“…Most researchers (Grote et al, 2001; Chen et al, 2013; Hao and Hao, 2013; Wang et al, 2018; Ganorkar et al, 2021; Liu et al, 2021) correlate the dynamic compressive strength to the static compressive strength by dynamic increase factor (DIF) to quantify the strain rate sensitivity of the material. DIF is obtained as the dynamic compressive strength normalized by the average quasi-static compressive strength of concrete.…”
Section: Resultsmentioning
confidence: 99%
“…The researchers have different opinion with respect to the variation of critical strain (at maximum strength) with the strain rate. Ganorkar et al (2021) and Wang et al (2018) reported that the critical strain corresponding to maximum strength increases with an increase in the strain rate. Grote et al (2001) performed the experimental study on the mortar specimens and reported a slight increase in the critical strain with the increase in the strain rate.Figure 18.Strain rate effect on the critical and ultimate strain.…”
Split Hopkinson pressure bar (SHPB) system is significantly used for dynamic material characterization in the range of strain rates 102–104 s-1; however, there is no standard design methodology or readily available technique for the development of this apparatus. The objective of this study is to present a detailed design, development and calibration of SHPB apparatus for dynamic material characterization of concrete in compression. The calibration of the loading and bar components has been presented with the help of experimental results and validated following an analytical approach for one-dimensional stress wave propagation. The experimental pulse duration, 124.5 microsecond, and elastic wave speed, 4820 m/s, was measured with 2% deviation from the analytical results. Under three different impact velocities, a minimum 1.09% and maximum 4.14% decrement was observed in the incident wave as compared to analytical formulation. The recorded strain signals were captured in the transmission bar with a decrement of 1, 3, and 3.3% in peak strain when compared to the incident bar, at 4.5, 4.9, and 5.7 m/s impact velocities. The incident and transmission bars had almost identical wave characteristics demonstrating that the bar system has been perfectly and precisely aligned, and almost complete wave transfer is seen to have occurred. Experiments performed on M35 concrete specimens using the developed SHPB setup have been presented and discussed. The results demonstrated that the developed SHPB setup is capable to provide accurate results for the dynamic material characterization of concrete at high strain rate loading.
“…Most researchers (Grote et al, 2001; Chen et al, 2013; Hao and Hao, 2013; Wang et al, 2018; Ganorkar et al, 2021; Liu et al, 2021) correlate the dynamic compressive strength to the static compressive strength by dynamic increase factor (DIF) to quantify the strain rate sensitivity of the material. DIF is obtained as the dynamic compressive strength normalized by the average quasi-static compressive strength of concrete.…”
Section: Resultsmentioning
confidence: 99%
“…The researchers have different opinion with respect to the variation of critical strain (at maximum strength) with the strain rate. Ganorkar et al (2021) and Wang et al (2018) reported that the critical strain corresponding to maximum strength increases with an increase in the strain rate. Grote et al (2001) performed the experimental study on the mortar specimens and reported a slight increase in the critical strain with the increase in the strain rate.Figure 18.Strain rate effect on the critical and ultimate strain.…”
Split Hopkinson pressure bar (SHPB) system is significantly used for dynamic material characterization in the range of strain rates 102–104 s-1; however, there is no standard design methodology or readily available technique for the development of this apparatus. The objective of this study is to present a detailed design, development and calibration of SHPB apparatus for dynamic material characterization of concrete in compression. The calibration of the loading and bar components has been presented with the help of experimental results and validated following an analytical approach for one-dimensional stress wave propagation. The experimental pulse duration, 124.5 microsecond, and elastic wave speed, 4820 m/s, was measured with 2% deviation from the analytical results. Under three different impact velocities, a minimum 1.09% and maximum 4.14% decrement was observed in the incident wave as compared to analytical formulation. The recorded strain signals were captured in the transmission bar with a decrement of 1, 3, and 3.3% in peak strain when compared to the incident bar, at 4.5, 4.9, and 5.7 m/s impact velocities. The incident and transmission bars had almost identical wave characteristics demonstrating that the bar system has been perfectly and precisely aligned, and almost complete wave transfer is seen to have occurred. Experiments performed on M35 concrete specimens using the developed SHPB setup have been presented and discussed. The results demonstrated that the developed SHPB setup is capable to provide accurate results for the dynamic material characterization of concrete at high strain rate loading.
“…where f c,d is the dynamic compressive strength and f c,s is the quasistatic compressive strength. Test data for this article were contributed by several BFRC dissertations [30][31][32][33][34][35]. It was decided to utilize only specimens tested at 28 days, since many concrete standards focus on strength.…”
Split Hopkinson pressure bar (SHPB) tests are usually used to determine the dynamic mechanical strength of basalt-fiber-reinforced concrete (BFRC), but this test method is time-consuming and expensive. This paper makes predictions about the dynamic mechanical strength of BFRC by employing machine learning (ML) algorithms and feature sets drawn from experimental data from prior works. However, there is still the problem of improving the accuracy of the dynamic mechanical strength prediction by the BFRC, which remains a challenge. Using stacking ensemble learning and genetic algorithms (GA) to optimize parameters, this study proposes a prediction method that combines these two techniques for obtaining accurate predictions. This method is composed of three parts: (1) the training uses multiple base learners, and the algorithms employed by the learners include extreme gradient boosting (XGBoost), gradient boosting (GB), random forest (RF), and support vector regression (SVR); (2) multi-base learners are combined using a stacking strategy to obtain the final prediction; and (3) using GA, the parameters are optimized in the prediction model. An experiment was conducted to compare the proposed approach with popular techniques for machine learning. In the study, the stacking ensemble algorithm integrated the base learner prediction results to improve the model’s performance and the GA further improved prediction accuracy. As a result of the application of the method, the dynamic mechanical strength of BFRC can be predicted with high accuracy. A SHAP analysis was also conducted using the stacking model to determine how important the contributing properties are and the sensitivity of the stacking model. Based on the results of this study, it was found that in the SHPB test, the strain rate had the most significant influence on the DIF, followed by the specimen diameter and the compressive strength.
“…The strain rate of the split Hopkinson pressure bar (SHPB) is between 50 and 10 4 s -1 (Chen et al, 2003; Zhao and Gary, 1996), which is widely used in the high strain rate loading experiment to investigate the dynamic increase factor (DIF) of concrete (Al-Mousawi et al, 1997; Chen et al, 2020). The compressive strength, post-peak load-carrying capacity, and energy absorption capability of FRC are increased with increasing the fiber content under quasi-static loading and high strain rate loading (Ganorkar et al, 2021; Hao and Hao, 2013; Xu et al, 2012a). The larger the aspect ratio of the steel fibers, the greater the improvement in static and dynamic compressive strength of ultra-high performance FRC (Su et al, 2016; Yoo and Banthia, 2017a).…”
Reinforced concrete structures sometimes are deteriorated and damaged by seismic and blast wave loadings, and the resistance of fiber-reinforced concrete was tested at a loading of high-strain rate. Therefore, concrete structures were needed to improve the dynamic load resistance and energy absorption capabilities. In infrastructures, fiber is incorporated into concrete and is used to strengthen structures to increase its durability and resistance to high-strain rate loadings. In this study, the quasi-static and dynamic mechanical behaviors of Kevlar fiber-reinforced concrete were studied by the compressive strength test and Split Hopkinson Pressure Bar test, respectively. The 0.5% weight ratio Kevlar fiber content of KFRC specimens attained the highest strength in the quasi-static and dynamic test compared with benchmark and other 1.0%, 1.5% weight ratios. The KFRC specimens with the length of 12 mm and 24 mm exhibit similar effects in the quasi-static compressive strengths, but the KFRC specimens with the length of 24 mm fiber attained higher strain energies under dynamic loading.
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