Performance Of Such Structures Research Articles

Experimental and numerical investigation of the seismic behavior of reinforced concrete frames with restricted ductility

In recent decades, the concept of special ductility has been commonly used to design reinforced concrete frames to resist strong earthquakes. There are numerous situations where strong earthquakes impose restricted ductility demands, e.g., structures governed by gravity loads or wind loads rather than seismic loads, and frames with geometric properties such that the dimensions prevent formation of plastic hinges at the ends of beams. To evaluate performance of such structures, this study has been conducted and emphasis is placed on intermediate reinforced concrete frames with code-conforming details. Shake table tests are conducted on a 3-story intermediate frame under a sequence of 9 incremental excitation records varying from 0.10 g to 0.60 g, representing minor to severe ground motions. A relatively satisfactory performance is observed: the maximum interstory drift ratio does not exceed 1.57 %, cracks are not localized at the ends of members but distributed along the spans of both beams and columns, and joints remain almost uncracked. To examine the effects of different parameters, a numerical model is developed and verified against the test results. Three essential parameters are considered: seismic event profile, span-to-depth ratio of the beam, and joint aspect ratio. The results show that the effects of different factors may be ranked from highest to lowest as follows: seismic event profile, aspect ratio of the beam-column joint, and span-to-depth ratio of the beam. The numerical analyses show that the frame will not exceed life safety limit under far field excitations and for joint aspect ratios larger than 0.9, but it may reach the threshold of collapse prevention limit under near fault earthquakes. Overall, the study sheds some light on seismic response of RC frames with restricted ductility and provides some indications of their feasibility as well as their limits in high seismic zones.

Probabilistic Prediction on Seismic Responses of a Long-Span High-Speed Railway Bridge Using BPINN

Efficient probabilistic prediction of seismic responses is crucial for assessing the seismic-resistant capability of long-span continuous girder high-speed railway bridges. Thus, a Bayesian physics-informed neural network (BPINN) is adopted to rapidly and effectively predict the probabilistic seismic responses of such bridges. The BPINN model combines deep learning and physics to improve the accuracy and consistency of predictions, while also quantifying the uncertainties using Bayesian inference methods. Various seismic excitations, including pulse, far-field and near-field types, are employed to probabilistically predict the seismic responses of the top of bridge pier. Evaluation metrics, including mean squared error and prediction interval coverage probability, are used to assess the deterministic and probabilistic estimates of BPINN. Results demonstrate that BPINN performs better in deterministic results for far-/near-field ground motions compared to pulse-like earthquakes, with most cases exhibiting a close approximation to the 95% confidence interval. The flexibility and adaptability of BPINN in handling different types of ground motions can provide valuable insights for assessing the seismic performance of such structures.

High-Energy–Density Fiber Supercapacitors Based on Transition Metal Oxide Nanoribbon Yarns for Comprehensive Wearable Electronics

AbstractFiber supercapacitors (FSs) based on transition metal oxides (TMOs) have garnered considerable attention as energy storage solutions for wearable electronics owing to their exceptional characteristics, including superior comfortability and low weights. These materials are known to exhibit high energy densities, high specific capacitances, and fast redox reactions. However, current fabrication methods for these structures primarily rely on chemical deposition, often resulting in undesirable material structures and necessitating the use of additives, which can degrade the electrochemical performance of such structures. Herein, physically deposited TMO nanoribbon yarns generated via delamination engineering of nanopatterned TMO/metal/TMO trilayer arrays are proposed as potential high-performance FSs. To prepare these arrays, the target materials were initially deposited using a nanoline mold, and subsequently, the nanoribbon was suspended through selective plasma etching to obtain the desired twisted yarn structures. Because of the direct formation of TMOs on Ni electrodes, a high energy/power density and excellent electrochemical stability were achieved in asymmetric FS devices incorporating CoNixOy nanoribbon yarns and graphene fibers. Furthermore, a triboelectric nanogenerator, pressure sensor, and flexible light-emitting diode were synergistically combined with the FS. The integration of wearable electronic components, encompassing energy harvesting, energy storage, and powering sensing/display devices, is promising for the development of future smart textiles. Graphical Abstract

Deterministic and stochastic finite element modeling of reinforced concrete beams without stirrups containing plastic wastes

PurposeThe use of waste polyethylene terephthalate (PET) plastics derived from shredded bottles in concrete is not formalized yet, especially in reinforced members such as beams and columns. The disposal of plastic wastes in concrete is a viable alternative to manage those wastes while minimizing the environmental impacts associated to recycling, carbon dioxide emissions and energy consumption.Design/methodology/approachThis paper evaluates the suitability of 2D deterministic and stochastic finite element (FE) modeling to predict the shear strength behavior of reinforced concrete (RC) beams without stirrups. Different concrete mixtures prepared with 1.5%–4.5% PET additions, by volume, are investigated.FindingsTest results showed that the deterministic and stochastic FE approaches are accurate to assess the maximum load of RC beams at failure and corresponding midspan deflection. However, the crack patterns observed experimentally during the different stages of loading can only be reproduced using the stochastic FE approach. This later method accounts for the concrete heterogeneity due to PET additions, allowing a statistical simulation of the effect of mechanical properties (i.e. compressive strength, tensile strength and Young’s modulus) on the output FE parameters.Originality/valueData presented in this paper can be of interest to civil and structural engineers, aiming to predict the failure mechanisms of RC beams containing plastic wastes, while minimizing the experimental time and resources needed to estimate the variability effect of concrete properties on the performance of such structures.

Compressive strength ratios of concretes containing pozzolans under elevated temperatures

Cement production is one of the major pollution contributors owing to its large rates of energy consumption and gas emission. Moreover, high temperatures could detrimentally impact the concrete infrastructure and thus, it would be essential to study performance of such structures under exposure to the elevated temperatures. In this paper, post-heat performance of the concrete whose cement has been added by zeolite and bentonite at ratios of 6 and 10% (by cement weight) under exposure to temperatures of 28, 150, 300 and 700 °C, was studied. Based on the results, replacing cement by zeolite and bentonite at the age of 90 days under ambient temperature, increases the compressive strength compared to the control specimen. Moreover, it was observed that heating the cubic and cylindrical specimens containing 10% bentonite at 150 °C, increase the compressive strength by 40%. Conversely, the results indicate that when exposed to temperatures of 300 and 700 °C, a decreasing trend is seen in the tensile strength of both cubic and cylindrical specimens containing the pozzolans. Peak intensity of C–S–H has dropped as per rise in temperature from 28 to 700 °C. These values reveal that peak intensity of C–S–H up to 300 °C, is approximately the same but under 700 °C, it has reduced considerably. In all the cubic and cylindrical specimens, it can be seen that the specimens heated at 150° have the highest compressive strength and the specimens heated at 700 °C have the lowest compressive strength compared to the same unheated specimens. The XRD patterns at 150 and 300 °C, reveal decrease and increase in the Portlandite content the difference between conversion ratio of the cubic and cylindrical specimens in this study, to the values provided by the codes, is less than 10%.

Study on the damage mechanism and hysteretic performance of fork column-dougong connection in traditional Chinese multi-story wooden structures

Fork column-dougong connection is an essential part in traditional Chinese multi-story wooden structures and its hysteretic performance is critical to the seismic performance of such structures. In this paper, a full-scale model consisting of a fork column and a dougong was fabricated and subjected to the pseudo-static cyclic load. Two types of damage patterns of the fork column were found and their inherent mechanism were revealed. The deformation features and hysteretic curves were studied and discussed. Results show that the constraint-induced and embedment-induced cracks are the two major damages of the connection, which both makes the cracks of column initiate at the interface with the dougong and propagate upwards. The rotation of the fork column accounts for about 90 % of the loading deformation and the proportion grows with the increase of the loading amplitude. The hysteretic curve of the connection is almost symmetric and each hysteresis loop seems fusiform, while the damping coefficient is slightly smaller compared with dougong alone.

Environmental implications of styrofoam waste and its utilization as lightweight fill material for embankment construction

This study investigates the adverse effects of styrofoam waste on the environment due to its non-biodegradable nature and persistence in natural ecosystems, encompassing issues such as visual pollution, habitat disruption, and potential health risks to flora and fauna. The research also delves into the feasibility of repurposing styrofoam waste as a lightweight fill material in embankment construction, aiming to improve the performance of such structures, with the primary objective of augmenting the structural performance of such constructions. The paper conducts an extensive assessment of the technical properties and engineering characteristics of a soil-styrofoam mixture. Key parameters under scrutiny encompass density, shear strength, and bearing capacity behaviors. Various proportions of styrofoam, specifically 0.0%, 0.2%, 0.4%, 0.6%, and 0.8% by weight, were systematically incorporated into the soil mixture. Based on this study, the use of styrofoam can reduce the maximum dry density of the soil mixture, but still has the desired bearing capacity. These results indicate that the reuse of Styrofoam waste as an additional material in embankment construction has great potential to improve the performance and sustainability of embankment projects.

Parametric Optimization of Circular Elevated Water Tanks Under Various Capacities and Seismic Conditions

The elevated water tank comprises important structural elements which includes slabs, beams, columns, and footings, facilitating the transfer of loads amongst these contributors and subsequently to the subgrade of the soil. This paper goals is to comprehensively analyze the structural behaviours exhibited by elevated water tanks underneath various loading conditions. The behaviours of multiplied water tanks variety underneath various styles of loadings, inclusive of dead, live, and seismic loads, that are comprehensively analyzed. This paper primarily aims to conduct a hydrostatic evaluation of circular water tanks and emphasizes the necessity of a parametric study. To obtain this goal, 2, 2.5, and 3 lakh litters of tanks are being considered for the analysis which are all examined underneath area III seismic situations whilst keeping a normal height and varying diameters during the simulation. The examination focuses on carrying out a comparative evaluation of critical structural parameters, such as moment, maximum displacement, and maximum base shear. By means of analysing those parameters across various tank capacities, precious insights into the structural reaction of circular elevated water tanks under seismic loading conditions are gained. Those findings contribute to enhancing the design and overall performance of such structures, enhancing their resilience and protection in earthquake-susceptible regions.

Limit analysis of multi-ring masonry arches: a parametric study on the effects of friction angle, geometry, interlocking, and ring number

The majority of built heritage covering large spans are built with curved masonry components, such as multi-ring arches, to attain greater overall thickness. Their ultimate structural capacity when subjected to external loads is significantly influenced by the various construction techniques utilized. Such structures are made up of independent rings that communicate with one another through interface contacts, and the geometrical features, like size, orientation, and the arrangement of units, play a significant role, as do the mechanical characteristics, like friction. Multi-ring arches subjected to a vertical load at quarter span are assessed utilizing an in-house code implementing the upper bound approach of the limit analysis for masonry structures. The formulation of a script for geometry generation has been given and used for the input to the code. A discrete model has been adopted accounting for a combination of size and disposition of blocks, friction angle, number of rings and the span length are taken into account. Following their combination of impacts in terms of collapse multipliers, which are classified as per respective influencing parameters, each one’s importance was demonstrated by classifying them into two major groups as per unit size. The outcomes showed that all the parameters were key influencing factors in the performance of such structures. Using relatively larger units enhanced the impact of interlocking and provided larger collapse multipliers. While interlocking played a more significant role when span was considered, it together with friction had a larger impact when ring number was varied, such that better interlocking and larger friction values provided higher collapse multipliers.

Simulation of a multimaterial model for modified auxetic structures

Auxetic structures, which is a term used to describe materials with a negative Poisson’s ratio, show beneficial properties like a low density, a high energy absorption capacity and an increased indentation resistance. This enables applications in many fields, such as aerospace and sports industries. Given their potential, many studies have already been conducted. Previously, the geometry of a selected auxetic re-entrant structure was optimized to maximize its mass-specific energy absorption capacity for ideal usage in lightweight applications. Moreover, a homogeneous material was used, whereas the combination of multiple materials could drastically increase the performance of such structures. Hence, in this study the use of two different materials combined into a modified re-entrant structure is investigated via Finite Element simulation. The Poisson’s ratio could thus be improved, which leads toa more pronounced and longer lasting auxetic effect.

Cyclic pushout tests on high‐performance concrete‐filled steel tube columns for seismic applications

AbstractConcrete‐filled double steel tube columns (CFDST) made from high‐performance materials represent an advanced type of prefabricated composite components with excellent fire performance, enabling a slender design under high loading compared to traditional concrete‐filled steel tubes (CFST). CFST have been proven to be a viable solution under seismic loading, as they can achieve improved load‐carrying capacities (improved stiffness, strength, ductility, and energy dissipation capabilities) compared to conventional concrete columns. However, there is currently a lack of experimental and numerical investigations on CFDST.This paper presents experimental results on five load‐reversal pushout tests on high‐strength CFDST columns. The objective was to investigate the bond behavior between steel and concrete, as well as the accompanying adhesion, micro‐, and macro‐locking effects under cyclic loading in order to better assess the seismic performance of such structures. The results showed a continuous decrease for the interface carrying capacity as well as for the overall bond stress behavior for each new loading cycle. However, macro‐locking represents the dominant mechanism for composite strength and is strongly influenced by the geometric shape of the high‐strength steel tubes. Even in post‐interface carrying capacity range, significantly higher bond stress states were reached.

Soft computing models for assessing bond performance of reinforcing bars in concrete at high temperatures

The bond between steel and concrete in reinforced concrete structures is a multifaceted and intricate phenomenon that plays a vital role in the design and overall performance of such structures. It refers to the adhesion and mechanical interlock between the steel reinforcement bars and the surrounding concrete matrix. Under elevated temperatures, the bond is more complex under higher temperatures, yet having an accurate estimate is an important factor in design. Therefore, this paper focuses on using data-driven models to explore the performance of the concrete-steel bond under high temperatures using a Gene Expression Programming (GEP) soft computing model. The GEP models are developed to simulate the bond performance in order to understand the effect of high temperatures on the concrete-steel bond. The results were compared to the multi-objective evolutionary polynomial regression analysis (MOGA-EPR) models for different input variables. The new model would help the designers with strength predictions of the bond in fire. The dataset used for the model was obtained from experiments conducted in a laboratory setting that gathered a 316-point database to investigate concrete bond strength at a range of temperatures and with different fibre contents. This study also investigates the impact of the different variables on the equation using sensitivity analysis. The results show that the GEP models are able to predict bond performance with different input variables accurately. This study provides a useful tool for engineers to better understand the concrete-steel bond behaviour under high temperatures and predict concrete-steel bond performance under high temperatures.

A theoretical investigation to boost the efficiency of CZTS solar cells using SCAPS-1D

Cu2ZnSnS4 (CZTS) is predicted to be an efficient absorber than CIGS due to its cost effective, earth inabundant constituents. But, it reached a maximum experimental efficiency of 12.6% in 2013 and it remains the same for the past decade. This is due to the various crystallographic factors that limit the performance of CZTS like antisite defect formation, unfavourable band alignment with n-type CdS, etc. The major objective of this article is to identify potential strategies through which CZTS research can be pursued further using Solar Cell Capacitance Simulator (SCAPS) 1D simulator. First, it deals with understanding the difference between CZTS and its derivatives Cu2ZnSnSe4 (CZTSe) and Cu2ZnSn(SxSe1−x)4 (CZTSSe). Then, in pursuit of finding an alternative to n-CdS, the performance of various n-type semiconductors is investigated. Later, bandgap-graded structures using exponential and linear gradient laws are constructed and the performance of such structures is evaluated. Cation-substituted CZTS structures like (Ag1−xCux)2ZnSn(SxSe1−x)4(ACZTSSe) and Cu2Cd1−xZnxSn(SxSe1−x)4 (CCZTSSe) are discussed and the performance characteristics of such devices are also studied.

METHOD OF ACCELERATED MATERIAL TESTING METAL CON-STRUCTION BASED ON MULTIPHASE ALLOYS

Purpose. Based on the quantitative assessment of the corrosion rates of multiphase metals and alloys, methodology for accelerated corrosion tests under conditions of electro-chemical corrosion with the determination of corrosion rates for each phase and mass corrosion damage of metal structures during the specified time of their operation was developed.
 Research methods. Achieving the solution of the set goal is based on the application of computational and experimental methods of evaluating the electro-chemical corrosion of multi phase alloys with the determination of corrosion rates for each phase separately and oxidation rates in general for the alloy.
 Results. The final formula and methods of conducting laboratory experiments on the assessment of corrosion rates of multi phase alloys were obtained. Methods of accelerated corrosion tests based on preliminary laboratory studies with accurate calculation of technological parameters prolonged during the operation of a real structure in conditions of electro-chemical corrosion are given.
 Scientific novelty. New mechanisms for estimating the corrosion rates of individual phases of multiphase alloys of the residual micro-heterogeneity of the corrosion surface under conditions of an uncertain total thickness of the corrosion layer was shown. An algorithm for calculating the technological parameters of accelerated tests, equivalent to the real conditions of operation of metal structures based on multiphase alloys during the given period of operation, is proposed.
 Practical value. The proposed approach makes it possible to determine the quantitative parameters of electrochemical corrosion of metal structures, calculate the reduction in load-bearing capacity, and assess the performance of such structures during a given period of operation.

Self-healing performance of a microcapsule-based structure reinforced with pre-strained shape memory alloy wires: 3-D FEM/XFEM modeling

Combination of microcapsules and shape memory alloys (SMAs) is one of the promising self-healing mechanisms. Although there are several parameters which affect the performance of such structures, limited studies are performed on this combined healing mechanism. In this work, we study the performance of such a composite structure using a 3-D finite element and extended finite element model consisting of matrix, glass microcapsule, healing agent, and Ni-Ti SMA wire. After examining the results, the effect of shape memory alloy wires on increasing the maximum fracture stress was observed. Moreover, the effect of radius of shape memory alloy wires, initial crack location, thickness ratio and volume fraction of microcapsules, and interface strength on ultimate fracture stress are investigated. Also, as a key parameter in self-healing performance, the crack opening distance decreased from 5 to 0.008 μm using 0.5% volume fraction of shape memory wires without pre-strain. In the case that the wires have a pre-strain of 1%, this value reaches almost zero and a compressive stress is induced between fracture surfaces which can enhance the healing process and adherence of healing agent.

Data-driven prediction of critical flutter velocity of long-span suspension bridges using a probabilistic machine learning approach

Among the consequences of wind-induced excitation on long-span cable-supported bridges, flutter instability is the most dangerous and can collapse bridge structures. Until now, the flutter velocity of long-span bridges can be computed after conducting an experimental wind tunnel test or by means of computational fluid dynamics (CFD). However, the approaches mentioned above are cost-prohibitive and time-consuming especially when there are many sampling designs to evaluate. Therefore, it is crucial to develop an alternative solution for evaluating the flutter performance of such structures while minimizing the associated cost and computation time without worsening the accuracy of the results. Scholars have proposed machine learning (ML) techniques to address this issue. Unfortunately, some ML techniques do not provide excellent generalization for small datasets and are prone to bias even when the accuracy is relatively high. Besides, conventional ML models do not consider the uncertainty in data. This study proposes a probabilistic machine learning approach to overcome the weaknesses of the conventional ML models. The dataset used to train the proposed model was generated from 73 sampling designs using a fully numerical approach that involved 2D URANS (Unsteady Reynolds-averaged Navier-Stokes) CFD simulations, quasi-steady flutter theory, finite element model, and multi-mode approach for critical flutter velocity computation. The deck cross-section's most influential parameters and the critical flutter velocity constitute the datasets used to build the proposed probabilistic machine learning model. Our finding substantiates that the probabilistic machine learning approach based on hierarchical Bayesian modeling (PML-HBM) overperformed the conventional machine learning models, including extreme gradient boosting regression (XGBR), random forest (RF), and the support vector regression(SVR). Therefore, PML-HBM can accurately predict the critical flutter velocity. This model is an interesting approach to circumvent the time and cost associated with wind tunnel tests and CFD simulations at the earlier design stage of long-span bridge aerodynamic study.

Effect of blast location and explosive mass on the dynamic behavior of a bowstring steel highway girder bridge subjected to air-blast

Steel bridges are preferred for their lesser construction time and are used in territorial border areas, to develop road connectivity between neighboring countries, and also in the existing busy railway tracks to construct underpass and roads over bridges. Bridges are also quite commonly enquired in the Indian railway network for the railway tracks to cross over the nullas and rivers. Thus, steel bridges are also the part of infrastructural lifeline system of a country. The safety performance of such structures under explosive loading during warfare and subversion too is of serious concern to researchers, engineers, and other government officials. A few research papers addressing the dynamic behavior of steel bridges subjected to explosive loading are available in the literature. The objective of this study is to simulate the behavior of a bowstring steel girder bridge using the ABAQUS nonlinear finite element analysis software and investigate its response under air-blast loadings considering various detonation scenarios in terms of location and mass of the explosive charge. Johnson-Cook (J-C) damage model has been adopted to simulate the non-linear behavior of the steel. The main parameters affecting the behavior of bridge under blast load above the surface are investigated such as explosive weight (W), the distance from the explosion source to bridge (S), and location of explosion. The blast load is modelled as a pressure function of the stand-off distance and the equivalent mass of TNT. The load-carrying mechanism, stress profiles, and dynamic responses such as maximum displacement are discussed and compared. Based on the computed results, the most critical location of the explosives is assessed. It has been found that the severe eccentric explosive loading on the deck other than at the supports is found detrimental and makes the bridge almost irreparable. Damage to the bridge is directly proportional to the explosive weight and inversely proportional to the standoff distance.

Effects of geogrid reinforcement on the seismic performance of lightweight embankments

Highway embankments have experienced earthquake induced damages from minor to catastrophic scales during the past few decades despite the fact that highways are considered as major lifelines that should be in continuous operation under any circumstances. Recent advances in highway engineering suggest that geosynthetic reinforcement can be considered as a novel approach to mitigate the earthquake hazards on highway embankments successfully. The use EPS geofoam inclusions is one of the prominent improvement methods available to increase the seismic performance of lightweight embankments. It’s a well-known method to reduce the magnitude of earthquake-induced dynamic forces. The aim of this numerical study is to determine the effects of using geogrid reinforcement on the seismic performance of lightweight embankments. Non-linear dynamic analyses were performed using the PLAXIS software using real earthquake records. Evaluation of the results reveal that inclusion of geogrid reinforcement layer beneath the lightweight embankment model successfully decreases earthquake-induced dynamic forces and increases the seismic performance of the embankment model in comparison of the nominally identical structure with no geogrid reinforcement. Numerical results obtained from this novel technique suggest that the implementation of a geogrid layer beneath such lightweight embankments can successfully and effectively increase the seismic performance of such structures.

Evaluating bioretention scale effect on stormwater retention and pollutant removal.

Bioretention column studies are commonly used in laboratory to assess the performance of such structures in removal of pollutants and to investigate different conceptions aiming to increase their efficiency. However, no studies were found recommending suitable diameters or sizes, or about the uncertainties related to the transfer of results among the different scales (i.e., among different experiments or from the laboratory to field scale). This study assessed the effect of the varying diameters in experimental bioretention columns on the retention and removal of pollutants from stormwater runoff. Three sets of columns with diameters of 400mm, 300mm, and 200mm were assessed. The results showed that runoff retention (R) was affected by the time interval between stormwater events, but not by the bioretention diameter, although the diameter influenced the variability of R results. The removal of TSS (95%), nitrite (98%), and phosphate (96%) did present variability among the different bioretention diameters. However, the nitrate removal was statistically different among the bioretention columns, with removal efficiency above 50% in the 300-mm and 200-mm columns, while the 400-mm columns acted as a source of nitrate by increasing its concentration in the outflow stormwater by up to 285%, suggesting that the removal of this pollutant can be influenced by the scale effect of the bioretention columns and the experiments with small bioretention diameters may not provide reliable results.

Energy absorption of multilayer aluminum foam-filled structures under lateral compression loading

This article proposes a biomimetic multilayer foam-filled structure (BMFS) that mimics the microstructural characteristics of biological structures such as human bone and whale baleen. The lateral compression performance of such structures is investigated using experimental and numerical analyses. The proposed structure consists of three layers of aluminum foam with different densities filled in several concentric circular aluminum tubes. The test includes a solid design (Design-1) and a hollow design (Design-2). A series of quasi-static compression tests and finite element simulations are conducted, and the results show that BMFS exhibits a more advantageous sequential collapse deformation pattern for practical use. An energy absorption analysis of each layer shows that the energy absorption ratio of the foam layer reaches 85%. Comparing Models 1–3 of the two designs shows that the energy efficiency decreases, and the work efficiency increases, as the foam density increases. In addition, the interaction between the tubes and foams enhances the energy absorption properties of the structure. The parameter study shows that the energy absorption characteristics of Design-2 are insensitive to the diameter of the tube. The SEA of Design-1 increases with the thickness of Tube-1.