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]

In this study, experimental natural frequencies and mid-span deflections were used to assess the tested composite floors against vibration serviceability limit states adopted by different standards such as AS3623. It was found that existing design criteria have predicted inconsistent results. Further, the finite element (FE) model was created, updated, and validated against the experimental modal parameters. The validated numerical model examined how various design parameters, such as material properties, cross-section geometry, and achieved a degree of composite action, have influenced the vibration properties such as natural frequencies and mode shapes. It was shown that as the added mass became more dominant than the stiffness enhancement, the fundamental natural frequency of the floor system dropped. This was evident from the results of the plywood slab thickness and the added permanent load parameters. On the other hand, the fundamental natural frequency increased with thicker and deeper joist sections since they made the floor system stiffer. [ABSTRACT FROM AUTHOR]

This article presents a new data-driven reliability analysis framework through combining the sample convolution and interaction network (SCINet) with Bayesian probability recursion to predict the time-variant reliability of bridge girders. The structural response predicted by SCINet and the state parameter (i.e., the variance of normal distribution) estimated by Bayesian dynamic linear model (BDLM) are used to form the limit state function to predict time-variant reliability. The results with a practical bridge show that the proposed method can predict future structural responses and time-variant reliability more accurately than BDLM, long short-term memory (LSTM), and long- and short-term time-series network (LSTNet) methods. [ABSTRACT FROM AUTHOR]

The primary requirement for vibration-based structural damage identification is to develop the damage index with higher damage sensitivity. Although it is believed that higher order mode means more sensitivity to damage, what is the quantitative relationship between damage sensitivity of different orders and how to carry out multi-mode fusion lack theoretical guidance. This paper implements the comparison study of the location-related damage sensitivity for different mode shape curvatures and then proposes a structural damage index with sensitivity enhancement for beam structure. First, the damage sensitivity of the mode shape curvature of beam structures at different orders is compared in theory. It reveals that the damage sensitivity is location-dependent, and the second-order mode in the even 16.6% region is more sensitive than the third-order mode in the simply supported beam. Second, a structural damage index with sensitivity enhancement for beam structure is proposed according to the relationship between the damage sensitivity of mode shape curvature at different orders and locations. Third, a simply supported beam model and a steel stringer bridge model with multiple main girders are both investigated to illustrate the comparison results of the damage sensitivity at different orders and the advantages of the proposed structural damage index. It shows that the confused damage sensitivities are very common between different mode orders, the sensitivity-enhanced damage index that considers the damage location always shows certain degree of improvement of damage indication ability in different damage areas. Finally, the effectiveness and accessibility of the proposed method are verified by a simply supported beam experiment. [ABSTRACT FROM AUTHOR]

This study addressed the issue of distortion in evaluating the seismic damage state of railway bridge piers using the original Park-Ang damage index. By constructing a parameterized co-simulation program with two finite element models, OpenSees and Abaqus, five sets of flexural failure and five sets of flexural-shear failure rectangular pier quasi-static test results were selected to validate the rationality of the calculation program. Four hundred and eighty parameterized calculations were conducted using this program. The combination coefficient β and critical damage index DI within the Park-Ang damage index were modified using nonlinear regression algorithm and convolutional neural network algorithm. The adaptability of the damage index calculation was ultimately verified through an engineering case study of a simply supported beam bridge. The research findings are as follows: 1) The main factor influencing β is the longitudinal reinforcement ratio, while the axial compression ratio, shear span ratio, volumetric stirrup ratio, aspect ratio, concrete strength, and steel strength are secondary parameters influencing β. 2) Compared to the nonlinear regression algorithm, the convolutional neural network algorithm can better establish a calculation model between pier structural parameters and β, clarifying their relationship. 3) It is recommended to use critical values of 0.11, 0.29, 0.49, and 1.00 for assessing pier damage as no, slight, moderate, severe, and collapse damage when using the damage index calculation model. 4) The Park-Ang index corrected by convolutional neural networks demonstrates improved accuracy and computational stability, making it suitable for practical assessment of seismic damage in bridge structures. Highlights: The original Park-Ang damage index has been modified to suit railway rectangular bridge piers. The possibility of flexural-shear failure in railway bridge piers has also been taken into consideration. In addition to the nonlinear regression algorithm, a convolutional neural network algorithm has been applied in the construction of the damage index calculation model. A simple supported beam bridge engineering case has been used to validate the applicability of the damage index calculations. [ABSTRACT FROM AUTHOR]

In the present study, an improved design method is proposed for the flexural design of steel plate I‐girders at elevated temperatures. The proposed method accounts for two important phenomena accompanying the temperature increase in steel I‐girders: (1) alteration of the failure mode and (2) degradation of the material properties. The main strategy of the proposed procedure is to find the ambient‐temperature‐equivalent design parameters of steel I‐girders at elevated temperatures. The basic design relationships are adopted from the flexural design provisions of AISC 360‐16 and then modified to accommodate the elevated temperatures and instability conditions of I‐girders. To evaluate the accuracy and efficiency of the proposed method, a comprehensive finite element study is conducted using ABAQUS. To this aim, 54 numerical models of steel plate I‐girders with different cross‐section slenderness parameters were investigated. All the simulated I‐girders were prone to fail in elastic lateral‐torsional buckling mode at both ambient temperature and elevated temperatures. To corroborate the numerical modeling and analysis process at ambient and elevated temperatures, the results were verified against the available experimental data. Based on the results, the maximum absolute deviation of the ultimate flexural strength obtained from the proposed method from the finite element predictions was 9%. [ABSTRACT FROM AUTHOR]

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

Bridges situated in northern climate regions, which face severe environmental conditions and daily fatigue loading, are prone to accelerated deterioration and corrosion of their components. The application of carbon fiber–reinforced polymer (CFRP) sheets bonding to the surface of bridge elements has emerged as an attractive solution for enhancing bridge strength. Past studies and field implementations have effectively showcased the viability of this approach in strengthening bridges. An exceptional opportunity arises with the deconstruction of a bridge in Canada, providing a unique chance to assess and study the condition of reinforced concrete elements strengthened with CFRP. These elements have endured real service conditions, including fatigue loads and exposure to aggressive environmental factors. This paper presents the experimental results of a research program that aimed to investigate the residual fatigue life and capacity of 60-year-old reinforced concrete bridge girders, which were strengthened using CFRP sheets. The study focuses on assessing the performance of these girders under different test conditions, providing valuable insights into their remaining fatigue life and load-carrying capabilities. The two 60-year-old girders have been strengthened with CFRP for the last 10 years of the service life of the bridge. The two full-scale girders were tested under 2 million fatigue load cycles and then tested monotonically until failure at the structural lab of the University of Sherbrooke. The test results revealed that the CFRP-strengthening technique can extend the service life of the bridge element and enhance its shear capacity. The CFRP–concrete interface and CFRP sheets showed excellent bonding behavior, as no damage-debonding failure or tensile rupture occurred until the formation of the diagonal shear crack. [ABSTRACT FROM AUTHOR]

Bridge bending stiffness, related to bridge material and geometric properties, is considered an important indicator of bridge performance. Accurately identifying bridge bending stiffness is essential for evaluating the condition of the bridge. The bridge influence line (IL), which can reflect the bending stiffness, is widely used for bending stiffness identification. The most frequently employed IL is deflection IL, which is typically extracted from the deflection response of the midspan section. In practice, a fixed reference point below the midspan section is usually unavailable, thus limiting the application of deflection measurements. Furthermore, existing methods primarily focus on simply supported girder bridges, which are not applicable to continuous girder bridges. This paper proposes a method for identifying the bending stiffness of continuous girder bridges by using multiple rotation influence lines (RILs) of the section near the bearing. The rotation responses of the section near the bearing are measured for RIL extraction since the bearing has a platform for sensor fixation and overcomes the limitation of deflection measurements. The distribution functions are introduced for simulating bending stiffness, and their parameters are estimated by an optimization algorithm using multiple RILs. This approach leverages multiple measurement points and is more accurate than the method using a single RIL. The effectiveness of the proposed method for identifying bridge bending stiffness is verified by both numerical simulations and laboratory experiments. A comparison between the identified bending stiffness using multiple RILs and that using a single RIL assesses the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

For strengthening punching shear endangered areas, both (1) punching shear reinforcement such as stirrups, headed studs or lattice girders and (2) the use of steel fiber‐reinforced concrete (SFRC) have been investigated and applied for many years. In contrast, the combination of both of these strengthening methods is way less investigated and there are mainly studies on slabs with stirrups or headed studs in combination with SFRC which show a high potential for increasing the load‐bearing capacity for the same slab geometry. Relevant investigations with other types of punching shear reinforcement in combination with SFRC are not known. In order to fill this gap, four full‐scale tests were performed on slabs made of SFRC combined with a high‐performance punching shear reinforcement (Filigran FDB). These tests are based on a plain concrete benchmark test with FDB punching shear reinforcement from the literature. The present paper describes and discusses the design, execution, key results and lessons learnt from these experimental tests. The addition of steel fibers strengthens the punching shear reinforcement, leads to smaller crack widths, and increases the ductility of the compression zone around the column. This results in significantly higher punching shear resistance. While the tested punching shear reinforcement (FDB) increases the resistance of the plain concrete benchmark test to 2.16 times the resistance of plain concrete without shear reinforcement (VRk,c), the addition of steel fibers in the tests shows resistances up to 2.79 · VRk,c. Thus, the additional increase due to the fibers was up to 30%. [ABSTRACT FROM AUTHOR]

Web buckling of steel plate girders creates an undesirable failure mode as it can limit the ultimate load capacity of plate girders. This paper presents details of an experimental investigation aimed at strengthening slender end panels of steel plate girders using three different types of fibre-reinforced polymer (FRP) composite materials (glass-fibre-reinforced polymer (GFRP) pultruded section stiffeners and woven carbon-fibre-reinforced polymer (CFRP) and GFRP fabrics). The plate girders were fabricated using non-rigid end posts and were tested in three-point bending. The test results showed an increase of up to 54% in the ultimate strength of the FRP-strengthened end panels compared with the non-strengthened control panel, which was the result of increased out-of-plane stiffness of the web. A breakdown of the bond between the steel and the FRP fabric occurred in the end panels strengthened with CFRP and GFRP fabrics, while no bond breakdown of the pultruded sections was observed at the ultimate load. Analytical methods proposed by some of the design codes underestimated the critical buckling load and overestimated the ultimate load of the non-strengthened end panel. [ABSTRACT FROM AUTHOR]

A numerical experiment is performed to evaluate the behaviour of externally pre-stressed steel–concrete composite beams (EPSCCBs) up to their ultimate stages, considering second-order effects, tendon material and friction at tendon–deviator locations. The tendon force evolution with loading and slip at the steel–concrete interface is explored. A three-dimensional finite-element model is used to include all these aspects. The idea is to deconstruct the project of eight experimental EPSCCBs with different tendon profiles, considering the above-mentioned issues. The main findings indicate that the inclusion of second-order effects is essential for predicting the stress paths near the collapse loads and slip demands at the steel–concrete interface, while external tendons made of carbon fibre-reinforced polymer (CFRP) can be used as a substitute for classical steel ones, as they presented similar behaviours. The largest tendon force increments occurred for the CFRP tendons compared to other tendons made of glass, aramid and basalt fibre-reinforced polymers. Furthermore, it was found that a friction coefficient between 0.2 and 0.4 at the tendon–deviator interface better matches the available experimental tendon force evolution with loading. This finding seems to counteract the common assumption of using a null friction coefficient as suggested in other works. [ABSTRACT FROM AUTHOR]

High-strength steels (HSSs) have been gaining increasing attention in recent years because of their potential application for lightweight structures. Hybrid structural steel I-sections, featured by dissimilar strength grades for constitutive plates, provide a more economical solution to suit bending loading scenario. This study conducted experiments on nine I-sections with Q690 flange plates under four-point loads, incorporating three different web strength grades including Q690, Q460, and Q355. Furthermore, the local buckling behavior of representative I-sections with various section geometries was analyzed using a validated numerical method to understand the role of web strength grade. Test and numerical analysis results revealed that the section with web steel in the strain hardening stage exhibited different levels of ductility among specimens with different strength webs. It was also observed that earlier yielding or inelastic buckling of the lower strength web plate in hybrid I-sections affects the local buckling behavior of I-girders, in terms of moment resistance and rotation capacity. In addition, the initial local imperfection mode used in numerical analysis was found to affect the rotation capacity of I-girders, but the effect of web strength grade remains consistent among I-sections with the same local buckling deformation mode. This study provides further insights into the local buckling behavior of hybrid I-sections subjected to uniform bending, laying the foundation for further development of design methods. [ABSTRACT FROM AUTHOR]

Aiming at the high-speed railway (HSR)-China Railway Track System III (CRTS III) slab ballastless track (SBT)-simply-supported bridge system, the mapping relationship between girder deformation and rail deformation had been deduced theoretically, and then, the additional irregularity of the rail was obtained. A dynamic model of the high-speed train-track-bridge (TTB) coupling system was established according to existing theory on the high-speed TTB dynamic interactions. Combined with the mapping relationship, taking the superposition of the additional irregularity and the random irregularity as excitation, the dynamic response of two train models (CRH2 and ICE3 trains) was analysed by using the high-speed TTB coupling system model. The recommended thresholds of girder deformation were given based on running safety and ride comfort indicators. The results show that the sensitivities of the two train models exposed to girder deformation were different, and the CRH2 train was more sensitive to the lateral girder deformation. The non-uniform dislocation deformation of multiple girders exerted a slightly more significant effect on the dynamic characteristics of two train models than the dislocation deformation of single girder. Under the same amplitude of girder deformation, the influences of vertical girder dislocation and vertical girder rotation on the running safety and ride comfort of trains were significantly greater than that of lateral girder dislocation and lateral girder rotation. Acceleration and wheel-rail force increase rapidly in the area of girder deformation. To guarantee running safety and ride comfort of trains, this paper proposes suggested values for girder deformation thresholds. [ABSTRACT FROM AUTHOR]

The key to understanding the shear failure mechanism of prestressed concrete girders lies in how to properly deal with the combined effects of the applied load, the support reaction, as well as the prestressing force. This paper firstly conceptualizes a combined stress field model, which integrates these effects by manifesting several subfields to disclose the potential failure patterns at different locations in the short shear span. Then, shear tests of four full-scale pretensioned concrete T-girders with a height of 1.6 m and two kinds of shear-span-to-depth ratios were carried out. The test results showed that all the specimens failed in a web-crushing pattern near the support accompanied by a bond-slip of the deflected strands. By analyzing the deviated compression subfields in the highly stressed webs and introducing a failure criterion for cracked concrete, the ultimate shear strength of pretensioned concrete girders was formulated. Finally, the shear strength evaluated by the proposed formula and by some other design codes were compared, and it was proved that the results of the proposed model were closer to the test. [ABSTRACT FROM AUTHOR]

The subject of the research presented in this article is the dimensional optimisation of the box structure of the main girder for overhead cranes, with the aim to reduce the main girder's own weight. Described are the applied optimisation methods and also the problems arising during the optimisation process. Loss of shape stability is analysed in more detail, as well as the methods determined for a constructional proposal of the girder cross-section. The developed optimisation procedure is a combination of the calculations, performed in the MS Excel environment, with the simulation of a parametrically modelled girder realised using Dassault Systèmes SolidWorks software v. 2023. Using the example of optimisation of an overhead crane girder with a lifting capacity of 50 tons, the effectiveness of the proposed optimisation procedure is declared, where the existing overhead crane box girder is compared with the optimised cross-section of the box girder. [ABSTRACT FROM AUTHOR]

Road infrastructure development in Indonesia has increased the use of long-span prestressed concrete I-section (PCI) girders for bridge structures. However, these girders have instability issues during construction that resulted in multiple failures between 2017 and mid-2018. To address this problem, engineers compiled a standard guideline for erecting long-span PCI girders that includes three recommendations: a lifting point or lifting frame, a dapped-end girder, and artificial stiffeners. In late 2022, despite the initial effectiveness of the guideline, a video revealed that PCI girders were still vulnerable to failure despite strict adherence to the guidelines. A subsequent study reviewed the guidelines and revealed that not all the guidance was effective. The study emphasized the importance of standardized bracing at the supports. Therefore, it is necessary to revise and improve the guidelines to prevent similar failures in the future. Practical Applications: The process of erecting long-span prestressed concrete I-section (PCI) girders, which are more than 40 m long, is risky and can lead to toppling and collapsing. The main cause of this risk is the presence of lateral imperfections, which are limited to length or span of the girder (L)/500 (maximum) due to construction tolerances and the lateral stiffness being relatively small. Therefore, the process of erection must be carried out carefully and purposefully. To reduce the risk of accidents, a standard guideline for erection (SGE) was created. However, although the SGE (2018, 2021) has successfully reduced accidents, failures still happen. There are weaknesses in the SGE that need to be corrected. There are two critical risk stages during the erection of a PCI girder: the hanging and seated conditions. Using a lifting frame, according to the SGE (2018, 2021), is correct for the hanging stage. However, the seating procedure in the SGE needs improvement. It is vital to ensure that the strength of the bracing at the supports is standardized and installed correctly before removing the lifting crane. The reasons for this recommendation are explained in this paper. [ABSTRACT FROM AUTHOR]

Steel plate girders are susceptible to web buckling due to slender web. This phenomenon creates an undesirable failure mode and limits their ultimate load capacity. The use of fiber-reinforced polymer (FRP) composite materials offers a good prospect of strengthening the slender web of plate girders to avoid web buckling. This paper presents the details of experimental testing of steel plate girders with nonrigid end posts. These girders were tested in three-point bending. The end shear panels of the girders were strengthened by glass FRP (GFRP) pultruded section stiffeners or glass fiber fabric composite. GFRP stiffeners were applied either vertically or along the compression diagonal in the shear panel. All strengthened panels failed by web shear buckling associated with a breakdown of the employed strengthening scheme. It was found that the shear capacity of the panel remained unchanged by replacing the steel stiffener with GFRP stiffeners in the end panel. The critical buckling load of the strengthened panels increased up to 44% compared to the unstrengthened panel. The shear capacities of the panels strengthened by the glass fabric composite and diagonal GFRP pultruded section were the highest and similar to each other. Both these panels resisted a 50% larger shear compared to the unstrengthened panel. The positions of the plastic hinges in all tested panels were the same due to the same ratio of panel length and depth of the web. [ABSTRACT FROM AUTHOR]

Beam shaping and polarization manipulation are of great importance for the design of microcavity lasers. Recently, topological photonic cavities have emerged as excellent platforms for surface-emitting lasers. In this class of lasers, beam engineering has not thus far been extensively studied. Here, we demonstrate how to achieve an intrinsic lateral shift of the beam emitted by a topological laser. This is achieved by designing a Kekulé-modulated topological bulk cavity, in which the continuous Kekulé modulation partially lifts a set of fourfold-degenerate Dirac cones into two twofold degeneracies. The resulting photonic cavity supports a range of interesting beam emission profiles, including vector beams with polarization winding, and laterally-shifted linearly-polarized Gaussian beams. It is possible to achieve lateral beam shifts in opposite directions and orthogonal polarizations for the degenerate photonic p-/d-orbitals, a feature that may be useful for photonic sensing applications. Topological phenomena in photonics have been found of great importance in realizing advanced semiconductor laser. Here the authors demonstrate the manipulation of the light emission profiles from a Kekulé-modulated topological bulk cavity in a topological-protection manner, where the achieved lateral beam shifts in light polarizations could be useful for the laser design and photonic sensing applications. [ABSTRACT FROM AUTHOR]

In order to study the influence of the lifting force arrangement on the mechanical performance of the long-span steel-concrete composite girder which using the lifting-composing construction method, based on the Qinhe grand bridge along the Taihang expressway, the effects of different first and secondary lifting force, the number and distance of lifting points on the stress, deformation, stability, and bridge deck compressive stress reserve of the steel-concrete composite girder were studied by using the Midas-Civil finite element software and a control variable method. The sensitivity of different factors on the steel-concrete composite girder was analyzed through variable normalization, moreover, the optimal scheme was selected, and the implementation effect was monitored on site. The results show that the stress of upper flange of the steel girder, bridge deck, and bridge deflection are most sensitive to the secondary lifting force, with sensitivities of 0.61, 1.95, and 0.16, respectively. The stress of lower flange of the steel girder is most sensitive to the number of lifting points, with a sensitivity of 0.20. The theoretical optimal pre-bending of Qinhe grand bridge is 78%, the final scheme arranges 5 groups of lifting points with distance of 11 m, and the first and the secondary lifting forces are 1 500 kN and 6 500 kN, respectively. The on-site monitoring results show that the construction effect of the scheme is consistent with the theoretical analysis results, and the on-site lifting force is reasonably arranged. The on-site monitoring results show that the implementation effect of the scheme is consistent with the theoretical analysis, and the lifting force is reasonably arranged. The research results can provide reference for similar projects. [ABSTRACT FROM AUTHOR]

In the degradation evaluation process of the crane girder structure under moving loads, the complex vibration response and low accuracy of health index standards are the main factors limiting the performance of the evaluation method. A method for identifying and evaluating damage to crane girder structures under moving loads has been proposed. In this method, optimized empirical wavelet transform (EWT) is used for decomposing the vibration signal of the crane girder structure to obtain sensitive components. A health indicator based on power spectrum maximum sequence is constructed by combining structural vibration simulation and response characteristics analysis under moving loads. A degradation index acquisition scheme based on an optimized sparse autoencoder is proposed, which utilizes a simulated annealing algorithm to optimize the model parameters of the sparse autoencoder. The effectiveness of the proposed method is verified through girder structure crack tests under moving loads. [ABSTRACT FROM AUTHOR]

This study investigates the blast-resistant performance of a polyurea-coated suspension bridge girder under explosive loads. The Hunan Road Bridge of Shandong was used as a case study through combined test and numerical simulation methods. Two 3 kg TNT charges and one 5 kg TNT charge were used to conduct two single-blast tests and one repeated blast test on a 1:3 scaled segment of a box girder. The tests were labeled as G (box girder without polyurea), PCG (first blast on box girder coated with polyurea), and PCGR (second blast on box girder coated with polyurea). A 1.5 mm polyurea layer was uniformly applied to the top surface. Numerical simulations of the explosion response were performed and validated using LS-DYNA software. The results indicate that under 3 kg of TNT detonation directly above the top plate, sample G exhibited an elliptical perforation, whereas sample PCG only experienced minor local dents without penetration. After a second detonation of 5 kg of TNT above the box chambers, sample PCGR displayed a nearly circular perforation in the top plate, along with cracks near the supports of chambers 1 and 3. For the main girder of the suspension bridge, multiple detonation points caused severe damage, rendering it impassable. However, after polyurea coating, the blast resistance significantly improved, with only minor spalling of concrete on the top plate and no other notable damage, allowing for continued passage. The polyurea layer effectively reduced the vertical displacement of the girder, and this reduction plateaued with increasing coating thickness. Under a 500 kg TNT blast, the optimal polyurea thickness to enhance blast resistance was determined to be 9 mm. [ABSTRACT FROM AUTHOR]

This paper presents the effects of angles of attack (AOA) on the windproof effect of wind barriers and the driving safety of highway vehicles on a wide bridge girder. The aerodynamic force coefficients of the vehicles were obtained using the force measurement technique. Computational fluid dynamics simulations were employed to investigate the mean wind velocity field on the upper surface of the girder. A comparison was made between the aerodynamic forces on a vehicle at various AOA on a bridge deck with guardrails and a deck with wind barriers. The windproof effect of wind barriers at various AOA was accessed by the safety factor of a vehicle. The results showed that the maximum of the aerodynamic forces of vehicles was not typically observed at a 0° AOA. The windproof effect of wind barriers became more pronounced as the magnitude of the AOA increased. As AOA increases, the height of the low wind velocity zone above the deck shows an upward trend. Compared to the deck with the guardrails, the height of the low wind velocity zone was much higher in the presence of wind barriers. The increase in the height of the low wind velocity zone will result in a decrease in the aerodynamic side force and an increase in the rolling moment acting on vehicles. It is also noteworthy that the installation of wind barriers can cause a reduction of overturning and side-slip safety factors of vehicles at specific AOA. This suggests that the wind barrier may potentially compromise driving safety at specific AOA. [ABSTRACT FROM AUTHOR]

Steel‐concrete composite box girders offer notable advantages such as high stiffness, excellent torsional performance, and light self‐weight, making them prevalent in large‐span bridges, particularly in cable‐stayed configurations. However, a persistent challenge arises from the shear lag effect in the concrete slab within the flanges induced by shearing interactions between the webs and flanges. Limited attention has been devoted to investigating the experimental and theoretical aspects of shear lag in long‐span cable‐stayed bridges with twin box‐shaped composite girders. This research addresses this gap by designing a segmental scale twin box‐shaped composite model specimen to simulate the cable spacing of the main girder in a cable‐stayed bridge, specifically targeting the shear‐lag effect. The study successfully captures the non‐uniform distribution of cross‐sectional strain in the top concrete slab. Subsequently, analytical strain solutions for the composite girder under mid‐span concentrated load and axial load are derived using the energy variation method. The theoretical model's applicability is then calibrated against experimental results. The investigation extends to the in‐situ testing of the Chibi Yangtze River Bridge, the world's largest steel‐concrete composite girder cable‐stayed bridge, boasting a main span of up to 720 m. An established finite element (FE) analysis model for the Chibi Yangtze River Bridge simulates the transverse stress distribution under typical construction conditions of CC6. Comparative analyses between the simulated results, calculated values from elementary beam theory, and the theoretical model against field‐measured values reveal that the FE model provides a more accurate estimation of the shear lag effect in the concrete slab. Notably, the FE model effectively reflects the bridge's characteristics and serves as a baseline for subsequent studies. This comprehensive investigation contributes significantly to the understanding and analysis of shear lag phenomena in twin box composite girders of cable‐stayed bridges. The integration of experimental, analytical, and construction site validations establishes robust tools for engineering design and the construction of safe and serviceable cable‐stayed bridges. The research augments knowledge regarding shear lag behavior and underscores the necessity to appropriately consider its effects in bridge analysis and design. [ABSTRACT FROM AUTHOR]

The bridge models reconstructed from unmanned aerial vehicle (UAV) images via photogrammetry are often reported to have quality issues (e.g., high noise, insufficient resolution and precision loss) and thus restrict their application in bridge inspection. To address this problem, this paper proposes a novel Building Information Model (BIM)-based 3D path planning method for improving the quality of photogrammetric bridge models by optimising the UAV flight plan. This method firstly uses a simple BIM model as input and considers inspection and photogrammetry requirements to generate effective UAV viewpoints. Then it adjusts inaccessible UAV viewpoints that are in occupied space or cannot meet the flight safety rules. Finally, a feasible flight trajectory is generated through all valid viewpoints. To evaluate the performance of the proposed method, two prototypes were developed to automate the path planning and on-site image acquisition, respectively, and were tested on a real girder bridge. The results showed that, compared with the common UAV flight plan used in current practice, the proposed method could: (1) generate a more precise bridge model with fewer noise points and higher visual quality to support damage detection; and (2) significantly improve the efficiency of photogrammetric 3D bridge reconstruction with reduced human interventions in image collection and processing. [ABSTRACT FROM AUTHOR]

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

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

Typical forms of seismic damage to laminated-rubber-bearing girder bridges in the transverse direction are falling beams, girder displacement, and bearing damage. However, the damage to piers and foundations is generally lighter. This is mainly due to slippage of the bearings. Therefore, we propose a new type of arc-shaped shear key to improve the lateral seismic performance. A 1/12-scale highway continuous-girder bridge isolated by different shear keys was tested utilizing a 4 m × 4 m shaking table with six DOFs. The seismic responses of the bridge were analyzed in terms of phenomenon, displacement, strain, and acceleration. The main girder and pier exhibited different seismic responses because the bridge had different stops. A numerical simulation based on FEM showed that the established finite element model can well reproduce the displacement time history of the main girder and the cap girder. By analyzing the finite element model, the relative displacement of the bearing under different seismic waves was obtained. A comparison between the measured and FEM responses showed that the arc-shaped shear key can well limit the displacement of the main girder and the bearing. In addition, it does not significantly amplify the seismic response of the substructure. The arc-shaped shear key dissipates more energy while limiting the displacement of the main girder, and the comprehensive seismic performance is better than that of the rubber pad shear key. [ABSTRACT FROM AUTHOR]

Steel truss bridges are especially vulnerable in the event of a sudden loss of a load-carrying element, which can trigger a chain of failures. This paper describes a unique case study of a steel truss bridge under construction subjected to sudden member breakages with an extensive monitoring system. The failures occurred during the dismantlement of temporary members that had been used to transform a three-span simply supported steel truss bridge into a three-span continuous structure during incremental launching. These temporary members needed to be removed once the bridge reached its final position. The robustness of the bridge was assessed using computer simulations of various failure scenarios to evaluate its capacity to effectively activate alternative load paths (ALPs). The results demonstrated the structural redundancy of the steel truss bridge. However, the dynamic response resulting from the failure of the temporary upper chord, due to the initially high tension in the rods, should not be overlooked. To mitigate this issue, a structural retrofitting method was proposed, involving jacking the truss girder above the side pier to reduce the tension in the temporary upper chord above the middle pier. The effectiveness of this method was demonstrated through both simulated and formal experimental tests. [ABSTRACT FROM AUTHOR]

A full-scale hybrid beam consisting of a UHPC slab and FRP truss girder was fabricated. The novel side plate FRP joint characterized with improved loadcarrying capacity, stiffness, and preferred failure mode along with the tailored shear connector validated in the previous studies of the authors were adopted. Its flexural performance was characterized and compared with that of hybrid beams employing NC or UHPC slab but I-profile girder. The failure of the proposed hybrid beam subjected to bending was pseudo ductile whereas those of the other two hybrid beams were brittle. The load-carrying capacity and stiffness of the proposed hybrid beam outperformed the other two hybrid beams with comparable dimensions and material properties. [ABSTRACT FROM AUTHOR]

The guideway’s alignment deviations are of concern when assessing the vibrations of high-speed maglev transportation systems. Among these, the deformation of the guideway due to solar thermal effects is a critical issue impacting the operational efficiency of a maglev train running on a guideway system. To address this issue, this study integrates solar radiation, shadow masking, heat convection and radiative heat transfer to present a thermal-mechanical coupling model for investigating the temperature-deformation field of guideway girders. Meanwhile, on-site measurements are conducted to confirm the feasibility of using temperature field distribution to estimate the thermal deformation of guideway girders. A solar-thermal field formula suitable for a maglev vehicle-guideway system is proposed to estimate the temperature field distribution on the guideway girders by referencing the formulas in the known specifications. Finally, this paper introduces an electromagnetic feedback controller that adjusts the maglev forces using real-time thermal deformation data to mitigate the effects of solar thermal-induced guideway deformation on the maglev vehicle-guideway system, demonstrating that the dynamic response of a maglev train is significantly influenced by the thermal deformation of guideway girders due to sensitive variations in levitation gaps. [ABSTRACT FROM AUTHOR]

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

The wind-resistant performance of cable-stayed bridges under construction deteriorates sharply as the cantilever length increases, and the arrangement of the temporary pier is an effective measure to improve aerodynamic stability. To investigate the effect of the temporary pier on buffeting response of a long-span three-tower cable-stayed bridge under construction, the nonlinear buffeting analysis and wind tunnel test of aeroelastic model methods are adopted in this paper. The influence of the type and arrangement positions of temporary piers on mean wind response and the nonlinear buffeting response of double-cantilever construction are studied, and the arrangement of the temporary pier is optimized based on the buffeting response. The results show that the reduction rates of the RMS of the torsional moment at the tower bottom and the lateral buffeting displacement at the girder end with the rigid pier are 35.6% and 59.2% compared to those without the temporary pier. Further, the buffeting response will decrease as the distance between the rigid pier and the tower increases in the state. On the contrary, in the double-cantilever construction state before the constraint of temporary piers, the buffeting response will become significant as the distance increases. Therefore, it is necessary to consider the buffeting response under two construction states when optimizing the arrangement position of the temporary pier. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive finite element analysis (FEA) of pre-stressed Ultra High-Performance Concrete (UHPC) girders, showcasing intricate structural behaviors under various loading conditions. Utilizing advanced finite element modeling techniques, the study accurately simulates the flexural response of UHPC girders, integrating experimental results from large-scale laboratory tests conducted by researchers at the Turner-Fairbank Highway Research Center. This paper shows the effectiveness of simulating pre-stressing forces via initial equivalent temperature load with relatively accurate stress and strain predictions. The paper also delves into the moment–deflection relationships at critical stages, such as first concrete crack appearance, yielding, and strain localization, to capture the non-linear behavior of UHPC girders under pre-stressed conditions. Additionally, crack propagations were characterized by investigating the damage in tension (DAMAGET) plots. In summary, the results of the finite element model agree well with the experimental observations. Moreover, this study not only demonstrates the effectiveness of FEA in accurately simulating the complex structural behaviors of UHPC girders but also highlights its broader applicability to the design and analysis of other girder types, offering valuable insights compared to ordinary concrete beams. [ABSTRACT FROM AUTHOR]

A new consolidation system for prestressed reinforced concrete (PSRC) beams of girder bridges is presented and evaluated. The system consists of two arch-shaped steel trusses placed alongside the lateral faces of the beam to be consolidated. The arches develop longitudinally along the entire span of the beam and in elevation using the available height of the PSRC cross-section. The consolidation system is characterised by its own external constraints, independent from those serving the pre-existing element. The efficiency of the system with respect to variable parameters is examined, focusing on the ratio between the load discharged by the consolidation system and the total applied load. Referring to a case study, consolidation of a PSRC beam adopting the proposed system is compared with the usually adopted external prestressing technique. The cross-sectional properties of the steel arch-shaped trusses are defined by means of a structural optimisation process using a genetic algorithm to identify the minimum steel consumption. Finally, a preliminary cost–benefit analysis is performed for the proposed solution and compared with other commonly adopted techniques. [ABSTRACT FROM AUTHOR]

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

Although ultra-high-performance concrete (UHPC) is one of the promising materials for precast bridge girder applications due to its advanced properties and durability, its implementation in the precast industry is subject to several potential concerns. To support implementation, this paper presents the development of nonproprietary UHPC mixtures for precast, pretensioned UHPC bridge girder applications. The nonproprietary UHPC mixtures were developed using materials commonly available in the Texas precast industry, with the additional requirement of obtaining a compressive strength of 12 to 14 ksi (83 to 97 MPa) within 24 hours without any heat treatment while maintaining the current precast, pretensioned bridge girder fabrication practices. The fresh, hardened, and durability properties of both laboratory- and plant-made UHPC mixtures were investigated. The research results show that the selected nonproprietary UHPC mixture developed in a laboratory setting can be successfully produced in a precast plant setting with comparable properties. [ABSTRACT FROM AUTHOR]

Steel bridge designers and erectors primarily rely on approximate methods, such as 1D line girder analyses and 2D grid analyses. For curved or skewed bridges, this can give erroneous indications of the structure's true behaviour. Refined methods of analysis, such as 3D shell modelling, aim to bring a significant change in the practice of bridge engineering. By moving the industry away from simplistic design assumptions, refined analysis methods lead to more accurate, less conservative results, which in turn brings true benefits such as improved structural safety and increased economy. In this paper, several case studies on curved plate girder and tub girder bridges are presented, which cover the full bridge life cycle, from erection of the steel structure and placement of the concrete deck, down to live load analyses using influence surfaces and load rating. The case studies will be modelled with mBrace3D, a dedicated FEA software for curved steel bridges. [ABSTRACT FROM AUTHOR]

The new railway line connecting Luxembourg and Bettembourg crosses the A3 highway at a steep angle (19.5°) with the bridge called OA14. The designed bridge is a bowstring structure with a single span of 186.85 meters. The bridge deck consists of two lateral metal box girders acting as a chord. The deck is a transversal filler beam, with spherical voids and lightweight concrete to reduce the structure's weight. The bridge features two inward‐inclined arches at 9°, which are doubled and serve as trusses. This significantly increases the stiffness of the arch whilst keeping the silhouette elegant. The deck follows the curved track alignment, the arches remain straight. Two times 12 hangers connect the arches to the girders, they are made of CHS profiles of S450H quality. This article gives an overview of the structure and its construction. It then gives a more detailed insight in the design of the hangers, especially the hanger‐girder connections. [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]

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

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

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

With the expanding application of lightweight wooden structures in modern construction, the load-bearing capacity of ordinary triangular single-span wooden trusses limits the applicability of lightweight wooden structures. As a result, triangular multi-span wooden trusses have emerged to replace single-span wooden trusses. In practice, multi-span wooden trusses are composed of multiple single-span lightweight wooden trusses, with connections between members using metal plates, a field that has been relatively well researched. However, connections between spans are primarily made with nails in actual engineering, and there has been little research on the use of wooden pins to connect multi-span wooden trusses. To study the mechanical performance of multi-span wooden trusses connected by wooden pins, this paper innovatively combines existing equipment with a self-designed pulley assembly device to conduct a continuous static full-scale loading test on double-span wooden trusses connected by wooden pins of three different diameters. We comprehensively evaluate which type of wooden pin is more suitable for triangular multi-span wooden trusses. The results indicate that the 16 mm diameter wooden pin provides the best energy dissipation performance for connected beam trusses. The 20 mm diameter wooden pin offers the best performance stability. The 20 mm diameter wooden pin also demonstrates a good load-bearing capacity and resistance to deformation. Overall, the 20 mm diameter wooden pin exhibits the best connection performance in triangular beam trusses. [ABSTRACT FROM AUTHOR]

This paper presents the implications of a hydrocarbon fire on the behavior of bridge girders prestressed with either steel strands or carbon fiber-reinforced polymer (CFRP) tendons. Stemming from a recent bridge fire that occurred in Lakewood, CO, numerical investigations are conducted employing a computational method called agent-based modeling to understand the intricate responses of these girders under thermomechanical loading. As the convection and radiation of surroundings are transformed to conductional thermal energy, the temperature of girder concrete rises, and the internal temperature differentials dwindle over time. Thermally induced damage in the prestressing elements is a function of distance from the surface heat. When loaded without thermal distress, the moment-carrying mechanism of the steel- and CFRP-prestressed girders is analogous; however, with the presence of heat, the development of lever arms and tensile strains of the girders demonstrates palpable differences. The maximum usable strains of the steel and CFRP vary with the degree of thermal exposure, thereby dominating the load-carrying capacity of the girders. From a design perspective, no evidence is noted to distinguish the performance of the steel- and CFRP-prestressed girders under service loadings, and contrary to commonplace notion, their fire ratings are found to be comparable because of sequential heat transfer. [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]