Improved Subcontractor Selection Employing Partnering Principles

Despite the increasing extent of subcontracting in construction, the importance of subcontractor selection is frequently underestimated. While the subcontracting element needs more attention in contractor selection itself, subcontractor selection techniques themselves need considerable improvements. This paper examines how such techniques can beneficially draw from improved multicriteria contractor selection methodologies in general, and specifically from recent developments in client-contractor partnering. It is shown how partnering may be profitably extended further into the supply chain, i.e., into subcontractor selection. A European case study illustrates the development of a subcontractor selection process that incorporated partnering principles. Despite the longer and costlier selection process, it was found that subcontractor pricing levels were reduced by about 10% to account for anticipated efficiencies arising from the proposed partnering. Markedly better time and cost control was achieved on the pilot project. The relationships between all project participants were also found to have improved considerably. Such observations confirm the value (1) of expanding the partnering “envelope” to encompass subcontractors in general; and more specifically, (2) of assessing the potential for such extended partnering as an integral part of the subcontractor selection process.     

Subcontractor Evaluation and Management Framework for Strategic Partnering

Recently, main contractors have shifted their attitudes about subcontract procurement to more strategic and long-term partnering philosophies. The objective of this study was to present a framework for subcontractor evaluation and management to help main contractors develop more strategic and productive relationships with their subcontract partners. As the strategic performance feedback model, the balanced scorecard concept was adopted with modification. A case study was also conducted to evaluate the framework with subcontracting strategy, performance indexes, weighting, evaluation of subcontractor performance data, and feedback methods. The research results obtained can be useful as a guideline of subcontractor management for long-term partnering and also to enhance overall productivity within the construction supply chain.     

Cancer mortality among atomic bomb survivors exposed in utero or as young children, October 1950-May 1992

Improvements in workplace health among silica exposed workers followed demonstrations of the severity of the risk of silicosis and means of controlling high dust levels on the job. Current ambient environmental analyses include either an adoption of air quality goals for reducing emissions of criteria pollutants or the conduct of risk assessments to determine if regulatory procedures are needed. Although silica has been regulated as a workplace hazard for most of the 20th century, only recently has it been considered for ambient control, and most of the thrust for this action has evolved from environmental regulatory work in California, where both state initiative (Proposition 65) and legislative law (Air Toxics Hot Spots Information and Assessment Act; Assembly Bill number 2588) have required risk assessments for silica dust emissions as carcinogens.     

Agent-Based Compensatory Negotiation Methodology to Facilitate Distributed Coordination of Project Schedule Changes

Change is ubiquitous in construction project schedules and there are many interrelationships and interdependencies in project schedule changes. Therefore, a schedule change in the work of a subcontractor might affect schedules of other subcontractors, as well as the project deadline. The subcontractor should resolve schedule conflicts with other affected subcontractors. This implies that there is a need for a methodology for the distributed coordination of project schedule changes (DCPSC). This paper presents a novel agent-based compensatory negotiation methodology to facilitate the DCPSC wherein a project can be rescheduled dynamically through negotiations by all of the concerned subcontractors. The methodology consists of a compensatory negotiation strategy based on utility of timing, multilinked negotiation protocols, and message-handling mechanisms. A simple case example illustrates the methodology. The methodology makes new contributions in both theoretical and practical areas. In practice, this methodology will improve project network schedules, by lowering the sum of the cost of the subcontractors associated with their resource constraints. In theory, the methodology provides a distributed coordination methodology that can improve interaction and collaboration among agents and people.     

Case-Based Reasoning Approach to Construction Safety Hazard Identification: Adaptation and Utilization

Risk assessment, consisting of hazard identification and risk analysis, is an important process that can prevent costly incidents. However, due to operational pressures and lack of construction experience, risk assessments are frequently poorly conducted. In order to improve the quality of risk assessments in the construction industry, it is important to explore the use of artificial intelligence methods to ensure that the process is efficient and at the same time thorough. This paper describes the adaptation process of a case-based reasoning (CBR) approach for construction safety hazard identification. The CBR approach aims to utilize past knowledge in the form of past hazard identification and incident cases to improve the efficiency and quality of new hazard identification. The overall approach and retrieval mechanism are described in earlier papers. This paper is focused on the adaptation process for hazard identification. Using the proposed CBR approach, for a new work scenario (the input case), a most relevant hazard identification tree and a set of incident cases will be retrieved to facilitate hazard identification. However, not all information contained in these cases are relevant. Thus, less relevant information has to be pruned off and all the retrieved information has to be integrated into a hazard identification tree. The proposed adaptation is conducted in three steps: (1) pruning of the retrieved hazard identification tree; (2) pruning of the incident cases; and (3) insertion of incident cases into the hazard identification tree. The adaptation process is based on the calculation of similarity scores of indexes. A case study based on actual hazard identifications and incident cases is used to validate the feasibility of the proposed adaptation techniques.     

Proposed Subcontractor-Based Employee Motivational Model

The intent of this research was to identify the factors that promote positive motivational behavior in construction subcontractor crews. The factors affecting motivation, goal-setting, workforce needs, and incentives were investigated to determine the attributes for a subcontractor employee motivational model. A survey addressing these four categories was distributed to subcontractor foremen and supervisors to establish a list of motivational factors. The statistical analysis of the survey results aided in the final development of the proposed subcontractor based employee motivational model, which includes such components as confidence and competence as being reinforced by quality of work, incentives, safe performance, praise, and a sense of belonging. The proposed model provides industry practitioners with another level of understanding of the motivation sequence of the subcontractor’s labor force. Perhaps the most interesting finding was related to the attributes found in relation to workforce needs. A common link “feeling of being a member of the team/crew” was discovered between “praise” and “job security.” It was surmised that essentially a worker must first receive praise before they feel as if they are a member of the team/crew and once they feel like a member of the team, they then begin to acquire feelings of job security. The results of this study further reinforce the findings of several previous behavioral studies. Future research should attempt to validate the model using a larger sample size incorporating multiple general contractors.     

Relative Importance of Subcontractor Selection Criteria: Evidence from Singapore

Subcontractors carry out a large portion of the work done in construction projects. Thus, selecting the right subcontractor essentially contributes to the project’s success. We designed a choice-based conjoint experiment to examine the relative importance of four criteria in the subcontractor selection process of main contractors from Singapore: price, technical know-how, quality, and cooperation. Although main contractors adopt a multicriteria selection process and perceive all four criteria to be important for their choice decision, the actual choice situation reveals that price is still by far the most important selection criterion, followed by quality, cooperation, and technical know-how. Main contractors are not willing to compromise on price but accept a lower performance of a known subcontractor on the remaining criteria.     

Safety Hazard Identification on Construction Projects

Hazard identification is fundamental to construction safety management; unidentified hazards present the most unmanageable risks. This paper presents an investigation indicating the current levels of hazard identification on three U.K. construction projects. A maximum of only 6.7% of the method statements analyzed on these projects managed to identify all of the hazards that should have been identified, based upon current knowledge. Maximum hazard identification levels were found to be 0.899 (89.9%) for a construction project within the nuclear industry, 0.728 (72.8%) for a project within the railway industry, and 0.665 (66.5%) for a project within both the railway and general construction industry sector. The results indicate that hazard identification levels are far from ideal. A discussion on the reasons for low hazard identification levels indicates key barriers. This leads to the presentation of an Information Technology (IT) tool for construction project safety management (Total-Safety) and, in particular, a module within Total-Safety designed to help construction personnel develop method statements with improved levels of hazard identification.     

Control of exposure to airborne viable microorganisms during remediation of moldy buildings; report of three case studies

Three different techniques for reducing exposure to microorganisms were tested during remediation of moldy buildings. Concentrations of spores (fungi and actinomycetes) were determined by filter sampling before, during, and after remediation. The local exhaust method used for asbestos dismantling was the most effective control method. In the construction zone, concentrations of microorganisms were 4-25 times higher during remediation than before it. In the adjacent area no increase in concentrations was seen. When the construction zone was placed under negative pressure with a fan and isolated with a plastic barrier, concentrations of microorganisms were about 100 times higher there during remediation work. Nevertheless, levels remained low in the adjacent area. The use of a portable exhaust fan with a side-draft hood decreased concentrations of fungi to one-tenth compared with demolition without the control technology. Furthermore, this method prevented the migration of fungal spores from the construction zone to the adjacent area, although it was less effective in prevention of actinomycete spore migration. It also decreased the levels of microorganisms in the construction zone below the preconstruction level within 2 hours. This study showed that levels of airborne microorganisms, including from the working area to adjacent area, can be reduced with commonly used dust control methods during demolition work. However, microorganism levels in the construction zone remained elevated. Therefore, personal protection of construction workers is needed even with control techniques.     

Airborne Particles in New Museum Facilities

Over the period July 1996–April 1998, airborne particle concentrations and chemical composition were measured both inside and outside the new J. Paul Getty Museum outside Los Angeles. The purpose of these experiments was to determine the relationship between the stages of construction and operation of the building and the soiling hazard to the collections. Particular attention was paid to tracking the concentrations of fine black soot particles and mineral dust particles. The time needed to “air out” the building following construction can be seen from the data collected, as well as the inherent particle removal efficiency of the filters within the building ventilation system, and the effect of entry of the general public into the building. During the period of observation when the building was under construction, weekday coarse dust particle concentrations on occasion reached very high levels (600–1,100?μg?m?3; 24 h average), falling to relatively low values averaging 26?μg?m?3 over weekend periods when construction activity subsided. In March, 1997, with construction largely completed and with the heating, ventilation, and air conditioning (HVAC) system in full operation, indoor coarse dust concentrations fell to 1.7% of those outdoors. Beginning at this time, indoor fine particle concentrations relative to those outdoors declined steadily over a period of about one to two months, reaching levels of 3.9% of those outdoors during the period June 3–December 6, 1997 when construction was completed but before entry of the general public into the building. Thus, the coarse and fine particle removal efficiencies of the building HVAC system absent major indoor sources are at least 98 and 96%, respectively. Following the opening of the museum to the public, indoor particle concentrations increased by approximately 1?μg?m?3 in each of the coarse dust and fine smoke-size particle size ranges indicating that there is a small but measurable effect due to increased air infiltration as doors are opened and closed more frequently and due to particles shed by the visitors. Indoor particle concentrations inside the new Getty Museum in the presence of the general public are only 3.2?μg?m?3 of coarse dust and 1.8?μg?m?3 of fine particles on average over the period January–April, 1998.     

On-Site Subcontractor Evaluation Method Based on Lean Principles and Partnering Practices

Subcontracting has greatly increased in the construction industry. It helps shift risk from the main contractor to the subcontractor and promotes specialization. Inadequate subcontracting management, however, may result in an adversarial relationship between main contractors and their subcontractors, uncoordinated on-site execution, and disappointing quality and schedule fulfillment. New subcontractor management methods and tools are being developed and tested as part of a collaborative research project led by the Catholic University Production Management Center with the participation of the Chilean Construction Chamber and several construction companies. The experience gained by testing prototype tools and methods on selected projects enabled us to develop an on-site evaluation method based on lean principles and partnering practices. This method allows main contractors to help subcontractors improve their performance by providing them with periodic feedback. It also supports subcontractor selection based on their previous performance, which helps foster collaborative relationships with those that consistently perform well. The results of the application of the method in two case studies are discussed.     

Dust Suppression Using Truck-Mounted Water Spray System

The control of dust on construction sites is an issue of concern of many communities that experience a high level of construction activity. Dust suppression typically involves using large water trucks to spray haul roads, material stockpiles, and other areas being worked by equipment. This method of dust control leads to labor, operating, and safety costs and complications that can limit and sometimes prohibit its implementation. Other spray methods that are cost-effective, easy to implement, functionally viable, and safe are needed that provide direct and effective dust control for each piece of equipment. This paper describes a research project to develop and evaluate a water spray system for suppressing dust emissions that is attached directly to a piece of earthmoving equipment, specifically a dump truck. The system consists of distribution hose, pipe, and spray nozzles attached to the perimeter of the truck body, and a water pump and water tank secured to the truck's frame. The system's design takes into account various operational and performance factors, including water consumption rate, spray configuration, equipment function and operation, dust suppression effectiveness, and cost of installation and use. It is expected that the system developed can play an effective role in minimizing dust emissions from construction sites.     

Modeling the Behavior of Fiber Reinforced Polymer-Confined Concrete Columns Exposed to Fire

Very little information is available on the behavior of fiber reinforced polymer (FRP) materials and FRP-strengthened concrete members in fire, and this is a primary factor hindering the widespread implementation of FRP strengthening technologies in the construction industry. This paper presents a numerical model for evaluating the fire behavior of conventionally reinforced circular concrete columns, FRP-wrapped reinforced concrete columns, and insulated FRP-wrapped reinforced concrete columns. The model is validated against data available in the literature from full-scale fire endurance tests on conventionally reinforced concrete columns, and preliminary predictions of the model are presented and discussed. It is demonstrated that the model agrees reasonably well with experimental data obtained from tests on circular reinforced concrete columns, that it is unlikely that the structural effectiveness of FRP materials can be maintained during fire, and that the fire behavior of FRP-wrapped columns can be dramatically improved by providing supplemental insulation for the FRP.     

Practical Issues for the Application of High-Performance Concrete to Highway Structures

In recent years, the advantages of high-performance concrete (HPC) have been well documented. Among others, these advantages include enhanced design flexibility and improved durability performance that results in reduced maintenance costs and an increased service life. Despite these obvious benefits, the implementation of HPC has been very slow. This can be attributed to several factors including the uncertainty related to current design codes and a lack of familiarity of designers and contractors with practices and requirements for proper design and construction of high-performance concrete structures. This paper introduces and discusses several fundamental issues that affect the implementation of HPC and impact the practitioner. These include issues related to quality control∕quality assurance, specifications, material performance, and structural behavior. Within the scope of this discussion, the fundamental differences and similarities between HPC and conventional concrete are discussed. The objective of this discussion is to provide the practicing engineer with a conceptual understanding of the practical issues that affect the design and use of HPC for highway structures with the desire to further stimulate the implementation of HPC.     

Field Experiments to Evaluate and Control Light Tower Glare in Nighttime Work Zones

An increasing volume of highway repair and construction work is being performed during the off-peak nighttime hours to mitigate the impact of construction-related daytime traffic congestions and shorten the duration of construction operations. The utilization and placement of light towers to illuminate the work zone in this type of construction can cause harmful levels of glare for both drivers and construction workers. This paper presents the results of field experiments which were conducted to (1) study the levels of glare and lighting performance generated by light towers in and around nighttime work zones; (2) analyze the combined impact of the light tower set up parameters including its height as well as its aiming and rotation angles on glare and lighting performance; and (3) provide practical recommendations to reduce and control lighting glare in and around nighttime work zones. The results of these experiments confirm that the set up of light towers has a significant impact on glare and therefore it should be carefully designed and executed on nighttime highway construction projects to ensure the safety of the traveling public as well as construction workers.     

Whole Life Performance Assessment: Critical Success Factors

Whole life costing (WLC) has become the best practice in construction procurement and it is likely to be a major issue in predicting whole life costs of a construction project accurately. However, different expectations from different organizations throughout a project’s life and the lack of data, monitoring targets, and long-term interest for many key players are obstacles to be overcome if WLC is to be implemented. A questionnaire survey was undertaken to investigate a set of ten common factors and 188 individual factors. These were grouped into eight critical categories (project scope, time, cost, quality, contract/administration, human resource, risk, and health and safety) by project phase, as perceived by the clients, contractors and subcontractors in order to identify critical success factors for whole life performance assessment (WLPA). Using a relative importance index, the top ten critical factors for each category, from the perspective of project participants, were analyzed and ranked. Their agreement on those categories and factors were analyzed using Spearman’s rank correlation. All participants identify “Type of Project” as the most common critical factor in the eight categories for WLPA. Using the relative index ranking technique and weighted average methods, it was found that the most critical individual factors in each category were: “clarity of contract” (scope); “fixed construction period” (time); “precise project budget estimate” (cost); “material quality” (quality); “mutual/trusting relationships” (contract/administration); “leadership/team management” (human resource); and “management of work safety on site” (health and safety). There was relatively a high agreement on these categories among all participants. Obviously, with 80 critical factors of WLPA, there is a stronger positive relationship between client and contactor rather than contractor and subcontractor, client and subcontractor. Putting these critical factors into a criteria matrix can facilitate an initial framework of WLPA in order to aid decision making in the public sector in South Korea for evaluation/selection process of a construction project at the bid stage.     

A study of the performance and comparability of the sampling response to cotton dust of work area and personal sampling techniques

In order to compare and contrast the sampling response to cotton dust of two forms of dust sampling 85 work areas were identified over a 2-year period for investigation in eight Lancashire spinning mills. Three hundred and five work area dust samples were undertaken and 252 personal dust samples were performed. Operatives who spent a minimum of 80% of their working shift in the area in which work area sampling was also performed were selected for personal sampling. Work area dust exposures have recently shown an upward trend, with highest concentrations occurring in the ring spinning room (median 1.15 mg m-3, range 0.82-2.06). Personal dust samples showed a reduction in dust exposures as cotton processing progressed, from a high in the opening room (median value of 6.24 mg m-3, range 1.0-41.5) to a minimum of 1.02 mg m-3 (range 0.30-0.93) in the winding room. The ratio of measured personal sampling dust exposure to work area sampling exposure was used to compare the relative performance of the two techniques. This ratio was highest in the early processes. There was a 7.8-fold difference in measurement between the two techniques in the opening processes, falling to 4.9 in carding and 4.2 in the other card-room processes. However in ring spinning the ratio was only 1.4, suggesting a degree of comparability in the methods at this stage of processing. The value rose to 2.5 for the last stage (winding). Respiratory disease is known to occur predominantly in the early stages of processing (opening and carding) where high dust concentrations are found using the personal technique. These data support the use of personal sampling for setting exposure limits to cotton dust in preference to the current recommended method using work area sampling techniques, which may significantly underestimate dust exposure in the high risk work areas and is outdated.     

Issues in Subcontracting Practice

Subcontractors are very important to the successful completion of most construction projects, yet the many issues involved in subcontracting practice are seldom acknowledged. A literature review indicates that these issues include the timeliness of payments by general contractors, the process of selecting subcontractors, subcontractor bonding, construction insurance, safety issues on the construction site, partnering arrangements with various parties, and productivity issues. A questionnaire survey was administered to subcontractors, general contractors, and construction owners to investigate these issues and to determine the differences in perceptions between the parties. The results confirm the existence of the issues identified in the literature and in addition indicate that (1) the practice of retainage withheld by general contractors seems to be acceptable to many subcontractors unless its magnitude is large relative to the size of the firm; (2) postaward bid shopping by general contractors is sometimes justified, particularly in cases where the scope of subcontract work is modified; and (3) current bonding and insurance practices are adequate unless the additional transferred risks are excessive. Recommendations are made on the basis of the findings to minimize the negative effects of said issues.     

Modeling Interfirm Dependency: Game Theoretic Simulation to Examine the Holdup Problem in Project Networks

Subcontractor selection strategies used by contractors can significantly affect short-term project and long-term organizational success. Existing research on subcontractor selection strategy implicitly assumes that the evaluation of subcontractors depends on current conditions. We extend this perspective by integrating an agent-based simulation model with game theory to examine whether precontract partner selection strategies that do not consider subcontractor selection as a repeated game may lead to a version of the holdup problem. The holdup problem we investigate focuses on relationship-specific investments in learning after the introduction of an innovation or organizational change across a project network. A minimum total cost strategy may decelerate the rate of adaptation to an innovation or organizational change, thereby proving that the holdup problem can exist in project networks. The findings contribute to subcontractor selection strategy literature by simulating the impact of the holdup problem in project networks, distinguishing task interdependence as a moderating variable, and identifying that the minimum total cost strategy can be a suboptimal strategy for project networks adapting to systemic changes.