Climatic Effects on Construction

The results of an investigation designed to determine the relationship between overall construction productivity, and temperature and humidity are presented. Data from the following activities or crafts, or both, were employed: excavation (manual), erection, masonry, electrocal, carpentry, laborers, and excavation (equipment). Two nonlinear equations were determined, one for cold or cool weather (R2? = ?0.62) and another for hot or warm weather (R2? = ?0.64). The overall findings indicate that below ?10?°F and above 110?°F it is difficult to achieve efficient construction operations. In addition to productivity data, the health hazards, possible preventive measures, and acclimatization of workers to severe environments are examined.     

Process Model Perspectives on Management and Engineering Procedures in the Precast/Prestressed Concrete Industry

The preparation of detailed models of information and process flow by 14 member companies of the North American Precast Concrete Software Consortium has provided a unique window into the current management, engineering design, and production operations in this industry. The modeling was performed using the authors’ Georgia Tech Process for Product Modeling tool, within the framework of the consortium’s effort to develop a precast concrete product model and to specify new integrated three dimensional modeling software. The paper opens with a comparative economic review of precast construction internationally and in North America, which reveals that the market share of precast construction in North American is relatively low. The models are analyzed and aspects of the underlying management procedures that they reveal are discussed, such as types of contracting arrangements, cost estimating, design outsourcing, engineering design communication, mold design, product diversity, and quality control. The results highlight aspects of precast management processes that may be re-engineered through appropriate application of information technology.     

Innovations in Nuclear Concrete Construction

The technical requirements and scope of concrete work on nuclear projects present significant engineering and construction challenges. These demands represent the extremes in many areas of construction operations. In meeting these challenges, engineering and construction forces have developed several innovations which can be beneficially applied to other types of construction. Innovative approaches in the general categories of engineering scope, construction input to engineering, work planning, special methods and techniques, and satisfaction of quality assurance requirements are given in this paper. The transfer of this technology to other segments of the construction industry will improve overall performance by avoiding the problem areas encountered on nuclear projects.     

混凝土工程施工质量控制方法分析

混凝土工程施工质量的好坏,直接关系到整个建筑物的安危和寿命。本文结合混凝土工程的施工工艺,分析了混凝土工程施工质量控制方法。     

浅谈混凝土工程冬季施工技术

严格控制混凝土拌合时间和坍落度，降低配合比中的用水量，避免混凝土产生早期冻害，并尽量缩短运输时间和距离，加快浇筑速度，防止热量散失过多，采取相应的保温保湿措施，以保证混凝土强度。     

Temporary Heating in Construction Contracts

It appears that in construction projects extending through winter with freezing temperatures, the cost of temporary heating is not always equitably resolved between the parties in a contract. Although existing guidelines have been initiated since 1964 by the construction industry, the bid allowances in calendar days and cost perdiem of heating, as suggested, have not been implemented. The three case studies described with varying structures and heating systems, show how heating costs are affected by changes beyond the General Contractor's control. These costs can be substantial; however, they can be minimized if owner, designer, contractor and mechanical subcontractor can cooperate.     

Drivers for Cost Estimating in Early Design: Case Study of Residential Construction

This paper proposes the use of a series of independent variables for an early estimation of the building construction cost of residential buildings. Based on 70 German residential properties, these variables serve as the cost drivers of a project, and the regression model, tested against the 70 properties, has a mean absolute percentage error of 9.6%. When applied to predict the cost of five more properties that were excluded from the 70 in the regression model, the percentage error ranges between–12 and 13%. The identified cost drivers are: compactness of the building, number of elevators, size of the project, expected duration of construction, proportion of openings in external walls, and region.     

Success of Supplier Alliances for Capital Projects

Energy sector capital projects typically cost hundreds of millions and even billions of dollars. Managing the engineered equipment is important not only because of their high dollar value but also because the long manufacturing lead times often drive the overall project schedules. In recent years, several supplier alliances have been successfully implemented on such projects leading to initial price savings in the range from 6 to 10%. This paper presents the result of a study to assess the opportunities and barriers with such partnerships. Interviewed company executives perceived that time savings and quality improvements, mostly due to the suppliers’ specialized expertise, are of much greater value than a lower bid price. Most surprisingly, very few companies use metrics to measure performance, thus leaving them in the dark on the question of how well an alliance worked or why it failed. The relevance of the presented work is in the amount of actual field data that has been generated and processed.     

Development of a Methodology for Live Capture and Reuse of Project Knowledge in Construction

The efforts to share and reuse knowledge generated on construction projects are undermined mainly by the loss of important insights and knowledge due to the time lapse in capturing the knowledge, staff turnover, and people’s reluctance to share knowledge. To address this, it is crucial for knowledge to be captured “live” in a collaborative environment while the project is being executed and presented in a format that will facilitate its reuse during and after the project. This paper uses a case study approach to investigate the end-users’ requirements for a methodology for the live capture and reuse of knowledge, and the shortcomings of current practice in meeting these requirements. A methodology for the live capture and reuse of project knowledge is then presented and discussed. The methodology, which comprises a web-based knowledge base, an integrated work-flow system and a project knowledge manager as the administrator, allows project knowledge to be captured live from ongoing projects. This also incorporates mechanisms to hasten knowledge validation and the dissemination of the knowledge once it has been validated.     

Fundamental Principles of Workforce Management

This paper was written to fill a void created by the absence of fundamental principles of site construction management. Efficient workforce utilization is essential to managing a productive and cost efficient site. For more than 25?years, the senior author has been observing and writing about inefficient labor productivity practices resulting from poor site management practices. Using deductive reasoning, fundamental principles were developed to avoid poor practices. General and fundamental principles related to performance measures and daily work schedules are cited. Additional principles are cited in the categories of work assignments, crew structure, disruptions, multiskilling, preassemblies and modules, and symbiotic crew relationships. The principles have been intentionally left general so as to apply to a broad range of situations.     

Characterization of Laser Scanners and Algorithms for Detecting Flatness Defects on Concrete Surfaces

In many construction and infrastructure management projects, it is important to ensure the flatness of concrete surfaces. Inspectors assess the quality of flat surface construction by checking whether a surface deviates from perfectly flat by more than a specified tolerance. Current flatness assessment methods, such as using a straightedge or shape profiler, are limited in the speed or density of their measurements. Laser scanners are general-purpose instruments for densely and accurately measuring three-dimensional shapes. In this paper, we show how laser scanners can be effectively used to assess surface flatness. Specifically, we formalize, implement, and validate three algorithms for processing laser-scanned data to detect surface flatness deviations. Since different scanners and algorithms can perform differently, we define an evaluation framework for objectively evaluating the performance of different algorithms and scanners. Using this framework, we analyze and compare the performance of the three algorithms using data from three laser scanners. The results show that it is possible to detect surface flatness defects as small as 3 cm across and 1 mm thick from a distance of 20 m.     

Risk-Based Safety Impact Assessment Methodology for Underground Construction Projects in Korea

Safety of construction projects may be affected by various factors such as types and scale of projects, construction methods, safety management procedure, climate, site conditions, etc. Among them is the quality of design in relation to safety. Presently, however, designers typically are not involved in construction safety. They are often uncertain of their responsibilities in relation to construction safety and fail to be responsible for avoiding or reducing safety-related risks. In this study, the concept of safety impact assessment to achieve “design-for-safety” in the design phase is introduced. For this purpose, a safety impact assessment model was devised, and a methodology using the risk-based safety impact assessment approach for open-cut type underground construction projects in Korea is suggested. The suggested methodology includes a safety information survey, classification of safety impact factors caused by design and construction, and quantitative estimation of magnitude and frequency of safety impact factors. A checklist which can be easily used for assessing the safety performance of design products is also proposed. A real-world case study on the safety impact assessment of a subway construction project in Korea is also provided in the paper.     

Fundamental Principles of Site Material Management

This paper was written to fill a void created by the absence of fundamental principles of site construction management. Efficient material management is essential to managing a productive and cost efficient site. For more than 25?years, the senior author has been observing and writing about inefficient labor productivity practices resulting from poor site material management. Using deductive reasoning, fundamental principles were developed to avoid poor practices. A construction site should be portioned into three areas or zones: semipermanent (exterior) storage, staging areas, and workface (interior) storage. Each has a unique function relative to site material management. Using these areas as a framework, fundamental principles are stated and illustrated using a case study project accompanied by numerous photographs and narratives.     

谈谈钢铁厂大型设备基础-混凝土的施工温度与裂缝

通过多年的现场观察，结合查阅有关混凝土内部应力方面的专著，对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施等进行深入的阐述。指出引起裂缝的原因主要是温度和湿度变化等。并提出采取防止裂缝的相应措施。主要改善内部和外部约束条件。     

Predicting Cost Deviation in Reconstruction Projects: Artificial Neural Networks versus Regression

This paper investigates the challenging environment of reconstruction projects and describes the development of a predictive model of cost deviation in such high-risk projects. Based on a survey of construction professionals, information was obtained on the reasons behind cost overruns and poor quality from 50 reconstruction projects. For each project, the specific techniques used for project control were reported along with the actual cost deviation from planned values. Two indicators of cost deviation are used in this study: cost overrun to the owner, and the cost of rework to the contractor. Based on the information obtained, 36 factors were identified as having direct impact on the cost performance of reconstruction projects. Two techniques were then used to develop models for predicting cost deviation: statistical analysis, and artificial neural networks (ANNs). While both models had similar accuracy, the ANN model is more sensitive to a larger number of variables. Overall, this study contributes to a better understanding of the reasons for cost deviation in reconstruction projects and provides a decision support tool to quantify that deviation.     

Games People Play with Cost Control in Australia

A study of a selected group of building and engineering construction contractors in the Australian construction industry was performed in order to determine the actual site cost control procedures and techniques being practiced. The study was conducted through a detailed questionnaire completed by the researcher during the course of interview sessions with the site managers of the 18 construction projects in the sample. The main trends disclosed from the questionnaire allowed a model of actual site cost control procedures to be flowcharted. This system was then subjected to a comparative analysis with an idealized site cost control system developed in a previous study. Cost control functions that are discussed in this paper include, among others, the method of work breakdown for site use in cost control, performance data feedback techniques and uses, yardsticks for cost control, and management action at the site. The study concludes with a set of general recommendations aimed to bring current site cost control practices more in line with the available body of knowledge.     

Improving Cost Estimates of Construction Projects Using Phased Cost Factors

Central to cost-based competition is the capability to accurately predict the cost of delivering a project. Most literature on cost estimation focuses on specific estimation methods as generic techniques and little attention has been paid to the unique requirements at each project stage. This note attempts to identify the critical factors for effective estimation at various stages of typical construction projects. Drawing from organization control theory and cost estimating literature, this note develops a theoretical framework that identifies the critical factors for effective cost estimation during each project phase of a conventional construction project. The underlying logic is that as a cost estimating effort progresses, both task programmability and output measurability improve. As a result, control effort will shift from input-oriented control to a combination of output and behavior control.     

Estimation of Minimum Working Capital for Construction Projects in Malaysia

Forecasting cash requirements is essential for all contractors during the tendering stage since cash flow at the beginning of the project is a major cause of construction companies’ failure. Unfortunately, estimating minimum working capital (MWC) is not the mainstream practice of the majority of contractors in Malaysia, who find that the present models for estimating MWC are cumbersome and seldom give an accurate estimate. Therefore estimates of MWC made during the tendering stage need to be simplified so they can be prepared quickly with minimum input. It is important for the developer or owner to select a qualified contractor with competent financial backing. This paper establishes the relationship among the factors that contribute to MWC requirements and presents a simple model that could be used as a guide to estimate MWC for housing construction projects in Malaysia. The estimation is based on percentages of variables of contract value based on the historical data that influence MWC; the MWC obtained is then expressed in terms of percentage of contract value.     

Testing of Minimization of Subjectivity in Best Value Procurement by Using Artificial Intelligence Systems in State of Utah Procurement

The Performance Information Procurement System (PIPS) was tested on the procurement of the $2.96 million Bridgerland Academic Training Center (ATC) for the state of Utah Division of Facilities Construction Management. The artificial intelligence (AI) information based PIPS was run two ways—selection with biased subjectivity (similar to current best value processes) and without biased subjectivity. Unlike other best value processes, PIPS minimizes the decision-making and subjective bias of the owner’s representatives. The procurement test at Bridgerland ATC provides a comparison between the AI selection versus the user agency’s subjective prioritization. The result of the system was one of the “best” construction projects procured at the state of Utah (on time, on budget, high quality), with no contractor generated change orders for additional cost, minimized construction management requirements, and high customer satisfaction.