Hasan et al. (2017) examined modifications and extensions of ant colony optimization (ACO) that could contribute to solving facility layout problems (FLPs), which are often NP-hard combinatorial problems. The paper identified potential future research areas in construction site facility layout problems, multi-criteria facility layout problems, and dynamic facility layout problems. Klausnitzer and Lasch (2019) investigated the advantage of integrated planning of facility layout and material handling network design using a holistic modeling approach. The results indicated superior layout solutions and planning process efficiencies compared to traditional sequential approaches. Suhardi et al. (2019) redesigned a garment factory sewing department layout using systematic layout planning and ergonomics to minimize material

1. 1.Classification of facility layout problems:
a review study
Facility layout problem (FLP) is defined as the placement of facilities in a plant area, with the
aim of determining the most effective arrangement in accordance with some criteria or
objectives under certain constraints, such as shape, size, orientation, and pick-up/drop-off point
of the facilities. It has been over six decades since Koopmans and Beckmann published their
seminal paper on modelling the FLP. Since then, there have been improvements to these
researchers’ original quadratic assignment problem. However, research on many aspects of the
FLP is still in its initial stage; hence, the issue is an interesting field to work on. Here, a review
of literature is made by referring to numerous papers about FLPs. The study is mainly
motivated by the current and prospective trends of research on such points as layout evolution,
workshop characteristics, problem formulation, and solution methodologies. It points to gaps
in the literature and suggests promising directions for future research on FLP.
Hosseini-Nasab, H., Fereidouni, S., Ghomi, S.M.T.F. and Fakhrzad, M.B., 2018. Classification of
facility layout problems: a review study. The International Journal of Advanced Manufacturing
Technology, 94(1), pp.957-977.
Hosseini-Nasab et al. (2018) described that placement of facilities in a plant area, with the aim
of determining the most effective arrangement in accordance with some criteria or objectives
under certain constraints, such as shape, size, orientation, and pick-up/drop-off point of the
facilities.
2.Mathematical optimization approaches
for facility layout problems: The state-of-
the-art and future research directions
Facility layout problems are an important class of operations research problems that has been
studied for several decades. Most variants of facility layout are NP-hard, therefore global
optimal solutions are difficult or impossible to compute in reasonable time. Mathematical
optimization approaches that guarantee global optimality of solutions or tight bounds on the
global optimal value have nevertheless been successfully applied to several variants of facility
layout. This review covers three classes of layout problems, namely row layout, unequal-areas
layout, and multi floor layout. We summarize the main contributions to the area made using
mathematical optimization, mostly mixed integer linear optimization and conic optimization.
For each class of problems, we also briefly discuss directions that remain open for future
research.
Anjos, M.F. and Vieira, M.V., 2017. Mathematical optimization approaches for facility layout problems:
The state-of-the-art and future research directions. European Journal of Operational
Research, 261(1), pp.1-16.

2. Anjos and Vieira (2017) facility layout are NP-hard, therefore global optimal solutions are
difficult or impossible to compute in reasonable time. Mathematical optimization approaches
that guarantee global optimality of solutions or tight bounds on the global optimal value have
nevertheless been successfully applied to several variants of facility layout. Three classes of
layout problems, namely row layout, unequal-areas layout, and multi floor layout. The main
contributions to the area made using mathematical optimization, mostly mixed integer linear
optimization and conic optimization.
3.A survey on multi-floor facility layout
problems
Facility layout problem is a well-known optimization problem which generally deals with the
arrangement of the facilities required in an organization. This problem has received much
attention during the past decades. However, the researchers have mainly focused on the case
where a single floor is available. While, in the competitive world, it is clear that using multi-
floor structure layouts are much more efficient and in some cases necessary due to the nature
of the functions and activities performed in the firms. Hence, this issue has recently attracted
much attention and is becoming increasingly popular. Nevertheless, the lack of a review study
on this subject for directing the new research is a great gap that has not been regarded so far.
In this paper, first a well-designed framework is presented. Then, all literature references in the
field of multi-floor facility problem (MFLP) are gathered, categorized and reviewed thoroughly
based on the framework. Accordingly, different applications of MFLP across various industries
are discussed; basic features of the problem to capture different situations are identified; the
formulation approaches to address the problems and the relevant resolution methodologies are
introduced; the majority of the contributions proposed in the literature are analysed from
different perspectives. Finally, several issues and research directions are highlighted to be
investigated in future work.
Ahmadi, A., Pishvaee, M.S. and Jokar, M.R.A., 2017. A survey on multi-floor facility layout
problems. Computers & Industrial Engineering, 107, pp.158-170.
Ahmadi, Pishvaee and Jokar (2017) multi-floor structure layouts are much more efficient and,
in some cases, necessary due to the nature of the functions and activities performed in the firms.
Hence, this issue has recently attracted much attention and is becoming increasingly popular.
Nevertheless, the lack of a review study on this subject for directing the new research is a great
gap that has not been regarded so far. In this paper, first a well-designed framework is
presented. Then, all literature references in the field of multi-floor facility problem (MFLP) are
gathered, categorized and reviewed thoroughly based on the framework.
4.A hierarchical facility layout planning
approach for large and complex hospitals
The transportation processes for patients, personnel, and material in large and complex
maximum-care hospitals with many departments can consume significant resources and thus
induce substantial logistics costs. These costs are largely determined by the allocation of the
different departments and wards in possibly multiple connected hospital buildings. We develop

3. a hierarchical layout planning approach based on an analysis of organizational and operational
data from the Hannover Medical School, a large and complex university hospital in Hannover,
Germany. The purpose of this approach is to propose locations for departments and wards for
a given system of buildings such that the consumption of resources due to those transportation
processes is minimized. We apply the approach to this real-world organizational and
operational dataset as well as to a fictitious hospital building and analyze the algorithmic
behavior and resulting layout.
Helber, S., Böhme, D., Oucherif, F., Lagershausen, S. and Kasper, S., 2016. A hierarchical facility
layout planning approach for large and complex hospitals. Flexible services and manufacturing
journal, 28(1), pp.5-29.
Helber et al. (2016) developed a hierarchical layout planning approach based on an analysis of
organizational and operational data from the Hannover Medical School, a large and complex
university hospital in Hannover, Germany. The purpose of this approach is to propose locations
for departments and wards for a given system of buildings such that the consumption of
resources due to those transportation processes is minimized. We apply the approach to this
real-world organizational and operational dataset as well as to a fictitious hospital building and
analyze the algorithmic behavior and resulting layout.
5.Dynamic facility layout problembased on open
queuing network theory
Determining the location of machines for given periods of time, depending on changes in the
material flow between the machines, is known in the literature as a dynamic facility layout
problem (DFLP). While most approaches focus on reducing handling and rearrangement costs,
this article also considers the amount of work-in-process (WIP) for a particular class of
problems. WIP results from the queuing phenomenon and depends on the availability of
transportation units. To solve these types of problems, we suggest the use of an analytical
approach which uses open queuing network theory and is based on a quadratic assignment
problem formulation. Since a queuing model approximates the studied system, the accuracy of
the results is evaluated through a comparison with simulation results. Considering both the NP-
hardness and the multi-objective nature of the problem, a meta-heuristic optimization approach
is proposed. It aims at determining the Pareto front using cloud-based multi-objective simulated
annealing (C-MOSA). The performance of C-MOSA is evaluated against other published
multi-objective approaches. Computational experiments are performed and the results show
that C-MOSA is capable of obtaining efficient results to solve the multi-objective dynamic
facility layout problem.
Pourvaziri, H. and Pierreval, H., 2017. Dynamic facility layout problem based on open queuing
network theory. European Journal of Operational Research, 259(2), pp.538-553.
Pourvaziri and Pierreval (2017) used analytical approach which uses open queuing network theory
and is based on a quadratic assignment problem formulation. Since a queuing model
approximates the studied system, the accuracy of the results is evaluated through a comparison
with simulation results. Considering both the NP-hardness and the multi-objective nature of

4. the problem, a meta-heuristic optimization approach is proposed. It aims at determining the
Pareto front using cloud-based multi-objective simulated annealing (C-MOSA). The
performance of C-MOSA is evaluated against other published multi-objective approaches.
Computational experiments are performed and the results show that C-MOSA is capable of
obtaining efficient results to solve the multi-objective dynamic facility layout problem.
6.A method for facility layout optimisation
including stochastic risk assessment
Facility siting and layout configuration are essential factors during design and expansion of
any industrial installation. In the recent past, cost-driven layout arrangements and the proximity
of chemical facilities to densely populated areas, among other factors, have also contributed to
the severity and propagation of various chemical incidents. Although several studies have been
reported to address such problems, there is still a need for incorporating safety into the facility
layout problem (FLP); especially for a method combining quantitative risk assessment (QRA)
and layout reformulation. Based on that, the objective of this study is to develop a framework
integrating layout formulation with a quantitative risk assessment method to support risk-based
decisions throughout the lifecycle of process facilities. The proposed methodology is divided
into three steps: risk calculation, determination of safety distances, and layout optimisation. In
the first stage, an in-house code has been developed to quantify risks associated with loss of
human life and structural damage stochastically. Subsequently, minimum separation distances
between process units are obtained to prevent escalation events. In the last stage, risk maps and
safety distances are accounted in a mixed-integer linear programming (MILP) for layout
optimisation. The application of the proposed methodology is demonstrated through a case
study. Sensitivity analysis is performed by varying risk values, safe distances, and risk
acceptance criteria. Even though different layout options are generated, a trend is observed
towards placing the equipment by its type.
Ahumada, C.B., Quddus, N. and Mannan, M.S., 2018. A method for facility layout optimisation
including stochastic risk assessment. Process Safety and Environmental Protection, 117, pp.616-628.
Ahumada Quddus and Mannan (2018) developed a framework integrating layout formulation
with a quantitative risk assessment method to support risk-based decisions throughout the
lifecycle of process facilities. The proposed methodology is divided into three steps: risk
calculation, determination of safety distances, and layout optimisation. In the first stage, an in-
house code has been developed to quantify risks associated with loss of human life and
structural damage stochastically. Subsequently, minimum separation distances between
process units are obtained to prevent escalation events. In the last stage, risk maps and safety
distances are accounted in a mixed-integer linear programming (MILP) for layout optimisation.
The application of the proposed methodology is demonstrated through a case study. Sensitivity
analysis is performed by varying risk values, safe distances, and risk acceptance criteria. Even
though different layout options are generated, a trend is observed towards placing the
equipment by its type.

5. 7.Optimal facility layout and material
handling network design
The designer of a plant layout is faced with the efficient arrangement of facilities, the planning
of material handling locations, and the aisle design. These mutually dependent subproblems
are traditionally solved in a sequential process. Designing the material flow paths within the
arranged facilities can be difficult and the expected material flow distances between the
arranged facilities can be exceeded significantly. Also, when the aisle design is not known, the
area between facilities is difficult to estimate and might require costly replanning. The purpose
of this study is to investigate the advantage of an integrated planning of these subproblems
using a holistic view. We propose two models in this paper. The first is a mixed integer linear
programming formulation for concurrently solving small-sized facility layout problems,
including the material handling points, and the path design. In a second model aisles are
implemented instead of paths, which is a scarcely considered design aspect within the related
literature. Several sets of valid inequalities are proposed to shorten the solution time. To
compare the solution quality between the proposed integrated approaches and traditional
approaches, a comprehensive computational study has been conducted considering several
influencing design factors. The results indicate that the integrated planning of the layout and
the material handling network design is a large untapped potential for designing superior layout
solutions and facilitating the planning process.
Klausnitzer, A. and Lasch, R., 2019. Optimal facility layout and material handling network
design. Computers & Operations Research, 103, pp.237-251.
Klausnitzer and Lasch (2019) investigated the advantage of an integrated planning of these
subproblems using a holistic view. We propose two models in this paper. The first is a mixed
integer linear programming formulation for concurrently solving small-sized facility layout
problems, including the material handling points, and the path design. In a second model aisles
are implemented instead of paths, which is a scarcely considered design aspect within the
related literature. Several sets of valid inequalities are proposed to shorten the solution time.
To compare the solution quality between the proposed integrated approaches and traditional
approaches, a comprehensive computational study has been conducted considering several
influencing design factors. The results indicate that the integrated planning of the layout and
the material handling network design is a large untapped potential for designing superior layout
solutions and facilitating the planning process.
8.A comprehensive study: Ant Colony
Optimization (ACO) for facility layout problem
In context of manufacturing, numerous models are designed to appropriately represent the
facility layout problem (FLP) and a variety of optimization methods have been applied to solve
these models. The ultimate goal of these methods is to find optimal solutions, In regard to
Swarm Intelligence (SI), Ant Colony Optimization (ACO) and Particle Swarm Optimization
(PSO) are regarded as the most important SI techniques of our time. In this paper, a brief
introduction for the so far most promising approaches to facility layout related topics, are
provided. The succeeding paper will then illustrate some of those, in more detail. Moreover,

6. we examine ACO modifications and extensions that could contribute to optimization methods
in FLP; mostly conform to NP-hard combinatorial problems. future research areas are
identified in Construction Site Facility Layout Problems, Multi-Criteria Facility Layout
Problems and Dynamic Facility Layout Problems.
Hasan, R.A., Mohammed, M.A., Ţăpuş, N. and Hammood, O.A., 2017, September. A comprehensive
study: Ant Colony Optimization (ACO) for facility layout problem. In 2017 16th RoEduNet conference:
networking in education and research (RoEduNet) (pp. 1-8). IEEE.
Hasan et al. (2017) examined ACO modifications and extensions that could contribute to
optimization methods in FLP; mostly conform to NP-hard combinatorial problems. future
research areas are identified in Construction Site Facility Layout Problems, Multi-Criteria
Facility Layout Problems and Dynamic Facility Layout Problems.
9.Facilitylayoutimprovementin sewing department
with Systematic Layout planning and ergonomics
approach
The design of facility layout is an influential factor in a company’s performance to support the
streamlined process of production. PT. PMJ is one of the garment industries that produce
women’s underwear. The total processing time in the sewing department often exceeds the
standard time set by the company. The composition of the machine and facilities at the sewing
department is considered to be not optimal. The order of machines in the production line has
not been arranged appropriately which causes the excessive distance in the material transfer.
In addition, the uses of straight material flow cause the workers to rotate their posture of the
body when taking the materials. Based on the results of the assessment of the condition of
workers in the initial facility layout using the Quick Exposure Check (QEC) method, the
highest total exposure score is on the back. This study aims to redesign the facility layout of
PT. PMJ using Systematic Layout Planning (SLP) and ergonomics approach to minimize total
material handling cost. Two design alternatives are proposed and the performance of each
design is evaluated using ARENA simulation software. Based on the calculation of total
material handling cost and simulation, the second proposed facility layout was chosen since it
was able to reduce the total material handling cost by 22.92% and material transfer time by
34.01%.
Suhardi, B., Juwita, E. and Astuti, R.D., 2019. Facility layout improvement in sewing department with
Systematic Layout planning and ergonomics approach. Cogent Engineering, 6(1), p.1597412.
Suhardi et al. 2019 designed the facility layout for the garment industries that produce women’s
underwear. The total processing time in the sewing department often exceeds the standard time
set by the company. The composition of the machine and facilities at the sewing department is
considered to be not optimal. The order of machines in the production line has not been
arranged appropriately which causes the excessive distance in the material transfer. In addition,
the uses of straight material flow cause the workers to rotate their posture of the body when
taking the materials. Based on the results of the assessment of the condition of workers in the
initial facility layout using the Quick Exposure Check (QEC) method, the highest total

7. exposure score is on the back. This study aims to redesign the facility layout of PT. PMJ using
Systematic Layout Planning (SLP) and ergonomics approach to minimize total material
handling cost. Two design alternatives are proposed and the performance of each design is
evaluated using ARENA simulation software. Based on the calculation of total material
handling cost and simulation, the second proposed facility layout was chosen since it was able
to reduce the total material handling cost by 22.92% and material transfer time by 34.01%.
10.Vadivel et al.2020 applied facility layout design in India postal facility layout in order to
improve the operational performance using MCDM methods. They have considered lean
service, workplace environment and ergonomics factors for judging the optimal layout
selection.