Supply Chain Issues Impacting the Construction of Infrastructure Projects: A Decision-Making Tool for Alternative Product Selection

Background The construction of infrastructure projects is complex process involving two disjointed processes: Building the project according to the plans and specifications, and supply chain management of construction materials and products through the suppliers, sub-contractors, and main contractors. The construction sector is the world's largest consumer of raw materials. Materials typically account for 50% to 60% of the total project cost and can influence up to 80% of the schedule of a construction project (Kar and Jha, 2008). The construction projects suffer from delays, cost overrun, and low productivity due to delays in the delivery of materials and products. Therefore, supply chain management has always been a major consideration for the completion of the construction projects on schedule. However, in the recent times, the pandemic-induced shutdowns, civil unrest, natural disasters, and the ongoing war in Ukraine have all wreaked havoc on local construction industry supply chains. Where previously it used to take weeks to procure building materials and equipment, contractors are now having to wait months for their orders to arrive. Late delivery of materials is a major cause of time and cost overruns on the construction projects. For water and wastewater infrastructure projects for utility agencies, delays and cost overruns lead to service disruptions and customer dissatisfaction in addition to the fiscal inefficiencies. In order to avoid these potential issues, the contractors are proposing alternative products as substitutions for the specified products during the construction and utility agencies, as project owners are willing to consider the alternative product for the construction. However, this presents the engineers and owners with the difficult decision of selecting and approving the alternative construction product or material during the construction under time constraints taking into consideration the several project criteria such as the meeting the design specifications, product cost, time of delivery, schedule impacts, project life, ease of construction, ease of operation and maintenance and environmental regulatory requirements. Therefore, the objective of this paper is to develop a decision-making tool that can be used by the engineers and owners to compare alternative construction products or materials and select best choice using multiple criteria more wholistically rather than using cost or time delay as sole criteria. Objectives: Since the pandemic, the issues with the supply and long lead time for delivery of the pipes for the construction of the water main in the water utility sector has become a more commonly encountered problem. There are several instances where the contractor must wait for the delivery of pipe for more than six months whereas the time for installation and commissioning of the water main is less than a month. To avoid the long lead time, the contractors propose to use the alternate pipe materials that they have already in their inventory or use the suppliers who can deliver the alternate pipe materials with less lead time. Each pipe material has its own merits and disadvantages, and they must be evaluated for multiple criteria before the proposed material is accepted for the construction. To assist the engineers and owners with the decision making for the selection and approval of the alternate product, a decision-making tool using multiple criteria decision analysis was developed and the developed decision-making tool has been used to illustrate a case study to compare the alternate pipe materials and select the most suitable material for the project. Methodology In this study, one of the most popular multicriteria methods called Analytical Hierarchy Process (AHP), is used for developing the decision-making tool (Saaty, 2008). This method gained popularity due to its simplicity and the ease with which one can obtain quite good solutions to serious hierarchical problems consisting of main criteria and sub criteria. The AHP method (Saaty, 2008) is used to make a decision in an organized way to generate priorities. This method involves the decomposition of decision into the following steps: 1) Define the problem and determine the kind of knowledge sought; 2) Structure the decision hierarchy from the top with the goal of the decision, then the objectives from a broad perspective, through the intermediate levels (criteria on which subsequent elements depend) to the lowest level (which usually is a set of the alternatives); 3) Construct a set of pairwise comparison matrices. Each element in an upper level is used to compare the elements in the level immediately below with respect to it; 4) Use the priorities obtained from the comparisons to weigh the priorities in the level immediately below. Do this for every element. Then for each element in the level below add its weighed values and obtain its overall or global priority. Continue this process of weighing and adding until the final priorities of the alternatives in the bottom most level is obtained. To make comparisons, we need a scale of numbers that indicates how many times more important or dominant one element is over another element with respect to the criterion or property with respect to which they are compared. Table 1 exhibits the scale (Plebankiewicz and Kubek, 2016; Saaty, 2008). These steps described above can is easily implemented in excel spreadsheet as it involves matrix multiplication and aggregations to generate the weighted priorities and pairwise comparisons. The process can also be automated with VB macros for complex selection processes involving numerable criteria and alternatives. Illustrative Case Study/Results/Discussions The methods described in the previous section were applied to a case study to compare alternative pipe products and select the most suitable one based on the performance under multiple criteria. The alternative products considered are Ductile Iron Pipe (DIP), Polyvinyl Chloride Pipe (PVC) and High-Density Polyethylene pipe (HDPE). The goal is to select the best pipe. It is assumed that all the pipes meet the functional and capacity specifications. However, the variations are in the following criteria: 1) Cost of the pipe, which is dependent on the material and availability from the supplier, 2) Delivery time, depends on the inventory and availability from the supplier and will have the project schedule impacts, 3) Project life is dependent on the pipe material and DIP last longer than other pipes, 4) Hydraulics, the capacity to convey the flows with minimal energy loss, 5) Corrosion resistance, which is dependent on the material. PVC and HDPE have superior corrosion resistance, 6) Ease of construction depends on the depth of excavation, joining of pipes, etc., 7) Ease of operation and maintenance which is operator's preference in case of pipe breaks during emergencies, and 8) Sustainability of the material depends on the carbon footprint during the life cycle of the product. The AHP for this case study is shown in Figure 1. The rankings are assigned, giving extreme preference for the cost of the pipe and the time of delivery. If the time of the delivery is given extreme preference, the project owner may have to pay high price for the pipe which is core of the problem under supply chain issues the construction industry is currently facing. In this case study, it is assumed that the PVC pipe is the specified pipe for the project from the budget consideration and the contractor is proposing DIP at the higher cost to avoid the time delays. The pairwise comparison matrix for the criteria are performed and the priorities were estimated. Then, the assigned priority from the criteria is used for pairwise comparison among the alternative products and overall priority was estimated. The above steps involving matrix multiplications and aggregations and pairwise comparisons were implemented in excel spreadsheet. The results from the AHP method of analysis revealed that the DIP is the best choice. The sensitivity analysis was also performed varying the delivery time from extreme importance to moderate importance, The sensitivity analysis revealed that the PVC is the best choice if the delivery time is of low preference. Conclusions This work demonstrates how the decision-making tool developed based on Multiple-criteria decision analysis method can be used to select the piping material for the project when the alternative materials are proposed as the substitution for the specified product under the situations constrained by the supply chain issues. The structured approach presented in this study increases the chances of selecting the best product. The Utility owners and Engineers need simple but effective decision-making methods, such as the one described in this study to help them in the alternative selection.