Anil Sawhney

CEPM 3: lead time reduction via pre-positioning of inventory in an industrial construction supply chain

Lead time reduction is a key concern of many industrial buyers of capital facilities given current economic conditions. Supply chain initiatives in manufacturing settings have led owners to expect that dramatic reductions in lead time are possible in all phases of their business, including the delivery of capital materials. Further, narrowing product delivery windows and increasing pressure to be first-to-market create significant external pressure to reduce lead time. In this paper, a case study is presented in which an owner entered the construction supply chain to procure and position key long-lead materials. The materials were held at a position in the supply chain selected to allow some flexibility for continued customization, but dramatic reduction in the time-to-site. Simulation was used as a tool to consider time-to-site tradeoffs for multiple inventory locations so as to better match the needs of the construction effort.

International comparison of cost for the construction sector: towards a conceptual model

Purchasing power parity (PPP) is often used by global organizations to perform international comparison of gross domestic product and other important economic indicators. Gross level comparisons include comparison of the output of the construction sector. Calculation of a construction sector PPP is a challenging endeavor incorporating aspects of construction finance, management, and estimating. The existing method in use by the World Bank relies upon a detailed estimate for a set of standard projects. The drawbacks of this method have been noted. Exploring the use of baskets of goods and services, the article finds that the inherent incorporation of labor and equipment charges is an important advantage of the standard projects method (SPM). However, the SPM is difficult and expensive to conduct. Therefore, a reduced scope of construction cost estimating is proposed, through the use of a basket-of-construction-components (BOCC). This article describes the BOCC approach that can be utilized to calculate construction sector PPP.

IntelliCranes: an integrated crane type and model selection system

The importance of the utilization of cranes in construction operations has resulted in the development of structured methods for crane selection. Most of these methods are for crane model selection and require the user to stipulate the type of crane to be used for the construction operation under consideration. Availability of a structured method for crane type selection will greatly benefit the overall crane selection process. This paper describes a prototype integrated crane selection tool, called IntelliCranes, designed to assist in both crane type and crane model selection. The key feature of IntelliCranes is the systematic incorporation of subjective and qualitative criteria in crane type and model selection.

CEPM 3: process mapping of residential foundation slab construction processes

With the purpose of mapping residential foundation slab construction processes, the authors collected the necessary process mapping information. After the completion of the process mapping for several common residential foundation slab construction processes, the team then used the process maps to identify potential process improvements and documented these in new, revised process maps. The residential foundation slab construction process mapping effort coupled with process simulation demonstrated the existence of opportunities for residential foundation slab construction process improvements. This has motivated the homebuilder partners to further pursue the issue by developing a residential foundation slab construction process to a stage where several prototype foundation slabs can be built. This report provides information on all steps accomplished and all issues involving the process mapping effort.

Special purpose simulation template for workflow analysis in construction

Workflow analysis is an important component in the simulation of construction operations. It involves creating a specific number of work requests for a crew every time period, computing outputs such as work arrival rate for a downstream crew and plotting work in process (WIP). These outputs are not directly provided in many construction simulation software tools. Determining these outputs is generally considered a time consuming and tedious undertaking. Developing modeling constructs that automate the computation of these workflow outputs will be useful for construction modelers. This paper presents a special purpose simulation (SPS) template developed for workflow analysis. The SPS template consists of four modeling constructs that implement the workflow analysis functionalities mentioned above. The SPS template logic was verified using two simulation experiments. Use of this SPS template for analyzing different workflow based issues as well as to test the production management principles in construction is also highlighted.

A Discrete Event Simulation Model to Analyze the Residential Construction Inspection Process

Inspections performed by code enforcement officials (building inspectors of a code enforcing jurisdiction) to confirm building code compliance are an important part of the home building production process. In 2003, an estimated 10 to 15 million code compliance inspections for residential construction were performed in various jurisdictions around the nation. The inspection process and its outcome have a significant impact on all the stakeholders, including city building departments, homebuilders, and trade contractors. This paper focuses on the inspection process in production homebuilding and provides critical analysis via a discrete event simulation model. The design of the simulation model is at the subdivision level and provides a mechanism through which a critical analysis of the process can be performed and waste due to inefficiencies can be identified. The simulation model has been developed in SLAM-II. Input data for the simulation model was obtained from municipal jurisdictions within the Phoenix metropolitan area. Key output parameters include inspection failure rates, impact of failure rates on the production cycle time, and impact of inspection failure on resources provided by individual stakeholders. Even though the model is developed at a subdivision level its results can be extrapolated at the city level and broad conclusions can be drawn.

Petri Net-based scheduling of construction projects

Scheduling of construction projects is an important planning function that provides a clear picture of the construction activities, construction sequence, and construction resources to the agencies involved in construction. In this paper a Petri Net-based scheduling method that is geared towards resource-based scheduling of construction projects is described. Petri Nets are graphical and mathematical modeling tools that can be used to perform static and dynamic analysis of systems. Under the proposed technique Generalized Stochastic Petri Net (GSPN) modeling elements are used to develop a construction schedule. Resources required to accomplish construction work tasks are explicitly identified and allocated to the corresponding work tasks. In addition the technique provides hierarchical features that allow top–down breakdown of a construction project and modular features to schedule repetitive units. The paper summarizes the steps required to perform scheduling of construction projects using the proposed technique and highlights its advantages. The scheduling of a sample bridge project also highlights the significant benefits of the method.

Java-based simulation of construction processes using Silk

The modeling and analysis of construction processes is gaining recognition in the construction industry. Recent developments, such as object-oriented modeling, Petri net-based simulation and construction project-level simulation, are being adopted by researchers in the field of construction simulation. This paper describes one such recent development. It highlights the work performed by the authors in using Java for the simulation of construction processes. The methodology used, the simulation toolkit adopted (Silk) and the construction process simulated are described.

Simulation of the structural steel erection process

The construction industrys growth and the adoption of newer means, methods, and materials of construction have resulted in an increase in complexity of on-site construction processes. Consequently, the construction industrys need for advanced tools and techniques to study, plan, and manage these complex construction processes has developed. The paper illustrates a Petri net based hierarchical and modular modeling and analysis technique that can be used for simulation of complex construction processes. Through the use of hierarchy, modularity, and resource modeling, Petri nets provide clear advantages in the modeling of complex construction processes. The paper highlights the advanced features of Petri nets and their utilization in the modeling and analysis of a structural steel erection process.

RESIDENTIAL CONSTRUCTION AND THE INFLUENCE OF INSPECTIONS ON CYCLE TIME

A key component of the homebuilding process is inspection of construction by the building permitting agency within the jurisdiction where the work is performed. Several inspections are made throughout the construction process, but four of the inspections, pre-slab, framing, drywall, and final, lie on the work schedule critical path. This research focuses upon these particular inspections to determine if the inspection failures influence construction cycle time. Inspections of production homes are examined to determine how often these critical path inspections do not pass the first time, and how many reinspections are required. The number of days utilized to pass those inspections and reinspections is also measured and reported. The research finds that, on average, 12 days are required, to pass these critical path inspections, thus adding 8 days to the construction cycle time. When these inspections do not pass the first time the inspection is made, rework and reinspections must be completed before construction can proceed. The results show that this process may occur within the same day as the original inspection, and the subsequent inspection takes place the next day. More research is necessary to determine precisely wh y these inspection failures occur, what cost is incurred because of such failures, and in turn, what opportunities are lost.