Development of Work Breakdown Structure (WBS) Standard for Producing the Risk Based Structural Work Safety Plan Of Building

. A construction project is inseparable from a series of tasks in the form of activities. Activities that take place on a project can be disrupted due to various reasons, one of the causes of the disruption of project activities are accidents on construction projects. The risk of workplace accidents can be prevented with early identification and analysis of the potential danger that exist in every activity contained in the project’s WBS. The need for a standardized WBS in preventing the risk of workplace accidents is very important because it would present a risk assessment, impact and frequency arising from workplace accidents. The aim of this study is to develop a risk-based WBS standard particularly for structural work, by using a qualitative approach. The results of this research are WBS standard for building, source of potentially dangerous risk at structural work,and the development of safety plan using a risk-based WBS that has been standardized, as a form of prevention, reduction or even nullify the risk of workplace accidents (to obtain zero accidents) during construction project implementation.


Introduction
Construction industry is a very unique industry and more dangerous than other industries. The construction sites are constantly changing and temporary. Each construction sites involve of many sub contractors and they perform different types of work in close proximity to each other. The safety of workplace is an essential component of efficiency and productivity [6]. Construction workers, both staff and field workers are protected assets in order to work properly and productively until construction is completed without any workplace accident (zero accident). Workers need to be protected against the threat of accidents and health in work. Occupational safety measures are indispensable, both to workers and to corporations and to their production. Workers must follow safety-related regulations, in this case the OSH program, as the OSH program is closely related to the safety of the workers. A comprehensive OSH program and self-awareness of workers is essential to reduce the number of accidents [2].
Work accidents occurring on a project can actually be minimized, if activities on the project are well defined and each job can be placed at a level and level corresponding to a standard WBS, WBS constructing used during the project phase with a basic scope that has been identified. Initially, WBS was created with a restricted formation of scope, however WBS will be reviewed in addition to scope information developed or developed through complete project-to-project analysis. To complete the description of WBS and its application refers based on standard practical guidance according to the principle used so that will get high quality WBS [8], that is easy to determine the amount of activity in project.
Each defined WBS level brings WBS to a more complex level of activity, each activity that has been grouped in a standard WBS, will be easier to identify and mitigate its potential risks, so it is important to develop a standard Work Breakdown Structure (WBS) for the manufacture of safety based risk [11] to obtain output that can be used as a guideline for the implementation of construction.

Research Objectives
The objectives of this research are : 1.
To develop of building standardized work breakdown structure.

2.
To identify a potentially dangerous source of risk for structure work. 3.
To develop safety plan using a risk-based WBS that has been standardized.

Work Breakdown Structure
Work Breakdown Structure is a resultsoriented analysis of the work covered in a project called the total scope of the project. WBS is a fundamental document in project management as it provides the basis for planning and managing the schedules, costs and changes that occur. WBS serves as a deliverable oriented tool [4]. WBS formulation enables the project to be better in its definition, both in terms of resources and the estimated time required to complete the project to be further enhanced. However, it is important to note that WBS projects change over time, depending on the needs and constraints that the project is experiencing [10].
WBS forms the basis for planning, estimating, scheduling, monitoring, management and control of all project activities. The proposed methods for developing a deliverable are well defined and comprehensive, and the importance of increasing the probability of project success by ensuring that the best resources applied to the project [12]. A standardized WBS for the project is used to facilitate the preparation of project financing and a standardized WBS is also used to define project activities [1].
The best method of constructing WBS is the hierarchically displayed decomposition of the entire scope that the project team will undertake to complete the project objectives and produce the intended work output. In PMBOK 5th Edition, 2013 The planned work at the bottom of the WBS called work package. (deliverables) and not the activities.

Risk Management
Risk management is an important part of the decision-making process in construction project management, especially regarding integration, scope, time, cost, quality, human resources, communications and project procurement. Creating hierarchical risk management with RBS can improve future project prospects for identifying uncertainty and probabilities [13]. Risk is considered a negative term, but in the engineering construction industry in managing risks that arise is necessary and implemented in a structured way, knowledge of risk management, can nullify and minimize risks occurring in construction projects [7].

Performance Concepts of Occupational Safety and Health
Accidents occurring at construction sites may result in serious physical injuries and accidents such as people falling from altitudes and crashing material or equipment, the cause of occupational accidents may occur due to worker negligence and also undisciplined workers in the project environment, preventive measures against accidents should Implemented and implemented, so that workers and top management will raise awareness in preventing The workplace hazard handling strategy for construction may introduce potential hazards [5] , further investigation of frequent hazards and may result in safety plans in construction projects.
Safety Plan is a plan document containing practical safety that can assist companies in avoiding potential hazards and can control them in the best way when in these hazardous conditions, the importance of safety planning training during the planning, design and implementation phase of a project because it is able to minimize the risk of construction projects and Can improve workers' safety.

Methodology
This research is using qualitative approach to achieve formulation of standardised WBS for building construction. A survey and deep interview was also conducted by means of a structured questionnaire to contractor's experts who have had more than 20 years experiences in highrise building construction projects. Here in Figure 1. The Research Flow, there is a sequence of implementation of this study.

Questionnaire
In this study there are 4 (four) questionnaires to be made: questionnaires in stage I, II, questionnaires in stage III, questionnaire at stage IV, and questionnaire at stage V.
 Questionnaire in phase I is with expert form validation related to standard WBS level will be done variable validation by expert first. There is also the number of experts / experts are 3-5 people with a minimum of 10 years experiences in the field of high-rise construction and education S1. The validation process contains expert responses to agree / disagree that variable X is an activity in highrise building.  Questionnaires in phase II will be validated variables by experts in advance related risk factors that affect OSH. There is also the number of experts / experts are 3-5 people with a minimum of 10 years experiences in the field of high-rise construction and education S1.Proses validation contains expert responses upon agree / disagree that the variable X effect on the risk of high building construction OSH.  After obtained a valid X variable by expert / expert, conducted phase III that is pilot survey to know whether questionnaire made easy understood responder. Pilot survey is in the form of questionnaires to be distributed to 5-10 respondents. Here is an example of a questionnaire in stage III.  Questionnaires in stage IV are used to obtain the highest risk factors that affect the quality performance of high construction work. This questionnaire will be distributed to respondents who are / have worked in the process of building high-rise project and handling high building construction work with experience of at least 5 years. Here is an example of a stage IV questionnaire.  Questionnaire at stage V is expert validation aimed at soliciting expert responses related to the results of risk analysis while discussing the causes, preventive actions, impacts, and corrective actions of the highest risk on the process of implementing high-rise building construction work. Here is an example of a stage V questionnaire.

Respondent
A total of 35 respondents, the profile of respondent is defined in Table 1. Profile of Respondents as follows: WBS research variables the standard derived from the archive analysis of the WBS work package from 5 high construction project data from the structural work down to the top structure in the last 5 years there are 31 work packages, and based on expert validation of the potential risks that affect the performance of OSH 173 risk variables. Then the variable is defined in Table 2.
Research Variables as follows: Data collection was carried out using questionnaire survey to understand the perception of the practitioners to the risk factors. Once the probabilities and impacts are determined, the risk score can be calculated with following : Where R = risk factor, P = probability and I = impact. The probability and impact matrix or risk level matrix (Table 3 and Table 4) illustrates a risk rating assignment for risk factors. This analysis is done on the results of questionnaires given to respondents by using Likert measurement scale. The probability value of the occurrence of risk and the impact generated multiplied to produce a number that can be made ranking of risk factors. The risk matrix shows the combination of impact and probability as shown below:

Result and Discussion
The results of this study are as follows: 1.
To answer RQ 1 found WBS Building Standard Building in Figure 2.

WBS S tandard For High Rise Building
Level 1 is for the name of project, level 2 is work sections, preliminaries, struct ure, architecture, external work, interior, mechanical and electrical works. Level 3 is for area, level 4 are for sub work sections among others soil work, sub structure work, upper structure work, and roof work. Level 5 is for work package, level 6 is fo r activities, and level 7 is for resources.

2.
To answer RQ 2 there is a potentially hazardous source of risk and affect the performance of OSH on Structural Work in Table 5. Dominant Risk as follows:

Conclusion
Based on the results of testing and analysis that has been done then it can be concluded as follows: a.
Creating WBS building standards divided into 7 levels, Level 1: Project Name, Level 2: Work Section, Level 3: Zoning Area / Location, Level 4: Sub Work Section, Level 5: Work Packages, Level 6: Activity, and Level 7: Resources. WBS structural work standards can be established according to the classified level after collecting and analyzing data / archives based on BOQ and RKS projects and have been validated by related experts.

b.
Identify potentially hazardous sources of risk on structural work. There are 24 high risk risk event variables (X9, X15, X16, X27, X123, X124, X125, X135, X139, X149, X141, X161, X162, X164 and X167, X168, X169 , X170, X172, X173) are identified to be the dominant risk in every stage of the high rise building development process. Having obtained the risk event variable is also equipped with the risk response of each variable so that the potential danger can be prevented / mitigated.

c.
Preparation of safety plan by using risk based WBS standard is completed and developed according to document of safety planning / ROSHK Government Regulation PU 05 / PRT / M / 2014 at occupational safety planning section for building construction work which can be used either as assessment material of service provider auction process and also as guide for contractors in the preparation of safety planning.