A visual technology to identify the punching points of a textile vamp to replace manual punching by machinery is proposed in this paper. This could solve several problems relating to the manual ...punching of textile vamp, such as high manual-punching strength, low efficiency, and poor punching accuracy. Unsharp mask guided filtering was adopted, to enhance the details of the textile-vamp punching points, considering the edge point position, gradient phase, and edge significance of the punching points, in building the template matching similarity measure function. A partial Hausdorff distance was proposed to sum and average values, to improve the degree of matching of punching point shape defects. A local search area of punching points to improve identification efficiency and punching evaluation criteria was established to evaluate the punching effects. The results showed that the matching similarity of the complete boundary was above 0.9. Positioning accuracy was 0.43 mm in the x-direction, 0.38 mm in the y-direction, and repeat positioning accuracy was 0.09 mm. The center average relative error was 5.03% and the relative error of the radius was 7.81%. Identification timeliness increased with the rotation angle, template size, and the number of punching points. When the rotation angle was between –180° and 180° and the number of punching points was 24, identification timeliness was 830 ms, which met productivity requirements. Textile-vamp punching grades A to D qualified, however, grades E and F were unqualified for punching.
•497 experimental data of reinforced concrete (R/C) interior slab–column connections were collected for the development of machine learning (ML) models.•Extreme gradient boosting (XGBoost) was ...employed to predict the punching shear resistance of R/C interior slabs without shear reinforcement.•The developed XGBoost model was compared with two other ML models, four design codes, and three empirical models.•The XGBoost model presented the best accuracy.•A graphical user interface was developed based on the XGBoost model for the estimation of punching shear strength.
This paper aims to present the application of extreme gradient boosting (XGBoost) to the prediction of the punching shear resistance of reinforced concrete (R/C) interior slabs without shear reinforcement. For the training and testing of the XGBoost model, which was developed using the XGBoost 1.1.1 package, 497 experimental data of interior slab–column connections were collected from the literature. The input variables were the column section dimension, slab effective depth, concrete compressive strength, steel yield strength, and reinforcement ratio at the top and bottom of the slab. The targeted output variable was the punching shear strength. First, the developed XGBoost model was compared with two other machine learning (ML) models that incorporate artificial neural network (ANN) and random forest (RF). All three ML models could reliably estimate the punching shear resistance of the considered type of R/C slabs, but the XGBoost model generally achieved the best prediction. Second, the performance of the developed XGBoost model was compared to various design codes and empirical models. The XGBoost model presented the most accurate prediction among them with the coefficient of determination (R2) for the testing dataset being equal to 0.9578. Third, the relative significance of input variables in the prediction of punching shear resistance was examined. The effective depth was shown to have the most significant role in the punching shear prediction. Finally, a graphical user interface based on the XGBoost model was created for preliminary estimation of the punching shear resistance of R/C interior slabs without shear reinforcement.
The paper deals with the results of a loading an isolated fragment of flat slab specimen with two openings located close to the column. Slab specimen was supported by an elongated column and was ...without shear reinforcement. The accuracy of the relevant design models for prediction punching resistance was tested with obtained test results. All design models provided punching capacity on the safe side. The best accuracy has been achieved by non-linear analysis that was carried out with Atena software.
Some reinforced concrete slabs are subjected simultaneously to concentrated loads and unidirectional in‐plane tensile forces. This the case of the top slab of a box girder bridge where hogging ...bending moments take place at the intermediate supports. Then, the in‐plane tensile forces may reduce the punching‐shear strength under concentrated loads. This paper describes an experimental campaign carried out to investigate the effect of unidirectional in‐plane tensile forces on the punching‐shear strength of RC slabs. A total of, five slabs (1,650 × 1,650 × 120 mm), subjected to different levels of in‐plane tensile forces were tested under a concentrated load up to failure. As observed, the punching‐shear strength diminishes almost linearly as the tensile force increases, up to a certain point associated to concrete cracking. From that point on, the reduction of punching strength is larger since the tensile force at the crack must be resisted by the reinforcement, which yields prematurely.
When designing flat slabs made of steel fiber-reinforced concrete (SFRC), it is very important to predict their punching shear capacity accurately. The use of machine learning seems to be a great way ...to improve the accuracy of empirical equations currently used in this field. Accordingly, this study utilized tree predictive models (i.e., random forest (RF), random tree (RT), and classification and regression trees (CART)) as well as a novel feature selection (FS) technique to introduce a new model capable of estimating the punching shear capacity of the SFRC flat slabs. Furthermore, to automatically create the structure of the predictive models, the current study employed a sequential algorithm of the FS model. In order to perform the training stage for the proposed models, a dataset consisting of 140 samples with six influential components (i.e., the depth of the slab, the effective depth of the slab, the length of the column, the compressive strength of the concrete, the reinforcement ratio, and the fiber volume) were collected from the relevant literature. Afterward, the sequential FS models were trained and verified using the above-mentioned database. To evaluate the accuracy of the proposed models for both testing and training datasets, various statistical indices, including the coefficient of determination (R2) and root mean square error (RMSE), were utilized. The results obtained from the experiments indicated that the FS-RT model outperformed FS-RF and FS-CART models in terms of prediction accuracy. The range of R2 and RMSE values were obtained as 0.9476–0.9831 and 14.4965–24.9310, respectively; in this regard, the FS-RT hybrid technique demonstrated the best performance. It was concluded that the three hybrid techniques proposed in this paper, i.e., FS-RT, FS-RF, and FS-CART, could be applied to predicting SFRC flat slabs.
•Evaluation of punching shear design provisions according to Eurocode2.•New Uniform Design Method for punching shear in flat slabs and column bases.•New databank consisting of 476 punching tests on ...flat slabs and column bases.
The punching shear design of flat slabs and column bases was revised with the introduction of Eurocode 2. While in many former codes the punching shear resistance was determined regardless of the type of member, in Eurocode 2 two different design equations for flat slabs and column bases were introduced. Additionally, different control sections for flat slabs and column bases were defined. The differentiation between flat slabs and column bases and especially the iterative design procedure for the determination of the punching shear resistance of column bases require great effort in daily practice.
Based on the punching shear provisions according to Eurocode2, a new Uniform Design Method (UDM) for flat slabs and column bases is developed. The derivation of the design method is described in detail. To verify the changes in the current design provisions, the new design method is evaluated using large databanks for flat slabs and column bases without and with shear reinforcement as well as systematic test series.
The currently dominant view concerning humor ethics is punching up/punching down. According to this view, members of one community with less social capital are allowed to make jokes at the expense of ...another with more social capital as a means of achieving social justice, while those in a community with more social capital are forbidden from making jokes about those with less. The latter is considered an act of bullying, which further entrenches pre-existing social injustice. While there is value in the moral intuitions that underlay this view, it falls prey to several problems. A new approach, the joke capital approach, is introduced which has the virtue of accounting for the cases in which punching up/punching down is effective but also is capable of handling the problematic cases.
•Flat slabs with the rational use of UHPFRC were studied by NLFEA.•The influence of the UHPFRC layer geometry and reinforcement ratio was evaluated.•Recommendations were given to assess the punching ...capacity of these connections.•The proposed approach was validated against experimental and numerical results.
The outstanding mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) can be used to improve the punching behavior of new slab-column connections. This study investigates the punching capacity of flat slab-column connections built with a rational combination of normal strength concrete (NSC) and UHPFRC in critical shear regions through non-linear finite element analyses (NLFEA) and by a punching shear model based on the critical shear crack theory (CSCT). Ten control tests from the literature were used to validate the Finite Element Models (FEM) developed to capture the behavior of slab-column connections made entirely with NSC, UHPFRC, and a combination of both materials. Parametric analyses were performed to investigate the behavior of connections with the rational use of UHPFRC, varying the reinforcement ratio, area, and thickness of the UHPFRC layer. The results indicated that placing a UHPFRC layer near the column in the slab compression zone significantly increases the punching capacity and deformation capacity compared to placing UHPFRC on the tensile side. The punching capacity enhancements varied between 26% and 156%, according to the reinforcement ratios and configurations of the UHPFRC layer investigated. The mean ratio between predicted punching capacities by advanced NLFEA and the analytical method proposed was 1.09, with a coefficient of variation of 10.3%. Therefore, the results indicated that the design of flat slabs with UHPFRC at the critical shear regions is a viable solution. Finally, the CSCT model can be used in design to predict the punching capacity of these connections.
•An effect of subsoil modelling on the test results in the case of footings subjected to punching.•The accuracy of the current and 2nd generation EC2 models for predicting punching capacity of the ...footings.•An effect of shear slenderness on punching shear capacity of the footings.•Post-punching resistance of the footings resting on the gravel cushion.
The results of an experimental program on the punching-shear capacity of foundation footings without shear reinforcement are presented and discussed in this paper, in the case of four tests on as many footings resting on a quasi-natural subsoil (top thin sand layer and bottom thick gravel layer). The design models of EC2 (2004) and prEC2 (2020) for the prediction of the punching-shear capacity are checked as well, by considering 90 tests well documented in the literature and the four tests performed in this research project. Special attention is devoted to the role played by the subsoil of the footing. The largest differences between the test results and the predictions occur in the case of quasi-natural subsoils, while the footings resting on point supports yield the smallest differences. The comparison of experimental and predicted capacities shows that the current model in EC2 (2004) is neither reliable nor safe, for any type of subsoil, since the ratio between the experimental and the assessed values of the load-bearing capacity ranges from 0.625 and 0.810 in 95% of the cases, depending on subsoil properties. On the contrary, the second-generation model introduced in prEC2 (2020) provides better results, since the previous ratio is close to 0.95 in 95% of the cases examined in the paper.
•RECC slab-column connections showed flexural-triggered or punching shear failure.•Flexural-triggered failure modes has ductility ratios between 1.63 and 6.4.•Ductile failure modes can be achieved by ...adjusting reinforcement ratio.•Ultimate strength of RECC specimens were estimated and the errors are within 15%.
RC flat-slab is widely regarded as one of the mainstream design solutions in commercial engineering projects due to its flexibility and the characteristic of maximization of floor-to-floor height. However, RC slab-column connections are vulnerable to punching shear failure due to the brittle tensile behavior of standard concrete. Engineered cementitious composites (ECC) have greater ductility than standard concrete which makes it ideal for slab-column connections. In this study, five RECC slab-column connections, which have different reinforcement ratios (ρ) and span ratios (λ), were tested under concentric gravity load to investigate their failure behaviors. Reinforcement ratios of ρ = 0.2%, 0.6%, 1.4% and 2.3%, as well as span ratios of λ = 8.4 and 5.7 were considered. Flexural strengths Vflex of specimens were estimated based on yield-line theory, and punching shear strengths Vpun of specimens were estimated by empirical formulas of ACI and JSCE codes. The main conclusions obtained in this study are as follows: (1) At a fixed span ratio of λ = 8.4, specimen with ρ = 0.2% experienced premature flexural failure after yielding reinforcement, while specimens with ρ = 0.6% and 1.4% both experienced flexural-triggered punching shear failure. In addition, premature punching shear failure occurred in ρ = 2.3% specimen. For specimens with λ = 5.7 and ρ = 1.4%, the flexural-triggered punching shear failure was also exhibited. (2) The ductility ratios of specimens with flexural-triggered failure modes (i.e. premature flexural failure and flexural-triggered punching shear failure) varied from 1.63 to 6.4. Premature flexural failure has the lowest ductility ratio of 1.63 amongst the flexural-triggered failure modes. Additionally, punching shear failure has the lowest ductility ratio of all the failure modes, which is close to 1.0. (3) The lesser of Vflex and Vpun was adopted as the estimated ultimate load, the errors between the test results and the estimated values are within 15%. (4) Flexural-triggered failure modes or strong-shear-weak-bending design can be achieved by making Vpun>Vflex through restricting the maximum reinforcement ratio. Premature flexural failure can be avoided by limiting the minimum reinforcement ratio.
PDF
