# Multi-Objective Resource-Constrained Scheduling in Large and Repetitive Construction Projects
## 2 Related Work
At the same time, the goal of a rather constant usage of the construction company's resources over time remains a top priority. When scheduling and allocating resources in large and repetitive projects, it is harder to visualize and carry out the process than in typical, small, or non-repetitive ones. The aim is still to reduce resource idle time, machinery movement in and out of the workplace, and staff hiring and firing situations. The development of an optimization model for scheduling such projects could result in significant time, resource consumption, and cost savings. The literature includes research efforts focusing on the resource schedulingproblem in repetitive and multi-projects and in approaches targeting multiple optimization goals, mainly during the last ten years. The review results are codified in Table 1. The information that is presented includes the optimization sub-objectives, the solving methods, and the main characteristics of the case studies for method evaluation. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**No. ** & **Authors** & **Year** & **Objective Function** & ** \begin{tabular}{c} **Repetitive/** \\ **Multi-** \\ **Projects** \\ \end{tabular}  & ** \begin{tabular}{c} **Multi-** \\ **Objective** \\ \end{tabular}  & **\ \begin{tabular}{c} **No. of** \\ **Activities** \\ \end{tabular}  & ** \begin{tabular}{c} **Optimization** \\ **Method** \\ \end{tabular}  \\ \hline
1 & [PERSON] et al. [19] & 2008 & \ \begin{tabular}{c} minimize (1) project makespan, \\ (2) variance of the sum of the resource \\ usage over time \\ \end{tabular}  & - & Yes & \begin{tabular}{c} 30, 60, 90, \\ 120 \\ \end{tabular}  & NSGA-II \\
2 & [PERSON] and & \begin{tabular}{c} minimize (1) resource overallocation, \\ **[PERSON]** [5] \\ \end{tabular}  & 2015 & \ \begin{tabular}{c} (2) project deadline exceedance, \\ (3) day-by-day resource fluctuations \\ \end{tabular}  & - & Yes & 10 & \begin{tabular}{c} Genetic \\ Algorithms \\ \end{tabular}  \\
3 & [PERSON] & 2015 & \ \begin{tabular}{c} minimize (1) project makespan, and \\ (2) project cost \\ \end{tabular}  & - & Yes & 100, 200 & \begin{tabular}{c} Ant Colony \\ Optimization \\ \end{tabular}  \\
4 & [PERSON] et al. [20] & 2015 & \ \begin{tabular}{c} minimize total weighted tardiness \\ of projects \\ \end{tabular}  & M & No & 120, 180 & \begin{tabular}{c} Genetic \\ Algorithms \\ \end{tabular}  \\
5 & [PERSON] et al. [21] & 2016 & \ \begin{tabular}{c} minimize (1) project duration, \\ (2) project cost \\ \end{tabular}  & R & Yes & 20, 90 & \begin{tabular}{c} Genetic \\ Algorithm \\ \end{tabular}  \\
6 & [PERSON] [15] & 2016 & \ \begin{tabular}{c} minimize (1) project makespan, \\ (2) resource capacity total cost \\ \end{tabular}  & - & Yes & 30, 60, 120 & \begin{tabular}{c} Evolution \\ Algorithm \\ \end{tabular}  \\
7 & [PERSON] et al. [22] & 2017 & \ \begin{tabular}{c} minimize project duration \\ (2) duration of the project \\ group, (2) total cost, (3) financing cost, \\ (4) maximum required credit, \\ (5) resource fluctuation, and (6) peak \\ resource demand \\ \end{tabular}  & M & No & 30, 60, 90, & \begin{tabular}{c} Genetic \\ Algorithms \\ \end{tabular}  \\
8 & [PERSON] et al. [23] & 2017 & \begin{tabular}{c} minimize (1) duration of the project \\ group, (2) total cost, (3) financing cost, \\ (4) maximum required credit, \\ (5) resource fluctuation, and (6) peak \\ resource demand \\ \end{tabular}  & M & Yes & 9, 25, 30 & NSGA-II \\
9 & [PERSON] et al. [24] & 2018 & \ \begin{tabular}{c} minimize (1) project duration, \\ (2) project cost, (3) work interruptions \\ \end{tabular}  & R & Yes & 20, 75 & \begin{tabular}{c} Genetic \\ Algorithm \\ \end{tabular}  \\
10 & [PERSON] and & 2018 & \ \begin{tabular}{c} minimize project duration \\ (2) project cost, (3) work interruptions \\ \end{tabular}  & R & No & 20 & \begin{tabular}{c} Genetic \\ Algorithm \\ \end{tabular}  \\
11 & [PERSON] and & 2019 & \ \begin{tabular}{c} minimize (1) project duration, \\ (2) project cost, (3) work interruptions \\ \end{tabular}  & R & Yes & 20 &