Search Results (65)

This study investigates two novel prefabricated frame joints: prestressed steel sleeve-connected prefabricated reinforced concrete joints (PSFRC) and non-prestressed steel sleeve-connected prefabricated reinforced concrete joints (SSFRC). A total of three PSFRC specimens, four SSFRC specimens, and one cast-in-place joint were designed and fabricated. Seismic performance tests were conducted using different end-plate thicknesses, grout strengths, stiffener configurations, and prestressing tendon configurations. The experimental results showed that all specimens experienced beam end failures, and three failure modes occurred: (1) failure of the end plate of the beam sleeve, (2) failure of the variable cross-section of the prefabricated beam, and (3) failure of prefabricated beams at the connection with the steel sleeves. The load-bearing capacity and initial stiffness of the structure are increased by 35.41% and 32.64%, respectively, by increasing the thickness of the end plate. Specimens utilizing C80 grout exhibited a 39.05% higher load capacity than those with lower-grade materials. Adding stiffening ribs improved the initial stiffness substantially. Specimen XF2 had 219.08% higher initial stiffness than XF1, confirming the efficacy of stiffeners in enhancing joint rigidity. The configuration of the prestressed tendons significantly influenced the load-bearing capacity. Specimen YL2 with symmetrical double tendon bundles demonstrated a 27.27% higher ultimate load capacity than specimen YL1 with single centrally placed tendon bundles. An analytical model to calculate the moment–rotation relationship was established following the evaluation criteria specified in Eurocode 3. The results demonstrated a good agreement, providing empirical references for practical engineering applications. Full article

This study proposes a novel hybrid connection method for precast concrete shear walls, where the edge walls are connected using grouting splice sleeves and the middle walls are connected using grouted corrugated metallic ducts. To investigate the effects of connection type and axial compression ratio on structural performance, five shear wall specimens were tested under low-cycle reversed loading, with detailed analysis of their failure modes and hysteretic behavior. Based on experimental results and theoretical derivation, a restoring force model incorporating connection type was developed. The results demonstrate that hybrid-connected specimens exhibit significantly improved load-bearing capacity, ductility, and seismic performance compared to those with only grouted corrugated metallic duct connections. A higher axial compression ratio enhances structural strength but also accelerates damage progression, particularly after peak loading. A three-line skeleton curve model was established to describe the load, displacement, and stiffness relationships at key characteristic points, and unloading stiffness expressions for different loading stages were proposed. The calculated skeleton and hysteresis curves align well with the experimental results, accurately capturing the cyclic behavior of the hybrid-connected precast shear walls. Full article

As one type of critical load-bearing element in precast concrete structures, grouted sleeve (GS) connections enable efficient force transmission between reinforcing bars while maintaining structural integrity. Despite their growing global adoption, significant variations exist in design philosophies, construction specifications, and performance requirements among regional standards. Through bibliometric analysis, the most active countries and regions in GS application and research worldwide were identified, and the relevant technical standards established by these countries and regions were systematically reviewed. By comparing standards from Asia, the Americas, Europe, and Oceania, the main differences in design philosophy, construction quality control, material specifications, and performance requirements among these standards were analyzed and identified. The results show that different standards have a conceptual difference at the materials and quality control level, with one approach focusing on stricter management of sleeve materials and more detailed on-site construction requirements, and another approach emphasizing testing-based methods and third-party verification. These standards can be divided into the following two categories for the design limits of GS tensile performance: one category takes multiples of the yield strength of the connected reinforcing bars as the limit, and the other category takes multiples of the tensile strength of the connected reinforcing bars as the limit. Regarding mechanical performance requirements, standards using the ultimate tensile strength of the connected reinforcing bars as the control parameter differ from those using multiples of yield strength in their performance requirements for connections of low-strength and high-strength reinforcing bars. The variation in yield-to-tensile strength ratios among steel grades across different countries is a key factor leading to these different requirements. When using the uniform steel bar material properties specified in the standard for quantification, as the bar strength increases from approximately 240 MPa to 600 MPa, the minimum required ratio of the limits for standards based on multiples of yield strength and multiples of tensile strength increases from 0.79 to 1.07. When applying GS connections to reinforcing bars of varying strength levels, using fixed strength multiplier requirements may result in uneconomical designs or create technical challenges in achieving the required strength. Full article

Two types of reinforcing the half-tenon wood joints, one reinforced with an energy dissipation plate (SW-1) and the other by a steel sleeve with energy dissipation plate (SW-2), were designed. The pure wood beam–column joint specimen SW-0, specimen SW-1 and specimen SW-2 were experimented by the monotonic loading test, and the corresponding failure mode of joints and load–displacement curve were obtained. Based on the reliability of the verified finite element numerical model, the impact of thickness of the energy dissipation plate on the seismic performance of the SW-2 joint was analyzed. The research results show that the SW-0 and SW-1 joints exhibited significant tenon pulling phenomena, while the SW-2 joint did not show this phenomenon. The initial stiffness of the joints is significantly improved after reinforcement, and the initial stiffness of the SW-1 and SW-2 specimens is 2.64 and 7.24 times that of the SW-0 specimen, respectively. The ultimate loads of specimens SW-0, SW-1 and SW-2 are, respectively, 2.8 kN, 6.2 kN and 24.9 kN. The enclosed area of hysteresis loop and the slope of skeleton curve gradually increase as the thickness of the energy dissipation plate increases, resulting in a significant enhancement in energy dissipation capacity. The ultimate bearing capacity of the joint and the slope of skeleton curve exhibit negligible variation when the thickness of energy dissipation plate exceeds 2.0 mm, and the corresponding optimal thickness is obtained as 2 mm. Full article

As a common rebar connector in prefabricated projects, the grouted sleeve connection (GSC) affects structural performance during fire and seismic events. However, the combined impact of both factors may alter GSC performance, although most studies concentrate on high temperature or loading schemes. Few quantitative models are available for predicting the mechanical characteristics of post-fire GSCs under unidirectional tension, let alone cyclic loading. In this study, 18 GSC specimens were made and subjected to heating, water cooling, and cyclic loading. Thermal and mechanical loads caused rebar fracture below 400 °C, but pullout failure occurred beyond 400 °C. GSC performance declined as temperature and loading cycles increased. Based on this test and several previous investigations, predictive models with guaranteed rates for GSC performance after high temperature by water cooling under uniaxial and cyclic loading were constructed. According to the predictive models, the four parameters (including yield strength, ultimate strength, elastic modulus, and ultimate strain) of the GSCs using HRB400 rebars can be obtained. Full article

Traditional monolithic precast and precast prestressed concrete joints often face challenges such as complex steel reinforcement details and low construction efficiency. Grouting sleeve connections may also suffer from quality issues. To address these problems, a new precast prestressed concrete frame beam-column exterior joint using ultra-high-performance concrete (UHPC) for connection (PPCFEJ-UHPC) is proposed. This innovative joint lessens the amount of stirrups in the core area, decreases the anchorage length of beam longitudinal reinforcement, and enables efficient lap splicing of column longitudinal reinforcement, thereby enhancing construction convenience. Cyclic loading tests were conducted on three new exterior joint specimens (PE1, PE2, PE3) and one cast-in-place joint specimen (RE1) to evaluate their seismic performance. The study concentrated on failure modes, energy dissipation capacity, displacement ductility, strength and stiffness degradation, shear stress, and deformation’s influence on the longitudinal reinforcement anchoring length and axial compression ratio. The results indicate that the new joint exhibits beam flexural failure with minimal damage to the core area, unlike the cast-in-place joint, which suffers severe core area damage. The novel joint exhibits at least 21.7% and 6.1% improvement in cumulative energy consumption and ductility coefficient, respectively, while matching the cast-in-place joint’s bearing capacity. These characteristics are further improved by 5.5% and 10.7% when the axial compression ratio is increased. The new joints’ seismic performance indices all satisfy the ACI 374.1-05 requirements. Additionally, UHPC significantly improves the anchoring performance of steel bars in the core area, allowing the anchorage length of beam longitudinal bars to be reduced from 16 times of the diameter of reinforcement to 12 times. Full article

Split reinforced concrete column (SRCC), recognized for their exceptional ductility as seismic members, have faced developmental challenges due to the complexities of on-site casting. This study presents an innovative steel sleeve dry connection assembled SRCC, which is highly modular and simplifies construction, aiming to promote the engineering application of this innovative ductile seismic structural system. This study used a validated 3D finite element (FE) method to analyze internal joint forces. Key parameters influencing joint performance, such as the axial compression ratio (u) and cross-sectional equal division ratio (n), were analyzed in detail. Subsequently, a comparative of dynamic analysis of SRCC and normal reinforced concrete column (NRCC) frames was conducted, leading to recommendations for structural strengthening. The analysis revealed that the sleeve can provide effective protection for the core area of the joint. The ductility of SRCC is 2–3 times higher than that of NRCC. A detailed formula for calculating the shear-bearing capacity of SRCC joints was derived, showing strong agreement with numerical simulations. At a high seismic intensity of 9°, the acceleration response of the SRCC frame is significantly reduced compared to the NRCC frame, with the maximum base shear (MBS) decreasing by approximately 4 times, which significantly enhances its seismic performance. However, due to the larger inter-story displacements, it is necessary to incorporate energy-dissipating braces to comply with code requirements. Collectively, these findings underscored that the proposed SRCC system significantly enhances seismic performance by improving ductility and energy dissipation, providing a robust foundation for future studies and practical applications in seismic design. Full article

As mining operations extend to greater depths, they encounter critical challenges, including increased distances and substantial energy losses. To address the challenges of cold-energy loss in deep mine cooling systems and improve the working environment for miners, a long-distance sleeve-type insulated pipe system was developed. This system aims to mitigate thermal energy loss caused by heat transfer between the pipe and surrounding soil throughout the water transport path from the source to the deep mine in boreholes. A heat transfer analysis model was developed to assess the impact of variables such as transport time, water flow rate, inlet temperature, and insulation materials on the temperature of cold water. The study reveals that the temperature of cold water increases rapidly during transportation before reaching a stable state. Implementing modifications such as increasing the inlet temperature, enhancing the water flow rate, or utilizing materials with lower thermal conductivity can effectively mitigate temperature rises. Additionally, the novel sleeve-type design enhanced the pipe’s pressure-bearing capacity, reduced the required pipe length by 4752 m and minimized energy loss compared to traditional systems. In practical applications, after 45 h, the supply and return water temperatures increased by 0.45 °C and 0.38 °C, respectively, while maintaining cooling energy loss below 12%. This innovative solution improves mine cooling efficiency and provides guidance to reduce cold-energy loss. Full article

In view of the application status and technical challenges of steel–wood composite joints in architecture, this paper proposes an innovative connection technology to solve issues such as susceptibility to pry-out at beam–column joints and low load-bearing capacity and to provide various reinforcement methods in order to meet the different structural requirements and economic benefits. By designing and manufacturing four groups of beam–column joint specimens with different reinforcement methods, including no reinforcement, structural adhesive and angle steel reinforcement, 4 mm thick steel sleeve reinforcement, and 6 mm thick steel sleeve reinforcement, monotonic loading tests and finite element simulations were carried out, respectively. This research found that unreinforced specimens and structural adhesive angle steel-reinforced joints exhibited obvious mortise and tenon compression deformation and, moreover, tenon pulling phenomena at load values of approximately 2 kN and 2.6 kN, respectively. However, the joint reinforced by a steel sleeve showed a significant improvement in the tenon pulling phenomenon and demonstrated excellent initial stiffness characteristics. The failure mode of the steel sleeve-reinforced joints is primarily characterized by the propagation of cracks at the edges of the steel plate and the tearing of the wood, but the overall structure remains intact. The initial rotational stiffness of the joints reinforced with angle steel and self-tapping screws, the joints reinforced with 4 mm thick steel sleeves, and the joints reinforced with 6 mm thick steel sleeves are 3.96, 6.99, and 13.62 times that of the pure wooden joints, while the ultimate bending moments are 1.97, 7.11, and 7.39 times, respectively. Using finite element software to simulate four groups of joints to observe their stress changes, the areas with high stress in the joints without sleeve reinforcement are mainly located at the upper and lower ends of the tenon, where the compressive stress at the upper edge of the tenon and the tensile stress at the lower flange are both distributed along the grain direction of the beam. The stress on the column sleeve of the joints reinforced with steel sleeves and bolts is relatively low, while the areas with high strain in the beam sleeve are mainly concentrated on the side with the welded stiffeners and its surroundings; the strain around the bolt holes is also quite noticeable. Full article

As a critical component of lifeline engineering, bridges play a vital role in post-earthquake rescue and disaster relief efforts. The rapid repair of earthquake-damaged piers is essential to ensure the uninterrupted functionality of lifeline systems. This paper presents a novel method for the rapid repair of earthquake-damaged pier columns using steel sleeves, based on a multi-level fortification approach, integrating numerical simulation, structural design, and experimental research. In alignment with the multi-level fortification requirements, the structural form of the outer steel sleeves was designed, key influencing factors were analyzed, and a design scheme for the outer steel sleeve was proposed. Furthermore, a quasi-static test was conducted to evaluate the seismic performance of the pier columns before and after repair. The results indicate that the maximum horizontal load the pier can withstand after repair is approximately 40% higher than that before the damage. When the pier’s bearing capacity reaches its maximum value, the horizontal displacement increases from 29.15 mm to 95.65 mm, indicating a significant improvement in the seismic performance of the repaired pier. Failure initiates with the buckling of the brace, followed by the buckling of the steel sleeves, demonstrating a multi-stage failure mode. This mode satisfies the requirements of multi-level fortification, with enhanced ductility achieved while maintaining the pier column’s bearing capacity, thereby enhancing the protection of the foundation. Full article

In this paper, a novel technique for connecting residential shear walls to floor slabs is investigated. Shear wall structures with two different connection methods were established and numerically analyzed using ABAQUS (2024) finite element software. The two structures were connected by sleeve grouted connections (hereinafter referred to as the original structure) and profile + bolted connections (hereinafter referred to as the new structure). Numerical analyses yielded a positive maximum load for the new structure 1.41 times that of the original structure and a negative maximum load 1.12 times that of the original structure. The ratio of the ultimate tensile strength (load value corresponding to the peak point) to the yield strength (load value corresponding to the yield point) of the two structures (strength-to-yield ratio) was in the range of 1.15–1.27. The original structure was 2.62 times more ductile in the negative direction and 2.24 times more ductile in the positive direction than the new structure. The stiffness degradation of the new structure was greater in the later stages of loading, and that of the original structure was greater in the early stages of loading. The original structure had 1.08 times the energy-consuming capacity of the new structure. The cost of labor and materials for the original structure was approximately 1.50 times the cost of the new structure. The results of the data analysis showed that, compared to the original structure, the new structure had comparable performance in terms of strength-to-flexure ratio, ductility, stiffness degradation, and energy dissipation capacity. However, the new structure was more advantageous in terms of load-bearing capacity and required lower construction costs than the original structure. Therefore, the connection nodes designed in this paper are of great significance for engineering practice. Full article

Based on the insufficient data on bonding performance and effective anchorage length of sleeve grouting in assembled structure. Combining the existing studies, the sleeve grouting joint test for the static unidirectional tensile test was designed, and the influencing factors are reinforcement diameter and reinforcement anchorage length. Then, the failure mode, load-displacement relationship, energy consumption capacity and bearing capacity of the grouting sleeve connection are analysed, and the stress mechanism of the specimen in the one-way tensile state is expounded. This paper considers the actual damage state of the joint, according to the failure of the reinforcement outside the joint and the sleeve; referring to the reinforcement-concrete bond strength research theory, the effective anchorage length formula is proposed. When the steel bar is pulled out, the bond strength and bearing capacity mainly depend on the effective anchorage length. However, when the specimen breaks the steel bar outside the joint, it depends on the material performance of the steel bar itself. The research results of this paper can lay a theoretical foundation for the application of sleeve grouting joints. Full article

This paper introduces a modular, assembled steel beam-column flange connection joint that efficiently connects prefabricated beams and columns using high-strength bolts. It enables the rapid repair of damaged joints after earthquakes by replacing flange connectors and high-strength bolt groups. Four joint specimens with varying thicknesses and lengths of the inner flange sleeve, scaled at a 1:2 ratio, were fabricated to evaluate performance. These specimens were subjected to low circumferential reciprocal loads to investigate damage modes, hysteresis curves, skeleton curves, ductility performance, energy dissipation capacity, and seismic performance, including stiffness degradation. The test and analysis results reveal that the primary failure mode is characterized by bulging of the flange jacket cover, with damage concentrated in the plastic hinge zone at the beam end. The flange connection joint exhibits excellent load-bearing, rotational, and energy dissipation capacities. The ‘secondary strengthening’ feature significantly enhances joint load-bearing capacity, ductility performance, and energy dissipation, increasing overall safety redundancy. Increasing the thickness and length of the flange connector substantially improves seismic performance and enlarges the plastic development area. Full article

The reliable anchorage of carbon fiber-reinforced polymer (CFRP) tendons is a critical issue influencing the stable bearing capacity of bridge cables. This study introduces a novel CFRP single-strand extrusion anchoring structure, where the strand is compressed at its end. By integrating this with internal cone filler wrapping, we create a CFRP multi-strand cable composite anchoring system. This innovative design not only minimizes the overall dimensions of the anchoring system but also significantly improves its anchoring efficiency coefficient. An axisymmetric model was developed using ANSYS finite element software. The radial stress distribution and anchorage efficiency coefficient in the anchorage zone of Φ7 CFRP bar and Φ13.6 extrusion die were analyzed with varying parameters, such as chamfering, outer diameter, and length of the extrusion sleeve, and were validated through static load anchorage tests. The results indicate that the highest anchoring efficiency is achieved when four extrusion sleeves with a chamfer angle of 5°, an outer diameter of Φ14.4, and a length of 15 mm are connected in series, reaching a coefficient of 61.04%. Furthermore, this study proposes an anchorage structure where multiple extrusion sleeves are connected in series and sequentially compressed to overcome the limitations of increasing anchorage length for enhancing the anchorage coefficient. The test results demonstrate that with equal total anchorage length, connecting four 15 mm extrusion sleeves in series enhances the anchorage efficiency coefficient by 24.98% compared to a single 60 mm extrusion sleeve structure. Full article

Test methods that use pushing forces to evaluate the maximal load capacities of carts in design standards require a flat, smooth and horizontal steel plate and thus do not take into account the real conditions of work. Resistive forces of a single wheel of a cart in a uniform rectilinear motion were measured using a unique test bench with five loads. Forty-four wheels were tested (varying diameters, treads and bearings) with one steel plate and four resilient floor coverings. Based on a linear mixed model, all the following results were significant (p < 0.05). Resistive forces were increased linearly with the load and depended on the characteristics of both the wheel and floor. These forces decreased as the diameter increased. They were important for wheels with sleeve bearings but decreased for cone ball bearings and precision ball bearings. Resistive forces depended on the material of the tread and were higher for solid rubber treads. In contrast, the hardness of the tread had little effect. Resistive forces strongly depended on the hardness of the base foam of resilient floor coverings: the softer the base foam, the higher the resistive forces. Test methods in design standards should be reviewed, using corrective forces based on these present results, to prevent musculoskeletal disorders. Full article