Search

The engineering of the surface morphology and the structure of the thin film is one of the essential technological assets for regulating the physical properties and functionalities of thin film-based devices. This study presents an easy and handy approach to tailor the surface structure of epitaxial thin films utilizing low-energy ion beam. Here, we investigate the evolution of the surface structure and magnetic anisotropy (MA) in epitaxial Fe/MgO (001) model systems subjected to multiple cycles of ion beam erosion (IBE) after thin film growth. The growth of Fe film occurs in the form of three–dimensional islands and exhibits intrinsic biaxial MA. Following a few cycles of IBE, an induced uniaxial magnetic anisotropy leads to a split in the hysteresis loop, and the film displays almost uniaxial magnetic switching behavior. More distinctly, we present a clear and conclusive evidence of (2 × 2) reconstruction of the Fe surface due to the atomic rearrangement by IBE. Furthermore, 57Fe isotope sensitive nuclear resonance scattering measurement provides insight into the depth-resolved magnetic information due to the modified surface topography. We also demonstrate that thermal annealing can reversibly tune the surface reconstruction and induced UMA. The feasibility of the IBE technique by adequately selecting IBE parameters for surface structure modification has been highlighted apart from conventional tailoring of the morphology for the tuning of UMA and introduces a new dimension to our understanding of self-assembled surface morphology evolution by IBE. [ABSTRACT FROM AUTHOR]

Segmentally assembled bridges are increasingly finding engineering applications in recent years due to their unique advantages, especially as urban viaducts. Vehicle loads are one of the most important variable loads acting on bridge structures. Accordingly, the influence of overloaded vehicles on existing assembled bridge structures is an urgent concern at present. This paper establishes the finite element model of the segmentally assembled bridge based on ABAQUS software and analyzes the influence of vehicle overload on an assembled girder bridge structure. First, a finite element model corresponding to the target bridge is established based on ABAQUS software, and the load is controlled to simulate vehicle movement in each area of the traveling zone at different times. Second, the key cross-sections of segmental girder bridges are monitored in real time based on the force characteristics of continuous girder bridges, and they are compared with the simulation results. Finally, a material damage ontology model is introduced, and the structural damage caused by different overloading rates is compared and analyzed. Results show that the finite element modeling method is accurate by comparing with on-site measured data, and it is suitable for the numerical simulation of segmental girder bridges; Dynamic sensors installed at 1/4L, 1/2L, and 3/4L of the segmental girder main beams could be used to identify the dynamic response of segmental girder bridges; The bottom plate of the segmental girder bridge is mostly damaged at the position where the length of the precast beam section changes and the midspan position. With the increase in load, damage in the direction of the bridge develops faster than that in the direction of the transverse bridge. The findings of this study can guide maintenance departments in the management and maintenance of bridges and vehicles. [ABSTRACT FROM AUTHOR]

The blast resistance of a typical two-lane steel girder highway bridge structural system was modeled using a nonlinear finite-element approach that considered material damage, fracture, and separation. Critical blast scenarios were based on field observations of terrorist attacks on bridges in Iraq, while system failure was defined in terms of practical emergency serviceability criteria used on actual blast-damaged bridges. The blast resistance of various design parameters was assessed, including the number of girders, deck concrete strength, reinforcement ratio, slab thickness, girder and reinforcement yield strength, girder sectional dimensions, and pier column width. The presented approach uniquely quantifies structural system blast resistance in terms of the charge weight that can be applied at different locations until failure. A sensitivity analysis was conducted to determine the most influential design parameters. It was found that system blast capacity was primarily influenced by the number of girders and girder yield strength, while additional significant parameters were deck compressive strength, deck thickness, web stiffener width, and girder depth. Secondary parameters were deck reinforcement ratio, girder flange, and web thickness, while deck reinforcement yield stress was found to be insignificant. Based on the results, recommendations for improving blast resistance are provided. [ABSTRACT FROM AUTHOR]

The existence of water-filled barriers alters the cross-sectional shape of the main girder, which may lead to vortex-induced vibrations (VIVs) in suspension bridges. However, the mechanism and occurrence conditions of VIVs in the main girder that is affected by water-filled barriers are still unclear. To this end, this study investigates the effect of water-filled barriers on the VIV performance of suspension bridges. The evolution of the vortex structure during one VIV cycle and the corresponding pressure variations, including the average and fluctuating values on the surface, were analyzed. Additionally, the spatiotemporal distribution of the surface pressure was studied using proper orthogonal decomposition (POD). The results show that VIV occurs in the main girder when the height of the water-filled barriers exceeds a threshold value of 0.317. Moreover, a significant negative pressure vortex occurred when the barriers were installed. The vortex underwent the following distinct phases in one VIV cycle: generation, separation, reattachment, and shedding. However, the negative pressure vortex behind the barrier did not vary substantially when the water-filled barriers were installed without VIV. Additionally, the average pressure on the surface of the main girder remained constant regardless of the occurrence of VIVs. In the presence of VIVs, the pressure fluctuations became much more pronounced and were mainly concentrated on the top surface and leading edge of the main girder. Additionally, the dominant modes of the pressure variations correlated with the evolution of the vortices and pressure distribution. [ABSTRACT FROM AUTHOR]

AbstractWhen a train traverses a curved bridge, it inherently tends to shift laterally outward. To counteract this propensity, the strategy of track superelevation is employed. After earthquake, curved bridges may exhibit diverse degrees of residual deformation. The precise failure mechanisms that compromise train safety and passenger comfort during transit over curved bridges, particularly under the combined influence of residual deformation, centrifugal force, and track superelevation, remain not entirely comprehended. A comprehensive system integrating trains with curved track-bridges is developed to examine the impact of girder end misalignments on residual track irregularities. The analysis concentrated on the dynamic time-history responses of trains traversing bridges featuring girder misalignments, exploring a range of amplitudes, train velocities, and curve radii. The findings revealed significant variances in the dynamic train responses, especially in lateral acceleration and the Nadal index, when contrasting centripetal and centrifugal girder side misalignments. Furthermore, it is discerned that lateral misalignment at the girder ends markedly affects train lateral acceleration and the Nadal index, with a relatively minor influence on other dynamic response metrics. Finally, the thresholds for misalignment deformation were summarized, for curve radii of 800, 1000, and 1200 meters, the comfort deformation thresholds at 100 km/h are determined to be 23, 23, and 20 mm respectively, while the safety deformation thresholds are found to be 26, 30, and 38 mm respectively. At a speed of 120 km/h, the comfort deformation thresholds for the same curve radii are 18, 18, and 15 mm, with the safety deformation thresholds at 12, 15, and 21 mm. [ABSTRACT FROM AUTHOR]

A series of bridge overturning accidents in recent years indicates that single-column pier bridges are susceptible to overturning failure. However, the traditional calculation method was incapable of ensuring an accurate prediction of the ultimate overturning capacity, which may lead to serious consequences in engineering practice. In this work, an analytical method was proposed based on the identified failure mechanisms. The forensic survey was first carried out on two typical overturning cases, and the findings of the surveys were summarized into three typical overturning failure modes and their corresponding criterion for failure evaluation. Further, the analytical method was proposed on the assumption that overturning of the girder consists of rigid and deformable body rotation and characters including radial bending and torsional deformation were considered. The method was later validated by the field data of the overturning cases. Besides, factors influencing the results were also compared and analyzed. The results demonstrate that, in comparison with the conventional calculation method, the proposed approach more effectively accounts for spatial parameter variations and nonlinear factors during girder rotation, thereby aligning better with the actual overturning process. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of segmental joints are pivotal in defining the comprehensive stress behavior of prefabricated assembled cover beams. In this research, direct shear tests were conducted on dry key‐tooth joints, and acoustic emission technology was employed for monitoring purposes. The shear failure mechanism was explored under a range of influential parameters. Building upon these observations, the study delved into the mechanical response of joints within segmental cover girders subjected to concurrent bending and shear forces. Specimen K‐3‐3 exhibited a higher shear carrying capacity compared to other specimens, indicating that the shear resistance of dry joints proportionally increases with the height of the specimen and the strength of the concrete. The carrying capacity of Specimen K‐4 was marginally lower than that of Specimens K‐3‐1 and K‐3‐2, suggesting that increasing the number of keys does not significantly impact the shear resistance of dry joints. Notably, Specimen K‐3 demonstrated exceptional shear carrying capacity, exhibiting minimal relative slip during failure, and streamlined the casting process. Consequently, these dry joints featuring large key teeth are deemed more appropriate for use as shear connectors in precast concrete segmental cover beams. Crack patterns in large key tooth precast concrete segmental cover beams propagate along the joints. A damage evolution model for the specimens, based on spatial b‐values and T‐values, visually depicts the damage extent in large key tooth precast concrete segmental cover beams. This model demonstrates excellent agreement with experimental results and provides a solid foundation for theoretical research and practical applications of large key tooth precast concrete segmental cover beams. [ABSTRACT FROM AUTHOR]

This research studies shear strengthening performance for Normal Concrete (NC) beams employing Engineered Cementitious Composite (ECC) reinforced with Galvanized Welded Wire Mesh (GWWM) in conjunction with/without a prestressing system. Six full‐scale Reinforced Concrete (RC) beams were experimented under static monotonic loading at critical shear span zone up to collapse. The investigated factors were: the type and technique of strengthening, materials used for strengthening, and size and configuration of shear reinforcement. Two techniques were introduced: ECC layer reinforced with GWWM and pretensioned steel bars recovered by ECC with one GWWM. GWWM with and without pretensioned steel bars were delivered as shear reinforcement for strengthening. Vertical and inclined steel bars were the two configurations selected for the prestressing technique for suppressing shear stress. The study was discussed through the experimented beams' crack load and pattern, collapse mode, elastic stiffness, absorbed energy, initial cracking load, and ultimate load, along with the corresponding defection. Experimental results showed that both exploited techniques could govern crack patterns, enhance the failure mode, and upgrade ultimate loading capacity up to 52%. Finite element models were built up, simulating those strengthened with an ECC covering layer augmented with GWWM extracting a model with an error of about 3%. [ABSTRACT FROM AUTHOR]

Lateral torsional buckling reduces the moment capacity of steel I-girders. To redress this weakening, one approach is to replace the conventional plate flange with a rectangular tube, which has higher lateral stiffness and is thus helpful to resist lateral buckling. At the same time, web openings are introduced to enable services to pass through, but this causes a reduction in strength. Girders with tubular flange plus web openings have not yet been discussed in the literature. In this paper, finite-element method modelling is used to fill this gap, studying different slenderness classifications, as well as parameters such as size of web openings, spacing and location. The results for a solid web are found to be more comparable to the Eurocodes for steel structures than the American Institute of Steel Construction codes, enabling good prediction of the flexural capacity. By introducing web openings, the flexural capacity is reduced by 10–20%, closer to the higher side for openings with large diameters located near the compression flange. Openings with an oval shape have less reduction in strength, whereas the square is unfavourable. Tubular flange girders, even if perforated, provide flexural strength enhancement and a considerable reduction in material compared with plate flange girders. This section also behaves better in relation to carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

Direct resistance check by applying advanced numerical models is getting increasingly used for the design of steel slender plated structures. This method has to take into account the same uncertainties as traditional analytical design calculations and should ensure the Eurocode-based prescribed safety level. The application of the model factor gives the possibility to account for the model-related uncertainties. The current study focuses on the determination of the model factor for one specific failure mode, the patch loading resistance. Numerical model has been developed and validated based on laboratory test results. To evaluate the model uncertainties, physically possible modeling differences are introduced, and their effects are evaluated on the resistance. The final aim of the study is to determine the model factor for the analyzed girder type and failure mode based on statistical evaluation. [ABSTRACT FROM AUTHOR]

In railway tracks, additional stresses occur in rails due to interaction between the rail and the bridge superstructure, which is a phenomenon known as track–bridge interaction (TBI). The additional rail stresses (ARSs) develop primarily as a result of temperature effect, vertical bending of bridge superstructure, and braking/acceleration of trains traveling over the bridge. One of the major parameters affecting the TBI response is the behavior of interface elements simulating the coupling between the bridge superstructure and the rail. In TBI analysis this coupling is defined by the so-called longitudinal resistance-displacement curves (RDCs). The present study deals with the longitudinal aspect of TBI though a numerical investigation. The numerical modeling approach was verified with available analytical solutions and data obtained from bridge monitoring. The primary interest was to illustrate how sensitive the TBI response is to changes in RDCs with both separate and sequential analysis approaches, which has not been investigated thoroughly earlier. The parametric study was extended to investigate the effects of expansion length and substructure stiffness, in addition to RDC type. For simply supported precast girder bridges, RDCs that are experimentally proven specific to ballastless railway bridges can be used as an economic alternative to those specified by provisions. [ABSTRACT FROM AUTHOR]

This research presents an experimental program for flexural strengthening of reinforced concrete (RC) full-scale girders with externally bonded carbon fiber–reinforced polymer (CFRP) sheets secured with fiber anchors. The testing program consisted of five RC T-girders strengthened with identical CFRP sheets anchored with different numbers of CFRP fiber bundles. The main objective of this study is to address the effectiveness of the CFRP fiber anchors in controlling premature failure of the CFRP sheets due to debonding. To evaluate the experimental results, a simplified design model was introduced to predict the effective CFRP maximum strain limit associated with a given number of fiber anchors in the shear span. The test results show that using CFRP fiber anchors significantly delayed the failure of the CFRP sheet beyond the classical intermediate crack (IC) debonding failure mode. In addition, the presented design model agrees reasonably well with the experimental findings as it pertains to the various numbers of anchors. Nevertheless, an anchor efficiency factor is proposed herein to reflect the fiber anchor group effect based on the experimental findings. Practical Applications: This paper presents an experimental program and a design model to capture the efficiency improvements of the response of carbon fiber–reinforced polymer (CFRP) strengthened full-scale reinforced concrete T-girders secured with increasing number of carbon fiber anchors along the shear span. Both the equivalent debonding strain and load capacity were improved owing to the use of increasing numbers of fiber anchors per shear span. This study showed that the ultimate failure of the girders can be controlled by the number of fiber anchors used to secure the CFRP sheets. Sectional analysis may not be strictly applicable once the progression of debonding starts. However, it is shown to capture a reasonably accurate measure of the maximum CFRP debonding strain without the need to resort to higher-order analysis that does not lend itself to design practice. [ABSTRACT FROM AUTHOR]

In this paper, the dynamics of an axially translating functionally graded cantilever beam (FGCB) with time-varying length are studied under environmental temperature variations. Firstly, the governing partial differential equation for the FGCB under different temperatures is established based on the Euler–Bernoulli beam theory. Secondly, the Galerkin discretization and the assumed mode method (AMM) are employed to derive the vibration equations for each mode. Then, the coupling effects of the axial translation motion and the bending deformation on the vibration response of the FGCB are analyzed through numerical simulation. The results showed that different initial lengths, velocities and accelerations can influence the dynamic response greatly. Moreover, the increase in temperature will increase the response amplitude and decrease the frequency of FGCB, but the increase in functionally gradient parameter will decrease both the amplitude and the frequency of the FGCB. Finally, the wavelet transform (WT) is utilized to perform a time–frequency analysis. It is found that the time-dependent frequency obtained by using WT is consistent with the first-order static frequency obtained theoretically. The variation of frequency with time can be obtained quickly and accurately by using WT. The results of this research are of great significance for the application of composite axially translating beams in practical engineering. [ABSTRACT FROM AUTHOR]

Corrugated steel web (CSW) sections are utilized worldwide in civil and mechanical engineering because of their advantages over flat sections, including enhanced lateral stability, a higher strength-to-weight ratio, improved energy absorption, and a reduced need for vertical stiffeners. The stability of such thin-walled structures becomes critical due to the small thickness of components and complex geometry. While lateral torsional buckling (LTB) can be avoided through lateral restraints, individual components of a girder, i.e. web and flanges, may undergo failure due to local instability. This paper focuses on summarizing the approaches for evaluating the local stability behavior of the flange and web sections. The review presents a holistic overview of the existing analytical, numerical and experimental studies on the web and flange instability of CSW girders. A numerical evaluation of local shear and flexural stability is presented using existing approaches. The influence of different geometrical parameters is summarized and important observations are highlighted for future research in this area. [ABSTRACT FROM AUTHOR]

The use of advanced materials, such as ultra-high-performance concrete (UHPC), and slender cross-sectional shapes in bridge girders can result in high susceptibility to shear failure during fire exposure. Shear limit state is usually not considered in fire design, which can be a major risk for I-shaped girders with slender webs. This paper presents the development of an approach to evaluate the shear capacity of UHPC bridge girders during fire through extension of room temperature capacity equations to elevated temperatures. Four types of standard AASHTO concrete bridge girders are analyzed under both standard and hydrocarbon fire scenarios. The output results are utilized to evaluate the progression of temperatures and deflections throughout fire exposure, as well as estimate degradation in flexural and shear capacities. Results show that the fire resistance of UHPC bridge girders are significantly affected by fire severity and concrete mass and that these factors should be taken into consideration in fire design of UHPC bridge girders. [ABSTRACT FROM AUTHOR]

I-shaped concrete girders are widely used in precast bridge and roof construction, making them a common structural component in existing infrastructure. Despite well-established strengthening techniques using various innovative materials, such as externally bonded carbon fibre reinforced polymer (CFRP) reinforcement, the shear strengthening of an I-shaped concrete girder is not straightforward. Several research studies have shown that externally bonded CFRP reinforcement might exhibit early debonding at the concave corners of the I-shape, resulting in a marginal increase in shear capacity. This research study aims to assess the performance of two different CFRP shear strengthening strategies for I-shaped concrete cross-sections. In the first strategy, CFRP was bonded along the I-shape of the cross-section with the provision of additional anchorage. In the second strategy, the I-shape was transformed into a rectangular shape by using in-fill blocks over which the CFRP was bonded in a U-configuration. In addition to the strengthening strategies, the investigated parameters included two different materials for the in-fill blocks (conventional and aerated concrete) and two different anchoring schemes (bolted steel plate anchor and CFRP spike anchor). To avoid testing on large-scale girders, a new test methodology has been implemented on concrete I-sections. The test results demonstrate the feasibility of comparing different shear strengthening configurations dedicated to I-sections. Among other findings, the results showed that the local transformation of the I-shape to an equivalent rectangular shape could be a viable solution, resulting in shear strength enhancement of 12% to 53% without and with the anchorages, respectively. [ABSTRACT FROM AUTHOR]

Fatigue strength of concrete decks for large composite bridges In the support area of large composite bridges, tensile stresses occur in the concrete deck slab due to the negative bending moment of the main girders, leading to cracks in the concrete deck. Transverse steel cantilever beams are arranged under the deck at the transverse frame spacing in order to support e. g. prefabricated concrete elements, so that the deck slab predominantly spans in the longitudinal direction. Cyclic transverse forces due to local wheel loads caused by high variable traffic loads must then be transferred to the cross girders via the cracked concrete slab, as a result of the tensile loading. Up to now, no tests have been carried out to determine the fatigue strength of the cracked concrete deck slab. Based on tests from the literature (whereby so far only well documented tests without longitudinal tensile loading have been available) and own experiments (with longitudinal tensile loading), a database has been developed which formed the basis for the derivation of S‐N‐lines and which allowed the evaluation of the influence of specific parameters on the fatigue strength. Since the fatigue strength of reinforced concrete elements without shear reinforcement is dependent on the static load‐bearing capacity, the influence of the scatter of the static shear capacity on the fatigue strength is discussed in particular. Based on the results and the current state of standardization, a design concept for the fatigue strength of the concrete deck slab is presented. [ABSTRACT FROM AUTHOR]

Prestress concrete composite girders with full‐depth precast bridge deck panels (PC composite girders) have been widely utilized in civil engineering due to their high production quality, reduced construction duration, potential weight reduction, and lower life‐cycle cost. The interface shear behavior in ultra high‐performance concrete (UHPC)–normal concrete (NC) connection interface of full‐depth deck PC composite girder has been extensively studied. This study conducted seven push‐off tests to examine the shear performance of UHPC‐filled joints between precast I‐girders and full‐depth precast concrete slabs. The testing variables included the quantity, and spacing of the Ubars, as well as the type of UHPC‐filled joints (longitudinal trough connector or pocket connector). The experimental results show the quantity and spacing of Ubars have a significant impact on both the interface shear capacity and residual shear resistance. For continuous shear connectors with reserved notches specimens, the ultimate load of the 4Ubar and 6Ubar specimens increased by 93% and 194%, respectively, compared with the 2Ubar specimens. With the increase of the spacing of the Ubar, the ultimate load will decrease. When the spacing between Ubars increases from 100 to 150 mm, the normalized ultimate load decreases by 51 kN. The type of joints also plays a crucial role in determining the ultimate shear‐bearing capacity of the specimens. The Ubars in pocket connector specimens will provide a greater contribution to the ultimate shear bearing capacity than longitudinal trough connector specimens and the ultimate stress of the 4Ubar and 6Ubar pocket connector specimens are greater than that of the longitudinal trough connector specimens by 232% and 323%. The study introduces the concept of pulling angle. In the experiment, the specimen with a large length is less affected by the pulling force. The experimental results in this study can rarely be predicted well by typical equations developed in current design codes and previous studies. Therefore, a more accurate equation was developed to predict the interface shear transfer stress between precast common concrete I‐girder and full‐depth precast concrete slab with UHPC‐filled joints. [ABSTRACT FROM AUTHOR]

Swarm intelligence (SI) algorithms represent a class of Artificial Intelligence (AI) optimization metaheuristics used for solving complex optimization problems. However, a key challenge in solving complex problems is maintaining the balance between exploration and exploitation to find the optimal global solution and avoid local minima. This paper proposes an innovative Swarm Intelligence (SI) algorithm called the Four Vector Intelligent Metaheuristic (FVIM) to address the aforementioned problem. FVIM's search strategy is guided by four top-performing leaders within a swarm, ensuring a balanced exploration-exploitation trade-off in the search space, avoiding local minima, and mitigating low convergence issues. The efficacy of FVIM is evaluated through extensive experiments conducted over two datasets, incorporating both qualitative and quantitative statistical measurements. One dataset contains twenty-three well-known single-objective optimization functions, such as fixed-dimensional and multi-modal functions, while the other dataset comprises the CEC2017 functions. Additionally, the Wilcoxon test was computed to validate the result's significance. The results illustrate FVIM's effectiveness in addressing diverse optimization challenges. Moreover, FVIM has been successfully applied to tackle engineering design problems, such as weld beam and truss engineering design. [ABSTRACT FROM AUTHOR]

This study theoretically and numerically examines the differences in shear performance between tapered and prismatic girder configurations with corrugated steel webs (CSWs) and investigates the influence of the Resal effect on the shear performance of tapered girders with CSWs. The vertical components of the inclined bottom slab forces (which are zero in prismatic cases) may decrease or increase the effective shear force on the CSWs, reflecting the positive and negative influences of the Resal effect. Based on these influences, this study introduces the concepts of positive and negative Resal effects and proposes an improved shear method to predict the effective shear forces acting on tapered CSWs. The results of the theoretical and finite element (FE) analyses show that the traditional shear method, which assumes CSWs bear all the shear force, is not applicable to tapered girders. The improved shear method significantly reduced the error in predicting shear forces within the CSWs, decreasing the maximum error from 42.25% (traditional method) to 7.71% (improved method) in specific sections. Quantitative analyses of three different types of girders with CSWs indicate that the Resal effect is influenced by both the internal forces and the structural form of the box girder. In cases of a positive Resal effect, the inclined bottom slab shares a considerable portion of the shear force with CSWs, resulting in a surplus shear capacity in the CSWs; conversely, under a negative Resal effect, there is an increase in the effective shear force on the web, which could lead to an overestimation of the shear buckling strength of CSWs. These findings highlight the necessity of incorporating Resal effects for accurate shear force predictions in tapered girders. By accurately predicting shear forces, engineers can enhance the performance and reliability of these structures, avoiding both overestimation and underestimation of shear capacities. [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]

Skewed supports complicate load paths in continuous steel I-girder bridges, causing secondary stresses and differential deformations. For a continuous bridge where tensile stresses are developed in the top flange of the steel girders over the intermediate supports, these effects may exacerbate potential fatigue issues for the top flanges. There is a gap in knowledge regarding the level of stress one can expect at these locations, and the stress level can render the problem either serious or trivial. This paper has been successful in providing this information, which was not available before. The study examines the fatigue performance of the top flange in girders over skewed supports. Results are presented from a detailed investigation consisting of 3D finite element modeling to evaluate 26 skewed bridges in the State of Florida that represent the wide range of geometries found in practice. The analysis focused on stress ranges in the top flanges and axial demands on end cross-frame members under fatigue truck loading. A preliminary analysis helped to select the appropriate element type and support conditions. The maximum factored stress range of 3.63 ksi obtained for the selected group of bridges remains below the 10 ksi fatigue threshold for an AASHTO Category C connection, alleviating the concerns about the fatigue performance of the continuous girder top flange over the intermediate pier. Hence, fatigue is unlikely to be a concern in the flanges at this location. Statistics on computed stress ranges and cross-frame forces that provide an understanding of the expected values and guidance for detailing practices are also presented. A limited comparative refined FE analysis on two different types of end cross-frame to girder connections also provided useful insight into the fatigue sensitivities of the skew connections. Half-Round Bearing Stiffener (HRBS) connections performed better than the customary bent plate connections. The HRBS connection reduces girder flange stress concentration range by at least 18% compared to the bent plate connection. The maximum stress concentration range in bent plate components is significantly higher than in the HRBS connection components. The work documented in this paper is important for understanding the fatigue performance of the cross-frames and girders in support regions in the upcoming 10th edition of the AASHTO Bridge Design Specifications that may include plate stiffeners oriented either normally or skewed to the girder web, or Half-Round Bearing Stiffeners. [ABSTRACT FROM AUTHOR]

As the prefabrication construction method plays an increasingly important role in the construction of cross‐sea bridges, coordinating the schedule between off‐site prefabrication and on‐site assembly becomes crucial and challenging. This paper studies a just‐in‐time single‐machine scheduling problem with due windows and release dates, which originates from the production and supply process of large segments of precast steel box girders in bridge construction. To solve this problem, we equivalently decompose it into the independent and same type of subproblems and formulate a mixed‐integer linear mathematical programming model. Furthermore, we propose a branch‐and‐bound algorithm with the initialization of a novel linear early and tardy dispatching rule with due windows to solve the problem exactly. The dispatching rule, based on the local dominance criteria with due windows, is designed and used to improve the upper bound. Moreover, a lower bound is obtained by further decomposing and relaxing the subproblems. Finally, the parameter of the dispatching rule is calibrated, and the best search strategy of the branch‐and‐bound algorithm is determined. The comprehensive computational experiments carried out show the efficiency and effectiveness of the proposed branch‐and‐bound algorithm. [ABSTRACT FROM AUTHOR]

In reinforced concrete (RC) buildings, the seismic behaviour of RC beams with flush outside faces of beams and columns has not been verified by experiments. In this study, four large RC beam specimens were fabricated and an experimental verification was conducted. The results showed that all of the specimens (including three beam specimens with flush outside faces of beams and columns) could withstand ultimate drift angles up to 4% rad. In addition, the lateral strength and seismic behaviour of a specimen with a concrete cover of 85 mm were no less than those of the benchmark specimen, so a concrete cover thickness of 85–40 mm should be acceptable for RC beams. The seismic behaviour of two specimens with lateral U-shaped auxiliary transverse reinforcement and a concrete cover of 85 mm was better than that of the benchmark specimen, but the crack width of the latter was wider and the spalling degree of the concrete cover was more serious. Based on the results of this work, the practical recommendation is to adopt lateral U-shaped auxiliary transverse reinforcement in which the two legs extend beyond half the width of the hoop, with two auxiliary longitudinal reinforcements and the same spacing as the hoop. [ABSTRACT FROM AUTHOR]

The new generation of China Railway Track System III (CRTS III) ballastless track structure has been found vulnerable under high-level earthquakes. However, the seismic characteristics and the damage mechanism had not been well studied. In this paper, a 4-span high-speed railway (HSR) simply supported bridge-track system model is established to investigate the seismic response and damage mechanism of the bridge-CRTS III slab ballastless track system under transverse earthquakes by nonlinear history analysis. In accordance with the results, the piers have a good seismic performance under high-level earthquake (0.57 g). The non-uniform vibration of unequal-height piers results millimeter-level inconsistent displacements between the girders. The fixed bearing is vulnerable under the earthquakes with PGA of 0.3 g and 0.57 g, indicating that the seismic design of fixed bearing should be optimized to enhance the seismic resistance under high-intensity earthquake. After the damage of fixed bearing, the friction is not enough to pull the girders to vibrate together with piers which leads the sliding of girders. The sliding of girder exacerbates the non-uniform displacements of girders and roadbed. The non-uniform vibration and residual slips of girders lead deformation of the rail, especially forming turning angles at the girder joints which may impact the safety of train operation. [ABSTRACT FROM AUTHOR]

This study evaluates the mechanical performance of composite girders with corrugated steel webs via finite element modeling in ABAQUS. Utilizing corrugated steel webs enhances structural efficiency and material economy. The research delves into shear-bending interactions, analyzing load capacity, deflection trends, and failure mechanisms. ABAQUS simulations provide insights for design optimization of these girders in engineering contexts. The findings advance understanding of composite girders with corrugated webs, fostering more effective and sustainable construction practices. The investigation focuses on using corrugated plates to bolster the shear zones in plate girders. theoretical analyses of girders with corrugated web plates demonstrate their shear zone reinforcement capabilities. Different thickness of trapezoidal corrugated steel webs in girder specimens (4, 8, 12, 16, 20 and 24 mm) underwent two-point load testing to study the corrugation's interaction with the girders. Trapezoidal patterned corrugated web specimens against one control beam shows corrugation's significant impact on girder stability, enhancing ultimate load capacity and delaying buckling. A numerical analysis using confirmed the corrugated web's role in increasing buckling resistance. [ABSTRACT FROM AUTHOR]

The paper deals with analyzing corrosion waste impact on ship girder strength through the life cycle. Evaluation of corrosion impact on ship strength is important because in some loading cases the ships are in overloaded condition. It is assumed that corrosion wear varies from 0 to 60%. Reduction of their transverse strength in combination of bad weather or sudden storms leads to cargo lost, ship damage and loss of human lives. Strength and plating elements bending capacity are evaluated by ship midsection model development and compared with the same for a new building ship. Helped by the relation between permissible and actual bending moment, plate bending efficiency is evaluated. Ultimate ship girder strength in cases with corrosion waste of more than 30% is evaluated too. [ABSTRACT FROM AUTHOR]

Cranes are employed to lift precast concrete girders during their construction. Presently, there is no recommendation for operational velocities during girder assemblage, particularly for long elements; simultaneously, several accidents have been reported during the transitory phase of girder motion. Since this mechanical problem has been examined in technical literature using a static approach, the present research study aims to investigate the dynamical behavior of a long, prestressed concrete girder by determining critical operational velocities according to crane movements. Prestressing cables' eccentricity and lifting loop position deviation were accounted for in 3D finite element simulations of a 40 m span precast prestressed concrete girder. Transient nonlinear analyses to obtain stresses and deflections were performed, so as to account for the large deformation behavior of the motion. A frequency domain approach was employed to analyze the time history results using the girder's natural frequencies obtained by modal analysis. The finite element model was developed to simulate upward, downward, and lateral girder movements. The most significant displacements and stresses were observed in the highest girder acceleration peaks, amplified by eccentricities. Safety against cracking and subsequent failure during vertical and lateral movements was ensured for crane operating accelerations of 0.02 g (v = 20 cm/s) and 0.007 g (v = 7 cm/s), respectively. Compared with the usual static analysis, for the critical case investigated, the inertial effect intensified the tensile stresses by 27 times, increased the compressive stresses by 11%, and increased the girder deflection by 3 times. [ABSTRACT FROM AUTHOR]

The long‐term behavior of slender (1/40) long‐span precast high‐strength concrete girders was experimentally investigated regarding their use as a competitive solution in relation to steel alternatives for highway overpasses. The time‐dependent effects of full‐scale girders has rarely been addressed, particularly the influence of creep and shrinkage of concrete with compressive strengths around 120 MPa. Two half‐scale girder specimens were produced using an economically optimized and high‐strength concrete mixture, nonfiber reinforced, designed only with conventional raw materials, currently available at Portuguese precast companies, and subjected to long‐term loading, with a magnitude of approximately 50% of the failure load in bending, during a period of 3.75 years. Using the same mixture, prismatic specimens were also produced and subjected to long‐term loading at 24 h and 7 days of age to assess both creep and shrinkage. Results show that the age of concrete at the loading day is of paramount importance regarding the time‐dependent effects. These are most relevant during the first days of loading and tend to stabilize from the 112th day of loading onward. The time‐dependent girder's mid‐span deflection at the end of the 3.75 years did not exceed more than 50% of the initial deformation. Comparison of results with those obtained with Model Code 2010 and the current version of Eurocode 2 shows that these underestimate strains and deflections due to creep, mostly because the short‐term development of these effects, occurring during the first days of loading, are not adequately represented. On the contrary, a sound agreement between experimental and theoretical values, both in short and long term, was obtained using the Auperin et al. approach. [ABSTRACT FROM AUTHOR]

Considering the advantages of hybrid steel I-section beams in reducing engineering costs and fully utilizing the mechanical properties of steel, and the lack of research on their ductility, hybrid steel I-section beams were tested to analyze the effects of the plate width–thickness ratio and steel strength matching on the flexural bearing capacity and ductility. The steel strength matching of the hybrid steel I-section beam with a high steel strength utilization rate and good ductility was related closely to the section size. Additionally, a parametric analysis based on the finite- element method was performed for further study. The steel strength ratio φ of the web to the flange with the best ductility was less than 1, and φ decreased with an increase in flange steel strength. The steel strength utilization rate and ductility decreased with an increase in φ. Based on the parametric analysis results, the optimal range of φ in hybrid-steel I-section beams with flange steel strength of 460–690 MPa was 0.56–1. The plate width–thickness ratio limit of the ductile section decreased with the decrease of φ. Considering the plate interaction and steel strength matching, a sectional ductility design method is proposed that is more applicable to hybrid steel I-section beams than existing methods. [ABSTRACT FROM AUTHOR]

In the actual structural health monitoring system of suspension bridges, only part of suspenders tension can be monitored, but not all the suspenders tension can be obtained. To solve this problem, a method for suspenders tension identification of bridges based on the spatio‐temporal correlation between the girder strain and suspenders tension is proposed. By using actual monitoring data of vehicle loads, a spatio‐temporal correlation model of the girder strain and tension forces of all suspenders is constructed based on the combined application of stacked denoising autoencoder and convolutional neural networks‐long short‐term memory model, so as to realize the preliminary identification of suspenders tension. On this basis, by using the actual monitoring data of suspenders tension and the strain monitoring data obtained through the distributed optical fiber sensors, the delicate identification of tension forces of all suspenders is realized based on the error interpolation of preliminary identification results. The results of the example bridge show that the method in this paper can effectively identify tension forces of all suspenders of the suspension bridge, and identification results are more accurate than the method using only the monitoring data of suspenders. [ABSTRACT FROM AUTHOR]

Sea-crossing bridges are generally subjected to the combined wind, wave and current action, making it worthwhile investigating the dynamic response of cable-stayed bridges under wind-wave-current action. In this study, the numerical wave flume is utilised to obtain wave-current action, where a measured spectrum is applied to generate random waves. The stochastic wind field is calculated through the spectral representation model. These actions are validated by comparing experimental and theoretical results. A comparative analysis under different loads provides the theoretical basis for load type determination. The influence of pile–soil interaction is also studied with the consolidation, pile–soil solid contact (PSSC), and soil spring model. The results show that the root mean square (RMS) values of girder displacement are greater under regular wave-wind-current action, while the extreme values of the girder internal force present the opposite pattern due to the statistical characteristics of random waves. It indicates that the statistical characteristics of random waves should be considered to secure the girder safety. For the bridge tower, the random wave-wind-current action has a greater effect on the lateral displacement responses. Furthermore, the model considering the pile–soil interaction gets more flexible, absorbing more energy of low-frequency wave-wind-current action. [ABSTRACT FROM AUTHOR]

Nonlinear static (pushover) analysis is widely used for analyzing structures, especially in the performance-based design method. Increasing the lateral load in pushover analysis causes changing the axial forces of beam-column members during the analysis. Whereas the axial load of beam-column elements can significantly affect the moment-curvature properties of these elements, in most pushover analyses, the momentcurvature curve of these elements is generally achieved based on the gravity axial loads and remain constant throughout the analysis. Furthermore, the confining action depends on the axial load of beam-column elements. In this study, a novel pushover analysis is developed to update the moment-curvature properties of beam-column elements based on the axial forces of these elements throughout the analysis. The confining effect is considered on the moment-curvature properties of beam-column elements as well. Furthermore, the influence of updating the moment-curvature properties is shown by comparing the responses of the updated and traditional pushover analyses. The method is applied to three reinforced concrete frames from the previous studies to assess the influence of the variation of moment-curvature properties on the capacity curve of these frames. Outcomes show that the variation of axial loads significantly affects the momentcurvature of beam-column elements especially for edge columns located in the lower stories of frames. Furthermore, considering the progressive changes of moment-curvature properties of beam-column elements during the pushover analysis accounting for the variations of axial forces leads to reducing the lateral load-carrying capacity e.g, ductility, secant stiffness ultimate strength, etc. [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 research presents the single Fourier sine transform method (SFSTM) for solving the Saint Venant torsion problem of rectangular prismatic bars. The problem is a common theme in the theory of elasticity of unrestrained torsion which was previously expressed by Prandtl using Prandtl stress functions ϕ, (x, y) as a Poisson type nonhomogeneous partial differential equation (PDE) called the stress compatibility equation. In this work the SFSTM was applied to the stress compatibility equation, converting the PDE to an easier to solve ordinary differential equation (ODE) in the transformed domain. The boundary conditions were used to find the integration constant and inversion was used to find the solution in the physical domain. The non vanishing stresses and torsional moments were thus found as a single series of infinite terms with rapid convergence. The maximum stresses and moments were found in standard form in terms of torsional parameters which were tabulated for various ratios of the cross-sectional dimensions. A comparison of the torsional parameters with previous results show that the present results are identical with previous results illustrating the accuracy of the SFSTM used. The sine kernel of the SFSTM satisfies the boundary conditions of the problem and contributed to the exact solution obtained. The SFSTM simplified the PDE to an ODE which is simpler to solve. [ABSTRACT FROM AUTHOR]

The residual flexural behavior of semilightweight prestressed concrete voided slab girders taken from a decommissioned 28-year-old bridge near Barrhead, Alberta, Canada was investigated. The residual flexural behaviors under loads corresponding to the serviceability limit state (SLS), the ultimate limit state (ULS), and the failure state were evaluated using four-point bending tests. Four girders with different deterioration levels were tested, with one girder exhibiting no visible deterioration considered as the control girder. Material tests on concrete, mild steel reinforcement, and prestressing strands were conducted to better understand girder behavior. Strand corrosion reduced the girder flexural strength by 14%–22% and changed the failure mode from concrete crushing after steel yielding to undesirable strand rupture prior to yielding. However, all girders, regardless of deterioration level, showed satisfactory performance under SLS and ULS loads. The effective prestress force was also studied using digital image correlation (DIC). North American bridge design codes were used to predict the cracking load and flexural strength considering the influence of different corrosion effects. Steel area loss was shown to be the most important factor for both cracking and flexural capacity reduction. [ABSTRACT FROM AUTHOR]

Composite steel bridges in the United Sates are typically constructed using 22 mm-diameter (7/8 in.-diameter) shear studs. The number of shear studs on a girder can be significantly reduced by using larger-diameter studs. This study employed 11 push-out tests to investigate the static performance of 29 mm-diameter (1-1/8 in.-diameter) shear studs. An extensive welding investigation was conducted to develop the optimum welding parameters for 29 mm-diameter studs. Results from experiments showed the static strength of 29 mm-diameter studs satisfied stud strength equations in the AASHTO LRFD Bridge Design Specifications and Eurocode 4. The ductility of the 29 mm studs was comparable or better than that of 22 mm-diameter shear studs. Concrete cracking under service level loading was similar between specimens with 22 and 29 mm studs. Observations indicate that the minimum allowable stud penetration into the concrete deck may need to increase in order for the 29 mm-diameter studs to have good static performance. Using partial-depth precast concrete panels in the bridge deck reduced the static strength of both 22 and 29 mm-diameter shear studs in push-out specimens. Efficient steel bridge girder design makes use of a composite action between the concrete deck and the steel girders. Composite action is achieved by welding shear studs to the top flange of the steel girder during fabrication or erection. The number of shear studs needed is directly related to the individual stud strength, which is controlled by the stud diameter. The shear stud diameter most commonly used in steel bridge construction throughout most of the United States is 22 mm. This paper presents laboratory experiments evaluating the static strength of 29 mm-diameter shear studs. The test results showed that 29 mm-diameter shear studs have a static strength that satisfies US bridge design standards. Compared with 22 mm-diameter shear studs, the use of 29 mm-diameter shear studs is estimated to reduce the number of studs needed on a steel bridge girder by 40%. This reduction in the number of shear studs can enhance construction safety, reduce the cost of fabrication, and facilitate the use of partial-depth precast concrete deck panels, which in turn can increase the speed of construction. [ABSTRACT FROM AUTHOR]

The gantry crane, positioned atop the bridge pier cap for the installation of Super-T girders, is a specialized construction unit within the bridge construction industry. The article presents a summary of research results investigating dynamic parameters and their influence on the operation of gantry cranes with assembled structures on the cap of bridge piers, serving the installation of Super-T beams in two scenarios: lifting with pre-stressed cable and moving with load (Super-T beam). To examine the dynamic parameters affecting the operation of the gantry crane, the authors first constructed a dynamic model. Subsequently, the influential parameters were determined, and the Matlab Simulink software was employed to develop a survey model corresponding to different values of each parameter and under various working conditions of the gantry crane. This process aimed to identify patterns and unfavorable values of these parameters affecting the operation of the gantry crane. The research results revealed that in both scenarios of lifting with pre-stressed cable and moving with a load (loading), factors such as lifting speed (Vn), stiffness of the main steel structure (S3), conversion stiffness of the lifting cable (S1), oscillation mass of the main structure (m3), wind load acting on the beam (Pg2), wind load acting on the main steel structure (Pg1), and stiffness of the hanging cable (S1) significantly influence the operation of the gantry crane. The survey results also indicated reasonable values for these influential factors during the operation of the gantry crane. The obtained research results can serve as a basis for computational design problems and effective utilization of gantry cranes with assembled structures on the cap of bridge piers for the installation of Super-T beams. Through analysis and simulation using Matlab-Simulink software, specific data on cable tension, main structure acceleration, and structural deformation were collected. The results emphasize the importance of limiting the lifting speed to 2 m/min to ensure stability during cable tensioned lifting and restricting the crane's moving speed to 7.85 m/min to maintain safety and performance when moving loads with tensioned cables. [ABSTRACT FROM AUTHOR]

Based on the existing permanent load equilibrium method, influence matrix method and adaptive control method, a distributed algorithm and control method for the cable forces of hybrid laminated girder cable-stayed bridges is proposed. The method uses the permanent load equilibrium approach to initially determine the permanent load cable forces, then adjusts it based on the influence matrix of the main girder displacement, and finally combines the calculation of finite element software to determine the cable forces that satisfy the internal force requirements of each member of the hybrid laminated girder cable-stayed bridge under the joint action of permanent load and live load. Through adjusting the cable force of an actual bridge, it can be found that this method is highly efficient in calculation, and the efficiency and accuracy of control of the cable forces are high, ensuring that the cable forces and alignment of the bridge structure after completion are in line with the design expectations. [ABSTRACT FROM AUTHOR]

Assessment and retrofitting of riveted lattice girders in metal roof structures Metal structures from the 19th and early 20th centuries, such as factories, train sheds and market halls, are a valuable and useful heritage. Preserving these structures by maintaining or adapting their use is of economic, ecological, and cultural interest. In this endeavour, accurately assessing their load capacity by calculation is a challenge. In France, riveted lattice girders are widely used in roof structures dating from 1850–1930. Numerically, they present stability problems often leading to preventive strengthening measures. This paper draws on the study of these structural components to explore a novel holistic assessment method that combines structural engineering, construction history and heritage conservation to provide a robust basis for the design of sensitive and targeted structural interventions. This approach could be extended to iron and steel structures of the 19th and early 20th centuries, and broadly to most types of existing structures. [ABSTRACT FROM AUTHOR]

Lateral buckling of precast and prestressed concrete girders that are not fully restrained against twisting rotations at their ends may occur during lifting and handling. Typically, the critical load at which this instability occurs has been estimated by ignoring torsional deformations. Although that approach permits a closed-formed solution, it is unconservative. This study includes the torsional deformations and develops a series solution for the simplest case of an end-supported girder. The solution is then extended to include overhangs. A balance between accuracy and usability is struck by truncating to a one-mode solution. By comparing with two known special cases, the first term is found to be sufficiently accurate while clearly illustrating the effect of torsional flexibility on girder stability. Accounting for torsional deformations reduces the predicted buckling load by an amount that can be conveniently defined with a knockdown factor applied to the traditional buckling load that ignores torsion. In this sense, the effect of torsion is separated from lateral bending. Downward (major-axis) deflection improves stability, whereas that net upward camber does the opposite. Use of lightweight concrete reduces the safety factor against lateral buckling. [ABSTRACT FROM AUTHOR]

Short headed studs used in grouted joints with precast concrete elements are currently not sufficiently covered by EN 1994‐1‐1. Therefore, three test series have been realised to define the load‐bearing capacity under these special conditions. These are characterised by short headed studs of height hsc=65 mm in combination with a high‐strength grout. For a more in‐depth analysis of the load‐bearing and deformation behaviour, a finite element model has been developed and validated on the conducted push‐out tests. Based on subsequent numerical studies – varying geometric and material parameters – recommendations of analytical model equations are given for headed studs of short length. [ABSTRACT FROM AUTHOR]

Featured Application: The study can further guide the application of vortex isolation plates in wind-induced vibration of twin-box girders. Twin-box girders are a good option for long-span cable-bearing bridges due to their excellent stability. Nonetheless, the girder's slots may generate vortex-induced vibrations (VIVs). Fortunately, appropriate aerodynamic measures can effectively suppress the VIVs in twin-box girders while reducing costs. To examine the effects of vortex isolation plates with varying aperture diameters and opening ratios on the VIVs, a segment model wind tunnel test was conducted. The results demonstrated that a reduction in the opening ratio improved the performance under heaving VIVs, but there was no discernible trend under torsional vibrations. It was also discovered that the opening size significantly influences the length of the lock-in region of torsional vibrations. Furthermore, heaving VIVs have a substantial correlation with both of the girder's boxes, while torsional vibrations are mostly connected with the downstream section. [ABSTRACT FROM AUTHOR]

Real-time prediction of hull girder loads is of great significance for the safety of ship structures. Some scholars have used neural network technology to investigate hull girder load real-time prediction methods based on motion monitoring data. With the development of deep learning technology, a variety of recurrent neural networks have been proposed; however, there is still a lack of systematic comparative analysis on the prediction performance of different networks. In addition, the real motion monitoring data inevitably contains noise, and the effect of data noise has not been fully considered in previous studies. In this paper, four different recurrent neural network models are comparatively investigated, and the effect of different levels of noise on the prediction accuracy of various load components is systematically analyzed. It is found that the GRU network is suitable for predicting the torsional moment and horizontal bending moment, and the LSTM network is suitable for predicting the vertical bending moment. Although filtering has been applied to the original noise data, the prediction accuracy still decreased as the noise level increased. The prediction accuracy of the vertical bending moment and horizontal bending moment is higher than that of the torsional moment. [ABSTRACT FROM AUTHOR]

In recent years, with the development of building technology, the Chinese construction industry has begun to gradually promote the prefabricated buildings to save on construction costs. Among them, composite slabs, as essential components of prefabricated buildings, have been widely used by designers mainly in favor of their low cost. However, is it possible to further reduce the cost without affecting the quality? Researchers think so if the operation cycle of support from the bottom of composite slabs can accelerate and the mechanical properties of their bottom plate can be optimized. To prove this hypothesis, researchers proposed a new type of prestressed concrete composite slab with removable rectangular steel-tube lattice girders (referred to as CDB composite slabs), whose bottom plate consists of a temporary structure composed of a prestressed concrete prefabricated plate and removable rectangular steel-tube lattice girders. Through static bending performance tests on three prefabricated bottom plates and one composite slab, researchers measured corresponding load-displacement curves, load-strain curves, crack development, and distribution, etc. The test results show that the top chord rectangular steel tubes connected to the bottom plate concrete through web reinforcement bars significantly improve the rigidity, crack resistance, and load-bearing capacity of the bottom plate and possess better ductility and out-of-plane stability. The number of supports at the bottom of the bottom plate is effectively reduced, with the maximum unsupported span reaching 4.8 m. Beyond 4.8 m, only one additional support is needed, and the maximum support span can be up to 9.0 m, which provides space for cost reduction. The cooperative load-bearing performance of the prefabricated bottom plate and the post-cast composite layer concrete is good. The top chord rectangular steel tubes are easy to dismantle and can be reused, which reduces the steel consumption by about 24% compared to that used for the same size of ordinary steel-tube lattice-girder concrete composite slabs. It can greatly decrease the cost. In conclusion, the results have shown that the new method researchers proposed here is practically applicable and also provides great space to save on financial costs. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, cost-effective deployable tool for the construction of highly skewed and curved steel girder bridges that will provide the necessary geometrical adjustments to the adjacent girders for the fit-up and installation of cross-frames. This tool consists of two cables and one hydraulic jack and would be deployed near the location where a cross-frame needs to be installed. The jack would be extended or contracted to rotate the girders such that they are approximately parallel to one another to achieve the desired geometry for the installation of the cross-frame without requiring force-fitting. After the cross-frame is installed, the deployable tool would be released and reused elsewhere. This paper presents a numerical investigation of the efficacy of this deployable tool in facilitating the installation of cross-frames for two prototype bridges: a highly skewed and a curved steel girder prototype bridge. Three-dimensional (3D) finite-element (FE) analyses of the prototype bridges under steel dead load at the construction increment just before the cross-frames would be installed were performed to first understand the challenges in cross-frame fit-up. The deployable tool was then incorporated into the developed FE model to determine the forces in the system throughout its deployment and the installation of the cross-frames. A control sequence for the deployment was developed and evaluated. For the prototype bridges considered in this research, the peak force in the hydraulic jack was 26.6 kN (5.97 k), meaning that off-the-shelf technologies could be used. The peak von Mises stress in the installed cross-frame was 22.4 MPa (3.25 ksi), indicating that the procedure is not overstressing the system. Overall, this research demonstrates the promise of a new tool to facilitate cross-frame installation in highly skewed and curved steel girder bridges and culminates in recommendations on the use of this technology in the field. [ABSTRACT FROM AUTHOR]