The use of prefabrication offers significant advantages, yet appropriate criteria for applicability assessments to a given building have been found to be deficient. Decisions to use prefabrication ...are still largely based on anecdotal evidence or simply cost-based evaluation when comparing various construction methods. Holistic criteria are needed to assist with the selection of an appropriate construction method in concrete buildings during early project stages. Following a thorough literature review and comprehensive comparisons between prefabrication and on-site construction method, a total of 33 sustainable performance criteria (SPC) based on the triple bottom line and the requirements of different project stakeholders were identified. A survey of U.S. experienced practitioners including clients/developers, engineers, contractors, and precast concrete manufacturers was conducted to capture their perceptions on the importance of the criteria. The ranking analysis of survey results shows that social awareness and environmental concerns were considered as increasingly important in construction method selections. Factor analysis reveals that these SPCs can be grouped into seven dimensions, namely, economic factors: “long-term cost,” “constructability,” “quality,” and “first cost”; social factors: “impact on health and community,” “architectural impact”; and environmental factor: “environmental impact.” The resultant list of SPCs provides team members a new way to select a construction method, thereby facilitating the sustainable development of built environment.
With the rapid development of urbanization in China, the number and size of underground space development projects are increasing quickly. At the same time, more and more accidents are causing ...underground construction to increasingly become a focus of social attention. Therefore, this research presents a real-time safety early warning system to prevent accidents and improve safety management in underground construction, based on the “internet of things” (IoT) technology. The proposed system seamlessly integrates a fiber Bragg grating (FBG) sensor system and a RFID (radio frequency identification)-based labor tracking system. This system has been validated and verified through a real-world application at the cross passage construction site in the Yangtze Riverbed Metro Tunnel project in Wuhan, China. The system's application results show that it can effectively promote underground construction safety management efficiency, specifically in the real time detection, monitoring and early warning of safety risks.
•An early warning system based on IoT for underground construction was proposed.•FBG sensor and RFID technology were integrated seamlessly in the proposed system.•The system has been applied in the Yangtze Riverbed Metro Tunnel project in China.•The results reflect the freezing process and labor position in cross construction.
Construction Safety Risk Mitigation Hallowell, Matthew R; Gambatese, John A
Journal of construction engineering and management,
12/2009, Volume:
135, Issue:
12
Journal Article
Peer reviewed
Construction safety and health management has improved significantly following the Occupational Safety and Health Act of 1970. In response to this legislation, contractors began implementing safety ...programs to reduce occupational safety and health hazards on construction sites. Researchers recently found that the current process of selecting specific elements for a safety program is informal. This paper describes the results of a recent study designed to determine the relative effectiveness of safety program elements by quantifying their individual ability to mitigate construction safety and health risks. In order to determine the effectiveness of individual safety program elements, the following research activities were performed: (1) an appropriate safety risk classification system was created using an aggregation of relevant literature; (2) highly effective safety program elements were identified in literature; and (3) the ability of each safety program element to mitigate a portion of each of the safety risk classes was quantified using the Delphi method. The results of the research indicate that the most effective safety program elements are upper management support and commitment and strategic subcontractor selection and management and the least effective elements are recordkeeping and accident analyses and emergency response planning. It is expected that the data presented in this paper can be used to strategically select elements for a safety program, target specific safety and health risks, and influence resource allocation when funds are limited.
•Analysis of multi-storey residential building located in hot and humid climate.•Modelling of energy use for on-site construction processes.•Significance of construction energy for buildings with ...partial or no air-conditioning.•Analysis of building operational energy using field data.•Study of embodied energy of construction materials and building components.
The life cycle energy of a building consists of construction energy, operational energy and demolition energy. Construction refers to initial construction as well as recurring maintenance and repair work. Initial construction represents manufacturing of construction materials, transportation and site related on-site construction processes. Only a few studies focused on life cycle energy use of Indian residential buildings. However, the energy use due to on-site construction processes is either ignored or not modelled with adequate level of detail at present. This paper presents a case study on life cycle energy analysis of a residential development consisting of 96 identical apartment-type homes located in Southern India. Energy use due to transportation of materials and construction equipment use at site are quantified. Sensitivity analysis is carried out to study the influence of building service life and monthly electricity use per home on the relative significance of construction energy and operational energy. The construction energy is found to be a significant component of life cycle energy of residential buildings with partial or no air-conditioning. Further, reduced building service life period and increased energy efficiency achieved in the operational phase makes the construction energy as important as the operational energy with respect to life cycle.
Construction sites still present high accident rates. The advent of advanced sensing technologies has motivated the development of unprecedented automated systems, capable of supporting health and ...safety control. Their application is particularly critical in those cases where regular safety inspections may prove to be inadequate in terms of preventing risks which, because of their specific nature, are unpredictable.
This paper reports the development of a first prototype for the proactive safety management and real-time signaling of potential overhead hazards. It is expected to enhance standard safety policies and assist inspectors and coordinators in executing their tasks. The system performs real-time tracking using ultra wide band technology and implements proactive virtual fencing logics. The development of the system, its laboratory test results, the algorithm optimization, and the final field test results are reported herein. The results achieved demonstrate the capability of proactive logics to reinforce safety management policies and assist personnel in coping with unpredictable hazardous events.
Abstract
In the construction industry, increased efforts are being made to automate production processes using industrial robots in order to increase efficiency, improve quality and optimize the use ...of materials. Tunnel construction is particularly suitable for the use of modern production methods, as the increased use of machines and the high repetition factor of the components used make it possible to scale production technology across project boundaries. This paper provides examples of current developments in segment production, in particular the use of industrial robots in the prefabrication of reinforcement cages and subsequent concreting. Necessary adaptations in segment design are pointed out when welded reinforcement is used, and conceivable further developments are shown. The medium‐term goal is a continuous IT‐based production control system that allows short‐term adjustments to segment production, logistics and subsequent installation in the tunnel.
Abstract
In der Bauindustrie werden verstärkte Anstrengungen unternommen Produktionsprozesse durch den Einsatz von Industrierobotern zu automatisieren, um die Effizienz zu steigern, die Qualität zu verbessern sowie den Materialeinsatz zu optimieren. Besonders geeignet für den Einsatz moderner Fertigungsmethoden ist der Tunnelbau, da insbesondere durch den verstärkten Maschineneinsatz und hohen Wiederholungsfaktor der eingesetzten Bauteile eine Skalierung der Produktionstechnik über Projektgrenzen hinweg möglich ist. Der vorliegende Aufsatz erläutert exemplarisch die aktuellen Entwicklungen im Bereich der Tübbingproduktion, insbesondere den Einsatz von Industrierobotern in der Vorfertigung der Bewehrungskörbe bzw. der anschließenden Betonage. Auf notwendige Anpassungen im Tübbingdesign wird bei Einsatz von geschweißter Bewehrung hingewiesen sowie denkbare Weiterentwicklungen aufgezeigt. Mittelfristiges Ziel ist eine durchgehende IT‐basierte Produktionssteuerung, die kurzfristige Anpassungen in der Produktion, aber auch in der Logistik und dem anschließenden Einbau im Tunnel ermöglicht.
AbstractIt is well established that the project cost, quality, safety, and duration are the four critical elements that contribute to project success. Past literature has established theoretical ...relationships between construction safety and quality on the basis of opinions of industry experts. This is the first empirical inquiry into the relationship between safety and quality, testing the null hypothesis that there is no statistical relationship among quality performance indicators and safety performance indicators. To test this hypothesis, empirical data were collected from 32 building construction projects, ranging in scope from $50,000 to $300 million dollars. Several quality metrics (e.g., cost of rework per $1M project scope and rate of rework per 200,000 worker-hours) were used as predictor variables and first aid and Occupational Safety and Health Administration (OSHA) recordable injury rates were used as response variables. Linear regressions among the predictor and response variables showed that there are two statistically significant relationships: the OSHA recordable injury rate is positively correlated to rework (r2=0.968; p-value=0.032) and the first aid rate is positively correlated to number of defects (r2=0.548; p-value=0.009). To understand why these relationships exist and to identify specific strategies that promote both safety and quality, open-ended interviews were conducted with project managers. These individuals indicated that the most compelling reason for the strong positive correlation between rework and injuries is the fact that rework involves demolition, schedule pressure, and unstable work processes. They also noted that devoting resources to preplanning, allowing the necessary time to complete tasks correctly the first time, encouraging leadership at the workface, and encouraging workers to take pride in their work are all strategies that promote both safety and quality.
We assess the durability of an Ultra High Performance Fiber Reinforced Concrete (UHPFRC) after accelerated aging, i.e. after partial drying, or 105°C oven-drying (dry reference state), 200, 300 or ...400°C heat-treatment, or progressive splitting (Brazilian test). Our key experimental tool is gas permeability Kgas under varying confinement Pc, coupled to MIP and SEM analysis. UHPFRC properties are compared to standard mortar and ordinary concrete.
Whereas usual UHPFRCs involve pozzolanic additions and thermal curing, this UHPFRC does not, and is significantly more porous (by 9–10%). However, 74% of its porosity comprises pores smaller than 4nm, i.e. located within the C–S–H. Dry reference state UHPFRC lies in the range of very high durable materials, with an average Kgas=10−18m2. Damage by heat-treatment at 400°C induces limited de-bonding at the fiber/paste interface, which increases Kgas up to 10−17m2 at Pc=6MPa. While sustaining more than 300μm/m tensile strain, Kgas of UHPFRC remains virtually identical.
•Gas permeability is used to assess durability of a UHPFRC after accelerated aging.•Dry gas permeability of UHPFRC (10–18 m2) places it in the very high durability range.•400°C heat-treated UHPFRC displays limited de-bonding at the fiber/paste interface.•400°C heat-treated UHPFRC is still placed within very high durability range, Kgas= 10–17 m2.•Brazilian splitting leads to 360μm/m diametral strain, but low Kgas is preserved.
A quantitative assessment of the environmental impact of construction activities can help decision-makers identify major environmental impact factors and make environmentally friendly construction ...plans in the early stages of construction. This paper presents an integrated life cycle environmental impact assessment model that is applicable to construction phase studies, where impact factors are examined according to two aspects of a typical construction process: construction equipment and ancillary materials. Environmental impacts are categorized into three safeguard subjects: ecosystems, natural resources and human health. A disability adjusted life year (DALY) model for assessing human health damage due to construction dust is developed. In addition, the environmental impact of earthwork construction is assessed as a case study to demonstrate the application of the proposed model. Results indicate that the proposed model can effectively quantify the environmental impacts of construction processes, and can potentially be used as a tool for contractors to select environmentally friendly construction plans.
This study investigates the influence of highly purified, nano-sized attapulgite clays on the rate of structural rebuilding of cement pastes. A shear rheological protocol is implemented that measures ...the rate of rebuilding of pastes after being broken down under shear and maintained under stress corresponding to the weight of the material. This simulates a real casting situation during which the concrete is initially in motion, then cast in place and measures how quickly it gains green strength immediately after placement. The rate of recovery for different resting times and preshear conditions are considered. The strain rate decay curves are fitted with a compressed exponential model to obtain relaxation time. The results show that the purified attapulgite clays significantly accelerate rate of recovery of pastes, especially at early ages. However, this accelerating effect diminishes at longer resting times as hydration mechanisms begin to dominate.
•Purified attapulgite clays accelerate rate of thixotropic rebuilding of cements.•Stress relaxation exhibit compressed exponential behavior, indicating jammed system.•Accelerating effect of clays on rebuilding decreases over time as hydration governs.
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