Department of Civil Engineering
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Item Axial load prediction of circular hybrid double-skin tubular columns using interpretable gradient boosting machine learning models(Springer, 2026-01) Singh, Shamsher Bahadur; Barai, Sudhir KumarThis study assesses the predictive performance of three gradient-boosting Machine Learning (ML) models, Gradient Boosting Machine (GBM), eXtreme Gradient Boosting (XGBoost), and Light Gradient Boosting Machine (LightGBM), in axial load prediction of circular FRP-concrete-steel double-skin tubular columns (hybrid DSTCs). Data from 275 specimens were compiled from 22 publications in the literature to train and test ML models. Input variables consist of the height of column (), outer diameter of the FRP tube (), outer thickness of the FRP tube (), diameter of the inner steel tube (), thickness of the inner steel tube (), tensile strength of the outer FRP tube (), yield strength of the inner steel tube (), and compressive strength of concrete (), with the ultimate axial load () serving as the output variable. Performance of all three gradient ML models was evaluated using statistical measures including coefficient of determination (R2), root mean square error (RMSE), mean absolute percentage error (MAPE), and mean absolute error (MAE) for training and testing datasets. Results indicate that the XGBoost model performed better than the other two gradient Models (GBM and LightGBM) with R2 values of 0.97 on the training data and 0.95 on the testing data. Further analysis of the XGBoost model assessed the relative importance of input features on the output feature.Item A simplified mix proportioning method for structural grade lightweight concrete using sintered flyash lightweight aggregate(Springer, 2026-01) Singh, Shamsher Bahadur; Barai, Sudhir KumarStructural concrete of a designed strength can be produced for specific requirements by using the accepted methods of mix design but the present Indian standards on mix design does not takes into account the procedure for mix design of sintered flyash lightweight coarse aggregate based concrete. The sintered flyash lightweight aggregate mainly produced from ash generated from coal based thermal power plants has higher water absorption and lower specific gravity. The mix proportioning of sintered flyash lightweight coarse aggregate based concrete is reported to be cumbersome and less accurate than normal weight concrete as the water absorption characteristics of these aggregates is a main concern. The current study has been done to develop a simplified mix design procedure for production of structural grade lightweight concrete using commercially available sintered flyash lightweight aggregate. The study also highlights the procedure for corrections need to be done with respect to higher water absorption characteristics of sintered flyash lightweight aggregate taking into account effect of cement paste during concrete mix proportioning. Based on the developed mix design method, a trend of 28-day cube compressive strength versus w/c for sintered flyash lightweight aggregate based concrete has been plotted for wide range of w/c from 0.3 to 0.7 and compared with curve given in IS: 10262-2019 for normal weight concrete.Item Empirical model for determining compressive strength using post-installed pull-out test for structural lightweight concrete made with sintered flyash lightweight aggregate(Wiley, 2025-06) Singh, Shamsher Bahadur; Barai, Sudhir KumarIn recent years, structural lightweight concrete has gained momentum in its use due to its superior properties in terms of dead load reduction, better thermal comfort, improved fire resistance, etc. The use of lightweight aggregates manufactured from industrial bi-products such as flyash presents an alternative to ever-depleting natural aggregates and has been the solution to environmental challenges and a circular economy. With the increase in the use of sintered flyash lightweight aggregate-based concrete (LC-SFA), there is a need to evaluate the applicability of existing empirical equations and models available to predict the on-site strength of concrete using the pull-out method. The pull-out technique for on-site strength estimation has been well researched for normal concrete (NC), but very limited studies have been reported for structural lightweight concrete. This study aimed to develop a model for the determination of on-site compressive strength from 20 to 50 MPa for lightweight concrete (LC) with sintered flyash lightweight aggregate with a high degree of predictability and accuracy using the non-destructive pull-out test, and compare the results with normal weight concrete. The pull-out method adopted in the study has demonstrated that the in-place compressive strength of concrete can be predicted with high accuracy and better repeatability of LC-SFA. The percentage variation in compressive strength predicted by different models varies from −2% to 80%. The proposed model for normal concrete and the model developed by Jensen and ACI for normal concrete gave values somewhat near to the experimental results of LC, however, the variation was more than 15% in the case of ACI, and in the case of Jensen, the values were on the lower side. The study revealed that existing empirical equations available for normal weight concrete to predict the compressive strength on the basis of pull-out force will not be applicable to lightweight concrete, and proposed a model based on a study conducted gives high accuracy and repeatability.Item Empirical model for static and dynamic modulus of elasticity for sintered flyash lightweight aggregate based concrete(Springer, 2025-09) Singh, Shamsher Bahadur; Barai, Sudhir KumarThe present study developed a relationship between the (a) compressive strength and static Modulus of Elasticity (MOE), (b) compressive strength and dynamic MOE, and (c) the static MOE and dynamic MOE for sintered fly ash aggregates based concrete. This is the first detailed study to propose MOE models for concrete using sintered fly ash aggregates (SFA) validated across five mix designs and 120 specimens. The existing codes overestimate the MOE for SFA based lightweight concrete. To determine static MOE, the cylindrical specimens have been placed under uniaxial compression in strain-controlled mode, and a compressometer has been used to measure the MOE. The ultrasonic pulse velocity and dry density of concrete with different strength ranges were measured to evaluate the dynamic MOE of concrete produced using SFA. The MOE of concrete produced using SFA as coarse aggregate is around 30–35% lower than that of normal-weight concrete. The static modulus of elasticity of lightweight concrete with SFA ranged between 16 GPa and 27 GPa, whereas the dynamic modulus of elasticity of lightweight concrete with SFA ranged between 19 GPa and 28 GPa for a compressive strength range of 20–55 MPa. Based on the experimental results, an empirical equation has been developed for estimating static MOE and dynamic MOE, and the relationship between static and dynamic MOE. The developed equations have been compared with those in the codes and literature. The developed models enhance accuracy in structural analysis and design through reliable estimation of MOE, and propose an alternative, quick, and easy method to estimate dynamic MOE for SFA-based lightweight concrete using the ultrasonic pulse velocity method.Item Probabilistic life cycle assessment of ash-based sintered lightweight aggregates manufactured with producer gas and coal-operated thermal power(Springer, 2025-09) Singh, Shamsher Bahadur; Barai, Sudhir KumarThe infrastructure growth in the world is expected to result in huge requirement of 12.5 billion tonnes of coarse aggregates in 2050. The utilization of artificial aggregates can pave a feasible pathway for tackling the issue of scarcity of natural aggregates. Life cycle assessment (LCA) is an environment management tool, which has been used for the large-scale acceptability of sintered flyash lightweight aggregates (SFLA) in the construction fraternity. The low quality of data inputs for LCA study induces bias and increase in uncertainty of evaluated impacts. In the current study, a probabilistic LCA framework has been developed for assessing the environmental impacts from the manufacturing of SFLA. The uncertainty distribution range in each of the input variables was identified and introduced in the model with the help of random numbers. In this study, uncertainty analysis is also carried out using Monte Carlo Simulation for the comparative analysis of baseline scheme with three alternative schemes of SFLA manufacturing process. Finally, the sensitivity analysis (SA) was also undertaken for studying the robustness of LCA model outputs. The global warming potential (GWP) for the baseline scenario is 198.6 kg CO2 eq. per t of SFLA. Three alternative schemes were proposed for which comparative impact assessment is carried out, which highlighted the GWP impacts reduces to 166.7 kg CO2 eq. per t of SFLA (16% lower), 142.6 kg CO2 eq. per t of SFLA (28% lower) and 123.4 kg CO2 eq. per t of SFLA (38% lower) for first, second and third alternative schemes respectively as compared to the baseline scheme. Sintering process is contributing highest to impact mainly due to emissions from combustion of coal present in raw mix, CO2 emissions from electricity consumed during the process and CO2 generated from producer gas production which is used for thermal energy in sintering process. The results of probabilistic LCA study show that there are significant variations in the coefficient of variation across the various unit processes and across the four impact categories.Item Machine learning-based prediction of axial load and strain capacities for circular FRP-concrete-steel double-skin tubular columns(Taylor & Francis, 2025-12) Singh, Shamsher Bahadur; Barai, Sudhir KumarFiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (hybrid DSTCs) are innovative composite columns offering high strength, ductility, corrosion resistance, and lightweight due to hollow cross-section. Despite extensive experimental, numerical, and analytical studies, accurately predicting the behavior using traditional methods remains challenging. Experimental and numerical methods are costly and time-consuming, while analytical approaches are conservative and may not effectively capture complex and nonlinear relationships. This study compares five machine learning (ML) models with two existing empirical equations for predicting the axial load and axial strain of circular hybrid DSTCs. An extensive dataset of 249 specimens from the literature was used to train and test ML models. Five ML models, namely, multiple linear regression (MLR), decision tree (DT), random forest (RF), K-nearest neighbors (KNNs), and extreme gradient boosting (XGBoost), were trained using eight input parameters. Results indicate that the XGBoost model achieved the highest accuracy in predicting both axial load and strain capacities, with R2 values of 0.87 and 0.96, respectively. Among the empirical equations, Louk Fanggi and Ozbakkaloglu’s equation performed better than traditional ML models such as MLR and DT for axial load prediction, achieving an R2 value of 0.785, compared to 0.72 for MLR and 0.74 for DT. Feature importance analysis further identified the significant influence of geometric parameters on axial load prediction and material properties on axial strain prediction. Additionally, a user-friendly web application is developed, allowing users to easily predict the axial load and strain of circular hybrid DSTCs, demonstrating ML’s efficiency as a data-driven alternative to empirical approaches.Item Experimental investigation for the determination of stress-strain relationship for sintered flyash lightweight aggregate concrete(Elsevier, 2025-08) Singh, Shamsher Bahadur; Barai, Sudhir KumarLightweight concrete offers better performance as structural concrete owing to its reduced dead load, better durability, and thermal insulating properties. However, it displays a reduction in certain mechanical properties related to its modulus of elasticity and ductility. The present experimental work investigates the stress-strain behaviour of concrete produced with sintered flyash lightweight as coarse aggregate (SFA). The specimens for determining stress-strain curves were tested under a closed-loop strain-controlled compression machine with 3000 kN capacity. To record the stress-strain behavior, extensometers were fixed in the central portion of the cylindrical specimen along its height to obtain a complete stress-strain curve. The loading rate was determined through experimental trials to obtain the full stress-strain curve at a loading rate of 0.4 μm/s. The stress-strain study has been conducted on a strength range between 15 and 45 MPa for analyzing the stress-strain behaviour of SFA-based concrete. The complete stress-strain behaviour during the ascending portion mainly consists of concave as well as convex shapes, while the descending branch shows a non-uniform shape and is relatively short. Based on the analysis of stress-strain curves tested under uniaxial compression, a constitutive relationship has been developed for the determination of strain at peak stress and ultimate strain for SFA concrete, and compared with existing empirical equations in the literature and codal provisions. From the study of complete stress-strain behaviour, ascending and descending branch constitutive equations of lightweight concrete have been developed and compared with experimental data, which mirrors the stress-strain behaviour under uniaxial compression. The results indicate that the ultimate strain to peak strain (εu/εo) decreases with the increase in compressive strength for concrete with SFA. The decrease in the εu/εo with an increase in compressive strength indicates that with an increase in compressive strength, concrete becomes brittle and the difference between εo and εu decreases. The ratio of residual stress to peak stress (σri/ σo) varies between 0.25 and 0.15, and no specific clear-cut trend has been observed with an increase in the compressive strength of concreteItem State-of-the-art review on axial behavior of FRP-concrete-steel double-skin tubular columns(Associated cement companies ltd., 2025-02) Singh, Shamsher Bahadur; Barai, Sudhir KumarOver the last twenty years, there has been considerable focus on the use of fibre-reinforced polymer (FRP) composites as confinement substances. The hybrid double-skin tubular column (DSTC) represents an innovative construction approach, comprising an external fibre-reinforced polymer (FRP) tube, an inner steel tube, and a concrete infill. These columns are primarily designed to offer corrosion and seismic resistance, DSTCs have gained popularity in bridges and offshore structures applications. This paper aims to provide an unbiased evaluation of the experimental research efficiency of hybrid FRPconcrete- steel double-skin tubular columns subjected to axial compression while exploring various critical parameters, as well as numerical and analytical studies. The examined parameters include the buckling behavior of the inner steel tube, the diameter of the inner steel tube, FRP tube thickness, the orientation of fibres, failure modes, axial load-strain behavior, FRP hoop rupture strain, concrete strength and concrete type, the interaction between steel and FRP tubes, filling the inner steel tube, stiffened DSTCs, and cross-sectional form. The review findings emphasize the importance of future research in areas such as non-circular column members, the use of natural fibres for the outer FRP tube, and numerical and analytical studies. These insights are valuable for researchers, practitioners, and decision-makers involved in designing, constructing, and retrofitting efficient and resilient structures as hybrid DSTCsItem Numerical parametric study on the flexural response and failure characteristics of GFRP-concrete composite beams with GFRP dowel shear connectors(Springer, 2025-04) Singh, Shamsher BahadurThis paper presents the findings of a numerical study conducted to examine the influence of different structural parameters on the response of a complete steel-free, glass fiber reinforced polymer (GFRP) dowel connector based, GFRP-concrete composite beam. The three-dimensional nonlinear analysis was carried out using the commercial software package Abaqus/CAE, and the damage evolution in concrete was defined using the concrete damaged plasticity (CDP) material model. The methodology was validated by comparing the results against those of an experimental study. The results showed that the composite beam ultimately fails either due to the shearing of the web or the rupture of the connected GFRP flange around the connection points; and its load-carrying capacity and stiffness have a proportional relationship with the compressive strength of concrete, the longitudinal elastic modulus of the profile, the elastic modulus of the connectors, the width of the concrete slab, the depth of the composite section, and the wall thickness of the profile; and an inverse relationship with the span length and the angle of inclination of connectors. The vertical deformations are significantly affected by the shear modulus of the GFRP profile; a relatively better response is obtained with a closed section profile; an optimum connector diameter and longitudinal spacing value exists at which the load carrying capacity is maximum; and the provision of web cutouts deteriorates the overall structural behavior. The critical findings of the study will assist the structural designers/researchers in developing an efficient and optimum design configuration for such structures in the near future.Item Pollutant removal from paint, mortar, and reinforced composite and evaluating the engineering properties by incorporate the photocatalyst: BaTio3(Wiley, 2025-07) Singh, Shamsher Bahadur; Srivastava, AnshumanThe present work explores to study the pollutant removal properties of mortar, concrete, and paint by incorporating the BaTiO3 as photocatalysts with different dosages (0.5%, 1%, and 2%) replaced by weight of cement and 20 g in white paint of 40 mL. To investigate the pollutant removal property of specimens prepared with Ordinary Portland Cement (OPC) and white cement (WC) and white paint on ordinary wall, Rhodamine B dye is used as a pollutant. The pollutant removal property was investigated for 4 days in laboratory experiment and 4 days in the field experiment. It was observed that the specimen having dosage of 2% photocatalyst have the best result in pollutant removal than the other specimen in laboratory experiment. The catalyst shows pollutant removal ability in white paint even in the presence of sunlight effectively and maintains the color’s grace of the paint. The compressive strength increased with the addition of a photocatalyst, and other engineering properties of the specimens were the same even at different dosages of the photocatalyst. The photocatalyst BaTiO3 remove the pollutant from paint, mortar, and reinforced composite without affecting the all the engineering properties.