Structural Age Research Articles

Prediction of confined compressive strength of concrete column strengthened with FRCM composites

AbstractNowadays, retrofitting and rehabilitation of deteriorated reinforced concrete structures are becoming a growing need of the construction industry instead of demolishing aged structures. The application of fabric‐reinforced cementitious matrix (FRCM) on the existing concrete structures is one of the sustainable solutions to retrofit the concrete structures. This study used machine learning (ML) models such as linear regression (LR), support vector machines (SVM), and adaptive neuro‐fuzzy inference systems (ANFIS) to estimate the compressive strength (CS) of columns wrapped with FRCM. The experimental dataset of 301 column specimens was collected including input parameters such as cross‐sectional properties, mechanical properties of concrete and steel, and characteristics of FRCM material. Apart from ML models, seven analytical models were also used to compare the accuracy and precision of ML models. The results illustrate that the ANFIS model outperformed other ML models and established itself as a dependable and precise model. The R‐value of the ANFIS model was 0.9816, whereas R‐values of 0.9269 and 0.9572 were achieved by LR and SVM models, respectively. In addition, the MAPE value acquired by the ANFIS model was 1.52% which was lower than those of the LR model by 73.24%, and the SVM model by 60.60%, respectively. As the precision of the ANFIS model was higher as compared with SVM and LR models, so, the developed ANFIS‐based mathematical model can be easily used to predict the CS of FRCM‐strengthened concrete columns. The developed model is accurate, economical, and fast; and can be utilized by FRCM applicators and structural designers.

Enhancing the Flexural Capacity of Deteriorated Low-Strength Prestressed Concrete Beam Using Near-Surface Mounted Post-Tensioned Carbon Fiber-Reinforced Polymer Bar

This study aimed to address the critical issue of age deterioration in prestressed concrete (PSC) structures by investigating the strengthening of aged PSC structures using a near-surface mounted (NSM) post-tensioned carbon fiber-reinforced polymer (CFRP). A total of nine PSC beams, each with a length of 6.5 m, were fabricated for a four-point bending test. Various experimental parameters were taken into account, including the strengthening method, compressive strength of concrete in the PSC beam, and the prestressing force of the PSC beam. The results indicated that the NSM post-tensioned CFRP strengthening system proved more efficient when compared to the NSM non-post-tensioned CFRP strengthening system. The flexural capacity of the NSM post-tensioned CFRP strengthening system, under the deteriorated low-strength PSC beam, increased by up to 30.9% compared to the PSC reference beam. Additionally, the experimental results were compared to a finite-element analysis, and a parametric study was conducted to examine the material properties of the PSC beam. Consequently, the NSM post-tensioned CFRP strengthening system is expected to be an effective solution for addressing the issue of deteriorated low-strength PSC structures.

An Analysis of the Fire Performance of Small-Scale Canadian Heritage Hardwood and Softwood

A common consideration in the rehabilitation of historic timber structures is addressing the concerns for fire safety. Heritage structures can have softwoods but depending on the time they were built they may also have hardwoods present. Currently, there is a lack of knowledge on the char rate of heritage hardwood and softwood. This study presents initial findings into the charring of these historic materials as they would be encountered in practice through samples taken from pre-existing aged timber structures in Canada that are greater than 100 years old. The materials were tested in a cone calorimeter following a modified ASTM 1354 procedure. Hardwood samples typically exhibited a faster charring rate than the softwoods but the charring rates converged at 1.05 mm/min when exposed to higher fluxes of 50 kW/m2. As rehabilitation and readaptation may require performance-based approaches such as structural fire modelling, a provisional framework for a numerical model using LS DYNA for historic timber members is presented. The objective is to identify future research and testing areas to develop a higher certainty model. In the a-priori model presented, results showed conservative charring rate results with charring trends seen in the experiment generally being followed.

Exploring physical aging in PIM-1 using molecular dynamics

This comprehensive study explored the aging process of PIM-1, a ladder polymer of intrinsic microporosity (PIM), by applying molecular dynamics simulations for the first time. Through detailed analysis, our work illustrates the evolution of the polymer structure from a loosely packed, less dense state of the pristine polymer to a more tightly packed configuration due to physical aging. For this purpose, a novel molecular dynamics (MD) methodology was employed in the process toward equilibration of PIM-1. This structural transition was quantitatively captured by measuring key parameters such as density, fractional free volume (FFV), cohesive energy density (CED), d-spacing, surface area, and gas permeabilities. The simulations demonstrate a noticeable increase in density by approximately 7 % in aged PIM-1 compared to a fresh sample. This increase in density is accompanied by a corresponding decrease in FFV, suggesting a more compact molecular arrangement. The impact of these structural changes is evident in the gas transport properties. Permeabilities of all gases tested, He, H2, O2, N2, CO2 and CH4, decreased by 33 %–80 %. Moreover, the selectivity of gas pairs like CO2/CH4 and O2/N2 exhibited increasing trends due to aging, as previously reported in experimental work. Structural analysis performed on the fresh and aged structures indicated collapse of free volume over aging, by disappearance of pores larger than ∼6.5 Å. Furthermore, no intrachain rearrangement was observed during physical aging in the ladder PIM-1 structure; rather, the aging resulted in increased interchain packing efficiency. Our methodology can be employed to other PIM architectures, such as polyimides of intrinsic microporosity (PIM-PIs) as well as low-free volume glassy polymers.

Effects of simulated groundwater solutions with different Ca2+ to Mg2+ concentration ratios on asymmetric electrodeposition in concrete

Electrodeposition is an emerging and unique method for the repair of concrete cracks, in particular, with great potential for the repair of aged asymmetric subsurface structures. However, the effect of groundwater solutions on the effectiveness of concrete repair by electrodeposition is not clear. Using an asymmetric electrodeposition repair device, this paper investigates the effect of simulated groundwater solutions with different Mg2+ to Ca2+ concentration ratios on the effectiveness of electric field-induced ettringite for repairing concrete cracks. Results show that the simulated groundwater solution has a negligible effect on the macroscopic repair effect on the electrolyte solution side, but allows a certain amount of Mg(OH)2 and CaCO3 precipitation to be generated on the simulated solution side. Meanwhile, compared with the deionized water group, the permeability coefficient is reduced from 2.05×10−6 cm/s to less than 7.65×10−7 cm/s at the repair age of 14 days. The total impedance is enhanced from 1322 KΩ to more than 1658 KΩ, with the lower the Mg2+ to Ca2+ concentration ratios, the lower the permeability coefficient and the higher the total impedance. Microstructure analysis suggests that as the concentration ratio of Mg2+ to Ca2+ decreases, the content of loose porous Mg(OH)2 decreases and the content of dense CaCO3 increases on the simulated solution side. Moreover, the size of the Mg(OH)2 particles on the simulated solution side, becomes larger and the amount of production decreases while the CaCO3 increases and changes from aragonite to calcite type.

The distribution, chronology and significance of late Holocene aged stone-based structures on Pitta Pitta Country, western Queensland

There is considerable discourse around the timing of Australia’s interior colonisation and whether environmental or technological impacts pushed people into occupying more arid environments. However, the general scarcity of rockshelter sites and the limited amount of research undertaken to date in central western Queensland has meant this region has only been peripherally considered in such debates. It is well recognised that, by the time Europeans began documenting lifeways in the region in the late 1870s, central western Queensland had given rise to complex and thriving Aboriginal societies, despite the boom-or-bust nature of its seasonal cycles. One of these is the Pitta Pitta people, who had a pivotal role in a vast trade network that traversed the Lake Eyre Basin, extending north to the Gulf of Carpentaria. The Pitta Pitta are also seemingly unique in that, as far as available data suggest, they are the only group in western Queensland to have used stone in their construction of gunyahs (huts), despite similar environmental and geographic conditions in adjacent areas to the east (Diamantina National Park) and south (Mithaka Country). Here we describe 70 stone-based huts spread across four site complexes on Marion Downs Station and use these to underpin discussions about Pitta Pitta lifeways in the late Holocene.

SPYGLASS. IV. New Stellar Survey of Recent Star Formation within 1 kpc

Young stellar populations provide a powerful record that traces millions of years of star formation history in the solar neighborhood. Using a revised form of the SPYGLASS young star identification methodology, we produce an expanded census of nearby young stars (age < 50 Myr). We then use the HDBSCAN clustering algorithm to produce a new SPYGLASS Catalog of Young Associations, which reveals 116 young associations within 1 kpc. More than 25% of these groups are largely new discoveries, as 20 are substantively different from any previous definition, and 10 have no equivalent in the literature. The new associations reveal a yet undiscovered demographic of small associations with little connection to larger structures. Some of the groups we identify are especially unique for their high transverse velocities, which can differ from the solar velocity by 30–50 km s−1, and for their positions, which can reach up to 300 pc above the galactic plane. These features may suggest a unique origin, matching existing evidence of infalling gas parcels interacting with the disk interstellar medium. Our clustering also suggests links between often-separated populations, hinting to direct structural connections between Orion Complex and Perseus OB2, and between the subregions of Vela. The ∼30 Myr old Cepheus-Hercules association is another emerging large-scale structure, with a size and population comparable to Sco-Cen. Cep-Her and other similarly aged structures are also found clustered along extended structures perpendicular to known spiral arm structure, suggesting that arm-aligned star formation patterns have only recently become dominant in the solar neighborhood.

Influences on the Housing Satisfaction of Middle-Aged Households Reflected in the Korea Housing Survey 2021

In research on housing welfare policy, there has been little interest in middle-aged households compared with young or elderly households. The purpose of this study was to explore influences on the housing satisfaction of middle-aged renter households using microdata from the Korea Housing Survey 2021. A statistical analysis of data was performed on a total of 2,709,152 middle-aged (aged between 40 and 64 years) Jeonse (lump-sum housing lease) renters and monthly renters with deposits, living in private rental housing units. The major findings were as follows. Firstly, there were significant differences in housing unit satisfaction and residential environment satisfaction among renter groups by age and rental type. Early-middle-aged Jeonse renters displayed the highest satisfaction with both housing units and the residential environment, while semi-elderly monthly renters with deposits displayed the lowest satisfaction. Secondly, living in aged structures or in apartment units exerted the strongest influences on housing satisfaction, which implies the need for residential area regeneration programs that consider the situation of rental households. Thirdly, living in Incheon and Gyeonggi-do was found to have a negative influence on housing satisfaction. Fourthly, upward filtering on tenure types or lease renewal of the current house did not necessarily have a positive influence on the housing satisfaction of middle-aged renters. Based on the findings, suggestions were made to improve the housing situation of middle-aged renter households.

Composites for Reinforcement of Damaged Metallic Aircraft Wings

Advanced composites, because of their inherent directional properties and ability to take complex contours are ideally suitable for repairs even in aged metallic aircraft structures. The composite materials can be suitably tailored to suit the strength and stiffness requirement at location of the damage on the parent structure. The laminate patch can be bonded to the structure. This avoids the use of large number of fasteners that are required for repair with metallic repair patch. A composite patch repair has been carried out on a military aircraft wing. The skin and the spar flange near the landing gear part were cut in order to gain access to a loosened bolt. With a request from HAL (Nasik), National Aerospace Laboratories (NAL) has taken the responsibility of designing and realizing composite repair at the damaged locations. The geometry and lay-up of the patches have been arrived at based on the strength requirements. The patches were fabricated at NAL and the repair was implemented on the aircraft. The quality of the patch bonding was checked using non-destructive testing (NDT). The aircraft has completed about 130 hrs flying with the repair. The repair was certified by the regulating authority and has been recommended to be implemented on other twenty aircraft also. This task has been completed successfully and all the aircraft are flying. This is an important achievement both for NAL and HAL (Nasik). This paper discusses the repair design, patch fabrication and implementation of the repair.

Predicting the shear behavior of reinforced concrete beams with Fe-Based shape memory alloy stirrups

Existing studies using Fe-based shape memory alloys (SMAs) for shear reinforcement have focused on strengthening aged structures. Studies on using Fe-SMAs as shear reinforcements for new structures have not been reported. Accordingly, this study performed experiments to evaluate the shear behavior of reinforced concrete (RC) beams with Fe-based SMA stirrups. Ten specimens were prepared for the experiments. The activation of the Fe-SMA stirrup, stirrup spacing, and shear span-to-depth ratio were considered as variables. The Fe-SMA stirrups were activated via electrical resistance heating. Activating the Fe-SMA stirrups applied compressive forces to the specimen, reduced the occurrence of diagonal shear cracks, and improved shear stiffness. However, it did not significantly affect the shear strength. The shear contribution of the Fe-SMA stirrup increased with an increase in the shear span-to-depth ratio and amount of shear reinforcement. In addition, the simulation results using the modified compression field theory (MCFT)-based section analysis model were consistent with the experiment results. Therefore, the model can predict the shear behavior of RC beams with Fe-SMA stirrups.

Failure analysis and structural reliability of unreinforced masonry veneer walls: Influence of wall tie corrosion

Corrosion appears to be a very common problem in historical and aged structures with steel ties and anchorages. A potential rapid deterioration of the wall tie due to the corrosion leading to a premature structural failure poses a serious threat to the built heritage infrastructures’ safety. This paper describes an overview of the probabilistic failure analysis of the unreinforced masonry (URM) veneer wall system with flexible backup under uniformly distributed out-of-plane loadings. Moreover, a framework is proposed to consider the wall tie corrosion in the stochastic finite element analysis (FEA) while estimating the structural reliability. A probabilistic experimental study where 18 full-scale URM veneer wall systems with theoretically identical geometries and properties were tested under inward and outward lateral loading. Wall failure statistics along with the probabilistic characterisation of veneer wall constituent materials including mortar, wall tie and timber were accomplished. A stochastic computational model was then developed which combines the FEA and Monte Carlo simulation to evaluate the failure progression and system peak load (veneer capacity) while considering the spatial variability of veneer wall material properties. Two scenarios, with and without wall tie corrosion, are considered, and the probabilistic characterisation of the veneer capacities for these scenarios under inward and outward out-of-plane loading is also reported. The model error statistics were combined with the probabilistic load models to determine the reliability index corresponding to the Australian Standard for Masonry Structures AS 3700. Annual reliabilities are compared to target reliabilities recommended by ISO 2394. Capacity reduction factor and design minimum tie strength consideration for corroded wall tie is also discussed.

New spectrally selective coatings for CSP linear receivers operating in air at high temperature

AbstractAn attractive candidate to reduce dependence on fossil fuels and replace them by renewable sources is represented by concentrated solar power (CSP) technology, whose wide deployment is still hindered by its high investment costs. In CSP linear collector plants, a key component with high technological content may be identified in receiver tubes, that are traversed by heat transfer fluid and located on focal line on which solar radiation is concentrated by mirrors. The proposed work aims at developing spectrally selective coatings for receiver tubes able to overcome state‐of‐the‐art technological limitation in terms of both vacuum encapsulation and maximum operative temperature, currently limited at 550°C for molten salts CSP plants. To this aim, a multilayer structure was designed and developed for coating a receiver tube to be employed in open‐air environment at temperature of 600°C. The multilayer coating is based on tungsten chromium titanium infrared reflector and includes a solar absorber layer developed with two alternative methods of reactive sputtering and thermal oxidation respectively, finally covered by antireflective and barrier bi‐layer of aluminum oxide and silica. Thermal stability was demonstrated of the new developed coatings, since only small variations were measured of the optical parameters after more than 2000 h of aging in open air conditions at temperature of 600°C (on average less than 5%), with final measured solar absorptance αs of 73% and 87% and thermal emissivity εth at 600°C of 18% and 27% for aged multilayer structures including the absorber layer obtained through thermal oxidation and sputtering process, respectively. These results pave the way for further improvement in terms of both optical performance and operative temperature increase, allowing to enhance efficiency and lower costs, thus contributing to ease to deployment of CSP technology.

Ultimate Shear Strength of Pitted Plates with Crack Using Finite Element Method

_ Ultimate strength of thin steel plates was studied under shear loading when pitting corrosion and cracking occur simultaneously. Nonlinear finite element method was used and the effects of different geometrical parameters, such as crack position, crack length, pit depth, pit diameter, number of the pits, and the inclination angle of the crack, were investigated. It was found that the degree of the pitting (DOP) significantly reduces the ultimate shear strength of the pitted plates when the corrosion is low. For high amount of corrosion, the reduction of the ultimate shear strength remains the same regardless of the amount of the DOP. In plates with short cracks, the crack length has no influence on the reduction of the ultimate shear strength. Also, it was found that the position of the crack is more effective than the length of the crack on the reduction of the ultimate shear strength of the cracked plates. In the cracked-pitted plates, there was no interaction between crack and pit for extremes value of DOP. For low value of DOP, the ultimate shear strength of the cracked-pitted plate was the same as the cracked plate, and for large value of DOP, it is the same as pitted plate. Introduction According to a study performed between 2002 and 2008 by American Bureau of Shipping (ABS) (“Review of Current Practices of Fracture” 2012), majority of reported fractures of the ships were structural failures, such as weld defect, buckling, fracture, and cracking. Cracks and corrosion are two more common defects, which are the main reasons of the failure of the aged steel structures. Plates and stiffened plates are the main structural elements in many structures, including airplanes, bridges, offshore structures, and ships. Ultimate strength evaluation of these structural elements is crucial for rational design of structures, such as Load Resistance Factor Design (LRFD) methods in civil engineering and Ultimate Strength (UTS) evaluation in ship structure. Many studies are carried out to evaluate ultimate strength of intact and damaged plates/ stiffened plates under in-plane compressive stress. Ranji (2012) studied ultimate strength of plate with general corrosion under in-plane compression. He proposed a spectrum for random generation of corroded surface and ultimate strength of corroded plate was evaluated using computer code ANSYS. Ranji and Zarookian (2015) analyzed ultimate strength of cracked stiffened plates with cracks having different stiffeners numerically.

Guided Wave Tomography of Surface Defects Based on the Method of Moments

AbstractThe detection and evaluation of corrosion, cracks, flaws, and other imperfections in aged structures are critical for enhancing safety and evaluating residual service life in structural health monitoring (SHM) and nondestructive testing (NDT). A guided wave tomography based on the method of moments (MOM) for exact detection of the surface defects in plates, including their profile, size, and position is proposed in this paper. The mathematical relationship between the plate thickness and the objective function is derived theoretically for the A0 mode. Based on the obtained relationship, a plate thickness imaging technique is proposed. The efficiency of the proposed technique is confirmed by the results of numerical simulation and experimental data. Center and off‐center surface defects are considered. 64 probes are evenly distributed in a circle outside the defect to capture omnidirectional wave signals. Both numerical and experimental results demonstrate that the guided wave tomography proposed can effectively reconstruct the spatial plate thickness distribution, enabling the precise identification of the defect's shape, depth, and position. The qualitative analysis and quantitative data provide effective guidance for NDT or SHM technologies in engineering.

Precision of Structures Used to Estimate Age and Growth of Apache Trout from Arizona

Abstract Obtaining reliable information on the age structure of fish populations is important for making conservation and management decisions. We sought to evaluate precision and reader confidence in age estimates from scales (two body locations), sectioned fin rays (pectoral, pelvic, anal), and sectioned sagittal otoliths from Apache Trout Oncorhynchus apache (n = 78 fish) sampled from the East Fork White River, Arizona, in 2017. Two experienced readers without prior knowledge of fish length aged structures independently. Each reader provided a confidence rating of 0 (no confidence) to 3 (completely confident) as a measure of readability. Both readers were unable to estimate age from scales collected from the area just posterior to the insertion of the pectoral fin. We used scales removed from an area just dorsal to the lateral line and posterior to the dorsal fin in all analyses. Percentage of exact agreement between readers was highest for scales and otoliths (&amp;gt;72.0%) and lowest for fin rays (31.8–58.1%). Average confidence rating was highest for sectioned otoliths (mean ± SE, 2.1 ± 0.07), and lowest for anal fin rays (0.3 ± 0.06) and scales (0.7 ± 0.05). We compared consensus ages from otoliths to the other structures. Percentage of exact agreement with otolith age was low and varied from 21.6 to 35.7% among structures. Similarly, percentage of agreement within 1 y was also low among structures (58.0–70.2%). Scales consistently underestimated age of age-4 and older fish (based on otolith age), whereas fin rays tended to overestimate age of younger fish and underestimate age of older Apache Trout. Although sectioned otoliths require lethal sampling, they produced the most precise age estimates for Apache Trout with the highest reader confidence. Dorsal scales may be a suitable nonlethal alternative to otoliths if ages for only young fish (age 3 and younger) meet study objectives.

Residual Mechanical Properties of Corroded Steel Bars after High-Temperature Exposure

Accidental fires in aged concrete structures can lead to combined damage from corrosion and fire. In this study, we aimed to explore the effects of corrosion and high temperature on the residual mechanical properties of hot-rolled plain and ribbed bars. The results indicated that the corroded steel bars still exhibited ductile failure after high-temperature exposure. Moreover, the combined action of high temperature and corrosion has little effect on the elastic modulus. The residual bearing capacity of the hot-rolled steel bar became smaller under the condition of temperatures above 600°C. When the temperatures experienced by the plain and ribbed steel bars were less than 600°C and 500°C, respectively, the high temperature accelerated the decrease in the nominal yield and ultimate strength. However, the yield and ultimate strengths based on the minimum cross-sectional area remained unchanged with an increase in the cross-sectional loss ratio. Similar to that at room temperature, the ultimate strain of steel bars subjected to high-temperature exposure decreased exponentially with an increase in the cross-sectional loss ratio. The new findings of this study can provide a theoretical basis for the safety assessment of aged reinforced concrete structures after exposure to fire.

Laboratory investigation on cement-treated recycled concrete aggregate bases for flexible pavements

India's economy is progressing fast, and many infrastructure development programs are going on. Especially the road network expansion is going on many folds. As a result, natural coarse aggregates are getting depleted, which has an impact on environmental sustainability. Utilizing the resources from the many aged and demolished structures will be cost-effective and solve the disposal problem of these wastes. India's government insists on using marginal material, demolished waste, or recycled aggregates as alternative materials for road construction. New codes developed by IRC and MoRTH recommend Cement Treated Bases (CTB) and Cement Treated Sub-Bases for pavement lower layers. In light of this, the present study attempts to utilize Recycled Concrete Aggregates (RCA) obtained from construction and demolition (C&D) waste in the CTB. The efficiency of RCA was checked at various replacement levels ranging from 0% to 100% with cement stabilization of 3%, 5%, and 7%. The strength properties like Unconfined Compressive Strength (UCS), Flexural Strength and durability were evaluated. The microstructural characteristics and elemental analysis of the cement treated recycled concrete aggregate mixtures were examined. The research yielded the highest potential RCA of up to 50% with a cement content of 5%, meeting the Indian Road Congress (IRC) criteria for CTB.

Influence of Wetting Conditions and Concrete Strength of Both Substrate and Repair Material on the Bond Capacity of Repaired Joints

Ultra-high performance concrete (UHPC) is an appropriate material to repair and rehabilitate aged structures due to its excellent properties, such as high compressive strength and durability. Several studies have demonstrated the effectiveness of applying UHPC in old buildings as a rehabilitation or repair material, but the bond between concretes needs more investigation. In this sense, the bond between normal-strength concrete (NSC) and UHPC is currently being studied. Three main parameters are responsible for ensuring a good bond: the surface treatment of the substrate (roughness), the wetting conditions, and the mechanical strength of the substrate. Thus, the present study investigated the bond between concretes experimentally. The concrete of the substrate was carried out in three grades: C25, C45, and C60. The repair concretes were C25, C45, C60, and UHPC. The following parameters were evaluated: wetting conditions, air surface dry (ASD), saturated surface dry (SSD), substrate strength, and repair concrete strength. All models received surface treatment by wire brushing. Slant shear and splitting tensile tests were performed to evaluate the mechanical behavior and the failure modes of the bond between concretes. The bond strength was classified and compared to existing predicting models. The results showed that most expressive strength gains occurred in SSD models with lower strength substrates and UHPC. Furthermore, the influence of surface wetting conditions becomes smaller as the strength of the substrate is reduced.

Performance prognosis of FRCM-to-concrete bond strength using ANFIS-based fuzzy algorithm

Nowadays, strengthening of reinforced concrete structures with a new class of sustainable materials is the possible solution to retrofit the aged deteriorated structures. It is difficult to predict the capacity of the strengthened (FRP/FRCM) reinforced concrete elements without considering the bond strength. Therefore, the concrete substrate to Fibre-Reinforced Cementitious Matrix (FRCM) bond is a crucial parameter in the strengthening procedures. As it is known, bond strength is dependent on various parameters, which increases the complexity of the FRCM-to-concrete bond. Analytical models cannot provide a high degree of accuracy, as their predictions are only valid for specific datasets. Machine learning algorithms are the best-suited solution to deal with bond strength like complex problems. In this study, curve-fitting, Gaussian Process Regression (GPR) and Adaptive Neuro-Fuzzy Inference System (ANFIS) models have been applied to 336 aggregated datasets. Nine performance matrices have been opted to compare the performance of the developed models. Feature importance analysis has also been used to check the rationality of the model. The parametric analysis has also been done using the 3D-surface plot of the ANFIS model. The R-values of ANFIS, GPR, and curve-fitting models are 0.9895, 0.9882, and 0.9145, respectively. The mean absolute error, root mean square error and Nash-Sutcliffe index of the ANFIS model are 0.9168 kN, 1.4326 kN, and 0.9791, respectively. The mean absolute percentage error of the ANFIS model is 11.19%, which is 8.72% and 76.78% lower than GPR and curve-fitting model, respectively. The error range of the curve-fitting, GPR and ANFIS models are −17.06 kN to 18.04 kN, −4.39 kN to 6.07 kN, and −4.23 kN to 5.19 kN, respectively. Overfitting analysis of the proposed models has been done, and the predicted results show that the curve-fitting model and GPR models are inferior and the ANFIS model is superior based on the selected performance matrices. The overfitting value of ANFIS model is 67.89% and 8.31% lower than curve-fitting and GPR model, respectively. The sensitivity analysis found that the number of layers, the width of the concrete block, and the compressive strength of the concrete had the highest effect on the FRCM-to-concrete bond strength. The findings of the study have the potential to decrease costs and save time by employing an accurate prediction approach instead of expensive and time-consuming testing. The developed model can be easily used by industry experts and FRCM applicators to estimate the bonding strength of FRCM-to-concrete substrate for sustainable designs.

Application of ECC as a Repair/Retrofit and Pavement/Bridge Deck Material for Sustainable Structures: A Review.

Concrete structures cannot efficiently perform their functions over time due to chemical and physical external effects. Thus, enhancing the relationship between repair and aged structures, and also improving the durability properties of concrete is crucial in terms of sustainability. However, high costs, negative environmental effects, and incompatibility problems occur in repair/retrofit applications. Furthermore, three-quarters of the failures in the repaired/retrofitted structures are caused by a lack of repair durability. The need for repair in pavement/bridge decks is also frequently encountered, and early-age performance problems with repair materials cause pavement/bridge decks to be unavailable for certain periods of time. Engineered Cementitious Composite (ECC) can be effectively used as repair/retrofit and pavement/bridge deck material. It also has a minimal need for repair/retrofit thanks to its high durability properties. This article presents state-of-the-art research regarding the application of ECC as a repair/retrofit and pavement/bridge deck material. Studies in the literature show that the repair/retrofit properties of ECC outperform conventional concrete and steel fiber-reinforced concrete. ECC can be a solution to high early strength and drying shrinkage problems frequently encountered in the use of repair materials. It could also be used for different repair applications such as cast, sprayed, and trenchless rehabilitation. Moreover, ECC might fulfill specific requirements for pavement, pavement overlay, tunnel pavement, airfield pavement, and bridge deck. These superior performances are attributed to ECC's kink-crack trapping mechanism, uniquely large inelastic strain capacity, strain hardening, high tensile strain capacity, and multiple microcracking and ductile behaviors, especially bonding behavior and self-healing.