In construction, about 80%–90% of accidents are associated with workers' unsafe acts. Nevertheless, the measurement of workers' behavior has not been actively applied in practice, due to the ...difficulties in observing workers on jobsites. In an effort to provide a robust and automated means for worker observation, this paper proposes a framework of vision-based unsafe action detection for behavior monitoring. The framework consists of (1) the identification of critical unsafe behavior, (2) the collection of relevant motion templates and site videos, (3) the 3D skeleton extraction from the videos, and (4) the detection of unsafe actions using the motion templates and skeleton models. For a proof of concept, experimental studies areundertaken to detect unsafe actions during ladder climbing (i.e., reaching far to a side) in motion datasets extracted from videos. The result indicates that the proposed framework can potentially perform well at detecting predefined unsafe actions in videos.
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•The framework allows for the automatic detection of unsafe actions in site videos.•Computer vision techniques enable estimation of body joint positions on 2D images.•Using stereo cameras, a 2D human skeleton can be reconstructed in a 3D coordinate.•Dimension reduction can improve the accuracy and efficiency of motion analysis.•With motion templates, similar actions can be detected through pattern recognition.
Prefabrication is one strategy considered to provide improved environmental performance for building construction. However, there is an absence of detailed scientific research or case studies dealing ...with the potential environmental benefits of prefabrication, particularly the embodied energy savings resulting from waste reduction and the improved efficiency of material usage. This paper aims to quantify the embodied energy of modular prefabricated steel and timber multi-residential buildings in order to determine whether this form of construction provides improved environmental performance over conventional concrete construction methods. Furthermore this paper assesses the potential benefits of reusability of materials, reducing the space required for landfill and need for additional resource requirements. An eight-storey, 3943 m2 multi-residential building was investigated. It was found that a steel-structured prefabricated system resulted in reduced material consumption of up to 78% by mass compared to conventional concrete construction. However, the prefabricated steel building resulted in a significant increase ( similar to 50%) in embodied energy compared to the concrete building. It was shown that there was significant potential for the reuse of materials in the prefabricated steel building, representing up to an 81% saving in embodied energy and 51% materials saving by mass. This form of construction has the potential to contribute significantly towards improved environmental sustainability in the construction industry.
AbstractConstruction labor productivity has become such a buzz word and one of the most frequently researched topics. In most countries, labor cost comprises 30 to 50% of the overall project’s cost, ...and thus is regarded as a true reflection of the economic success of the operation. There are many challenges facing the construction industry in the state of Kuwait but one of the most important is low productivity. The objective of this research, therefore, is to identify and rank the relative importance of factors perceived to affect labor productivity on construction sites in Kuwait. To achieve this objective, a statistically representative sample of contractors was invited to participate in a structured questionnaire survey, comprising 45 productivity factors, classified under the following four primary groups: (1) management; (2) technological; (3) human/labor; and (4) external. Among the factors explored, the subsequent 10 are discerned to be the most significant in their effects on labor productivity: (1) clarity of technical specifications; (2) the extent of variation/change orders during execution; (3) coordination level among design disciplines; (4) lack of labor supervision; (5) proportion of work subcontracted; (6) design complexity level; (7) lack of incentive scheme; (8) lack of construction manager’s leadership; (9) stringent inspection by the engineer; and (10) delay in responding to requests for information. The results obtained fill a gap in knowledge of factors affecting labor productivity in Kuwait, which can be used by industry practitioners to develop a wider and deeper perspective of the factors influencing the efficiency of operatives and provide guidance to construction managers for efficient utilization of the labor force, hence assist in achieving a reasonable level of competitiveness and cost-effective operation.
In recent years, with the increasing level of competition in the global construction market, several research efforts have focused on the application of information technology (IT) as a way to ...improve the integration process of construction supply chain management (CSCM). Visual representation of the process can provide an effective tool for monitoring resources in the CSCM. In order to support this objective, this paper integrates building information modeling (BIM) and geographic information systems (GIS) into a unique system, which enables keeping track of the supply chain status and provides warning signals to ensure the delivery of materials. First, the proposed methodology is implemented by using BIM due to its capability to accurately provide a detailed takeoff in an early phase of the procurement process. Furthermore, in order to support the wide range of spatial analysis used in the logistics perspective (warehousing and transportation) of the CSCM, GIS is used in the present model. Thus, this paper represents the integrated GIS-BIM model manifesting the flow of materials, availability of resources, and “map” of the respective supply chains visually. A case example is presented to demonstrate the applicability of the developed system.
► Application of IT to improve the integration of construction supply chain (CSC). ► Integrating BIM and GIS into a unique system. ► Visual representation of the CSC process, keeping track of the material status. ► Providing warning signals using BIM-GIS to ensure the delivery of materials.
In this paper, a typical equivalent fitting linear modeling method is studied by using BIM technology. This paper realizes the quality-efficiency control of construction projects based on BIM ...technology. The software can realize the cost data statistics and collection of each sample. The system takes the statistical sequence of each department’s project cost as the original data for dimensionality reduction processing. The variance contribution is used as the weight to calculate the weight of each main component. According to the finite element analysis of combined parameters, the project cost and construction benefit are the restrictive factors. A multi-factor comprehensive evaluation method establishes a rapid construction cost evaluation model. The experimental results show that this method agrees with the conventional calculation method and the measured data. The estimated cost of construction differs little from the measured value. The results show that the model constructed according to different stages of the construction projects has good prediction accuracy.
AbstractA large amount of field and experimental data has been devoted to rectangular excavations thus far. In contrast, very few data were available for cylindrical excavations, especially those ...with large diameters in thick soft clay deposits. Via a comprehensive instrumentation program on a 100-m-wide×25.89-m-deep unpropped (self-supported) cylindrical excavation constructed by the bottom-up method in Shanghai soft clay, the characteristics of this large-sized circular excavation were extensively investigated. This cylindrical shaft was a part of a large-scale deep foundation pit excavated by the central-island technique. The investigated items included (1) lateral wall deflections, (2) vertical wall movements, (3) lateral ground movements, (4) ground settlements, (5) subsurface settlements, (6) basal heaves, (7) vertical column movements, (8) column stresses, and (9) variation of pore pressures along depth and artesian water levels. Analysis of the field data indicates that discharging of the deep artesian water was one of the key factors affecting the excavation behaviors. The influence zone of basal heave caused by soil removal (stress relief) reached very deep soil layers, far beyond the depths reported in literature. Column movement and stress were shown to be reliable indicators of the relative movement between basal soils, diaphragm walls, and interior columns. Finally, the comparisons of this study with other bottom-up excavations in Shanghai, including 11 cylindrical excavations, 92 building basement excavations, and eight metro station excavations, demonstrate that self-supported (unpropped) cylindrical excavations had much stronger capabilities of resisting deformation than both multipropped regular basement excavations (in terms of deformation magnitudes) and long and narrow metro station excavations (in terms of scale of influence zones). For cylindrical shafts, their diameters, and not wall penetration ratios, played a dominant role in the determination of excavation behaviors. However, when the shaft diameter reached 90 m or more, the advantage of cylindrical shafts over rectangular pits in constraining wall deflection was no longer obvious.
Abstract
In response to spalling of concrete parts, the headrace tunnel was to be strengthened section by section and made fit for the years to come. Since little information was available on the ...condition of the tunnel and the cause of the spalling, possible damage patterns and causes were analyzed and grouting in combination with concrete rehabilitation were defined as strengthening measures. During a break in operation of approx. 2 months in June 2020, cement injections were tested in grouting trials in different variants to determine their suitability and optimize the parameters and the work to be carried out. The tests and the investigations carried out revealed interesting findings about the condition of the tunnel. The grouting was carried out at low pressure, at different distances and drilling depths, testing important parameters for the subsequent execution and enabling optimization. The porosity of the lining was significantly reduced by grouting, thus improving the quality of the shell. A before‐and‐after measurement with georadar investigation demonstrated the improvement of the lining due to the grouting.
A remarkable finding is the combination of the relatively poor quality of the lining concrete, which is due to the construction during World War II, with the practically uncracked and relatively tight lining. It is a testimony to a high level of construction skill that it was possible to create such durable structures with the means available at the time.
Abstract
Nach abgeplatzten Betonteilen im Druckstollen sollte dieser abschnittsweise ertüchtigt und für die weiteren Jahre fit gemacht werden. Da wenig Informationen über den Zustand des Stollens und die Ursache der Abplatzung vorlagen, wurden mögliche Schadensbilder und Ursachen analysiert und Injektionen in Kombination mit einer Betonsanierung als Ertüchtigungsmaßnahme definiert. Innerhalb einer Betriebspause von ca. 2 Monaten wurden im Juni 2020 Zementinjektionen in Verpressversuchen in verschiedenen Varianten getestet, um deren Eignung festzustellen, bzw. die Parameter und auszuführenden Arbeiten zu optimieren. Die Versuche und die dabei gemachten Untersuchungen ergaben interessante Erkenntnisse über den Zustand des Stollens. Die Injektionen erfolgten bei niedrigem Druck, wurden in verschiedenen Abständen und Bohrtiefen ausgeführt und dabei wichtige Parameter für die spätere Ausführung getestet und Optimierungen ermöglicht. Die Porosität der Auskleidung konnte dabei wesentlich reduziert und damit die Qualität der Schale verbessert werden. Mit einer Vorher‐nachher‐messung mit Georadar konnte die Verbesserung der Auskleidung durch die Injektion nachgewiesen werden.
Eine bemerkenswerte Erkenntnis ist die Kombination aus verhältnismäßig bescheidener Qualität des Auskleidungsbetons, die dem Bau während des Zweiten Weltkriegs geschuldet ist, mit der praktisch ungerissenen und relativ dichten Auskleidung. Es zeugt von einer hohen Baukunst, dass mit den damals verfügbaren Mitteln so dauerhafte Bauwerke erstellt werden konnten.
Prefabrication has been increasingly used in buildings. It is recognised as a solution to reduce waste arising during design and construction phases. However, there is little emphasis on life cycle ...design issues for prefabricated buildings located in dense high-rise building environments. The purpose of this paper is to review the application and identify benefits and impediments of design for deconstruction and Industrialised, Flexible and Demountable building systems when applied to precast concrete construction. The paper presents the results of a comprehensive literature review, and two case studies of recently completed institutional buildings using prefabrication. The literature review shows that, so far, design for deconstruction is not a common practice in the building industry. The case studies showed some limitations such as the dense urban environment conditions and limited site area. The promotion of a closed-loop material cycle is critical to contribute to sustainability thus minimising CO2 emissions, natural resources consumption.
•Design for deconstruction is not a common practice in the building industry.•Some limitations of IFD buildings include dense urban environment conditions.•Closed-loop material cycle promotes reuse and recycling of building materials.•Closed-loop material cycle is critical to contribute to sustainability.•Life cycle design could reduce emissions and material use, and save landfill space.
•This paper presents a set of significant indicators for successfully reducing construction waste at the design stage.•Six significant indicators are deprived for effective implementation of waste ...minimization at the design stage.•The applicability and significance of the identified significant indicators are explored.•These significant indicators provide designers and project managers a useful criterion.•These can also sever as valuable references for the government to formulate related construction regulations.
Construction waste minimization at the design stage is a key strategy in effective waste reduction. However, it seems that few studies focus on exploratory factors that can significantly improve the design of construction waste minimization. This paper addresses this research gap by presenting a set of critical factors that inform and improve the practice of waste minimization design, particularly in the context of Shenzhen, China. Nineteen potential factors which can influence effective waste minimization are presented based on related official guidelines, reports and literature. Top institutions in Shenzhen that have received a Grade A building design certification were surveyed through a questionnaire. From this survey, six critical factors are derived: (1) large-panel metal formworks, (2) prefabricated components, (3) fewer design modifications, (4) modular design, (5) waste reduction investment and (6) economic incentive. The applicability and significance of the identified critical factors for effectively designing waste minimization are also explored. These critical factors not only provide designers and project managers with a useful set of criteria for effective design strategies to reduce construction waste, but also serve as valuable references for the government to formulate related construction waste minimization regulations.
Solid waste arisen from construction activities is grave concern in many economies. Given its negative impacts to the natural environment as a public good, construction waste is often heavily ...regulated by authorities. Hong Kong is no exception to this; over the past decades, a series of construction waste management (CWM) policies including regulations, codes, and initiatives have been introduced by the Government and her executive arms. It comes to an opportune time to retrospectively examine the effectiveness of these policies with a view to providing insights for further improvement. The aim of this paper is thus to examine CWM policies and their effectiveness in Hong Kong by conducting a longitudinal study. The evaluation of the policy effectiveness is derived by triangulating empirical data collected from various sources including Hong Kong Census and Statistics Department, Civil Engineering and Development Department, Environment Protection Department, and Hong Kong Construction Association with the qualitative data gleaned from interviews and case studies in construction sites, waste sorting facilities, and landfills. It is found that Hong Kong is actively trying new CWM policies based on latest waste management philosophies available (e.g. reduce, reuse, and recycle principle, and polluter pays principle). These policies have formed an interlocking, and relatively effective policy framework for CWM in Hong Kong. However, new initiatives are desired if aiming to change the gloomy situation since 2006 when the construction waste disposal charging scheme was effectively implemented. This research provides insightful understanding of CWM policies and their effectiveness, which is often concerned policies makers, researchers, and the like.
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