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.
In this study, the FLAC3D finite difference numerical software was employed to simulate a geotechnical engineering project, establishing scenarios with concrete and steel pipe piles for support simulation. The analysis focused on the reinforcement effects provided by different types of piles on the geotechnical project. It was found that the reinforcement effects on the soil varied significantly between the pile types. Under the support condition of concrete piles, the maximum soil settlement observed was 4.12 mm, with a differential settlement of 3.19 mm. For steel pipe piles, the maximum soil settlement was reduced to 2.38 mm, with a differential settlement of 2.19 mm, indicating a superior support effect compared to that of concrete piles. Stress concentration phenomena were observed in the piles, becoming more pronounced when pile-soil friction was considered. The substitution of concrete piles with steel pipe piles led to an intensified stress concentration phenomenon in the soil surrounding the piles. The soil undergoing support from concrete piles exhibited the largest plastic deformation, whereas soil supported by steel pipe piles showed less plastic deformation. Consequently, it is concluded that steel pipe piles provide a superior support effect over concrete piles in terms of geotechnical engineering reinforcement.
Seismic performance is a critical consideration in the design and assessment of reinforced concrete bridges. Ensuring the structural integrity and safety of bridges under seismic loadings is essential to protect public safety and maintain the longevity of these vital infrastructure components. The objective of this research study was to evaluate the seismic performance of a multi-span reinforced concrete bridge located in Pan Borneo Highway Sarawak. The non-linear static pushover analysis provided valuable insights into the bridge's load resistance. It determined that the bridge could withstand a base shear force of up to 30,130.899 kN before collapsing, indicating its high structural capacity. The capacity curve analysis further demonstrated the ability of bridge to endure spectral accelerations of up to 4.44 g (43.512 m/s$^2$), indicating its robustness against high-intensity ground motions. In addition, the non-linear static time history analysis considered three ground motions and their effects on the bridge's structural performance. The study highlighted the bridge's sensitivity to different external forces, with varying responses observed under different ground motions. Notably, the recorded joint acceleration and displacement values were found to be within acceptable limits, ensuring immediate occupancy and life safety for bridge users. The research study successfully evaluated the seismic performance of a reinforced concrete bridge in Pan Borneo Sarawak using non-linear time history and pushover analyses. The results demonstrated the bridge's satisfactory capacity to withstand seismic loadings. The utilization of CSIBridge software provided valuable insights into the bridge's structural integrity and behavior under seismic conditions. These findings contribute to the advancement of bridge engineering practices.
Traditional analyses of tunnel reliability, which employ deformation values, such as surface settlement, crown settlement, and arch shoulder settlement, as instability indicators, fail to accurately depict the failure state of tunnel lining structures. In addressing tunnel instability induced by the failure of lining structures, the limit strain theory is introduced, designating shear strain penetration failure of the lining structure as the criterion for tunnel instability. A novel method for studying tunnel reliability, integrating neural network response surface methodology and Monte Carlo simulation, is proposed. The feasibility of the limit strain theory in reliability analysis is validated through the calculation of instability probabilities for specific tunnel projects, offering a fresh perspective on tunnel reliability assessment. Sensitivity analysis of rock mass parameters reveals that an increase in the variability of these parameters elevates the probability of tunnel instability and the shear strain value at the arch waists. Among these parameters, the variability of the modulus of elasticity (E) exerts the most significant impact on the probability of tunnel instability.
Glued laminated timber (glulam), a composite material fabricated by bonding multiple wood layers, is engineered to support specific loads, offering reduced product variability and diminished sensitivity to inherent wood characteristics, such as knots. This technology facilitates a wide array of architectural designs, rendering it a popular choice for load-bearing elements across diverse construction projects, including residential structures, storage facilities, and pedestrian overpasses. Over time, exposure to various environmental conditions leads to the degradation of these structural components, necessitating periodic reinforcement to maintain their strength properties. Recent advancements have seen the adoption of fiber-reinforced polymer (FRP) for the reinforcement of columns and beams, a departure from traditional strengthening methods. This study focuses on the connection of column-beam joints using an array of steel fasteners, subsequently reinforced with FRP. Rotational tests were conducted on these fabricated connections, followed by a comprehensive analysis using the finite element method (FEM). Results indicate that connections reinforced with FRP exhibit a significant enhancement in load-carrying capacity, energy dissipation, and stiffness compared to their unreinforced counterparts. Specifically, the load-carrying capacity showed an increase of 25-39%, energy dissipation capacity augmented by 64-69%, and stiffness values rose by 2-7%. These findings underscore the efficacy of FRP reinforcement in improving the structural integrity and performance of glulam column-beam connections, offering valuable insights for the design and renovation of wood-based construction elements.
In rock masses, internal defects such as joints, faults, and fractures are pivotal in determining mechanical behavior and structural integrity. This investigation, employing the discrete element numerical simulation technology of GDEM, examines the mechanical attributes of single-fractured sandstone under standard triaxial compression. The study focuses on how fracture inclination angle and confining pressure affect crack propagation within the rock. It is observed that an increase in both fracture inclination angle and confining pressure correlates with a reduction in the tensile stress growth rate near the fracture, indicative of inhibited crack propagation. A notable transition in the failure mode of the sandstone samples is identified, shifting from tensile-shear to predominantly shear failure. This shift is more pronounced under varying confining pressures: Low confining pressure conditions show a prevalence of tensile-shear damage units in proximity to the fracture, while high confining pressure leads to a dominance of shear damage units. These findings contribute to a deeper understanding of fracture mechanics in rock materials and have significant implications for geological and engineering applications where rock stability is critical.
Building upon the foundations of classical fractional derivatives, the general fractional derivative emerges as a significant advancement in the development of constitutive models, especially for materials with complex properties. This derivative distinguishes itself through a kernel function of variable form, enabling it to encapsulate diverse characteristics of the creep process more effectively than its classical counterpart. This study introduces a general-variable order fractional creep constitutive model, ingeniously linking the order of the fractional derivative to Talbot gradation, which describes the aggregate gradation of cemented backfill materials, alongside dosage and confining pressure parameters. The model's innovative design synergizes the kernel function's diversity from the general fractional derivative with the phase adaptability inherent in the variable-order derivative. This integration permits a comprehensive description of each stage of the creep curve for cementitious filling materials in varying compositions, leveraging the Gamma function's properties within the positive real number domain. The model's rationality and validity are substantiated through a comparative analysis between experimental creep curves and theoretical predictions, affirming its relevance and accuracy in practical applications. This approach represents a notable contribution to the understanding of cemented backfill materials' behavior, offering a robust tool for engineering analysis and design.
This study examines innovative box-plate prefabricated steel structures, where stiffened steel plates serve as primary load-bearing walls and floors. In contrast to traditional stiffened steel plate walls, which typically exhibit significant hysteresis, pronounced out-of-plane deformation, and rapid stiffness degradation, these advanced systems demonstrate superior performance. A pivotal feature of these structures is the intensive use of welding to connect stiffened steel plates during assembly. This study introduces a novel composite stiffened steel plate wall, addressing concerns of traditional systems, and executes a comprehensive numerical simulation to assess the influence of welding on joint integrity and overall structural performance. It is observed that the height-to-thickness ratio of steel plate walls significantly influences load-bearing capacity, with a lower ratio yielding enhanced capacity. However, the stiffness ratio of ribs is found to have minimal impact. An increase in bolt quantity and density correlates with improved ultimate bearing capacity. Moreover, the adoption of staggered welding techniques bolsters shear strength, though the positioning of welds has negligible influence on this parameter. The number of welded joints moderately affects shear strength, while the size of staggered welding joints is identified as a crucial factor, with larger sizes leading to more pronounced reductions in shear strength. This study highlights the importance of construction details, particularly in welding practices, in the structural integrity and performance of box-plate prefabricated steel structures. The findings offer significant insights for optimizing design and construction methodologies to maximize the load-bearing capacities of these innovative systems.
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