•ML algorithms were employed to predict punching shear strength of FRP-RC slabs.•The ML-based models exhibited more accurate and unbiased predictions.•Compare XGBoost-based model with other ML-based ...models and existing design equations.•Feature importance and sensitive analysis was used to explain the model predictions.
Recently, the use of fiber-reinforced polymer (FRP) bars replacing steel reinforcement has been widely applied to overcome the corrosion issue, particularly concrete slab-column connections using FRP bars as flexural reinforcement (FRP-RC slabs). However, experimental studies showed that the use of FRP differentiates the punching shear behavior from steel-RC slabs. Various methods have been proposed to predict the punching shear strength of FRP-RC slabs, but existing design equations need improvement because their accuracy is low with wide scatteredness. Thus, this study aims at pioneering the application of machine learning (ML) algorithms for the prediction of the punching shear strength of FRP-C slabs without shear reinforcement. For this purpose, an experimental database with 104 specimens was compiled, with the input variables of the shear span-to-effective depth ratio, column perimeter-to-effective depth ratio, effective slab depth, concrete compressive strength, FRP reinforcement ratio, and ultimate tensile strength and elastic modulus of FRP. Three ML algorithms, including support vector regression (SVR), random forest (RF), and extreme gradient boosting (XGBoost), were evaluated for the application. To develop the ML-based models, a grid search method with a 5-fold cross-validation approach was used in the training process to determine the optimal hyperparameters. The performance of the ML-based models was estimated using various statistical estimators and compared with the current design codes and existing models. The comparisons showed that all three ML-based models could accurately predict the punching shear strength of the FRP-RC slabs without any significant and evident bias with the input variables. The XGBoost-based model displayed the best prediction with the coefficient of determination (R2) of 0.962, the root mean square error (RMSE) of 0.061 MN, mean absolute error (MAE) of 0.035 MN, and mean absolute percent error (MAPE) of 8.931% for testing dataset. The correlation coefficient, feature score, and sensitive analysis for the input variables indicated that the effective slab depth has the most substantial influence on the prediction performance. The prediction by the XGBoost-based model was more accurate and robust than that by the SVR- and RF-based models, current design codes, and existing models. These analysis results proved that the XGboost-based model can be used in the design and evaluation of FRP-RC slabs reliably and precisely.
Despite the intensive efforts dedicated in the last decades to better understanding punching shear failures, there is still no consensus on the mechanics governing this phenomenon and on how to ...implement it within a physical approach. In this paper, an analysis of recent detailed measurements on the kinematics and crack development associated with punching failures is presented. This allows classifying the observed cracks by their nature and to address their interaction and development on the eventual punching failure surface. On this basis, a complete mechanical model is formulated consistently with the principles of the critical shear crack theory (CSCT). This model generalizes previous approaches based on the CSCT by accounting for the various crack types and failure modes as well as for their associated kinematics. The generality of the model is verified by extensive comparisons to test data, showing accurate and consistent agreement. Its results are eventually used to investigate the role of the various potential shear‐transfer actions as well as the pertinence of the assumptions adopted to simplify the CSCT by describing its failure criterion with analytical expressions.
•The relationship between the relative clearance and the fractured morphologies of the punched-out HEA was established.•The fractured surfaces of punched-out disc are composed generally of ...deformation zone, fracture zone, and burr zone.•The relative clearance affects the distribution of stress states of HEA plate during shear punching process.
In this paper, the deformation and fracture behaviors of Co20Cr20Fe20Ni20Mn15Cu5 high entropy alloy plates in the shear punching tests were studied. The fractured surfaces of the punched-out high entropy alloy discs consist of three parts, i.e., the deformation zone, the fracture zone, and the burr zone. As the ratio of clearance to the plate thickness, i.e., the relative clearance, gradually increases, the percentages of both deformation zone height and burr zone height increase. This phenomenon was attributed to the changes of stress states during shear punching process. Meanwhile, a larger relative clearance favors more plastic deformation, generating numerous slip bands and some elongated dimples on the fractured surface.
•Geopolmer concrete reduces carbon dioxide emissions.•Geopymer concrete is an eco-friendly concrete.•Industrial waste material is used during the production of geopolymer concrete.•During the ...production of geopolymer concrete, industrial waste materials are used. Thus, it helps to solve the storage problem of waste materials and causes less damage to the environment.•Steel fiber and nano silica improves the punching shear strength of slabs.
This research was conducted by performing center point load tests on the two way flat slab samples to investigate the combined effects of steel fiber (SF) and Nano-silica (NS) on the punching shear and deflection capacities of ten slag-based Geopolymer Concrete (GC). This study consists of two parts; in the first part, the effects of only SFs were investigated, while in the second part the combined effects of NS and SFs on the properties of GC were examined. During the study, two types of hook-end SFs (0.5% and 1%) and only 2% NS were used. The tested slabs showed that the energy absorption capacity/toughness of GC slabs was positively affected by the inclusion of NS and SFs. Also, it was favorably influenced by SFs content and aspect ratio. Furthermore, these slabs were categorized. While, NS and SFs enhanced the punching shear strength of the slabs, the combined influence of NS and SFs exhibited better the punching shear capacity compared to individual utilization. It is clear from the experimental studies that the slab with the combination of NS and SF2 outperformed all of them and showed 131.08% higher strength bearing capacity than the slab without SFs and NS.
This paper investigates, experimentally and analytically, the ultimate strength behavior of steel–concrete–steel (SCS) sandwich plates under concentrated loads. The proposed SCS sandwich plate ...consists of two external steel plates and a sandwiched concrete core. 17 quasi-static were carried out to evaluate their structural performances under concentrated loads. 20 test data in the literature were used to analyze the failure mode and load-transferring mechanisms of the SCS sandwich plate under concentrated loads. The influences of sandwich plates with different plate geometry, diameter of connectors and their spacing, and concrete core strengths were analyzed and discussed. Theoretical models were developed to predict the resistances of the connectors, flexural resistance of the SCS sandwich plate, punching resistances of the concrete core and punching resistance of the top steel plate. Design methods were then developed to predict the maximum resistance of SCS sandwich plate subject to concentrated load based on the minimum the design resistance calculated for each individual components. The accuracy of the design methods were validated against the test results. Finally, the ultimate load resistance of the SCS sandwich plate was compared with the ice-contact pressure in ISO code to check its applicability for use as ice-resisting wall in the arctic region.
•ABAQUS can be used to study the impact of column rectangularity on punching shear.•Slab shear stresses concentrate near the corner and along short side of the column.•Impact of column rectangularity ...on punching not a function of column geometry only.•Impact also dependent on ratio of minimum column dimension to effective slab depth.•ABAQUS results indicate that current American design methods may be unconservative.
Design provisions for punching shear of reinforced concrete flat slabs supported on rectangular columns vary greatly and are typically based on empirical results. Due to the large cost and time required to conduct experimental tests the empirical database for slabs supported on rectangular columns is small. Properly calibrated, nonlinear finite element models (FEM) provide an efficient way to expand experimental databases, conduct parametric studies and verify design provisions. In this paper, the results from a parametric study of the impact of column rectangularity (aspect ratio) on the punching shear behaviour of interior slab-column connections without shear reinforcement under static concentric vertical loading are provided. The study was conducted using a three-dimensional nonlinear FEM based on the concrete damaged plasticity model available in ABAQUS. The FEM, summarized herein, was calibrated using seven experimental specimens of slabs supported on square and rectangular columns from literature. The parameters studied were the column aspect ratio, and the ratio of the minimum column dimension to the effective slab depth. These parameters were selected based on a review of literature and design provisions. The impact of column rectangularity on the predicted load-deflection response, slab crack patterns and shear stress distribution in the slab along the column perimeter are analyzed. The results for the 77 slab-column connections simulated in the parametric study demonstrate that the impact of column rectangularity is not dependent on the column aspect ratio alone, and becomes more severe as the ratio of the minimum column dimension to the effective slab depth increases.
•Push-out tests were conducted to investigate the bond behavior between the steel tube and the foundation concrete.•Punching tests were conducted to reveal the working mechanism of the embedded ...column base with shear studs.•A method was proposed to determine the punching shear resistance of the embedded column base for CFSTs.
In this paper, the punching shear behavior of the embedded column base for the concrete-filled steel tube is experimentally studied. Push-out tests were firstly conducted to obtain the bond strength between the steel tube and the foundation concrete. Punching tests were then performed on ten specimens to reveal the working mechanism of the embedded column base with shear studs. The test results indicated that shear studs changed the load path, enlarging the punching section of the foundation and improving the punching shear resistance of the column base. It was also found that the diameter of the shear studs and the distance between the shear studs could affect the punching shear resistance significantly. Finally, a method was proposed to determine the punching shear resistance of the embedded column base for the concrete-filled steel tube, by adding up the contributions from the different components of the system, including the bond force and shear resistance of studs above the punching section, and the resistance of foundation. The predicted results showed good agreement with the experimental results, with errors not greater than ± 15%.
•The eccentric load in the slab significantly reduces its punching shear.•The place of the opening in relation to the bending moment affects the punching shear.•The analyzed codes do not take into ...account the direction of the bending moment.•The punching force in accordance with Codes is notably lower than experimentally.
The aim of this study is to discuss the punching shear strength of flat RC slabs supported directly on columns. Special attention is paid to slabs which, in addition to axial load, are loaded with an unbalanced bending moment caused by the eccentricity of the force in relation to the vertical axis of the column with the presence of an opening along the face of the internal column. The slabs with the opening are made in such a way that no additional reinforcement is placed around the openings themselves. The reason for this is an attempt to simulate the subsequent formation of an opening in the slab for the purpose of passing various types of installations in the existing structure. The experimental research included tests on seven RC slabs without shear reinforcement with a loading up to the punching shear failure. By varying the position of the opening in relation to the eccentrically loaded column, as well as the shape and dimensions of the column, the degree of reduction in punching shear strength caused by the eccentricity of the force and the position of the opening in the slab was determined. The measured forces due to which the punching shear failure occurred were compared with the calculated ones obtained in accordance with the design codes prescribed by the leading world standards (EC2, ACI 318 and MC 2010) as well as with existing experimental research from the published literature.
•Load-resistant mechanisms of in-plane restrained and eccentrically loaded slab-column joints with drop panels were investigated.•Effects of eccentricity and punching shear failure sections on ...punching and post-punching performances were evaluated.•A high-fidelity 3D FEA model of the slab-column joints with drop panels was developed.•The punching cone angles of two different failure sections at the slab-column joints with drop panels were quantified.•A prediction method for post-punching strength calculation for different punching shear failure sections was proposed.
In concrete flat plate slab-column joints with drop panels, successive punching shear failures often occur at the slab-drop panel interface and along the column perimeter. When such joints are subjected to combined bending-shear actions under an eccentric load, their punching and post-punching shear failure behaviours are further complicated which can significantly impact the progressive collapse behaviour of the structural system. An experimental study was conducted on six laterally-restrained slab-column joint specimens with drop panels. Different levels of load eccentricities and different drop panel thicknesses were considered. Two punching shear failure sections were also identified. For a thick drop panel, the first punching failure took place at the slab-drop panel interface, followed by the second punching shear failure occurring along the column perimeter. For a thin drop panel, on the other hand, punching shear failure only occurred at the column perimeter. The damage patterns, the reinforcement strains and the joint strengths before and after punching failure at two different sections were analysed. Numerical simulation was conducted to investigate the effects of load eccentricity on the inclination of the punching cone. Numerical results showed that the punching cone angles at the slab-drop panel interface and at the column perimeter are, on average, 11.6° and 27.1°, respectively. In addition, larger eccentricity contributed to higher cross-sectional shear stresses on the eccentric loading side, leading to reduced punching shear strength and earlier damage. Furthermore, the experimental and numerical punching shear strengths were compared against the predictions of the Chinese, American and European design codes. Finally, a post-punching strength prediction method was proposed, and the predicted strengths deviated from the experimental results by −16% and 23%, for the thick and thin drop panels, respectively. In addition, the integrity reinforcement was also found to contribute at least 80% to the post-punching shear strength.
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