Iris D. Tommelein

The foundations of lean construction

Looks at a broad range of topics related to the processes of design and construction. Its overall aim is to look at ways that clients can improve the value for money outcomes of their decisions to construct buildings.

Knowledge-based assembly of simulation networks using construction designs, plans, and methods

An object-oriented and interactive computer system is presented that integrates project- and process-level planning. This system, named CIPROS, realistically models construction processes by matching resource properties with design component properties and operation durations. It uses a modular representation to create discrete event simulation networks and to relate simulation output to the design and construction plan of the facility to be built. CIPROS users must identify and describe attributes of components to be constructed, based on the facilitys design drawings and specifications, and they must develop a CPM plan. They must also select a construction method to perform each activity by retrieving the appropriate elemental simulation network from a library of networks that represent such methods. CIPROS then pieces the networks together based on sequential relationships from the plan and property values input from the drawing and specification data. The latter initialize the simulation network resources that make up the constructed facility. To complete the simulation network, users must specify the construction resources that are available to perform the work and which may be shared by activities. CIPROS comprises a fully-operational discrete event simulation engine that is called once a network is completed. Besides producing statistical reports that are instrumental in assessing the quality of the construction plan, CIPROS can also be used to check the degree of facility completion as the simulation progresses.

Lean management methods for complex projects

This paper reviews the principles, history, applications and current research issues associated with lean construction, in order to provide a foundation for future research in this area. Lean is a management approach that emerged in the automobile industry and spread initially to other forms of repetitive manufacturing and ultimately to service industries. Despite its success in practice, the lean philosophy and methods have not been fully evaluated and incorporated into the academic literature. The question remains to what extent lean management methods are unique and beneficial and how they are related to principles and models in management science, production management and related fields. One of the relevant issues is the adequacy of lean methods to the management of complex projects. As project complexity increases, emergent phenomena increase. Consequently, leadership must become more adaptive and less prescriptive in order to be successful. This paper describes some of the key lean management metho...

CEPM 3: contributors to lead time in construction supply chains: case of pipe supports used in power plants

This paper describes process models that characterize the design phase in the supply chain of pipe supports used in power plants. The models are used to study how production system design factors such as batching, uncertainty, and multitasking throughout this phase hamper supply chain performance. These factors all cause an increase in lead time. The models build on the STROBOSCOPE discrete-event simulation engine and illustrate several deterministic and probabilistic simulation scenarios including different batch sizes, uncertainty levels, and allocation percentages of shared resources. Based on the analysis of the simulation results, this paper recommends performance improvement opportunities that apply not only to the supply chain of pipe supports but generally to the delivery of capital projects.

External Change in Large Engineering Design Projects: The Role of the Client

A problem facing the management of large engineering design projects is: Why do clients often adopt an early commitment strategy on design decision-making when they want to speed up project delivery, yet allow late changes to the project definition to accommodate the resolution of (un)foreseen external uncertainties? Empirical findings illustrate this problem and underpin a 2-stage model of the concept development process, in which conceptualization is followed by design, and stochastic pre-emption simulates asymmetric changes. Simulation experiments demonstrate that when clients make commitments early on in conditions of high uncertainty, they increase the likelihood (upside risk) of speeding up delivery if external events do not materialize; however, if these events do materialize, they increase the likelihood (downside risk) of causing design rework and losing process predictability-especially when the ability to reuse design work after a change is limited. We show that moderate design postponement is appropriate if clients relinquish some of the upside risk of finishing the design sooner. Moderate design postponement does not increase the downside risk of overrunning the delivery completion date in relation to the risk clients incur when they commit earlier because it reduces expected variability in design. These insights highlight the clients role in foreseeing external uncertainties and judiciously instructing changes to design teams. They also demonstrate the applicability of postponement to large engineering design projects where external uncertainty emerges as a fundamental contingency

Understanding project success through analysis of project management approach

Purpose – The purpose of this paper is to show that project success is dependent on the project management approach selected, relative to the challenges posed by the project, and to develop an analytical model for analyzing the performance of the project organization. Design/methodology/approach – The research is based on literature review, model development, interviews, and case studies. Findings – The findings define two different approaches in project management: The prescriptive approach focusses on the formal qualities of the project organization, including governing documentation and procedures. The adaptive approach focusses on the process of developing and improving a project organization, project culture and team commitment. The two approaches have been identified through studies of three different case projects. An analytical model, referred to as the Pentagon model, has been applied for analyzing the performance of the project organization and explaining the project management approach. The mod...

Value Stream Mapping for Make-to-Order Products in a Job Shop Environment

This paper investigates the use of Value Stream Mapping (VSM) for make-to-order products in a job shop environment, specifically the fabrication of Heating Ventilating and Air Conditioning (HVAC) sheet metal ductwork. The use of VSM for analyzing the production of repetitive units has proven to be successful in different industries. The use of VSM for studying the production of non-repetitive units requires some adaptation from repetitive-unit uses in order to successfully capture the attributes of multiple product families required at different frequencies and volumes. The VSM for a job shop environment has to be flexible to deal with the dynamic nature of job shops, e.g., maps may change daily according to the products scheduled for fabrication. Other aspects of the production system for sheet metal ducts that should be captured in the maps include the availability of a multi-skilled workforce for shop and site work, single flow of product and worker, and development of forecasts and capacity allocation to deal with frequent changes on incoming orders from project sites. Besides discussing the peculiarities of this job shop environment and their representation in a VSM, the authors discuss the process for elaborating VSMs for this production system and the definition of data used to develop them. Finally, the authors present a VSM for the fabrication of sheet metal d ucts and discuss it using Lean Production concepts and recommend systematic data collection to reveal current practices and opportunities for improvement.

Role of Tolerances and Process Capability Data in Product and Process Design Integration

A case from the authors’ experience reveals that dimensional tolerance, in terms of physical dimensions of components and their position within the system; interact to compound the process variability and uncertainty within a project. Variability adds to the costs of a process with long cycle times, high work in progress levels; wasted capacity due to low utilization of resources; lost throughput, and a general increase in waste (poor quality and increased scrap) (Hopp and Spearman 2000). Early constructability research supports this observation: as it identified dimensional tolerances as a major factor in ease of construction and subsequently cost and schedule (O’Connor 1989 and CII 1986). Though constructability research has developed many tools for application to design, none appear to have focused on how to identify appropriate tolerances. In addition, other industries outside AEC have made significant improvements by carefully measuring and understanding the effects of tolerances within their systems. Quantifying dimensional tolerances for construction operations and materials, and developing strategies to mitigate their effects is therefore an important objective in research and design practice. Based on a case study, a strategy is recommended in which product designers are challenged to design systems that accommodate most process variability without compromising project goals.

Upstream Problem Solving Under Uncertainty and Ambiguity: Evidence From Airport Expansion Projects

Environmental changes are common during development of large engineering (infrastructure) projects. To accommodate them when they occur, developers design and physically execute the upstream base building with preliminary information about the downstream business-critical fit-out. Base-building subsystems provide service space for occupancy, whereas fit-out subsystems make the space functional. We build theory on design under uncertainty and ambiguity from case study research, drawing on theory of preliminary information exchange in concurrent development. We find that the base-building subsystem shows low sensitivity to incremental changes in fit-out. However, it shows high sensitivity to radical changes, unless the two subsystems interact in a modular fashion. In the face of slow resolution of downstream uncertainty and difficulties in decoupling the physical interfaces (as is the case in modular design for example), upstream developers avoid starvation by making working assumptions at risk and exploring the space of possible design solutions through an early ldquooptioneeringrdquo stage. Two patterns for problem-solving upstream stand out: 1) iterate design when preliminary information is either ambiguous or precise, but unstable and 2) build buffers in the design definition to absorb foreseeable changes when the preliminary information lacks precision but is not ambiguous. Buffers can be designed out if downstream uncertainties resolve favorably before the buffers are physically executed.

Lean hospitals: a new challenge for facility designers

This article presents a literature review of a wide array of implementation studies of Lean healthcare practices, performed worldwide. Firstly, we review some fundamentals of Lean thinking. Second, we describe the continuous work improvement cycle along with some commonly used Lean tools. We then examine how the implementation of Lean practices has affected hospitals and their users. Furthermore, we review the encountered challenges and opportunities. Finally, we present process- and technology improvement ideas to address the urgent needs and critical shortcomings of current healthcare practices. Lean practices are becoming increasingly widespread in the healthcare industry. Readers new to them might like to investigate their applicability more deeply.