Accelerating the middle – rise building construction duration using BIM 4D, a case study in central Jakarta

Construction planning involves scheduling and sequencing of project activities for proper execution. Research was conducted to obtain and enhance construction project scheduling, which was good and in accordance with the targets achieved. The results of the project performance analysis in the 9th month using the Earned Value Method resulted in SPI <1 and SV <0, indicating that the project experienced delays. Scheduling using the PDM based on the actual duration of the project shows that the project will be completed in 511 days. The project duration can be accelerated to 429 days by combining overlap and overtime methods. The scheduling results were simulated using BIM 4D to generate a visualization of the scheduling to improve the project monitoring process.


Introduction
Scheduling is a method of managing projects.Without scheduling, a construction project cannot be managed, resulting in many errors in the project.Scheduling is a part of the workflow guidelines for operating a project.Monitoring the schedule generates an idea of the impact of problems contained in the project and generates opportunities to increase or decrease the scope of the phases of the project [1].
Delays in construction projects can have negative effects.The consequences of delays can be late resolution, disputes, damage to the company's reputation, loss of future project opportunities, loss or reduction of profit margins, company bankruptcy, contract termination, and so on.Delays in construction projects can extend the duration of project completion, increase project costs, and endanger quality and safety [2].
To overcome these delays, project acceleration or project crashes are required.Project Crashing is a process that is carried out systematically and analytically by testing all activities in a project that focus on activities that are on the critical path [3].
4D Building Information Modeling (BIM) provides the best solution for construction work in 2D project planning and scheduling with 4D visualization techniques, thereby increasing the operating IOP Publishing doi:10.1088/1755-1315/1324/1/012022 2 range in real time.4D BIM visualization has the potential to view all project details from start to finish and automatically view project work and resources at any given time without analyzing a traditional Gantt chart.4D BIM provides rapid information and clear communication through real-time scheduling tracking with intelligent process updates.Time-based clashes can be detected and solved as early as possible [4].
Project construction requires rapid decision-making, starting from the planning stage to the construction stage.Therefore, based on the attachment to regulations of the Ministry of Public Works and Public Housing Number 22 of 2018, Building Information Modeling (BIM) was implemented in state buildings with an area of 2000 m 2 and more than two floors.BIM implementation has a significant impact on accelerating infrastructure development, making it more efficient and productive.Based on the research that has been conducted, by utilizing BIM, time and cost savings can be achieved because it can speed up the planning process and can predict errors that will occur in the field by performing clash detection.

Research Methods
This research was conducted based on the data obtained from the project in the form of shop drawings, project master schedule, and Bill of Quantity (BQ).Project shop drawings in 2D CAD form were converted into 3D modeling using Autodesk Revit software.Then, project scheduling is linked to 3D modeling so that it becomes a 4D BIM to obtain a visualization of project scheduling.Project performance analysis is carried out using Earned Value Analysis to determine the project performance and estimated completion time.To catch up with project construction progress, several acceleration scenarios are required.In this study, the overlapping method, overtime, and a combination of the two methods were used.The scheduling of the project acceleration scenario is carried out using the Precedence Diagram Method (PDM) to obtain the critical path and total duration of the project.The conclusions of this study were derived from the fastest and most effective acceleration methods (Fig. 1).
The concept of Earned Value is a method for measuring the amount of work that is actually done on a project to measure the progress, estimated costs, and the project completion date.In accordance with the complexity level of a project, delays often occur and cause cost overruns.The concept of earned value can be used as a performance measurement tool that integrates cost and time [5] Overtime acceleration method =

Working hours
Working hours + Productivity coef.

× normal duration (6)
Where BCWS, BCWP and contract value in Rupiahs, ATE is Actual Time Expended, OD is Original Duration.

Data and analysis
The main objective of this study is to create a project scheduling simulation using 4D Building Information Modeling (BIM) by integrating project scheduling into 3D BIM.3D BIM was created using Autodesk Revit 2020 software by converting 2D shop drawings into 3D modeling, and 4D BIM simulation was created using Navisworks Manage 2020 software.In 4D BIM, each building 3 component is linked to a schedule contained in the project scheduling to produce a project development simulation.
In this study, project scheduling was evaluated using the concept of Earned Value Analysis to determine the amount of delay and time required to complete the project.Project scheduling is calculated using the Precedence Diagram Method (PDM) to determine the critical path and fastest completion duration of the project.Visualization of the deviation between planned and actual progress can be seen using 4D BIM, making it easier to monitor and track a project.

Project Information
This study was conducted on a middle-rise building construction project in Jl.Raden Saleh, Cikini, Central Jakarta.This project consists of eight floors with one basement.This project is planned for completion within 420 days starting from 29 July 2019 to 20 September 2020 with a contract value of IDR 39,710,000,000.
The Ibis Raden Saleh project has been delayed since the first month of construction.This delay was caused by various factors such as human resources, bad weather, change orders, and the COVID-19 pandemic.With a series of delays in project activities, in the 9th month, the project had just completed progress of 38.69% which should have been completed by 80.36%.Therefore, it is necessary to have an acceleration simulation so that the project does not experience greater losses because it is already in the construction phase.

Project Performance using Earned Value Analysis
The concept of Earned Value is a method for measuring the amount of work that is actually done on a project to measure the progress, estimated costs, and the project completion date.In accordance with the complexity level of a project, delays often occur and cause cost overruns.The concept of earned value can be used as a performance measurement tool that integrates cost and time [5] The BCWP is the value received from the completion of work during a certain period (Table 2).The BCWP was calculated based on the accumulation of completed work.The following is an example of BCWP calculation in the first month: BCWP = 1,31% × 39,710,000,000 = Rp520,201,000 The time parameter is a detailed calculation that integrates the time aspect with the project costs.The calculation of the time parameter for the earned value concept is as follows: • Schedule Variance (SV) Schedule Variance (SV) on the 40 th week or end of the 9 th month can be calculated using the following equation: SV = 15,363,799,000 -31,909,030,065 = -16,545,231,065 An SV < 0 indicates that the project experienced a delay from the planned schedule.
• Schedule Performance Index (SPI) The ((SPI) on the 40 th week or end of the 9 th month can be calculated using the following equation: SPI = 15,363,799,000 / 31,909,030,065 = 0,48 SPI < 1 indicates that the project experienced a delay from the planned schedule.

• Time Estimate (TE)
The time Estimate (TE) was calculated using the following equation:  -Overlapping Method Acceleration Overlapping can be performed on jobs that are not interconnected or that interrupt each other.
Overlapping of work can be done by advancing one of the jobs according to its dependency logic.Overlapping work can be performed without increasing the work duration or the number of workers.Figure 3 shows the duration after overlap.

Overtime Acceleration Method
Additional overtime working hours can be performed on jobs that are in the critical path because these jobs cannot be postponed.Overtime hours are added for jobs that have not been done, with a maximum of four hours of overtime.Based on the analysis of the additional 1-hour overtime duration, the duration obtained was 184 days, and an additional 2 h of overtime resulted in a project completion duration of 160 working days from the remaining duration of 140 days.The addition of an overtime duration of 2 h is still in IOP Publishing doi:10.1088/1755-1315/1324/1/0120227 accordance with the regulations of the Ministry of Manpower's overtime hours, which are a maximum of 3 hours per day and 14 hours per week.

Combination of Overlapping and 2 Hours Overtime
A combination of the two acceleration alternatives can be achieved by overlapping the accelerated schedule with the addition of working hours.The work done by adding working hours is the work on the critical path, as shown in Figure 4.

Project Crashing Comparison
The fastest duration was 128 days obtained by combining the two acceleration alternatives.The additional two hours of working hours resulted in an increase in overtime paid for workers, but there was no increase in the number of workers.The resulting duration, with the addition of working hours, was also shorter.Table 3 presents a comparison of the monthly progress of the acceleration alternatives.

Project Crashing Simulation using BIM 4D
The project has completed a construction progress of 38.69% in the 9th month with a completion plan of 80.39%.To complete the project within the desired duration target, project acceleration must be performed on the work that is on the critical path.With the alternative combination of overlap acceleration and additional working hours, the total duration of the project completion was 429 days.The duration of the project acceleration can be simulated using BIM 4D [6] [7] [8] .Table 4 and Figure 5 shows a BIM 4D simulation of the acceleration of the combination of overlapping and addition of working hours.

Figure 1 .
Figure 1.Research Flowchart Based on the calculation of the estimated project completion time using data up to week 40, the project will be completed in week 125.The project will experience a delay of 60 weeks, the project completion target of 65 weeks.-PrecedenceDiagram Method (PDM)Based on the project scheduling plan, scheduling alternatives can be made using the Precedence Diagram Method (PDM).With this method, the duration of the Early Start (ES), Latest Start (LS), Early Finish (EF), Late Finish (LF), and float can be determined.The critical scheduling path can be determined if the float value is 0 (zero).By determining the duration and dependence between works, a PDM diagram can be used to determine the duration of project completion and the critical path of the project.Figure2shows the scheduling diagram of the PDM.

Figure 3 .
Figure 3. Duration After Overlap Overlapping was performed by advancing the ceiling work on the roof floor (D11), the architectural floor work for the 7th floor to the roof floor (E9-E12), door and window work (F), and sanitary work (G) for 7 days (G).Miscellaneous jobs, PC-Sum jobs, and outside jobs were advanced for six weeks, resulting in a work duration of 168 workdays.Miscellaneous work can be advanced because it only depends on the completion of the structural work and metal doors, whereas the outside work only depends on the completion of architectural work on the ground floor.

Figure 4 .
Figure 4. Combination of Overlapping and Overtime Duration Overlapping was performed by advancing the ceiling work on the roof floor (D11), the architectural floor work for the 7th floor to the roof floor (E9-E12), door and window work (F), and sanitary work (G) for 7 days (G).Miscellaneous work (I) is carried out by start-start (SS) with sanitation work on the 1st floor (G4), and outdoor work (L) is carried out starting with sanitation work on the 2nd floor (G5).The duration of this alternative acceleration was 128 d.Project Crashing ComparisonThe fastest duration was 128 days obtained by combining the two acceleration alternatives.The additional two hours of working hours resulted in an increase in overtime paid for workers, but there was no increase in the number of workers.The resulting duration, with the addition of working hours, was also shorter.Table3presents a comparison of the monthly progress of the acceleration alternatives.

Table 1 .
. Earned Value calculations are based on data on planned and actual project schedules and the value of the project contract.Budgeted Cost of Work Schedule (BCWS) Performance

Table 2 .
Budgeted Cost for Work Performed

Table 3 .
Project Crashing Alternatives Comparison