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Abstract: Measurement of short-term and long-term deflections is a necessary step towards understanding and evaluating the status of a bridge. In this paper, a novel non-contact weighted-stretched-wire (NCWSW) system is developed for measuring the deflection of a bridge. Also some factors related to the system are addressed. The proposed system is promising due to some attractive features such as high precision, low implementation cost and suitability for continuous monitoring. The efficiency and reliability of NCWSW system are investigated both analytically and experimentally. A realistic NCWSW system has been used in the monitoring of a real-world bridge. [Copyright &y& Elsevier]

• Monitor an onshore wind turbine for a long time. • Analyze vibration feature of wind turbine in different operational conditions. • Observe the resonance phenomenon by drawing the Campbell diagrams. • Discuss the relationship between modal parameters and operational conditions. A wind turbine structure works under the complicated environment and its operational state is complex. In this study, the operational state of a 1.5 MW wind turbine and the vibration response of the tower have been monitored for a long time. The vibration characteristic of the wind turbine under different operational conditions is discussed in detail, and it was observed that the rated rotation speed condition has the highest vibration level. The Campbell diagrams of wind turbine both in the FA direction and SS direction are drawn based on the natural frequencies results, which are identified by data-driven stochastic subspace identification method. It was observed from the Campbell diagrams that when the rotation speed is close to the grid-connected rotation speed, the blade-passing frequency 3 f (0.43 Hz) is equal to the fundamental frequency of wind turbine which will easily lead to the resonance. This phenomenon is confirmed by the time history diagrams of the operational condition and vibration speed of a certain startup process. Lastly, the relationship between first-order, second-order modal parameters and operational conditions of the wind turbine are discussed in detail respectively. The mean value of first-order natural frequency is affected slightly by the different operational conditions while the value of second-order natural frequency increases significantly with the increase of rotation speed. The work in this paper can help us to better understand the response of the wind turbine under different operational conditions, which can also lay the foundation for the structure design, modal validation and damage diagnosis of wind turbine. [ABSTRACT FROM AUTHOR]

Welded connectors are commonly utilized in steel-concrete composite construction. However, these connectors lack demountability, hindering the recycling or reuse of steel sections. In response to this limitation, high-strength bolts have been proposed as alternatives to traditional welded shear connectors to facilitate demountability. Nevertheless, the use of numerous high-strength bolts may negatively impact construction costs due to their limited capacity. This paper introduces a novel solution: the bolted angle shear connector. Comprising a standard angle section, a smaller size angle section functioning as a hat, and a high-strength bolt, this connector aims to balance the demountability advantage while avoiding the drawbacks associated with high-strength bolts. To assess its performance, the proposed connector was embedded into a solid concrete block, and horizontal pushout tests were conducted on 31 specimens. Variables considered included the angle section size, bolt diameter, bolt grade, concrete compressive strength, loading direction, and bolt thread condition. The findings reveal that the proposed connectors demonstrate a ductile response, meeting the mandated slip capacity of at least 6 mm according to EN 1994–1-1. Two distinct failure modes were observed: bolt fracture and a combination of concrete crushing and angle bending. The shear resistances at 6 mm slip ranged from 146 kN to 280 kN, influenced by the angle size and concrete compressive strength. Capacities were formulated as functions of these variables, leading to the development of design recommendations, which are presented in this paper. • Bolted angle shear connectors proposed for demountable construction. • Shear resistance investigated through 31 direct shear (push-out) tests. • Proposed connectors showed ductile behavior with slip capacity in excess of 6 mm. • Shear resistance varied between 146 kN and 280 kN. • Design recommendations were developed for the proposed connector. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on three-dimensional steel frame structures subjected to progressive collapse, drawing insights from a full-scale steel frame substructure test. The investigation encompasses connection component tests and numerical simulations, focusing on extended end plate and double-angle cleat connections employed in the substructure test. The mechanical properties of the connection components were tested, forming a basis for defining component properties in subsequent connection models. Finite element (FE) models of the test substructure were developed, utilizing hybrid elements for the steel frame part, which include beam, connector, and spring elements based on the component method. To simulate reinforced concrete slabs, a combination of refined solid elements and simplified shell elements was employed. The former accurately captures detailed failure modes, while the latter efficiently simulates the collapse behavior of large-scale steel frame structures. Validation of the established models against test results encompassed load-displacement responses, internal forces in structural members, and failure modes. The validated FE models were then utilized to analyze and discuss the contributions of various structural components in resisting progressive collapse. Specific focus was placed on the development of load-resisting mechanisms in the floor slab and the influence of beam-column connection types on structural behavior. The paper explores the role of bracing systems in a building in resisting progressive collapse. Additionally, it evaluates the effectiveness of the restraint systems used in the test, shedding light on their ability to accurately reflect real restraint effects from the surrounding structure. The findings presented herein contribute valuable insights to the understanding of progressive collapse behavior in steel frame structures, with implications for robustness design of multi-story steel buildings. • A novel component test method for extended end plate connection was proposed. • FE models of steel frame structures for progressive collapse were built and validated. • Contributions of structural members in resisting progressive collapse were clarified. • Evolutions of load-resisting mechanisms in floor slabs were explained. • Effects of beam-column connection types and bracing systems were discussed. [ABSTRACT FROM AUTHOR]

The investigation of the behavior of reinforced concrete (RC) elements without shear reinforcement is a current focal point, driven by the incomplete consolidation of predictive formulas for shear strength in RC elements. Currently, the literature provides, indeed, a limited number of experimental and numerical studies on this subject. This paper seeks to advance the comprehension of the behavior and collapse mechanisms of RC beams not provided of shear reinforcement, as commonly employed in RC slabs of bridges. The paper commences with a critical review of several predictive formulas for the shear strength of RC elements lacking transverse reinforcement, as stipulated by various international codes. The objective is to identify the principal parameters involved in the formulations and discuss their roles also by means of sensitivity analysis. Following this, the results of nonlinear numerical analyses, based on a three-dimensional finite element (FE) model, are presented. The FE model was initially calibrated using experimental results from a benchmark beam lacking shear reinforcement, retrieved from the literature, which exhibited a brittle shear failure. Subsequently, several specimens were prepared for the numerical investigation, assuming multiple combinations of geometrical and mechanical parameters. For specimens experiencing shear failure, the strength was compared with that provided by code formulas, as well as using the strut-and-tie approach for the cases characterized by a reduced shear span-to-depth ratio. In general, these analytical tools significantly underestimated the numerical strength, underscoring the necessity for further insights based on experimental tests. The numerical outcomes have been, indeed, prodromal to design an experimental campaign. • Finite element modeling of a reinforced concrete beam without shear reinforcement. • Review of all major approaches in technical regulations worldwide. • Parametric analysis of the shear behavior of reinforced concrete beams without transverse reinforcement. • Assessment of the predictive capacity of technical regulations formulations. [ABSTRACT FROM AUTHOR]

This paper focuses on addressing seismic safety evaluation and resilience analysis of nuclear containment structure. Through the derivation of fragility formulas and the introduction of a new set of limit states (LSs), this paper accomplishes the fragility analysis and assesses failure probabilities comprehensively. Furthermore, safety evaluation and resilience analysis procedures, specifically for nuclear containment, are proposed alongside relevant determination criteria. In order to further improve the seismic performance of nuclear containment, the periodic foundation is analyzed. Theoretical formula is derived to determine the combination of 2 materials (concrete and rubber). Key findings include the safety demonstration of HUALONG 1 through probabilistic reliability analysis, the safety level (Level-I; basic integrity) and resilience level (Level-I). The effectiveness of periodic foundations is confirmed and supported by the average damping rates of concrete and liner strains, which can reach up to 6.154 % and 11.007 %, respectively. This research provides valuable insights for improving the seismic safety and resilience of containment, crucial for ensuring the integrity and functionality of this critical infrastructure system. [ABSTRACT FROM AUTHOR]

The accurate assessment of cracked reinforced concrete structures is becoming increasingly more important as the world's infrastructure ages and resources for retrofit and replacement remain limited. While existing approaches can be used to predict crack information for comparisons with on-site observations, there remains a need to establish methods that use crack measurements as a direct input to assess residual structural capacity. Critical wide cracks have been observed in lightly reinforced deep beams leading to questions about the safety of concrete bridges. To assess such deep members, this paper answers three important questions: 1) which critical crack displacements should be measured?; 2) where should the critical crack displacements be measured?; and 3) what is the residual shear capacity of the member, given the measured critical crack displacements? To answer these questions, detailed data from large-scale experiments is examined and interpreted with the two-parameter kinematic theory (2PKT). The results illustrate the importance of vertical crack displacements for conducting assessments of lightly reinforced deep beams. The paper shows that when the measured crack shape is incorporated into the 2PKT, the residual capacity of deep beams can be determined from measured critical crack displacements. • Which critical crack displacements should be measured? • Where should the critical crack displacements be measured along the cracks? • How to assess the residual shear capacity of the member, given the measured critical crack displacements? • A crack-based framework is used to assess the residual capacity of large-scale deep beams • The unique feature is the use of measured crack geometry as input in the assessment [ABSTRACT FROM AUTHOR]

This paper presents a reliability analysis of concrete masonry infill walls with an aim to examine the efficacy of the resistance factor specified in the infill design under seismic loading. A numerical model for masonry infilled reinforced concrete frames was developed and encoded in OpenSees for this study. The model was validated using experimental data. Two features were involved in this reliability study, including 1) that the effect of spatially varying masonry compressive strength f ′ m on the lateral resistance of masonry infills was considered using the Random Finite Element Method, and 2) that seismic load with different return periods was considered to provide a more complete treatment of a reliability analysis. The study selected six Canadian cities with varying levels of seismic intensity for this analysis. By calculating the probability of failure of infill frames subjected to earthquake loading at different locations, the paper showed that the current resistance factor of 0.6 in the infill design equation suggested by the Canadian masonry design standard is conservative. To achieve a reliability index of 3, this factor could be increased to 0.65 for all cities studied. For cities with low seismicity such as Toronto, the results suggest that an even higher resistance factor is justified. • A meso-model encoded in OpenSees to simulate the in-plane behaviour of masonry infilled RC frames. • A reliability-based study on masonry infilled RC frames using the Random Finite Element Method (RFEM). • Considered spatially varied masonry compressive strength and seismic loads with varying return periods. • Calibrate the resistance factor specified in CSA S304-14 for the design of masonry infills. [ABSTRACT FROM AUTHOR]

Landslides represent a large-deformation process influenced by various factors of uncertainty, such as types of ground motion (GM), randomness of GMs, and spatial variability of soils. The behavior of landslides is profoundly affected, making their assessment and measurement challenging. This paper proposes a computational approach for simulating the large-deformation process of landslides based on three-dimensional (3D) non-ordinary state-based peridynamics (NOSBPD). The analysis results of NOSBPD indicate that the mean runout distance triggered by pulse-like ground motions (PLGMs) is 16% greater than that induced by non-pulse ground motions (NPGMs), suggesting that PLGMs exhibit higher destructiveness. Besides, this paper establishes a runout distance assessment framework by considering the stochastic nature of PLGMs. This framework allows for the evaluation of the specific risk probability of landslides caused by stochastic PLGMs that match the target spectrum specified by codes. By introducing the theory of random fields and implementing a coupled procedure in peridynamics, we conducted a detailed analysis of the impact of spatial heterogeneity on the evolution process and consequences of landslides. Additionally, compared to two-dimensional (2D) analysis, the mean runout distance obtained from 3D analysis increased by 27.5%. This suggests that 2D analysis may underestimate the consequences of landslides. The findings of this study can serve as a scientific foundation for predicting the extent and scope of landslides triggered by near-fault earthquakes. • A computational approach for 3D landslide leveraging NOSBPD features is proposed. • A coupling procedure between random fields and PD is proposed. • A runout distance assessment framework is established to evaluate landslide risk. • Effects by various sources of uncertainty are explored. [ABSTRACT FROM AUTHOR]

The paper presents unique research on real-scale post-tensioned concrete crane girders dismantled from an existing hall structure. The study aimed to determine the transmission length for bonded prestressing tendons in an anchorage failure situation, a critical factor for proper assessment of the safety of many building structures, mainly those built between the 1950s and 1980s. The results of the tests indicated the feasibility of prestressing force transmission from a 12Ø5 mm Freyssinet-type tendon to the element via bond stress, with implications extendable to the other 18Ø5 mm tendon type prevalent at the time. The key factor affecting transmission efficiency is the quality of tendon duct grouting, with good quality cement injection resulting in transmission length as short as 800 mm. Furthermore, a computational model for the transmission length of prestressing force in post-tensioned concrete members has been developed similarly to the Model Code 2020 for pretensioned concrete. The level I of approximation enables quick transmission length estimation, whereas refined analysis is possible with the level II approach. The developed model and the research findings facilitate a comprehensive assessment of the post-tensioned concrete members in anchorage or tendon failure scenarios. As a result of the analyses carried out, optimal strategies for the further use of the structures can be proposed, fostering a step towards sustainable management. [Display omitted] • The paper details unique laboratory tests conducted on real-scale girders dismantled after 50 years of service. • Analysis of the strain changes of post-tensioned concrete girder during the simulation of tendon anchorage failure was performed. • The assessment of the transmission length for multiwire tendon in the anchorage failure scenario was carried out. • The feasibility of prestressing force transmission from bonded tendon to concrete in an emergency situation is shown • A computational model for transmission length and effective prestressing force evaluation was developed. • The developed model facilitates a comprehensive assessment of the post-tensioned concrete members. • Limitation of unnecessary shutdowns of useful industrial facilities is feasible. [ABSTRACT FROM AUTHOR]

A gap in current design approaches demands explicitly introducing a capacity design approach when designing steel-concrete composite reduced web section (RWS) connections. This paper addresses this gap by presenting test-validated finite element models and parametric investigations, focusing on the presence and absence of composite action over the web opening, the diameter, and the end-distance of the web opening. Additionally, the first-ever comprehensive experimental and numerical database from the literature on bare steel and composite RWS connections is compiled and thoroughly analysed to develop the capacity design assessment for such connections. Both parametric investigations and the database highlight the significance of the capacity design ratio between the connected components in achieving a desirable ductile mechanism. This is crucial, as evidenced by the results: a 15 % increase in the connection's moment capacity led to an average 21 % difference in dissipated energy, favouring the web opening with a diameter of 50 d o over 80 d o , in RWS connections with the presence of composite action. The results show that proper consideration of the capacity design approach in designing RWS connections ensures a stable yield mechanism is developed, resulting in the redistribution of global action and capping deformation demands on non-ductile elements. This enhances connections' rotational capacity and ductility by forming the Vierendeel mechanism. Lastly, the paper presents a detailing recommendation for employing RWS connections in both existing and new structures for seismic purposes. • Demountable steel-concrete composite extended end-plate RWS specimens examined under cyclic loading. • High-fidelity modelling and parametric finite element investigation. • A complete up-to-date database on steel and composite RWS connections. • Current design approaches demand an explicit introduction of the capacity design approach for prequalified RWS connections. • Vierendeel mechanism enhances the rotational capacity and the ductility of RWS connections. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for the underwater crack detection by fuse the optical and texture information. Underwater crack images were influenced by the harsh underwater environment, lead to making crack detection challenging, especially difficult to capturing the details of cracks accurately. To improve detection accuracy, it was necessary to obtain more feature information related to cracks. Therefore, this paper proposes a dual-input branch semantic segmentation model to achieve the fusion of optical and texture information, and introduces the Convolutional Block Attention Module (CBAM) module to enhance the performance of the semantic segmentation model. The optimal network architecture was determined by selecting the backbone network and optimizer, and a custom Tversky loss function was introduced to make the semantic segmentation model pay more attention to the crack area. The results show that the detection accuracy, IoU, and F1-Score can reach 96.07 %, 0.95, and 0.96 respectively. Through multiple comparative experiments, the effectiveness of the proposed method was validated, particularly compared to the non-fused texture information method, where the accuracy, IoU, and F1-Score were increased by 3.30 %, 6.74 %, and 7.88 % respectively. Finally, by visualizing the variation pattern of cracks in the detection model, the operational mechanism of the proposed method was explained. This confirms that the proposed method significantly improves the accuracy of underwater crack detection, and provides a novel approach for the underwater defect detection. • A new underwater crack detection method by fusing optical and texture information. • The crack feature extraction performance of the semantic segmentation model has been improved through the CBAM module. • Feature visualization and importance analysis reveal the variation patterns of cracks in the proposed model. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study aimed at characterizing the lateral cyclic behaviour of Glulam (GL), Laminated Veneer Lumber (LVL), and Glued Laminated Veneer Lumber (GLVL) shear walls anchored to the foundation by means of conventional hold downs and angle brackets, which are fastened to the timber walls with annular ring nails. Monotonic and cyclic tests are conducted on these mechanical anchors, with hold down connections tested under tensile loads and angle bracket connections under shear loads. Withdrawal tests on annular ring nails embedded in GL, LVL, and GLVL elements are also conducted, to investigate the withdrawal response of the fasteners. The experimental tests reveal that the lateral behaviour of GL, LVL, and GLVL shear walls is similar to that of Cross-Laminated Timber (CLT) shear walls, primarily governed by the wall base connections and by the wall geometry. Hold down and angle bracket connections exhibited a mechanical behaviour governed by the steel-to-timber joints, to large extent comparable with that of typical hold downs and angle brackets fastened to CLT elements. Generally, higher ductility and lower load carrying capacity were reached by hold downs and angle brackets fastened to GL elements compared to those reached by hold downs and angle brackets fastened to LVL and GLVL elements. All quantities relevant for the seismic design, such as stiffness, load carrying capacity, ductility, and overstrength factors are calculated and discussed through the paper. These quantities are then compared with results from different experimental investigations on hold downs and angle brackets fastened to CLT elements available in the literature. Finally, an analytical model for the calculation of the lateral load carrying capacity of the shear walls is presented and used to verify that the same calculation models used for CLT shear walls can be adopted for GL, LVL, and GLVL shear walls. • The lateral behaviour of Glulam, LVL and GLVL shear walls is investigated. • The cyclic behaviour of hold downs and angle brackets fastened to Glulam, LVL and GLVL elements is investigated. • Mechanical properties and overstrength factors of the wall base connections are presented. [ABSTRACT FROM AUTHOR]

Bridge girders are subjected to repeated patch loading during incremental launching (i.e. travelling over supports). Plastic deformations are likely to occur in the girder already at the first patch loading. They influence the girder's structural response and bring about a decrease in the ultimate resistance at subsequent patch loadings. This problem is analysed in the present paper through the serviceability limit state (SLS) of incrementally launched bridge I-girders (ILBGs). The SLS of ILBGs is a current problem since only a few studies, with contrasting conclusions and certain limitations, have been recognised in the literature. Research is limited on plate girders without longitudinal stiffeners made of structural steel. Flat slide-type launching shoes are considered in this paper. The serviceability requirement (repeatable behaviour of ILBGs) and criterion (that effective membrane strains should remain in the elastic range) are adopted from the literature. So, the serviceability resistance is adopted as a load at the start of the effective membrane plastic strains in the girder. In order to propose a practical and simple SLS design procedure, the serviceability resistance is normalised against the ultimate resistance, so a serviceability correction factor (k sls) is defined. The paper presents a parametric numerical analysis of the factor (k sls). A finite element model previously developed and validated by the author is employed to simulate a nonlinear response of patch-loaded girders. The parametric study includes 599 girders. k sls is inversely proportional to the web thickness and directly proportional to the flange thickness and the yield strength of the steel material. The load length, web depth and flange width do not influence k sls. The influence of the spacing between transverse stiffeners on k sls is negligible. Finally, by regression analysis of the results of parametric study, an original and reliable serviceability correction factor is proposed as the main objective of the research. The range when the SLS of ILBGs should be checked is also defined. [Display omitted] • The serviceability correction factor (k sls) is the serviceability resistance normalised against the ultimate resistance. • A parametric numerical analysis of k sls is conducted. The numerical database contains 599 patch-loaded girders. • The load length, web depth and flange width do not influence k sls , while the influence of the spacing between transverse stiffeners is negligible. • k sls is inversely proportional to the web thickness and directly proportional to the flange thickness and steel grade. • A reliable, original and simple empirical expression for k sls is proposed. [ABSTRACT FROM AUTHOR]

This paper proposes a new mechanical model to describe the dowel action with the aim of using the model to gain a deeper understanding of the unstable dowel splitting cracking observed in shear experiments of beams without shear reinforcement. The model was developed by combining beam on elastic foundation (BEF) theory and fracture mechanics. The proposed model is able to predict the whole evolution process of dowel action until the propagation of the dowel splitting crack becomes unstable. The model theoretically proves that the development of a dowel splitting crack can become unstable under certain conditions, therefore leading to the unstable shear failure of the whole member. In addition to the derivation of the analytical model, the paper also validates the model using data from the literature. Finally, an analytical solution of the critical shear displacement that triggers the unstable dowel splitting crack is derived. It can be used to improve the failure criterion initially proposed in the Critical Shear Displacement Theory (CSDT). • A mechanical model for dowel action is proposed based on beam on elastic foundation theory and fracture mechanics. • The unstable dowel splitting cracking is theoretically demonstrated in the proposed model. • A closed-form analytical solution is derived for critical displacement for unstable cracking. • The full load-displacement response of dowel action can be obtained using the proposed model. • The proposed model can predict the experimental data with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The shear strength of piers and spandrels is a crucial factor in masonry buildings, affecting structural safety. Such a strength can be increased in several ways, particularly by using fiber reinforced cementitious matrix (FRCM) reinforcements. These reinforcements can be applied symmetrically on both sides of the wall or only on one side. As it is well known, the FRCM-to-substrate adhesive properties strongly affect the effectiveness of such reinforcements. Moreover, a complete covering of the reinforced surface with bidirectional mesh evenly distributes the stresses, improving the load-bearing capacity. Appropriate test methods, for example diagonal tests, can be effectively used to evaluate the shear capacity of masonry panels, even with externally bonded composite material reinforcements, and the corresponding failure mechanism. This paper describes the results of an experimental campaign involving masonry panels, made with three different types of mortar, also reinforced with a PBO-FRCM system, subjected to diagonal tests. Through the experimental results, it was possible to determine the shear capacity of the panels, identify the failure mechanisms and evaluate the effectiveness of the FRCM reinforcements. The predictive capability of design formulas proposed in the literature for evaluating the shear capacity of unreinforced and reinforced masonry panels has been analyzed in the paper. • The results of an extensive experimental program on masonry panels subjected to diagonal tests are described in this research. • Three different types of masonry, differing for the type of mortar, and both unreinforced and reinforced panels are analyzed. • The experimental shear capacity of the panels is compared with the predictions of design formulas available in the literature. [ABSTRACT FROM AUTHOR]

This paper presents an experimental program on a series of long-span cold-rolled aluminium portal frames with various configurations subjected to different load combinations. The main structural members of the portal frame systems, including columns and rafters, were constructed using cold-rolled aluminium back-to-back built-up channel sections made from aluminium alloy 5052-H36 materials. The objectives of this paper are to understand the structural behaviour of different portal frame configurations and to explore possibilities for improving the performance of the structural systems, including strength and ductility enhancements. A total of four full-scale two-bay portal frame systems, each featuring two end frames and a central frame, were tested. The columns were braced against flexural-torsional buckling by girts spanning between the columns of the central frame and the columns of the two end frames. As a result, the portal frames failed due to in-plane sway deformations with the columns reaching their full section capacities. The tests revealed that the addition of rafter tie and sleeve stiffeners significantly improved the performance of the cold-rolled aluminium portal frame systems. Described in a separate publication, the authors also conducted a study to experimentally investigate the behaviour of the same system but with unrestrained columns, resulting in failure due to flexural-torsional buckling. Collectively, these two works form the foundation for further studies on cold-rolled aluminium portal frames in particular, and aluminium structures more generally. • Four full-scale portal frames of cold-rolled aluminium back-to-back built-up channel sections are tested. • Aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural members and frame components. • Portal frames are tested under two loading cases, including vertical loads only and combined horizontal and vertical loads. • Braced columns of the portal frames by girts spanning between the frames enhance the load capacity of the frame system. • Rafter tie and sleeve stiffeners added to the portal frames significantly improve the performance of the portal frame systems. [ABSTRACT FROM AUTHOR]

The research object of this paper is to investigate the mechanical behavior and develop an analytical model of the prestressed circular-section rocking steel piers with external energy-dissipating devices under the horizontal cyclic load. Based on the method of monolithic beam analogy under monotonic loading, the concept of generalized rotation angle and intercept strain in the pre-decompression state was introduced. The geometrical equations for the pre- and post-decompression stages are deduced. The calculation formulas for internal forces of each component and the analytical calculation method for the entire process of the rocking steel pier under horizontal cyclic loading are established in detail. To reproduce the hysteresis curve of the test, some special test conditions, such as the retraction effect of prestressed tendons and increase of the compressed area due to the vertical plates, were considered in the analytical model. The results show that the analytical method based on generalized rotation angle and intercept strain can ensure an ideal transition of the hysteresis curve of the pier in pre- and post-decompression stages. Except for the pier with particularly severe local buckling and ovalization deformation, the calculated results obtained from the proposed analytical model agrees well with the test results for the rocking steel bridge piers. The effect of prestressed tendons and the P –Δ effect on the lateral load–displacement curve of rocking steel bridge biers was further analyzed through parametric study using the proposed model. The analytical calculation method presented in this paper provides a theoretical tool for seismic design of the rocking steel pier in engineering practice. This paper provides important guidance for the establishment of seismic design method of rocking steel piers. • to deduce the geometrical equations for the pre- and post-decompression stages of the rocking steel pier. • to establish the analytical calculation method for the entire process under horizontal cyclic loading. • to analyze the effect of prestressed tendons and the P –Δ effect on the lateral load–displacement curve. [ABSTRACT FROM AUTHOR]

Civil infrastructure relies heavily on structural health monitoring systems. However, these systems often encounter challenges due to sensor failures and environmental damage. Consequently, numerous anomalous data points are generated, significantly distorting the accuracy of structural safety assessments. While deep neural networks have emerged as a promising tool for efficiently identifying abnormal data, the meticulous optimization of hyperparameters during training remains a challenge. To address this challenge, this paper introduces a novel approach termed multiple transfer learning, designed to continually enhance a model's classification performance without the need for meticulous hyperparameter configurations. This methodology achieves adaptive training by iteratively migrating across bridge anomaly datasets, bypassing the need for elaborate hyperparameter setting. In this study, five distinct hyperparameter working conditions are established and evaluated to validate the effectiveness of the multiple transfer learning method. The findings highlight the robustness of this approach, demonstrating that multiple transfer learning achieves satisfactory recognition accuracy levels irrespective of the initial hyperparameter setting during network model training. This method circumvents the need for continuous hyperparameters optimization, enabling the adaptive detection of abnormal bridge data. • A training method called multiple transfer learning based on transfer learning is proposed in this paper to solve setting hyperparameters. • The relationship between the number of multiple transfer learning times and the accuracy of anomaly data identification is displayed. • Comparison experiments with different working conditions were set up to verify the effectiveness of multiple transfer learning. [ABSTRACT FROM AUTHOR]

This paper proposed a new method to strengthen and repair concrete columns, which combined active and passive confinement. The method involved the use of iron-based shape memory alloy (Fe-SMA) strips to quickly exert active confinement to these columns, followed by the use of fiber-reinforced polymer (FRP) and high-density polyethylene (HDPE) tubes as external passive confinement to improve the load-bearing capacity, durability, and ductility of concrete columns. Rubber concrete that performs high energy consumption and certain strength was used as the cladding layer to improve the impact resistance of the concrete column. This paper explored the effect of this method on the bearing capacity performance of concrete columns through axial compression tests and set three test variables, including different net-spacing of Fe-SMA, different FRP wrapping forms, and different FRP layers. The test outcomes showed that all three test variables obviously improved the load-bearing capacity and ductility of concrete columns, peculiarly when applying active confinement. Eventually, this paper proposed a theoretical model to predict the peak compressive strength of the specimen, which can provide a reference for designing this active-passive confinement strengthening method. • A new technique for strengthening concrete columns by using a combination of active and passive confinement was proposed. • The effect of different experimental variables on axial compressive behaviour of concrete columns were tested. • The variation laws of the axial compression performance of specimens were researched. • A theoretical model was given to predict the peak compressive strength of the specimen. [ABSTRACT FROM AUTHOR]

A comprehensive investigation into the mechanical properties of 50 and 70 mm thick high strength S690 steel plates and their butt-welded sections under tension was presented in this paper, and a total of 40 tensile tests were conducted. Firstly, a total of 18 proportional coupons with circular cross-sections were extracted at three different layers within the plate thicknesses. Tensile tests on all of these coupons were carried out to obtain their mechanical properties, and their variations across the plate thicknesses were also examined. Secondly, submerged arc welding was adopted to prepare butt-welded sections between these thick steel plates with various heat input energy. Micrographic examinations on typical heat-affected zones of the welded sections were also performed. Standard tensile tests on a total of 22 proportional coupons with rectangular cross-sections were carried out to obtain their mechanical properties, and the full range deformation characteristics of these coupons were assessed and compared, in particular, their tensile strengths and elongations at fracture. This paper presents important experimental evidence on the mechanical properties of these high strength steel plates of practical thicknesses in construction, and also of their butt-welded sections. It is demonstrated that there is little or even no reduction in their mechanical properties of these butt-welded sections, provided that the welding processes are properly controlled according to established welding practice. Hence, full strength butt-welded sections between these thick high strength S690 steel are readily achieved in practice, similar to those of the commonly adopted S355 steel. These important findings are contrary to general understanding as many researchers and engineers consider that the mechanical properties of these high strength S690 steel are reduced significantly after welding, irrespective of their plate thicknesses. [Display omitted] • Mechanical properties of thick high strength S690 QT steel plates were investigated. • There are significant variations in yield and tensile strengths across 70 mm thick plates. • Microstructures of heat-affected zones under various heat input energy were obtained. • No or little reductions in mechanical properties are found in these thick welded sections. • A proper control on welding procedures avoids reductions in their mechanical properties. [ABSTRACT FROM AUTHOR]

The modal-domain structural model updating and damage detection methods own the advantage that they perform the whole computation without the information of system input, when compared to the time-domain. The system input required in the time-domain methods is hardly measured in realistic field tests of civil engineering structures. However, the time-domain methods own the advantage that they carry out model updating based on raw measured dynamic responses but not the processed (and compressed) modal parameters. The modal-domain methods only uses the compressed modal parameters, and some useful system information may be lost in the compressing process. Thus, higher errors and uncertainties are induced in the model updating results from the modal-domain methods. To take advantages and avoid disadvantages from the traditional time-domain and modal-domain model updating methods, a novel time-domain MCMC-based Bayesian model updating method without the information of the system input is developed in this paper by incorporating a newly developed dynamic response reconstruction technique and extending the formulation of the posterior probability density function (PDF) and the corresponding bridge PDF in the MCMC sampling process. A new modal decomposition algorithm is proposed in this paper for accurate modal response decomposition even in case of dense or sparse modes, and filters are not required for higher computation accuracy. Experimental case studies on a two-story steel frame were conducted to illustrate the proposed methodology in both structural model updating and damage detection. According to the analysis results, it is concluded that the proposed methodology outperforms the modal-domain methods especially in the cases with small number of measured DOFs. • No excitation information is needed with the proposed time-domain MCMC-based Bayesian model updating method. • A novel modal decomposition method is proposed to obtain the modal responses without filters. • The uncertainties introduced by some uncontrolled factors are quantified with the proposed technique. [ABSTRACT FROM AUTHOR]

Italian and European transportation networks include a significant number of existing bridges, built since the early '60s, characterised by simply supported prestressed concrete (PC) girders with post-tensioned steel tendons. Corrosion of tendons, which may lead to significant loss of structural capacity, cannot be detected by simple visual inspections and requires advanced and expensive testing by bridge owners. Therefore, procedures aimed at risk-informed prioritisation of advanced inspections and possibly retrofit are needed. The paper presents a study on the fragility of existing PC girder bridges considering traffic loads, accounting for corrosion-induced effects. An automated framework is proposed, aiming at the efficient probabilistic structural assessment of the investigated bridge typology accounting for different critical corrosion scenarios and the influence of knowledge-based uncertainty related to geometric and mechanical properties. To simulate corrosion effects, prestressing steel tendon geometric and mechanical characteristics are modified through a specific algorithm able to estimate variations in flexural and shear bearing capacity of critical cross-sections. To simulate the traffic loads, a simplified analysis is performed by using code-based traffic load models. In the paper, the framework is tested with reference to a dataset of case-study superstructures. The obtained fragility curves are deeply discussed, highlighting the effects of the number of girders and span length on the corrosion-induced increase in fragility. Although the proposed methodology presents some simplifications, it could improve the current practices of risk prioritisation, by supporting transportation authorities in ensuring the safety of the existing bridge stock. • A methodology for fragility analysis of PC girder bridges under traffic loads is proposed. • The methodology accounts for knowledge-based uncertainty and corrosion of tendons. • The strategy for flexural response analysis of cross-section considering corrosion is validated. • The methodology is applied for six case-study superstructures. [ABSTRACT FROM AUTHOR]

Fiber-reinforced concrete is a typical unidirectional fiber-reinforced composite. For practicality and efficiency, fiber-reinforced concrete usually has the fiber and matrix modeled separately and then the fiber is embedded into the matrix. Therefore, this paper proposes a novel method to realize the topology and fiber orientation optimization for fiber-reinforced concrete structures. The optimization formulation considers two types of discrete variables, i.e., topology and fiber orientation, which are optimized by using the solid isotropic material with penalization method and bi-value coding parameterization method, respectively. To reduce the computational complexity, the topology and fiber orientation are independently updated at each iteration during the optimization process. Numerical examples verify the validity of the proposed method, which provides new ideas for the design of fiber-reinforced concrete structures. • This paper proposes a topology optimization method for fiber-reinforced concrete structures using membrane-embedded model. [ABSTRACT FROM AUTHOR]

Friction is an important source of energy dissipation in structural damping. The effect of friction on the damping ratio, however, has not been fully investigated. This paper presents an experimental study of the nonlinear damping ratio induced by friction at bolted joints of a bridge model in the laboratory. The decay responses of the bridge were tested under various bolt configurations and pre-torques. The nonlinear characteristics of the damping ratio were analyzed, and the experimental results were interpreted through numerical simulations. The relationship between damping ratio and amplitude of the Iwan model was derived. The results show that friction induces a nonlinear damping ratio. The damping ratio exhibits two opposite nonlinear characteristics under the influence of bolt joints. The damping ratio may either decrease with decreasing amplitude or may increase, and both of these nonlinear patterns can be elucidated by the Iwan model. Numerical simulations successfully replicate these two nonlinear damping ratios. A case study of an actual steel truss bridge is used to discuss the possible effects of bolt joints on the damping ratio. The results of this paper reveal the nonlinear damping patterns induced by bolt joints and provide an optional model for such structures. • There are two opposite nonlinear patterns of bridge damping ratio under the influence of bolt joints. • The configuration and pre-torque of bolts induce the damping ratio to vary in the range of approximately 0.25% to 1.20%. • High pre-torque may result in lower damping ratio. • The Iwan model can explain the two nonlinear patterns of the damping ratio. [ABSTRACT FROM AUTHOR]

The realistic consideration of reusability of a fire effected RC structure or structural member relies on the accurate estimation of post-fire structural capacity. Bond between steel and concrete play a vital part in the structural analysis of RC. This paper presents a study on bond behaviour of RC structural members exposed to fire employing ISO-834 fire scenario and using beam-end test specimens to take into account the realistic boundary conditions of a flexural member. The study is a continuation of the previous work done by authors. The focus of this paper is to understand the residual bond behaviour considering various concrete covers and the presence of transverse reinforcement for various fire durations. Two different fire exposure scenarios are considered, namely one-sided heating, where only the surface with the minimum concrete cover is exposed to fire and three-sided heating, where two side surfaces along with the surface with minimum cover are exposed to fire. The beam-end specimens were exposed to fire for a desired fire exposure duration, followed by a natural cooling to room temperature. An unconfined pull-out test was performed thereafter to obtain residual behaviour. The results show that although concrete cover and presence of transverse reinforcement do have an influence on the absolute values of the residual bond splitting strength after fire, the relative values of bond degradation due to fire are not very strongly influenced by these parameters. • Post-fire bond behavior of reinforcement in concrete is experimentally investigated considering real fire scenarios. • Different concrete cover and transverse reinforcement in the bonded zone are considered. • Modified beam-end specimen is used in the experimental investigations. • Specimens are subjected to ISO834 fire scenarios for different fire exposure durations with one- or three- sided exposure. • Severe reduction in post-fire bond capacity and stiffness is observed for all the investigated cases. [ABSTRACT FROM AUTHOR]

Nonlinear energy sink (NES) is a type of vibration absorbers that does not have linear stiffness. Through establishing strongly nonlinear coupling between a primary system and a NES, the targeted energy transfer can be achieved from the primary system to the NES, thereby realizing vibration absorption in a wide frequency range. A significant amount of research work has been conducted on developing the NES for unidirectional vibration energy transfer over the last decade. More research is expected to develop further NESs to address various engineering vibration problems. Meanwhile, the question of whether NES can be practically applied to engineering is always being asked. The main objective of this paper is to review the research progress on dynamic design of NESs to promote the application of NESs to reduce engineering structure vibration. To do so, this paper first summarizes the characteristics of NESs, including vibration absorption mechanism, the threshold of targeted energy transfer, and strong nonlinearity characteristics. Then, dynamic designs of the NESs proposed in the literation are reviewed in terms of nonlinear stiffness design, mass design and damping design. Special attention is placed on the nonlinear stiffness design for NESs, including design principle, multi-stability design, track design, and magnetic design. The gaps between these design approaches and applications are explained. NES cells and their distributed vibration control strategy are also introduced. The research progress on the NES optimization design is also briefly discussed. Following the extensive review on NES dynamic design research, future promising research topics are recommended with an attempt to advancing the engineering application of NES. It is expected that this paper would help readers to understand the progress of NES dynamic design research and the future NES development for more practical applications. • The research progress on dynamic design of the nonlinear energy sink is reviewed. • The NES cell and its distributed vibration control strategy are also introduced. • Future promising topics are recommended to advance the application of NES. [ABSTRACT FROM AUTHOR]

Rocking of a non-symmetric block on a compliant horizontally-moving base is explored for the first time in this paper through a combination of analytical, numerical and experimental approaches. A compliant base model is proposed, which is shown to have good overall accuracy, in particular predicting when rocking will be initiated. The proposed model predicts a significantly lower rocking threshold, which is much more sensitive to the eccentricity of the centre of mass, in comparison with the threshold determined assuming the base is rigid. The proposed model predicts that a highly non-symmetrical block, with its centre of mass outside the middle third of its base, will have uplifted even when it is at rest and no horizontal excitation is applied. The proposed model also predicts lower overturning thresholds, which is because the static overturning angles reduce when the compliance of the base is accounted for. The proposed compliant base model provides an accurate tool suitable for the design of base isolation systems for the seismic protection of freestanding museum artefacts or mechanical equipment, as evidenced by the extensive numerical and experimental test results presented in this paper. • Dynamic response of non-symmetric rigid blocks standing on a horizontally-moving compliant base. • Combination of analytical, numerical and experimental studies. • The compliant base model can better predict when rocking will be initiated. • The rocking thresholds are significantly lower than those determined assuming the base as rigid. • The rocking thresholds are sensitive to the eccentricity of the centre of mass. [ABSTRACT FROM AUTHOR]

Timber is extensively utilized as a foundational component in the construction of bridge supports, known as timber piles. These structures are vulnerable to deterioration due to environmental influences, presenting potential risks to public safety. The application of fiber-reinforced polymer (FRP) has emerged as a prevalent approach for the rehabilitation of timber piles, favored for its installation efficiency. This paper introduces a novel contribution through the adoption of Acoustic Emission (AE) as an innovative, non-destructive method for evaluating the integrity of timber piles with and without FRP rehabilitation. In this paper, seven timber piles with varying degrees of damage have been prepared. Four of these piles were rehabilitated using fiber reinforced polymer (FRP) jackets and damaged regions were filled with either resin or grout. Two different FRP jackets were investigated, a glass FRP (GFRP) bi-directional laminate and a unidirectional prepreg filled with sun-curing resin. Compression tests were conducted on each specimen and acoustic emission sensors were installed on the piles to assess the effectiveness of the repair and to evaluate the extent of damage as the load increased. Results of compression tests show that the most effective method was the use of the GFRP laminate filled with grout for piles with large areas of natural damage and the GFRP laminate filled with resin for piles with smaller areas of damage. The AE results demonstrated that AE is a useful non-destructive technique, and the analysis of cumulative signal strength (CSS), intensity and cumulative hits can be applied to unrehabilitated and rehabilitated timber piles to gauge damage in members. • Carried out a detailed study involving the use of FRP for rehabilitating damaged timber piles. • Employed two different types of FRP jackets for rehabilitation and assessed their effectiveness. • Utilized Acoustic Emission (AE) to gauge the extent of damage and rehabilitation efficacy. • Assessed and compared various rehabilitation methods based on strength, cost, and practicality. [ABSTRACT FROM AUTHOR]

Although mainland Portugal has been spared from large magnitude earthquakes in recent years, it faces a threat due to the presence of several active fault systems. In such a framework, Portuguese pre-code masonry construction is believed to be the most vulnerable in the existing building stock. Given the lack of information on earthquake damage to this stock, the use of detailed numerical models is a viable strategy to comprehend its seismic behavior. This paper provides an updated fragility characterization of Lisbon pre-code masonry buildings based on their seismic assessment through the Applied Element Method. To limit the computational time, a promising pushover strategy, known as Incremental Ground Acceleration, was adopted. After the characterization of the current fragility, two retrofit layouts based on piers strengthening were modeled and assessed for the building stock whose seismic capacity does not meet expected demand. The aim of the paper is to derive updated fragility curves for the Lisbon region to support risk analysis incorporating the latest hazard studies and to offer insights into potential retrofit interventions. • Incremental Ground Accelerations to estimate the seismic capacity of representative pre-code buildings in Lisbon (Portugal). • Analytical-numerical seismic fragility curves for the Lisbon region incorporating the recent hazard studies. • Integration of fragility curves with the retrofit to support risk studies. [ABSTRACT FROM AUTHOR]

The longitudinal displacement at the girder ends of long-span suspension bridges is a crucial issue that affects structural safety, durability, as well as traffic safety and ride comfort. The primary cause of these reciprocating displacements is the action of moving live loads, which induces quasi-static displacements in the longitudinal direction. This paper theoretically investigates the static longitudinal displacements of suspension bridges under a moving vertical concentrated load and elucidates the underlying deformation mechanisms. Considering geometrical nonlinearity, analytical equations are established for the longitudinal deformations of the main cable and stiffening girder under a vertical concentrated load. By analyzing the geometrical deformation conditions of the suspenders, the relationship between the longitudinal displacements of the stiffening girder and the main cable is derived. Due to the coupling between longitudinal and vertical displacements, the vertical displacement of the stiffening girder must be solved to obtain its longitudinal displacement. Based on deflection theory and considering the bending stiffness of the stiffening girder, this paper derives the vertical deformations of the stiffening girder for single-span suspension bridges and those with short continuous side spans under a vertical concentrated load, which is then used to calculate the longitudinal displacement. Finite element models are used to verify the accuracy of the analytical solutions. Differences between the proposed solutions and previous solutions neglecting the bending stiffness of the stiffening girder are compared and analyzed. The effects of neglecting the longitudinal displacement at the bridge tower top and the presence of short continuous side spans on the longitudinal displacement of stiffening girder are also investigated. The results demonstrate the high accuracy of the proposed analytical solution for the longitudinal displacement at the girder ends of suspension bridges. Importantly, the bending stiffness of the stiffening girder cannot be neglected in calculating the longitudinal displacement. The longitudinal displacement at the girder ends is primarily caused by the longitudinal deformation of the main cable, while the contribution from the flexural deformation of the girder is negligible. Furthermore, the longitudinal displacement at the bridge tower top has a negligible effect on the longitudinal displacement of the girder, and the presence of short continuous side spans is beneficial for reducing the longitudinal displacement of the stiffening girder. The proposed analytical solution method provides a rapid approach for calculating the static longitudinal displacement at the girder ends of suspension bridges under passing live loads and reveals the deformation mechanism. This is beneficial for preliminary design and structural optimization, as it avoids the complex finite element modeling and solution process. • Deriving and validating analytical solutions for longitudinal displacements. • This deduction considers the stiffness of the stiffening girder. • Both single span and those with short continuous side spans are considered. • Analyzing effects of bridge tower, side spans and girder stiffness. • Offering quick and accurate analytical solutions for girder end displacement. [ABSTRACT FROM AUTHOR]

Previous studies have put forward reduction factor equations to determine the web crippling strength of cold-formed steel (CFS) channels with circular web openings. However, these equations overlook vital parameters such as material yield strength, flange width, and fillet radius of CFS channels. Consequently, this paper introduces simplified Direct Strength Method (DSM) equations, which account for plastic loads (P y) and elastic buckling loads (P cr), integrating the aforementioned crucial parameters. Eight unique yield line models were devised, considering two-flange loadings: interior-two-flange (ITF) and end-two-flange (ETF), as well as the positioning of circular web openings, to compute the yield line length for P y. Similarly, new P cr equations were also proposed. The reliability of the proposed equations was evaluated using a dataset of 236 test results sourced from the literature. This assessment aims to demonstrate the suitability of the equations for incorporation into future revisions of international design codes. • This paper introduces simplified Direct Strength Method (DSM) equations for determining the web crippling strength of CFS channels with circular web openings under two-flange loadings. • Eight novel yield line models, accounting for various load cases and positions of circular web openings, were developed to compute the yield line lengths. • New critical loads (P cr) equations, considering the effect of circular web openings, were obtained through regression analysis. [ABSTRACT FROM AUTHOR]

A robust and efficient plastic analysis method incorporated into beam-column elements is highly demanded for economic design and safety evaluation of structures under earthquakes and extreme events. This paper presents a novel approach for the direct analysis of steel structures allowing for material yielding by introducing an enhanced plastic hinge method to an advanced second-order beam-column element, which is derived based on a rigorous incremental-iterative force recovery procedure. The new element considers various critical factors at the element level, including transverse shear deformation, initial geometrical imperfections, and residual stresses. Thus, the approach enables the analysis and design of a wide range of steel structures using a single element per member, which contrasts with commercial software that requires many elements per member. Several benchmark problems are investigated and the results are in good agreement with those in literature and commercial software. The paper offers a reliable, efficient, and practical solution for direct analysis of steel structures in various engineering applications without the use of the conventional effective length method. • A 3D second-order beam-column element for direct analysis is derived based on a rigorous force recovery procedure. • An end-spring type refined plastic hinge approach is integrated into the proposed second-order beam-column element. • Accurate section stiffness models are introduced for both major and minor principal axes of wide-flange sections. • The consideration of transverse shear deformation, geometric imperfections, and residual stresses in members is included. [ABSTRACT FROM AUTHOR]

In this paper, we present a new seismic metamaterial (SM) for the suppression of Lamb waves and surface waves utilizing the negative Poisson's ratio (NPR) foam. The periodic cell of the metamaterial is composed of a square cylinder made of steel in the center and NPR foam connecters at the corners. Utilizing the unique resonance properties of the NPR material, an ultra-low-frequency broadband wave suppression is achieved. First, the characteristics of bandgaps (BGs) of the proposed structure with different materials were analyzed using the finite element (FE) method. It shows that the application of the NPR foam can significantly broaden the BGs compared with the case using traditional rubber. The vibration modes were analyzed to investigate the mechanism of BG generation, and the results show that the broad BG is achieved via the unique local resonance mechanism of the NPR foam. Subsequently, the frequency-domain analysis was carried out to verify the shielding effect of the designed SM on Lamb waves, using a periodic structure consisting of 10 × 6 unit cells. It shows that the designed SM can effectively attenuate Lamb waves in the range of 3–44 Hz with attenuation up to −590 dB at 32 Hz. A parametric analysis shows that the NPR foam with small thickness, high modulus, low mass density, and low Poisson's ratio can broaden the first complete BG. In addition, the acoustic cone method was combined with the frequency-domain analysis to calculate the BGs of the proposed structure against the surface wave, using a periodic structure consisting of 20 unit cells. It shows that the surface wave can be significantly attenuated within the BG. Finally, real seismic excitations were applied for time-domain analyses, and the simulation results show that the proposed structure can effectively shield the low-frequency seismic surface waves in the range of 0.1–20 Hz. The design scheme proposed in this paper is simple in structure and easy to implement, and is believed to possess bright application potentials in seismic protection. • A new seismic metamaterial (SM) utilizing the negative Poisson's ratio (NPR) foam is presented. • The proposed SM can effectively attenuate Lamb waves in the range of 3-44 Hz with attenuation up to −590 dB at 32 Hz. • The proposed SM can effectively shield the seismic waves in the range of 0.1-20 Hz, with its amplitude attenuated by more than 85 %. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) provides real-time data on the condition and performance of infrastructure, enabling timely and cost-effective maintenance interventions, and hence enhanced safety and extended service life. The computer vision-based non-contact sensor has emerged as a promising alternative to conventional contact-type sensors for structural displacement measurement and SHM. Many of the currently reported vision-based structural displacement measurement systems typically temporarily set up a video camera from a distance to the structure. The collected images or videos are usually stored locally and post-processed offline to obtain structural displacement responses, which is cumbersome and limited to short-term SHM applications. The recent development of technologies empowered by the Internet of Things (IoT) and edge computing has enabled real-time video processing and analysis at the source, minimizing latency, reducing bandwidth requirements, and enabling prompt decision-making, thereby enhancing efficiency and responsiveness compared to traditional offline video recording and processing systems. In this paper, an edge computing vision-based displacement measurement system (EdgeCVDMS) is developed. Video recording, processing, and displacement response identification are entirely performed on an edge device integrated with the vision-based displacement tracking algorithm, thereby greatly reducing the amount of data transmitted to the cloud server. The feasibility and applicability of the developed sensing system are experimentally validated on a laboratory-scaled transmission tower structure. The proposed EdgeCVDMS is cost-effective, easily deployable, and of great potential to be applied for the condition assessment of a larger population of aging civil infrastructure. • This paper proposes a displacement measurement method based on edge computing. • Vision-based algorithm and edge computing device are used for measuring displacement. • AWS is used for data management and visualization. • Experimental validations are conducted to verify the accuracy of the proposed device. • Different influence factors, such as lighting conditions, angle and distance are considered. [ABSTRACT FROM AUTHOR]

Concrete is essential in global construction but significantly contributes to carbon emissions, primarily due to cement production. The cement industry is adopting low-carbon practices, such as using supplementary cementitious materials (SCMs) to reduce emissions. Concrete prepared with calcined clay can achieve a carbon reduction effect of approximately 30 % compared to ordinary cement. Current studies highlight the reuse of kaolin clay, the predominant constituent of engineering sediment in Shenzhen, China, providing raw materials for sustainable low-carbon and eco-friendly concrete. However, high substitution rates of calcined clay can compromise concrete strength, posing a challenge for the application in load-bearing structures. This study proposed a novel low-carbon eco-friendly concrete (i.e., using calcined clay as supplementary cementitious materials) filled into FRP tubes (i.e., Low-Carbon Eco-Concrete-Filled FRP Tubes, termed LCE-CFFTs) aiming to enhance substitution rates of calcined clay and to improve compressive strength and ductility. This paper provides a detailed description of the preparation method, chemical reaction process, chemical composition, and microstructure of calcined clay. Experimental tests investigated the axial compressive performance of LCE-CFFTs, considering calcined clay substitution rates and FRP thickness as key parameters. The experimental work and theoretical analysis indicated that: the inclusion of 10 % and 40 % calcined clay led to a reduction in carbon emissions, resulting in a decrement of 5.8 % and 23.3 %, respectively; confinement provided by FRP tubes mitigated the reduction in axial compressive strength resulting from calcined clay inclusion, particularly evident at higher substitution rates (40 %); the effect of FRP tube confinement in improving peak stress and axial performance of LCE-CFFTs became more pronounced with higher calcined clay substitution rates; to more accurately predict the axial compressive behavior of LCE-CFFTs of this study, it is essential to consider the biaxial stress-strain state of filament-wound FRP tubes. • This paper studied novel low-carbon eco-concrete filled into FRP tubes (i.e., LCE-CFFTs) under axial compression. • Axial compression tests indicated that calcined clay substitution rates had minimal impact on failure modes of LCE-CFFTs. • FRP tube confinement mitigated the reduction in axial compressive strength resulting from calcined clay inclusion. • The effectiveness of FRP confinement for LCE-CFFTs became more pronounced with higher rates of calcined clay substitution. [ABSTRACT FROM AUTHOR]

In this paper, strength reduction factors (R-factors) for performance-based seismic design of bridges in far-fault seismic regions are developed. Response spectrum analyses (RSA) and nonlinear time history analyses (NTHA) of simplified bridge models with piers of circular and rectangular sections having several substructure-superstructure connections are performed for wide ranges of design parameters and pier displacement ductilities based on target performance levels are obtained. Subsequently, a set of equations representing R-factors is proposed by performing linear regression analyses on the data obtained from the analyses. The accuracy of the proposed equations is investigated by performing error performance analyses, which indicated R-factors with mean error values close to zero. Furthermore, a simple application procedure of the proposed R-factor equations is presented and explained in detail through various sample bridges designed to achieve the performance objectives recommended by AASHTO LRFD, Eurocode, and the Canadian Highway Bridge Design Code (CSA). Eventually, a comparison between the estimated R-factors and those suggested by design codes is presented. The results showed that AASHTO LRFD recommends conservative R values for single-column bents, while it provides overestimated R values for multiple-column bents. Indeed, it is found that Eurocode recommends conservative R values for piers of limited-ductile behavior and relatively high R values for piers of ductile behavior. Therefore, it is concluded that the R-factors suggested by design codes might result in performance levels not intended in design. • Strength reduction factors (R-factors) for performance-based seismic design of RC bridges is presented. • The paper presents Six R-factor equations expressed in terms of various design parameters. • A novel performance-based seismic design procedure for RC bridges is introduced. • The paper provides an assessment of the R-factors existing in design codes by comparing them with the estimated ones. • The research provide valuable information to the bridge engineering community for improving the seismic design codes. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic characteristics (natural frequencies and damping ratios) of a 600-m-tall supertall building with an active tuned mass damper (ATMD) system during Super Typhoon Saola. Based on the wind speed, wind direction, and wind-induced acceleration response records by the structural health monitoring (SHM) system installed on the skyscraper, the wind characteristics during the passage of Saola are first investigated, and the relations between the mean wind speeds atop the skyscraper and the root-mean-square (RMS) acceleration responses are established. Then, employing the stochastic subspace identification (SSI) method and an uncertainty quantification method, this paper comprehensively investigates the uncertainty bounds, time-varying features, and amplitude-dependency characteristics of the modal parameters with and without the operation of the ATMD system. Next, on the basis of the identified modal parameters and time-frequency analysis, the performance and effectiveness of the ATMD system in suppressing the wind-induced vibrations of the skyscraper is investigated. Lastly, the structural health condition is evaluated from the perspective of building natural frequency and damping ratio changes before and after the typhoon hit. The goal of this study is to advance the understanding of the wind effects on supertall buildings and provide useful information for the wind-resistant design and vibration control of supertall buildings in tropical cyclone-prone regions. • Conduct field measurements on a 600-m-high skyscraper with an active tuned mass damper system during Super Typhoon Saola. • Investigate uncertainty bounds, time-varying features, and amplitude-dependency of modal parameters of the skyscraper. • Assess performance and effectiveness of the ATMD in suppressing wind-induced vibrations of the skyscraper. • Evaluate structural health condition based on building frequency and damping ratio changes before and after typhoon hit. [ABSTRACT FROM AUTHOR]