Ahmed W. A. Hammad

A Computational Method for Estimating Travel Frequencies in Site Layout Planning

Optimizing the layout of facilities on a construction site to minimize the material handling costs has been widely investigated in the literature. An integral part of the objective function utilized in the previously proposed optimization models is the frequency parameter, which generally provides a rough estimate of the frequency of travel between each pair of facilities at a specific stage of the project. The majority of travel frequencies deduced in prior studies have been estimated merely based on past experience and may not be an actual representation of movements within the project studied. There is currently a lack of a systematic approach for estimating travel frequencies, required in site layout planning, based on the information available at early stages of the project. Obtaining a reasonable estimate of the travel frequency matrix requires a realistic evaluation of the material transportation quantities at each construction stage. This necessitates the utilization of information on the progress of different activities and their corresponding material needs during the various stages. This paper presents a framework for obtaining travel frequencies at different construction project phases by taking advantage of the information made available by building information models and project schedules. The estimated frequencies are later embedded as parameters in an optimization model to improve site layout planning. The results of a case study are presented to highlight the capabilities of the proposed framework.

Location Optimization of Tower Crane and Allocation of Material Supply Points in a Construction Site Considering Operating and Rental Costs

AbstractThe choice of a suitable tower crane along with its location may considerably affect the costs and duration of the construction process. The location of the tower crane determines the travel time of transporting material between the supply and demand points and thus the operation costs. On the other hand, the distance between the tower crane and supply points as well as the distance between the tower crane and demand points considerably affects the minimum required load moment capacity of the cranes and thus the cranes’ rental and operating costs. Previous studies on optimizing the location of tower cranes on a construction site have focused mainly on minimizing the crane operation costs through minimizing their operation time, overlooking the effect of tower crane location on its required capacity and thus rental and operation costs. This paper presents a modified crane location optimization model that also accounts for the effects of crane location on its required capacity, on top of operating t...

A cutting plane algorithm for the site layout planning problem with travel barriers

A novel discrete Construction Site layout planning model (SLP) is proposed, where multiple coverage of locations by facilities is permitted.We contrast the proposed model with the approach commonly adopted in the literature to solve the SLP problem to exact optimality.We quantify the impact of space discretisation on discrete SLP models.We propose a novel cutting plane algorithm to solve large instances of the discrete SLP problem.We provide a comprehensive analysis on the computational effectiveness of the proposed models. Site layout planning is an imperative procedure that may significantly impact the productivity and the efficiency of logistical operations undertaken on a construction site. This paper considers the site layout planning problem (SLPP) which entails the allocation of temporary facilities on a construction site in the presence of travel barriers such that the total transportation cost between facilities is minimised. In order to account for travel barriers, the SLPP is typically solved under the assumption that the available region for facility layout can be discretised. In this paper, we propose a general Mixed Integer Programming (MIP) model to represent the SLPP, accounting for the presence of barriers, and we show how space-discretised formulations can be derived from this model. In particular, we propose a novel MIP model, which permits facilities to cover multiple locations. This is then benchmarked against a commonly adopted MIP model in the literature. We also highlight a systematic procedure to convert the continuous feasible space in SLPP to a set of discretised locations based on the concept of d-visibility, enabling us to approximate the barrier distance function embedded in the objective function. In particular, we focus on presenting a simple space discretisation approach for converting the continuous SLP into a discrete problem for which the discrete SLP models would be applicable. Space-discretised MIP formulations are highly combinatorial and we introduce a cutting plane algorithm to improve their tractability. Specifically, we propose a novel exact location-decomposition algorithm which works from a relaxed MIP formulation and iteratively generates feasibility cuts to converge to an optimal solution. Both space-discretised MIP models and the decomposition algorithm are tested on a large group of instances to analyse their effectiveness in solving the SLPP. Computational results indicate that the proposed location-decomposition algorithm improves on the pure MIP approach and provides a competitive framework to solve realistic SLPP instances.

A mixed-integer nonlinear programming model for minimising construction site noise levels through site layout optimisation

Activities undertaken on a construction site are often accompanied with high levels of noise. Addressing the issue of noise pollution in construction is gaining significance with the growing awareness about the social and environmental components of sustainable construction and the increasing numbers of projects being undertaken in congested urban areas. The documented methods for reducing noise pollution in construction include controlling (1) the noise produced at the source; (2) noise levels reaching a receptor; (3) noise propagated along the transmission path. Methods addressing the latter points use the fact that attenuation of noise increases as the transmission path gets longer. Thus the efficiency of such methods can be improved considerably through optimising the arrangement of temporary facilities on construction sites, with respect to a receptor, making use of noise attenuation due to distancing noisy facilities away from noise-sensitive receivers. The building under construction can also be used as a barrier to the noise transmission path, where obstruction of particular facilities from a given receiver can help in producing lower levels of sound as measured at the receptor. The available literature on site layout planning is extensive but limited to only achieving traditional construction project objectives (travel and material handling cost, safety, etc.). This paper presents a mixed integer non-linear programming (MINLP) model that optimises the location of temporary facilities on site in order to minimise the sound levels measured at a pre-defined receptor. The present model is expressed in three stages: (1) defining the noise objective function; (2) implementing model constraints; and (3) application of COUENNE to solve the MINLP for a case study.

A Bi-level Mixed Integer Programming Model to Solve the Multi-Servicing Facility Location Problem, Minimising Negative Impacts Due to an Existing Semi-Obnoxious Facility

We propose a bi-level multi-objective model to solve the multi-facility location problem with traffic equilibrium constraints. The main facility location problem within our proposed model consists of locating a set of buildings with varying sensitivity thresholds due to the negative impacts propagating from an existing semi-obnoxious facility. The traffic routing problem is modelled as a user equilibrium which is embedded using its Karush-Kuhn-Tucker optimality conditions. We use the convex scalarisation approach to deal with multiple objectives. Two solution methods are then contrasted: in the first method we solve our linearised model using an off-the shelf Mixed Integer Programming solver. In the second solution approach we use Benders Decomposition algorithm to improve computational tractability. Numerical results highlight the superiority of the decomposition approach when solving a realistic-sized instance.

Bilevel Mixed-Integer Linear Programming Model for Solving the Single Airport Location Problem

AbstractThis paper addresses the airport facility location problem considering environmental impacts and induced changes to traffic on the underlying road network. An optimization model is develope...

Accounting for Embodied Carbon Emissions in Planning and Optimisation of Transport Activities During Construction

To mitigate the environmental impacts of construction-related activities, environmental factors should be incorporated within the planning procedure to inform the decision-making process at all levels. A large amount of embodied carbon of buildings is the result of material processing, transportation and construction. An opportunity therefore exists to alleviate the emissions of greenhouse gasses in the construction industry through optimising the associated construction operations while minimising carbon emissions. In this chapter, the focus is on the applications of smart planning approaches that incorporate the use of mathematical optimisation to manage and mitigate the embodied carbon of buildings, through proposing a relevant decision-making framework. Both on-site and off-site transportation in construction are considered since such operations contribute considerably to embodied carbon of buildings. The interrelation of several classes of well-known and relevant optimisation models is addressed, along with their applications in the planning stages of material transportation. A case study is presented to highlight the major benefits attainable through employing different classes of models within a scheme targeting the reduction of the carbon emissions in the transportation activities of a building’s life cycle.

Sustainable Lighting Layout in Urban Areas: Maximizing Implicit Coverage and Minimizing Installation Cost

A key decision in the design of urban lighting is the location of the luminaries that are used to illuminate the specified region. The decision needs to account for coverage requirements identified in certain areas, based on safety considerations and nature of work activity, along with ensuring the cost effectiveness of the installation pattern adopted. In this work, a novel approach is presented via a multi-objective mathematical optimisation model that results in a sustainable layout of light poles in urban region. A maximal coverage objective, with implicit demand cover, is formulated as a measure of the social requirement in urban lighting, which models security and safety associated with night-time lighting of the urban region. At the same time, the economical aspect of the layout is considered via minimising the installation cost of the lighting layout. A realistic case example is then solved using the ϵ-constraint method. A Pareto optimal front for the case considered is constructed and analysed.

Modular vs Conventional Construction: A Multi-Criteria Framework Approach

The use of modular construction methods for projects offers significant time and environmental improvement relative to conventional construction methods. Currently, there is a lack of appropriate assessment approaches to capture the differences between modular and conventional construction. This paper proposes a framework to aid decision makers in choosing between the latter construction methods through the integration of building information models with material libraries, project schedules and machinery inventory. A fixed set of performance parameters, whose attributes are shared among both construction methods, are defined to allow for a reasonable comparison across multiple criteria, including embodied carbon, productivity and total construction costs expended. The dynamics of the project are incorporated by modelling the various stages of the project within a building information model. The proposed framework is tested on a realistic case example, highlighting its applicability as a decision support tool for construction method selection.

Decision Support System for Modular Construction Scheduling

The use of modular construction as opposed to traditional on-site construction presents an opportunity to improve a project’s economic and sustainable performance. At the same time, substantial savings in the overall project’s duration can be achieved. The potential for reducing the overall make-span period involved in manufacturing and assembling the modularised components, along with the constant need for aligning the work schedule with the in-house manufacturing schedule, leads to the need for a repetitive scheduling optimisation procedure for modular manufacturing operations. This paper presents a framework and a decision support system to schedule operations in modular building factories. The framework is divided into 3 layers; the first layer concerns the assignment of workers to workstations; the second layer solves the scheduling of jobs to workstations while the last layer governs the overall operations of production lines through formulating a parallel machine scheduling problem. For demonstration purposes, a computational test is conducted on the final optimisation stage using a practical case study to solve the parallel machine scheduling problem. To account for resource allocation and levelling, the model is presented as a resource constraint one. Results reveal the satisfactory performance of the proposed model.