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The site layout has a significant impact on the efficiency of construction operations. Planning an effective site layout partly involves identifying and positioning temporary facilities such as tower cranes and areas on the jobsite for materials storage. This study proposes an approach to optimizing the type and location of the tower crane and material supply point on construction sites.

The problem is formulated into an integer linear programming (ILP) model considering the total cost of material transportation as the objective function and site conditions as constraints. The efficacy of the approach is demonstrated by finding the optimum site layout for a numerical example. The proposed model is validated and verified using two methods.

Results indicate that the proposed model successfully identifies the type and location of the tower crane and the location of material supply point, leading to approximately 20% cost reduction compared with when such features of a site layout are decided solely based on experience and educated guesses of the construction manager.

The primary contribution of this study is to present a modified linear mathematical model for site layout optimization that exhibits improved performance compared with previous models. The type and location of the tower crane and the material supply point as decision variables are extracted directly from solving the proposed model. The proposed model will help enhance time and cost efficiency on construction sites.

Public–private partnerships (PPPs) are notoriously prone to disputes among stakeholders, some of which may unduly jeopardize contract performance. Contract disputes arising in Iran are often due to inefficiency of PPP concession agreements and practice. This study presents a causal-predictive model of the root causes and preventive measures for inter-organization disputes to enhance the likelihood of achieving desirable performance in PPP projects.

A theoretical “causal-predictive” model was developed with fourteen hypotheses based on extant literature and contractual agency theory, which resulted in the creation of a pool of 110 published items. Data were obtained from a questionnaire survey with 75 valid responses, completed by 4 stratified groups of Iranian PPP experts. Partial least square structural equation modeling (PLS-SEM) was used for validating the proposed model via a case study.

Results reveal that the main three factors of PPP desirable performance are as follows: on-time project completion, high quality of activities/products and services for public satisfaction. Further, the most influential factors of the lifecycle problems, construction stage, and preferred risk allocation included risk misallocation, improper payment mechanism and failure to facilitate a timely approval process.

For researchers, the findings contribute to the theory of contractual agency; specifically, how different influences among the model's elements lead to better PPP performance. In practical terms, proposed outcome-based strategies will inform PPP stakeholders to avoid dispute occurrence and thus improve the time, quality and services of projects.