Journal of Construction Engineering and Management

One expression of the renewed attention gained recently by formwork for concrete is the current revision of formwork standards. This paper presents the new Israeli formwork standard as a case study for contemporary trends in formwork standardization. The main novelty in the new standard is its similar treatment of the design of temporary structures to that of permanent structures, resulting in the replacement of the traditional allowable-stress approach with the concept of limit-state design and partial safety factors. The paper presents this concept and discusses its applicability to formwork design. In addition, the paper highlights several other issues of a contemporary nature, which appear to be worth debate by standardization committee members from the industry and academia. In the course of the preparation of the new Israeli standard, American, European, and Australian standards and similar documents were closely studied; some comparisons of design and loading data that may affect construction safety and economy are also presented in this paper.

Trenchless technology is an emerging area of construction involving innovative methods, materials, and equipment used for the installation of new and the rehabilitation or replacement of existing underground infrastructure with minimal or no need for open cut excavation. This technology provides an alternative to traditional methods of open trenching construction, which is often associated with major disruptions to surface activities. The results of a survey of trenchless construction methods in Canada are presented in this paper. The survey, which was sent to 87 municipalities across Canada, provides an indication of current and future trends in the application of trenchless construction technologies in the municipal arena including type and frequency of technologies employed, percentage of projects that employed trenchless technologies, and contractor selection methods. The survey results indicate that trenchless technology is gaining increasing popularity among municipal engineers across Canada. The percentage of all municipal projects utilizing trenchless construction methods has grown over the past 5 years by 180% (new construction) and 270% (rehabilitation). The survey also revealed that the typical Canadian municipality spends $29.68/capita on new construction of municipal service lines and $18.21/capita on rehabilitation of existing lines.

Time series analysis is a powerful statistical tool that can be of great value in evaluating the results of experiments to improve construction productivity. Time series analysis explicitly recognizes the importance of the order in which experimental data are observed, and the statistical dependence of observed data. This paper presents a brief overview of time series analysis and demonstrates its application using previously published data for a series of experiments involving crane lift cycle durations. In one experiment, it was shown that despite no apparent change in productivity, a new technology changed the nature of the work operation. In another experiment, a change in productivity was observed, but little change to the overall operation was seen. In a third experiment, a large change in the complexity of the operation can be seen as well as a clear learning effect. The underlying changes are due to differences in disturbances to the overall operation. These nonproductivity changes may be of great interest to the researcher, but they would not be identified using conventional productivity comparison techniques.

The identification and analysis of compensable delays become necessary on most construction projects. Although there are several different analytical techniques available, the window method of contemporaneously analyzing delays is the most realistic. The reasons for the superiority of the window method are discussed. The possible results of a window analysis are evaluated and graphically presented. Also discussed are a correction, or intermediate step, in the method, necessary to avoid incorrect findings of false concurrency, and the proper method for handling apportionable and nonapportionable delays. Finally, an argument is made that the burden of proving noncompensable delays, assuming a proper window analysis of compensable delays by a contractor, should be borne by the owner.

This paper is the result of an investigation into the use of contingency in smaller construction firms. It summarizes recent literature classifying construction contract risks and mitigation measures. Eight major classifications are used to organize the types of risk found in the literature. The risks are described in detail with associated risk mitigation strategies. Risk modeling techniques are briefly reviewed for their contribution to the risk categorization and contingency estimating. After reviewing the researcher's concepts of risk management in the literature, interviews were conducted with estimators and/or construction managers involved in the bidding process at 12 small to medium construction firms. The purpose of the interviews was to investigate the current risk management practices of small and medium size construction firms. The times when smaller companies used contingency had specific interest for the research. The literature findings were compared with important risk factors identified from the interviews. The main conclusion drawn from the comparison was that small to medium size contractors predominately use contingency in those situations where they are construction managers in a reimbursable contract. Generally, they do not use line item contingency in competitive bidding situations. Thus, these firms are assuming proportionally greater business risk than suggested by the literature on contingency.

Overexertion injuries are the single largest classification of injury in construction, accounting for about 24% of all injuries. Overexertion injuries generally occur as a result of performing a given task as planned. While overexertion injuries are not intentional, the underlying causes of these injuries are built into the prescribed tools and work methods. If the causes can be identified, it should be possible to engineer them out of the work. This paper presents a summary of research to investigate 65 construction activities for the presence of risk factors for overexertion injuries. Each activity has been broken into its constituent tasks, and each task has been analyzed for each of seven generic risk factors for overexertion injuries: (1) repetitive exertions; (2) static exertions; (3) forceful exertions; (4) localized mechanical stresses; (5) posture stresses; (6) low temperature; and (7) vibration. Ratings for each risk factor have been made on a three point scale: insignificant, moderate, and high. This analysis shows that virtually all construction activities have moderate-to-high ratings for at least one risk factor, and thereby place craft workers at increased risk for overexertion injuries and disorders.

A computerized model to optimize location of a group of tower cranes is presented. Location criteria are balanced workload, minimum likelihood of conflicts with each other, and high efficiency of operations. Three submodels are also presented. First, the initial location model classifies tasks into groups and identifies feasible location for each crane according to geometric “closeness.” Second, the former task groups are adjusted to yield smooth workloads and minimal conflicts. Finally, a single-tower-crane optimization model is applied crane by crane to search for optimal location in terms of minimal hook transportation time. Experimental results and the steps necessary for implementation of the model are discussed.

Microtunneling is a type of trenchless technology for underground pipeline construction. Using the technology, surface disruptions can be minimized. Currently, open-cut trenching is often not allowed in urban areas or environmentally sensitive areas; therefore, demand for microtunneling is increasing. However, the decision to use microtunneling can be hard to make, because many decision makers are still not familiar with the technology. In fact, it can be a risky and costly process, when used improperly. In order to achieve a successful microtunneling project, it is important to select an appropriate method, considering its strengths and limitations. A decision procedure and tool that outputs appropriate underground pipeline installation methods for specific site conditions is presented here. It should be useful for decision makers who are relatively new to microtunneling, and can be used as a check by more experienced planners.