, respectively, showing negligible dependence on surface pressure, amplitude, or frequency. Then, the proposed connections were applied to the prefabricated shear wall-rocking coupling beam subassembly. Quasi-static cyclic loading tests on 5 full-scale specimens of the subassembly showed typical flag-shaped hysteresis curves, and the connections performed well as expected. Moreover, the theoretical analysis accurately reflected the hysteretic behavior of the specimen. Adjusting the connection’s frictional force changed the initial damping moment ratio (IDMR) of the coupling beam, determining the rocking system’s energy dissipation and self-centering capability. A reasonable IDMR value ranged from 0.8 to 0.9.

Experimental and Numerical Investigation of Buckling Behaviour in Q690 High-Strength Steel Tubes Under Combined Axial Compression and Bending Loads

This paper investigates the buckling behavior of Q690 high-strength steel tubes under combined axial compression and bending loads through experimental testing and finite element analysis (FEA). A total of 27 full-scale specimens with varying slenderness ratios (λ) and diameter-to-thickness (D/t) ratios were tested to evaluate their load-bearing capacity, deformation characteristics, and failure modes. The experimental setup replicated real-world conditions, with constant axial loads applied alongside incremental bending moments until failure occurred. FEA models, developed using ABAQUS, incorporated geometric imperfections and material nonlinearities to simulate realistic structural behavior and predict critical buckling moments. The comparison between experimental and numerical results showed strong agreement, with deviations ranging from 5.6% to 7.9%, confirming the reliability of the simulations. The findings indicate that tubes with higher D/t ratios are more sensitive to imperfections, experiencing significant reductions in post-buckling moment capacity, while those with lower D/t ratios demonstrated greater resistance to buckling and maintained higher structural integrity. The transition between global and local buckling modes was effectively captured by both experimental and numerical approaches, validating the robustness of the models. This study emphasizes the importance of accounting for geometric imperfections and residual stresses in design practices to ensure the safety and reliability of high-strength steel structures under combined loading conditions. Additionally, the results underscore the effectiveness of advanced FEA tools in predicting structural behavior, providing valuable insights for improving design codes and practices. Future research is recommended to explore dynamic loading scenarios, such as wind or seismic effects, to further enhance the applicability of Q690 steel tubes in critical infrastructure projects.

Experimental study of reinforced concrete rocking columns with steel tubes under cyclic loading

To reduce damage and enhance the seismic resilience of reinforced concrete (RC) columns, this study introduces a new type of RC rocking column installed with steel tubes for end protection and steel angles as external dampers to enhance the energy dissipation capacity. Six full-scale specimens including four RC rocking columns without steel angles and two with steel angles were tested under cyclic loading. The results demonstrate that the proposed end protection measure significantly mitigates the damage to RC rocking columns. The residual deformation of specimens was small after testing. As the axial compression ratio increases, the strength of RC rocking columns also increases. However, a higher axial force results in greater damage and increased residual deformation. Steel angles significantly enhance the strength, stiffness, and energy dissipation capacity of RC rocking columns. Additionally, the repair of the RC rocking column is straightforward, and the recovery of its function is rapid after strong earthquakes.

Effective Concrete Failure Area for SC Structures Using Stud and Tie Bar Under Performance Tests.

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars.

Mechanical Response of Hot-Mixed Epoxy Asphalt Concrete Steel Deck Pavement Under Thermal and Load

In recent years, fatigue cracking in orthotropic steel bridge deck pavements has become a significant concern, so the investigation of the mechanical response of the pavement layer has become a central focus in pavement structure design. This experiment subjected a full-scale specimen to a constant amplitude dynamic load of 60 kN to 300 kN over 2 million cycles. Throughout the testing, a circulating water bath elevated the temperature of the pavement layer from 15 °C to 50 °C. Key locations were monitored for strain and deflection data, facilitating an investigation into the mechanical response of the epoxy asphalt pavement system under the effects of temperature and load. The results indicate that the maximum transverse strain at the bottom of the steel deck occurs at the U-rib weld aligned with the load center, reaching 190% of the initial loading strain. Meanwhile, the maximum transverse strain on the pavement surface is observed at the U-rib weld adjacent to the loaded area, measuring 167% of the initial strain. The maximum longitudinal strain is lower than the maximum transverse strain. In the load zone, the longitudinal strain between the U-ribs exceeds that at the U-rib weld. Both transverse strain and relative deflection increase as the load intensifies. The relationship between transverse strain and applied load is characterized by an exponential function, while deflection exhibits a cubic relationship with the applied load. Elevated temperatures also contribute to increased transverse strains at both the bottom of the steel deck and the pavement surface, following an exponential trend. Relative deflection is primarily influenced by the applied load and remains relatively unaffected by temperature variations. When accounting for the coupling of load and temperature, the maximum transverse strains at both the bottom of the steel deck and the pavement surface can be modeled as an exponential function of the independent variables: load and temperature.

Group resistances of tensile-loaded anchored-bolted connections with CFST columns: Tests, simulations, and theoretical models

The performance of the connections in concrete-filled steel tubular (CFST) columns fabricated with a group of two anchored blind-bolts under tensile forces is evaluated. Based on the bolt group arrangement, two sets of experiments, comprising eight full-scale specimens, were tested. Test parameters include the presence of concrete, bolt anchorage length, pitch distance, and gauge distance. Further, numerical models were developed, which, after validation, were used for parametric studies. Key findings indicate that bolt gauge distance, anchorage length, concrete grade, and column cross-section slenderness significantly influence the connection behaviour, but pitch distance has the least influence. Tube and concrete failure modes, as well as critical gauge and pitch distances, are identified, which govern tube deformation and concrete crushing zones. Finally, a bi-linear theoretical model is developed that can provide a fair prediction of the connection strength and stiffness.

Comparative study of RC and ECC beam-column connections with shear deficit spacing under quasi-static conditions

ABSTRACT This study evaluates the seismic performance of beam-column joints using Engineered Cementitious Composite (ECC) compared to Reinforced Concrete (RC) under quasi-static loading. Five full-scale specimens, one control RC specimen and four ECC specimens with varying configurations were tested. The study examines parameters such as load-bearing capacity, ductility, energy dissipation, and cracking behavior. Results revealed that ECC significantly outperformed conventional concrete, increasing the mean ultimate load by 28.96% and ductility by 23.95% in specimens with proper shear spacing. While ECC specimens with shear deficits exhibited 26.75% lower energy dissipation, extending ECC into the plastic hinge zones increased dissipation by 58.06%. These findings demonstrate ECC’s effectiveness in enhancing seismic resilience, particularly in cases with inadequate shear reinforcement, and underscore its potential as a viable alternative to traditional reinforcement strategies.

Hybrid modular construction system “INNO3DJOINTS”: Experimental behaviour and numerical modelling of isolated sub-frames

With the growing demand for sustainable, cost-effective and overall-efficient building solutions, the need for dependable modular construction systems is steadily on the rise. In the present paper a novel hybrid modular construction system named INNO3DJOINTS is introduced, employing cold-formed welded steel tubular columns, fabricated according to EN 10219, and cold-formed steel thin-wall section based truss-girders, joined by the innovative plug-and-play (P&P) connector, designed to provide ease-of-assembly and -disassembly. The experimental investigation conducted on isolated sub-frame configurations of the novel system is presented, where 6 full-scale specimens were subjected to horizontal and vertical loading. The test configurations differed in the P&P joint socket thickness and the absence/presence of the light steel framing (LSF) wall, encased with oriented strand board (OSB). In addition, a numerical model for predicting the system's global behaviour is proposed, developed in SAP2000. Initially, the behaviour of the employed P&P joint configurations, categorized as partial-strength, is characterized using experimental and validated ABAQUS finite element model (FEM) data, resulting in a spring model implemented into the global FEM. Finally, the numerical and experimental results are compared and discussed, leading to conclusions regarding the system's 2D structural performance, identified behaviour governing phenomena, P&P joint influence, LSF wall and OSB contribution, as well as the capabilities of the developed FEM.

Optimization study of strengthened T-shaped concrete-filled steel tubular (CFST) column-steel beam joint

In this paper, a strengthened T-shaped concrete-filled steel tubular (CFST) column-steel beam joint is proposed. The joint is strengthened in the core region of the column wall as well as the beam, to avoid buckling of the column wall and outward displacement of the plastic hinge at the beam end. To study the damage modes and seismic performance of the joint, low-cycle loading experiments on two full-scale specimens of the joint were carried out. The results show that each specimen was damaged by plastic hinging of the steel beam flanges, the column walls did not buckle, and all had a good seismic performance. In addition, Abaqus finite element software was utilized to optimize the joints by analyzing the effects of changing the dimensions of the strengthened column and modifying the structure of the beam-column connection. Simulation results show that increasing the thickness and height of the strengthened column wall enhances the joint's load capacity, stiffness, and energy dissipation. it is recommended that the width-to-thickness ratio of the strengthened columns should be at most 0.08 and the beam-to-column height ratio should be kept at least 1.3. Additionally, two optimization methods, reducing the wall thickness of the steel corbel and weakening the steel beam flange, can effectively reduce weld tearing at the beam-to-column connections, while guaranteeing a good seismic performance. It is suggested that the slope of the steel corbel is not less than 1:6.25, and the weakening ratio of the steel beam flange is not greater than 0.267.

Passing-through I-plates-to-SHS moment resisting joints subjected to symmetric bending moments

When using hollow structural section (HSS) members in multi-storey buildings, beam-to-column moment resisting connections’ design raises critical questions to tackle. With conventional welded and bolted joints’ response being generally very flexible, the design resistance becomes governed by a deformation criterion rather than a strength criterion. This underscores the necessity for smart reinforcement techniques. A widespread solution is the diaphragm approach, in which the stiffeners usually protrude over the tubular column. The solution of plates passing through the HSS column is another stiffening option which was studied recently for CHS, yet, SHS columns have not been subject to comparable scrutiny. The objective of this paper is to study experimentally, numerically, and analytically the mechanical behaviour of I-beam-to-SHS column moment resisting joints using passing through I-plates under symmetric bending moments. The testing of two full-scale specimens corroborates previous findings with CHS columns in the elastic regime. However, significant deviations were observed in the post-peak response, revealing new insights into the behaviour of SHS columns. Failure was due to progressive buckling of passing through plates and yielding of tube-wall in transverse compression. A finite element model using solid and contact elements is developed and validated against experimental data. This model underscores how loads are redistributed between the tube wall and passing plates. A simplified version of the FE model is used to perform a thorough parametric numerical analysis on 101 configurations expanding upon the experimental test database by varying geometrical parameters such as passing plate thickness, tube, and beam dimensions. Finally, an analytical model integrating the different components of the joint is proposed to evaluate the initial rotational stiffness and the bending resistance.

Experimental study on concrete-filled L-shaped steel tubular columns and beam-columns

Concrete-filled L-shaped steel tube (CFLST) is an efficient structural form for corner columns in high-rise buildings, which avoids column protrusion. This paper presents an experimental and theoretical study on the structural behavior of CFLST columns and beam-columns. A total of nine full-scale specimens (i.e., three stub columns, two slender columns, and four slender beam-columns) was tested under compressive loads and the specimen ends were free to rotate about a geometric axis. Plastic local buckling was observed for the stub columns and the confinement effect was not obvious. Flexural buckling occurred for the slender columns and beam-columns. With the increase in the applied load, the neutral axis shifted to the compressive side of the beam-column. Performance of current design codes, which apply for rectangular CFSTs, on predicting the ultimate capacities of CFLSTs was assessed. The prediction for section capacity was conservative and it was likely caused by the reduction in the design strength of concrete. The buckling curve in design codes for rectangular CFSTs was applicable for CFLST columns whereas the interaction relationship specified in design codes underestimates the ultimate capacities of CFLST beam-columns. Based on fiber element analysis, out-of-plane bending moment was found in the tested CFLST slender members and the values were quantified. A new interaction relationship was proposed for CFLST beam-columns, which exhibited good agreement with experimental and numerical results. Finally, design methods were recommended for CFLST columns and beam-columns.

Experimental and analytical investigation of bracket moment connection for precast concrete beam-to-composite column joints

In large industrial buildings, precast prestressed concrete beams and composite columns are appealing to achieve longer span and higher story height, with temporary supporting and scaffolding minimized. To facilitate field erection of moment connection between precast beams and composite columns, a bracket connection transferring beam loads to the column by connecting the beam to a composite bracket attached to the column has been developed. Since precast beams are lap-spliced and integrated with the bracket by concrete engagement at the interfaces, the connection performance depends on beam lap length and load transfer details (i.e., concrete shear keys). In this study, the seismic performance of precast prestressed concrete beam-to-composite column joints with the bracket connection was experimentally and analytically investigated. Cyclic loading tests were conducted on four full-scale specimens with different beam lap lengths and load transfer details. For the specimens with a longer beam lap length, the bracket connection successfully transferred the beam flexural strength to the column with the connection barely damaged. The governing failure mode was beam flexural yield occurring at the bracket end. However, for the specimen with a shorter beam lap length, relative slips at the interfaces of the beam and bracket occurred and thus the strength was governed by the bracket connection. Excellent ductility satisfying the acceptance limit of special moment frame in AISC 341 was achieved in all specimens. The load transfer at the bracket connection through concrete shear keys and other details were further investigated through finite element analysis. Design models to predict the connection strength were proposed and the validity of the models was verified through comparisons with the tests and analyses.

Seismic performance of a novel concrete-filled steel tube column to continuous reinforced concrete beam joint with multiple openings in the core region

This study developed a novel concrete-filled steel tube column to continuous reinforced concrete beam joint with multiple openings in the core region, aiming to eliminate field welding and improve construction efficiency. To evaluate the seismic performance of the joint, six full-scale specimens were tested under cyclic loading, which and a series of numerical simulations were implemented upon refined models. The effects of reinforcement ratio, steel tube thickness, and concrete strength on the failure mode and the mechanical performance degradation of the joint were quantitively evaluated. The results indicated that depending on the beam-column flexural capacity ratio, three typical failure modes, i.e., compression bending failure at the column end, shear failure at the joint core region, and flexural failure at the beam plastic hinge region, were observed. Among them, the flexural failure-dominated joint possessed the best energy dissipation capacity and a high ductility coefficient greater than 3.72. Moreover, increasing the thickness of steel tube within the core region can effectively compensate for the reduction of seismic performance caused by multiple openings, and a preliminary value of at least 2.5 times the thickness of column steel tube is recommended. This novel joint configuration exemplifies a balance between structural integrity, construction efficiency, and mechanical performance, rendering it a feasible alternative for frame structure in seismic-prone regions.

Flexural mechanical properties of H-shaped steel-bamboo scrimber composite beams

To improve the torsional buckling resistance and enhance the load-bearing capacity and ductility of H-shaped steel beams with carbon reduction materials, the concept of combining H-shaped steel with bamboo scrimber has been proposed, in which the bamboo scrimber, an eco-friendly, lightweight, and high-strength material, promises significant structural benefits. Five full-scale specimens were designed and tested, including one H-shaped steel, two bamboo scrimber beams, and two composite beams. Additionally, further simulation tests were conducted using the verified finite element model (FEM). The experimental results revealed a remarkable increase in the ultimate bearing capacity of the composite beams by 96.5 % compared to bamboo scrimber-only beams and 72.7 % compared to steel-only beams. Meanwhile, distinct from the brittle fracture characteristics of the bamboo scrimber beams, which include instantaneous crack propagation and interlaminar cracking, the composite beams exhibited localized vertical cracks within the beam's tensile zone, effectively avoiding the torsional buckling issue of the H-shaped steel beam. The results further demonstrated that increasing the cross-sectional size of the composite beams can significantly enhance their flexural stiffness (up to 669 %), and reduce the deflection at the ultimate flexural moment. When the area of the bamboo scrimber in the cross-section was reduced with an unchanged steel profile, the initial stiffness dropped to 79 % without incurring any structural instability. Furthermore, by integrating the experimental and simulation results, a fiber element model for this composite beam structure is proposed to predict the maximum flexural moment value in the ultimate state. A corresponding calculation program was developed, and it is found that the calculated predicted ultimate flexural moment values exhibited negligible deviation from both experimental and FEM results, with AV of 1.0001, AAE of 2.21 %, and COV of 3.28 %.

Fretting fatigue life prediction of full-scale dovetail joints using the theory of critical distances with mesh control

The fretting fatigue life of full-scale dovetail joints in two contact configurations was estimated using the theory of critical distance with the area method (TCD-AM) and the mesh control method (TCD-MC). The TCD-MC method demonstrated prediction accuracy comparable to the traditional TCD-AM method, while improving computational efficiency by 85 %. By incorporating a calibration strategy with the TCD-MC method, the predicted fatigue life was within the scatter band of factor 3 when compared with the experimental data, indicating its reliability. The proposed parameter-fitting method for TCD-MC yielded results nearly identical to the conventional method, while reducing the workload by 75 %. The TCD-MC method is expected to provide a potentially novel and convenient approach for fretting fatigue life prediction in full-scale specimen.

Development of a novel full-scaled self-centering brace with notched steel tubes

A novel self-centering brace with notched steel tubes (SCB-NST) was developed and experimentally studied. The proposed SCB-NST consists of a novel notched steel tube (NST) for energy dissipation and disc springs for self-centering, respectively. Three full-scaled specimens were tested to investigate the hysteresis behavior under cyclic loading. These specimens include a brace with NST only, a brace with disc spring only, and an SCB-NST. The first two tests were specifically conducted to obtain the contributions of the NST and disc springs alone, respectively. The test results illustrate that the first proposed NST displays excellent energy dissipation and deformation capabilities. The proposed SCB-NST exhibits a stable flag-shaped hysteresis behavior, distinguished self-centering, and significant energy dissipation capacity without residual displacement. Furthermore, experimental findings reveal that the disc spring functions as a secondary defense line of the SCB-NST system upon sudden failure of the NST. The cyclic test of the brace with disc spring only shows that the friction between the disc springs should not be neglected, especially when quantities of large-diameter disc springs are stacked. The modular design of the proposed SCB-NST facilitates the replacement of energy-dissipating components, allowing for efficient maintenance and ultimately achieving the design objective of promoting reusability and resource conservation. The SCB-NST, equipped with two NSTs featuring different ultimate displacements, has been confirmed through finite element analysis to have three defense lines, which improves the reliability and redundancy of the SCB-NST system. The parametric finite element analysis results reveal that the thickness of the energy-dissipation ring has the most significant influence on the load-bearing capacity and energy-dissipation capability of the SCB-NST. Concurrently, the pre-pressed force of the disc spring is crucial for eliminating the residual displacement of the SCB-NST.

Bearing capacity and failure behavior of segments with a mid-span opening of a shield subway tunnel

This paper investigates the load-bearing properties and failure mechanisms of shield segments with a circular mid-span opening in shield subway tunnels. Two full-scale specimens with opening diameters of 100 and 200 mm were manufactured and tested, revealing that with an increasing opening diameter, the failure mode transferred from uniform tensile fracture of inner arc concrete to the peeling and crushing of the outer arc concrete. Moreover, the loading process can be divided into four stages, i.e. elastic, plastic expansion, failure, and ultimate stages, and each stage shares a critical load. Subsequently, numerical models were established using the elastoplastic damage constitutive of concrete, and its reliability is verified by the experimental results. Afterward, parametric analysis was performed considering the plain concrete loss and reinforced concrete loss. The analysis results show that the plain concrete loss significantly weakens the cracking load of the segment, while reinforced concrete loss has the greatest impact on the failure load. Finally, a comparative analysis is conducted between the bearing characteristics of the local failure segment, standard shield segment, and the segment joint. Overall, the research results can provide a theoretical basis for the field reinforcement and the safety assessment of local failed shield tunnels.

Evaluation of interactional behavior of suspended ceilings and partition walls through shake table tests

Earthquakes cause seismic losses due to direct and indirect effects of damage to structural and nonstructural elements in buildings. Suspended ceiling-to-partition wall (SCPW) systems, the most earthquake-vulnerable nonstructural elements, may suffer severe damage under earthquakes even with low and moderate intensities. However, there is still limited research on investigating the seismic performance of SCPW systems in buildings located at low- or moderate-seismicity regions. This study aims to experimentally evaluate the seismic response of SCPW systems using shake-table test program and to deeply investigate the interaction between a partition wall and a ceiling. To do this, the shake table program was carried out using a full-scale specimen employing SCPW systems and its results were summarized and analyzed. The frequencies measured at the partitions were similar to those measured at the test frame whereas the fundamental frequency of the suspended ceiling was decoupled to the floor acceleration of the test frame. The full-height partitions presented relatively good seismic response because of the sufficient lateral support at the top of the partition, whereas severe damage was mainly concentrated on the ceiling elements due to pounding effects. The partial-height partitions with improper anchor detailing to adjacent suspended ceiling suffered severe damage. Such poor seismic performance is because they suffer pounding effects resulting from the interactional behavior which are magnified in partition walls with lack of sufficient lateral supporting. Both partial-height partitions and ceiling elements were seriously damaged.

Fatigue behavior and damage mechanism of steel plate-UHPC composite bridge deck subjected to negative bending moment

In order to investigate the fatigue behavior and failure mechanism of steel plate-UHPC composite bridge deck under hogging moment, a total of four full-scale specimens with two class of reinforcement ratio (Three specimens with reinforcement ratio of 1.58 %, 1.69 %, 1.86 %, respectively, which called longitudinal specimen. One specimen with reinforcement ratio of 0.89 %, which called transverse specimen.) were designed and tested under fatigue loading. Test results reveal that when the fatigue loading ratio was 0.25 with maximum load of 0.8 times of the static cracking load, taking the crack width of 0.10 mm as the fatigue failure criterion, the fatigue life of longitudinal specimen over 16 million cycles. However, the fatigue life of transverse specimen was only 9.08 million cycles. The longitudinal reinforcement restricts the propagation of fatigue cracks along the depth of the UHPC slab, and tensile fracture of the steel fibers occurred in the region between the top layer of longitudinal reinforcement and the UHPC surface. The fatigue damage mechanism resulting from fatigue degradation of the UHPC layer in the tension zone is identified. In addition, The fatigue design of the steel plate-UHPC composite bridge deck should be controlled by the durability rather than the strength. The established tensile S-N curve with 0.05 mm critical UHPC crack width could be used evaluate the fatigue cracking resistance of composite bridge deck.

Lap Length of Steel Bars Between Novel Prefabricated Wall and Foundation Floor Structures: Full-Scale Experiment

In the context of promoting environmentally friendly practices, prefabricated components are increasingly utilized in civil engineering design and construction. Prefabricated shear walls, in particular, have become prevalent in contemporary residential and office buildings. Following an economic analysis of the construction steps for prefabricated walls, Shanghai Hengxu Energy Conservation Company developed a novel type of prefabricated wall for use in building basements. This innovative wall consists of two thin plates joined by distributed tie pieces, with an internal steel bar cage positioned between them. The core concrete is cast in place between the plates. The wall is designed to withstand water and soil pressures from underground and connects to the basement floor through overlapping steel bars. The effectiveness of the wall's integration with the foundation floor depends on the lap length of the steel bars, a critical factor in structural design and construction. To optimize the lap length, three full-scale specimens were tested, differentiated by varying steel bar lap lengths: 0.8 lae, 1.0 lae, and 1.2 lae, where lae represents the basic anchorage length. The specimens were subjected to horizontal loading to assess failure modes, crack propagation, load-displacement behaviors, and stress-strain responses of the reinforcements. The experimental results revealed that increasing the lap length of the steel bars beyond 0.8 lae does not significantly enhance the bearing capacity or deformation potential of the specimens.