2.1 Introduction In a traditional way, a concrete mix is designed based on the code requirements and recommendations which uses the empirical values obtained from previous experiences. Compressive strength of concrete is determined by conducting standard uniaxial compression test on standard cylindrical sample specimens of ages 7 & 28 days, following the standard procedure and test values are reported in accordance with ASTM and ACI standards . If the strength value obtained from the test is less than the required strength after 28 days from date of placing of concrete, the entire process of concrete mix design has to be repeated until the required strength value is achieved, which is time consuming and costly. Numerous test samples with different mix ingredient proportions have to be created to achieve the required strength and is an iterative process. So, every mix designer wants a tool or methodology to predict the compressive strength of concrete required at the time of design, before placing the concrete. As we know that, the relationship between Compressive Strength and its mix ingredients is complex and highly non linear. The data scientists, researchers and engineers are trying to develop several approaches using regression function for the accurate prediction of compressive strength of concrete. Recently, data mining tools are becoming more popular and reliable methods to predict the compressive strength of concrete than others. The section below reviews and discusses some of the popular, relevant and effective data mining tools developed so far, to predict the 28 days compressive strength of concrete. 2.2 Multiple Regression Model The first popular regression equation used in the prediction of compressive streng... ... middle of paper ... ...per plasticizer, fine aggregates and coarse aggregates. The method of least squares is used to estimate the regression coefficients in the above model. A lot of researchers have used multiple regression models to improve the prediction accuracy of concrete strength. It is still a popular model because the model that once fitted can predict the required value more quickly than other modeling techniques and can be easily implemented in computer applications. By performing correlation analysis, it also provides insight knowledge about the key factors influencing the 28 days compressive strength of concrete. Although it gives better performance where there are few independent variables, it performs poor modeling when the number of independent variables is more and the relationship between independent variables and dependent variable becomes complex and highly nonlinear.
α is the intercept of the regression line, and β is the slope of the regression line. e is the random disturbance term. The equation Y = α + βX (ignoring the disturbance term “e”) gives the average relationship between the values of Y and X.
in the linear regression model. The R for the linear model is -.632 and the R in
Regression analysis is also used to understand which among the independent variables are related to the dependent variable, and to explore the forms of these relationships. In restricted circumstances, regression analysis can be used to infer causal relationships between the independent and dependent variables. However this can lead to illusions or false relationships, so caution is advisable;[2] for example, correlation does not imply
Analysts will input the following information into a simple linear regression model provided in Excel QM using a simple linear regression formula Yi =b_0+ b_1 X_1. In FIGURE 1-3 the highlighted Coefficients are provided. The b_0 is -18.3975 and the b_1 is 26.3479, these coefficients are added to the formula that is represented in figure 1-4.
Checking the opening of cracks and stress limits, will not be required for concrete elements. When the tensile flexural stress exceeds the effective tensile strength fcteff, then a check for pre-stressed concrete is required. This should normally occur when sections do not have tendons near the tension face or there is no exposure to chlorides, so decompression doesn’t have to be checked. The analysis using uncracked section will be done in sections controlled for decompression and have tendons near the surface tension. As the cracked section analysis is done by computer, it solves the complexity of the calculations. However, this does not mean that pre-stressed cannot be calculated directly from a set of equations as with crack width checks for RC.
Using All Possible Subsets Regression Models, there are 2p -1 models, where p is the number of predictors in the full model . There are 23 -1 = 7 possible subsets for these data. Regression models with 1 variable are X1,X2 and X3 , with two variables X1X2, X1X3 and X2X3 and with three variables, X1X2X3. The results for the model selection criterion for each of the subset with classical method using OLS for both original and clean data and Robust MAD using LTS for original data are shown below:
Concrete is one of the world’s most popular construction materials. Some six billion tonnes of concrete is produced each year in the world, making it approximately one ton of concrete for every human being per year (Fardis, 2012, p.116). However, the lifecycle of concrete does not make it the most sustainable building material at the moment. Because of limited natural resources, concerns over green house gases, and landfill problems, concrete production is being cut-back, or at least cannot be increased to keep up with population increase. In this essay, I will look at what makes concrete an unsustainable material and possible solutions to make concrete a more sustainable material.
Concrete can be an excellent choice for paving driveways, parking lots, walkways and other areas. When many customers begin considering having concrete installed, they often ask about the best thickness for the slab. Although many municipalities have established codes that require a specific minimum thickness, in some cases, the actual number may be higher than the one required by the code. Therefore, a concrete contractor must consider a variety of factors before deciding on how thick to make the slab.
The strength developed by portland cement depends on its composition and the fineness to whi...
Now a days HPC is expensive than conventional concrete. It require additional materials in some quantities as to meet specified performance.These additional materials are cement,silica fume,...
Our regression estimation showed that minimum wage, labor force, job openings, hires rate, and unemployment
In this report, we will introduce and illustrate on precast concrete, pre-stressed concrete, ready-mix concrete, reinforced concrete, terrazzo and Urbanite in details.
The data obtained and used for estimation would be presented in tabular form so as to ensure a clear view of variables. The data would also be analyzed following the trend of the growth pattern of the different variables.
The line of regression is the regression line of best fit or the regression line.
Simple linear regression is a model with a single regressor x that has a relationship with a response y that is a straight line. This simple linear regression model can be expressed as