Disruptions Control on Precast Concrete Supply Chain in Construction Projects

Agility amid uncertain circumstances is key to all-across sustainable industries. The construction industry depends heavily on projects as potent drivers to their operational activities regardless of projects' hardwired constraints—shipment, resistance to risks— to affect Key Performance Indicator (KPI). PT ABX, as one of the Indonesian precast-concrete manufactures, is the object of this research aiming to find precautionary strategies for controlling disruptions to the concrete supply chain in construction projects. It considers such supply-chain disruptions, and therefore, the two-layered House of Risk (HOR) model to subsume risks identification, and risks control is applicable for minimizing possible disruptions. It finds risk events, some of which are classified as critical risk events and preventive actions against risks. The findings contribute to a working framework for managers responsible for applying effective strategies for preventing such disruptions.


I. INTRODUCTION 1
Intense competition over product innovation, production, and performance in the precast concrete industry leaves the players bruised. The supply chain within management concept refers to the inseparable production process, distribution, and marketing as consumers are exposed to their-desired products available in markets. At the same time, producers are capable of producing products amounts, quality, propermarket location are subject to preliminary plan (Saptana et al., 2016). While working towards fulfilling consumers' expectations, projects should be quite agile in managing possible-yet-common risks to impact preliminary-planned aims (PMI, 2008). Projects apply risk management in order to unknown risks amid the ongoing projects, and therefore, cost and time efficiency, as well as quality properness, are achievable (Nurlela and Suprapto, 2014).
Any activities inseparable from supply-chain management bound to risks as Handayani (2016) theorizes uncertainties (i.e., demand, capacities, time shipment, cutting-edge technology, market changes, intense competition, political upheaval, and government regulations) embedded in the supply chain are initial agents to spark risks. One risk agent commonly has domino effects of sparking other risks, and PT ABX precast supply chain is also exposed to domino-effect risks. Marie et al. (2015) have conducted research of a model of disruptions control applied in processed bread makers and beef-sausages makers. That model anticipates and prevents any disruptions from supplying, demand, internal production system and varies in sub-models it has (i.e., preventive actions against disruptions, advanced policies of controlling disruptions, and inventory tolerance. The sub-model of preventive actions against disruptions recommends rulebased mechanisms to control disruptions; the sub-model of policies of controlling disruptions generates prevailing regulations against disruptions, and the sub-model of inventory tolerance by means of average disruptions produce safety stock value. Each of the disruptions and preventions against them is recorded in a certain database whose names are input and locked with keywords. Should any disruptions occur, proper preventive actions for controlling that disruptions can be taken into effect by unlocking keywords. According to each of the processed food industries, the database on a periodical basis is subject to analysis to formulate new policies better. The sub-model of inventory tolerance update safety stocks to keep their adequate amount, and therefore, methods for determining safety stocks vary. Marie (2014) has proposed a safety stock, which is way more adaptive to periodical adjustment and production disruptions (i.e., supply, demand, internal production system).  has conducted research on a precautionary model against disruptions applied in automotive spare-parts manufacturers exposed to possible risks. The research finds a precautionary sub-model against disruptions (i.e., disruption risk levels, status to measure necessary management, measures for controlling disruptions, and safety stock calculation).
Disruptions to the production system in the heavy equipment makers have been mapped with respect to industrial volatility. Therefore, a proposal to determine dynamic safety inventories carefully considers the mapped disruptions (Marie et al., 2019).
Related to research for the management of supply chain disruptions conducted at an automotive battery company, by defining disruption as an event that hampers KPIs' achievement, a lean manufacturing approach is used. The research objective is to identify waste and cause of waste and propose an improvement to eliminate waste in the PT XYZ supply chain to reduce lead time and achieve the delivery target to improve company performance with the Lean Supply Chain approach. Based on Value Stream Mapping and analysis of waste, the researcher proposed improvements and decreased manufacturing lead time and the increased process cycle efficiency .
Companies to manage construction projects based on their supply chain uncertainty have the following characteristics (i.e., high level of volatility demand, high level of lead-time supply, moderate process uncertainty, high complexity). Thus, it is recommended that they adopt flexible strategies with low safety stock, high safety lead time, low-capacity buffer, high supplier backup, moderate component commonality, high postponement, and high sub-contract outsourcing. (Angkiriwang et al., 2014).
PT ABX established in 2014, is a subsidiary of PT AK (Persero) Tbk and envisions to be the Indonesian third-largest precast concrete supplier. To ensure a smooth supply of precast concrete, it establishes two plants located in Sadang-Purwakarta and Mojokerto. These two plants supply precast concrete demands by PT AK Tbk (Group) and the domestic market.
The Company accredited with ISO 9001:2015 quality management system proves its performance of producing quality products and providing the best services to its customers. Figure 1 shows PT ABX's supply chain.
The initial mapping of PT ABX's supply chain explains problems in precast concrete supplied for construction projects. Thus, to ensure an undisturbed supply chain, PT ABX, running its business, is equipped with two-typed plants: permanent and temporary. Its permanent plants supply generally-marketed precast concrete, while temporary plants whose locations are impermanent and near the ongoing projects specifically supply precast concrete for certain construction projects. The impermanent locations require properly-planned strategies for managing disruptions: uncertain supply, internal and operational issues to hamper the production system. A proper precautionary system against possible disruptions is mandatory. For example, companies -PT ABX -by means of projects Key Performance Indicators (i.e., budget, schedule, and quality) can fulfill customers' expectancy. Precise qualitative and quantitative risk measures are prerequisites and complementary. The qualitative method measures "analysis accuracy" in terms of risk descriptions, risk agents, plausible occurrence, impacts of risks on supply-chain performance. In contrast, the quantitative method calculates probable events and their impacts on supply-chain risks (Waters, 2007).
This research aims to find proposed strategies for controlling disruptions to the precast supply chain in construction projects, for it also considers disruptions as risks to such a supply chain. Thus, quantitative and qualitative methods are measurements applied to control supply-chain disruptions. The qualitative method measures risks level, while a qualitative method is necessary for in-depth analysis and provides recommended solutions for risks.
House of Risk (HOR) model is applicable for identifying and measuring supply-chain risks in construction companies as two widely-used tools-Failure Mode & Effect Analysis (FMEA) and House of Quality (HOQ) of Quality Function Deployment-are the basis for its developed framework (Millaty et al., 2014). Its developed framework generally is categorized into two phases: risk identification and risk management. Risk identification involves comprehensive identifications and measurement of risk events and risk agents, while risk management subsumes the first-phase measurement of managing and mitigating risk agents (Kristanto et al., 2014).
Several research pieces have applied the HOR model to identify and prevent possible risks, as Pujawan et al. (2009) developed HOR management risks of fertilizer companies' supply chain. Then, Cahyani et al. (2016) carried out HOR's implemented study in the heavy shipbuilding industry. Meanwhile, Kristanto et al. (2014) continued to apply HOR for risk mitigation in the leather-made shoe industry's supply chain. Ma et al. (2018) developed a fuzzy HOR assessment method based on severity and frequency level applied for supply-chain risks in Hong Kong-based electric equipment producers. Additionally, Dewi et al. (2015) used HOR to compared risks arising from 3 surrounding veil industries in order to develop new-designed veils. Any research on risks or disruptions to the precast supply chain has never been conducted. Therefore, this research analyzes a model for controlling disruptions or risks to the precast supply chain applied in the construction project. This research applies HOR to identify varied risks and analyzes precautions, which also utilizes a lean manufacturing approach against possible risks.

II. RESEARCH METHOD
Flowchart diagram of research methodology is described in Figure 2. This research collects data provided by PT ABX as a precast supplier for construction projects and this research object. The collected data consists of corporate data, business process data, supply-chain network data (i.e., customers order, checking finished inventories, data storage, raw-material and supporting-material procurement process, manufacturing, finished precast concrete, delivery to customers complete with a schedule for each of activity), suppliers and customers' data.
Customer data varies from value, customer demands, managing-construction-project KPI to critical quality of precast concrete products. Meanwhile, manufacturing data varies from Figure 2. Flowchart of research methodology production layout, working machinery used in production, production operator, production activities, production planning, managing, inventories, material handling, and material receiving and storage in warehouses. Another type of collected data is documentation of recorded risks and disruptions to supply-chain activities. All kinds of data are collected through structured interviews with experts working for vocal and I-tier companies and documentation of visiting precast-concrete producers and construction projects in the Jakarta greater area. This research applies a HOR model to process the collected data further so that disruptions and risks to the precast concrete supply chain are found.
Based on the results of filling out the questionnaire, which has been strengthened by the results of interviews with supply chain actors regarding the disruptions that occur in each supply chain, disruptions mapping and control actions for each disruption were carried out. This mapping will help supply chain actors identify disruptions control actions to anticipate the disruptions to reduce the impact of disruptions. Next, the results of disruptions mapping and analysis will be used in data processing for HOR creating. In HOR-1 data processing, the disruption becomes a risk agent, while disruption control action becomes a risk event. Next, we calculate the Aggregate Risk Potential (ARP) level by multiply the severity, occurrence, and correlation between risk events and agents. The highest ARP level represents risk potential to have the most destructive impacts on companies, and therefore, be on top-managed priority. Furthermore, the HOR-2 data processing is carried out by utilizing the data from the HOR-1 calculation. HOR-2 determines the correlation value between risk prevention and risk agents as well as the calculation of Total Effectiveness (TEk), Degree of Difficulty (Dk), Effectiveness to Difficulty (ETDk) in order to figure out the priority of prevention action measures.

Supply-Chain Activities
Owners of construction projects through the marketing division give orders to PT ABX. The marketing division will then process orders so that receipts of prices or product specifications will be resentful to the owners. After accomplishing the deal, a selling agreement contract is drafted as the marketing team coordinates with the production and engineering team to discuss orders from construction companies, then issues a license to produce precast concrete and calculate raw materials and time allocation for production. The raw-material preparation requires 14 days to subsume rawmaterial order to raw-material delivery to processing plants. The product processing requires a sample taken from 7 pcs of finished Figure 3. Precast concrete supply-chain activities precast concrete to undergo 7 days, 14 days, and 28 days of a preliminary test to figure out their high tensile strength. The production team will update information relating to products, number of produced products, defective or perfect and finished products. Figure 3 describes precast concrete supply-chain activities carried out by PT ABX.

Preventive actions against Disruption
Interviewees with experience and knowledge of disruption and prevention reveal recorded documentation of precast concrete constraints for construction projects. Such supply chain is integrated with suppliers, precast, and construction projects, where Table 1, Table 2, and   Table 3 depict constraints in each chain.
Preventive actions are precautions against potential disruptions and provide appropriate control when disruptions hampered the supply chain. The mapping of disruptions and necessary control is recorded in a system to be corporate smartbooks.
House of Risk-1 (HOR-1) HOR-1 identifies to-be-managed risks. The required data varies from risk event, risk trigger, severity, occurrence, and a correlation between risks and risks.
Risk event identifies potential risk event using supply-chain operation reference consisting of Plan, Source, Make, Deliver, Return (SCOR) to    Table 1 describes the mapping of the precast concrete supply chain using the SCOR model. Severity displays the level of severity caused by any risk event on companies. The severity assessment of risk events is performed by direct questions and answers with production supervisors. The severity level falls on a scale from 1 to 5, as 5 represents the extreme impacts. Table  2 describes the level of risk events.
Risk agent identifies a risk agent by means of direct questions and answers with production supervisors.
Occurrence elucidates the possible occurrence frequency of risk triggers. Measurement of an event caused by a risk agent is performed.
Correlation between risk events and agents. If risk agents cause plausible risks, it implies a strong correlation and is scored 9, while moderate and weak correlation is scored 3 and 1, respectively.
Aggregate Risk Potential (ARP) level functions to put priority over managed risks. ARP level comes from the multiplication of severity, occurrence, and a correlation between risk events and agents. ARP levels are put in order from the biggest to the smallest. The highest ARP level  represents risk potential to have the most destructive impacts on companies, and therefore, be on top-managed priority. Appendix 1 describes the table of ARP level. Risk agent to have the biggest ARP level shown by Pareto diagram is on the top-mitigation priority and put in HOR-2. The following figure is the list of to-be-mitigated risk agents based on the Pareto diagram-ranked ARP level. Figure 4 portrays the Pareto diagram. The Pareto diagram shows the top-priority-managed-and-mitigated risk agents to determine the proper precautions.

House of Risk-2 (HOR-2).
HOR-2 finds effective precautionary measures in order to lessen plausible risk agents. HOR-2 determines the correlation value between risk prevention and risk agents as well as the calculation of Total Effectiveness (TEk), Degree of Difficulty (Dk), Effectiveness to Difficulty (ETDk) in order to figure out the priority of prevention action measures. Prevention actions suggested are also based on the lean manufacturing approach and using lean tools. Figure 5 displays HOR-2. Table 7 shows each of the prevention action's priorities based on the value of the effectivity ratio.
Proposed prevention action is Poka-Yoke method applied in Quality Control process, availability of product specification data, QC SOP (inspection and rework) and smartbooks quickly access by production operator. Production or working activities hardwired with erroneous factors-human error, flaw materials, improper methods, misinformation-to cause defects, and the further and in-depth analysis of erroneous factor will lead to the fact that each of the defects are made by humans (Syarifuddin and Sofyan, 2018). Poka-Yoke method is applied by creating supporting tools for controlling the working process so that checking and monitoring the quality control of precast concrete runs smoothly. These supporting tools must measure the suitability of dimensions and measure the visual condition of precast concrete from the surface to the inside. Company constraints in providing these supportive tools are in terms of cost. Companies must provide more budget, but if compared to the ease of the process and the results obtained, the provision of supporting tools for process control is still more effective and efficient. Meanwhile, smartbooks mean applications to explain production and operators complete with their job descriptions comprehensively. It is expected that each of the operators using smartbooks can acquire information at hand so that coordination with related parties gets easier. The company itself can make this application; the features contained in the application can be tailored to the company's needs. Before running by all users, there must still be special training for users to understand and not experience difficulties operating the application. The smartbook application can be ordered from the provider that provides this application for a broader scope.
The precast concrete industry's responsibility is not only in the production process but also includes product delivery. Therefore, adequate transportation facilities are needed and can guarantee that the product being moved remains safe. Precast concrete, which consists of several types, has a weight of around 25 tons. Transportation facilities used to deliver products are trucks, and the project's product delivery is carried out by road only. The company needs to calculate the optimal number of transportation suggestions that must be provided and adjust the provision of transportation facilities to the project that is being worked on.
Moreover, the MRP system is recommended to be complete with computerized safety stock; temporary suppliers are available to supply alternative materials, and safety stocks of rare material are adequate. MRP-computerized system initially was developed in the American A3 ARPj %Cummulative Production and Inventory System Society) APICS at the time of professional program development.
It gains popularity in industries applying computerized inventory design and management as it identifies inventory items correlation so that more efficient inventory management determines precise and proper material needs (Yuliana and Octavia, 2001). MRP-computerized system whose operation is faster than the manual ones requires intensive operational training given to its operators to prove boon for the companies applying it. As business partners, suppliers play a crucial role in providing adequate material demand because they-in the supply chain concept-are significant for companies' sustainable production (Ramayanti & Ulum, 2017). Companies should have alternative suppliers to keep adequate inventories of rare materials in check. Another to having alternative suppliers, safety stock of rare materials is a precaution against possible project disruptions.
In addition, inventories review based on ABC classification, updated records of material stock data, evaluation of weekly PR, SOP for machinery use, updated records of machinery use, and routine preventive maintenance is also as significant as previously-elucidated prevention actions. Periodic monitoring of raw-material orders and alternative suppliers' availability to supply required material in less than two weeks minimize any possible disruptions with respect to postponed material supply. In relation to risk agents in the form of technical troubles in plants to cause disruptions can be mitigated by routine checking of equipment and facilities used in operational activities, the availability of diesel generator, coordination with internal and external parties, management of warehouse stock data, updated record of inventories, and monitoring of factual and natural circumstances.

IV. CONCLUSION
The mapping of disruptions in precast supplied for construction projects reveals precautionary models for controlling disruptions are crucial in order to apply necessary control on disruption and maintain smooth operational activities in integrated parts of the supply chain. Key strategies for managing disruption to the precast concrete supply chain are Poka-Yoke method for QC process, availability of product specification data, QC SOP (inspection and rework), "smartbooks" accessible to production operators, MRP-computerized system integrated with safety stock, alternative interim suppliers, substitute for a rare material core to production. The strategies should be useful to mitigate possible disruptions. Precautionary control on disruptions and HOR model prevent and minimize any possible disruptions; and therefore, KPI of the precast supply chain for construction projects and customers' values are successfully achievable.

ACKNOWLEDGMENT
A sincere thanks go to PT Adhi Persada Beton and the research institution of Trisakti University for making this research come into actualization.