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This paper is dedicated to the memory of Dr. Miklós Iványi, who instilled in the authors an appreciation for experimental investigations, which are foundational to understanding material and structural behavior. Timber-concrete composite structures are increasingly adopted for new buildings due to their favorable sustainability parameters and the increased availability of cross laminated timber. For larger spans, however, solid timber floors lead to higher timber volumes and the use of glulam beams may become necessary for a more efficient use of wood. This paper presents laboratory tests of glulam-concrete composite beams and is the first in a series of two papers on investigating the associated failure mechanisms. Three full-scale glulam-concrete beam specimens were studied. The glulam and concrete are monolithically interconnected using a continuous layer of adhesive. Shear reinforcement was added to the glulam beams to allow for failure mode control. Static load tests to failure were conducted along with acoustic emission monitoring to track the progression of the failure. The results indicate that the shear reinforcement of the glulam layer affects the load capacity of the composite beam through shifting the failure from a shear to a tension failure mode. Similar glulam-concrete beams can enable larger span applications for buildings and bridges while maintaining an attractive sustainability performance. [ABSTRACT FROM AUTHOR]

In order to foster a modern economic system and facilitate high-quality economic development, it is crucial to establish a conducive business environment. Undoubtedly, the evaluation of the business environment for enterprises constitutes a prominent area of research. Nevertheless, ensuring the authenticity and security of the raw data sources provided by participating enterprises poses a challenge, thereby compromising the accuracy of the evaluation. To tackle this issue, an enterprise composite blockchain construction method for business environment is proposed in this paper, which stores the raw data of enterprises by the means of hybrid on-chain and off-chain. Initially, the enhanced hash function SHA256 is introduced to encrypt the raw data of enterprises. The encrypted data is subsequently stored in an off-chain Level DB database, which is based on non-volatile memory. This approach effectively alleviates the burden on communication and storage. Secondly, a composite storage strategy on-chain is adopted: the key values from the Level DB are stored in the DAG-based Conflux public blockchain, while the enterprise state data is stored in the consortium blockchain, so as to provide trusted evidence of business environment evaluation data. Finally, it is demonstrated through a large number of experimental comparisons that the enterprise composite blockchain construction method proposed in this paper exhibits better read and write performance, lower storage efficiency and storage overhead, and outperforms both the before-improved Level DB database and existing blockchain storage models. [ABSTRACT FROM AUTHOR]

In order to design an optimal reinforcement of steel thin-walled beams with composite materials, it is worth analyzing two important, although often overlooked issues, which are the selection of the appropriate thickness of the adhesive layer and the effective anchoring length of the composite tape. This paper, which is part of a wider laboratory study devoted to the strengthening of thin-walled steel profiles, focuses on the second issue. The paper involves a description of laboratory four-point bending tests during which ten thin-walled steel beams made of a rectangular section with dimensions of 120 × 60 × 3 and a length of 3 m were tested. Two beams were taken as reference beams, and the other eight were reinforced using Sika CarboDur S512 carbon fiber composite tape, assuming four different effective anchorage lengths. The impact of the length of the anchoring of the composite tape on the value of the displacements and strains of the tested beams and on the value of the destructive load that caused tape detachment was analyzed. The following phase was numerical analyses carried out in the Abaqus program, which showed high consistency with the results of laboratory tests. In reference to the conducted tests, it was observed that the increase in the anchoring length of the composite tape has a slight impact on the change in the value of strains and displacements in the tested beams. Nevertheless, the increase in the effective anchorage length has a significant impact on the load value at which the composite tapes are detached from the surface of the steel thin-walled beam. [ABSTRACT FROM AUTHOR]

An experiment was conducted on a prestressed concrete (PC) composite girder bridge with steel truss webs to investigate its flexural performance. The mechanical characteristics and failure modes of a PC composite girder bridge with steel truss webs was clarified. Finite element (FE) analysis was carried out, and the influence of the girder height-to-span ratio and eccentric loading effect on the flexural performance of a composite beam bridge with a steel truss web was discussed. The method for calculating the cracking bending moment, the bending moment at the rebar yield stage, and the ultimate bending moment of a PC composite girder with steel truss webs was proposed. Key findings include that, in both the elastic and cracking elastic stages, the strain of the bottom and top conforms to the plane-section assumption. Throughout the loading process, there was no occurrence of joint failure or local buckling failure in the steel truss webs; the composite girder ultimately fails due to excessive deformation, indicating that the overall mechanical performance of the composite beam is good. The deflection and stress in the mid-span section decrease with an increasing height-to-span ratio, and there are significant impacts of eccentric loading on deflection and stress. Compared with the results of the FE analysis and test, the calculation methods of the cracking moment, reinforcement yield moment, and ultimate moment of PC composite girders with steel truss webs presented in this paper have a high accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a research program aimed towards developing a method of producing lightweight, porous geopolymer composites for the construction industry based on industrial wastes. A direct method involving the addition of chemicals is currently most commonly used to produce the porous mineral structure of a geopolymer matrix. This relies on a reaction in a highly alkaline environment of the geopolymer to produce a gas (usually hydrogen or oxygen) that forms vesicles and creates a network of pores. This paper demonstrates the feasibility of producing a slag-based geopolymer paste foamed with aluminum powder, taking into account different parameters of fresh paste production: the mixing duration, its speed and the timing of foaming agent addition. The foaming process of the fresh paste in terms of the volumetric changes and temperature development of the fresh paste during the curing of the material are observed. After hardening, the physical properties (density and porosity) as well as the mechanical parameters (compressive strength and work of damage) are determined for the nine manufactured foamed pastes. Image analysis software was used to assess the porosity distribution of the material across the cross-section of the samples. The results enabled the design of the mixing procedure to be adopted during the manufacture of such composites. [ABSTRACT FROM AUTHOR]

At present, the determination of tunnel parameters mainly rely on engineering experience and human judgment, which leads to the subjective decision of parameters and an increased construction risk. Machine learning algorithms could provide an objective theoretical basis for tunnel parameter decision making. However, due to the limitations of a machine learning model's performance and parameter selection methods, the prediction model had poor prediction results and low reliability for parameter research. To solve the above problems, based on a large number of construction parameters of a composite section subway in Shenzhen, this paper combined dimensionality reduction data with service analysis to optimize the selection process of shield tunneling parameters, and determined the total propulsion force, cutter head torque, cutter head speed, and advance rate as key tunneling parameters. Based on an LGBM algorithm and Bayesian optimization, the prediction model of key tunneling parameters of an earth pressure balance shield was established. The results showed that the average error of the LGBM model on the test set was 8.18%, the average error of the cutter head torque was 13.93%, the average error of the cutter head speed was 3.16%, and the average error of advance rate was 13.35%. Compared with the RF model, the prediction effect and the generalization on the test set were better. Therefore, an LGBM algorithm could be used as an effective prediction method for tunneling parameters in tunnel construction and provide guidance for the setting of tunneling parameters. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the influence of the modification of polypropylene (PP) fibers on the sorption capabilities of the fibers. The physical modification of the PP fibers was made with inorganic nanoadditives in the mass, with a view to improving the properties of silicate composites used in the construction industry. The compositions of the modified PP fibers using two different nanoadditives were based on previous work, as well as the work presented in this paper. The prepared modified PP fibers were compared with pure PP fibers, and their mechanical and thermomechanical properties were evaluated. Another task of this work was to evaluate and compare the sorption capabilities of these fibers without the preparation of concrete blocks. Therefore, the Washburn method was used. However, the obtained results led us to the conclusion that the given method points to the excellent transport properties of PP fibers if such properties are used to evaluate the sorption of the fibers. However, the sorption of the prepared modified fibers could be associated with the nanoadditives used, which have a higher water sorption capacity compared to pure PP fibers, and this could also ensure the higher adhesion of the modified PP fibers with inorganic additives to the cement matrix compared to the adhesion of the hydrophobic PP fibers. [ABSTRACT FROM AUTHOR]

The global shear capacity of steel–concrete composite downstand cellular beams with precast hollow-core units is an important calculation as it affects the span-to-depth ratios and the amount of material used, hence affecting the embodied CO2 calculation when designers are producing floor grids. This paper presents a reliable tool that can be used by designers to alter and optimise grip options during the preliminary design stages, without the need to run onerous calculations. The global shear capacity prediction formula is developed using five machine learning models. First, a finite element model database is developed. The influence of the opening diameter, web opening spacing, tee-section height, concrete topping thickness, interaction degree, and the number of shear studs above the web opening are investigated. Reliability analysis is conducted to assess the design method and propose new partial safety factors. The Catboost regressor algorithm presented better accuracy compared to the other algorithms. An equation to predict the shear capacity of composite cellular beams with hollow-core units is proposed using gene expression programming. In general, the partial safety factor for resistance, according to the reliability analysis, varied between 1.25 and 1.26. [ABSTRACT FROM AUTHOR]

The objective of this paper is to outline a method for the systematic analysis and calculation of the constrained torsional shear stress in corrugated steel web composite box girders. Initially, leveraging Umansky's secondary theory, the calculation formula for the constrained torsional shear stress within the composite girder is derived from the conditions of cross-sectional torque equilibrium and continuity in warping displacement. Subsequently, a torsion test is conducted using a scaled model of an actual girder. Finally, the constrained torsional shear stress of the corrugated steel web composite girder is examined based on theoretical analyses and the results of torsion testing. The influence of wing plate length and web thickness on the torsional shear stress of the composite girder is also investigated. The findings reveal a strong agreement between the experimental results obtained from model testing and the theoretical calculations. Notably, under torsional constraint, it is observed that the shear stress in the web is maximal and evenly distributed, followed by the bottom plate and then the top plate, with no discernible shear stress observed at the free end of the cantilever plate. Numerical analysis indicates that an increase in the relative width of the cantilever plate initially leads to an increase in shear stress for both the cantilever plate and roof plate, followed by a decrease until reaching a relative width value around 0.6, where the changes tend to stabilize. Moreover, an increase in web thickness results in a monotonic decrease in web shear stress. Additionally, the shear stress of the roof and bottom plate decreases initially before subsequently increasing. [ABSTRACT FROM AUTHOR]

The narrow-width steel box girder is an important type of steel–concrete composite bridge structure, which is usually composed of reinforced concrete wing plates, narrow steel boxes partially injected with concrete, and shear connectors that promote shear force transfer. The utilization of narrow-width steel box girders, augmented by partially filled concrete, embodies the synthesis of steel and concrete elements, fostering structural efficiency. Moreover, its attributes, including reduced structural weight, diminished vertical profile, enhanced load-bearing capacity, and augmented stiffness, have prompted its gradual integration into bridge engineering applications. In this study, the calculated values of shear strength under three current design codes were reviewed, and the shear failure phenomena and its determinants of narrow-width steel box–ultra-high-performance concrete (UHPC) composite beams under negative bending moment conditions were investigated, which were mainly determined by shear span ratio, concrete wing plate, UHPC steel fiber content, UHPC plate thickness, and transverse partition inside the box. Concurrently, this paper evaluates two innovative structural designs, including a double-narrow steel box girder and a three-narrow steel box girder. In addition, strategies to reduce crack formation under the negative bending moment of long-span continuous narrow and wide box girder abutments are discussed, and we show that this measure can effectively control the formation of cracks to support the negative bending moment zone. At the same time, the scope of the application of a narrow-width steel box girder composite bridge is reviewed, and the conclusion is that a narrow-width steel box girder is mainly used in small-radius flat-curved bridges or widened-ramp bridges with a span of 30 m or more in interworking areas and in the main line with a 60–100 m span in mountainous or urban areas. Finally, the research direction of the shear resistance of the UHPC–narrow steel box girder under negative bending moments is proposed. [ABSTRACT FROM AUTHOR]

In this study, the structural performance of a new type of lightweight composite cold-formed steel and timber (CFST) flooring system has been investigated by conducting four-point bending tests on 13 specimens. A bare cold-formed steel system without timber sheathing was also tested to provide a benchmark response to which the strength and stiffness of the composite system were compared. This paper presents key findings on the flooring system's structural behavior and performance parameters, such as ultimate bending capacity, load-deflection response, load-slip response, and failure modes, by categorizing 13 specimens into four subgroups based on shear connector types and spacings. In the proposed composite CFST flooring system, 45-mm thick structural plywood panels were connected to the 2.4-mm thick cold-formed steel C-section joist using self-drilling screws, coach screws, and nuts and bolts. The performance of different types of shear connectors on the composite action is experimentally investigated and compared with the theoretical plastic section. Furthermore, the load-carrying capacity, effective bending stiffness, and deflection of composite CFST beams were computed theoretically using elastic theory and compared to experimental results, which showed good agreement. [ABSTRACT FROM AUTHOR]

The mountain area is faced with complex coJdjtions sucn as vertical and horizontal valleys, complex geologd topography, Vmny earthquake fault zones, high seismic intensityfriBk ecologyBkcriangeable climate. The traditional concrete bridgee heavy weilrhigh consumption of sand and gravel materials, large structural dimensions of steel box composite bridges, high steel consumption, and poor overall horizontal performance of steel plate composite beams, which are not suitable for mountain construction conditions. Thejefore, based onthe construction environment and application requirements of highway bridges in mountainous areas, the structural scheme of steeHX-steel pete composite beam is put forward in this paper, and the design 50 m landaTa-span steel box-steel plate composite beam is studied. Jrfl®iesu[ts show that the steel box-steel plate composite beam structure scheme is adopted, which has excellent mechanical characteristics of steel box girder and k simple structure of steel plate girder. It has the mechanical characteristics of balancidtransverse force and excellent longitudinal force", so it is a reasonable choice for small radius curved beam bridge in a mountainous area, so it is a reasonable choice for small radius curved beam bridge in a mountainous area. The steel box-steel plate composite beam adopts the integrated technology of manufacture, transportation and installation, which can better meet the road transport conditions in the mountain area. The longitudinal assembly of the manufacturing unit as the installation unit can ensure the rapid and high-precision installation of the construction site, and the assembly construction of the bridge in the mountain area has been realized. The technical and economic comparison shows that the mechanical performance of steel box-steel plate composite beam is similar to that of steel box beam and obviously better than that of steel plate girder. The steel consumption and construction period of steel box- steel plate composite beam are similar to that of steel plate girder, and are significantly less than that of the steel box girder. Therefore, the steel box- steel plate composite beam is a good choice for mountain bridge construction. [ABSTRACT FROM AUTHOR]

In this paper, the flexural performance of the Engineering Cementitious Composite (ECC)-concrete composite beam hybrid reinforced by steel and Fiber Reinforced Polymer (FRP) bars is assessed using nonlinear finite element analysis. The concrete damage plasticity model is used to model the nonlinear behavior of ECC and concrete materials. A perfect bond is assumed at the interface surface between the ECC and concrete. The validity of the numerical model is established through comparison with a previously published experimental study (overall error of about 5.4%). Consequently, the developed model is utilized to consider the effect of hybrid (FRP/steel) tensile reinforcement ratio, thickness of the ECC layer, type of FRP bars, and compressive strength of concrete on the flexure performance. It was evident from the results that the ratio of hybrid (FRP/steel) tensile reinforcement should be carefully chosen to achieve an adequate balance between ductility and carrying load capacity. Additionally, the thickness of the ECC layer plays a crucial role in controlling the hybrid reinforcement's tensile ratio to prevent rapid failure following the yielding of steel rebars within the ECC layer. Furthermore, the type of FRP bars used in the hybrid reinforcement has influenced the flexural behavior of the composite beam. Conversely, increasing the compressive strength of the concrete has minimal impact on enhancing the mechanical characteristics of the beams, even when considering a change in the type of FRP bars. [ABSTRACT FROM AUTHOR]

A common problem of anisotropic materials is that the modulus of elasticity is not equal in tension and compression. Presently, research objects are mainly concentrated on beams with isotropic materials or laminated beams with orthotropic materials, and few are involved in composite sandwich beams with different moduli in tension and compression. Considering the shortcomings of the equivalent area method, we propose a developed theoretical analysis method for analyzing sandwich beams with different moduli in tension and compression based on the idea of layering. In this method, the sandwich beam is divided into four layers: upper panel, lower panel, tension zone of core, and compression zone of core. In addition, based on general weighted flexibility matrix material model and its simplified model, a finite element simulation model with high computational efficiency and good convergence is established. A comparison between the theoretical calculation results and the finite element results shows that the developed theoretical analysis method proposed in this paper has a higher accuracy than the equivalent area method, regardless of different types of loads or conditions with a large ratio of tensile to compressive elastic modulus. [ABSTRACT FROM AUTHOR]

The current European Standard (EN 1994-1-1: Eurocode 4) put forth a reduction factor for Solid Composite Beam (SCB) with Class 1 and 2 sections for the design moment of resistance for sagging bending. This paper presents the analytical study on the behavior of Cellular Composite Beam (CCB) and proposes the reduction factor for the ultimate moment capacity of CCB sections. A moment-curvature program based on the strain compatibility method has been developed and used to examine the behavior of CCB made of S355, S460, and hybrid strength steel sections with different geometries. The program involves elastoplastic analysis since it is crucial to explore how the cellularity of the composite sections increases their curvature ductility, flexural resistance, and material utilization under high strain. The developed program has been validated against FE results, available test data, and ACB+ software solutions. A parametric study has been carried out to determine the effect of steel grade, concrete grade, effective width and depth of the slab, and varying sizes of a web opening on CCB sections. The Eurocode 4 design guidelines were used to determine the bending resistance of CCB for S355, S460, and hybrid-strength steel sections. The parametric study showed that high-strength concrete with a wider effective slab and enhanced depth sections with the lowest web opening causes CCB sections to have a higher ultimate moment and ultimate curvature. Comparing the hybrid CCB section to the regular and high-strength sections also showcases a significant enhancement in ductility and moment capacity. [ABSTRACT FROM AUTHOR]

Welding residual stress will aggravate the fatigue cracking damage of the structure and have an essential impact on the structure's load-bearing capacity. The welding sequence will directly affect the size and distribution of welding residual stress. To this end, this paper establishes a thermal–mechanical sequential indirect-coupling finite-element analysis model, researches the residual stress of steel-plate composite girder bridges considering the welding sequence, and verifies the analysis results through field tests. Then, a three-span steel-plate composite continuous girder bridge was taken as the research object, and the residual stress of the stiffener welds in seven welding sequences was analyzed. On this basis, the equivalent peak-stress method is used to evaluate and predict the fatigue strength of the weld. The research results show that welding residual stresses change the multiaxial stress state of fatigue details. Although under the same external load cyclic stress, the difference in welding sequence directly leads to a significant difference in the equivalent peak stress of the stiffeners, and this difference results in different fatigue properties of the stiffeners. The research results can provide a basis for the welding process and fatigue analysis of stiffener welds in steel-plate composite girder bridges. [ABSTRACT FROM AUTHOR]

Featured Application: In this paper, a fast construction method for a composite girder cable-stayed bridge is proposed. The method is used on the Xiangsizhou Bridge, and it complies with all bridge rules while reducing the entire construction time of the bridge by 4 months. This paper presents a comprehensive study of the Xiangsizhou Bridge, a double-tower double-cable steel–concrete composite girder cable-stayed bridge located in Pingnan, Guangxi, China. A finite element model of the full-bridge spatial truss system was established using a dual main beam simulation of the steel–concrete composite girder. To obtain the initial reasonable bridge state, the minimum bending energy method was employed, followed by optimization of the state using the unknown load coefficient method to attain the final reasonable completion state. This paper proposes an innovative construction scheme for the erection of the main girders, which is designed to address the issue of excessive tensile stresses in the bridge deck slabs that can arise in conventional construction schemes. This scheme can save about 4 months of construction time and shorten the construction cycle of main beam erection by 60%. Furthermore, the study derived and verified a formula for the intermediate cable force during the construction process, which demonstrated its effectiveness. This study provides practical value for the design and construction of similar bridges. [ABSTRACT FROM AUTHOR]

Thermal conductivity is a fundamental material parameter involved in various infrastructure design guides around the world. This paper developed an innovative neural network (NN) aided homogenization approach for predicting the effective thermal conductivity of various composite construction materials. The 2-D meso-structures of dense graded asphalt mixture, porous asphalt mixture, and cement concrete were generated and divided into 2n × 2n square elements with specific thermal conductivity values. A two-layer feed-forward neural network with sigmoid hidden neurons and linear output neurons was built to predict the effective thermal conductivity of the 2 × 2 block. The Levenberg-Marquardt backpropagation algorithm was used to train the network. By repeatedly using the neural network, the effective thermal conductivities of 2-D meso-structures were calculated. The accuracy of the above NN aided homogenization approach was validated with experiment, and various factors affecting the effective thermal conductivity were analyzed. The analysis results show that the accuracy of the NN aided approach is acceptable with relative errors of 1.92~4.34% for the dense graded asphalt mixture, 1.10~6.85% for the porous asphalt mixture, and 1.13~3.14% for the cement concrete. The relative errors for all the materials are lower than 5% when the heterogeneous structures are divided into 512 × 512 elements. Ignoring the actual material meso-structures may lead to significant errors (134.01%) in predicting the effective thermal conductivity of materials with high heterogeneity such as porous asphalt mixture. While proper simplification is acceptable for dense construction composite materials. The effective thermal conductivity of composite cement-asphalt mixtures increases with higher saturation of grouted material. However, the improvement effect of the high-conductive cement paste on the composite cement-asphalt mixtures could be significantly reduced when the cement paste concentrates at the bottom of the mixture. Cracked aggregates and segregation of material components tend to decrease the effective thermal conductivity of construction materials. The NN aided homogenization approach presented in this paper is useful for selecting the effective thermal conductivity of construction materials. [ABSTRACT FROM AUTHOR]

Composite deck slab flooring system is gaining popularity since they allow for simpler, lightweight, and more cost-effective building construction technique. The main constituent materials of a composite slab are profiled deck steel sheet and concrete. Profiled steel sheet serves two purposes: it acts as a main reinforcing structural element as well as a permanent formwork during the construction phase. The efficiency of the composite slab mainly depends upon the shear interaction between concrete and steel decking sheet. This paper contributes to improving the horizontal shear strength of composite slab by utilizing basalt textile reinforced concrete (BTRC) topping. The current research is focused on examining the behavior of this shear bond action and improving its performance even without the shear connectors. Three types of concrete topping and four different shear spans (250 mm, 325 mm, 550 mm, and 625 mm) are the variables of the testing. Based on the load-displacement response, failure mechanisms, maximum strain recorded in concrete/steel, load-slip characteristics, steel-concrete shear bond resistance, and the structural performances of basalt textile-reinforced concrete (BTRC) composite slabs were compared with the conventional concrete (CC) composite slabs. BTRC composite slabs are found to be more ductile than the conventional concrete composite slab, with increased load-bearing and slip resisting capacity. Both the m- k and partial shear connection (PSC) approaches were used to calculate the horizontal shear strength of the composite floor. The m-k technique has proven to be more meticulous than the PSC method. [ABSTRACT FROM AUTHOR]

This research paper introduces a methodology to assess the robustness of the Global Innovation Index (GII), by comparing the rankings provided in it with those achieved using alternative data-driven methodologies such as data envelopment analysis (DEA) and principal component analysis (PCA). With it, the paper aims to reduce the level of subjectivity in the construction of composite indicators regarding weight generation and indicator aggregation. The paper relies on PCA as a weighting-aggregation scheme to reproduce the 21 sub-pillars of the GII before the application of DEA to calculate the relative efficiency score for every country. By using the PCA-DEA model, a final ranking is produced for all countries. The random forests (RF) classification is used examine the robustness of the new rank. The comparison between the new rank and that of the GII suggests that the countries positioned at the top or the bottom of the GII rank are less sensitive toward the modification than those in the middle of the GII, the rank of which is not robust against the modification of the construction method. The PCA-DEA model introduced in this paper provides policymakers with an effective tool to monitor the performance of national innovation policies from the perspective of their relative efficiency. Ultimately, the contribution made in this paper could be instrumental to enhance the effectiveness and the efficiency of the practice of innovation management at the national level. [ABSTRACT FROM AUTHOR]

Four different composite coupling beam-to-composite plate shear wall (CPSW/CF) connection details were developed and proposed. Six large-scale specimens representing the four connections were designed, fabricated, and tested. The connections were subassemblies of coupled composite plate shear walls/concrete filled (CC-PSW/CF) subjected to cyclic lateral loading. The coupling beams were designed to be flexure-critical with clear span-to-depth (Lb/d) ratios of 3.5 or 5.1. This paper presents the experimental program, capacities, and detailed behavioral observations of all six specimens. The effects of connection type and Lb/d ratio on the ultimate strength, stiffness, ductility, and failure modes are evaluated. Major limit states and events included yielding of the steel plates comprising the coupling beam, followed by local inelastic buckling, fracture initiation in the base metal (near the weld toes), and fracture propagation through the beam flange and web plates, leading to loss of flexural strength and failure. All the connections were able to develop and transfer the flexural capacity of the composite beam section. The composite coupling beams developed flexural capacities (10%–50%) greater than those calculated using the plastic stress distribution method. The underlying reasons for this overstrength are evaluated. The AISC flexural stiffness equation for filled composite sections could reasonably estimate the stiffness of the composite coupling beam sections. A fiber-based model of the cross-section was used to calculate the section moment–curvature response of the filled composite beam sections. The calculated flexural capacities were consistent with those calculated by the plastic stress distribution method but lower than the experimentally observed values. The flexural stiffness values were slightly higher than the experimental results. For more accurate comparisons with experimental results, a numerical model is needed to estimate the cyclic lateral load-deformation response while accounting for the effects of local buckling, low cycle fatigue, and fracture. [ABSTRACT FROM AUTHOR]

A cold-formed, thin-walled steel/fast-growing timber composite system has recently been presented for low-rise buildings. It aims to increase the use of fast-growing wood as a green building material in structures, thus contributing to the transformation of traditional buildings. This study proposed a composite I-beam combined with fast-growing radiata pine and cold-formed thin-walled U-shaped steel. A four-point bending test was used to measure the bending properties of steel–timber composite I-beams under various connection methods. Based on experimental results, this study examined the specimen's failure mechanism, mechanical properties, and strain development. In addition, a method for calculating flexural bearing capacity based on the superposition principle and transformed section method was suggested. It is evident from the results that fast-growing timber and cold-formed thin-walled steel can have significant composite effects. Different connecting methods significantly impact beams' failure mode, stiffness, and bearing capacity. Furthermore, the theoretical method for calculating the flexural bearing capacity of composite beams differs from the test value by less than 10%. This paper's research encourages the applications of fast-growing wood as light residential components, and it serves as a reference for the development, production, and engineering of steel–timber composite structural systems. [ABSTRACT FROM AUTHOR]

Steel–concrete composite girder rigid frame bridges with V-shaped piers are a new type of bridge structure. Based on the traditional composite continuous beam bridge, part or all of the vertical piers are changed into V-shaped piers. This special structure makes them have the mechanical characteristics of both composite continuous beams and V-shaped piers. In this paper, the finite element model of the first steel–concrete composite continuous beam V-pier rigid frame bridge in China is established by simulation software, the construction process of the bridge is simulated, and the stress and deflection of the bridge in each construction stage are studied. At the same time, the stress of the completed bridge model considering the construction stage is compared with that of the completed bridge model without considering the construction stage. It is found that the stress difference between the two concrete slabs is as high as 2.7 MPa. The results show that the stress state of the bridge is greatly affected by the construction process. This study can provide guidance for the design and construction of such bridges, which is of great significance. [ABSTRACT FROM AUTHOR]

Aerospace solar arrays serve as the primary means for spacecraft to collect energy. Flexible solar arrays have the advantages of a high deployment ratio, light weight, a large span, and high specific power. Currently, they are primarily used on space stations. Ultra-thin, multi-stepped variable-section flexible solar arrays are a novel design solution. Due to extremely low stiffness, flexible solar arrays exhibit nonlinear behavior such as large deformations under bending during the deployment process driven by external forces, which is the main topic of this paper. To quickly obtain the morphology of the flexible solar array after unfolding and improve design efficiency, this paper first transforms the unfolding morphology of the flexible solar array into a nonlinear large deflection problem of a fourth-order discontinuous variable-section composite beam and gives the equivalent methodology. Subsequently, an efficient nonlinear difference algorithm is proposed. A set of differential equations for large deflections of multi-stepped variable-section beams under complex loading conditions is derived. The finite difference method is employed to discretize this system, and four different categories of node processing methods are derived in detail. Newton's iterative technique is used to solve for the curvature of each point, and explicit formulas to calculate the point coordinates, strain, and stress are developed. Ground deployment experiments, numerical simulations of on-orbit deployment, and comparisons with benchmark examples are used to verify the validity of the ND algorithm. Finally, the morphological analysis of the on-orbit deployment of the flexible solar array is performed, and some design advice is given. [Display omitted] • This approach can be used in the analysis of various flexible spacecraft. • It is applied to a certain flexible solar array. • The on-orbit morphology can be calculated quickly, which facilitates the design. • It is clear, highly reliable, and can be easily generalized to complex problems. • Some design advice is given for flexible solar arrays. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed solution of fasteners made of corrugated steel sheet and shot nails can be used as the connector for steel–concrete composite floor beams. The sheet provides stay-in-place formwork for a monolithic reinforced concrete slab. Furthermore, the sheet in the shape of the dovetail caused the connection between the steel I-beam and the concrete slab. The connectors are easy to fabricate. Any special mounting equipment that requires high-current electrical power is not necessary. Because shot nails have very wide applications, nailing devices are available in almost every construction factory and on construction sites. The shape of a such cross-section of the metal sheet improves its stability during installation compared to a flat metal sheet. An additional advantage is the ability to easily suspend the finishing elements by using dedicated hangers fixed in the fold of sheet. The paper presents an analysis of the innovative connector for manufacturing a steel–concrete composite beam. The connector consists of a corrugated metal sheet in the shape of a dovetail and shot nails. The nails are shot through the sheet fold into the flange of the steel I-section. Experimental studies of push-out tests were carried out. The conducted tests proved that the proposed solution can be applied as the fastener for steel–concrete composite beams for the construction of ceilings in utility public buildings with small beam's span. Considering the criteria presented in the Eurocode 4 standard and the results of the experiments, it was proven that all analyzed types of fasteners are ductile. The connector made of sheet with a thickness of 1.00 mm and 2 nails is characterized by a breaking load of 30.83 kN. The load-bearing capacity of the fastener can be adjusted by changing the corrugated sheet thickness and changing the number of nails shot in the single fold of the sheet. [ABSTRACT FROM AUTHOR]

Sustainable composite structures in building construction are assembled using demountable structural elements that can be reused in the circular economy. The current research and development project, in cooperation with Budapest University of Technology and Economics and KÉSZ Group, bim.GROUP Ltd., Hungary, aims to design a novel demountable steel-concrete composite slab and frame system for buildings. The key component of this construction is the demountable shear connector. In the current research, novel bolted shear connectors with embedded bolts and threaded rods are developed and studied that can fit the applied technology of the industrial partner. One of the leading aspects of this connection is the consideration of bolt hole clearance, since it occurs initial slip and stiffness reduction of the composite beam. In the first phase of the research program, demountable and economical structural details were developed, which can reduce the stiffness reduction with the proper resistance and ductility features. To study the behavior of these shear connections, a push-out experimental program was designed and completed in March and April 2023. It is observed that novel shear connectors have a proper behavior with sufficient resistance and ductility, which is applicable according to the Eurocode 4 standard and fits the objectives of the research and development project. In the paper, the developed structural details and the push-out experimental program are presented with general results and statements besides a detailed evaluation of a specified specimen type. [ABSTRACT FROM AUTHOR]

The paper concerns the numerical modelling of a new slim-floor system with innovative steel–concrete composite beams called "hybrid beams". Hybrid beams consist of a high-strength TT inverted cross-section steel profile and a concrete core made of high-performance concrete and are jointed with prestressed hollow core slabs by infill concrete and tie reinforcement. Such systems are gaining popularity since they allow the integration of the main structural members within the ceiling depth, shorten the execution time, and reduce the use of concrete and steel. A three-dimensional finite element model is proposed with all parts of the system taken into account and detailed geometry reproduction. Advanced constitutive models are adopted for steel and concrete. Special attention is paid to the proper characterisation of interfaces. The new approach to calibration of damaged elastic traction–separation constitutive model for cohesive elements is applied to concrete-to-concrete contact zones. The model is validated with outcomes of experimental field tests and analytical calculations. A satisfactory agreement between different assessment methods is obtained. The model can be used in the development phase of a new construction system, for instance, to plan further experimental campaigns or to calibrate simplified design formulas. [ABSTRACT FROM AUTHOR]

Research on evaluating highway bridge performance through vehicle-bridge interaction (VBI) analysis has made significant advancements. However, when assessing driving comfort, using vehicle acceleration instead of human acceleration poses challenges in accurately representing comfort. First, the paper proposes a finite element analysis method for human-vehicle-bridge spatial interactions (HVBSIs). Then, the importance of wheel path roughness difference is explored when assessing driving comfort. Furthermore, a new method for evaluating driving comfort that includes human and vehicle vibration responses has been proposed, and a simulation example of the steel-concrete composite beam bridge (SCCBB) is used to verify the effectiveness of the proposed method. The results demonstrate that the HVBSI analysis method effectively simulates the interconnected vibrations of the human body, the spatial vehicle model, and the three-dimensional (3D) bridge model. Differences in wheel path roughness significantly impact the roll vehicle vibration responses, which are crucial in driving comfort analysis. The driver's body vibration response is essential for evaluating driving comfort, and its inclusion leads to increased comfort indices values. In comparison to traditional methods, the overall vibration total value (OVTV) increases by a maximum of 109.04%, and the level of weighted vibration ( L e q ) increases by a maximum of 6.74%. This leads to an upgrade from grade IV to grade V in terms of comfort level, indicating a reduced comfort. [ABSTRACT FROM AUTHOR]

High-temperature (HT) geothermal wells can provide green power 24 hours a day, 7 days a week. Under harsh environmental and operational conditions, the long-term durability requirements of such wells require special cementitious composites for well construction. This paper reports a comprehensive assessment of geothermal cement composites in cyclic pressure function laboratory tests and field exposures in an HT geothermal well (300–350 °C), as well as a numerical model to complement the experimental results. Performances of calcium–aluminate cement (CAC)-based composites and calcium-free cement were compared against the reference ordinary Portland cement (OPC)/silica blend. The stability and degradation of the tested materials were characterized by crystalline composition, thermo-gravimetric and elemental analyses, morphological studies, water-fillable porosity, and mechanical property measurements. All CAC-based formulations outperformed the reference blend both in the function and exposure tests. The reference OPC/silica lost its mechanical properties during the 9-month well exposure through extensive HT carbonation, while the properties of the CAC-based blends improved over that period. The Modified Cam-Clay (MCC) plasticity parameters of several HT cement formulations were extracted from triaxial and Brazilian tests and verified against the experimental results of function cyclic tests. These parameters can be used in well integrity models to predict the field-scale behavior of the cement sheath under geothermal well conditions. [ABSTRACT FROM AUTHOR]

Low computational efficiency and non-linearity behaviour make the simulation of the overall building structure problematic to attain with a single dynamic or static method. Thus, this paper uses a plastic deformation (PD) method based on concrete plasticity theory (CPT) for comparative analysis of multi-storey reinforcement cement concrete (RCC) and composite buildings under common and rare earthquake loads. For this purpose, a 15-storey tall building was selected for analysis using ABAQUS software. At first, a possible building model was created and then plastic deformation analysis was performed using the new PD method under both common and rare earthquakes. After that, a nonlinear time history analysis was conducted, and the results of plastic strain distribution, lateral displacement, peak acceleration, storey stiffness, shear force, storey drift, normalised shear, and top deflection of the RCC and composite buildings were studied deeply. The fundamental time period of the RCC model was found to be 5.2 s while the fundamental time period of the composite model was 6 s. Under common and rare earthquake leads, the peak acceleration of the RCC building was 19% and 22% higher than composite buildings, respectively. Under common and rare seismic loads, the top deflections of the composite building were 33% and 36% higher than those of RCC buildings, respectively. In the case of the RCC building, it was found in this study that higher peak acceleration (PA) of the ground motion led to higher storey top displacement, storey drift, shear force and top deflection under both ground motions. Numerical results suggested that the use of composite structure is more durable than RCC structure. It was also concluded that the PD method could also be effectively used for the analysis of RCC and composite buildings under dynamic loads. [ABSTRACT FROM AUTHOR]

Due to the shear strain in the plane of the slab, the parts of the slab remote from the steel beam lag behind the part of the slab located in its proximity. This shear lag effect causes a non-uniform stress distribution across the width of the slab. As a result, several standards have introduced the concept of an effective flange width to simplify the analysis of stress distribution across the width of composite beams. Both the computed ultimate moment and serviceability limit states are directly impacted by the effective width. The effect of using a large number of contact points as shear connectors on the effective width of a steel beam flange has not been investigated. A three-dimensional finite element analysis is carried out in this paper. The ABAQUS software (version 6.14) is used for this purpose, where several variables are considered, including the surface area connecting the steel beam and concrete slab, the transverse space, and the number of shear connectors. It was discovered that the number of shear connectors on the steel beam flange has a major impact on the effective width. The many connectors work together to provide a shear surface that improves the effective width by lowering the value of the shear lag. [ABSTRACT FROM AUTHOR]

Laminated bamboo (LB) is considered a promising environmentally friendly material due to its notable strength and advantageous lightweight properties, making it suitable for use in construction applications. LB I-beams are a prevalent component in bamboo structures due to their ability to fully utilize their material properties and enhance efficiency when compared to beams with rectangular solid sections, while the characteristics of connections should be further studied. This paper presents an experimental investigation of the flexural behavior of I-shaped LB beams that are connected using self-tapping screws and LB dowels. Compared with glued beams of the same size, the findings of the study reveal that the primary failure modes observed in those two types of components were characterized by the separation of the component and web tensile fracture. The screw beam and dowel beam exhibited a reduced ultimate capacity of 43.54% and 30.03%, respectively, compared to the glued beam. Additionally, the ultimate deflections of the screw beam and dowel beam were 34.38% and 50.36% larger than those of the glued beam, respectively. These variations in performance can be attributed to the early breakdown of connectors. Based on design codes, it can be observed that the serviceability limits were in close proximity, whereas the ultimate strains of the top and bottom flanges were significantly lower than the ultimate stresses experienced under uniaxial loading conditions. As a result of the slip and early failure of connectors, the effective bending stiffness estimated by the Gamma method achieved better agreements before elastic proportional limit. Therefore, in future investigations, it would be beneficial to enhance the connector and fortify the flange as a means of enhancing the bending characteristics of an I-shaped beam. [ABSTRACT FROM AUTHOR]

The embedded shear connector with flanges (ESCF) exhibits excellent shear performance in the steel–concrete composite beam. The ESCF consists of embedded corrugated steel web as the shear connector and shape-matched flanges for construction convenience. However, previous research showed that the steel flange of the ESCF was prone to local buckling when subjected to shear force, resulting in insufficient shear strength of the connector. In this paper, head studs were adopted to reinforce the ESCF at the flange with a large width-to-thickness ratio. Nine stud-reinforced embedded shear connectors with flanges (SR-ESCF) were manufactured to conduct the push-out test to investigate the shear performance of SR-ESCF. The effects of the reinforcing studs, thickness of the web, width-to-thickness ratio of the flange, embedding depth of the web, and diameter of the combined rebar on shear strength of the SR-ESCF were revealed and discussed thoroughly. The push-out test results showed that the head studs significantly improved the initial stiffness and load-bearing capacity of the ESCF, which were increased by 17% and 15%, respectively. Moreover, the head studs prevented local buckling of the steel flange. The shear strength of the specimens was greatly influenced by the embedding depth of the web, the width-to-thickness ratio of the flange as well as the reinforcing studs. However, the diameter of the combined rebar and thickness of the web had negligible effects on the shear capacity of the SR-ESCF. According to the test results, the nonlinear finite element model (FEM) and the shear capacity of SR-ESCF prediction formula were created and verified. Furthermore, the layout of the reinforcing studs welded on the flange of the SR-ESCF was optimized by the validated FEM, which indicated that the shear-bearing capacity of the SR-ESCF could be significantly increased by adding studs on the steel flange near the original studs. This research will be of great significance to the design and implementation of the steel–concrete composite beam bridge with corrugated steel web. [ABSTRACT FROM AUTHOR]

This paper investigates the bending resistance of an innovative lightweight composite floor system, LWT-FLOOR. The system consists of built-up cold-formed steel elements that are spot-welded and connected to the concrete slab using demountable shear connectors. As the system under investigation is new, the existing standards do not provide guidelines for calculating its bending resistance. This paper gives an overview of different analytical approaches and a comparison of calculated results using bending capacities from the numerical parametric study. Within the numerical parametric study, the influence of the height of the steel beam, the type and degree of shear connection, the connection between the steel elements, and the thickness of the corrugated web used for the bending capacity are investigated. Numerical results for the full shear connections resulted in lower bending capacities than the analytically calculated plastic bending resistances. However, numerically obtained bending capacities for partial shear connections were found to exceed the calculated characteristic non-linear bending resistances and bending resistances for partial shear connections. The obtained results will comprise the basis for further experimental tests, which will support the search for an optimal analytical approach for the bending resistance of the proposed composite system. [ABSTRACT FROM AUTHOR]

In civil engineering, carbon fibre-reinforced polymer (CFRP) composites have emerged as a promising alternative to conventional materials. The article provides a comprehensive overview of the application of CFRP composites in various building structural elements and their characteristics and properties, such as their fatigue and corrosion resistance, stiffness and high strength, and incorporation of temperature factors. The advantages and disadvantages of CFRP composites and the current trends and prospects for CFRP composites in the construction sector are discussed. In addition, the article compares various studies on CFRP composites to shed light on their performance and potential limitations. This paper aims to provide useful information to researchers and practitioners interested in using CFRP composites in civil engineering applications. In addition, the article discusses emerging materials in CFRP, such as nanostructured carbon fibres, hybrid fibre reinforcement, and self-sensing CFRP. Additionally, the paper outlines how CFRP composites promote sustainability by increasing structural durability and longevity. [ABSTRACT FROM AUTHOR]

This paper proposes a Principal Component Analysis (PCA)-based method to construct composite indices to rapidly assess power system transient stability. By assigning appropriate weights to a few selected sub-indicators, a composite index can be constructed to guarantee a better coverage of worst-case stability scenarios of the power system. This paper provides an automatic method to construct a composite index with four sub-indicators calculated by the integral of acceleration, speed deviation and rotor angle of generators over a certain integration period using PCA. The effectiveness of the sub-indicators is validated first, followed by a comprehensive example of process of composite index construction, and the assessment of the influence of the effect of integration period on the performance of the composite index. High accuracy of classification has been demonstrated using composite index with appropriate settings of the integration periods of the sub-indicators. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyze the nonlinear vibration of composite beams and the stability of the solution by using the reduced-order model and the incremental harmonic balance (IHB) method. Timoshenko beam theory is used to indicate the displacement of the beam element. Each nodal point has three degrees of freedom. Simplified homogenized beam theory is used to calculate the equivalent moduli of each ply of the composite beam. Element matrices are created using the weak form quadrature element method, and the equation of motion at the element is created using Lagrange's equation. A system matrix is created using the element matrix assemble rule of the finite element method. In order to reduce the calculation time, a reduced-order model is used. The nonlinear forced vibration equation is solved using the IHB method. The results calculated using the non-reduced-order model and the reduced-order model are compared, and the results are very close. Based on this, the reduced-order model is used to analyze the nonlinear vibrations of composite beams at the first resonance point, and stability tests are conducted for the calculated solutions using the multivariable Floquet theory. [ABSTRACT FROM AUTHOR]

To maximize the capabilities of nano- and micro-class satellites, which are limited by their size, weight, and power, advancements in deployable mechanisms with a high deployable surface area to packaging volume ratio are necessary. Without progress in understanding the mechanics of high-strain materials and structures, the development of compact deployable mechanisms for this class of satellites would be difficult. This paper presents fabrication, experimental testing, and progressive failure modeling to study the deformation of an ultra-thin composite beam. The research study examines the deformation modes of a post-deployed boom under repetitive pure bending loads using a four-point bending setup and bending collapse failure under eccentric buckling. The material and fabrication challenges for ultra-thin, high-stiffness (UTHS) composite boom are discussed in detail. The continuum damage mechanics (CDM) model for the beam is calibrated using experimental coupon testing and was used for a finite element explicit analysis of the boom. It is shown that UTHS can sustain a bending radius of 14 mm without significant fiber and matrix damage. The finite element model accurately predicts the localized transverse fiber damage under eccentric buckling and buckling stiffness of 15.6 N/mm. The results of the bending simulation were found to closely match the experimental results, indicating that the simulation accurately shows deformation stages and predicts damage to the material. The findings of this research provide a better understanding of the structure characteristics with the progressive damage model of the UTHS boom, which can be used for designing a complex deployable payload for nano-micro-class satellites. [ABSTRACT FROM AUTHOR]

Fatigue in steel–concrete composite beams can result from cyclic loading, causing stress fluctuations that may lead to cumulative damage and eventual failure over an extended period. In this paper, the experimental findings from fatigue loading tests on composite beams with various arrangements are presented. Fatigue tests were performed up to 1,000,000 cycles using four-point loading, encompassing various ranges of shear stress at a consistent amplitude. Additionally, the effects of external post-tensioning and the strength of the shear connection were investigated. Static tests were run until failure to assess the enduring strength of the specimens subjected to fatigue. The cyclic mid-span deflections, slippages, and strains were measured during the testing. Based on the experimental findings, it was found that the damage region that the shear studs caused in the concrete slab, which resulted in a reduction in stiffness within the shear connection, grew as the loading cycles increased, leading to an increase in residual deflections and plastic slippages. Controlling the longitudinal fatigue cracks in the concrete slab was largely dependent on the strength of the shear connection between the steel beams and concrete slabs. Moreover, the applied fatigue loading range affected the propagation and distribution of fatigue cracks in the concrete slab. The strains in different parts of the composite specimens were significantly reduced by applying the external post-tensioning. With no signs of distress at the anchors, the tendons displayed excellent fatigue performance. [ABSTRACT FROM AUTHOR]

It is known that steel–concrete composite systems are very efficient. However, such steel–concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be reduced. This paper, therefore, presents a numerical study of an innovative solution for a composite floor system consisting of built-up cold-formed sections and concrete slabs. Through parametric numerical analysis, parameters such as the diameter and quality of bolts, the concrete class, the type of concrete slab, and the steel quality of sections and bolts were varied. The numerical analysis results show that the system with a solid concrete slab had a higher shear resistance and ductility than the system with a concrete slab made with profiled sheeting and showed different failure modes. The presented results form the basis for push-out tests for the proposed shear connection types. [ABSTRACT FROM AUTHOR]

This paper investigates the progressive collapse behavior of composite beam-column connection subassembly under column removal scenarios. An analytical model is proposed based on the rigid-plastic assumptions, in which the plastic hinges and inelastic rotations are assumed to develop concentratedly at only the connection interfaces, whereas the remaining parts are rigid except for the axial shortening/lengthening deformation when subjected to compressive/tensile forces. The component-based joint model proposed by Eurocodes is utilized to approximate the axial and plastic moment resistances of composite beam-column connections. The method to determine the force-displacement relationship of each connection component is presented in detail, particularly for the concrete slab and profiled steel decking where the actual nonuniform stress distributions along the slab thickness and width are carefully considered. By comparing with the published test results of composite joints under respective hogging and sagging moment, the proposed rigid-plastic model is capable of predicting the progressive collapse behavior of composite beam-column connection subassembly with reasonable accuracy. Based on the verified model, a parametric study is conducted with focus on the effect of lateral restraint stiffness on the collapse-resisting capacity of composite beam-column connection subassembly under column removal scenarios. [ABSTRACT FROM AUTHOR]

The utilization and incorporation of glass fiber-reinforced plastics (GFRP) in structural applications and architectural constructions are progressively gaining prominence. Therefore, this paper experimentally and numerically investigates the use of GFRP I-beams in conjunction with concrete slabs to form composite beams. The experimental design incorporated 2600 mm long GFRP I-beams which were connected compositely to concrete slabs with a 500 mm width and 80 mm thickness. The concrete slabs are categorized into two groups: concrete slabs cast using normal-strength concrete (NSC), and concrete slabs prepared using high-strength concrete (HSC). Various parameters like the type of concrete (normal and high-strength concrete), type of stiffeners bonded to the composite section (bolt–epoxy or bolt only), and inclusion of corrugated metal sheets were investigated. To obtain the full shear connection between the GFRP I-sections and concrete slabs, two rows of shear connectors in the form of bolts were utilized. These shear connectors were erected to the top flange of the GFRP I-sections to compositely connect between the GFRP I-beams and the concrete slabs as well as the corrugated metal sheets. The strengthening of the shear webs of GFRP I-beams with GFRP T-section stiffeners resulted in an enhancement in the flexural and shear strength. The failure loads in the case of the bolt–epoxy connection for the stiffeners were 8.2% and 10.0% higher than those in the case of bolt only when the concrete compressive strengths were 20.1 MPa and 52.3 MPa, respectively. Moreover, the effect of the concrete compressive strength was vital where the failure loads increased by 79.9% and 77.1% when HSC was used instead of NSC for the cases of bolt–epoxy and bolt only, respectively. The epoxy adhesive used in conjunction with mechanical connectors, specifically bolts, resulted in sufficient composite action and delayed shear failure within the web of the GFRP beam. For the specimens with bolt–epoxy connection, strain levels in the concrete slabs were consistently higher than in the other specimens with bolts alone at the same loading level. The concrete slabs integrated with HSC registered strain levels that were 20.0% and 21.8% greater for bolt–epoxy and bolt-only connections, respectively, when compared to those using normal-strength concrete (NSC). This discrepancy can likely be credited to the enhanced composite interaction between the concrete slabs and the GFRP I-beams. In addition, ABAQUS software (version 6.2) was used to develop FE models to analyze the tested composite beams and provide a parametric study using the verified models. [ABSTRACT FROM AUTHOR]

The paper presents a beam theory for composite girders consisting of two beams joined together with an adhesive layer. The height of the bottom beam is considered variable. The governing equations are suitable for formulation of a shape optimization problem in terms of control theory. The use of Pontryagin's maximum principle enables finding an optimal solution satisfying necessary optimality conditions. The presented optimization approach allows for including issues which cannot be accounted for by commercial topology optimization software. The introduced theory provides an estimated solution, which is then validated by an analysis of a 3D finite element model. [ABSTRACT FROM AUTHOR]

The flexural performance of steel and concrete composite beams can be further enhanced by utilizing advanced construction materials such as ultra-high performance fiber-reinforced concrete (UHPFRC) and high-strength steel. In this paper, the concept of critical elastic moment resistance is proposed and the equation for its estimation is derived. It was found that the high yield strength of steel calls for a narrow UHPFRC top layer to reach the critical state, whereas this ideal condition is not realistic for composite beams with normal-strength steel and UHPFRC. Small-scale composite beams composed of both high-strength and low-strength steel materials were tested under four-point bending to verify the critical state and performance of different types of connectors. The headed studs and plate connectors were first tested through small-scale push-out tests and then implemented in the composite beam with different spacing. The connection utilizing headed studs with 150 mm spacing performed the best among the three tested specimens in helping reach the critical elastic moment resistance. Finite element analyses of the composite beam were performed based on the estimated material properties under axial and biaxial stress conditions and the results align with the experiment results. [ABSTRACT FROM AUTHOR]

This paper optimizes the design of a novel large-span cable-supported steel–concrete composite floor system in a simply supported single-span, single-strut configuration, aiming for cost-effective solutions and minimal steel consumption. The optimization considers various cross-sectional dimensions, adhering to building standards and engineering practices, and is based on a non-linear programming (NLP) algorithm. Parameters of live loads ranging from 2 to 10 kN/m2 and spans from 20 to 100 m are considered. The optimization results show that cable-supported composite floors with a single strut exhibit robust economic feasibility for spans of less than 80 m and live loads under 8 kN/m2. Compared to conventional composite floors with welded I-beams, the cable-supported system offers more cost-effective cross-sections and reduces steel consumption. The savings in economically equivalent steel consumption range from 20% to 60%. Discussion on the area ratio of cables to steel beam in the optimal cross-section reveals that the secondary load-bearing system (i.e., bending of the main beam with an effective span length of L/2) may require more steel in cases of ultra-large spans. Therefore, the economical efficiency of cable-supported composite beams with multiple struts and smaller effective span lengths warrants further exploration in future studies. [ABSTRACT FROM AUTHOR]

In this paper, the interactions between the transverse loads and the electrical field quantities are investigated based on the nonlinear constitutive relation. By considering a composite beam consisting of a piezoelectric semiconductor and elastic layers, the nonlinear model is established based on the phenomenological theory and Euler's beam theory. Furthermore, an iteration procedure based on the differential quadrature method (DQM) is developed to solve the nonlinear governing equations. Before analysis, the convergence and correctness are surveyed. It is found that the convergence of the proposed iteration is fast. Then, the transverse pressure induced electrical field quantities are investigated in detail. From the calculated results, it can be found that the consideration of nonlinear constitutive relation is necessary for a beam undergoing a large load. Compared with the linear results, the consideration of the nonlinear constitutive relation breaks the symmetry for the electric potential, the electric field, and the perturbation carrier density, and has little influence on the electric displacement. Furthermore, the non-uniform pressures are considered. The results show that the distributions of the electric field quantities are sensitively altered. It indicates that the electrical properties can be manipulated with the design of different transverse loads. The conclusions in this paper could be the guidance on designing and manufacturing electronic devices accurately. [ABSTRACT FROM AUTHOR]

The U-shaped steel-concrete composite beam (USCB) has the superiority of good stiffness, high load-bearing capacity, and good fire performance. In this paper, the numerical simulation and theoretical derivation were conducted for the thermal transfer and fire-resistant research of USCBs. Four fire tests on USCB specimens under the current standard temperature rising curve were used to validate the fire design method. The temperature field models and fire-resistance models were set up to research heat-transfer and structural mechanisms, and the analysis showed that the fire condition of different concrete sections was different in the USCBs, and the internal force redistribution happened in the composite beam. Then, the parametric analysis shows that the load ratio, the diameter of fire-resistance reinforcement, and the thickness of the fire protection layer have significant effects on the fire performance. The temperature calculation methods of U-shaped steel, different concrete sections, and fire-resistant reinforcement are proposed based on the conducted research. Moreover, a flexural bearing capacity calculation method for the USCB under the standard temperature rise curve is proposed allowing for the influence of material strength reduction under high temperatures, which can also be used to calculate the fire resistance. Finally, the calculation tables for the fire protection layer thickness and the corresponding design method are proposed based on the delaying temperature mechanism. [ABSTRACT FROM AUTHOR]

This paper reports comparative studies of the fire behavior of partially encased composite beams (PECBs), slim-floor composite beams (SFCBs), and fully encased composite beams (FECBs) using validated numerical models. The effects of parameters such as load ratio, concrete slab width, concrete and steel strength, and section dimension of the steel beam were considered. The findings indicate that the mechanical behavior of PECBs, SFCBs, and FECBs undergoes four distinct phases when exposed to elevated temperature, namely an elastic phase, an elastic-plastic phase, a plastic yielding phase, and a plastic instability phase. The failure criterion proposed by ISO 834 is more appropriate for predicting the failure of PECBs, SFCBs, and FECBs than those proposed by BS 476-20 and ASTM E119-18. The failures of SFCBs and FECBs under fire were both demonstrated to be the crushing of concrete and yielding of steel beam, whereas when PECBs fail, the steel beam yields, but whether the concrete of PECBs is crushed is determined by the load ratio. At elevated temperatures, the web of PECBs and SFCBs yields earlier than the lower flange. Additionally, the lower flange of PECBs and SFCBs has the potential to convert from a state of tension to compression. Increasing the web height and thickness or decreasing the load ratio can prolong the duration of plastic yielding phases and plastic instability phases, thus improving the fire resistance of PECBs, SFCBs, and FECBs. In addition, the fire resistance of PECBs, SFCBs, and FECBs are barely affected by the concrete slab width, steel strength, and shear connection degree. Although PECBs and SFCBs both have good fire resistance, additional measures such as welding the reinforcement to the web or applying a fire protection layer to the lower flange are required to meet 2-h fire resistance at a load ratio of 0.4. Moreover, FECBs can achieve 2-h fire resistance even if the load ratio is up to 0.8. [ABSTRACT FROM AUTHOR]

Glass Fiber Reinforced Polymer (GFRP) beams have gained attention due to their promising mechanical properties and potential for structural applications. Combining GFRP core and encasing materials creates a composite beam with superior mechanical properties. This paper describes the testing encased GFRP beams as composite Reinforced Concrete (RC) beams under low-velocity impact load. Theoretical analysis was used with practical results to simulate the tested beams' behavior and predict the generated energies during the impact loading. The impact response was investigated using repeated drops of 42.5 kg falling mass from various heights. An analysis was performed using accelerometer readings to calculate the generalized inertial load. The integrated acceleration record and the measured hammer load vs. time data were utilized to determine the generalized bending load and fracture energy. Four forms of energy were calculated at the maximum load. The total energy was calculated and divided into two parts: The first part was gained by the beam's rotational kinetic energy, the bending energy in the specimen, and the elastic strain energy. The second part was the hammer's kinetic energy before striking the beam. The analytical results showed that the bending energy was less than its rotational kinetic energy for the encased GFRP beams and the reference specimens. In contrast, the encased steel beams had high bending energy due to the higher impact load and deflection. Strain energy recorded lower energy values for all specimens with higher bending energy. There is a good agreement between the tested and the calculated inertial and bending force for all beams. The ratio of inertia force to the total impact load for the encased GFRP and encased steel beams to the reference beam is about 9% and 5%, respectively. [ABSTRACT FROM AUTHOR]