Cost and Time Evaluation using The Critical Path Methode (Cpm)

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Cost and Time Evaluation using The Critical Path Methode (Cpm)

(Case Study of Hanging Bridge in Kab X, Jawa Timur)

Rizky NovitaSari, H. Fredy Kurniawan

Faculty of Engineering Civil Engineering Study Program Narotama University Surabaya, Jl. Arif Rahman Hakim 51 Surabaya

[email protected]

Abstract

A project is a temporary activity that takes place in a limited period of time, with a specific allocation of resources, and is intended to carry out tasks whose objectives are clearly outlined. This means that each project has a deadline that must be completed (deadline).This research includes research using Ms. Projects as data management used in data management are cost budget plans, work agreement and job specifications, research locations are in suspension bridges in X Regency, East Java. Data analysis uses work shift analysis and methodsCritical Path Method(CPM). The suspension bridge construction project X is planned to be completed within a period of 3 months starting on October 1, 2018 and completed on December 31, 2018 with a planned work cost budget of Rp. 4,689,282,000. From the analysis by adding the CPM method on the critical path the cost of accelerating the time needed to complete the project is 54 work calendars or 1.95% faster than the normal duration of 105 work calendars with a total normal cost of Rp. 4,689,282,000 then the cost decreased to Rp. 4,595,777,563 or decreased by 1,020%.

Keywords:

Critical Path Method (CPM), cost and time evaluation

1. Introduction

1.1. Research Background

A project is a temporary activity that takes place in a limited period of time, with a specific allocation of resources, and is intended to carry out tasks whose objectives are clearly outlined. This means that each project has a deadline that must be completed (deadline). The project is said to be successful or successful if the cost of the work or its implementation is not more than budgeted, the working time does not exceed the planned time in the time schedule or contract and the specifications are in accordance with the plan or design.

Delay in project work can be overcome by accelerating the implementation so that the project can be completed according to the planned target, but must also pay attention to the cost factors because the cost, quality and time are interrelated so that they influence one another. One way to speed up the project implementation time which has been delayed including increasing work time with available labor (overtime work) adding working hours can be done by adding 1 hour, 2 hours, 3 hours, 4 hours in addition to the desired addition time but with the addition of this working hour is automatic costs for project work will also increase (Priyo and Risa Anggriani Paridi, 2018).

The case study used for the analysis of project time acceleration is the construction of the Hanging Bridge Construction Project in District X, East Java. This development process takes 92 calendar days on structural work. Although there were delays in the project when working on the project 13 working days so that the total implementation of the construction project of the Construction of the Hanging Bridge in District X, East Java was 105 working days, so further research was needed on whether the construction management method could be applied to further save the implementation time. not too long. detailed time division that is adjusted for each section of work, from preparatory work to final work. The detailed plan schedule acts as a master framework to be elaborated in more detail in the form of schedules, material procurement, tools and labor, billing, and achievement payment services. In this study, the impact of the duration of the Hanging Bridge Construction Project in X X East Java will be analyzed (Caesaron1 and Andrey Thio, 2015).

In order to be more focused on the existing problems, this research will provide the following problem constraints:

1. When using CPM (Critical Path Method) method, what kind of work should not be late on the Construction of a Suspension Bridge in District X, East Java?

2. What is the cost and time efficiency that will be obtained if the project uses the CPM (Critical Path Method) Method?

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35 2.1. Literature Review

CPM method (Critical Path Method) construction management that can be used in the calculation of time by determining the critical path that must be prioritized in the work of the project, in implementing the project can be a calculation in the time to be implemented so as to minimize the time that will be able to reduce the burden in cost According to (Critical Path Method) is a method using arrow diagrams in determining the critical path so that it is also referred to as a critical path diagram.

In the CPM method there are two estimated time and costs for each activity that gets in the network. Both of these estimates are estimates of completion time and costs that are normal (normal estomate) and estimates of completion time and costs that are accelerated (crash estimate). In determining the estimated completion time the term critical path will be known, a path that has a series of activities with the longest total amount of time and a quick project completion time. So that it can be said that the critical path contains the initial crisis activities to the end of the path. A manager must be able to identify the critical path well, because in this path there are activities that if the implementation is late it will result in the delay of the entire project.

One strategy to speed up project completion times is to increase the working hours (overtime) of workers. Addition of working hours (overtime) is very often done because it can empower existing resources in the field and simply by increasing the cost incurred by the contractor. Usually the normal working time is 7 hours (starts at 8:00 and finishes at 16.00 with one hour of rest), then overtime is done after normal working hours are finished

2. Methodology

In this research, there are stages that are carried out, namely the existence of interviews, observations, literature study literature studies, data collection, and data management using CPM method by determining the critical path and calculating the acceleration by shift work.

Furthermore, determine the time of acceleration and calculate additional costs for the acceleration of activities with the alternative of adding hours of work (overtime), tapping the work network,Speed up project completion time by prioritizing critical activities that have the lowest cost slope. If acceleration efforts are made on activities that are not on the critical path, then the overall completion time will not be reduced

3. Research Result

Accelerating using shift system working hours on critical activities, the direct costs will increase while indirect costs decrease. In this study, the amount of overhead and profit is taken 15% from the RAB. (based on Perpres 70/2012 regarding service provider profits is 0-15%). In Perpres 54/2010 as amended by Perpres 70/2012, paragraphs on price adjustments to article 92 paragraph 3 that in price adjustments to determine fixed coefficients consisting of profits and overhead if the offer does not include the magnitude of the profit and overhead components, the fixed coefficient = 0, 15 (15%). This is the meaning in calculating the profit at the offer price offered by the provider. Unless the provider does not list, then a conclusion of 15% is taken.

Unknown = RAB Value = Rp. 4,689,282,000 Overhead and profit = total project cost x 15%

= Rp. 4,689,282,000 x 15%

= Rp. 703,392,300

10% profit = Rp. 4,689,282,000 x 10%

= Rp. 468,928,200

Overhead 5% = Rp. 4,689,282,000 x 5%

= Rp. 2,344,641,000

The amount of direct and indirect costs based on PUPR Regulation 28-2016

= total cost - overhead and profit

= Rp. 4,689,282,000 - Rp. 703,392,300

= Rp. 3,985,889,700 Material costs (82% xdirect cost) = 82% x Rp. 3,985,889,700

= Rp. 3,268,429,554 Wage fee (18% x direct cost) = 18% x Rp. 3,985,889,700

= Rp. 717,460,146

Wage fee per day = Rp. 3,985,889,700/ 105

= Rp. 37,960,854

Direct cost = Rp. 3,268,429,554 + Rp. 717,460,146

= Rp. 3,985,889,700

Indirect costs = Rp. 4,689,282,000 - Rp. 3,985,889,700

= Rp. 703,392,300 Normal project duration = 105 days

Overhead per day = Rp. 2,344,641,000 / 105

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36

= Rp. 2,232,991

Project costs under normal conditions = direct costs + indirect costs Direct costs include: material costs = Rp. 3,268,429,554

Wage fee= Rp. 717,460,146 Indirect costs: overhead = Rp. 2,344,641,000

Profit = Rp. 468,928,200 +

Total project costs under normal conditions = Rp.4,689,282,000

Project costs under conditions of acceleration

Project duration after acceleration = 105 - 51 = 55 days

Direct cost = Rp. 3,985,889,700 + Rp. 27,077,100

= Rp. 4,012,966,800 Indirect costs include:

Overhead (51 x Rp. 2,232,991) = Rp. 113,882,541

Profit = Rp. 468,928,200 +

Total indirect costs = Rp. 582,810,763

Total project cost after crashing = direct costs + indirect costs

= Rp. 4,012,966,800 + Rp. 582,810,763

= Rp. 4,595,777,563

Following below is a summary table of the comparison of duration and costs between normal projects and projects that are carried out at the same time

Table 1. Recapitulation Table Comparison of Project Duration and Costs Project Time Duration Total cost

Normal 105 4,689,282,000

CPM 54 4,595,777,563

Difference 55 93,504,437

From the results of the calculation analysis as above, the X suspension bridge construction project is planned to be completed within a period of 3 weeks starting on October 1, 2018 and completed on December 31, 2018 with a planned work cost budget of Rp. 4,689,282,000. but there are work delays so that 105 work duration, accelerating the duration of the project by adding CPM methods on the critical path will add to the project's direct costs and will reduce the project's indirect costs. In this study, the amount of overhead and profit is taken at 15% of the Budget Plan, so we will get overhead costs per day.

From the cost analysis the acceleration of time needed to complete the project is 54 work calendars or 1.95% faster than the normal duration of 105 work calendars with a total normal cost of Rp. 4,689,282,000 then the cost decreased to Rp. 4,595,777,563 or decreased by 1,020%. The results of this analysis show that increasing the hours worked causes the total project cost to fall.

From the above analysis, it can be seen that the project experienced a crashing that had a duration of 105 days to 54 days making direct costs and total costs have increased. Whereas indirect costs decreased.

Based on the discussion above, several results were obtained. The first is the advantages and disadvantages of using additional working hours.

4. Conclussion and Suggestion

4.1. Conclussion

There is some work that becomes a critical path that must be done, including excavation block anchor with the duration of acceleration time 12HK from the normal time of work 28 HK, reinforced concrete work with acceleration time duration of 5 HK from the normal time of work 28 HK, work formwork abutment with duration the acceleration time is 6 HK from the normal time of work 14 HK, the work of installing a suspension bridge with the acceleration time duration of 28 HK from the normal time of work is 35 HK. So there is a difference in the work of 54HK by analysis using MS. Project 2013with a planned work cost budget of Rp.

4,689,282,000. From the analysis by adding the CPM method on the critical path the cost of accelerating the time needed to complete the project is 54 work calendars or 1.95% faster than the normal duration of 105 work calendars with a total normal cost of Rp. 4,689,282,000 then the cost decreased to Rp. 4,595,777,563 or decreased by 1,020%. The results of this analysis show that increasing the hours worked causes the total project cost to fall

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37 4.2. Suggestion

So that a project can go according to plan and on schedule, tracking should be carried out for each work, especially for work that is on a critical path. Further research can be added to other supporting factors related to the handling of the remaining material as an evaluation material and also about the placement of more effective disposal of waste material.

References

Caesaron1, D. and Andrey Thio (2015) ‘Analisa Penjadwalan Waktu Dengan Metode Jalur Kritis Dan Pert Pada Proyek Pembangunan Ruko (Jl. Pasar Lama No.20, Glodok)’, Journal of Industrial Engineering &

Management Systems, 8(2), pp. 1–24.

Priyo, M. and Risa Anggriani Paridi, M. (2018) ‘Studi Optimasi Waktu dan Biaya dengan Metode Time Cost Trade Off pada Proyek Konstruksi Pembangunan Gedung Olah Raga (Gor)’, Semesta Teknika, 21(1). doi:

10.18196/st.211213.