Cognitive Approach to Construction Safety: Task Demand-Capability Model

In the evolution of safety research, the literature identifies three paradigms: normative, error-based, and cognitive engineering. Traditionally, strategies to improve construction safety have been based on the normative paradigm—compliance with prescribed safety rules. However, the normative approach ignores how the characteristics of the production system and team processes influence the work behaviors and the possibility of errors and accidents. These factors are the focus of the cognitive engineering perspective. This study develops a cognitive model of construction safety, which conceptualizes safety as an emergent property of the production system. The model proposes that during a task, the task demands and the applied capabilities determine the potential for errors and accidents. It also proposes that the production practices and the teamwork processes of the crew shape the work situations that the workers face—that is, the task demands and the applied capability. Empirical evidence from recent case studies is discussed. The cognitive perspective shifts the focus of accident prevention from conformance with rules to the issues of task demands and applied capabilities, and the factors affecting them—such as work design, workload, resource allocation, and team processes.     

Simulation of Concrete Paving Operations on Interstate-74

The objective of this paper was to study and optimize the concrete paving operations taking place in the reconstruction project of Interstate-74 using computer simulation. To achieve this objective, field data were collected during construction, and were then used to determine adequate probabilistic density functions for the activities’ duration and to test a developed simulation model. Upon testing, the developed model was used to study the impacts of resources on the flow of operations and on the cost effectiveness of the construction process. In general, application of simulation methods to concrete paving operations was successful and its accuracy was acceptable as compared to field measurements. Based on the results of a sensitivity analysis of the critical resources, multiple factors were considered in the decision-making process to ensure that all aspects of the operation are evaluated. This includes total operation time, productivity, costs of the operation, average truck delay, and idle times for the paver and the spreader. For the conditions pertinent to this construction site, ten trucks, one paver and one spreader, and three finishing and plastic-covering crews are recommended. Using this set of resources would result in a prompt and effective execution of the operation. Practical implementation and limitations of the developed model in similar construction operations is discussed.     

Predictive Tool for Estimating Accident Risk

This paper presents a predictive tool that uses safety factors to estimate accident risk for processes commonly employed on construction sites. The tool is demonstrated in the context of the utility-trenching process. Based on expert surveys, preplanning, supervision, and training are identified as critical safety factors needed to predict accident risk when evaluating safety performance related to trenching operations. Preplanning has a greater impact on excavation tasks than supervision and training, while conversely, supervision and training are more important during the pipe installation phase of trenching operations.     

Algorithms for Automated Monitoring and Control of Fall Hazards

Most lethal accidents in construction are caused by falling from heights. Researchers point out the importance of safety control, carried out systematically and based on real-time data collection, as the most important element of accident prevention. An automated model to monitor and control fall hazard was developed. The model identifies the activities associated with risk of fall from heights and the areas where these activities are scheduled to be performed and plans the protective measures—guardrails in the present case. The model is designed to follow up the existing guardrails and constantly compare their locations and lengths to the planned ones. Based on this comparison, the model issues warnings whenever guardrails are missing, or temporarily removed. The model provides reports and warnings—the reports are used for planning the materials, or workers, needed to erect the protective measures. Warnings are given when a dangerous activity is performed without appropriate protective measures, or when the latter were removed before the dangerous activity was completed. The model’s main algorithms—dangerous activities and areas identification—were implemented and evaluated on site. Whereas the proposed model was developed to improve safety during the construction stage, it can be used as a useful tool during the design stage too. Including safety in the design stage, typically absent, can meaningfully improve safety during the actual construction.     

Benchmarking Studies on Construction Safety Management in China

This paper presents information by which to measure safety management performance on construction sites. In China, the conventional construction safety benchmarking approach is to assess safety performance by evaluating the physical safety conditions on site as well as the accident records, while no attention has been paid to the management factors that influence site safety. This paper is to identify the key factors that influence safety management and to develop a method for measuring safety management performance on construction sites. Based on the survey and interview data collected on safety management factors in 82 construction projects in China, the safety management index as a means to evaluate real-time safety management performance by measuring key management factors was developed. The quantified factors were compared with the commonly accepted physical safety performance index, which was derived from inspection records of physical safety conditions, accident rates, and the satisfaction of the project management team. Multifactor linear regression was conducted and the result indicates that safety management performance on site is closely related to organizational factors, economic factors, and factors related to the relationship between management and labor on site. Based on this benchmarking study, a practical safety assessment method was developed and then implemented on six construction projects. The results show that this method can be an effective tool to evaluate safety management on construction projects.     

Interpretation of Automatically Monitored Lifting Equipment Data for Project Control

Interpretation of the data that can be collected by automated monitoring systems on construction sites is the most significant challenge to providing useful management information. Distinct construction operations must be identified and associated with construction activities, so that they can be related to construction plans. Earlier research has indicated that construction equipment can be monitored conveniently and that individual equipment operations can be isolated and characterized. In this work, an approach has been developed for unique association of isolated equipment operations with planned construction activities. The approach is based on comparison of the values of various characteristics, calculated for each equipment operation, against preset filters of characteristic values for all expected basic construction activities. The composition of the set of characteristics is different for each data stream monitored and is dependent on the nature of the construction activities. The method has the distinct advantage of ensuring the uniqueness of each filter within the collection of filters when the system is calibrated at the start of any project, rather than during online data processing. In this way, rapid and accurate interpretation of monitored data can be guaranteed. The method was tested using data collected during construction of a high-rise office tower.     

Reengineering of Construction Management Process

Applying the business process engineering philosophy, this study focuses on developing a construction management process reengineering (CMPR) method to improve the efficiency of construction management. The CMPR method includes four phases, namely, process representation, process transformation, process evaluation, and reengineering activity. Using CMPR, inefficient operations within a construction company working process can not only be identified, but a new rational operation process can also be developed to improve management efficiency. In this way, the competitive ability of a construction company is also increased. This study argues for the need of a new research agenda in construction management in general. This is illustrated by information technology within construction—in particular, by examining the potential application of the reengineering philosophy. The research possibilities are identified and tested based on the implementation of the CMPR method. To some extent, this study establishes a new agenda of process reengineering for future research.     

地下矿山生产接续与设备调度集成优化模型

为了实现地下金属矿山生产接续的紧凑性、科学高效地调度生产设备,针对矿山开采工序复杂、设备资源有限、生产任务量大等特点,以最短工序时间间隔和最短总完成时间为共同优化目标构建了地下矿山生产接续与设备调度集成优化模型.通过分析地下矿山生产循环顺序、作业设备类型和生产能力等生产要素,考虑工序闲置期间采场的安全隐患问题,运用改进遗传算法对最优解进行主-从两步骤搜索,得到地下矿山生产接续和设备调度最佳方案.以国内某大型金矿为案例进行了模型的有效性验证,解算出矿山最优的设备调度计划.验证结果表明,与传统的单一目标优化相比,模型在保证完成指定任务的同时,有效缩短工序时间间隔,并且保证了作业的安全要求.     

Analysis of Residential Framing Accidents, Activities, and Task Demands

Framing contractors have the highest rate of nonfatal incidents among specialty contractors. This case study analyzes 654 safety incidents that occurred over a period of 5??years in a large residential framing company. Accident analysis and interviews with safety and production experts identify the high-risk tasks, the errors that lead to incidents, and the task factors that increase the likelihood of incidents. The analysis resulted in a framework of five task factors that increase the task demands: (1) working platform constraints; (2) ergonomic postures constraints; (3) material/load handling requirements; (4) tool use/accuracy requirements; and (5) difficulties due to external forces. The combined effect of these factors determines the task difficulty and the likelihood of incidents. The paper discusses safety measures to reduce the task demands of the high-risk tasks, as opposed to measures that reduce exposure or mitigate the consequences. Reducing task demands can reduce the likelihood of accidents while at the same time increasing productivity. For practitioners, the study points to the need to understand the high-risk tasks and reduce task demands in their operations. The framework of the five task demand factors provides the “building blocks” of task difficulty for framing tasks and provides directions for further research in understanding and mitigating the combined effect of the task demand factors.     

Spatial and Temporal Exposure to Safety Hazards in Construction

Given the dynamic nature of construction sites, analysis of construction activities and their related hazards is inadequate for reliable risk assessment if it does not explicitly account for the likelihood of exposure of potential victims to hazardous situations. In traditional risk level calculations for manufacturing industries, the number of victims is factored with the likelihood of an accident and the potential severity, but the victims are simply assumed to be those typically present at the accident location. In construction, exposure cannot be accounted for at a generic metaproject level: it must be assessed at the level of the activities and the physical context in which they are performed. Conceptually, accidents are “loss-of-control events” to which victims are exposed; without exposure, no accident is assumed to occur. A set of algorithms has been developed to demonstrate estimation of the likelihood of exposure of construction workers to loss-of-control events. The algorithms have been implemented in a prototype software application designed to predict fluctuating risk levels in construction projects. The software implements the “construction hazard assessment with spatial and temporal exposure” model for managing safety in construction, which empowers planners at all levels to adjust construction plans to mitigate high levels of risk or to undertake appropriate proactive measures to ensure safety when high risk levels are unavoidable.     

Interactive 3D CAD for Effective Derrick Crane Operation in a Cable-Stayed Bridge Construction

The high expectation of esthetic and functional quality in modern civil infrastructure has resulted in the increased demand for long span bridges. In advanced or developing countries, long span bridges such as cable-stayed and suspension bridges are considered even as landmarks that symbolize the prosperity or culture of the region. These long span bridges require higher level of design and construction technologies than other types of bridges. In particular, the construction of cable-stayed bridges involves precise and sophisticated operation of construction equipment such as derrick cranes. However, it is not easy to plan the operations of a derrick crane before the actual construction process takes place. Unexpected spatial constraints in the construction site may hinder the smooth operation of a derrick crane, which leads to lower than expected productivity and safety. This study applies interactive three-dimensional (3D) computer aided design (CAD) to the derrick crane operation for the purpose of identifying potential problems. Construction managers can have the two way process with the 3D CAD system to interactively test their construction plans and scenarios. The case study shows that the interactive 3D CAD system significantly improves the constructability of the cable-stayed bridge construction.     

Computer Vision-Based Video Interpretation Model for Automated Productivity Analysis of Construction Operations

Videotaping is an effective and inexpensive technique that has long been used in construction to conduct productivity analyzes. However, as schedules of modern construction projects become more and more compressed, the limitation of video-based analysis—intensive manual reviewing process—contrasts sharply with the need for effortless data analysis methods. This paper presents a study on developing a video interpretation model to interpret videos of construction operations automatically into productivity information. More specifically, this research formalizes key concepts and procedures of video interpretation within the construction domain. It focuses on designing a mechanism for furthering the crosstalk between the prior knowledge of construction operations and computer vision techniques. It uses this mechanism to guide the detection and tracking of project resources as well as work state classifications and abnormal production scenario identifications. The resulting approach has the potential to provide a common base for developing automated video interpretation procedures that can greatly improve current data collection and analyzes practices in construction. Experimental results from preliminary studies have shown the potential of the proposed video interpretation method as an improved productivity data analysis method.     

Development of Causal Model of Construction Accident Causation

Accidents occur in all types of construction activities. The accident causation process is complex. Accident prevention requires a comprehensive understanding of this complex process. This paper proposes a conceptual, but practical, model of accident causation for the construction industry, highlighting the underlying and complex interaction of factors in the causation process. The model describes the constraints and responses experienced by the parties involved in project conception, design, and construction, which may affect accident causation. This paper details theoretical findings of research currently being conducted at UMIST. Both proximal and distal factors are considered (for example, operative factors, site environment and systems of work, and project management and organizational issues). A study of 500 accident records provided by the U.K. Health and Safety Executive shows that accidents in construction projects involve inappropriate construction planning (28.8%), inappropriate construction control (16.6%), inappropriate construction operation (88.0%), inappropriate site condition (6.0%), and inappropriate operative action (29.9%). Data currently available are, in some respects, inadequate and will need to be supplemented, in the future, by extended accident investigations.     

Decisions in Construction Operations

A method for selecting the most desirable construction strategy is proposed in this paper. A decision analysis framework is developed considering the information on relative risk, along with the information on cost, benefit, and consequences of each construction strategy. Many factors affect the safety of construction operations. Labor skill, supervisors' experience and attendance, condition of falsework, weather conditions, type of equipment, level of operator's experience, etc., may be considered as the main factors that affect the safety of construction operations. From an engineering point of view, these factors are always desirable to be in their best states. However, it may not be practical in many cases due to time and money constraints. Consequently, the risk of failure and cost of construction operations, and the consequences of failure need to be estimated in order to decide about the optimum construction strategy. The decision problem is complicated since the state of the factors are generally expressed in linguistic terms. The theory of fuzzy sets is used to translate these terms into mathematical measures and to estimate the risk of failure. The proposed method is illustrated with the help of an example.     

氧化铝厂赤泥堆场库区防渗层的处理

氧化铝生产排出的废弃物-赤泥,是腐蚀性的危险废物,为防止对地下水、土污染,满足环保要求,做好赤泥堆放的防渗处理具有重要意义。本文详细阐述了场地土石方开挖、场地整平、土工布铺设、粘土垫层铺设、防渗膜铺设、覆土层铺设等施工方法,以及安全文明施工的保证措施,为以后类似工程施工提供可参考的资料。     

那林金矿全面留矿法试验研究

针对广西凤山那林金矿的矿床开采技术条件以及矿山近年的开采情况而提出多分段喷锚支护全面留矿法开采方案,目前该矿正在试验研究之中;可以预计,通过应用多种多样的施工技术,会满足矿山生产技术要求,尤其是采矿与出矿方面的安全作业要求,并可满足矿山生产能力需要。     

深埋硬岩隧道围岩参数概率反演方法

在贝叶斯理论框架下, 提出了一种基于多源数据融合的深埋硬岩隧道围岩参数概率反演方法.首先, 分析硬岩隧道常用的启裂-剥落界限本构模型中围岩单轴抗压强度、启裂强度与抗压强度比及抗拉强度三个参数不确定性来源, 确定其概率统计特征; 其次, 利用粒子群算法优化多输出支持向量机, 建立反映反演参数与隧道监测数据间非线性映射关系的智能响应面; 最后, 结合贝叶斯分析方法构建概率反演模型, 运用马尔科夫链蒙特卡洛模拟算法实现了围岩参数的动态更新.将该方法应用到某深埋硬岩隧道中, 利用反演的围岩参数计算隧道拱顶下沉点、周边收敛点变化值及开挖损伤区深度, 与监测数据吻合较好.结果表明, 该方法可以实现围岩多参数快速概率反演, 更新后的参数可用于硬岩隧道施工安全风险评估与结构可靠性设计.      

Predicting Industrial Construction Labor Productivity Using Fuzzy Expert Systems

The objective of this technical note is to illustrate the application of fuzzy expert systems to the modeling of a practical problem—that of predicting the labor productivity of two common industrial construction activities: rigging pipe and welding pipe. This note illustrates how to develop and test such a model, given the realistic constraints of subjective assessments, multiple contributing factors, and limitations on data sets. The factors that affect the productivity of each activity are identified, and fuzzy membership functions and expert rules are developed. The models are validated using data collected from an actual construction project. The resulting models are found to have high linguistic prediction accuracies. This note is of relevance to researchers by demonstrating how a fuzzy expert system can be developed and tested. It is of relevance to industry practitioners by illustrating how fuzzy logic and expert systems modeling can be exploited to help them solve real world problems.     

FTA在某地下矿运输事故安全评价中的应用

FTA是安全系统工程中的重要分析方法之一。本文采用FTA法对云南省某地下矿可能发生的运输事故作了定性及定量分析。通过对运输事故的分析,构造地下矿运输事故的事故树,找出发生事故的主要因素。