Structures最新文献

{"title":"Mechanical properties of wire arc additively manufactured steels at polar temperatures","authors":"Cheng Huang ,&nbsp;Nicolas Hadjipantelis ,&nbsp;Sangchu Quan ,&nbsp;Tao Chen ,&nbsp;Leroy Gardner","doi":"10.1016/j.istruc.2024.107627","DOIUrl":"10.1016/j.istruc.2024.107627","url":null,"abstract":"<div><div>Wire arc additive manufacturing (WAAM) offers the potential for automated construction in remote locations such as in polar regions, where the climate is cold and harsh and labour is scarce. To facilitate such applications, an experimental study into the mechanical properties of WAAM steel plates at polar temperatures has been conducted. Following microstructural and geometric characterisation, 48 as-built and machined WAAM tensile coupons made of normal and high strength steel wires were tested in the temperature range of −100 ℃ to 20 ℃. The low temperature environment was achieved by means of a liquid nitrogen cooling chamber, while the deformations of the coupons were monitored using digital image correlation (DIC). The stress-strain curves and key mechanical properties of the WAAM material are presented and discussed. It is shown that the Young’s modulus, strength and ductility of the WAAM steels increased with decreasing temperature to varying degrees, with the clearest ascending trend observed for the ultimate strength. Fractography was carried out on the tested coupons, revealing principally ductile fracture at low temperatures, though coupled with somewhat brittle features. Finally, predictive equations that can accurately capture the low temperature mechanical properties of the WAAM steels are proposed.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107627"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multitask SHM algorithm to identify damage with random severity and location in IPE beams using EMI technique","authors":"Mehrab Zamanian ,&nbsp;Naserodin Sepehry ,&nbsp;Seyed Mehdi Zahrai","doi":"10.1016/j.istruc.2024.107659","DOIUrl":"10.1016/j.istruc.2024.107659","url":null,"abstract":"<div><div>Existing electromechanical impedance (EMI) damage identification algorithms often face challenges in terms of generalizability. This paper presents a robust algorithm that can simultaneously estimate the region and severity of damage with random damage scenarios across a surface and any severity, rather than being limited to specific points and severities. The host structure was an I-beam. Simulated damage was introduced as a subtle added mass to evaluate the algorithm's effectiveness in early-stage damage identification. Initially, various EMI tests with different damage specifications were conducted, and validated through numerical simulation. Damage-sensitive features were extracted and were input into three ML models: support vector machine, random forest, and multilayer perceptron. An ensemble learning approach was employed to combine the individual predictions from these models. The algorithm achieved classification accuracies of 97.3 % and 94.4 % on the validation and test sets, respectively, for identifying damaged regions. The algorithm also quantifies damage severity, achieving R-squared values of 92 % and 88 % on the validation and test sets, respectively.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107659"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of NaHCO3 accelerated carbonation method on the early mechanical properties of recycled aggregate concrete","authors":"Ruitian Xu ,&nbsp;Ying Liang ,&nbsp;Fan Ning ,&nbsp;Zongping Chen","doi":"10.1016/j.istruc.2024.107647","DOIUrl":"10.1016/j.istruc.2024.107647","url":null,"abstract":"<div><div>In order to simplify the carbon sequestration process of recycled aggregate concrete (RAC), this paper proposes a method of using sodium bicarbonate (NaHCO₃) solution to cure RAC and accelerate carbonation. The compressive and flexural tests of 135 specimens were completed, and the effects of three carbonation environments and carbonation age on the early mechanical properties of RAC were studied. The results indicate that the carbonation environment of NaHCO₃ solution can significantly improve the early compressive strength and flexural strength of RAC, but it will reduce ductility. Before 21d, the early compressive strength and strength development of RAC after carbonation of NaHCO₃ solution were slightly lower than those in the carbonation environment of the carbonation box, but significantly improved at 28d. The carbonation age has little effect on the flexural strength of RAC, but at the same age, the flexural strength of RAC was highest after carbonation in NaHCO₃ solution. Through thermogravimetric analysis, it was found that the calcium carbonate content in RAC after carbonation of NaHCO₃ solution was 10.3 % higher than that after carbonation in the carbonation box, and 16.5 % higher than that of natural carbonation, offering an alternative pathway for carbon sequestration in RAC.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107647"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and numerical investigations on wave propagation in planar frames and trusses with shear deformable elements: Introduction of a fast numerical method using degrees of freedom just at joints","authors":"Amin Borji,&nbsp;Bijan Boroomand,&nbsp;Bashir Movahedian","doi":"10.1016/j.istruc.2024.107599","DOIUrl":"10.1016/j.istruc.2024.107599","url":null,"abstract":"<div><div>In this paper, the formulation of time weighted residual method has been extended to study wave propagation in planar frames and trusses with shear deformable elements. Timoshenko beam theory (TBT) was used to take into account the shear deformations. The salient feature of the method is that, although propagation of waves along the elements, with distributed mass, is fully taken into account, it uses the degrees of freedom (DOFs) defined just at joints of the structures, making the whole analysis simple and efficient compared with finite element method (FEM). To demonstrate the accuracy and efficiency of the proposed method, two experimental setups (i.e., portal frame under moving mass and hammer impact load) were designed and fabricated to measure the frame displacements. The experimental results are presented for the first time in this paper. The digitized results from the experiments and those found from the proposed numerical method, and also those from the FEM, are presented and compared to demonstrate the capabilities of the method. We shall show that, while the FEM needs numerous DOFs to generate acceptable results, the presented method uses just one element for each structural member and still it is capable of generating very accurate results. It may be expected that the Euler-Bernoulli beam theory (EBT) could be suitable for slender beams since the transverse shear strains in this theory remain null. However, we shall show that this is true for relatively low frequencies for which the height of the structural member is significantly less than the wavelength. To demonstrate this, further numerical examples are presented to discuss the suitability of the two theories and also to show the efficacy of the proposed method compared to the FEM. The numerical results show that the proposed method is accurate and efficient in terms of computational cost.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107599"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Full robustness-based decision-making computational approach for RC structures subjected to multiple hazards","authors":"Mengxue Guo ,&nbsp;Hua Huang ,&nbsp;Kai Qian ,&nbsp;Bin Wang ,&nbsp;Chunliang Xue ,&nbsp;Min Huang","doi":"10.1016/j.istruc.2024.107638","DOIUrl":"10.1016/j.istruc.2024.107638","url":null,"abstract":"<div><div>Existing RC structures show accidental loadings vulnerabilities because of inadequate design detailing causing in premature failure. The installation of a certain reinforcement measure on the susceptible structure is a common option to mitigate these fragility. At this time, reinforcement measures aided by the participation of stakeholders are crucial to combat multiple hazards. However, previous studies did not necessarily dealt with the integration multi-hazard loss, multi-uncertainty, and dependence configuration in a performance-based engineering decision-making framework, to retrofit selection from the robustness of structures perspective. In this paper, an efficient fuzzy full robustness-based decision-making framework is proposed to tackle the challenge of integration of multi-uncertainty and dependence, and further to avoid biased strategies. This framework contained Probabilistic Multi-hazards Fuzzy Global Vulnerability (PMFGV), Loss (PMFGL), and Robustness Assessment (PMFRA) for structures, by incorporating the fuzzy theory and Vine-Copula tree structure. The mentioned robustness index can be used as a reference indicator in the rehabilitation and retrofitting planning. The PMFRA-based making-decision methodology is applied to RC structures with three design schemes, which were established the platform OpenSEEsPy. Results confirm that the established assessment framework is effective in evaluating actual RC structures’ robustness. The fuzzy full robustness index for the frame S-RC, SS-RC, and RS-RC, was &lt; 0.327, 0.421, 0.470 &gt; , &lt; 0.400, 0.503, 0.523 &gt; , &lt; 0.356, 0.453, 0.507 &gt; , respectively. Whether the robustness-cost-based or the Cumulative Prospect Theory-based, the robustness of the reinforcement strategy with the installation of secondary beam (SS-RC) outdistance that of the additional reinforcement ratio (RS-RC). Such parameters are suggested as reasonable and meaningful making-decision index for selecting the optimal retrofitting schemes for structures subjected to multiple hazards, which leads to a balance between the enhancement of full robustness and reduction of life cost.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107638"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-amplitude nonlinear vibrations characteristics of bi-directional functionally graded plate having microstructure defects in hygro-thermal environment","authors":"Varun Katiyar,&nbsp;Ankit Gupta","doi":"10.1016/j.istruc.2024.107484","DOIUrl":"10.1016/j.istruc.2024.107484","url":null,"abstract":"<div><div>The present article investigates the nonlinear hygro-thermal vibration characteristics of bi-directional functionally graded plates (BFGP) with microstructural defects. The distribution of material properties is anticipated to vary gradually along both thickness and length directions according to the modified power-law distribution. A novel expression has been developed to solve for the nonlinear temperature variation along the thickness of the BFGP. The micro-structural defects in terms of porosity have been incorporated in the formulation using a newly developed porosity model for a BFGP. A refined non-polynomial trigonometric higher-order shear deformation theory (HSDT) with a von Karman sense of geometric nonlinearity has been employed for the vibration response of BFGP. The finite element formulation has been carried out utilizing the C⁰ continuous Lagrangian quadrilateral element with nine nodes and eight degrees of freedom per node. The equations of motion have been derived using a variational approach. Various validation and comparative studies have been conducted to substantiate the current formulation's authenticity. The effect of the geometric nonlinearity, boundary constraints, volume fraction index along thickness (n) and volume fraction index along length (<em>q</em>), porosity index, temperature, and moisture concentration difference on the vibration frequency ratios (VFR) has been covered in depth. The VFR is more sensitive to the volume fraction indices (VFI) ' <em>n′</em> than <em>'q'.</em> Incorporating porosity decreases the VFR of BFGP, but it increases at higher amplitude ratios when BFGP becomes more porous. The VFR of BFGP exhibits nonlinear behavior with increasing moisture concentration and also varies non-linearly with the rise in amplitude ratio due to the hygro-thermal environment.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107484"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of near-field pulse-like ground motions on the seismic resilience of RC shear wall buildings","authors":"Mohsen Khademi ,&nbsp;Mohsen Tehranizadeh ,&nbsp;Amir Shirkhani ,&nbsp;Iman Hajirasouliha ,&nbsp;T.Y. Yang","doi":"10.1016/j.istruc.2024.107585","DOIUrl":"10.1016/j.istruc.2024.107585","url":null,"abstract":"<div><div>This paper examines the effects of near-field pulse-like earthquake ground motions (GMs) on the seismic resilience, repair cost and time, and structural collapse risk of low-to-high-rise selected multi-story RC structures with special moment-resisting frames (SMRFs) and shear walls. Selected 5-, 10-, and 15-story structures are designed based on a seismically active region where pulse-like GMs are more likely to occur. Two different sets of near-field GMs are chosen based on the recommendations of FEMA P-695 to conduct nonlinear dynamic analyses. Subsequently, the methodology provided in FEMA P-58 is adopted to perform a comprehensive seismic performance assessment at various hazard levels. It is shown that the consideration of the effects of near-field pulse-like GMs can considerably increase the risk of structural collapse in RC shear wall systems, based on the ratio of the pulse period of ground motion records to the elastic first mode period, in comparison to the near-field GMs without a pulse. It is concluded that the stated ratio is a crucial parameter to assess the risk to the life safety (LS) of low-to-high-rise RC buildings. For frequently occurring seismic intensities, repairable damage to nonstructural elements is the main factor contributing to the total expected economic loss in the studied buildings, irrespective of the selected GM set and the number of stories. In addition, the contribution of collapse and demolition due to residual drift in the estimation of repair time is significant for pulse-like GMs.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107585"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mesoscale simulation based optimization of fibre distribution and orientation in UHPFRC beams","authors":"Yuming Zhang ,&nbsp;Yaqi Li ,&nbsp;Zhenjun Yang ,&nbsp;Yongchang Wang","doi":"10.1016/j.istruc.2024.107584","DOIUrl":"10.1016/j.istruc.2024.107584","url":null,"abstract":"<div><div>The high cost of a large number of uniformly distributed and randomly oriented high-strength steel fibres severely limits the applicability of ultra high performance fibre reinforced concrete (UHPFRC) to engineering structures. In this study, two types of mesoscale modelling based optimization algorithms are proposed and applied to optimize the fibre orientation and distribution in UHPFRC beams to reduce the total amount of steel fibres. The first algorithm heuristically distributes fibres in regions with high tensile stresses only with their orientations parallel to the principal tensile stresses, considering that the steel fibres contribute little to the compressive strength but significantly to the tensile and flexural strength of UHPFRC beams. The second method optimises the beams’ topology into strut-tie models using algorithms such as SIMP and BESO and then adds steel fibres oriented longitudinally in the tensile ties. The load-carrying capacity and failure process of the optimised beams are then simulated and assessed using a meso-scale finite element modelling approach recently developed by the authors. Based on the results of steel-bar reinforced UHPFRC beams under 3 or 4-point bending, it was found that the usage of steel fibres could be reduced by up to 60 %, and the amount of UHPC and cement could be reduced by up to 50 %, respectively, without sacrificing the load-carrying capacities of the beams compared with the beams with uniformly distributed and randomly oriented fibres.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107584"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine learning-based sensitivity analysis of engineering demand parameters for a reinforced concrete wall-frame building","authors":"Nabajit Sarkar ,&nbsp;Kaustubh Dasgupta","doi":"10.1016/j.istruc.2024.107477","DOIUrl":"10.1016/j.istruc.2024.107477","url":null,"abstract":"<div><div>Ensuring the reliable execution of structural fragility assessments for future earthquake hazard scenarios demands a stochastic evaluation of the seismic performance of structures. This necessitates a probabilistic assessment of the seismic demand, which, in turn, requires a proper sensitivity analysis of the Engineering Demand Parameters (EDP) in relation to several input random variables. In general, uncertainties in structural capacity and in seismic hazard mainly account for the total variability of the structural seismic response parameters. This study presents a regression-based machine learning approach and Sobol sensitivity indices for investigating the relative importance of uncertain structural parameters on various EDPs for a Reinforced Concrete (RC) wall-frame building. The sensitivity analysis results indicate that the viscous damping ratio, concrete strength, and building mass significantly influence the scatter of different EDP values. A comparative study is also conducted to evaluate the impact of uncertainty in structural properties and ground motion records on various considered EDPs. The results suggest that ground motion variability exerts a stronger influence on the response variables at higher seismic intensity levels but is less pronounced at lower intensity levels as compared to uncertain structural parameters. Further, the evaluation of the impact of different sources of uncertainty on seismic fragility estimates indicates that uncertain structural capacity parameters have a greater effect on response variability than on the fragility estimates.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107477"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isolation effectiveness of lead rubber bearing on low-medium-speed maglev vehicle-bridge system under earthquake","authors":"Fenghua Huang ,&nbsp;Jinxiao Wang ,&nbsp;Yunlong Luo ,&nbsp;Nianguan Teng ,&nbsp;Bin Cheng ,&nbsp;Dachang Zhang","doi":"10.1016/j.istruc.2024.107652","DOIUrl":"10.1016/j.istruc.2024.107652","url":null,"abstract":"<div><div>The constructed maglev line generally extends for dozens of kilometers or even hundreds and thus inevitably passes across earthquake-prone regions, which exposes the viaducts to the potential risk of seismic damage. The leader rubber bearing (LRB), a commonly employed isolation support in highway and railway bridges to mitigate seismic responses, is expected to be applied into maglev line for seismic protection. However, research in this domain remains relatively scarce. This paper digs into the isolation effectiveness of LRB on low-medium-speed maglev vehicle-guideway system under earthquake. An analysis model for seismic responses of the maglev vehicle-guideway system incorporating LRB was formulated, where the maglev vehicle was simplified as a multi-rigid-body dynamic model with 50 degrees of freedom and accounted for actively-controlled electromagnetic forces. The fast nonlinear analysis technique was introduced to solve such complicated nonlinear system. Then, the seismic isolation effectiveness of LRB on the vehicle-guideway system was thoroughly investigated, and a parametric study was conducted to identify the critical factors such as pier heights and LRB dimensions that influence the isolation effectiveness. Additionally, the driving quality of vehicle moving on LRB-isolated bridge was studied to evaluate the applicability of LRB to maglev line bridge. It reveals that, the installation of LRB effectively reduces the seismic responses of bridge but enlarges the vehicle responses under earthquake. Factors including pier height, LRB initial elastic stiffness and yield force exhibit significant influence on the seismic-reduction rate for the coupling system. It is recommended that the isolation degree of LRB should not exceed 2.50 during the design of LRB-isolated bridge, thereby achieving a balance between seismic isolation effectiveness of LRBs and vehicle driving quality.</div></div>","PeriodicalId":48642,"journal":{"name":"Structures","volume":"70 ","pages":"Article 107652"},"PeriodicalIF":3.9,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}