Analysis of The Most Affecting Factors in The Selection of Conventional and Precast Concrete Floor Slabs on Time Performance ( Case Study : IKEA Jakarta Garden City Project )

One of the efforts to achieve the goals of construction project in terms of cost, quality and time is to replace conventional methods with more modern ones, namely by applying precast concrete. Precast concrete products, especially for buildings, are quite varied, one of them is Hollow Core Slab (HCS). Supported by previous research which explains that precast concrete floor slabs can save processing time compared to conventional floor slabs. Therefore, it is necessary to identify factors and variables that affecting the selection of conventional and precast floor plates on time performance and how the influence of the X variable (Factors) on the Y variable (Time performance).The results showed that the most affecting factors in the selection of conventional floor slabs on time performance were manpower factor with variable number of workers (41.3%), location factor with variable distance of batching plant to project site (19.8%), and also technical factors with shop drawing revision variable (by 41.8%). As for, the most affecting factors in the selection of precast concrete floor slabs on time performance include manpower factors with worker’s expertise variable (29.7%), and technical factors with shop drawing revision variable (by 38.4%).


Introduction
With the increasing number of infrastructure and building construction in Indonesia, the development of technology and innovation in the world of construction should be growing. These innovations are expected to have a good impact in the implementation of construction. To achieve the requirements of cost, quality and time, it is necessary to carry out work efficiently and effectively. One of the efforts made is to replace conventional methods with more modern ones, namely by applying precast concrete. The consideration of the timing of the selection of the precast system has an effect on improving the performance of the implementation of building construction projects later (Rusli et al., 2018).
Hollow Core Slab is a type of precast floor slabs that is commonly used in building construction projects that have a hole in the center of the floor slab. Hollow Core Slabs made fabricated using special molds and pretension system, where the pre-stressed cable is pulled first before casting.
Based on research (Najoan et al., 2016) Hollow Core Slab can save 28 days beside conventional slab. Meanwhile, (Firdaus et al., 2017) showed that Hollow Core Slab is 12 days more efficient than conventional one. This becomes one of the considerations in choosing the method of concrete floor slabs on construction projects. Therefore, it is necessary to further review the factors and variables for selecting the use of precast slabs or HCS (Hollow Core Slab) on the time performance of project implementation time compared to conventional concrete floor slabs and to determine how far these factors and variables can affect time performance.

Identification of problems
Related to the research background, it is necessary to identify the following things: 1. Factors and variables that affecting the selection of conventional precast concrete floor slabs on time performance.

The effect of variable X (Factors) on variable Y (Performance time).
This needs to be reviewed because there is still a lack of previous research that compares the two methods and obtains the value of contribution in the selection of a method in terms of implementation time. ADRI INTERNATIONAL JOURNAL OF SCIENCES,ENGINEERING AND TECHNOLOGY VOLUME 6 │ NUMBER 1 │ MAY 2021 http: //adri.journal.or.id/index.php/ijset/index ISSN: 2549-5518 ;2549-550X Attribution 4.0 International (CC BY 4.0) You are free to: Sharecopy and redistribute the material in any medium or format, Adaptremix, transform, and build upon the material for any purpose, even commercially 21

Research Purpose and Objectives
The purpose of this study are: 1. To know the factors and variables that affecting the selection of conventional and precast floor slabs on time performance 2. To know how does variable X (factor) affect on variable Y (time). 3. Which is variable X is the factors that affect the selection of conventional and precast concrete floor slabs, while Variable Y is time performance.

Methodology
In this study, the results of the respondent's questionnaire, site observation and documentation are used as a primary data collection and for secondary data came from previous journals or literature study. This researched method uses quantitative research, which was conducted through statistical analysis testing with SPSS 26. The test instrument including normality test, validity test, reliability test, and multiple linear regression analysis including the coefficient of determination, F test and T test. The research flowchart in this study is as follows: You are free to: Sharecopy and redistribute the material in any medium or format, Adaptremix, transform, and build upon the material for any purpose, even commercially 22

Factors and Variables
The factors and variables proposed for the distribution of the first expert validation questionnaire are as follows: Table 1. Proposed Factors and Variables

The Result of First Expert Validation
After the first expert validation, it was obtained 17 variables of 30 variables that are considered affected the selection of concrete floor slabs method by the expert. So that, these variables will be proposed in the distribution of the respondent's questionnaire. Worker's dicipline X4 (Palusia, 2018) B Location Factors Weather X5 (Najoan et al., 2016) Alternative road access X6 (Najoan et al., 2016) Stockyard X7 (Najoan et al., 2016) Distance between Batching Plant to Site Project X8 (Syamsuddin et al., 2019) Area clearing X9 C Technical Factor (Najoan et al., 2016)  You are free to: Sharecopy and redistribute the material in any medium or format, Adaptremix, transform, and build upon the material for any purpose, even commercially 23

Normality Test
Normality test is a test to see the distribution of research data is normal / not. The data can be said to be normally distributed if the result of the significance value is greater than the probability value of 5% or 0.05. The results showed that all variables have a significance level of 0.200, where the value is greater than 0.05, so that the data distribution can be said to be normally distributed.

Validity Test
Validity test is carried out to see the validity of a proposed variable. The validity of variable is seen from the comparison of the calculated r value and r table. With number of respondences is 33, so the value of r table is 0.344. The result showed that the variables (X13 and X28) have a value of calculated r < r table. So, it can be said that the variable X13 and X28 are invalid and it can be eliminated for the next test stage.

Reliability Test
Reliability test is used to determine whether the measuring instrument is reliable and remains consistent for repeated measurements. The reliability of variables is seen from Cronbach's Alpha value. From the result, it showed that Cronbach's Alpha value is 0.887. This value shows the "Good" category with a range of Cronbach's Alpha values of 0.7 < a < 0.9 based on Internal Consistency Table in (Riadi, 2016). So it can be said that all data is said to be reliable.

Multiple Linear Regression a. Coefficient of determination
The value of the coefficient of determination explains how big the ability of the variable X in explaining the variable Y. The value of the coefficient of determination ranges from 0 to 1. From the result, it showed that the value of Adjusted R Square is 0.836 or 83.6%. So, it can be said that the ability of variable X in explaining variable Y is 83.6%. While 16.4% is explained by other variables outside of this study.  You are free to: Sharecopy and redistribute the material in any medium or format, Adaptremix, transform, and build upon the material for any purpose, even commercially 24 Figure 5. Result of F Test in Conventional Concrete Floor Slab Method c. T Test The T test aims to determine whether the independent variables affect the dependent variable partially. The results of the T test can be determined by comparing the calculated t value and t table and comparing the significance values.
The t table value obtained is 2,110. This shows that the value of t count for X1, X8 and X11 is greater than t table. In addition, the significance value is also smaller than 0.05, which has a significant effect. So it can be concluded that the independent variables X1, X8 and X11 partially affect the dependent variable.

Normality Test
Normality test is a test to see the distribution of research data is normal / not. The data can be said to be normally distributed if the result of the significance value is greater than the probability value of 5% or 0.05. The results showed that all variables have a significance level of 0.200, where the value is greater than 0.05, so that the data distribution can be said to be normally distributed.  /adri.journal.or.id/index.php/ijset/index ISSN: 2549-5518 ;2549-550X Attribution 4.0 International (CC BY 4.0) You are free to: Sharecopy and redistribute the material in any medium or format, Adaptremix, transform, and build upon the material for any purpose, even commercially 25 2. Validity Test Validity test is carried out to see the validity of a proposed variable. The validity of variable is seen from the comparison of the calculated r value and r table. With number of respondences is 33,so the value of r table is 0.344. The result showed that the variables (X13 and X28) have a value of calculated r < r table. So, it can be said that the variable X13 is invalid and it can be eliminated for the next test stage.

Reliabiliaty Test
Reliability test is used to determine whether the measuring instrument is reliable and remains consistent for repeated measurements. The reliability of variables is seen from Cronbach's Alpha value. From the result, it showed that Cronbach's Alpha value is 0.914. This value shows the "Excellent" category with a range of Cronbach's Alpha values of a ≥ 0.9 based on Internal Consistency Table in (Riadi, 2016). So it can be said that all data is said to be reliable.

Multiple Linear Regression a. Coefficient of determination
The value of the coefficient of determination explains how big the ability of the variable X in explaining the variable Y. The value of the coefficient of determination ranges from 0 to 1. From the result, it showed that the value of Adjusted R Square is 0.819 or 81.9%. So, it can be said that the ability of variable X in explaining variable Y is 81.9%. While 18.1% is explained by other variables outside of this study. The F test aims to determine whether the independent variables affect the dependent variable simultaneously (together). The results of the F test can be determined by comparing the calculated F value and F table and comparing the significance values.
The F table value obtained is 2.290. This shows that the calculated F value > F table (10.041 > 2.290). In addition, the significance value is also smaller than 0.05, which has a significant effect. So it can be concluded that the independent variables simultaneously affect the dependent variable. The T test aims to determine whether the independent variables affect the dependent variable partially. The results of the T test can be determined by comparing the calculated t value and t table and comparing the significance values.
The t table value obtained is 2,120. This shows that the value of t count for X2 and X11 is greater than t table. In addition, the significance value is also smaller than 0.05, which has a significant effect. So it can be concluded that the independent variables X2 and X11 partially affect the dependent variable.