Showing papers in "Structures in 2021"
TL;DR: In this article, the bending behavior of an advanced functionally graded ceramic-metal plate subjected to a hygrothermo-mechanical load and resting on a viscoelastic foundation is studied using a simple higher-order integral shear deformation theory.
Abstract: In this work, the bending behavior of an advanced functionally graded ceramic–metal plate subjected to a hygro-thermo-mechanical load and resting on a viscoelastic foundation is studied using a simple higher-order integral shear deformation theory. The power-law function in terms of volume fraction is used to vary the elastic material constituents through the plate's thickness. The in-plane displacement field uses a sine shape function which changes linearly through the plate thickness to calculate the out-of-plane shear deformation. Both the linear and nonlinear influence of temperature and moisture concentration on the bending response are investigated. For the first time, a three-parameter viscous foundation model is used to study the bending response utilizing the damping coefficient in addition to Winkler’s and Pasternak’s parameters. The governing equations are derived using the principle of virtual displacement, and the analytical solution is obtained by the Navier method. Non-dimensional numerical results is validated by existing results in the literature. A parametric investigation is established to discuss the effects of the power-law gradient index, temperature rise and moisture concentration, elastic foundation coefficients, and the viscoelastic damping coefficient on the FGM plate's bending response.
108 citations
TL;DR: A comprehensive review of major publications addressing the blast response of the reinforced concrete slabs is provided in this article, where the phenomenon of spall damage in the slab and the parameters affecting it are discussed, and different damage/failure modes of the slabs exposed to contact or close-in detonations are presented.
Abstract: Rising fanaticism and rapid industrialization across the globe make the structures more vulnerable to direct threats generated from accidental and explosion-induced air-blast loads. Unlike the response of the reinforced concrete structure under quasi-static loading, it may respond in a brittle manner with highly localized failure like scabbing, cratering, spalling, and crushing of the concrete as well as rupturing of the reinforcement under the near field or contact detonations. Large deflection and high stresses could cause irreparable damage or result in the failure of critical structural elements. Besides, high-speed secondary fragmentation resulting from spalling of concrete may cause injuries to the occupants and other damages in the detonation area. It is therefore important to have a better understanding of the structural response/damage under air-blast loadings. This paper provides a comprehensive review of major (over twenty) publications addressing the blast response of the reinforced concrete slabs. First, the phenomenon of spall damage in the slab and the parameters affecting it are discussed. Then, available experimental investigations on slabs have been reviewed and different damage/failure modes of the slabs exposed to contact or close-in detonations are presented. The damage in the slabs has been observed in the form of spalling of concrete, the formation of punching crater, concrete scabbing/crushing, flexure-shear failure, flexural failure, bending-punching failure, and development of longitudinal, transverse, and radial cracks. Next, numerical modeling of the slabs using various material damage models available in different finite element programs has been discussed by reviewing the numerical /analytical investigations under air-blast loading. It is noted that the vast majority of the papers focused on improving the blast resistance of the slabs using different strengthening techniques. Finally, the major findings and other aspects that need to be considered for subsequent research are discussed.
86 citations
TL;DR: A deep learning-based axial capacity prediction for cold-formed steel channel sections is developed using Deep Belief Network and it was found that the DBN was conservative by 9%, 6% and 8% for stub columns, intermediate columns, and slender columns, respectively.
Abstract: In this study, a deep learning-based axial capacity prediction for cold-formed steel channel sections is developed using Deep Belief Network (DBN). A total of 10,500 data points for training the DBN are generated from non-linear elasto plastic finite element analysis, which incorporated both initial imperfections, as recommended by the Australian/New Zealand Standard (AS/NZS 4600:2018) and residual stresses as recommended by Moen et al. A comparison against experimental results found in the literature was conducted. It was found that the DBN was conservative by 9%, 6% and 8% for stub columns, intermediate columns, and slender columns, respectively. When compared against a typical shallow artificial neural network (Backpropagation Neural Network) and a typical machine learning model (Linear regression model based on PaddlePaddle), it was shown that DBN performed around 2% better than both with the same training data. When the same comparison was made for both the Effective Width Method and the Direct Strength Method, it was found that they were conservative by 15%, 13%, and 15%, respectively. Based on the DBN output data, new and improved design equations for AS/NZS 4600:2018 were proposed.
63 citations
TL;DR: In this article, the effect of using glass powder alongside polypropylene fibers was investigated in different compression and flexural beam specimens, and the best rate for glass is 25% which causes an increase in the compressive and Flexural strengths of the concrete.
Abstract: Today a wide variety of tools and instruments are made from glass, and they need recycling after being wasted. However, their recycling process could harm the environment. In order to increase concrete ductility and strength against the flexural and compressive loads, one could implement polypropylene fibers to reduce the problems associated with concrete brittleness. In this study, in addition to adopting the environmental sustainability approach and applying glass powder, polypropylene fibers are used. In order to investigate the effect of using glass powder alongside fibers, different compression and flexural beam specimens are made and tested. The rates of used glass are 20, 25, and 30%, and the rates of used fibers are 0.5, 0.75, 1, 1.5, and 2%. Considering the amount of fiber and used waste glass powder, 24 types of compression specimens with dimensions of 15 × 15 × 15 cm and 12 types of flexural beam specimens with dimensions of 50 × 15 × 15 cm were prepared. Based on the test results, the best rate for glass is 25% which causes an increase in the compressive and flexural strengths of the concrete. Also, simultaneous use of 25% glass and 1.5% fibers results in best flexural and compressive strengths of concrete. Simultaneous use of waste glass powder (25%) and fibers (1.5%) improves the compressive strength, flexural toughness, and ductility in the beams by about 1.6, 4, and 13.2 times, respectively.
60 citations
TL;DR: In this paper, the authors made an in-depth investigation on the earthquake damages of various engineering structures in Nepal, and the reinforcement measures and suggestions were putted forward for post-earthquake reconstruction, which focused on the load transmission path of the structure.
Abstract: On April 25, 2015, a M8.1 earthquake happened near Pokhara, Nepal, and aftershocks occurred continuously which caused significant losses. In November 2015, the authors made an in-depth investigation on the earthquake damages of various engineering structures in Nepal. As the post-disaster reconstruction work has not been completed, up to this day, the current reconstruction work is still worthy of continuous attention. Firstly, the earthquake damage of typical frame and masonry buildings in Nepal was described and the causes of damage were analyzed. The reinforcement measures and suggestions were putted forward for post-earthquake reconstruction, which focused on the load transmission path of the structure, the enclosure structure, the beam-column joints, the integrity of the structure, house site selection and structural stiffness. With the help of the finite element software, the numerical modeling analysis of the wall reinforcement measures and a typical reconstruction house was carried out. The results show that the seismic performance of masonry wall can be greatly improved after being wrapped by reinforced concrete or seismic band, the use of seismic band in reconstruction of typical houses in Nepal can effectively improve the seismic performance of buildings. The surrounding areas of door and window openings are still the most vulnerable places to be damaged. Reinforcement should be strengthened in these locations.
54 citations
TL;DR: When compared with Backpropagation Neural Network and linear regression model based on PaddlePaddle, the proposed DBN outperformed these two methods, using the same big training data generated in this study.
Abstract: This paper proposes a deep-learning framework, specifically, a Deep Belief Network (DBN), for studying the web crippling performance of cold-formed stainless steel channel sections (lipped and unlipped as well as fastened and unfastened) with centered and offset web holes under the end-two-flange loading condition. G430 ferritic, S32205 duplex and 304 austenitic stainless steel grades are considered. A total of 17,281 data points for training the DBN are generated from an elasto plastic finite element model, validated from 69 experimental results reported in the literature. When a comparison was made against a further 53 experimental results reported in the literature, the DBN predictions were found to be conservative by around 10%. When compared with Backpropagation Neural Network (a typical shallow artificial neural network) and linear regression model based on PaddlePaddle, it was found that the proposed DBN outperformed these two methods, using the same big training data generated in this study. Using the DBN predictions, a parametric study is then conducted to investigate the effect of web holes, from which unified strength reduction factor equations are proposed. Finally, a reliability analysis is conducted, which shown that the proposed equations can predict the web crippling strength of cold-formed stainless steel channel sections under the end-two-flange loading condition.
50 citations
TL;DR: In this paper, the effects of basalt fiber content on uniaxial compressive mechanical properties and damage of concrete were investigated using 3D-digital image correlation to record the surface strain field and track the surface crack development.
Abstract: In this study, the effects of basalt fiber content on the uniaxial compressive mechanical properties and damage of concrete were investigated. Acoustic emission (AE) technology was adopted to collect the AE characteristic parameters (ringing count and energy) in the entire loading process, and the change trend of the characteristic parameters from initial compression to final complete failure was analyzed during the uniaxial compression test of basalt fiber-reinforced concrete (BFRC). 3D-digital image correlation was used to record the surface strain field and track the surface crack development in real time. Research results show that a proper amount of basalt fiber (6 kg/m3) can improve the compressive strength of concrete and reduce the density and intensity of AE characteristic parameters. The change in AE characteristic parameters is closely related to the stress–strain curve of BFRC and includes three stages, namely, initial compaction, stable crack propagation, and unstable crack propagation stages. With the increase in basalt fiber content, AE events are dispersed in concrete, effectively weakening the local damage. The strain contours show that adding a proper amount of basalt fiber can delay the early cracking and reduce the transverse strain of concrete. At the same time, the long cracks on the surface of BFRC gradually transform into many microcracks with the increase in basalt fiber content.
50 citations
TL;DR: In this paper, the effect of fibers on UHPGC properties including compressive strength, splitting tensile strength, flexural strength and modulus of elasticity was investigated.
Abstract: Using high amount of cement is one of the disadvantages of ultra-high-performance concrete (UHPC). To reduce this, it is tried to replace cement with certain alternative materials with industrial waste materials and disposal. In this research, Ultra-high-performance geopolymer concrete (UHPGC) based on ground granulated blast furnace slag (GGBFS) and silica fume containing steel fiber (SF) and polypropylene fiber (PPF) was investigated experimentally. For this purpose, series 1 of mix proportion has been used to determine the reference design with the highest compressive strength. In series 2, nine mixtures were used to investigate the effect of fibers on mechanical properties of the UHPGC including compressive strength, splitting tensile strength, flexural strength and also modulus of elasticity. Moreover, the chloride ion penetration resistance was evaluated through some specific tests such as electrical resistivity (ER), rapid chloride migration test (RCMT) and rapid chloride penetration test (RCPT). The results show that addition of PPF to the samples containing SF improves the mechanical and durability properties. Moreover, the results indicate that replacing the percentage of SF with PPF leads to reduction in the mechanical strength, although it causes the durability to be increased.
48 citations
TL;DR: The classic decoupling strategy for UBMDO, the framework of sequential design and uncertainty evaluation (SDUE), is introduced into U BMDO-RIV to reduce the computational burden and to tackle challenges of mixed uncertainties in engineering systems.
Abstract: Generally, the traditional uncertainty-based multidisciplinary design optimization (UBMDO) methods are based on the probability distribution information of random design variables and parameters. However, the probability distribution information needs to be obtained based on a large number of sample points. In many engineering structure design problems, for some uncertainties, it is difficult to obtain enough experimental samples to construct their accurate probability distribution, only the variation interval of them can be known. In this situation, mixed uncertainties exist in the engineering systems. Furthermore, with the increase in the complexity of engineering systems, these mixed uncertainties will even produce cumulative effects along with the internal coupling of the systems themselves. To tackle these challenges, the random and interval variables (RIV) are considered and a strategy of UBMDO with RIV (UBMDO-RIV) is proposed in this study. In the given method, the evaluation of uncertainty constraints is performed in the worst case scenario due to interval uncertainties. Meanwhile, the classic decoupling strategy for UBMDO, the framework of sequential design and uncertainty evaluation (SDUE), is introduced into UBMDO-RIV to reduce the computational burden. The engineering case study is utilized to illustrate the application of the proposed strategy.
44 citations
TL;DR: This review demonstrated that machine learning algorithms have established new research directions in bridge engineering, in particular for applications such as the form-finding of innovative long-span structures, structural reinforcement, and structural optimization.
Abstract: Machine learning is one of the key pillars of industry 4.0 that has enabled rapid technological advancement through establishing complex connections among heterogeneous and highly complex engineering data automatically. Once the machine learning model is trained appropriately, it becomes able to effectively predict and make decisions. The technology is rapidly evolving and has found numerous applications in various branches of engineering due to its preponderance. This study is focused on exploring the recent advances of machine learning and its applications in reinforced concrete bridges. It covers a range of different machine learning techniques exploited in structural design, construction quality management, bridge engineering, and the inspection of reinforced concrete bridges. This review demonstrated that machine learning algorithms have established new research directions in bridge engineering, in particular for applications such as the form-finding of innovative long-span structures, structural reinforcement, and structural optimization.
44 citations
TL;DR: In this article, a finite element analysis of cold-formed stainless steel channels with circular web holes, subjected to end-one-flange loading condition, is presented, where the effect of web hole size, web hole location and bearing length on the web crippling strength of such sections is investigated.
Abstract: This paper presents a finite element analysis of cold-formed stainless steel channels with circular web holes, subjected to end-one-flange loading condition. The material properties of stainless steel types EN 1.4509 (Ferritic), EN 1.4462 (Duplex) and EN 1.4301 (Austenitic) were taken from the literature. To investigate the effect of web hole size, web hole location and bearing length on the web crippling strength of such sections, a parametric study involving a total of 1728 FE models was performed. The parametric study results were used to propose new web crippling strength equations and strength reduction factor equations which outperformed the equations of American Society of Civil Engineers Specification (ASCE 8–02), American Iron and Steel Institute Specification and Australia/New Zealand Standard (AISI&AS/NZS) and Lian et al (2016). A reliability analysis was then performed, which showed that the proposed design equations can closely predict the web crippling strength of cold-formed stainless steel channels with and without web holes under end-one-flange loading condition.
TL;DR: KnitCandela as discussed by the authors is a free-form, concrete waffle shell with KnitCrete, a falsework-less formwork approach using a custom prefabricated knitted textile as multi-functional, structural shuttering layer and a form-found cable net as the main loadbearing formwork.
Abstract: This paper describes the structural design, digital fabrication and construction of KnitCandela, a free-form, concrete waffle shell with KnitCrete, a falsework-less formwork approach using a custom prefabricated knitted textile as multi-functional, structural shuttering layer and a form-found cable net as the main load-bearing formwork. The digitally designed and fabricated textile provided integrated features for inserting and guiding elements such as cables and inflatables that helped shape the sophisticated mould. With a total weight of only 55 kg, the 50 m2 formwork was easy and compact to transport. On site, the formwork was tensioned into a timber and steel rig, the pockets were inflated, and then coated with a thin layer of custom-developed, fast-setting cement paste. This paste served as a first stiffening layer for the textile, minimising the formwork’s deformations during further concrete application. Fibre-reinforced concrete was manually applied onto the formwork to realise a 3 cm-thick shell with 4 cm-deep rib stiffeners. The novel approach, for the first time applied at architectural scale in this project, enables the building of bespoke, doubly-curved geometries in concrete, with a fast construction time and minimal waste, while also reducing the cost and labour of manufacturing complex parts.
TL;DR: In this paper, the effect of different amounts of metakaolin and zeolite pozzolans on the mechanical properties and durability of concrete containing polypropylene fibers was investigated.
Abstract: Supplementary cementitious materials (SCMs), including industrial by-products or natural pozzolans are widely used as a partial replacement of ordinary Portland cement (OPC) in eco-friendly concrete, to reduce the carbon footprint and enhance mechanical and durability properties. Although many experiments have been conducted to study the effect of SCMs in concrete, the research on the effect of natural pozzolans on fiber reinforced concrete (FRC) is limited. This study investigates the effect of different amounts of metakaolin and zeolite pozzolans on the mechanical properties and durability of concrete containing polypropylene fibers. A total of 99 specimens were made in 11 experimental groups and the parameters of compressive strength, tensile strength, water absorption, porosity and density of concrete specimens were evaluated. In addition, concrete specimens were tested for ultrasonic pulse velocity (UPV) and atomic force microscopy (AFM) to further study the effect of natural pozzolans on the microstructure of concrete. The performance of FRC with natural pozzolans was compared to that of reference concrete and fiber reinforced concrete without SCMs. The results indicated that the polypropylene (PP) fibers were more effective in enhancing mechanical properties of concrete in the zeolite mixtures, so that the compressive strength and tensile strength compared to reference concrete increased by 44 and 22%, respectively, while the water absorption and porosity decreased by 48 and 45%, respectively. This is attributed to the higher viscosity of the zeolite-mixtures that allowed for a better dispersion of fibers in the mixture as well as the improved bond strength between fibers and paste due to the high pozzolanic activity of zeolite. The AFM analysis, UPV, density, and permeable voids test results revealed that the FRC mixtures incorporating natural zeolite had the most dense microstructure and the least porosity and defects among all examined FRC mixtures even compared to the mixtures that incorporated metakaolin with the same cement replacement level.
TL;DR: In this article, the authors present a concise state-of-the-art review on the use of Fiber Reinforced Polymers (FRPs) in bridge engineering, and organize commonly used FRP bridge components, and different materials/manufacturing techniques used for repairing and construction of FRP bridges.
Abstract: This paper presents a concise state-of-the-art review on the use of Fiber Reinforced Polymers (FRPs) in bridge engineering. The paper is organized into commonly used FRP bridge components, and different materials/manufacturing techniques used for repairing and construction of FRP bridges. Efforts have been made to give a clear and concise view of FRP bridges using the most relevant literature. FRPs have certain desired properties like high strength to weight ratio, and high corrosion and fatigue resistance that make them a sustainable solution for bridges. However, as FRPs are brittle and susceptible to damage, when safety is concerned, critical parts of the bridges are made as hybrids of FRP and conventional materials. Despite significant studies, it has been found that a comprehensive effort is still required on better understanding the long term performance and end-of-life recycling, developing cost-effective and flexible manufacturing processes such as 3D printing, and developing green composites to take full advantages of FRPs.
TL;DR: In this paper, the authors investigated the durability performance of self-compact high-strength concrete (SCHSC) by comprising silica fume and fly ash (mineral admixture), and waste marble slurry (WMS) as an alternative to cement.
Abstract: Production of self-compacting high-strength concrete (SCHSC) needs a colossal quantity of cement, which is perilous for the environment and economy. Researchers are intended to lower down the dependency on this cement and seeking for alternate green materials. The incorporation of industrial by-products together with mineral admixtures has been found suitable to minimize aforesaid problems. This investigation is, therefore, aimed to study the durability performance of SCHSC by comprising silica fume and fly ash (mineral admixture), and waste marble slurry (WMS) as an alternative to cement. The durability of such SCHSC mixes was evaluated by performing water permeability, chloride penetration, carbonation, corrosion, and drying shrinkage tests. X-Ray Diffraction (XRD) analysis was carried out for the microstructural formation of SCHSC mixes. The results revealed that the incorporation of mineral admixture and WMS improved the durability performance of the mixes. The durability parameters confirm the optimal performance of the SCHSC made with 10% of WMS and 15% of fly ash, with 5% of silica fume.
TL;DR: In this article, the flexural and shear performance of reinforced concrete (RC) beams made with recycled coarse aggregate (RCA), steel fibres (SF) and polypropylene fibres(PPF) are studied.
Abstract: Improving the flexural and shear performance of reinforced concrete (RC) beams plays a vital role in controlling the seismic behaviour of concrete structures. In this research, the flexural behaviour of RC beams made with recycled coarse aggregate (RCA), steel fibres (SF) and polypropylene fibres (PPF) are studied. A total of 54 RC beams with a cross-section 150 mm wide, 200 mm high, and a length of 1500 mm, with different transverse reinforcement spacing, are manufactured and tested. RCA from a building demolish is used as a replacement of natural coarse aggregate (NCA) at 0%, 50% and 100% (in term of mass). Moreover, SF and PPF are added to improve the flexural behaviour of the beams at 0%, 1% and 2% (in terms of volume). Specimens are tested under a four-point bending setup. In these tests, maximum flexural capacity, maximum deformation at mid-span of beams, ductility and the stiffness of specimens are measured. It was found that the influence of PPF on improving the flexural capacity of RC beams is higher than those made by SF; however, the effect of SF on deformation is more significant.
TL;DR: In this paper, the authors developed an FE model using ABAQUS software to simulate the progressive collapse phenomenon of reinforced rubberized concrete frames and validated the proposed numerical model by comparing the FEM results with the experimental test observations.
Abstract: The progressive collapse of reinforced concrete structures usually starts as a local failure, which occurs because of abnormal loads. This can result in enormous economic losses and catastrophic extensive casualties. To avoid high costs of testing full-scale structures and save time, the implementation of the finite element method (FEM) is, therefore, inevitable. This paper aims to develop an FE model using ABAQUS software to simulate the progressive collapse phenomenon of reinforced rubberized concrete frames. The proposed numerical model is validated by comparing the FEM results with the experimental test observations. The numerical study is extended to include more ten models with different stories and details for further understanding of progressive collapse. Based on the results, the simulation model achieved good results compared to the experimental results. Moreover, the numerical models of full-scale frames satisfied the resistance requirements of progressive collapse according to the guidance.
TL;DR: The Improved Shuffled based Jaya (IS-Jaya) algorithm is proposed, which uses the concept of shuffling process to gain superior exploration capability in the search mechanism and can be an effective tool for solving discrete size optimization of skeletal structures.
Abstract: Jaya algorithm is a simple and efficient population-based metaheuristic algorithm. Besides its simplicity, it has free from any algorithm-specific parameters. Although it has these advantages, the Jaya algorithm suffers from some shortcomings including unwanted premature convergence and the possibility of being trapped in local minima due to insufficient population diversity. To alleviate these handicaps, this paper proposes an Improved Shuffled based Jaya (IS-Jaya) algorithm. The proposed optimization method uses the concept of shuffling process to gain superior exploration capability in the search mechanism. A mechanism that causes to escape from local minima is also incorporated into the original Jaya algorithm. The efficiency of the IS-Jaya algorithm is tested on discrete optimization problems and compared to those of Jaya algorithm, self-adaptive multi-population-based Jaya (SAMP-Jaya), and some other state-of-art optimization methods. Optimization results show that the proposed optimization method can be an effective tool for solving discrete size optimization of skeletal structures.
TL;DR: In this article, the impact of polypropylene (PP) fiber and steel fiber hybridization on the fracture characteristics of plain and rubberized concrete prisms was examined to identify the fibers' optimized mixture proportion.
Abstract: Currently, the researchers’ endeavors focus on the incorporation of recycled waste tires from worn-out tires, such as tires-rubber particles in the concrete mix, which contributes to solving the accumulated waste tires problem. However, the crumb rubber inclusion can result in a significant reduction in mechanical properties. Moreover, in fiber-reinforced concrete (FRC), hybrid fibers are more effective in arresting cracks macro/micro than a single fiber type. Therefore, using hybrid fiber is essential to address the problems of strength decline and sustainability, simultaneously. To this end, this study aims to examine the impact of polypropylene (PP) fiber and steel fiber hybridization on the fracture characteristics of plain and rubberized concrete prisms to identify the fibers’ optimized mixture proportion. Prism specimens, measuring 100 × 100 × 500 mm (width × depth × length) were, therefore, prepared for this purpose. The variables involve different ratios of PP fiber (0%, 0.1%, 0.175, 0.25%, 1.0%) and steel fiber (0%, 0.75, 0.825, 0.9%, 1.0%) with/without crumb rubber (1–2 mm in size) with a partial replacement ratio of 20% by volume of fine aggregate (natural sand). In experimental studies, FRC prisms with crumb rubber achieved more significant improvements in the fracture characteristics than those with/without crumb rubber. By contrast, the concrete compressive and tensile strengths decreased due to the crumb rubber replacement. The specimen, reinforced with hybrid 0.1% PP-0.9% steel fiber-reinforced rubberized concrete, produced higher levels of fracture energy of approximately 3716.6 N/m, i.e., 13 times higher than that of plain concrete. More importantly, the most significant improvement in compressive and tensile strengths has been observed for the mixture with hybrid 0.1% PP-0.9% steel fiber.
TL;DR: An experimental study according to EC4 on deconstructable steel-concrete composite bolted shear connectors is carried out to investigate the effect of various bolt size, concrete strength, bolt strength and clearance size between the precast concrete slab and bolt on the static behavior of this type of composite connection as discussed by the authors.
Abstract: An experimental study according to EC4 on deconstructable steel-concrete composite bolted shear connectors is carried out to investigate the effect of various bolt size, concrete strength, bolt strength and clearance size between the precast concrete slab and bolt on the static behaviour of this type of composite connection. Shear load capacity for the first bearing, average major slip at the first bearing, maximum shear load capacity per bolt, slip corresponding to the maximum shear load capacity, maximum average slip between the precast concrete slab and steel beam and failure modes are assessed. A total of 12 composite specimens were tested according to EC4 with different parameters using deconstrcutable bolted shear connectors. In addition, two steel-concrete composite connection specimens using welded headed stud shear connectors were tested as control specimens to determine the influence of prefabricated concrete panels and deconstructable friction-grip bolted shear connectors on the performance of the steel-concrete composite connection. The experimental results show that deconstrcutable steel-concrete composite bolted shear connectors have completely different behaviour compared to welded headed stud shear connectors. Furthermore, a 3D finite element model of the steel-concrete composite connection having precast concrete slabs and deconstructable bolted shear connectors was performed. Numerical model was verified against experimental results, and was shown to accurately simulate their observed structural behaviour.
TL;DR: In this article, the Baily-Norton formulation has been used for modeling the creep behavior of radiant tubes distortion of cracking furnaces in operation conditions by the finite element method (FEM).
Abstract: In this paper, radiant tubes distortion of cracking furnaces plants has been modeled in operation conditions by the finite element method (FEM). The coils are made of 25Cr 35NiNb, and Baily-Norton formulation has been used for modeling the creep behavior. Tubes operational pressure and temperature have been achieved by since coils to complete the cracking process have a limitation in reducing skin temperature. If to economic reasons and to reach the appropriate timeframe for production and fulfillment of sales obligations, operation time before decoking increases from 60 days to 62 days, high operation temperature in the final two days passes from temperature calculated by normal numerical integration techniques and field observations, respectively. Analysis results have compared increasing values of coil tubes length in real conditions. Due to the coils operational process, the parameters affecting their distortion have been investigated. The phenomenon of ballooning and excessive distortion has also been studied by changing tubes internal pressure.
TL;DR: This paper has studied and analyzed the time-varying reliability of the large and small gears in the one-stage gear transmission system and the mechanical structure of the system itself under the correlation of strength degradation and failure.
Abstract: In mechanical engineering, most mechanical structural systems are composed of many parts, so their structures are complex. When a mechanical structure fails, it is generally caused by various failure modes. When designers want to improve the quality of mechanical products in the design of mechanical products, reliability analysis can play an important role. It is indispensable in the design and manufacture of mechanical products, engineering use, repair and maintenance. Research on time-varying reliability of mechanical structures is of great significance in improving the quality of mechanical products and bringing more economic benefits to engineering. It has received extensive attention in both academic fields and practical engineering applications. This paper takes the time-varying reliability analysis of mechanical structures based on performance degradation as the research topic, focusing on the reliability analysis methods and techniques of mechanical structures such as Gamma degradation process, material P-S-N curve, mixed Copula function, and nested Copula function. The main research content is divided into three parts. (1) The Gamma degradation process and the P-S-N material probabilistic fatigue life curve are used when establishing the strength degradation random model of the mechanical system. It provides the theoretical basis of strength degradation level for time-varying reliability analysis of mechanical structure based on performance degradation. (2) Combine the mixed Copula function and the nested Copula function to establish a comprehensive failure correlation analysis model of the mechanical system. It provides a theoretical basis for failure correlation for time-varying reliability analysis of mechanical structures based on performance degradation. (3) The time-varying reliability analysis of the one-stage gear transmission system in the engineering example is carried out. Researched and analyzed the time-varying reliability of the large and small gears in the one-stage gear transmission system and the mechanical structure of the system itself under the correlation of strength degradation and failure.
TL;DR: An advanced macro-block model accounting for frictional resistances is used to calculate the onset load factors for two classes of local mechanisms in multi-storey URSM buildings: the rocking-sliding and the flexure mechanisms.
Abstract: Unreinforced stone masonry (URSM) buildings without a box-like behaviour are very vulnerable to out-of-plane failure modes in seismic prone areas. These may involve partial or total collapses of walls with severe civil protection implications in terms of hazard to people, structures, and road network in the surroundings. In this paper, an advanced macro-block model accounting for frictional resistances is used to calculate the onset load factors for two classes of local mechanisms in multi-storey URSM buildings: the rocking-sliding and the flexure mechanisms. Based on the application of the kinematic approach of limit analysis, the presented formulations are an upgrade of the load factors identified within the FaMIVE (Failure Mechanism Identification and Vulnerability Evaluation) procedure existing in the literature and developed by the last author. These take into account a revisited evaluation of the in-plane frictional forces for the rocking-sliding mechanisms and the torsion-shear-flexure interactions for the horizontal flexure mechanisms. Moreover, the position of the hinge along the height of the building is identified more accurately, since it can be found at the story level or between two storeys, depending on the accounted mechanism. Other innovative issues concern upgrades of the former formulations for the vertical and horizontal flexure mechanisms. The final perspective of the presented abacus of local mechanisms in multi-storey URSM buildings is the next implementation of the proposed formulations in the FaMIVE procedure, after a sensitivity analysis of the main physical and geometrical parameters affecting the “hierarchy” among the all possible mechanisms. The identification of the most probable mechanisms, through a comprehensive but at the same time relatively rapid assessment, can be very useful for civil protection purposes.
TL;DR: Results highlight that the self-centring behaviour is particularly sensitive to the number of storeys and tends to reduce with the increasing height of MRFs equipped with the proposed connections.
Abstract: Many recent research studies have focused on developing innovative seismic-resilient structural systems to reduce repair costs and downtime in the aftermath of an earthquake. In this regard, dealing with steel Moment Resisting Frames (MRFs), recent research works have demonstrated the benefit deriving from the adoption of both low-damage and self-centring column base connections, both in terms of damage and residual drifts reduction. Although several technologies have been developed in this direction, only a few research studies investigated the significant parameters influencing the self-centring capability of these systems. Within this framework, the present study investigates the influence of the frame layout (i.e., storeys and bays number) on the seismic performance, including the self-centring behaviour, of perimeter MRFs equipped with damage-free self-centring column bases previously studied by the authors. Nine case-study perimeter steel MRFs are designed and modelled in OpenSees. Incremental Dynamic Analyses are performed with a set of 30 ground motion records while monitoring both global and storey-level engineering demand parameters, including peak and residual interstorey drifts. Fragility curves are successively used to evaluate the self-centring capability of the structures. The present study provides insights on the use of the adopted connections for the residual drift reduction of MRFs and defines the boundaries of the investigated parameters for their application. Results highlight that the self-centring behaviour is particularly sensitive to the number of storeys and tends to reduce with the increasing height of MRFs equipped with the proposed connections.
TL;DR: In this article, a three-dimensional elastoplastic model is used for simulation of the fatigue life and the fatigue crack growth path of 2024 aluminum plate riveted joints, and the results showed that the geometric parameters and the rivet material have a significant effect on fatigue cracking in aluminum plates.
Abstract: The purpose of this paper is to numerically investigate the fatigue life and the fatigue crack growth path of 2024 aluminum plate riveted joints. For this purpose, according to field observations, the parameters affecting fatigue life are obtained. Relevant geometric parameters such as rivet shank length, hole diameter and dimensional tolerances, as well as the location pattern of the rivets and the material of the rivet joints are studied. In this study, modeling is performed to calculate the equivalent plastic strain using the finite element method. For this purpose, a three-dimensional elastoplastic model is used for simulation. The information obtained from the finite element method in this study made it possible to place the rivets in this type of joint for use in high safety structures such as the aerospace industry. Given the importance of the problem of crack growth in 2024 aluminum plates, having the geometrical and physical parameters of the problem, the goal is to achieve the exact path of crack growth and fatigue life of riveted joints. Fatigue crack growth simulation is performed on the samples using the boundary element method. The stress intensity factor for different loading modes is determined using the boundary element method. The results showed that the geometric parameters and the rivet material have a significant effect on fatigue cracking in aluminum plates.
TL;DR: The main parameters affecting the performance of 3D printed concrete are reviewed and potential methods to enhance these properties are discussed, which include novel reinforcement, material modification, rheology control, nozzle design, process improvements, and interlayer bonding.
Abstract: The application of additively manufactured, 3D printed concrete in the construction industry has been gaining attention in recent years. 3D concrete printing (3DCP) has potentials for mass customisation, and off-site and rapid manufacturing of complex structural and architectural components. However, 3DCP has many challenges such as competing rheological requirements, weak interlayer bonding, difficulty in integrating reinforcement, and anisotropic material behaviour. Therefore, material properties of printed concrete are often inferior to traditional mould cast and leading to poor structural performance. Thus, satisfying performance criteria for structural applications is the key challenge of 3DCP, methods for enhancing the material properties of 3DCP are required. This article reviewed the main parameters affecting the performance of 3D printed concrete and discussed potential methods to enhance these properties. Methods investigated in this article include novel reinforcement, material modification, rheology control, nozzle design, process improvements, and interlayer bonding. Lastly, this article discussed the performance of structural elements produced by 3DCP and proposed future research areas to advance this technology in the building industry.
TL;DR: In this article, the authors used dynamic life cycle assessment to convert greenhouse gas emission histories to key climate impacts using a simple dynamic model, and explored the implications for structural design decisions by comparing concrete, steel and timber options for a typical medium-rise building structure.
Abstract: The enormous environmental impact of construction is becoming increasingly apparent and unacceptable to many structural engineers, whose designs typically account for the majority of a building’s embodied carbon. It is timely, therefore, that consensus is forming around a methodology for calculating embodied carbon. This encourages the inclusion of all life cycle stages, from material production and construction, through use and eventual demolition, disposal and reuse. In practice, however, end-of-life processes are fraught with uncertainty and often ignored, despite the potentially large associated carbon fluxes. Further uncertainty exists when considering bio-based construction materials, which store carbon during use. There are no widely-accepted means of accounting for timing of these carbon fluxes, despite the long service life of most buildings. Could we consider whole-life carbon in a more holistic and climate-focused way? This article uses dynamic life cycle assessment to convert greenhouse gas emission histories to key climate impacts using a simple dynamic model. The implications for structural design decisions are explored by comparing concrete, steel and timber options for a typical medium-rise building structure. Concrete is found to have a higher impact than steel, with the climate response of both options dominated by the large initial emissions of material production and construction. Timber has the smallest impact, for this example, under a typical scenario with sustainable forest management and re-emission of sequestered carbon at end-of-life. The analysis takes a forward-looking approach to sequestration, with timing corresponding to the growth of replanted trees. An optimistic timber scenario, whereby future carbon-capture technology avoids most end-of-life emissions, demonstrates the possibility of structures with small long-term climate cooling effects. Conversely, in a hypothetical worst-case scenario where no replanting or subsequent sequestration occurs, the long-term warming effect of the timber structure is increased by the net emission of biogenic carbon. Although end-of-life processes are important in the long-term, particularly for timber, the analysis also highlights the importance of the initial emissions from material production and construction. These cause high rates of short-term temperature increase and prolonged accumulation of radiative heat for all the buildings, but the impacts are again lowest for timber. Most importantly, the investigation shows how dynamic life cycle assessment can be used to explore climate impacts in a comprehensive, graphical and unbiased way. As a simple extension to established methodologies for calculating embodied carbon, it is a powerful decision making tool in the climate emergency.
TL;DR: An effective machine learning model, namely artificial neural network (ANN), is developed for predicting the shear strength of squat flanged RC walls and an efficient graphical user interface platform has been established for facilitating the practical design process of the squat flange RC walls.
Abstract: The squat flanged reinforced concrete (RC) walls have been widely utilized in nuclear power plant and building structures. Nevertheless, the empirical equations in current design codes and published studies show a significant discrepancy in calculating the shear strength of the walls. The purpose of this study is to develop an effective machine learning model, namely artificial neural network (ANN), for predicting the shear strength of squat flanged RC walls. A total of 369 test results of squat flanged RC walls were collected from the literature and used to develop the ANN model. The results of the proposed model were compared with those of existing design codes and published studies. The comparisons emphasized that the developed ANN model in this paper can predict the shear capacity of squat flanged RC walls more accurately than the existing equations. Moreover, the effect of input parameters on the predicted shear capacity of the walls was sufficiently investigated. A predictive formula based on the ANN model, which can cover thirteen input parameters, was then proposed to compute the shear strength of the squat flanged walls. Additionally, an efficient graphical user interface (GUI) platform has been established for facilitating the practical design process of the squat flanged RC walls.
TL;DR: In this article, the flexural response of steel fiber-reinforced concrete (SFRC) incorporating recycled nylon granules (NG) and natural zeolite after exposure to elevated temperatures was investigated.
Abstract: Polymer wastes are categorized as highly recyclable materials from various aspects. An effective way to recycle these materials is to utilize them in the concrete industry to replace aggregates. Thus, the non-renewable natural resources are reserved, and the waste disposal problems are partly mitigated. This study investigates the flexural response of steel fiber-reinforced concrete (SFRC) incorporating recycled nylon granules (NG) and natural zeolite after exposure to elevated temperatures. In total, 216 specimens were produced, which contained steel fiber at 0, 0.75, and 1.25% of mix volume, NG at 0, 10, and 20% of sand volume, and a type of zeolitic framework at 10, 15, and 20% of cement weight to examine the effect of each variable on the compressive and flexural strength, stiffness, and load–deflection response of concrete mixes. A concise microstructural analysis was also conducted to characterize the microscopic properties of the concrete constituent materials using SEM, BSEM, and EDXMA spectroscopy. The obtained results indicated that adding natural zeolite to the concrete mixes improved the compressive and flexural strength, as well as the flexural stiffness capacity. It was also observed that NG helped enhance the flexural specifications of specimens at 300 °C. This was attributed to the clamping action of partially molten polymer, similar to the crack-bridging mechanism of the steel fibers. The ultimate deflection capacity of the specimens was also increased with increasing zeolite addition.
TL;DR: In this paper, the main causes of mesh-reinforced linings cracks or structure failures are summarized, and current challenges for mesh reinforced linings are examined, and the advantages of using steel fiber reinforced concrete (SFRC) for the realization of the tunnel linings is highlighted.
Abstract: The complicated tunnelling conditions and variable engineering demands have made numerous challenges of mesh-reinforced lining structures. Thereafter, the steel fiber reinforced concrete (SFRC) is said to be a reliable alternative to mesh-reinforced linings. This paper reviews the constituent materials and typical properties of SFRC. The main causes of mesh-reinforced lining cracks or structure failures are summarized, and current challenges for mesh-reinforced linings are examined. Also, the advantages of using SFRC for the realization of the tunnel linings are highlighted. Furthermore, design considerations and some practical cases on application performance of SFRC in tunnel linings are summarized. This review confirmed the positive effect of SFRC lining on rock displacement control, lining pressure reduction, and global and local stability of the support structures. The research provides solid insights for promoting the development of SFRC in tunnel linings.