scholarly journals Prediction of Concrete Failure Time Based on Statistical Properties of Compressive Strength

2020 ◽  
Vol 10 (3) ◽  
pp. 815
Author(s):  
Jiao Wang ◽  
Weiji Zheng ◽  
Yangang Zhao ◽  
Xiaogang Zhang
Keyword(s):  
Compressive Strength ◽  
Failure Time ◽  
Reliability Evaluation ◽  
Structural Safety ◽  
Time Varying ◽  
Concrete Failure ◽  
Proposed Model ◽  
Compressive Strength Of Concrete ◽  
Mc Simulation ◽  
Good Agreement

Since the heterogeneity of the cement-based material contributes to a random spatial distribution of compressive strength, a reliability analysis based on the compressive strength of concrete is fundamental to carry out structural safety assessment. By analyzing 10,317 datapoints on compressive strength of concrete, a time-varying reliability evaluation based on the third-moment (TM) method was proposed to predict the service life of concrete. Unlike the second-moment (SM) method, skewness is taken into account in the TM; thus, the calculated result of concrete failure time based on the TM is more accurate. In this paper, the errors of the calculated results using time-varying reliability evaluation are within 3%, as shown by Monte Carlo (MC) simulation. In addition, the proposed model (aiming to calculate the equivalent design compressive strength) verifies the concrete failure time calculated by time-varying reliability. According to the results, concrete failure times calculated by these two models are in good agreement. Overall, based on the simple and effective methodology adopted in this paper, it is feasible to develop time-varying reliability based on other factors that might also lead to concrete failure, such as carbonation-induced corrosion, cracking, or deflection of the concrete.

scholarly journals Time-Varying Reliability Evaluation of Concrete Based on Carbonation Depth

2019 ◽  
Vol 9 (23) ◽  
pp. 5116
Author(s):  
Jiao Wang ◽  
Weiji Zheng ◽  
Yangang Zhao ◽  
Xiaogang Zhang
Keyword(s):  
Safety Assessment ◽  
Concrete Surface ◽  
Reliability Evaluation ◽  
Structural Safety ◽  
Time Varying ◽  
Carbonation Depth ◽  
The Third ◽  
Mc Simulation ◽  
Traditional Approaches ◽  
Third Moment

When studying concrete impairment, the carbonation depth of concrete is regarded to be variable. Therefore, a time-varying reliability evaluation is important to perform a structural safety assessment. By analyzing 13,198 data on the carbonation depth of concrete, we propose a time-varying reliability evaluation based on the third-moment (TM) method to predict the service life of concrete. Validated by Monte Carlo (MC) simulation, the errors of the calculated results using time-varying reliability evaluation were within 4%. It is shown that the TM method proposed in this paper is more practical than traditional approaches such as MC simulation and second-moment (SM) methods in probability analysis. In this paper, exponential distribution was used to characterize the distribution of carbonation depths. Since paint was present on the concrete surface, numerous uncarbonized concrete components were found in the experiments; to develop a time-varying model considering the uncarbonized components, a function for evaluating the ratio of carbonized concretes is proposed. Overall, the time-varying TM method provided in this paper can act as a foundation for other investigations on probabilistic analysis, e.g., of compressive strength, deflection, and crack of concrete, which can be used to evaluate the reliability of concrete.

scholarly journals Study of the influence of compressive strength concrete on columns during the design of a multi-floor building

2019 ◽  
Vol 12 (5) ◽  
pp. 1126-1147
Author(s):  
G. M. FREGONEZI ◽  
W. W. WUTZOW ◽  
R. D. VANDERLEI
Keyword(s):  
Compressive Strength ◽  
Concrete Columns ◽  
Structural Safety ◽  
Structural Elements ◽  
Computational Tool ◽  
Stability Parameters ◽  
Total Cost ◽  
Strength Concrete ◽  
Compressive Strength Of Concrete ◽  
Materials Used

Abstract This work aims to analyze the influence of the compressive strength of concrete columns in the design of a multi-floor building using the CAD/TQS computational tool. The strengths of the columns varied in increments of 5 MPa, from 35 MPa to 90 MPa, with a 35 MPa resistance in the remaining structural elements. Analyses of the horizontal deformability, stability parameters, and optimized sections, as well as quantities and cost of the main materials used (concrete, steel, and formwork), were performed. As a result, a 32% reduction to the total area of the columns was achieved; consequently, a reduction in material quantities and the total cost of the building was also achieved. Thus, greater durability was provided without major costs or loss in structural safety.

Dynamic Behavior of Helical Gears with Effects of Shaft and Bearing Flexibilities

2011 ◽  
Vol 86 ◽  
pp. 26-29
Author(s):  
Kai Feng ◽  
Shigeki Matsumura ◽  
Haruo Houjoh
Keyword(s):  
Experimental Tests ◽  
Time Varying ◽  
Gear Pair ◽  
Contact Ratio ◽  
Mesh Stiffness ◽  
Helical Gears ◽  
Shaft System ◽  
Proposed Model ◽  
Center Distance ◽  
Good Agreement

This study presents a numerical model of helical gears to consider the effects of shaft and bearing flexibility. A primary feature of this study is that the time-varying mesh stiffness is not just determined by the geometry of gear pair but also updated for each iteration according to the change of center distance. The effects of shaft and bearing flexibilities are discussed by comparing the dynamic response of gear pairs supported with a rigid and a flexible bearing-shaft system. The results show that the pressure angle and contact ratio are significantly changed due to the center-distance variation of gears and the gear pair with a flexible bearing-shaft system has much larger vibration. Finally, experimental tests are conducted to validate the proposed model. The predicted results show good agreement with the experimental data.

Predicting the Strength of Rectangular Reinforced Concrete Columns Confined with FRP Sheets

2022 ◽  
Vol 906 ◽  
pp. 17-23
Author(s):  
Ashot G. Tamrazyan ◽  
Yehia A.K. Sayed
Keyword(s):  
Compressive Strength ◽  
Regression Analysis ◽  
Concrete Columns ◽  
Test Results ◽  
Rc Columns ◽  
New Model ◽  
Proposed Model ◽  
Axial Compressive Strength ◽  
Frp Sheet ◽  
Good Agreement

A complete reorganization about the behavior of rectangular RC columns confined with FRP sheet is very important to predict the axial compressive strength values of the strengthened rectangular RC columns. That is because the process of strengthening RC rectangular column depending on several parameters that role this type of strengthening. These parameters include the characteristics of the used fiber, the grade of concrete and the geometry of the cross section including the rectangularity aspect ratio, corner radius, and size of specimens. Besides that, using a wide scope of experimental data may affect positively to generalize a model that considers the whole parameters affect the value of the axial strength. So, in this paper a review about parameters that affect the axial compressive strength values of rectangular RC columns was conducted. After that, based on the test results regarding FRP-confined rectangular RC columns available in the literature or conducted by the author, some existing confinement models for rectangular RC columns were assessed. Further, a new model is proposed through regression analysis of the database. A new model is proposed through regression analysis of the database. The proposed model was found to be in good agreement with the test results in the database. Finally, based on the results conclusions were drawn.

scholarly journals Bond Properties of Steel Bar in Concrete under Water Environment

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3517 ◽  
Author(s):  
Li Song ◽  
Fulai Qu ◽  
Guirong Liu ◽  
Shunbo Zhao
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Water Environment ◽  
Splitting Tensile Strength ◽  
Soaking Time ◽  
Bond Slip ◽  
Pull Out ◽  
Steel Bar ◽  
Compressive Strength Of Concrete ◽  
Good Agreement

The present study concerns the bond behavior of steel bar in concrete under a water environment. This topic was put forward because of the changes of concrete under a water environment and the importance of reliable anchorage of steel bar for reinforced concrete structures. Thirty bond specimens with deformed steel bars were immersed in water and experimentally studied by pull-out tests. The soaking time from 28 day to 360 day and the cubic compressive strength of concrete with 20 N/mm2 and 40 N/mm2 were considered as the main parameters. The results indicate that the moisture content, compressive strength, and splitting tensile strength of concrete are affected by the water environment; the splitting tensile strength varies almost linearly with the compressive strength of concrete; and the descent portion of the bond–slip curve dropped slowly owing to the confinement of stirrups. On the basis of the test data, the formulas for the prediction of bond strength, residual strength, and the corresponding slips with different soaking time are proposed. Finally, the constitutive relation of bond–slip with two portions in the water environment is established with good agreement with the experimental bond–slip curves.

Evolution Model of Concrete Failure Surface under the Action of Load and Frezee-Thaw Cycles

2013 ◽  
Vol 684 ◽  
pp. 163-167
Author(s):  
Si Jia Chen ◽  
Xiao Bing Song ◽  
Xi La Liu ◽  
Jia Chao Zhang
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Failure Surface ◽  
Simultaneous Action ◽  
Stress Space ◽  
Freeze Thaw ◽  
Concrete Failure ◽  
Principal Stress Space ◽  
Compressive Strength Of Concrete ◽  
External Loads

Concrete failure surface is the most important tool to predict concrete strength under complicated load. Most concrete structures in cold regions are subjected to both external loads and freezing-thawing, while now most researchers focused on the freeze-thaw durability of concrete without external loads. To make up the deficiency, the degradation of compressive strength of concrete under the simultaneous action of external loads and freezing-thawing are experimentally investigated in this research. Finally, a concrete failure criterion is adopted to establish an applicable failure surface in principal stress space for concrete.

scholarly journals Comprehensive Machine Learning-Based Model for Predicting Compressive Strength of Ready-Mix Concrete

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1068
Author(s):  
Jiajia Xu ◽  
Li Zhou ◽  
Ge He ◽  
Xu Ji ◽  
Yiyang Dai ◽  
...  
Keyword(s):  
Machine Learning ◽  
Compressive Strength ◽  
Pearson Correlation ◽  
Influential Factors ◽  
Structural Safety ◽  
Percentage Error ◽  
Modeling Framework ◽  
Machine Material ◽  
Proposed Model

Considering that compressive strength (CS) is an important mechanical property parameter in many design codes, in order to ensure structural safety, concrete CS needs to be tested before application. However, conducting CS tests with multiple influencing variables is costly and time-consuming. To address this issue, a machine learning-based modeling framework is put forward in this work to evaluate the concrete CS under complex conditions. The influential factors of this process are systematically categorized into five aspects: man, machine, material, method and environment (4M1E). A genetic algorithm (GA) was applied to identify the most important influential factors for CS modeling, after which, random forest (RF) was adopted as the modeling algorithm to predict the CS from the selected influential factors. The effectiveness of the proposed model was tested on a case study, and the high Pearson correlation coefficient (0.9821) and the low mean absolute percentage error and delta (0.0394 and 0.395, respectively) indicate that the proposed model can deliver accurate and reliable results.

Effects of Silica Fume on Concrete Compressive Strength

2015 ◽  
Vol 744-746 ◽  
pp. 78-81 ◽  
Author(s):  
Hua Xi Li
Keyword(s):  
Mathematical Model ◽  
Compressive Strength ◽  
Silica Fume ◽  
Polymer Binder ◽  
Concrete Compressive Strength ◽  
Proposed Model ◽  
Strength Based ◽  
Compressive Strength Of Concrete

The effects of silica fume (SF) on compressive strength of concrete have been analyzed. The compressive strength results of concrete mixed over different water–binder ratios as well as different replacing percentages of SF were analyzed. The results of the experiments showed that when the polymer/binder materials ratio increases, the compressive strength of concrete decreases. A mathematical model has been proposed for evaluating the strength of concrete containing SF. The proposed model provides a probability to analyze compressive strength based on the time of curing in water (t), water to binder materials ratios and SF to binder materials ratios which are shown as (w/b) and (s). This model might serve as a useful guide for increasing concrete compressive strength.

A Stress-Strain Model for Unconfined in Compression Considering the Size Effect

2018 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Ju-Hyun Mun
Keyword(s):  
Compressive Strength ◽  
Aspect Ratio ◽  
Size Effect ◽  
Maximum Stress ◽  
Damage Zone ◽  
Peak Stress ◽  
Specimen Width ◽  
Proposed Model ◽  
Compressive Strength Of Concrete ◽  
Strain Model

In this study, the model proposed by Yang et al. to generalize the stress–strain model for unconfined concrete with consideration of the size effect is expanded. Sim et al.’s compressive strength model that is based on the function of specimen width and aspect ratio was used for the maximum stress. In addition, a strain at the maximum stress was formulated as a function of compressive strength by considering the size effect using the regression analysis of datasets compiled from a wide variety of specimens. The descending branch after the peak stress was formulated with consideration of less dissipated area of fracture energy with the increase in specimen width and aspect ratio in the compression damage zone (CDZ) model. The key parameter for the slope of the descending branch was formulated as a function of specimen width and aspect ratio, concrete density, and compressive strength of concrete considering the size effect. Consequently, a rational stress–strain model for unconfined concrete was proposed. This model explains the trends of the peak stress and strain at the peak stress to decrease and the slope of the descending branch to increase, as the specimen width and aspect ratio increase. The proposed model agrees well with the test results, irrespective of the compressive strength of concrete, concrete type, specimen width and aspect ratio. In particular, the proposed model for the stress–strain curve rationally considered the effect of decreasing peak stress and increasing the descending branch slope, with the increase in specimen width and aspect ratio.

scholarly journals Time-Varying Kelvin Wake Model and Microwave Velocity Observation

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1575 ◽  
Author(s):  
Jie Niu ◽  
Xingdong Liang ◽  
Xin Zhang
Keyword(s):  
Doppler Velocity ◽  
Time Varying ◽  
Millimeter Wave Radar ◽  
Proposed Model ◽  
Wave Radar ◽  
Application Potential ◽  
Wake Model ◽  
Simultaneous Switching ◽  
First Time ◽  
Good Agreement

In the synthetic aperture radar (SAR) imaging of ship-induced wakes, it is difficult to obtain the Doppler velocity of a Kelvin wake due to the lack of time-varying wake models and suitable radar equipment. The conventional Kelvin wake investigation based on the static Kelvin wake model failed to reflect time-varying characteristics, which are significant in the application of the Kelvin wake model. Therefore, a time-varying Kelvin wake model with consideration of geometric time-varying characteristics and the hydrodynamic equation is proposed in this paper, which reflects the wake’s time-varying change lacking in the conventional Kelvin wake investigation. The Doppler velocity measurement, measured by a specially designed radar, can be exploited to verify the time-varying model by the comparison of velocity fields. Ground-based multi-input multi-output (MIMO) millimeter wave radar imaging through the simultaneous switching of transceiver channels was used to obtain the Doppler velocity for the first time. Finally, promising results have been achieved, which are in good agreement with our proposed model in consideration of the experimental scene. The proposed time-varying model and radar equipment provide velocity measurements for the Kelvin wake observation, which contains huge application potential.

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