Prestressed concrete continuous box girder bridges have been widely adopted in transportation engineering due to their superior crack resistance ($Kf\geq$ 1.15) and stiffness stability ($\eta \leq$ 0.85). To address the mechanical uncertainties introduced by non-orthogonal diaphragm arrangements, by taking a 3 × 35 m box girder bridge constructed using a staged simply-supported-to-continuous method as the object, detailed beam grillage models with both orthogonal and stepped diaphragms were developed using Midas Civil 2023. Four loading scenarios were defined based on the JTG 3362-2018 standard, and static load tests employing four tri-axle heavy trucks were conducted to validate the model reliability. A total of 36 strain gauges (sampling frequency: 10 Hz) and 12 laser deflectometers (accuracy: ±0.01 mm) were installed on the top and bottom slabs of the box girder, with loading efficiency controlled within 0.91–1.03. Comparative analyses of strain fields ($\varepsilon$), deflections ($\delta$), and shear lag effects were performed for both diaphragm configurations. The results demonstrated that, under maximum positive bending moment conditions, the longitudinal strain differential rate across the top slab for the stepped diaphragm configuration remained within 3.7%. The deviation in deflection at the support region under negative bending moments was $\Delta \delta$ = 1.2 mm, meeting the specified code limits (L/600 = 58.3 mm). The loading efficiency test (0.91–1.03) confirmed the equivalent load-bearing performance of the stepped diaphragm configuration, with the cracking safety factor ($Kf$ = 1.18-1.22) found to be consistent with that of the orthogonal diaphragm model. A diaphragm inclination–stiffness matching criterion was proposed in this study, offering a theoretical reference for the design of the girder bridges constructed using a staged simply-supported-to-continuous method.
Muck pile characteristics play a pivotal role in optimizing mining operations, particularly in understanding the post-blast behavior of throw, drop, and lateral spread, which directly impacts the selection and performance of loaders. The parameters of blast design are crucial in determining muck pile formation, influencing both loader efficiency and overall operational productivity. This study explores the effects of various blast design parameters on key muck pile attributes through a series of controlled blast experiments. Principal component analysis (PCA) was employed to identify the blast design factors most influential on muck pile characteristics, enabling the formulation of precise blast designs. The experiments were conducted across four phases at the OCI RGIII mines of Singareni Collieries Company Limited (SCCL), using advanced blast planning software to ensure accurate parameter implementation based on PCA results. Muck pile characteristics were assessed with the assistance of sophisticated artificial intelligence (AI) tools, providing valuable insights into blast optimization. The results revealed that blast designs incorporating a 1.35 spacing-to-burden (S/B) ratio, 0.9(B) stemming, 1-meter decking, and a V firing initiation pattern significantly enhanced muck pile performance. Specifically, these configurations reduced drop height by 3 meters, decreased throw distance by 5.9 meters, and increased lateral spread by 19.3 meters. These optimized muck pile attributes facilitated smoother loader operation, ultimately improving loading efficiency and the overall productivity of mining processes.
This study investigates the application of the horizontal stratified mining method to the extraction of steeply inclined unstable coal seams at the Puxi Mine. The stress environment in the mining area, the relationship between the supports and surrounding rock, the control of the rock layers in the caving zone, and the mechanical analysis of the roof collapse following the extraction of the steeply inclined coal seam were examined. The stress conditions in the mining area under the horizontal stratified mining method were explored, and a numerical analysis model was established using FLAC3D software, based on the rock mechanics parameters of the Puxi Mine’s rock layers and strata. The results indicate that, in the stress environment of the horizontal stratified mining method, the mining area is subject to not only the self-weight stress from the surrounding strata, large horizontal ground stresses, and gas pressures, but also concentrated stresses in both the dip and strike directions. When using this mining method, the stability of the two sides of the tunnel is generally good due to the surrounding rock being of a relatively stable nature. However, the roof collapse in the upper layers during the extraction of the lower layers is one of the factors affecting the safety of the support structures in the lower layers, necessitating enhanced support management. Deformation is expected in the mining face of the lower layers during extraction, and measures must be taken to prevent any instances of roof spalling. Therefore, the horizontal stratified mining method is considered feasible for the extraction of steeply inclined unstable coal seams at the Puxi Mine.
Earthquakes, characterized by unpredictable seismic events, release substantial lateral energy, which propagates through structures, often causing significant damage before the motion subsides. In the absence of specific seismic design guidelines in the British Standards (BS), the introduction of the Eurocode has provided a more comprehensive framework for seismic resistance. Although Sarawak, Malaysia, is situated in a low seismic hazard zone, the effects of seismic forces on structures that are not explicitly designed for seismic resistance remain poorly understood and under-researched. This study employs SAP2000 software to conduct nonlinear pushover analysis (POA) and nonlinear time history analysis (NTHA) on medium-rise reinforced concrete (RC) and steel frame buildings subjected to lateral forces and dynamic ground motions scaled to the local seismic intensity, in accordance with Eurocode 8 (EC 8). The seismic responses of different structural models, incorporating various bracing configurations, were compared to evaluate the relative performance of each system. The influence of material type and bracing configuration on structural behavior under seismic loading was examined. The results suggest that, among the configurations analyzed, the RC frame with central inverted V-bracing (Model 1) exhibits superior seismic performance in terms of lateral stiffness, displacement control, and energy dissipation, positioning it as the most optimal design solution for the study's conditions. This investigation highlights the critical role of structural design and bracing configuration in enhancing the seismic resilience of buildings, even in regions with relatively low seismic risk.
Corrosion-induced damage significantly impairs the seismic performance of steel frame columns, leading to an increased vulnerability during earthquake events. To address this issue, a restoring force model was developed to accurately describe the seismic behaviour of corroded steel columns. Low-cycle repeated loading tests were conducted on corroded steel frame columns to evaluate the effects of corrosion and earthquake-induced damage on their seismic performance. The results revealed distinct degradation patterns, which were systematically analyzed. A cyclic degradation index was proposed to quantify the impact of corrosion on critical parameters, including yield strength, hardening stiffness, unloading stiffness, and reloading stiffness. This index was incorporated into a damage model, which facilitated the formulation of a comprehensive restoring force model for corroded steel frame columns. The developed model was validated through case studies, demonstrating its effectiveness in predicting the seismic response of corroded columns. The findings underscore the importance of considering corrosion damage in the assessment and design of steel frame columns subjected to seismic loading, providing a more accurate and reliable approach for seismic performance evaluation.
This study investigates the performance of star-shaped auxetic structures as protective materials in aluminum containers, designed to safeguard sensitive or hazardous materials during road transport. Finite element analysis (FEA) was conducted to assess the impact resistance of the star-shaped auxetic structure under high-speed collisions, simulating potential events such as explosions or sudden impacts. The simulations were performed using Autodesk's event simulation algorithm. In the first analysis, the auxetic structure was subjected to loading conditions applied to the metallic casing, while in the second, the metallic casing was considered rigid, with the focus placed on the structural behavior of the auxetic material under extreme stress conditions. Both scenarios examined the response of the auxetic structure in the plastic deformation region. The results indicate that the maximum stress developed in both loading cases approached 80 MPa. Notably, in the second scenario involving the rigid casing, the maximum displacement of the auxetic structure increased threefold compared to the first study. Despite the extreme loading conditions, the auxetic structure maintained significant cohesion, ultimately failing in a controlled manner. The ability of the star-shaped auxetic structure to absorb substantial impact loads is attributed to the twisting deformation of the structure, which redirects the applied stress towards the center of the impact area. These findings highlight the potential of star-shaped auxetic materials in providing enhanced protection for sensitive materials during transport, demonstrating their ability to withstand severe dynamic loading and to effectively dissipate energy upon impact.
The free vibration characteristics of functionally graded porous (FGP) beams were investigated through the application of hyperbolic shear deformation theory (HSDT). The material properties were described using a modified rule of mixtures, incorporating the porosity volume fraction to account for various porosity distribution types, enabling the continuous variation of properties across the beam thickness. The kinematic relations for FGP beams were formulated within the framework of HSDT, and the governing equations of motion were derived using Hamilton’s principle. Analytical solutions for free vibration under simply supported boundary conditions were obtained using Navier’s method. Validation was conducted through comparisons with existing data, demonstrating the accuracy and reliability of the proposed approach. The effects of porosity distribution patterns, power-law indices, span-to-depth ratios, and vibrational mode numbers on the natural frequency values of FGP beams were comprehensively examined. The findings provide critical insights into the influence of porosity and geometric parameters on the dynamic behavior of functionally graded (FG) beams, offering a robust theoretical foundation for their design and optimization in advanced engineering applications.
The stability of rock masses in large-scale hydropower projects and high-slope excavation engineering is significantly influenced by the unloading of confining pressure. This study investigates the triaxial creep behaviour of limestone under varying conditions of confining pressure unloading through systematic experimental research. Using a ZYSS2000C triaxial shear rheometer, limestone samples from the Qinling region were subjected to a series of triaxial creep tests with controlled unloading conditions. Experimental setups included varying single-step unloading magnitudes of confining pressure (2 MPa, 4 MPa, and 6 MPa) under constant axial stress. The results demonstrated that the magnitude of confining pressure unloading had a pronounced impact on creep behaviour. Larger unloading magnitudes led to shorter total creep durations and reduced cumulative deformation, highlighting the pivotal role of unloading intensity in governing creep characteristics. During the unloading creep process, the deviatoric stress of the rock decreased, and the deformation predominantly manifested as radial dilation. These findings provide new insights into the rock deformation mechanisms induced by confining pressure unloading and offer valuable theoretical and practical guidance for slope excavation and stability management.
Achieving efficient fragmentation and minimizing ground vibration in blasting operations necessitates a precise understanding of bench geology, structural dimensions, and the compressive strength of the rock. This study presents a novel blast design approach that integrates compressive strength-driven adjustments to decking lengths and firing patterns, aiming to balance effective fragmentation with safe peak particle velocity (PPV) levels. A series of 36 trial blasts was conducted to assess the impact of decking and firing configurations tailored to specific rock strengths, supported by advanced software simulations and field laboratory testing. Results indicated that a combination of 3.5 m decking length with a V-pattern firing arrangement yielded optimal outcomes for rocks exhibiting compressive strengths between 40 and 50 MPa. This configuration achieved a mean fragmentation size (MFS) of 0.21 m and a PPV of 1.11 mm/s, demonstrating its suitability for controlled and efficient blasting. The findings underscore the critical role of rock strength in guiding blast design and provide mining engineers with practical insights for improving blast efficiency and safety. This study contributes to the development of adaptable blasting models that account for geological variability, paving the way for more precise control over fragmentation and ground vibration in complex mining environments.
The 6.0 moment magnitude scale (Mw) earthquake that struck Ranau, Sabah, on June 5, 2015, resulted in seismic intensities of VI to VII, significantly increasing the seismic vulnerability of buildings in the region. This study presents an analysis of the site-specific seismic ground response and liquefaction potential for the Ranau District, East Malaysia. Ground response spectra were generated for 15 borehole sites, applying a 5% damping factor at ground level using both global and local input ground motions. Seven global and five local seismic records were processed using a one-dimensional equivalent linear approach via DEEPSOIL software. The LiqIT software, based on the Boulanger and Idriss method, was employed for the liquefaction analysis. Ground amplification in Ranau was found to range between 1.281 and 5.132, with peak ground acceleration (PGA) reaching an average maximum of 0.314 g at the surface. Soil periods across the region varied from 0.05s to 1s, consistent with the specifications outlined in the Malaysian National Annex for Sabah (MS EN 1998-1:2015). The results confirmed that the Ranau District is not prone to liquefaction, offering valuable insights for the structural design of future constructions in the area.
This study outlines the essential thermal and mechanical properties of wood, steel, and gypsum board, focusing on their application in timber-steel and timber-timber connections, as well as in protected and unprotected connections involving one or more materials. These materials are widely used in structural components, serving various functions, from load-bearing to protective roles. A comprehensive summary of these materials was provided, emphasising the critical importance of understanding their properties for use in numerical simulations and other analytical methods commonly employed in structural design research. The properties of these materials significantly influence the behaviour of connections under various conditions, particularly in fire scenarios or other high-temperature environments. As such, knowledge of these properties is crucial for ensuring the accuracy of design calculations and simulations. Furthermore, selecting appropriate material properties from verified standards and documents contributes to the reliability of numerical analyses. This study aims to consolidate and present these verified properties to facilitate their application in both experimental and computational studies of structural connections.
This study employs a combination of geological investigation, numerical simulation, and theoretical analysis to evaluate the applicability of the load-unload response ratio (LURR) theory in urban tunnels. The results indicate that using the sudden increase in the LURR at critical points or the equivalent plastic strain penetration between the tunnel and the ground surface as failure criteria for subway tunnels is feasible. Under critical instability loads, the equivalent plastic strain zones in the surrounding rock penetrate to the surface during the construction phase, leading to severe deformation of the tunnel chamber group and loss of load-bearing capacity in the surrounding rock. During the operation phase, the tunnel lining plays a primary load-bearing role. Under instability loads, a butterfly-shaped failure zone appears in the surrounding rock. These findings can be utilized for the quantitative evaluation of the overall safety margin of urban subway tunnels.
Recent advancements have seen the integration of nanocomposites, composed of clay minerals and polymers, into cementitious materials to enhance their mechanical properties. This investigation focuses on the dynamics of clay-based cementitious nanofluids along a vertical plate, adopting a Jeffrey fluid model to encompass various phenomena. The effects of a first-order chemical reaction and heat generation/absorption are considered, alongside slip velocity and Newtonian heating conditions. The governing equations, represented as partially coupled partial differential equations, have been extended using a constant proportional Caputo (CPC) fractional derivative. Exact solutions were derived employing the Laplace transform technique. A detailed graphical analysis was conducted to elucidate the influence of pertinent flow parameters on the velocity, temperature, and concentration profiles. It was observed that the incorporation of clay nanoparticles results in a reduction of the fluid's heat transfer rate by 10.17%, and a decrease in the mass transfer rate by 1.31% at a nanoparticle volume fraction of 0.04. These findings underscore the nuanced role of nanoparticle concentration in modifying fluid dynamics under the studied conditions, providing a validated and precise understanding of nanofluid behavior in construction-related applications. This research not only supports the potential of nanotechnology in improving cementitious materials but also contributes to the broader field of fluid mechanics by integrating complex heating and slip conditions into the study of nanoparticle-enhanced fluids.
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