International Journal of Civil Engineering最新文献

This study investigates the mechanical characterization of Fabric Reinforced Cementitious Matrix (FRCM), emphasizing the tensile and bond performance of system incorporating Glass Fabric-Reinforced polymer (GFRP) mesh embedded in an inorganic binder. The primary focus is on the variation in the fabric reinforcement ratio and bond width for the shear bond test. To determine composite matrix tensile properties, rectangular cross-section specimens underwent direct tensile testing. The maximum tensile strength for composite sections with thicknesses of 8, 10, and 12 mm ranges from 1.03 to 5.91 MPa, varying with configurations of one to four layers, respectively. Test results revealed a substantial increase in tensile strength with an increase in fabric reinforcement ratio, with maximum tensile strength ranging from 6 to 63.77% compared to Aveston Cooper Kelly (ACK) theory and Simplified Tri-Linear model. Single-lap shear bond test conducted on concrete blocks to evaluate the bond strength between the GFRCM and the concrete substrate. The maximum bond shear strength for the specimen reinforced with one to four layers of GFRCM ranges from 4.86 to 14.65 MPa. The test results highlighted a strong bond and an increase in shear bond strength as the number of layers increases, with maximum shear strength ranging from 5 to 18% compared to the Interfacial Constitutive model. The bending test results showed a maximum strength increase of 8.49–18.73% compared to the single-layer reinforced specimen. The study concludes that glass FRCM significantly enhances the tensile, shear bond, and bending performance of concrete structural components in practical applications.

The current study investigated the boundary effects induced by an Equivalent Shear Beam (ESB) container in a dynamic centrifuge test of a silica sand deposit. A fully nonlinear two-dimensional (2D) numerical model is established for the ESB container with soil by adopting nonlinear sand and hyperplastic rubber materials. A nonlinear frictional connection is adopted between the ESB and the soil. This study also proposes a numerical simulation procedure for ESB containers as boundaries for seismic analysis. A relationship between the fundamental frequency of the ESB container and rubber material properties is also proposed and provides a guide for the simulation of centrifuge tests with ESB containers. The established numerical model is validated via a dynamic centrifuge test. Investigation revealed that the boundary effects are minimal and are less than 20% at the base to the middle height of the soil deposits. The effects are significant on the surface and can reach 80% near the boundary. The effects remain less than 20% from the middle up to 0.3B (B: total width of soil deposit) toward the boundary. This position is recommended as the optimal location for sensor placement in centrifuge tests. It is also observed that the boundary effects are significant around the fundamental period of the soil deposit. The findings from the study provide a guideline for the numerical modeling of ESB containers and for determining the optimal location for sensor placement in centrifuge tests to minimize boundary effects.

Using optimization and regression methods, this research developed intermodal transportation routes in the event of terminal disruptions. The proposed mixed integer linear programming model explicitly takes into account the discrete unit flows of carriers within the intermodal rail network including time-varying demand and capacity. The objective of this study is to optimize the rerouting decisions for carrier services in rail-road intermodal transportation networks. Numerical experiments are conducted with several problems of varying sizes and characteristics. CPLEX solves the optimization model and reports the most effective results. A case study of multimodal transportation networks in Iran demonstrated the effectiveness of the proposed strategies. The results of this study demonstrate that it is important to identify the vulnerable rail-roadway links in an intermodal freight transportation network in order to minimize delays in meeting freight demand and, thus, increase the reliability of the multimodal freight network in Iran. By using road strategy to reduce costs, the transportation costs will decrease by 0.85% and 4.8%, respectively, under 25% and 100% disruption conditions; therefore, road transportation is a more economical strategy for reducing costs in conditions of rail terminal disruption.

In order to solve the problem of surrounding rock support difficulties encountered during TBM excavation in weak strata in coal mines, a steel segment support structure for TBM-excavated tunnels in coal mines was proposed. Full-scale model tests of the steel segment support structure were conducted under different lateral stress coefficients. The deformation and failure modes, bearing capacity, and strain distribution characteristics of the proposed roadway support structure were studied, and the factors influencing the bearing capacity of the support structure were determined, revealing the mechanism of the instability and failure of the support structure. Subsequently, numerical tests of the support structure were conducted to obtain parameters such as the axial force and bending moment, which were difficult to monitor in the full-scale model tests. The results showed that the support structure first experienced local instability at the joints and mid-span, leading to overall instability of the structure. The ultimate bearing capacities of the support structure were 3,972.2 kN and 2,763.2 kN for lateral stress coefficients of λ = 1.0 and 1.5, respectively. The ultimate bearing capacity decreases exponentially with increasing lateral stress coefficient, highlighting the importance of considering tectonic stress in design. Design parameters analysis reveals that rib plate thickness significantly influences bearing capacity, followed by rib plate width, while ring plate thickness has a minimal impact.

This study presents a novel self-centering two-yield buckling-restrained brace (SC-TYB) incorporating a dual-core configuration with distinct yield strengths, utilizing low-yield point and high-strength steel. This system is introduced to mitigate a critical limitation inherent in buckling-restrained braces (BRB), which rely on hysteretic behavior for seismic energy dissipation and experience a significant reduction in post-yielding stiffness. The feasibility and performance of the proposed brace in braced frames are assessed through a simplified core-spring finite element model. Through nonlinear analysis, this study evaluates the behavior of two-story SC-TYB frames with multiple prevalent arrangements. Pushover and time history analysis utilizing near-field and far-field earthquake records were performed to investigate the ductility, over strength, response modification factors, and the seismic response of braced frames, focusing on maximum inter-story drifts and residual drifts. The results demonstrate that the proposed BRB exhibits a multistage yield pattern and maintains significant post-yield stiffness, effectively counteracting P-delta effects. Also, the response modification factor of frames with the introduced SC-TYB was obtained on average 40% higher than that of BRB frames. Meanwhile, in comparison, the analysis reveals a 10% and 35% average decrease in inter-story and residual drifts, respectively, for SC-TYB frames. Finally, the diagonal arrangement of the proposed system exhibits the minimum inter-story and residual drifts among the evaluated models.

This article aims to study the changes in strength and water holding capacity of low liquid limit clay under different compaction degrees and dry-wet cycles. Based on the variation law of embankment fill compaction in service, soil samples of typical low liquid limit clay in southern Anhui, China, were reshaped with 85%, 90%, and 95% compaction degrees, followed by 0–5 dry wet cycle tests. Then, direct shear tests and soil water characteristic curve (SWCC) tests by filter paper method were conducted on cycled samples, and the suction stress of these samples was calculated backwards. A new SWCC model considering compaction and dry-wet cycles was established. The results show that the shear strength decreases with the increasing dry-wet cycles, and the first cycle has the maximal impact on the shear strength and cohesion of the low liquid limit clay. After 5 dry-wet cycles, the cohesive force and internal friction angle of the 95% compacted soil sample are 2.61 times and 1.24 times that of the 85% compacted soil sample, respectively. When the compaction degree increases, the intake value, suction stress range, and water holding capacity of the soil show an increasing trend. The suction stress of soil samples elevates with the increase of dry-wet cycles in the low effective saturation stage and drops with the rising dry-wet cycles in the high effective saturation stage. The turning point of saturation is between 0.1 and 0.3.

The aim of this study is to increase the load–displacement capacities of beams with web openings exposed to cyclic loading, to reduce the distortion in rigidity and to design high-strength beams with web holes designed according to BS 5950 specifications. The tests were carried out on five 2400 mm long, non-composite IPE240 cross-section beams. The ratio of the beam height to the diameter of the web opening is determined according to the BS 5950 specifications: for the beam with the ratio of 1.25 (lower limit) the diameter of the opening is 192 mm, for the beam with the ratio of 1.75 (upper limit) the diameter of the opening is 137 mm, for the beam with the ratio of 1.5 the diameter of the opening is 160 mm, and for the beam with the ratio of 1.618 the diameter of the opening is 148 mm. The beam with a ratio of body height to opening diameter of 1.618 (Golden Ratio) was compared with the perfect model and other beams with different opening diameters. According to the BS 5950 specification, when the ratio of beam height to circle diameter reaches 1.618, the opening diameter in the beam web exceeds the upper limit. However, in the beams examined in this study that exceed the upper limit of the specification, it was found that the beams carried 11.62% more moment and 11.63% more load, and their energy absorption capacity increased by 22.19%. In addition, the decrease in the moment bearing capacity, load bearing capacity and energy absorption capacity of the beam optimized with the golden ratio was determined as the optimization that shows the closest mechanical behavior to the perfect sample with a decrease of 20.65–24.1% and 4.12%, respectively. In this study, finite element analyses and experimental data were used to validate the experimental results of the designs and to examine the deformation modes and nonlinear behavior of the beams with web openings. As a result of the research, it has been determined that the mechanical properties of the beam subjected to cyclic loads and designed according to the golden ratio are closer to the perfect model.

This study investigates local scour, a significant cause of bridge damage, by examining the effect of vegetation as a natural method to mitigate erosion around bridge abutments. Laboratory experiments were conducted on semi-circular abutments under conditions with and without vegetation. A total of 65 velocity profiles were obtained using acoustic doppler velocimetry (ADV), enabling the calculation of 3D velocity, turbulence intensity, and Reynolds stresses. The experiments revealed that the presence of vegetation decreased the time to reach scour equilibrium by up to 40%, and reduced scour depth by up to 33%. Vegetation significantly reduced shear stresses near the bed and around the abutment, with turbulence intensity values becoming more uniform in the streamwise and transverse directions and larger than those in the vertical direction. Flow events at specific angles showed distinct patterns. Without vegetation, at a 90-degree angle, ejection events dominated near the bed while sweep events were prevalent near the water surface. At a 130-degree angle, sweep events dominated near the bed, and ejection events were dominant from the middle depth upwards. With vegetation, at a 90-degree angle, all four events (sweep, ejection, inward interaction, and outward interaction) were close to each other in the initial one-third near the bed, with significant decreases in sweep and ejection events. At a 130-degree angle, vegetation showed no significant difference in dominant events compared to the non-vegetation case. These findings highlight the effectiveness of vegetation in reducing scour around bridge abutments and provide valuable insights into the flow-vegetation interactions that influence scour processes.

The pressurised bentonite slurry efficiently stabilised the tunnel face, but slurry infiltration may reduce its effectiveness. In this work, the effect of slurry infiltration on tunnel face stability during slurry-shield tunnelling in saturated cohesionless soil is investigated, and the results reveal that due to slurry infiltration, an additional margin for support pressure is needed. The infiltration distance has a significant influence on the effective support at the tunnel face. For slurries with a low viscosity (apparent viscosity = 4 mPa·s), only when the infiltration distance is small (< 0.5 m) is the effective support ratio high (> 80%). Furthermore, a larger infiltration distance or a larger value of tunnel diameter to cover depth ratio (C/D) requires a higher support pressure. Generally, the hydraulic gradient at the face in an unconfined aquifer is greater than that in a semi-confined aquifer. For semi-confined aquifer, a smaller height or a larger leakage length leads to a greater hydraulic gradient. Finally, for shield tunnelling in an aquifer, when the gradient at the tunnel face is less than 1, a viscous slurry is recommended to replace the pure water to support the tunnel face.

This study investigates the mechanical behavior of gravelly soil under various confining pressures using large-size triaxial cyclic tests and a novel constitutive model. Key properties analyzed include stress-dependent dilatation, nonlinear strength, cumulative plastic strain, cyclic hysteresis, hardening, and particle breakage. Experimental results show that confining pressure significantly affects volume deformation, strength, and failure modes. Specifically, volume deformation shifts from dilatation to contraction with increasing pressure, and failure modes transition from drum-shaped to compressive shear. The developed model integrates stress-dilatancy equations, plastic flow directions, and plastic moduli within the critical state soil mechanics framework, effectively capturing cyclic loading and unloading behaviors. A particle breakage index and a differential equation for void ratio evolution are included to reflect relative density changes. The material constants of this constitutive model are derived from large-size triaxial cyclic tests. The model's material constants are derived from large-size triaxial cyclic tests. Comparison with experimental data confirms the model's accuracy and potential applications in stress path analysis and complex engineering projects, demonstrating its adaptability to varying mechanical stress conditions.