Load Bearing Capacity Of Structures Research Articles

Data-driven prediction of high-temperature bond strength in corroded reinforced concrete

For accurately assessing the structural load bearing capacity of corroded reinforced concrete(CRC) structures after exposure to high temperatures, such as in sudden fire accidents, there is an urgent need for a unified model to predict the bond strength of CRC under high-temperature conditions. However, the degradation mechanism of bond strength in CRC under high-temperature conditions is highly complicated. Traditional empirical models cannot account for the multivariate correlations among factors such as high temperature, corrosion, and material properties. Based on a large amount of existing experimental data, ML methods can effectively establish a regression relationship between input and output features through data analysis. This paper utilized five ML algorithms, namely ANN, SVM, DT, RF, and XGB, to establish an interpretable prediction method for the high-temperature bond strength of CRC. The model was trained and tested using 612 sets of experimental data on high-temperature CRC. The results show that the predictions of the ML model are in good agreement with the experimental results. Moreover, the calculation outcomes of the ML model were compared with those of three theoretical calculation formulas, and the ML model demonstrated clear advantages. Furthermore, to address the black-box issue inherent in ML algorithms, the SHAP method was employed to enhance the interpretability of the bond strength prediction process for high-temperature CRC. This model will provide a theoretical basis for accurately assessing the extent of damage to CRC buildings after exposure to high temperatures.

ADDITIVE TECHNOLOGIES IN CONSTRUCTION: TECHNICAL, ECONOMIC AND MANAGEMENT ANALYSIS

The study is devoted to a comprehensive analysis of the introduction of additive technologies into modern construction production, revealing the technical, economic, and managerial aspects of concrete 3D-printing of architectural structures. The work systematically analyzes the evolution of additive manufacturing technologies and identifies the main structural types of 3D-printers (an additive machine for layer-by-layer construction of objects), including portal, robotic, mobile, and hybrid systems. A detailed study of the technological parameters of concrete 3D-printing with concrete mixtures is presented, in particular, optimal printing speed modes, layer parameters, criteria for shaping and quality of building structures. A comparative analysis of the technological capabilities of leading world equipment manufacturers, such as ICON, COBOD International, Apis Cor, and WinSun, is conducted. The economic analysis demonstrates significant advantages of additive technologies: reduction of construction time by 2-6 times, reduction of construction cost by 20-35%, and increase in the load-bearing capacity of structures. The study comprehensively explores the structure of capital and operational expenses associated with technology implementation. Special emphasis is placed on the management aspects of introducing additive technologies, highlighting the critical need for an interdisciplinary approach and knowledge integration across architecture, engineering, management, and computer modeling. The study determines the prospects for the development of concrete 3D-printing technology in the construction industry and outlines the main directions of further scientific research and practical implementation of innovative solutions. This study was developed between the Department of "Integrated Technologies of Mechanical Engineering" named after M. Semko of NTU "KhPI" and "Geopolimer" LTD to implement innovative technologies in the construction industry.

Experimental study on bearing capacity of steel-pipe PBL shear connectors

In composite open-web sandwich plate structures, when the span is large, the restraining effect of the bottom chords on the top chords makes the stress state of the material interfaces tend to be complicated, which restricts the structural load-bearing capacity. Therefore, To improve the overall stress state of such structures and increase their load-bearing capacity, this study introduces an innovative design for Steel-pipe PBL shear connectors(Perfobond rib shear connectors). In this design, steel pipes are welded to the openings of conventional PBL shear connectors. By utilizing the circular cross-section of the steel pipe to resist the complex stresses at the material interfaces, the stiffness of the shear connectors and the load-bearing capacity of the structure are improved at the same time. This study evaluates the shear performance of the new PBL shear connectors by testing nine specimens with varying parameters: steel pipe diameter, length, wall thickness, perforated rebar diameter, and concrete strength. The results indicate that steel pipes modify the failure mode and bearing mechanism of conventional PBL shear connectors, significantly enhancing shear stiffness and ultimate bearing capacity. Among all parameters, the steel pipe diameter has the most substantial impact on the bearing capacity of Steel-pipe PBL shear connectors. Based on the experimental data, this article presents a calculation formula for assessing the ultimate bearing capacity of Steel-pipe PBL shear connectors.

Optimized evaluation of ground motion intensity measures for the prefabricated cantilevered roadbed structure in mountainous areas

The prefabricated cantilevered roadbed structure (PCRS) is a novel design that addresses the significant excavation and embankment volume associated with traditional mountainous roadbeds. The seismic performance of it has not yet been fully investigated. Seismic fragility analysis is one of the main methods for assessing the damage pattern of a structure, and the ground motion intensity measure (IM) is a key parameter affecting the damage assessment results. To this end, a finite element model is first conducted based on structural load-bearing capacity verification experiments, relying on a prefabricated cantilevered roadbed structure in a mountainous region. Then, the nonlinear time-history analysis of the structure was carried out, and 20 common IMs were selected and compared from the perspectives of practicality, efficiency, proficiency, and sufficiency. Finally, the seismic fragility analysis of the structure is conducted based on the optimal IM. The analysis results indicate that the peak ground acceleration of response spectrum (PSA) is the optimal IM for such structures. Quadratic fitting exhibits higher accuracy compared to linear fitting. Among all components, fixed-end foundations are identified as the most vulnerable. Anchored reinforcement remains elastic throughout the seismic response calculations and suffers little damage.

Vulnerability Assessment for Naval Ships against Air-Explosive Impulses: Modified Damage-Extent Method Incorporating Structural Capacity

Abstract This study introduces an enhanced damage-extent method that incorporates the structural load-bearing capacity of the hull to assess the vulnerability of naval ships to explosive loads. This vulnerability assessment predicts the area of damage to the hull structure and calculates the probability of onboard equipment experiencing functional losses due to the explosive load, thus allowing various design alternatives to be evaluated. The proposed methodology improves upon traditional damage-volume-based approaches, such as damage-radius and ellipsoid methods, by considering the hull's structural stiffness and intrinsic damage resistance. It integrates the hull's structural resistance to the load, enhancing the damage assessment process for both the hull and equipment. This approach facilitates damage prediction for different hull designs by comparing the allowable impulse with the explosive pressure. In assessing the functionality loss and vulnerability of the equipment within the damaged hull, the network of equipment functions is considered. An anti-ship cruise missile with a sea-skimming trajectory is investigated as the explosive charge, with procedures established to simulate its trajectory and impact location on the hull. Hundreds of potential internal and external explosion points are generated, predicting the explosive pressure at each location. The shock wave, including incident overpressure, reflection pressure, and quasi-static gas pressure, is converted into impulses, taking into account the configuration of hull compartments to accurately predict these pressures and equivalent impulse. The resulting impulse is compared with the intrinsic damage capacity of each compartment's structure to assess potential damage. System network and fault tree analysis evaluate the loss of function and vulnerability of equipment within the damaged hull. Finally, the proposed capacity-based damage extent method demonstrates more accurate damage assessment compared to traditional methods, overcoming the limitations of damage-radius and ellipsoid approaches by considering hull strength

Wireless vibration testing and bridge deck damage identification using underneath maintenance walkway

Bridges will inevitably experience structural damage during long-term operation, which will decrease their structural load bearing capacity and durability. The vibration characteristics of bridge structures can be used as evaluation indicators for accurately diagnosing their deterioration. This study aimed at developing a vibration testing method for identifying bridge deck damage that does not affect traffic and is easy to implement. The vibration tests on the in-service bridge revealed it was mainly subjected to vertical vibrations, with the accelerations in the vertical direction about twice those in the horizontal direction. Based on fast Fourier transform analysis, the dominant vertical vibration frequencies were 2.34 Hz, 4.10 Hz, 10.30 Hz, 14.45 Hz and 18.75 Hz. A series of 0.1–0.3 Hz bandpass filters were used with those frequencies at the centers for modal analysis. The experimental results were then compared to the finite element analysis results. This study proposed a vibration-based damage identification method based on the differences between the bridge deck and both main steel girders. The study confirmed the convenience and effectiveness of using underneath maintenance walkways for wireless vibration testing.

A Review on Multi-Scale Toughening and Regulating Methods for Modern Concrete: From Toughening Theory to Practical Engineering Application.

Concrete is the most widely used and highest-volume basic material in the word today. Enhancing its toughness, including tensile strength and deformation resistance, can boost the structural load-bearing capacity, minimize cracking, and decrease the amount of concrete and steel required in engineering projects. These advancements are crucial for the safety, durability, energy efficiency, and emission reduction of structural engineering. This paper systematically summarized the brittle characteristics of concrete and the various structural factors influencing its performance at multiple scales, including molecular, nano-micro, and meso-macro levels. It outlines the principles and impacts of concrete toughening and crack prevention from both internal and external perspectives, and discusses recent advancements and engineering applications of toughened concrete. Insitu polymerization and fiber reinforcement are currently practical and highly efficient methods for enhancing concrete toughness. These techniques can boost the matrix's flexural strength by 30% and double its fracture energy, achieving an ultimate tensile strength of up to 20 MPa and a tensile strain exceeding 0.6%. In the future, achieving breakthroughs in concrete toughening will probably rely heavily on the seamless integration and effective synergy of multi-scale toughening methods.

[Translated article] Anatomical and biomechanical factors of osteoporotic vertebral fracture and the occurrence of cascade fractures

Osteoporosis weakens the structural strength of bone to such an extent that normal daily activity may exceed the capacity of the vertebra to bear this load. Vertebral fracture and deformity is a hallmark of osteoporosis. The detriment of trabecular bone properties alone cannot explain the occurrence of osteoporotic vertebral fracture. The ability of the spine to bear and resist loads depends on the structural capacity of the vertebrae, but also on loading conditions arising from activities of daily living or low-energy trauma. This review describes the mechanical properties of the vertebral bone, the structural load-bearing capacity of the various elements forming the spine, the neuromuscular control of the trunk, as well as the biomechanics of the loads to which the spine is subjected in relation to the presence of osteoporosis and the risk of vertebral fracture. A better understanding of biomechanical factors may help to explain both the high incidence of osteoporotic vertebral fractures and their mechanism of production. Consideration of these issues may be important in the development of prevention and management strategies.

Durability test study of laminated specimens for large glass fiber protective structures in seawater

The mechanical properties of glass fiber composite structures prepared by vacuum forming manufacturing process are influenced by various factors and have a certain degree of dispersion, resulting in unclear durability characteristics when applied in corrosive seawater engineering. Firstly, a variety of resin materials for underwater protective structures are tested for seawater degradation, and excellent resins that can still ensure the structural load-bearing capacity and stability after immersion are selected. Secondly, based on relevant standards and specifications, the article conducted seawater immersion aging tests at room temperature and accelerated seawater immersion aging tests at 60°C on glass fiber specimens of 430 epoxy bisphenol vinyl resin and 1967 polycyclic pentadiene resin. Finally, the degradation characteristics of strength, modulus, and impact toughness of the specimens were obtained through a series of mechanical property tests, such as bending, compression, shear and impact, under different aging time periods in room temperature and 60°C seawaters, respectively. The article summarizes the differences in the durability and mechanical properties degradation of large glass fiber protective structures with different resins during seawater immersion.

Engineering applications of fiberglass protective covers for oil and gas production facilities in submerged sand slope areas

Glass fiber reinforced materials have the advantages of light weight, high specific strength, and corrosion resistance, making them suitable for application in the structure of underwater oil and gas production protection systems. First, a variety of resin materials for underwater protective structures are tested for seawater degradation and mechanical properties, and excellent resins that can still ensure the structural load-bearing capacity and stability after immersion are selected. Secondly, the strength calculation and structural analysis of the designed fiberglass protective structure are carried out under the loading conditions of sand slope accumulation, fishing net towing and lifting. Afterwards, in order to facilitate the transportation and installation of large fiberglass shields, the paper innovatively proposes to adopt a segmented modular manufacturing solution. Finally, an underwater installation study is carried out considering the closed characteristics of the fiberglass shields. Based on the above series of studies, the glass fiber protective structure has been successfully installed in the South China Sea oilfield.

Factores anatómicos y biomecánicos de la fractura vertebral osteoporótica y la aparición de las fracturas en cascada

Osteoporosis weakens the structural strength of bone to such an extent that normal daily activity may exceed the capacity of the vertebra to bear this load. Vertebral fracture and deformity is a hallmark of osteoporosis. The detriment of trabecular bone properties alone cannot explain the occurrence of osteoporotic vertebral fracture. The ability of the spine to bear and resist loads depends on the structural capacity of the vertebrae, but also on loading conditions arising from activities of daily living or low-energy trauma. This review describes the mechanical properties of the vertebral bone, the structural load-bearing capacity of the various elements forming the spine, the neuromuscular control of the trunk, as well as the biomechanics of the loads to which the spine is subjected in relation to the presence of osteoporosis and the risk of vertebral fracture. A better understanding of biomechanical factors may help to explain both the high incidence of osteoporotic vertebral fractures and their mechanism of production. Consideration of these issues may be important in the development of prevention and management strategies.

Macroscopic and mesoscopic mechanism of hydration instability of the rock-grout coupled structure

In order to investigate the macroscopic and mesoscopic mechanism of hydration instability of rock-grout structure under the influence of moisture content, a direct shear test combined with particle flow code (PFC) simulation was conducted subject to various moisture content levels and normal stresses. The results show that a higher moisture content would compromise the load bearing capacity of soft rock anchorage structures by deteriorating the structural integrity of the surrounding rock and the bonding effect between the anchorage interfaces. The load bearing capacity of the surrounding rock is also rapidly reduced. The rock-grout structure has four main shear damage modes, which are influenced by both moisture content and normal stress. When the saturated moisture content is reached, the anchorage structure has lost its bearing capacity, and the rock is muddied and subsequently debonded from the bolt. The energy required to break the internal adhesion of the rock-grout structure under the effect of hydration is greatly reduced, resulting in easy decoupling and dispersion between the rock skeleton particles. In turn, the rock surface particles bonded by the anchor agent are separated from the deeper particles, resulting in the failure of the bonding surface and weakening the coupling effect between the anchor and the surrounding rock. According to the test results, the control measures for surrounding rock of muddy roadway are put forward.

Experimental and Finite Element Analyses of Adjustable Foundation Bolts in Transmission Towers

Uneven settlement of transmission tower foundations can result in catastrophic events, such as tower collapse and line failures, disrupting power transmission operations. To address the challenging repairs caused by uneven foundation settlement of transmission towers, we propose an adjustable foundation bolt (AFB). This paper provides a detailed theoretical analysis of the AFB’s stability and load-bearing capacity, including critical buckling force formulas and maximum normal stress expressions. Finite element simulations confirm the precision of our theoretical formulations. Additionally, we introduce a method using baffles to enhance its load-bearing capacity, analyzing the impact of different numbers of baffles through numerical simulations. The experimental results validate the effectiveness of baffles in enhancing structural load-bearing capacity. The device brings convenience and efficiency to the maintenance of transmission towers.

Fabrication and mechanical properties of thermoplastic corrugated sandwich panel with enhanced face‐core interface

AbstractThermoplastic sandwich structures are widely utilized in engineering fields due to their high specific strength and stiffness, recyclability, and impact toughness. The face‐core interface strength is crucial to maximize the performance benefits of sandwich structures. Two sizes of corrugated sandwich panels with hot‐melt bonding and resistance welding connection methods were fabricated. The mechanical properties of sandwich panels were compared using a combination of experimental, numerical, and analytical investigation. Edgewise compression (EC) and 3‐point bending (3 PB) tests were conducted to obtain load–displacement curves and investigate different failure modes of sandwich panels. The peak edge compression and bending loads of the resistance welded structures were 42% and 92% higher, respectively, and the face‐core interface was always well‐connected compared to those of the hot‐melt bonding. The results indicate that the resistance welding method can be utilized as a core bonding technique for thermoplastic composite sandwich structures and has great potential for aerospace application.Highlights A method that includes hot‐melt bonding and resistance welding are develop to produce thermoplastic composite corrugated sandwich panels (TPC‐CSPs). The TPC‐CSPs fabricated by resistance welding exhibit superior interface connection performance compared to hot‐melt bonding and this method enhance the structural load bearing capacity. The numerical and analytical method were presented to investigate the failure model, which was consistent with the experimental results.

Geometric Complexity Control in Topology Optimization of 3D-Printed Fiber Composites for Performance Enhancement.

This paper investigates the impact of varying the part geometric complexity and 3D printing process setup on the resulting structural load bearing capacity of fiber composites. Three levels of geometric complexity are developed through 2.5D topology optimization, 3D topology optimization, and 3D topology optimization with directional material removal. The 3D topology optimization is performed with the SIMP method and accelerated by high-performance computing. The directional material removal is realized by incorporating the advection-diffusion partial differential equation-based filter to prevent interior void or undercut in certain directions. A set of 3D printing and mechanical performance tests are performed. It is interestingly found that, the printing direction affects significantly on the result performance and if subject to the uni direction, the load-bearing capacity increases from the 2.5D samples to the 3D samples with the increased complexity, but the load-bearing capacity further increases for the 3D simplified samples due to directional material removal. Hence, it is concluded that a restricted structural complexity is suitable for topology optimization of 3D-printed fiber composites, since large area cross-sections give more degrees of design freedom to the fiber path layout and also makes the inter-layer bond of the filaments firmer.

Experimental and numerical evaluation of geometrical imperfection effects on the load bearing capacity of small-scaled voussoir arches

The study of the behaviour of masonry arches represents a complex problem, which involves different aspects that can significantly affect the load bearing capacity of such structures. In this regard, geometrical imperfections, such as the irregular shape of the arch blocks, the initial position of the first and last voussoirs (boundary conditions), the alignment between the adjoining blocks and the rounded corners of each block, play an important role. An experimental campaign was conducted on a toy arch made by eleven irregular blocks, with the aim of evaluating the effect of such irregularities. A numerical model was developed basing on lower bound (LB) and upper bound (UB) limit analysis approaches (referred to as the static and the kinematic theorem, respectively). A linear programming (LP) solving algorithm was implemented in the software MATLAB and used to solve the minimization/maximization problems. The probability distribution of each considered nonlinearity was estimated, the results of the numerical analysis were correlated with the experimental outcomes and a Montecarlo simulation was carried out to validate the hypothesised probability distributions.

Optimization of geometrical factors for enhanced performance of carbon fiber reinforced polymer cores under transverse loading

The high strength-to-weight ratio and ease of manufacturing of composite materials make them widely used across a variety of industries. A commonly used method of improving composite structure load-bearing capacity is to employ carbon fiber-reinforced polymer (CFRP) cores. The mechanical properties of CFRP, however, vary in different directions due to its anisotropic behavior. Due to higher tensile strength along the fibers, anisotropy can lead to failure based on directions other than the fiber orientation. A thorough analysis of CFRP core failure modes has been conducted. Experimental analysis, finite element analysis, and micromechanical modeling techniques have been used in these studies. In this research, specific emphasis has been placed on understanding failure behavior under transverse loading conditions. Failure modes have been thoroughly examined in relation to geometric parameters such as interference, wedge angle, and friction coefficient. Modeling CFRP core failure and displacement behavior was carried out using FEA simulations to validate the research findings. A comparison of the obtained results with existing literature ensured that they were accurate and reliable. Additionally, response surface methodology was employed for optimization, aiming to minimize two critical factors: radial compressive stress and core displacement. By minimizing these factors, the performance and reliability of CFRP cores in applications related to grid capacity can be enhanced. The analysis of the research data revealed that the friction coefficient and interference play significant roles as interacting factors, albeit with opposite impacts on the stresses within the CFRP cores. The optimal values for interference and friction coefficient were found to be 0.0224 mm and 0.4, respectively, to minimize radial stress. Furthermore, the wedge angle exhibited a substantial influence on core displacement, with an optimal value of 3.5°.

Effects of adhesive layer thickness on the fracture properties of a concrete-epoxy resin interface

Adhesive layer thickness is a crucial factor that affects the performance of interfaces in cement-based composite structures. However, the influence of adhesive layer thickness on the fracture properties of concrete–epoxy resin remains unclear. In this study, a two-parameter fracture model of a concrete-epoxy resin interface from the perspective of fracture mechanics. Digital image correlation (DIC) technique was used to investigate the evolution of the fracture process zone (FPZ) of nine specimens with adhesive layer thicknesses of 2 mm, 5 mm, and 8 mm, respectively. The interfacial fracture toughness parameters of the concrete-epoxy resin interface were determined based on the four-point bending (FPB) tests. The test results indicated that increasing the adhesive layer thickness changed the failure mode of the interface from approximate-brittle to quasi-brittle. The load-carrying capacity and interfacial stiffness of the concrete-epoxy resin interface decreased by approximately 13.8 % and 61.1 % with an adhesive layer thickness from 2 mm to 8 mm, respectively. The deflection across the specimen increased by approximately 37.2 % with an increase in adhesive layer thickness due to the lower elastic modulus of epoxy resin compare to the concrete. Furthermore, the FPZ for the adhesive layer thickness of 5 mm was the longest; it was approximately 18.7 % longer than that for the test specimen with an adhesive layer thickness of 2 mm. In terms of structural load-bearing capacity and fracture toughness, the concrete-epoxy resin interface exhibited the best working performance when the thickness of the adhesive layer was 5 mm.

Physical informed neural network for thermo-hydral analysis of fire-loaded concrete

In the event of a fire within a tunnel, the rapid and substantial increase in temperature can prompt swift fractures within the concrete lining. This situation can severely compromise the structural load-bearing capacity and overall safety of the tunnel. The intricate interplay of factors within the tunnel, including temperature, humidity, and pore pressure, necessitates the adoption of a thermo-hydro coupled model for comprehensive analysis. However, these highly coupled models exhibit profoundly nonlinear characteristics that cannot be readily solved through analytical means. In this study, a Physics-informed neural network (PINN) is harnessed to address this intricate multi-field coupled issue. Neural networks possess a significant advantage in their capacity to autonomously differentiate and directly capture variations within the spatiotemporal domain. Through a comparison with experimental results, the proposed method’s reliability is effectively demonstrated. The research findings hold the potential to significantly aid engineering professionals in swiftly conducting fire resistance assessments and risk evaluations for tunnels, whether they are under construction or already in operation.

Experiment and Numerical Simulation on Damage Behavior of Honeycomb Sandwich Composites under Low-Energy Impact

It is well-established that the honeycomb sandwich composite structures are easily prone to damage under low-energy impact. Consequently, it would lead to a dramatic decrease in structural load-bearing capacity and a threat to overall safety. Both experimental and numerical simulations are carried out to investigate the impact damage behavior of honeycomb sandwich composite specimens. The damage mode, damage parameters, and contact force-time curves of three types of panel materials with T300, T700, and T800 are obtained under different impact energies of 10 J, 20 J, and 40 J by the drop-weight impact experiment. Moreover, digital image correlation (DIC) tests are used to measure the deformation and strain of the lower panel. The experimental results reveal that the degree of damage increases with increasing impact energy. Particularly, the T300 panel specimen exhibits visible fiber fracture when subjected to an impact energy of 40 J. The impact process involves matrix cracking, fiber fracture, and delamination of the upper panel occurring first, followed by immediate crush damage to the honeycomb core and, finally, slight fiber damage to the lower panel. Due to its higher strength, the T800 panel specimen exhibits the highest damage resistance compared to the T700 and T300 panel specimens. To consider the microscopic failure criteria and various types of contact during the impact process, a finite element model of honeycomb sandwich composites is established, and numerical simulation analysis of low-energy impact is performed to determine the damage mode, damage size, and contact-force curves. Comparative analysis demonstrates good agreement between the simulation and experimental results. The findings of this study provide valuable technical support for the widespread application of honeycomb sandwich composites in the aviation field.