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Coalbed methane (CBM) is an increasingly important unconventional natural gas. Production logging can provide important information about the production status of each layer in a CBM well, which is crucial for developing and adjusting development plans. However, currently, only open-hole logging is done for CBM wells, and there is no mature technology for production testing of wells that produce low amounts of gas. To address this issue, a new method has been proposed in this paper for measuring the production profile of CBM wells. This method is based on the pressure difference method and measures the gas–liquid two-phase flow in a 125 mm vertical rising circular tube. The researchers established a simulation model of the CBM wellbore pressure difference method and obtained four flow patterns: bubble flow, slug flow, churn flow, and annular flow. We studied the relationship between the pressure difference and gas and water flow rates at different positions and spacing between measuring points in the wellbore. A differential pressure flowmeter without a throttling device was developed, and gas–liquid dynamic experiments were carried out through a simulation experiment platform to verify the feasibility of the flowmeter. Two well field tests were conducted in Shanxi CBM fields using differential pressure flowmeters, which accurately and quantitatively measured the stratified gas production of CBM wells. This technology can help improve the productivity and development efficiency of CBM wells. [ABSTRACT FROM AUTHOR]

For two-dimensional (2D) materials, the exact thickness of the material often dictates its physical and chemical properties. The 2D quantum material WTe2 possesses properties that vary significantly from a single layer to multiple layers, yet it has a complicated crystal structure that makes it difficult to differentiate thicknesses in atomic-resolution images. Furthermore, its air sensitivity and susceptibility to electron beam-induced damage heighten the need for direct ways to determine the thickness and atomic structure without acquiring multiple measurements or transferring samples in ambient atmosphere. Here, we demonstrate a new method to identify the thickness up to ten van der Waals layers in Td-WTe2 using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy image simulation. Our approach is based on analyzing the intensity line profiles of overlapping atomic columns and building a standard neural network model from the line profile features. We observe that it is possible to clearly distinguish between even and odd thicknesses (up to seven layers), without using machine learning, by comparing the deconvoluted peak intensity ratios or the area ratios. The standard neural network model trained on the line profile features allows thicknesses to be distinguished up to ten layers and exhibits an accuracy of up to 94% in the presence of Gaussian and Poisson noise. This method efficiently quantifies thicknesses in Td-WTe2, can be extended to related 2D materials, and provides a pathway to characterize precise atomic structures, including local thickness variations and atomic defects, for few-layer 2D materials with overlapping atomic column positions. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the self‐compacting alkali‐activated slag concrete‐filled cold‐formed steel tubes (SACFST) stub columns under axial compression. The innovative combination of alkali‐activated slag concrete (AASC) with concrete‐filled steel tubes (CFST) enhances both sustainability and structural performance. AASC, known for its eco‐friendly benefits compared to conventional concrete, was developed using industrial wastes, contributing to green construction practices. Based on Taguchi's L‐9 orthogonal array, nine mixes of self‐compacting alkali‐activated slag concrete (SASC) were developed, achieving impressive flowability exceeding 700 mm and compressive strengths ranging from 48 to 69 MPa. Additionally, split‐tensile strengths between 3.8 and 5.7 MPa, flexural strengths from 6.3 to 8.2 MPa, and a modulus of elasticity between 27.6 and 32.9 GPa were observed. Nine circular CFSTs containing SASC mixes were tested under axial compression, and a finite element model was developed to simulate their results. The experimental results were compared with standards from ACI 318, AIJ‐97, AISC‐360, AS 5100, and EC‐4, to evaluate the accuracy of axial capacity predictions. Among these standards, EC‐4 and AS 5100 provided the closest estimates, with mean PTest/PEC4 and PTest/P5100 ratios of 1.03 and 1.04, respectively, indicating a high level of accuracy. These findings highlight the potential of SACFST in advancing sustainable and resilient construction practices, laying the groundwork for future applications in structural engineering. [ABSTRACT FROM AUTHOR]

In order to study the fatigue performance and fatigue failure mode of the composite box girder with steel bottom plate and corrugated webs (SBCSWs), the model beam was made and the constant and variable amplitude fatigue experiment were performed. Combined with ABAQUS finite element software, the strain, deflection, and fatigue failure mode of the composite box girder with SBCSWs were analyzed. The results showed that the slope of the load–deflection curve, the slope of the load–strain curve, and the neutral axis height of the model beam did not change during the constant amplitude fatigue test. In the variable amplitude fatigue test, as the fatigue loading time and fatigue load amplitude increased, the slope of the load–deflection curve and the slope of the load–strain curve of the model beam decreased significantly, while the neutral axis height increased significantly. The section strain of the composite box girder with SBCSWs was consistent with the quasi‐plane section assumption. The fatigue failure of the composite box girder with SBCSWs began at the stress concentration at the junction of the steel bottom plate and the corrugated webs. The fatigue fracture section has typical fatigue fracture characteristics. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the crushing performance of four different composite lattice cylinder structures (hexagonal, circular, square, and triangular) under quasistatic compression loading using the finite element method. The numerical model was developed by performing progressive damage analysis with the MAT-54 material model in the LS-DYNA finite element software. The crushing performance (peak force (PF), mean crushing force (MCF), crushing force efficiency (CFE), and specific energy absorption (SEA)) and damage types of composite cylinders for different lattice structures, specimen thicknesses, lengths, material types and compression directions (axial and tangential) were determined and compared with results from other studies in the literature. At the end of the study, it was determined that the PCF value of the square lattice structure was 19.3% higher than hexagonal lattice structure, 37.6% higher than the circular lattice structure, and 33.4% higher than triangular lattice structure for axial loading. The AL specimen exhibited the highest EA value with 171 J, while the CFRP specimen had the highest SEA value with 4.2 J/g. The CFE value was the highest for the AL specimen. The deformation behavior of lattice cylinders varied primarily according to the cell type. [ABSTRACT FROM AUTHOR]

This article takes STC long and short columns as the research objects, and first conducts quasi-static tests to preliminarily explore the failure characteristics of STC long and short columns under horizontal reciprocating loads. Then, a large number of numerical analysis models are established to explore the influence of coaxial compression ratio, steel pipe wall thickness, wood cross-sectional area, and bending point height on the seismic performance of STC long and short columns through numerical analysis. The results indicate that although the trend of changes in STC long columns and short columns under these factors is the same, STC long columns mainly resist bending and compression, while STC short columns mainly bear shear and bending resistance. Finally, the calculation formulas for the compressive bending bearing capacity of STC long columns and the shear bending bearing capacity of STC short columns were derived through theoretical analysis. The accuracy and safety of the formulas were verified through a large number of numerical simulation results. [ABSTRACT FROM AUTHOR]

To study the flexural behavior of hybrid reinforced concrete (hybrid‐RC) beams with FRP and steel bars, this paper used ABAQUS finite element (FE) software to model and nonlinear analyze the hybrid‐RC beams and investigate the effects of effective reinforcement ratio, concrete strength, and FRP bars type on the flexural behavior of hybrid‐RC beams. In addition, the FRP bars stress, flexural bearing capacity, and ductility formulas for hybrid‐RC beams were fitted based on the FE results, and existing literature data were used to verify their accuracy. The FE model results indicated that the effective reinforcement ratio, FRP bars type, and concrete strength significantly impacted the flexural bearing capacity and deformation performance of hybrid‐RC beams. Increasing the strength of concrete improved the flexural bearing capacity and ductility of hybrid‐RC beams; increasing the effective reinforcement ratio and the elastic modulus of FRP bars increased the flexural bearing capacity of the hybrid‐RC beams but decreased its ductility. In addition, the fitted FRP bars stress, flexural bearing capacity, and ductility calculation formulas can quickly and conveniently predict the flexural bearing capacity and ductility of hybrid‐RC beams. [ABSTRACT FROM AUTHOR]

This study systematically investigates the enhancement effects of different fiber-reinforced polymer (FRP) materials on the axial compressive performance of concrete. Through experimental evaluations of single-layer, double-layer, and composite FRP reinforcement techniques, the impact of various FRP materials and their combinations on concrete's axial compressive strength and deformation characteristics was assessed. The results indicate that single-layer CFRP reinforcement significantly improves concrete axial compressive strength and stiffness, while double-layer CFRP further optimizes stress distribution and load-bearing capacity. Among the composite FRP reinforcements, the combination with CFRP as the outer layer demonstrated superior performance in enhancing the overall structural integrity. Additionally, numerical analyses of the mechanical behavior of the reinforced structures were conducted using ABAQUS 2023HF2 finite element software, which validated the experimental findings and elucidated the mechanisms by which FRP influences the internal stress field of concrete. This research provides theoretical support and empirical data for the optimized design and practical application of FRP reinforcement technologies in engineering. [ABSTRACT FROM AUTHOR]

This article aims to provide an overview of the fire resistance of concrete‐filled steel tube beam columns and the importance of fire resistance in building design and construction. Ten experimental models were developed to predict the behavior of different types of concrete‐filled steel tubes and beams‐columns under Fire resistance conditions (ISO‐834) under cyclic loading in two groups. The results show the type of concrete effect on moment‐rotation characteristics. Also, increasing the length of the stiffener on the column increases the load and moment capacity, but also affects the failure mode. Moreover, the ideal situation is to use PP fiber concrete in concrete‐filled steel tube structural elements where displacement and rotation capacity are prominent. Withal, the recycling of fire‐exposed steel beam‐to‐column tube element is available by filling the inner space with C50 and/or polypropylene fiber reinforced concrete, also as a fireproof member. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the applicability of externally bonded fiber‐reinforced polymer (FRP) composites to enhance the structural performance of steel–concrete composite beams with web openings in terms of load capacity and stiffness. In order to achieve this aim, the ABAQUS software was used to create a three‐dimensional (3D) non‐linear finite element model (FEM) to simulate the behavior of FRP‐strengthened continuous composite beams with web openings exposed to monotonic loadings. After ascertaining the accuracy of the proposed model's results in successfully predicting failure patterns and load capacities of the experimentally tested specimens available in the literature, the suggested model was used to create a parametric study. The parametric study focused on the impacts of the opening location, opening shapes, and opening area on the failure pattern, load carrying capacity, and stiffness of continuous steel–concrete composite beams. Additionally, strengthening the web openings using different configurations and lengths of FRP strips with and without bolts was investigated. Results showed that the presence of web openings in location 2 exhibited the lowest load capacity of all investigated beams (20.80%–42.50% lower than the control composite beam). Moreover, the continuous composite beams with a circular opening were the best case and gave a higher failure load as compared to the rectangular opening at all locations. Additionally, all the simulated FRP‐strengthened composite beams in the third group demonstrated significant values of load capacities and stiffness among all the analyzed specimens. [ABSTRACT FROM AUTHOR]

Recycled aggregate concrete contributes to the recovery of construction and demolition waste, which is a growing societal concern. The technical feasibility of recycled aggregate concrete has been extensively tested and validated and the revisions of codes are already including clauses for recycled aggregate concrete specification and design. However, there are still doubts regarding its structural behavior. This article assesses the suitability of Eurocode 2 design clauses for concrete elements under compression when used for recycled aggregate concrete design. This is done through the analysis of model uncertainties that are estimated from a database collected from laboratory experiments on columns. Both the current version of Eurocode 2 (with and without taking confinement into account) and the upcoming (second generation) Eurocode 2 are considered. A database was collected with clearly defined criteria and includes coarse recycled aggregates produced from concrete waste, since columns made with other types of recycled aggregates are scarcely tested and do not represent the current status for structural recycled aggregate concrete design and production. The statistics of the model uncertainty for natural and recycled concrete columns were compared and it was observed that the mean model uncertainty tends to decrease slightly when recycled aggregates are used. However, a preliminary assessment of whether a partial factor for recycled aggregate concrete compression design should be used concluded that this partial factor is not necessary to ensure reliable design and the design of columns may be carried out using the same formulae used for conventional concrete. The format proposed may be used for other resistance models, provided that the partial factor is calibrated for each resistance model. [ABSTRACT FROM AUTHOR]

Because the cement content is inexorably growing, CO2 emissions from the cement industry are becoming unavoidable. The use of rice husk ash (RHA) makes the system environmentally benign. This paper investigates the effect of RHA and manufactured sand (M-Sand) on the axial capacity of circular Concrete Filled Steel Tube (CFST) specimens subjected to axial compression. Thirty-two CFST specimens infilled with self-compacting concrete (SCC) with a replacement of RHA and M-Sand to cement and fine aggregate in 0%, 15%, 20% and 25% proportions are subjected to axial compression. Results show that use of RHA beyond 20% decreased the compressive strength of concrete and eventually decreased the axial capacity of CFST and occurred higher local buckling irrespective of their L/D ratios. Failure modes, strength index, confinement along with steel and concrete contribution on axial capacities of CFST specimens are studied. The axial capacities of the specimens were compared with various design code results such as: American concrete institute, Australian Standards, Chinese code, Eurocode, and Japanese code. Among all the codes, Chinese code overestimated the test results and hence, the axial capacity equation is altered and compared the results with test data along with 278 circular CFST data available from literature and found the results to be accurate. [ABSTRACT FROM AUTHOR]

To enhance the energy-absorbing capacity of the energy absorber, the circular metal foam-filled tube (CMFFT) under external inversion over a circular die is designed. According to the rule of energy conservation, a theoretical model for the inversion of the CMFFT over a circular die is proposed, considering the radial bending of the CMFFT and the circumferential expansion of the CMFFT in the contact region and disengaging region, and the foam compression. Then, the die inversion deformation of the CMFFT under axial compression is investigated by the commercial software ABAQUS/Explicit. It is seen that the analytical model captures the numerical results reasonably. Next, the influences of the strength of the metal filled foam, the circular corner radius of the die, the average radius of the metal circular tube and the wall thickness of the metal circular tube are discussed. It is found that the force increases with the strength of the metal filled foam and the average radius of the metal circular tube. In addition, the force firstly decreases and then increases with the increase of the radius of the circular die and the wall thickness of the metal circular tube. The absorbed energy increases with the wall thickness of the metal circular tube, the circular corner radius of the die, the average radius of the metal circular tube, and the strength of the metal filled foam. The optimum radius of the circular die is proposed based on the theoretical model. The special energy absorption (SEA) efficiency of the CMFFT under external inversion over a circular die is significantly better than the metal empty tube. The SEA ratio of the CMFFT is 130.21%, when the compressive strength of metal filled foam σ ¯ F = 0.0694 . It is demonstrated that the CMFFT under external inversion over a die is a good energy absorber. [ABSTRACT FROM AUTHOR]

The internal cavity of the foundation of a steel–concrete composite wind turbine tower (WTT) is designed to facilitate prestressed construction. The load-bearing mechanisms of this type of foundation are different from those of ring-type and anchor-type foundations commonly used in steel WTTs. Based on a real project, an integrated model of a prestressed tower–foundation–ground was built using the finite-element software Abaqus. The internal force and damage in the foundation of a steel–concrete WTT under extreme load conditions were studied using the static loading method. Under extreme load conditions, prestressed reinforcements were found to have little impact on the local pressure at the anchor end of the foundation. Prestressing the reinforcement effectively prevented concrete cracking and tower deformation. For areas experiencing extreme loads on both sides, simplified calculations for stress and reinforcement can be performed using calculation formulae for the bracket. [ABSTRACT FROM AUTHOR]

A detailed study of the behaviour of concrete-filled rectangular tubular flange girders (CFRFGs) was undertaken. The CFRFGs were steel beams in which the top flange plate is replaced with a concrete-filled steel section, resulting in greater load-carrying capacity and lateral torsional buckling resistance compared with a regular steel beam of similar proportions. They are complex members and their behaviour is governed by several interrelated parameters, which were studied in this work. Using the Abaqus program, a three-dimensional finite-element (FE) model was developed to investigate the flexural behaviour of simply supported CFRFGs. Using available experimental results, the computational model was validated and then used to study the influence of the most salient properties on the overall response. Based on a fundamental assessment of the behaviour, a simplified analytical model was developed to predict the capacity of these types of section in a way that is suitable for designers. The results were compared with those from the FE analysis and it was found that the analytical model is capable of providing an accurate depiction of the behaviour and the bending moment capacity. [ABSTRACT FROM AUTHOR]

Steel tube–reinforced concrete (STRC) columns are composite members consisting of an inner concrete-filled steel tube (ICFST) component and an outer reinforced concrete (ORC) component. These columns are commonly used in the bottom columns of high-rise buildings and bridge piers to withstand significant axial loads. However, the stress state of the components in a STRC composite column differs from that of a single confinement component. As a result, the existing lateral strain model and concrete constitutive model cannot be directly applied to describe the stress–strain development of each component. To address this issue, this study combines the existing confined concrete models with the stress balance condition and strain development characteristics of the cross section of a STRC composite column. Theoretical models are proposed to simulate the development of lateral strain and confining stress in both the ICFST component and ORC component. Additionally, the biaxial stress state of the steel tube is considered based on the generalized Hooke law and Prandtl-Reuss theory in the theoretical model. Consequently, an incremental iterative calculation model for the whole axial load–strain curve is proposed. The effectiveness of the proposed models is verified by comparing the calculation results with the experimental results. [ABSTRACT FROM AUTHOR]

The FRP wrapping of reinforced concrete columns is a simple way to increase the axial load capacity of such members with substandard concrete quality. A total of 2197 specimens were collected as a database to discuss the efficiency of predicting axial compressive strength of FRP-wrapped concrete columns according to several national and international guidelines. Various aspects of the database, including fiber type, unconfined strength and specimen geometry used to investigate the guidelines, and results are presented in terms of averages, standard deviations, and ratio of overestimated specimens. The performance of these expressions was compared with one another based on these statistical results and graphs, and those that captured the behavior best were identified for specific subsets. Recognizing the expressions' inadequacy in capturing efficiency improvements related to radius to area and confinement ratios, some improvements in the form of coefficients for lateral confinement stress in the Turkish Building Earthquake Code were introduced, specifically for certain subsets. [ABSTRACT FROM AUTHOR]

Investigations carried out on cellular steel beams so far were mainly focused on the behavior of non-composite homogeneous sections. Hybrid I-beams are built-up sections where different steel grades are used for flanges and web parts. But perforated hybrid hot-rolled I-sections, where the top and bottom T sections would have different steel grades, can be achieved due to their cutting process. This paper presents a comprehensive parametric study focusing on the inelastic behavior of hybrid and homogeneous cellular steel beams made from hot-rolled parent sections. Finite element modeling using ABAQUS software was employed to validate previously tested hybrid and homogeneous cellular steel beams made from hot-rolled sections. To observe the effect of hybrid sections; the results of hybrid cellular steel beams were compared to the homogeneous ones of the same geometry but with different materials property. A broad spectrum of parent sections (section ratio), restraining conditions, spacing to opening ratio, span lengths, and various steel grades were included in the analysis. Results showed that the upper Tee is mainly the governing part in cellular beams. Moreover, the use of hybrid cellular beams with successive steel grades showed more compatible results compared to sections with non-successive grades for both restrained and unrestrained sections failing under global buckling. According to Eurocode 3 design rules, a set of modified equations were proposed to be used for the Lateral Torsional Buckling resistance calculations of hybrid cellular beams made from hot-rolled sections. [ABSTRACT FROM AUTHOR]

Steel–concrete composite connections play a crucial role in facilitating the transfer of forces between steel and concrete structural elements. The safety of structures during fire incidents has garnered significant global attention. This study focuses on examining the behavior of steel–concrete composite beam–column connections with flush end-plate under both ambient temperature and fire conditions through numerical analysis. Parametric analysis was conducted after adjusting the numerical models. The parameters considered include beam and column profiles (represented as profile sets), negative longitudinal reinforcement ratio, degree of steel–concrete interaction, slab type, moment orientation, concrete strength, and steel strength. At ambient temperature, the primary failure mechanisms include local buckling of the column flange, bolt yielding, plate distortion, reinforcement yielding, excessive slab damage, and local buckling of the beam web near the connection. In fire scenarios, the flush end-plate beam-to-column connection failed due to local buckling and reinforcement yielding. Additionally, during the fire, the failure of bolts connecting the end-plate to the column was observed. Importantly, all variables in the parametric analysis influenced the behavior of the composite connection, both at ambient temperature and during fire scenarios. Furthermore, this study provides practical equations for calculating moment resistance and initial stiffness at ambient temperature, as well as reduced stiffness during a fire and accumulated rotational capacity variation, specifically for steel–concrete composite beam–column connections with a flush end-plate. [ABSTRACT FROM AUTHOR]

The suspended monorail is a new mode of rail transit with light weight, medium speed and low cost. It has a lightweight and aesthetically pleasing structure but has obvious limitations when spanning obstacles such as rivers and valleys. From the perspective of structural force and operational safety, this paper puts forward a new composite beam structure scheme, in which track piers and track beams are erected on the main beam of a cable-stayed bridge, overcoming the limitations of conventional suspended monorail spanning ability. To investigate the complex force situation and the load transfer path at the junction of the main beam of the cable-stayed bridge and the track beam piers, finite element models of steel box girder section and concrete box girder section were established using ANSYS software. The results showed that, in the steel box girder section, the pier load was mainly transferred to the diaphragm and the middle web directly connected to it. Among them, the diaphragm load experienced relatively uniform stress, while the middle web's stress was mainly concentrated within a 2-meter radius centered around the pier, which could be mostly transferred to the steel girder bottom plate. 58% of the pier's axial force was transferred to the directly connected diaphragm. During the transfer of the pier column's transverse bending moment, 58. 8% of the shear force was transferred to the directly connected diaphragm. During the transfer of the pier column's longitudinal bending moment, 53. 4% of the shear force was transferred to the middle web. In the concrete box girder section, the pier load was mainly transferred to the concrete web and diaphragm directly connected to it. The concrete stress was mainly concentrated within a 2-meter radius centered around the joint surface, and the pier load was basically transferred within about 0. 5 meters below the joint surface. 68. 8% of the pier's axial force was transferred to the directly connected diaphragm. During the transfer of the pier column's transverse bending moment, 86. 4% of shear force was transferred to the directly connected diaphragm. During the transfer of pier column's longitudinal bending moment, 44. 6% of shear force was transferred to the middle web. [ABSTRACT FROM AUTHOR]

This article was based on indoor simulated marine environment erosion tests using concrete, by analyzing the compressive strength, coating bonding strength and chloride ion diffusion behavior of marine cast-in-place concrete after erosion, and the effects of anti-corrosion coating / treating ages on the mechanical properties and durability evolution of marine cast-in-place concrete were studied. The results show that compared with concrete without anti-corrosion coating / treating, anti-corrosion coating / treating concrete using silane and polyurethane coating shows a decrease in compressive strength fc after erosion in marine tidal areas, and concrete fc gradually decreases with the increase of curing age tc . Anti-corrosion coating / treating can effectively improve the long-term chloride ion erosion resistance of marine cast-in-place concrete, and with the increase of curing age tc, the effects of anti-corrosion coating / treating on reducing the surface chloride ion content Cs and apparent chloride ion diffusion coefficient Da of concrete becomes more significant. Taking into account the development of mechanical properties of cast-in-place concrete in the marine tidal zone environment and the effectiveness of anti-corrosion coating / treating measures, it is recommended to use silane and polyurethane coatings for coating with a curing age of not less than 5 and 10 d, respectively. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of fly ash and steel fiber on the abrasion resistance of ultra-high performance concrete (UHPC), this paper performed macroscopic mechanical test, underwater abrasion resistance test and microscopic characterization such as SEM and MIP to investigate the effects of fly ash and steel fiber on the workability, mechanical properties, microstructure, and abrasion resistance of UHPC. The results show that the replacement of cement by fly ash delays the emergence of hydration peak by about 3 h, and the cumulative heat flow at 3 d is reduced by 18%, significantly improving the workability of UHPC. The incorporation of fly ash reduces the mechanical properties of UHPC in the early stage and has no effect on the mechanical properties in the later stage. The incorporation of steel fiber improves the flexural strength and compressive strength of UHPC. The flexural strength and compressive strength are increased by 82% and 47% respectively due to the composite mixing of steel fiber and fly ash under steam curing. The addition of fly ash has little effect on the abrasion resistance of UHPC, while the addition of steel fiber improves the abrasion resistance of UHPC, and the composite mixing of steel fiber and fly ash increases the abrasion resistance of UHPC by 58%. The compressive strength and abrasion resistance strength of UHPC show a significant positive correlation. The incorporation of fly ash reduces the most available pore size, porosity and capillary pore content, making the internal structure of matrix more uniform and denser. [ABSTRACT FROM AUTHOR]

This study investigates the behavior and capacity of concrete-filled steel tubes (CFTs) with rectangular and circular sections under various loading conditions: axial loads, pure-bending, and combined axial load-bending moments. A finite element-based numerical model is developed and validated against existing experimental data. Using an extensive databank generated from finite element analysis, this research proposes analytical empirical relations for determining the bearing capacity of rectangular and circular composite beams, columns, and beam–columns. These relations provide a direct, concise, and efficient method for calculating the ultimate strength of CFT members, making them valuable for engineering design. Comparisons between the proposed analytical results and previous experimental studies demonstrate the high accuracy of this method in analyzing rectangular and circular CFT member behavior. The findings contribute to a better understanding of CFT structural performance and offer practical tools for designers working with these composite elements. [ABSTRACT FROM AUTHOR]

One of the main barriers to the acceptance and adoption of fiber-reinforced polymers (FRPs) in structural engineering is the brittle failure mode and limited ductility caused by the elastic-brittle behavior of FRP materials. Introducing a compression-yield (CY) system is a promising way to improve the ductility of the structures. This study adopted perforated steel cylinders as CY systems. Six perforated steel cylinders with different parameters were tested, and the applicability of the existing constitutive model on the perforated steel cylinders was verified. A design approach for perforated steel members on the structures was proposed. Based on the proposed design approach, ultralightweight cement composite (ULCC)-filled carbon fiber-reinforced polymer (CFRP)-wrapped steel tube arches with perforated steel cylinders were designed and experimentally investigated. The ULCC-filled CFRP-wrapped steel tube arches with CY systems achieved high ductility while maintaining favorable bearing capacity. A model was then proposed to evaluate the damage degree of the structures based on the longitudinal strain in the CY system. The damage development of the structures can be detected based on the measurement of the CY system, which enables early warning to be provided before structural failure. [ABSTRACT FROM AUTHOR]

The hybrid fiber-reinforced polymer (FRP)–concrete–steel double-skin tubular column (DSTC) is an innovative composite member consisting of an outer FRP tube and an inner steel tube, with the space between them filled with concrete. The incorporation of ultrahigh-performance concrete (UHPC) in the DSTC yields numerous advantages over the DSTC with normal-strength concrete, particularly in terms of enhanced impact resistance. While the lateral impact behavior of UHPC DSTC has been investigated, its residual performance after lateral impact remains unexplored. To comprehend the postimpact behavior of UHPC DSTC, a series of specimens underwent lateral impact, followed by static axial compression. Additionally, intact specimens were subjected to static axial compression for comparative analysis. Subsequently, refined numerical models were developed and validated using the obtained test data. Detailed parametric studies were carried out to investigate the influences of key variables on the postimpact behavior of UHPC DSTCs. Finally, based on the ratio of residual midheight deflection to the column height, a prediction formula was proposed for the rapid damage evaluation of impacted UHPC DSTCs, and threshold values for different damage levels were suggested based on a defined damage index. [ABSTRACT FROM AUTHOR]

The use of externally bonded composite systems is recognized as an effective solution for strengthening existing reinforced concrete (RC) structures. Steel-reinforced grout (SRG) is an attractive option, because of its compatibility with the concrete substrate and mechanical properties. However, a critical aspect is the delamination that might affect the steel textile–mortar and the mortar–concrete substrate interfaces. An experimental and theoretical investigation of the SRG–concrete bond is reported in this paper. In particular, the bond performances of SRG-to-concrete joints, which varies the width of the SRG fabric, the displacement rate, and the applied load eccentricity, are analyzed for the stress that is associated with the bond capacity, slip, and failure modes based on the results that are obtained by direct single-lap shear tests. To assess a data set for model calibration, the findings of this paper and those in the technical literature are collected. Therefore, a machine learning (ML) approach that is based on an artificial neural networks (ANN) algorithm is implemented, and a new analytical formulation for the prediction of the SRG-to-concrete bond capacity is proposed. [ABSTRACT FROM AUTHOR]

The present study investigated the behavior of concrete‐filled steel tubes (CFST) and concrete‐filled double‐skin steel tubes (CFDST) of square and rectangular shapes after exposure to elevated temperatures. The infill concrete was prepared with granulated blast furnace slag (GBS) as fine aggregate, and no natural fine aggregate was used. A total of 20 CFST and CFDST specimens of both square and rectangular shapes were prepared. The specimens were heated at 200, 400, 600, and 800°C temperatures for 2 h and allowed to cool inside the furnace after heating. Axial load was applied to the specimens to check their behavior after exposure to fire. The reduction in the load‐carrying capacity was insignificant for the specimens heated at 200, 400, and 600°C for both square and rectangular CFST and CFDST conditions. The decrease in load‐carrying capacity was slightly higher in the case of CFDST specimens compared to CFST specimens. A three‐dimensional finite element model using ABAQUS software was proposed for predicting the behavior of the tested specimens. The proposed model could predict the behavior of both unheated and heated specimens with acceptable accuracy. [ABSTRACT FROM AUTHOR]

Previous research largely concentrated on predicting load‐carrying capacities of concrete‐filled steel tubes (CFST) confined with fiber‐reinforced polymer (FRP) wraps under pure concentric loads, neglecting the more complex failure mechanisms that occur under real‐life eccentric loading conditions. This study, therefore, employs both finite element modeling (FEM) and machine learning methods to accurately predict the load‐bearing capacities under both concentric and eccentric loading conditions. This research analyzed a comprehensive dataset comprising 128 experimental tests and an equivalent number of FEM simulations designed to evaluate their eccentric performance. These models have been thoroughly generated and validated against existing literature. Additionally, the developed ML models, particularly a hybrid deep learning model, demonstrated significant predictive accuracy, with an average R2 value of 0.969 across all model folds. Partial dependence analysis further highlighted the significant influence of concrete strength and the interactive effects of steel tube area and FRP wrap thickness on the load‐carrying capacity of the columns. Furthermore, to enhance cost‐efficiency and resource management compared with traditional laboratory testing, a user‐friendly graphical user interface (GUI) has been developed and hosted on an open‐source platform such as GitHub. This interface supports real‐time, precise predictive capabilities and promotes a collaborative environment for ongoing model refinement and improvement. [ABSTRACT FROM AUTHOR]

This study analysed the strengthening process of a classical steel–concrete composite beam. The beam consisted of a reinforced concrete slab connected by shear studs to an IPE steel profile. The key idea was that the composite beam was strengthened under load. This process simulated an actual reinforced structure that is always subjected to dead loads, with possible service loads. This study assumed that strengthening was implemented to increase the load-carrying capacity and stiffness, not as a way for simulation a repair. The strengthening consisted of expanding the steel part of the beam by welding an additional plate to the bottom flange of the IPE profile. This study included the results of numerical analyses conducted in Abaqus software and lab results. A three-dimensional numerical model was created, taking into account the non-linear behaviour of concrete and steel, the susceptibility of the composite at the joint plane, and the residual stresses created during welding. A full-scale strengthening of the composite beams under load was carried out. Comparison of the results obtained in the experimental tests and numerical analyses showed a very high convergence of the results, as well as in terms of the non-linear operation of steel and concrete. This confirmed the validity of the created numerical model, which can be the basis for further research into the process of optimal strengthening of composite elements. [ABSTRACT FROM AUTHOR]

Featured Application: The strengthening of the columns and the connections of the columns with the beams for reinforced concrete buildings designed and constructed according to older codes is crucial for regions prone to seismic activity. Herein, the application of the innovative C-FRP ropes for the strengthening of these structural elements is featured. The experimental results yielded from testing real-scale columns demonstrated that this strengthening technique is both highly effective and easy to implement. Moreover, it is emphasized that the C-FRP ropes technique can easily be applied by the practicing engineer in structures with complex configuration without any geometrical restraints. The application of the innovative C-FRP ropes for the strengthening of reinforced concrete columns is experimentally examined. Two real-scale specimens with the same geometrical characteristics and the same steel reinforcements were constructed for the needs of this investigation. The primary objective of the study is to investigate the efficacy of the use of C-FRP ropes as externally mounted reinforcement for the strengthening of deficient external columns. In this direction, (a) C-FRP ropes are applied as longitudinal reinforcement of the column for the increase in the flexural strength, (b) C-FRP ropes are applied as external confining stirrups in the critical end parts of the column for the improvement of the concrete strength and the development of local element ductility, and finally (c) C-FRP ropes are applied as external stirrups in the form of diagonal X-shaped reinforcement for the increase in the capacity of the part of the column connected with the beam (joint panel). Both specimens are tested under the same cyclic loading procedure that comprises seven steps and each step includes three full loading cycles. The maximum loads of the strengthened specimen at the three loading cycles of the seventh step were 40%, 72% and 87% higher than the corresponding ones of the unstrengthened specimen. On the other hand, the measured shear deformations of the joint panel of the pilot (unstrengthened) specimen at the sixth and the seventh steps were 43% and 44% higher than the corresponding ones of the strengthened specimen. In general, it is concluded that the strengthened column exhibited improved hysteretic response and the whole behavior was apparently improved compared to the pilot specimen without strengthening in terms of maximum loads per loading step, dissipated energy, and shear deformations of the joint panel. In particular, it is stressed that the measured shear deformations of the joint panel and strain gauge measurements have substantiated that the column and the connection panel of the strengthened specimen remain almost intact, whereas damage and eventually failure have been located in the column and the joint panel of the pilot specimen. Additionally, it is emphasized that the C-FRP ropes can easily be applied in structures with complex configuration without any geometrical restraints. [ABSTRACT FROM AUTHOR]

To solve the problem of a large amount of fly ash accumulation and study the axial compression and bearing capacity prediction of the self-compacting fly ash concrete filled circle steel tube (SCCFST) columns, eight specimens are designed to explore the impact of concrete strength grade, internal structural measures, and additional parameters. The stress, progression of deformation, and failure mode of each specimen are observed during the loading process. The load–displacement curves, load-strain curves, characteristic load and displacement, ductility, and stiffness degradation are analyzed. The findings revealed that shear deformation occurred predominantly in the middle and upper portions of the steel tubes. Enhancing the strength of the concrete or adopting internal structural measures could increase the bearing capacity and ductility of the specimens. The peak load and ductility could be increased by up to 17.6 and 53.6%, respectively. The proposed unified calculation equation for the axial compression bearing capacity of SCCFST columns demonstrates notable reliability and precision. Furthermore, these tests offer valuable references for the engineering application of various forms of SCCFST columns, which are of significant importance in practical engineering. [ABSTRACT FROM AUTHOR]

AbstractIn order to study the seismic performance of Reinforced Concrete columns strengthened with Carbon Fiber Reinforced Polymer-steel tube self-compacting concrete, seven strengthened columns and one unstrengthened column were designed and manufactured with the main parameters of axial compression ratio, self-compact concrete strength, steel tube shape and steel tube thickness. The hysteresis curve, skeleton curve, ductility, energy dissipation capacity, stiffness, steel tube surface and steel bar strain variation of the specimens were analyzed. The test results show that the strengthened part of the specimen has good cooperative working ability with the RC column, and the failure process and failure mode of the specimen are similar to those of the concrete filled steel tube. Under the action of horizontal reciprocating load, the concrete at the bottom of the strengthened column is cracked; with the increase of horizontal displacement, the hysteresis curve becomes full and the energy dissipation capacity increases. The finite element software ABAQUS is used to model and analyze the specimens. The simulation results are in good agreement with the experimental results. It is proved that the simulation is reasonable and effective in unit selection, contact setting, meshing and material constitutive selection. The hysteresis curve, skeleton curve and failure mode of each specimen are obtained. [ABSTRACT FROM AUTHOR]

The first-order second-moment checking point method was introduced to judge the instability probability and evaluate the stability of the TCURM. The frequency–response stability calculation and the reliability results were compared, and a frequency–response stability and reliability analysis method was proposed. Taking the Zengziyan W12# unstable rock mass in Nanchuan, Chongqing, China, as an example, the calculation shows that the dynamic indexes and geological indexes decrease as the stiffness of the deterioration area decreases. According to the statistical data of the laboratory test and the field investigation, reliability theory is used to evaluate the stability of the TCURM, and the failure probabilities are 80.3% and 96.27% under natural and saturated conditions, which correspond to states of poor stability and instability, respectively. The reliability evaluation results are consistent with the conclusion of the frequency–response stability analysis. The new method can provide a theoretical basis for developing the dynamic monitoring and early warning indicators of the TCURM and disaster prevention and mitigation in mountainous areas. [ABSTRACT FROM AUTHOR]

The chloride migration coefficient (CMC) of concrete is crucial for evaluating its durability. This study develops ensemble models to predict the CMC of concrete, addressing the limitations of traditional, labor-intensive laboratory tests. We developed three ensemble models: an inverse variance-based model, an Artificial Neural Network (ANN)-based model, and a tree-based model using the random forest regression algorithm. These models were trained on a dataset comprising 843 concrete mix proportions from existing literature. Results indicate that ensemble models outperform single models such as ANN and Support Vector Regression (SVR) in predicting CMC, with the combined random forest and ANN model showing the highest accuracy. Sensitivity analysis using Shapley Additive Explanations (SHAP) reveals that the CMC is most influenced by the water-to-cement ratio and curing age. Additionally, we designed a graphical user interface (GUI) to facilitate the practical application of our models. This research offers a robust methodology for evaluating concrete durability and potential for extending the prediction to other concrete properties. [ABSTRACT FROM AUTHOR]

Purpose: The external confinement provided by the fiber-reinforced polymer (FRP) sheets leads to an improvement in the axial compressive strength (CS) and strain of reinforced concrete structural members. Many studies have proposed analytical models to predict the axial CS of concrete structural members, but the predictions for the axial compressive strain still need more investigation because the previous strain models are not accurate enough. Moreover, the previous strain models were proposed using small and noisy databases using simple modeling techniques. Therefore, a rigorous approach is needed to propose a more accurate strain model and compare its predictions with the previous models. Design/methodology/approach: The present work has endeavored to propose strain models for FRP-confined concrete members using three different techniques: analytical modeling, artificial neural network (ANN) modeling and finite element analysis (FEA) modeling based on a large database consisting of 570 sample points. Findings: The assessment of the previous models using some statistical parameters revealed that the estimates of the newly recommended models were more accurate than the previous models. The estimates of the new models were validated using the experimental outcomes of compressive members confined with carbon-fiber-reinforced polymer (CFRP) wraps. The nonlinear FEA of the tested samples was performed using ABAQUS, and its estimates were equated with the calculations of the analytical and ANN models. The relative investigation of the estimates solidly substantiates the accuracy and applicability of the recommended analytical, ANN and FEA models for predicting the axial strain of CFRP-confined concrete compression members. Originality/value: The research introduces innovative methods for understanding FRP confinement in concrete, presenting new models to estimate axial compressive strains. Utilizing a database of 570 experimental samples, the study employs ANNs and regression analysis to develop these models. Existing models for FRP-confined concrete's axial strains are also assessed using this database. Validation involves testing 18 cylindrical specimens confined with CFRP wraps and FE simulations using a concrete-damaged plastic (CDP) model. A comprehensive comparative analysis compares experimental results with estimates from ANNs, analytical and finite element models (FEMs), offering valuable insights and predictive tools for FRP confinement in concrete. [ABSTRACT FROM AUTHOR]

Limited research is available in the literature to investigate the presentation of normal strength concrete-filled steel tube (CFST) circular compression elements under compression loading by considering various material and geometric coefficients. Thus, the present study investigates the mechanical behavior of CFST compression elements employing nonlinear finite element analysis (NLFEA), empirical/theoretical modeling, and a newly developed Artificial Neural Network (ANN) model, based on a large experimental database of 1223 samples. The NLFEA modeling is performed in ABAQUS (6.14) with an improved concrete damaged plasticity model for laterally restrained concrete. Various geometric and material properties are considered, for parametric NLFEA estimates preliminary validated toward the available experimental database. A new ANN model for the load-carrying capacity of CFST circular elements was also offered by employing the experimental database. The comparison between the calculations of the NLFEA model, empirical model, and ANN model displayed a close agreement with the database results. [ABSTRACT FROM AUTHOR]

Progressive collapse is a phenomenon where initial local failure of a component spreads to surrounding components, resulting in the collapse of the entire structure or most of it. This research is based on the component method (joint simplification model) and the hierarchical shell element macromodeling approach (composite floor simplification model). A three-dimensional spatial composite structural model was established using the finite-element (FE) software ANSYS/LS-DYNA. Experimental results were used to validate the reliability of the FE model. Based on these methods, a typical prototype structural model designed by the National Institute of Standards and Technology (NIST) was established, and a computational analysis of progressive collapse due to component removal was conducted. The results showed that the occurrence of structural collapse depends on the type of beam-column connection, floor level, and type of component removed. Also, it was found that structural collapse is more likely to occur when interior columns, gravity columns (nonresisting lateral column), and low-floor columns are removed. After column failure, the path of vertical loads is mainly transmitted to the columns within the area of direct collapse effect. The area within the potential collapse effect is also exposed to a severe impact phenomenon due to falling floors. Based on the collapse modes and internal force transfer path, an innovative collapse-prevention design method (structural response-based design, or SRBD) is proposed. The SRBD method predicts the collapse response of structure at a theoretical level and avoids redundant modeling and nonlinear calculations in collapse-prevention design. A comparison with collapse response of the NIST model shows that the prediction accuracy is approximately 90%. The SRBD method provides guidance for structural engineers in progressive collapse-prevention design. [ABSTRACT FROM AUTHOR]

A set of seismic analysis and design requirements are presented to improve seismic stability of steel two-tiered eccentrically braced frames (EBFs) with I-shaped link beams. The proposed requirements include strength, stability, and stiffness provisions for braces, intermediate beams, and columns. In particular, these requirements aim to make use of intermediate beams to limit out-of-plane deformation of diagonal braces, torsionally brace the link beam in the intermediate level using diagonal braces, utilize column stiffness and strength to brace the intermediate beam out-of-plane, estimate and account for in-plane bending demands of the columns due to uneven yielding of the links, and control inelastic link rotation. The proposed special analysis and design requirements for two-tiered steel EBFs prevent excessive out-of-plane deformation of the intermediate beam and columns, promote sequential yielding of link beams, and limit inelastic rotation of the link in the tier experiencing the largest lateral deformation. The proposed requirements are demonstrated for a case study two-tiered EBF. Nonlinear static and dynamic analyses are performed to evaluate the seismic response of the case study frame against the frame designed without special design provisions and to validate the proposed requirements. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluates gravity‐induced progressive collapse performance and damage mitigation strategies in modular steel buildings (MSBs) A typical three‐dimensional six‐story structure was modeled and analyzed using the finite element method, focusing on the instantaneous removal of a corner module. The study includes a parametric evaluation of the influence of beam moment capacity on progressive collapse and investigates the effect of using concrete as an infill for square hollow section columns. Additionally, the effectiveness of short K‐shaped braces in limiting gravity‐induced collapse was assessed. A response/damage index (DI) was proposed to quantify the overall structural response. The findings indicate that semirigid beam‐column connections outperform fully rigid connections. Both concrete‐filled columns and K‐shaped braces mitigate structural damage, with K‐shaped braces proving more effective in preventing collapse. Although increasing the beam moment‐resisting capacity reduced the DI, improvements were marginal beyond 50% of the fully rigid connection capacity. Higher beam moment capacities reduced local vertical displacement at the corner joint but led to undesirable lateral deformations. Reducing beam rigidity/capacity by 25% mitigated global structural deformations. The optimal beam moment capacity was identified as 75% of the total section capacity when using concrete‐filled columns. K‐shaped braces applied at the column midpoint entirely prevented progressive gravity‐induced collapse and no lateral deformations were observed in braced structures with fully rigid beam‐column connections, unlike unbraced structures. Concrete‐filled columns offer a cost‐effective solution for preliminary production of MSBs, while K‐shaped braces are suitable for retrofitting existing buildings. Further research is necessary to address other parameters influencing the mitigation of progressive collapse in MSBs. [ABSTRACT FROM AUTHOR]

This study investigates the seismic behavior of moment-resistant composite frames with concrete-filled steel tube (CFT) columns and composite steel beams under multiple earthquakes, considering soil–structure interaction (SSI) effects. Nonlinear time history analyses were performed on 2-, 4-, and 6-storey frames under five real seismic sequences and various soil conditions. The key response parameters included interstorey drift ratios, floor displacements, accelerations, and residual deformations. The results indicate that consecutive ground motions generally increase displacement demands and residual deformations compared to single-event scenarios. Incorporating SSI typically reduces drift ratios and accelerations but increases periods and displacements. Contrary to conventional assumptions, taller buildings exhibited lower maximum interstorey drift ratios, with the second storey consistently experiencing the highest drift across all building heights. Peak floor accelerations varied with building height; low-rise structures showed higher accelerations from earthquake sequences, while mid-rise buildings experienced higher accelerations from single events. These findings challenge traditional assumptions in seismic engineering and underscore the importance of considering multiple earthquake scenarios, building-specific factors, and SSI effects in the seismic design of CFT–steel composite frames. The results suggest a need for revising current design approaches to better account for these complex interactions. [ABSTRACT FROM AUTHOR]

When hollow reinforced concrete (RC) columns are retrofitted with concrete filling, the hollow interior cannot always be accessed to treat the internal surface. Without this treatment, an optimal bond between the newly introduced concrete and the existing column cannot be established; as a result, the two parts do not behave as a single unit. This study conducted cyclic loading tests on three types of large RC column specimens: a hollow RC column, a hollow RC column with a solid section at the column base, and a hollow RC column retrofitted with concrete filling (lacking inner surface treatment). The aim of this study was to investigate the effectiveness of a concrete-filling retrofitting method for hollow RC columns when the filled and existing portions behave separately, assuming a situation in which the bond between the filled and existing portions cannot be strengthened. The results indicated that concrete-filling retrofitting can suppress the inward buckling of the internal longitudinal bars, thereby enhancing the flexural deformation capacity of hollow RC columns to some extent. However, this did not prevent the significant axial settlement and reduction in the lateral load capacity that occurred when the inner longitudinal bars buckled. This is because the filled portion cannot resist axial forces when the filled and existing portions behave separately. Additionally, it was suggested that retrofitting with concrete filling does not substantially improve the shear resistance of a hollow RC column when the filled section behaves separately from the existing section. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The L-shaped partially encased steel–concrete composite (PEC) stub column, composed of profile steel, concrete, and transverse links, tends to occupy less space than the rectangle-shaped PEC column when used as side or corner columns. In this study, an axial compression test involving three L-shaped PEC stub columns was conducted to investigate the influence of critical factors on axial compression performance. The test results indicated that the axial compression capacity can be effectively enhanced with an increase in material strength. Furthermore, finite element (FE) analysis was carried out with parameters such as material strength, steel thickness, transverse link spacing, transverse link diameter, transverse link distribution, and longitudinal rebar diameter. The results revealed that the primary failure modes of L-shaped PEC columns were concrete spalling and local buckling of the flange. Additionally, it was found that the increase in steel strength, steel thickness, and transverse link diameter, as well as the decrease in transverse link spacing, significantly improved the axial compression capacity and concrete confinement effect. However, an increase in concrete strength diminished the concrete confinement effect. Additionally, the accuracy of the axial compression capacity calculation methods in the Eurocode 4 and T/CECS719-2010 specifications for L-shaped PEC stub columns was verified. Finally, a calculation method based on the superposition principle incorporating the concrete confinement effect was proposed, and validated by comparing with experimental and FE results. Overall, this study could provide a theoretical basis for the engineering application of L-shaped PEC columns. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive three-dimensional finite element modeling and parametric analysis of composite beam-to-column joints in steel–timber composite structures. The investigation encompassed a variety of shear connector configurations, end plate designs, and bolt dimensions, aiming to elucidate their respective influences on the structural performance and behavior of these joints. Through meticulous numerical simulation, this research sought to enhance the understanding of the interactions and load transfer mechanisms within composite connections, thereby contributing to the optimization of design practices in the field of structural engineering. The load–displacement relationship for timber–steel composite joints subjected to monotonic loading was investigated using ABAQUS 6.14 software. This study systematically analyzed the effects of various parameters, including different configurations of shear connectors, end plate thicknesses, and bolt dimensions, on the overall performance of the joints. Through this comprehensive numerical analysis, the research aimed to provide deeper insights into the mechanical behavior and structural integrity of these composite connections under the applied loading conditions. A non-linear finite element model of timber was developed and verified with the results of the experiment in this study. The findings are discussed in detail, highlighting the intricate relationships between the selected parameters and their respective effects on the performance and overall stability of the composite connections. This thorough evaluation aimed to enhance the understanding of how these variables interact within the context of composite joint design and behavior. Finally, design recommendations for composite structures, such as the dimensions of the bolt, end plate thickness, and different sizes of shear connectors are provided. [ABSTRACT FROM AUTHOR]

As the bridge's structural component is directly subjected to vehicle loads, the stress performance of the bridge deck has a significant impact on the safety, durability, and driving comfort of the bridge. In order to improve the bending performance of the bridge deck in the negative moment zone, a new type of steel grating–UHPFRC composite bridge deck was proposed in this paper. Firstly, structural details and advantages of the new steel grating-UHPFRC composite bridge deck were introduced. Secondly, the finite element program ABAQUS was used to establish a refined solid finite element model of the new bridge deck. The mathematical program MATLAB (PYTHON) was also used to analyze the effects of the structural parameters on bending bearing capacity and put forward reasonable structural parameters of the new bridge deck, considering the technical and economic indexes. Thirdly, the simplified plasticity theory was applied to analyze the bending bearing capacity of the new bridge deck, and the corresponding formula for bending bearing capacity calculation was derived and verified by numerical model results. In addition, the cost–benefit analysis and environmental impact assessment of the new bridge deck were also conducted. The results show that the bending bearing capacity of the new bridge deck in the negative moment zone increases with the increase of the width of the bridge deck, the thickness of the wing plate, and the height of the web plate, with a trend of increasing and then decreasing when the horizontal inclination of the web plate decreases. The bridge deck width does not have a significant effect on improving the bearing capacity. The bearing capacity calculated by theoretical formulas is close to that calculated by numerical models and the maximum relative deviation is 9.1%. The new steel grating-UHPFRC composite bridge deck proposed in this paper is superior to conventional steel-UHPC composite bridge deck in terms of cost-benefit and environmental impact. [ABSTRACT FROM AUTHOR]

As an effective technology for the rapid treatment of soft-soil foundations, geosynthetic encased stone column (GESC) composite foundations are commonly used in various embankment engineerings, including those situated on sloped soft foundations. Nevertheless, there is still a scarcity of stability studies for sloped GESC composite foundations. Several 3D numerical models for sloped GESC composite foundations were established using an equivalent method. The influences of the area replacement ratio and the tensile strength of geosynthetic encasement on the stability were investigated. The results showed that the stability increased nonlinearly with the area replacement ratio, and there existed an optimal area replacement ratio (e.g., 24.56% in this study) to balance the safety and economic requirements. The stability increased linearly with the tensile strength of geosynthetic encasement at low tensile strength levels (lower than 105 kN/m in this study), and the impact was relatively limited compared with that of the area replacement ratio. In addition, the stability generally decreased nonlinearly as the foundation slope decreased, and high-angle (foundation slope close to 30°) sloped GESC composite foundations are recommended to be treated with multiple reinforcement techniques. The relationship between the minimum area replacement ratio and the foundation slope was further quantified by an exponential function, allowing for the determination of the area replacement ratio of various sloped GESC composite foundations and providing theoretical guidance for engineering practice. [ABSTRACT FROM AUTHOR]

The present study proposed novel prefabricated composite RC shear walls with a concrete-filled steel tube frame (CCRCSW-CFST) because of the superior seismic performance of shear walls incorporating CFSTs as boundary-restrained members. One cast-in-place reinforced concrete shear wall (RCSW) and seven CRCSW-CFSTs, each varying in axial compression ratios, concrete strengths, and shear span ratios, were designed for experimental analysis. Cyclic loading tests were performed on these specimens, yielding the following results: (1) Compared to reinforced concrete shear walls, CCRCSW-CFSTs demonstrated superior seismic performance, with 14.2% increased ductility and 47.5% greater energy dissipation capacity. (2) Elevating the axial compression ratio in CCRCSW-CFSTs resulted in increased yield strength, peak strength, and stiffness. Conversely, this adjustment also expedited the degradation of stiffness with displacement and decreased both ductility and ultimate deformation. (3) The peak displacement and ultimate displacement of CCRCSW-CFSTs were both increased with an increase in concrete strength. Increasing the axial compression ratio enhanced the initial stiffness of CCRCSW-CFSTs and mitigated the rate at which stiffness deteriorated with increasing displacement. (4) The stiffness, peak and ultimate displacements, peak and ultimate loads, and shear span ratio of CCRCSW-CFSTs were significantly reduced as the shear span ratio was increased. (5) The minor slip between the reinforced concrete panel of the precast slab and the encasing C-shaped steel contributed to an increase in early-stage energy dissipation of the CCRCSW-CFSTs. [ABSTRACT FROM AUTHOR]