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PurposeThe paper aims to identify the effective constructability methods and tools that should be applied during the early project design stages to prevent specific constructability failures regarding project context.Design/methodology/approachSeventeen basic constructability problems were defined, 12 constructability implementation methods for investigation were selected, and a general tool representing potential causal connections between the problems and the methods that could prevent them was developed. A comparative case study was conducted through a rigorous investigation of the construction documentation of four major building construction projects. Nearly four hundred constructability problems were identified. The tool developed was used to draw conclusions about the preferred constructability methods, in general, and with respect to specific project contexts.FindingsThe managerial approach offers the best methods for preventing constructability problems. The major methods that emerged were (1) assigning a constructability champion, (2) facilitating the involvement of the general contractor early in the design process, and (3) augmenting design quality control. At the other end of the scale, methods such as company procedures and owner involvement were found to be the least effective.Originality/valueThe paper offers the ability to relate constructability problems to preventive mechanisms and to identify the appropriate steps to be taken to resolve these problems. The mechanism described here can be used by construction companies that keep failure data within accounting files to check projects in retrospect and draw lessons from them to be implemented in future projects.

Population growth and urbanization lead to increasing water demand, putting significant pressure on natural water sources. The rising amounts of domestic wastewater (WW) in urban areas may be treated to serve as an alternative water source that may alleviate this pressure. This study examines sustainability of utilizing reclaimed domestic wastewater in urban households for toilet flushing and garden irrigation. It models a city characterized by water scarcity, using a coal-based electricity mix. Four approaches were compared: (0) Business-as-usual (BAU) alternative, where the central WW treatment plant effluent is discharged to nature; (1) central WW treatment and urban reuse of the effluent produced; (2) semi-distributed greywater treatment and reuse, at cluster scale; (3) Distributed greywater treatment and reuse, at building scale. Environmental life cycle assessment (LCA), social LCA (S-LCA), and life cycle costing (LCC) were applied to the system model of the above scenarios, with seawater desalination as the source for potable water. System boundaries include water supply, WW collection, and treatment facilities. Analytical hierarchy process (AHP), a multi-criteria decision analysis (MCDA) methodology, was integrated into the life cycle sustainability assessment (LCSA) framework as a means for weighting sustainability criteria through judgment elicitation from a panel of 20 experts. Environmentally and socially, the two distributed alternatives perform better in most impact categories. Socially, semi-distributed (cluster scale) reuse is somewhat advantageous over the fully distributed alternative (building scale), due to the benefits of community engagement. Economically, the cluster-level scenario is the most preferable, while the building-scale scenario is the least preferable. A hierarchical representation of the problem’s criteria was constructed, according to the principals of AHP. Each criterion was weighted and those of extreme low importance were eliminated, while maintaining the integrity of the experts’ judgments. Weighted and aggregated sustainability scores revealed that cluster level reclamation, under modeled conditions, is the most sustainable option and the BAU scenario is the least sustainable. The other two alternatives, centralized and fully distributed reclamation, obtained similar intermediate scores. Distributed urban water reuse was found to be more sustainable than current practice. Different alternative solutions are advantageous in different ways, but overall, the reclamation and reuse of greywater at the cluster level seems to be the best option among the three reuse options examined in this assessment. AHP proved an effective method for aggregating the multiple sustainability criteria. The hierarchical view maintains transparency of all local weights while leading to the final weight vector.

The use of near-miss management systems in construction is relatively new and has not been fully explored or understood. Near misses have not been investigated in a systematic perspective that will...

The social benefits and impacts of four alternative approaches to urban domestic non-potable water reuse were compared: (1) central wastewater treatment, no urban reuse. Reclaimed water is discharged to nature; (2) central wastewater treatment and urban reuse of the wastewater treatment plant’s tertiary effluent; (3) semi-distributed greywater treatment and reuse, at cluster scale (8 residential buildings); (4) distributed greywater treatment and reuse, within each apartment building. The impacts of the four aforementioned approaches to water reuse on three relevant stakeholders were investigated: public, community, and consumer. A hierarchical structure of impact categories and sub-categories under these stakeholder groups was established. Expert judgment elicitation was used to attribute weights to the social criteria, through an analytical hierarchy process (AHP). AHP is an established multi-criteria decision analysis method, based on series of pairwise comparisons. It was also used to evaluate impact intensities for both quantitative and qualitative social indicators. All expert judgements were integrated into an overall weight vector, and a comprehensive social score was calculated for each compared scenario. Public commitment to water saving was ranked as the most important factor in assessing the social impacts of urban domestic reuse, with a weight of 29.6%. Two sub-categories of the community category ranked second: urban landscape and community engagement (12.6% and 12.0%, respectively). The two distributed alternatives are advantageous over the other two approaches in terms of water saving and urban landscape. The semi-distributed alternative has a significant benefit of community engagement, which the other three lack. The business-as-usual (BAU, no reuse) scenario scored highest in the categories: public equality, consumer health concerns, and consumption habits. Final scores for the compared scenarios indicate that central reuse is somewhat more socially beneficial than no urban reuse, but the two distributed alternatives are far better. In social life cycle assessment (SLCA) often quantitative and qualitative criteria/indicators exist side by side and their harmonious integration is challenging. The challenge arising is twofold: quantifying qualitative indicators and homogenizing all indicator evaluations into a uniform comparable scale. Both tasks were achieved in this study using the AHP. The AHP also successfully served as a platform for participatory processes of eliciting expert judgments regarding criteria weights and may be very useful for stakeholder participation in any social assessment. Regarding the case study—distributed urban water reuse was found to be socially beneficial, both in terms of promoting public commitment to conservation of natural water resources and in advancing community engagement.

The evaluation of real estate assets is currently one of the main focal points addressed by territorial marketing strategies, with the view of developing high-performing or competitive cities. Given the complexity of the driving forces that determine the behavior of actors in a real estate market, it is necessary to identify a priori the factors that determine the competitive capacity of a city, to attract investments. The decision support system allows taking into account the key factors that determine the &ldquo, attractiveness&rdquo, of real estate investments in competitive urban contexts. This study proposes an integrated complex evaluation model that is able to map out and encapsulate the multidimensional spectrum of factors that shape the attractiveness of alternative real estate options. The conceptual&ndash, methodological approach is illustrated by an application of the model to a real-world case study of investment choice in the residential sector of Naples.

Learning lessons from near-miss reports is a well-known procedure in various high-hazard industries. The construction industry tends to adopt near-miss management systems, but the procedure is relatively new and has not yet been fully explored or understood. Although the management of near-miss reporting systems in construction has been investigated, no effort appears to have been made to suggest a methodology for technically investigating the content of near-miss reported events. This paper reports a study that implemented both qualitative and quantitative analysis methods for a structured investigation of tower-crane-related incident stories (near misses and accidents). The study began by collecting a large number of incident stories (51 accidents and 161 near misses) that were qualitatively analyzed to form an incident database that served as raw material for further quantitative analyses. The database structure definitions contained categories, which in turn contained variables, such as defining the event severity outcomes on a six-point scale from ‘1’ – near miss to ‘6’ – fatality. Further quantitative analysis suggests comparing groups of similar or identical incidents. The groups (clusters) were established by implementing k-means clustering based on the database definitions as variables. The relative risk potential of each cluster was then quantified by comparing each cluster’s severity outcome occurrences to those of the other clusters and to the entire database as well. Findings from the analyses suggest that technical failures are the most hazardous risk factors within the tower crane domain.

The use of data collected from near-miss reports has added value to safety in high-hazard industries such as aviation and the process industry, but this procedure has not yet taken root in construction management practice. Although the management of near-miss reporting systems and the collection of near-miss event reports have been the focus of recent research efforts, the structural analyses of reports have not yet been investigated. This paper reports on a multi-phase research that studied near misses related to crane work and their safety risk potential. Former research stages concentrated on collecting near-miss as well as accident stories and established a structured database of tower-crane related events. The reported events were further classified into five homogeneous clusters and their potential for escalating into accidents at a given outcome severity level was assessed. The research stage reported in this paper builds on the results of the previous stage results, and implements the analytic hierarchy process (AHP) to evaluate the quantitative outcome severity level values, thus computing each event’s total risk potential. The research outcomes reveal inter-relations between technical factors and human factors in the tower-crane domain. Further application is demonstrated, using the risk potential values for construction company safety assessments.

Purpose – This study aims to show how laser scanning data can be utilised to quantitatively assess “blind lifts” with respect to their rate and spatial distribution. Design/methodology/approach – This study employed time study of crane cycles for quantitative measuring of the crane’s work periods in dead areas and mapping the crane operator’s field of view and developing a model that allows the spatial analysis of blind lifts. Findings – This study found a discrete geometric laser scan-based model that is capable of locating and quantifying the visible and invisible zones from the crane operator’s cabin; 28 per cent of the analyzed crane’s work area represented by the model were found to be invisible, which corresponds fairly to 35 per cent of the half-cycles measured manually that were found to involve blind lifting; the range of blind lifts duration derived from the spatial information-based model was 50 to 84 per cent, which is in excellent correspondence with the 54 per cent to 82 per cent range obtained from the time unit-based analysis. Research limitations/implications – The laser-based model and the ensuing analyses are limited to the type of buildings whose envelope can practically be represented by the vertical extrusion of their footprint. Practical implications – The practical implications of the study are reduction of blind lifts as a factor when selecting the location of the crane and staging areas; more effective preplanning of signallers positioning; and ad hoc consideration of analysed dead space for various lift task-based decision-making during construction. Originality/value – This study demonstrates the ability to capture the geometric relations that characterise the work scene around the tower crane by harnessing the increasingly available laser technology and correlates the results of the manual observations with those obtained from the laser-based model.

Airborne dust can be hazardous to workers' health, especially when polymorphic crystalline forms of silica are present, which, depending on their concentration, specificity, and exposure time, can cause respiratory illnesses. In the majority of cases, the presence of some types of dust on building construction sites can be verified visually or through their effects, such as allergic reactions in workers and residents who live nearby. Construction workers are exposed to many raw materials and production processes that produce diverse types of dust, which propagate through the work envi- ronment and the neighborhood surrounding the construction site. The objective of this study was to quantitatively assess the exposure to dust of construction workers in Brazil, a country considered to be representative of the developing world and emerging economies. A preliminary study, conducted at several building sites to identify hazards, consisted of a sur- vey of dust-generating construction materials, processes, and equipment. Nine activities that expose workers to dust were identified, of which six were chosen for further analytical study: mortar/concrete mixing, worksite cleaning, tile cutting, plastering, woodcutting, and wall/ceiling surface sanding for paintwork. The first three activities were analyzed for the presence of free crystalline silica in the total and respirable fractions; of these, the tile-cutting activity presented the high- est exposure to silica concentration. Of the other three activities, paintwork and woodcutting exhibited total dust expo- sures equaling 368% and 159% of the international recommended limits, respectively. This study presents relevant infor- mation to help fight dust exposure on building construction sites and support the need to conduct quantitative dust analy- ses for workers in this sector in order to determine effective protection measurements.

Interior and finishing activities in building construction exhibit high degrees of variation as a result of uncertainty in supply chains, variations in work quantities, client changes, and lack of predictability of the production capacity of subcontracting trades. Decisions must constantly be made concerning effective utilization of available resources. Reentrant workflow patterns, where a trade crew returns multiple times to the same space, make production control particularly difficult. We present a method for pull flow control at the operational level through real-time prioritization of pending work packages and daily regulation of crew assignments and trades’ production capacities. Application of various heuristics was evaluated using discrete-event simulation of a representative construction project. The experimental results emphasize the importance of dynamic control of allocation of production resources to those mature activities that ensure subsequent (downstream) flow. The most successful...

Environmental management and planning are instrumental in resolving conflicts arising between societal needs for economic development on the one hand and for open green landscapes on the other hand. Allocating green corridors between fragmented core green areas may provide a partial solution to these conflicts. Decisions regarding green corridor development require the assessment of alternative allocations based on multiple criteria evaluations. Analytical Hierarchy Process provides a methodology for both a structured and consistent extraction of such evaluations and for the search for consensus among experts regarding weights assigned to the different criteria. Implementing this methodology using 15 Israeli experts-landscape architects, regional planners, and geographers-revealed inherent differences in expert opinions in this field beyond professional divisions. The use of Agglomerative Hierarchical Clustering allowed to identify clusters representing common decisions regarding criterion weights. Aggregating the evaluations of these clusters revealed an important dichotomy between a pragmatist approach that emphasizes the weight of statutory criteria and an ecological approach that emphasizes the role of the natural conditions in allocating green landscape corridors.

Contractors have responded to the growing pressure from owners to shorten project duration by employing a variety of crew-scheduling techniques. Unfortunately, only a limited knowledge base exists for determining the impact of different crew schedules on project performance in terms of cost, duration, productivity, and safety. Standard crew schedules include those that require crews to work 40 h per week, including five 8-h days, four 10-h days, or a second shift. Overtime schedules are also common, which require crews to work additional hours beyond the standard 40 h per week. These overtime schedules include five 9-h days, six 8-h days, or five 10-h days. In addition to the standard and overtime schedules, several other crew-scheduling techniques have been used successfully by contractors. This paper presents the results of a study on the impact of crew-scheduling techniques on overall project performance. The paper identifies the proper application and conditions for successful use of various c...

In the course of a study of mega building construction projects in Germany, the need arose to identify and analyze the characteristics of the local construction culture, particularly upon realization that these characteristics may constitute significant contextual factors in equipment and site logistics planning. The study of the German building construction culture was based on (1) a focused literature review; (2) case studies of multicrane construction sites; and (3) structured interviews with experts of various professions from the German construction industry. The findings highlight the role of the following factors: (1) the typical German professional character; (2) various systems of contractual relationships; (3) state and city regulations; (4) technology and industrialization; (5) workforce sources; (6) rooted safety culture; (7) protection of the environment; (8) the crane market; (9) relationships between planning, engineering, and construction; (10) logistics concepts; and (11) additional unique features of Berlin as a major construction hub. Some of the German culture characteristics detected were further supported by a comparison with other advanced European construction cultures.

The gradual disappearance of traditional borderlines between equipment cultures and the increasing use of tower cranes as today’s dominant building construction equipment result in exposure to safety issues concerning tower crane operation that have not yet been fully addressed. This paper proposes a model capable of computing an overall index that realistically reflects the safety level on any individual site due to the operation of tower cranes. The model integrates four modules: (1) nonsite-specific relative weights of safety factors, (2) measurement of the magnitude of each safety factor actually present on site, (3) scales to convert each measured magnitude into a value representing the potential risk generated by each factor present on site, and (4) multiplying factors to convert the cumulative risk generated by all factors into actual risk. The model was computerized and tested on two construction sites and the user interface for company and site data gathering was validated. The developmen...

The objective of the research reported in this paper was to investigate the use of short arc-length segments and semi-circular segments of paperboard (also known as cardboard) tubes as formwork in bridge deck applications for either long-span [20–50 m (60–160 ft)] steel or prestressed concrete bridges or short-span [6–20 m (20–60 ft)] “Beam-in-Slab” bridges. In both these types of structures conventional plywood and light framing lumber formwork can be expensive and time consuming to install. For over 30 years, paperboard tubes have been used throughout the world to form round, reinforced concrete columns or occasionally voided slabs. These tubes (also know as Sonotubes) are produced throughout the world, and are preferred to conventional steel, plywood, or even fiber reinforced plastic (FRP) formwork because they are economical, disposable and recyclable. Due to their tubular shapes they have not been considered for use in “flat” elements such as slabs and walls. This paper presents results of a series of laboratory tests conducted at the University of Wisconsin – Madison that demonstrate that paperboard tube segments can be used as formwork for certain types of slabs, particularly for bridge decks and a variety of other types of construction where a flat surface is not essential. The testing, which was intended to simulated construction site loading conditions, included ultimate and service load tests, as well as impact loading. Tests were also conducted to investigate how moisture content affects the structural performance of the tubes. Results showed that commercially produced large diameter paperboard tubes may well be viable economical and recyclable materials for forming concrete elements, particularly those used in bridge decks when wide-flange prestressed girders are used.

Modelling the flow of systems and interior finishing works in building construction has been hampered by the inability of traditional critical path modelling to reflect features of these works such as uncertainty, instability, non-linear and interrupted value-adding processes and re-entrant flow. Drawing on empirical data collected in a work study of a large residential project, a novel workflow model is proposed that explicitly models the flows of products and crews at a fine-grained level. The overall model includes a trade workflow model with a module for each work-package type, and a project level model in which multiple trade modules are embedded. The model was tested through implementation of a simulation of a prototypical construction project involving seven work-packages performed in a 20-storey residential tower with 120 customized apartments. The modelled flows of crews through the test building reflected the same behavioural features observed in construction projects. The model enables evaluati...

The wide range of crane types and sizes offered by the market expresses the responsiveness of the lifting industry to meet the variety of challenges posed by the built environment. One such emerging set of challenges is the outcome of the growing rate of wind turbine installation. Wind energy is one of the largest alternative energy production methods today, and as the global push for greener energy sources is increasing, so is the number of windmills. This paper addresses the unique lifting challenges posed by windmill installation and maintenance. These challenges have been met by leading crane manufacturers in various ways to produce products not seen before on the construction scene. The paper focuses on two such products representing two different concepts and provides the development and design rational of each. Engineering is impacted by unique height, lifting capacity, site preparation, and environmental requirements. The accelerated rate of global wind energy use, the increasing number, height, and component weight of turbine towers, and the persistent search for new territories for wind farms are likely to further produce more innovative solutions.

The conception, development, implementation, and commercialization of a crane-mounted vision system through close academia-industry cooperation illustrate how such joint efforts can yield research and development success. The vision system was devised to help solve the problem of blind lifts and other viewing concerns related to the operation of tower cranes on construction sites, thereby enhancing safety and productivity and saving money. In addition to other expected difficulties, the project faced the traditional skepticism of a conservative industry reluctant to adopt changes. The paper relays the chronology of the project and analyzes, stage by stage, the steps taken by the university-based developers to work in harmony with construction companies in particular, and with the industry at large, to ensure success. Lessons drawn from this experience are offered to future academician developers in the field of construction technology.

This paper addresses quantitative measurement and risk scales of safety hazards on construction sites due to the work of tower cranes. Hazard measurement and risk scales are essential components of an integrated model aimed at quantitatively determining the safety level of individual construction sites, on a comparative basis. The paper focuses on two factors identified in earlier studies as considerably affecting safety on sites with tower cranes, "overlapping cranes" and "operator proficiency." These two factors are inherently different from each other in their characteristics and therefore also in the methods used to measure both the factors and the risk resulting from them. A probability-based method was prescribed for the measurement of overlapping cranes, while the analytical hierarchy process method and knowledge elicitation from experts were applied to develop metrics for operator proficiency. In both cases, an intimate understanding of the crane work environment is necessary. The uniform format and specific methodologies presented here can be used in the development of measurement techniques and risk scales for other safety factors concerning crane operation on construction sites.

This paper discusses the development of a model design and construction specification for thin [less than 38 mm (1.5 in.)] non-participating permanent formwork panels (also known as, stay-in-place forms and lost forms) made of FRP or FRC materials with or without non-metallic reinforcements for use in the construction of concrete slabs, in particular, highway bridge decks. The use of such forms is motivated by the narrow gaps [less than 1 m (39.4 in.)] that are often found between the flanges of wide flange ‘‘bulb-T” prestressed girders that are becoming commonplace in the US highway construction industry. Bridge contractors have expressed an interest in using non-participating permanent forms to reduce the time and cost required in forming and stripping the plywood forms for such narrow gaps. A model specification that was developed to enable engineers to design and specify such forms is provided in the appendix to this paper. To develop the specification, different permanent formwork panels were fabricated and tested. These included (1) flat cementitious panels reinforced with short glass or polypropylene fibers, (2) flat cementitious panels reinforced with bi-directional FRP thin grids, (3) flat cementitious panels reinforced with unidirectional FRP reinforcing bars, and (4) off-the-shelf, commercially manufactured pultruded FRP thin-walled, ribbed planks. The specification provides guidance for the width of gaps permissible for each Class of system and details of prescriptive and performance tests that must be performed to qualify the products for use in construction.

Aspiring to adopt a nonstatistical quantitative approach to safety assessment, this study implements a multiattribute decision-making tool to elicit knowledge from experts and formalize it into a set of weighted safety factors. The environment addressed is the construction site and the specific factors studied are those affecting safety due to the operation of tower cranes. Nineteen senior construction equipment and safety experts were interviewed and led through the analytic hierarchy process (AHP) to provide their assessments on the relative importance of safety factors obtained in an earlier study. The results accentuate the dominance of the crane operator and general superintendent on the site safety scene and play down the contribution of “classic” site hazards such as power lines. Quantitative measuring of safety, such as reflected in the weights obtained in this study, is important in communicating safety requirements and focusing the limited resources available for safety improvements. These facto...

Tower cranes are the centerpiece of production on today’s typical building construction sites. Tower cranes hoist and transport a variety of loads near and above people, working under crowded conditions, occasionally with overlapping work zones, and often under time, budget, and labor constraints. This work regime further increases the safety risk on sites that are inherently hazardous workplaces. This paper presents the results of a study that identified the major factors affecting safety in tower-crane environments and evaluated the degree to which each factor influences ongoing safety on site. Use of statistical data on accidents was ruled out as a source of information due to the countless number of incidents that go unreported, the common inability of statistics to provide root causes, and the questionability of statistics as a predictor of accidents. The research methodology was therefore based on comprehensive questioning of an expert team that included the safety managers and equipment managers of...

Operators of tower cranes enjoy a bird's eye view of the site, which undeniably contributes to work safety and efficiency. Yet their work often involves blind lifts, as well as other viewing difficulties, that impede full utilization of the potential inherent in the operator's location atop the crane. This paper reports on a tower-crane-mounted live video system that offers a solution for such difficulties, and consequently, enhances safety, improves productivity, and brings about direct and indirect cost savings. The development and implementation of the vision system are described as a successful academia-industry research and development joint effort. Work studies of numerous craning cycles resulted in considerable time savings, depending on the nature of the lift, lighting conditions, and viewing obstructions. In addition, a detailed list of benefits drawn on the basis of feedback received from the field is presented. The paper is aimed, first and foremost, at project managers as well as construction equipment and safety practitioners, who daily experience those situations that have prompted the development of the system. Researchers may benefit mainly from the lessons learned with respect to the role of academia-industry cooperation in the introduction of innovative systems in construction.

A great many of today's construction projects are characterized by high levels of dynamics, namely, the combined effect of complexity, uncertainty, and speed. Managing projects under such conditions is difficult and challenging, and the question is asked: How do managers do it? Aspiring to answer this question, ten excellent on-site construction project managers were systematically observed during one workweek each, within an extensive study that examined their performance in their dynamic management environments. The structured observation and documentation and the analysis that followed them enabled us to characterize the managers' work and exposed their unique modes of operation through which they consistently excel in their work. Among many aspects addressed by the said study, this paper focuses on communication and, using various measures, examines the intensiveness and extensiveness of communication performed by the PMs in the broad context of their work. The study found that the on-site construction PMs were strongly oriented toward verbal communication of information (during nearly 80% of their activities and time); they spent a major portion of their workdays in meetings (during 60% of their activities, and of which nearly 80% were unplanned); and they showed clear preference for interacting informally with no more than one or two other persons (during 93% of their activities and 88% of the time). The unique knowledge base resulting from this study constitutes a potential contribution for practitioners who are required to function in similar dynamic work environments, as well as for students, teachers, and researchers of construction management.

This paper raises the issue of "soft" considerations in the selection of equipment for building construction projects. The paper aims at increasing the awareness: 1 to the nature, variety, and richness of soft factors; 2 to their significant role and potential impact on the outcome of decision making; and 3 to the inherent difficulty of evaluating them and integrating them within a comprehensive selection process. Existing state-of-the-art equipment selection models were analyzed and found to be inadequate in terms of both considering soft factors and providing mechanisms for their systematic evaluation. Six cases of large-size, complex construction projects were investigated to obtain an extensive list of typical soft factors. This investigation revealed that the consideration of soft factors in current practices is essentially unstructured and is not integrated within the selection process in a systematic manner. A desirable selection process is outlined that generally responds to the needs identified in the study. The proposition of a specific method for the quantitative treatment of soft factors and their tradeoff with cost factors is the subject of another paper.

Cranes have come to symbolize building construction itself. They perform indispensable services in moving materials and components vertically and horizontally. Used since antiquity, their history is interrelated with the development of new power sources that replaced man and mule, first steam and later internal combustion, diesel, and electric engines. Mobile cranes can be rapidly deployed to lift heavy loads. New models with telescoping booms and all-terrain travel capability, compact urban machines, and even hybrids with tower cranes are beginning to replace the familiar lattice boom truck cranes. Mobile cranes have dominated the North American market, but a cultural change appears to be taking place toward tower cranes for building projects. Tower cranes, common in Europe for decades, are globally gaining in popularity with surging real estate developments. Ideal for dense urban environments and coming with a small footprint, they are available in a growing diversity of sizes and configurations. Sophis...

Selecting the right equipment for the project is inherently a multifaceted cost and benefit evaluation process that is further compounded by the complexity of today's building projects and the lack of systematic tools for the consideration of soft factors. This paper presents a detailed application example of a model based on an analytical hierarchy process (AHP) approach. This model was developed to address the difficulties experienced during the multifaceted process. The example illustrates how an AHP-based model helps address the multitude of qualitative, intangible factors, both among the factors themselves and then vis-a-vis costs, by means of a systematic and traceable process. The method enables project managers and their equipment selection teams to exercise their knowledge, intuition, and professional judgment, and at the same time to address the context and specifics of the particular projects under examination. The example should be helpful for construction practitioners dealing with similar equipment selection issues. Researchers may find interest in the implementation of a multiattribute-decision-making method for a typical construction management problem.

Mega building projects typically employ numerous tower cranes covering the entire area of the building footprint and staging areas with multiple overlapping work envelopes. This paper aims to answer the following question: Are the determinants of crane selection for mega building projects similar to projects serviced by a small number of cranes? On-site interviews found: (1) the visibility of the crane forest in the surroundings of the project affects the approach to crane selection; (2) various modes of action are taken by project management to share information with the neighboring residents and business and to ease the hardships of living and working near a busy construction site; and (3) cranes are often selected and located such that they could dismantle other cranes, due to difficulties of using a dismantling mobile crane in the depth of the crane array.

A study conducted in Israel, among ten excellent on-site construction project managers (PMs), examined the ways in which they cope with the dynamic project environment of the modern construction site (complex, uncertain, and fast). Empirical data gathered by means of structured observations led to the development of the Star Model, which offers a multidimensional description of the dynamic patterns of the managers’ activities, namely, their managerial dynamics. In addition, characterization of the level of environment dynamics with which managers were required to cope in their work, led to the identification of a tentative relationship between contextual conditions that characterize the project environment and the level of managerial dynamics practiced by the managers. This tentative relation, which basically suggests that managers should adapt their level of managerial dynamics to the level of dynamics they find on-site, apparently holds one of the keys to the managers’ excellent job performance.

The project management team directing the construction of a concrete building learned during the last stages of construction that the building encroached by 190 cm into the permit specified setback. This case study discusses how the Internet was used to aid the contractor in addressing the problem and the particular solution adopted for moving the building. The steps taken by the project management team from the moment the problem was discovered through moving the building to its correct location are described. Practitioners can learn much from the creative approach used by this project team to find a solution to the challenges of such a unique problem.

Selection of equipment for construction projects, a key factor in the success of the project, is a complex process. Current models offered by the literature fail to provide adequate solutions for two major issues: the systematic evaluation of soft factors, and the weighting of soft benefits in comparison with costs. This paper presents a selection model based on analytic hierarchy process (AHP), a multiattribute decision analysis method, with a view to providing solutions for these two issues. The model has the capacity to handle a great number of different criteria in a way that truly reflects the complex reality, to incorporate the context and unique conditions of the project, and to allow for manifestation of user experience and subjective perception. The model was implemented in an in-house developed system that was improved and validated through testing by senior professionals. The main academic contribution of the study is in the modification of AHP to correspond with the nature of equipment selection and in its utilization as an effective means for the formalization of knowledge possessed by competent, experienced practitioners. On the practical side, the proposed model offers an efficient, convenient tool that forces the users into orderly, methodical thinking, guides them in making logical, consistent decisions, and provides a facility for all necessary computations.

The distinctive design and construction requirements of an outdoor athletic stadium in Haifa, Israel, are described in this paper. This open-air stadium accommodates approximately 2,400 seats in its upper deck, while the lower part of the stadium contains offices and visitors' facilities. The stadium has a distinctive arrangement of 30 m high bowed-concrete columns from which 24 m long curved concrete beams are cantilevered. Because of restricted access to the project site, it was necessary to cast the stadium's concrete columns and beams on site and then lift these elements with large cranes.

One of the differences between industrial manufacturing or processing plants and construction sites is the temporary nature of the construction site, which has traditionally precluded installation of sophisticated production monitoring systems. Monitoring of pro- duction progress, cost, and quality is performed almost exclusively manually, with the result that it is expensive and approximate, and is commonly delivered with a time lag that does not allow for an effectively closed control loop. Automated monitoring of construction lifting equipment to provide useful feedback information for project management is a strong potential candidate; almost all components and materials must be transported by machines, and monitoring of machines is relatively straightforward. A system concept, employing a "black box" monitor and an electronic building information model, was developed. A field study was conducted to test the feasibility of the concept. The results indicate that the system is technically feasible, and offers the potential to deliver real-time, accurate project control information at very low cost.

Formwork for cast-in-place concrete in high-clearance construction is commonly based on multitier shoring towers. The market has responded to the demand for shoring towers by offering numerous proprietary models, from which the constructor can choose. Thus, there is a need for comparative data and selection criteria that are comprehensive, objective, uniformly processed, and systemati- cally organized. This paper presents methodology, formatted data, and findings that purport to assist constructors in rationally selecting the appropriate shoring towers for their projects. For the benefit of industry practitioners, the paper offers an overview of tower configuration and classification, a formatted list of selection criteria generated on the basis of input from formwork manufacturers, and interviews with representatives of formwork service companies, examples of comparative data on selected tower models, and quantitative comparisons based on the introduction of normalized parameters and on formwork solutions for typical cases. This information is particularly vital given the high cost of tower-based formwork relative to the overall construction cost of the supported concrete element, while published erection and dismantling work input data are largely still unavailable for most models and heights of shoring towers.

Shoring towers are the common formwork solution for high-clearance construction. Because towers account for a remarkably high percentage of the cost of the constructed concrete element, work input data and related economic aspects of tower erection constitute important information for constructors. This paper presents three case studies of high multitier shoring towers, each representing a different tower type. Tower data, major construction parameters, and work inputs for each case are presented. Findings are compared and discussed, and due conclusions are drawn. Finally, recommendations on measures expected to increase the economy of shoring solutions using multitier towers are offered, and some restrictions on the adoption of work input data are listed.

Tower cranes commonly constitute the bottleneck of production on today’s typical building construction projects, so shortening of crane cycle durations is often the key to increased site productivity. This case study examined one potential determinant of cycle duration that has been largely overlooked in the wide body of cycle time research, which is the operation mode (OM) of top-slewing tower cranes: from the cab or by remote control. This knowledge gap was addressed by providing quantitative substantiation to qualitative evaluations regarding the advantages and disadvantages of both OMs. The results revealed that there prevail certain conditions under which the two OMs may yield identical cycle times or even give remote operation an advantage. The study also identified that it is the balance between the fast-travel part of the cycle and the fine-maneuvering part that determines which of the two OMs will generate shorter cycle times. These findings will be useful for construction professionals w...

Shoring towers are the common formwork solution for high-clearance construction, but there are not many documented cases of extremely high towers. This paper reports on a project in which 60-m-(200-ft-) high shoring towers were used for slab formwork. The paper describes the design and construction of the formwork, with a focus on aspects unique to high multitier towers. The various considerations made are presented, and data and information are provided that may assist practitioners facing similar engineering undertakings. Special attention is given to the organization of the work, in light of the scarcity of data pertaining to shoring towers of such heights. Measured assembly and disassembly work inputs are presented and analyzed, and the validity of a model to predict work inputs in multitier tower erection is examined.

High shoring towers, the common shoring solution for high clearance construction, cause the entire formwork system to account for a remarkably high percentage of the cost of the constructed concrete element. However, data on work inputs in assembly and disassembly of high towers are scarce, and the reason lies in the difficulty in conducting the numerous work studies that would be needed to cover the wide variety of tower types offered by the market and the extensive range of heights to which towers are erected. A model is presented, based on a limited number of work studies, for the prediction of work inputs in the assembly and disassembly of shoring towers of two configurations, rising to heights of up to 30 m. Results of actual measured work input data for three tower models representing three tower types widely used on construction sites are presented. An insight is provided into the anatomy of tower erection, which should make possible use of the proposed methodology for the development of similar mo...

This paper presents an approach to the integration of site-related activities into the planning and scheduling of the entire construction project. The paper starts by briefly reviewing some common methods used by construction firms in the planning and scheduling of site activities. Next follows a discussion of current research efforts concerned with the modelling of site-related procedures. Then a virtual-reality-based model is proposed, which uses both knowledge-based simulation of the work progress and visualisation capabilities, to achieve the desired integration. Finally the prototype system is described and its potential is demonstrated through several examples.

The complicated process of selecting cranes for construction projects can be divided roughly into two main phases: (1) a general decision on the type of crane, mobile or tower; and (2) selection of the particular model according to the required size and technical specification. Several determinants of this second phase of the selection process in a typical mobile crane culture were investigated through on-site interviews with representatives of major construction companies. Factors affecting mobile crane selection were identified, classified, and rated according to their degree of influence. The involvement in equipment planning and crane selection was characterized with regard to project stages and planning parties. The findings were analysed with a view to the changing participation level of each party throughout project life. The conclusions of the study portray a picture that is different from the common assumptions about mobile crane selection, with respect to both influencing factors and the process...

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.

Tower cranes enjoy a long useful working life. Therefore, a vast population of cranes are still in use today that do not feature the advanced automation and sensor technologies such as those with which some of the new models are equipped. This paper examines the technological and economic feasibility of retrofitting existing tower cranes with semi-automatic devices for motion control. The proposed improvements are intended to enhance the cranes' efficiency and their capacity to meet the challenges of today's tightly scheduled construction projects. Based on work studies and analyses of craning cycles, the concept offered by the proposed improvements distinguishes between the long-distance navigation of the crane's hook and the fine maneuvering in the loading and unloading zones. The expected economic benefits resulting from the enhancement of the crane's performance, with regard to both types of motion, far exceed the cost of installing the various devices.

The need to provide immediate housing solutions for hundreds of thousands of people in the early 1990's faced the Israeli construction industry with an unprecedented challenge: to multiply overnight its output and drastically cut construction time. It also created a unique opportunity to observe a national‐level experiment of great magnitude aimed at meeting that challenge. The present paper reports on a study that examined how construction companies managed to cut housing construction time to half of what had been accepted earlier as a normal pace. This was achieved by implementing an approach that concurrently and integratively treats environment, technology and management determinants, creating a synergetic effect. The present paper introduces and demonstrates the integrative approach to schedule compression, and highlights the role of the environment.

This paper presents a quantitative economic analysis and a qualitative constructability analysis of three-dimensional fiber-reinforced plastic (FRP) reinforcement cages for concrete beams. Material, labor, and life-cycle costs are provided, and construction practice aspects are discussed. The results of the analyses indicate that prefabricated FRP cages can offer benefits to the construction industry. Although the initial costs of the FRP materials are likely to be higher than those of steel rebar, there is a significant potential for cost savings due to reduced maintenance and labor costs, as a result of the corrosion resistance of the FRP and the increased construction productivity. When direct life-cycle costs are considered, FRP reinforcements already constitute, in many cases, an economically competitive alternative to conventional steel reinforcement in adverse environments. If, in addition, the indirect cost savings as well as quality and safety issues are considered, the FRP reinforcement may be even more competitive.

While tower cranes traditionally are identified with high-rise, congested urban building construction, and mobile cranes primarily are associated with heavy civil and infrastructure construction, there exists a vast population of building projects where both are feasible. The question, then, is: why are different crane types used under similar project conditions in different geographic areas (e.g., tower cranes in Europe, mobile cranes in the United States)? This paper examines the culture of using mobile cranes for building construction, as observed in the southwestern United States. Project-specific and environmental characteristics are identified, classified, and described, while comparatively relating to tower crane practice. The role of non–project-specific factors (such as planning culture, operating style, employment patterns, and market organization) is emphasized in shaping the mobile crane culture. A rather homogeneous population of projects with distinct features, such as short construction dur...

Although formwork based on high shoring towers is a very common solution for forming elevated slabs and other concrete elements over high spaces, the trade literature furnishes neither detailed guidelines nor basic cost data for the design of such formwork. The present paper presents a method for the design of elevated-slab formwork using scaffold-type towers as the vertical shoring element. The method includes the definition of a basic tower layout and its properties, an algorithm for determining the distances between the various elements of the formwork, and key information as a basis for economic evaluation of alternate design solutions. Whereas the algorithm directly solves a general case of a flat, nonconstrained slab, the method as a whole readily applies to elevated slabs and other high-rise concrete elements of any kind. The method has been found particularly useful when computerized. It may become even more important when incorporated into an intelligent design system that will take into account shape and load constraints exerted by particular cases.

Formwork commonly constitutes about 40–60% of the overall costs of constructing concrete elements. With high elevated concrete elements, the vertical shoring for the high soffits may raise the share of formwork cost even higher, making it imperative that the formwork design be more rigorously addressed. This paper presents a method for the design of high elevated slab formwork in which shoring towers are the central element. The method defines the primary stages of the design process, determines the detailed procedure within each stage, and identifies the basic data needed for exercising the design. The proposed method is aimed at producing design solutions that meet both quality and economy criteria. The paper also identifies open issues in formwork design and practice, and consequently suggests areas for further research.