LOGIC THE COST OBTAINED BY APPLYING PRECEDENCE DIAGRAM METHOD TOWARD THE TIME OPTIMIZATION ON BUILDING DEVELOPMENT PROJECTS

. The complexity of the project expands along with the progress of human civilization. The problems that appear will be more numerous and complicated. The role of project management is indispensable in order to address and prevent these problems, so that the cost,the quality and the time agreed upon can be realized. Cost and time relationship is not directly proportional, so it is necessary to determine the optimal time by optimum cost. Optimization is a best effort undertaken by planning various alternative methods of implementation, in order to obtain optimal timing of projects with optimum cost. Planning and scheduling are the backbone of the entire project, which is based on clear objectives. Microsoft Project as one of the scheduling software based on Precedence Diagram Method (PDM) provides many advantages, one of which scheduling can be done more quickly and thoroughly.In this research, it is created six alternative models as follows: ; In the alternative V , the project period was 96 days , at a cost of Rp2,019,623,191.13 ; In alternate VI , the project period was 89 days at a cost of Rp2,090,543,033.77. From the above calculation, then the result is interpolated in order to obtain the optimum time for the development project . The optimum time obtained is 120 calendar days, at a cost of Rp. 1,884,638,013.61.


INTRODUCTION 1.1 Background
Nowadays construction projects have grown increasingly complex and complicated. No doubt the problems faced will be more and more difficult, so it takes the role of project management to the overall stages of the project, in order to minimize the problems posed and the three project targets that are appropriate cost, time, and quality can be met.
Planning is the overall backbone of the project, and it must be realistically structured. Realistic planning is expected to guarantee the completion time of a construction project in accordance with the plan. Because it is not guaranteed that the timing of fast project implementation requires minimal cost, and vice versa. In other words, the time and cost ratio of the project is not directly proportional. Based on this it is necessary to take into account how to get the most optimum time planning with the least cost. Optimization is defined as a process of deciphering the duration of the project to obtain optimal completion time and reasonable cost, using various alternative methods of implementation, such as: heavy equipment use, increase in the number of workers, additional hours of work and others, tailored to the field conditions and needs.
To plan when a project should be implemented, a scheduling is required. With the scheduling, the problem of delay in completion of the project can be reduced and there will be an increase on the timeliness of completion, so the budget can be saved without any additional costs that are not really needed. There are two kinds of project scheduling techniques that are often used today. Networking is the best scheduling technique right now because it can solve the problems of the only scheduling technique (Gantt-Chart). In its development there are various kinds of networking methods such as CPM, GERT, PERT, PDM etc.
PDM (Precedence Diagram Method) is a scheduling tool that focuses on the equilibrium issue between project cost and time of completion. The PDM diagram does not require dummy / fictitious activity and additional sections to indicate overlap. Based on the above description, the authors are interested to raise the topic of Project Development Cost Building Using PDM (Precedence Diagram Method) ".

Research Problems
Based on the above description of the background, the issues to be raised in this research are as follows: a. What is the shape of network (network) with PDM method in Building Construction project? b. How much is the total cost of the Denpasar Building Development project with optimum duration?

Research Objectives and Benefits
The purpose of this study are as follows: a. To determine the network on the Development project. b. To analyze the cost estimates for a Building Development project whose completion time is accelerated. The benefits of this research are as follows: a. To complete the project on time so that its budget use becomes efficient and there is no waste. b. To apply the sciences gained in lectures to solve existing problems in the project. c. To be able to provide input to the agencies involved in construction work projects in order to produce construction products that are timely in progress, precise and cost-effective methods.

Research Scope
The limitations of the research problems are as follows: a. The research was conducted on Building Construction project. b. Project scheduling analysis using PDM method. c. For alternative optimization of time on the addition of manpower, available resources are considered unlimited. d. For alternative optimization of time on the addition of working hours (overtime), used normal labor productivity. e. Normal working hours in one day is 8 hours ie at 08.00 until 12.00, then at 13:00 until 17:00. f. There is no volume change in each job.

Literature Review a. Project
The construction project is a series of activities that are only implemented once and generally takes a short period of time. In the series of activities, there is a process of processing project resources into a result of activities in the form of buildings. In addition, the construction project has 3 (three) characteristics: unique, requires resources (money, machinery, methods, and materials), and requires organization [3].

b. Project Management
H. Kerzner states that project management is planning, organizing, leading, and controlling company resources to achieve short-term goals that have been determined [10].
Project management is the implementation of systematic management functions in a project using limited resources, effectively and efficiently to achieve the project objectives more optimally.

c. Planning
Planning is a process of trying to lay the groundwork of goals and objectives including setting up all resources to achieve them. Planning provides guidance for the implementation of resource allocation to carry out activities (Imam Suharto, 1997). Broadly speaking, planning serves to lay the foundation of project objectives, namely scheduling, budget and quality.

d. Scheduling
Scheduling is the elaboration of project planning into a sequence of steps on the implementation of work on a time scale to achieve the target. Scheduling determines when activities are initiated, deferred and resolved, so that the financing and use of resources will be timed according to predetermined needs [8]. Planning a project schedule can be done well and realistically, if in the planning process schedule is done in stages with the steps as follows: 1) Making WBS 2) Determining the implementation method 3) Determining duration 4) Determining relation between activities 5) Looking back to whether the duration and sequence of activities are reasonable and workable in the field There are a variety of project scheduling methods to plan graphically from the construction activities, but only two methods are commonly used; they are gantt charts and networking (CPM, PERT, PDM, GERT, etc.).
Here is the systematizing of scheduling on networking methods: Picture 1 Network Scheduling Systematic e. PDM PDM was developed in the 1960s by the US Navy in collaboration with Professor Dr. John Fondahl of Stanford University to develop a CPM calculation method that will also solve the use of "Dummy" dependencies. Dr. Fondahl reversed the AOA diagram method to the traditional AON method known as the precedence method. The Fondahl method then became an option for the critical path method (Uher, 1996). Although the approach is substantially different between CPM and PDM, the results are the same (O'Brien and Plotnit, 1999).
The advantage of Precedence Diagram Method (PDM) compared to CPM is that PDM does not require fictitious / dummy activities so the networking becomes simpler [5]. This is because different overlapping relationships can be created without increasing the number of activities.

f. Optimization
Optimization is a process done in the best way in a job to gain profit without having to reduce the quality of work. There are several alternatives to optimize the time and cost of project completion that can be done, namely: 1) Use of Heavy Equipment.
2) Replacement or Repair of Working Methods.
3) The addition of Labor. 4) Implementation of Working Hours (Overtime). 5) Work shift g. Implementation method Method of work implementation represents the elaboration of procedure and technique of the implementation. The use of appropriate, practical, fast and secure methods is helpful in the completion of work on a construction project. So precise quality, exact cost / quantity and timely as determined, can be achieved. The method of implementation has an enormous impact on the direct costs of a project. The aspects that affect the method of job implementation include: 1) Implementation method is a technological innovation aspect required by the terms of the contract 2) Selected implementation methods must be tailored to the various environmental conditions of the project.
3) The method of implementation is affected by the availability of resources.

RESEARCH METHOD 2.1 Flow Chart
In conducting a research, obviously, a research method plan should be developed so that the research can run systematically and directed. Here is the systematic research in the form of flow chart.

The Time of Data Collection
The research execution time is 10 weeks.

Research Location
For the location of this research, it was taken the building project.

Data Analysis a. Identification of the Project Scope
Identification of project scope is the first step in networking. Identification of the project scope aims to know the activities that exist within a project and grouped into work groups. Arrangement of project scope is based on the sequence of job execution which is adjusted to sequence of work on Time Schedule that already exists.

b. Calculation of Project Cost
In this study, it is assumed that, costs other than the overhead cost are in the scope of the direct costs. Based on the journal Asri Nurdiana (2015) which is related to indirect cost analysis, it is mentioned that overhead cost is 5% of the budget plan, so direct cost can be formulated as follows: Rp. 25,500

d. Alternative Planning of Optimization
The alternative planning of the optimization on the building construction project consists of six alternatives. The detail of each alternative is as follows: 1) There are six alternatives consisting of one plan alternative (existing) and five new alternatives.
2) Five from three alternatives are planned by deciphering the duration and changing the dependency relationship of each alternative work item.
3) The remaining two alternatives are done by addition of working hours (overtime).

e. Deciding the Work Item Duration
In deciding the duration for each work item in each alternative, trial and error method is applied. This method is chosen because of the relation between resources and duration which use fixed work relation. Things to consider in determining duration are overhead, critical paths, dependency relationships and project densities.

f. Flatten the Resources
Resource leveling is important to determine the maximum (peak) effort required in a given period of time. In one period of course there is not only one work item but other work items being carried out in that period. Maximum requirements obtained do not reflect the needs of the unit as a whole, because between the efforts of one period to another is not the same. So the calculation of the need for the next work unit is used with the calculation of the average. This calculation will produce a straight line.

g. Calculating Overtime
In this study, overtime calculations will be planned using Microsoft Project help. The required data is the overtime wage of each labor which is calculated per unit hour. Overtime wages are determined based on Ministerial Decree No. 102/2004. In the regulation, overtime pay is calculated as follows: 3 hours of overtime = 1.5 x normal wages 4 hours overtime = 2 x normal wages In the above calculations can be drawn conclusions for one hour of overtime requires a fee of 0.5 x normal wage.

h. The Calculation Results
To find out the most optimal cost and time, it is planned six alternative models. Once it is processed with Microsoft Project (see the attachment), then the results obtained are shown the following table:

Discussion
In this research, six alternative models are created. Each alternative is described as follows: a. In alternative I, it is obtained project time for 256 days, at a cost of Rp2,190,234,913.43; b. In alternative II, it is obtained project time for 150 days, at a cost of Rp1,903,674,873.6; c. In alternative III, it is obtained project time for 102 days, at a cost of Rp1,873,215,897.61; d. In alternative IV, it is obtained time project for 99 days, at a cost of Rp1,895,159,526.12; e. In alternative V, it is obtained time project for 96 days, at a cost of Rp2,019,623,191.13; f. In alternative VI, it is obtained time project for 89 days, at a cost of Rp2,090,543,033.77.
From the above calculation, the graph shows that the optimal time is 120 calendar days. So in order to know how much cost incurred, interpolation is applied as follows: Based on the above interpolation result, it can be concluded that the optimal time in Building Project is 120 calendar days with optimum cost of Rp. 1,884,638,013.61. The percentage of cost efficiency and project time of the plan are as follows: Efficiency of Project Time From the above calculation results, it is known from the time of optimization that there is efficiency / time savings of 30% of the time plan or 30 calendar days. Efficiency of Project Cost