Analyses of Instability in Mobile Cranes due to Ground Penetration by Outriggers

This study focuses on the phenomenon of ground instability causing mobile cranes to overturn. Four outriggers usually support a mobile crane in order to restrict pitching during hoisting operations. Nevertheless, the crane may become quite unstable if the outriggers should happen to sink into the bearing ground. In this paper, various types of analysis, including experiments, were performed in order to investigate the influence of ground penetration by outriggers on the stability of mobile cranes. Through study of the results of experimentation and simulation, it has been clarified that mobile cranes become highly unstable as a result of rapid penetration. It was found that an index of relative instability had a linear relationship to the common logarithm of an index for brittle failure as derived from the load–settlement curve for ground penetration. Finally, a method of evaluating the risk of mobile-crane overturning is proposed by using the maximum value of both the supporting surface’s failure risk and the kinetic risk due to ground penetration.     

Crane-Related Fatalities in the Construction Industry

One of the major causes of fatalities during construction is the use of cranes or derricks during lifting operations. Using the Occupational Safety and Health Administration’s (OSHA) case files from fatality investigations during the years 1997–2003, the writers examined the data to determine the proximal causes and contributing physical factors. The research results showed the use of mobile cranes with lattice and telescopic booms, truck or crawler mounted, represented over 84% of the fatalities in the use of cranes/derricks. To reduce the rate of crane fatalities the writers believe that crane operators and riggers should be qualified and requalification should occur every 3?years. Crane safety training must be provided to specialty trade crafts before they are allowed to work around cranes during lifting operations. In addition, a “diligent” competent person [as defined in 29CFR 1926.32(f)] should be in charge of all aspects of lifting operations. Finally, OSHA should improve its system of collecting information during fatality investigations, placing emphasis on intervention strategies to improve usefulness of the investigations to researchers and policymakers inside and outside the Agency.     

Innovative System for Off-the-Ground Rotation of Long Objects Using Mobile Cranes

Managing heavy-pressure vessel lifts on construction sites requires planning, arranging adequate crane support, and preparing collision-free rotation (from a horizontal position to a vertical position) of the vessel. Generally, selecting mobile cranes and developing engineered lift studies for vessels are done using two cranes and analyzing the lift for each crane individually on the basis of the selected cranes’ lift-capacity specifications provided by crane manufactures. This practice is relatively costly and time-consuming. Optimizing the mobile cranes’ use and location is also difficult. To assist in the field operation of mobile cranes and to provide engineers with a planning tool, this paper presents a methodology to carry out such a lift utilizing only one crane. Using the developed methodology and mechanism, heavy vessels can be rotated off the ground (in the air) with one crane. The proposed mechanism is supported with a mathematical model that has been developed into a computer system and has been integrated with a previously developed crane selection and ground pressure calculation system and crane database. The developed system provides users with a lift study analysis for a given configuration as well as simulation results with interactive graphics to assist in the selection of an optimum configuration. This research is important as projects involving heavy lifts need to reduce the cost and time associated with construction operations.     

Optimization Algorithm for Selection and on Site Location of Mobile Cranes

Mobile crane manufacturers provide operators and practitioners with tabulated lift-capacity charts. These charts are structured based on predetermined crane configurations, which consist of boom/jib length, lifting radius, lifting height, main boom angles to ground, and jib angle to ground or its offset to its main boom centerline. Practitioners, however, are often required to lift on a partially extended hydraulic section and/or lifting radius other than those listed in the manufacturers’ lift-capacity charts. This paper presents a newly developed optimization algorithm (referred to in this paper as Algorithm-2) for selecting and locating mobile cranes on construction sites based on their minimum boom length and/or minimum radius, accordingly higher lifting capacities. Algorithm-2 includes an optimization procedure that avoids lifting capacity violations. In addition to the practical use of Algorithm 2, the mathematical representations of the crane’s geometry are also useful for research in the automation and robotic field of operations involving cranes. The algorithm is incorporated into a computer system that integrates a selection module and a database. Data pertinent to crane lift configurations are retrieved from the database and are then processed to determine the optimum, geometrical selection of the crane configuration. A case example is described in order to demonstrate the use of the developed algorithm and to illustrate its essential features.     

Simulation-Based Identification of Possible Locations for Mobile Cranes on Construction Sites

Identifying spatial-conflict free locations of mobile cranes that could minimize delays associated with crane relocation can result in productivity and safety improvements on construction sites. Existing approaches for identifying possible crane locations are based on two-dimensional (2D) work envelopes created by reasoning about the lift capacities of a crane during operations. Since spatial conflicts related to crane operations typically occur in three dimensions and during any period of operation, representing possible crane locations based on such 2D work envelopes can result in identifying some locations as good when in fact they might result in conflicts and missing possible locations that might be feasible. This paper presents an approach that determines possible locations of mobile cranes based on discrete-event simulation of crane operations incorporating dynamic behaviors of cranes. This approach starts with identifying a search space for possible crane locations by reasoning about a reachability radius of a crane determined by crane characteristics and the weight of the load to be carried. Later, it reduces the search space through boom-line intersection tests. For the remaining locations, it checks for potential spatial conflicts between building components and cranes moving in three dimensions and across time. Validation studies show that the developed approach can accurately identify possible locations for mobile cranes that minimize the relocation of mobile cranes and avoid potential spatial conflicts.     

Algorithm of Crane Selection for Heavy Lifts

Lifting capacity charts are tabulated and provided to operators and practitioners by mobile crane manufacturers. These charts are structured based on predetermined crane configurations, which consist of boom/jib length, lifting radius, main boom angle to ground, and jib angle to ground or its offset to its main boom centerline. It is a tedious job that lifting planners select cranes for construction projects based on a large number of lifting capacity charts. This paper presents a newly developed algorithm for selecting mobile cranes on construction sites, which takes into account the lifting capacity, the geometrical characteristics of the crane, the dimensions of equipments and riggings, and the ground bearing pressure. The algorithm is incorporated into a three-dimensional (3D) computer-aided system that integrates crane selection module, crane modeling module, 3D-simulation module, 3D computer-aided design modeling module, rigging calculation module, and data management module. At last, a case is represented in order to demonstrate the use of the developed algorithm and to illustrate its essential features.     

Cranes for Building Construction Projects

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. Sophisticated electronic controls and operator assistance devices are enhancing their safe and productive operation. While cranes occupy a central role on midrise and high-rise building projects, they operate in conjunction with other types of supporting equipment that are an essential part of the overall equipment array on today’s industrialized construction sites.     

Dynamic Analysis of Tower Cranes

Tower cranes are widely used in the construction of high-rise buildings and the analysis of their dynamic behaviors is of both theoretical and practical significance. A parameterized super element formulation for modeling the multiple-pulley cables in a crane system is proposed based on the friction-free assumption between the cable and pulleys. The cable passages over intermediate pulleys are considered as new degrees-of-freedom in the proposed element model and equal tensions at different segments of a continuous cable are exactly achieved. Numerical results show that these cable passages have significant effect on both static tensions and dynamic properties of tower cranes and the proposed super element model provides more accurate and realistic results in dynamic analyses of the crane system. It is found that some modes are insensitive to the change of jib angle or bracings at crane mast, while others change drastically depending on the mode shapes. Picking up the payload from ground or payload accelerating/decelerating during lift operation will induce finite impulsive excitations and, therefore causes noticeable dynamic responses of the crane system.     

液压履带起重机变幅运动的动力学仿真

用机器人动力学方法建立了液压履带起重机变幅运动时的多刚体动力学模型,用牛顿－欧拉方法得到载荷摆振的动力学方程。给出了各杆件的受力的递推公式,为起重机设计和载荷摆振控制提供了理论依据。用数值方法求解了系统动力学方程,对变幅运动过程进行了数值仿真。     

Adaptive Probabilistic Neural Network-based Crane Type Selection System

Due to the central role of cranes in construction operations, specialists in the construction industries have cooperated in the development of structured methods and software for crane selection. Most of these software tools are for crane model selection, and integrated systems that handle both crane type and model selection are not readily available. This paper presents the crane type selection features of IntelliCranes, a prototype integrated crane selection tool that assists in both crane type and crane model selection based on a set of inputs describing the construction operation under consideration. By using historical data and advanced artificial intelligence computing tools such as artificial neural networks, IntelliCranes automates crane type selection. Crane type and crane model selection are seamlessly integrated in a comprehensive crane selection tool, and consistency in the selection of cranes for similar situations is increased.     

酒钢连铸车间冶金行车限位保护系统优化

限位保护是冶金铸造行车控制的最重要一环,国家为此制定专门的行业规定。碳钢薄板厂连铸车间冶金铸造吊限位保护亦不能完全满足安全生产的需要,因此对其进行系统的优化改造,以增加冶金铸造吊运行的可靠性和安全性。     

热装模式下板坯库动态调度系统研究与应用

针对钢铁企业热装模式下板坯库作业动态调度的需求,采用Petri网对热装模式下辊道输送作业、板坯入库作业和出库作业进行详细、系统的分析,提出了辊道输送控制策略和天车动态调度策略,在此基础上研发了板坯库动态调度系统。2011年系统在某钢铁集团热轧薄板厂板坯库实际运行后,实现了板坯库辊道输送的自动控制以及天车的动态调度,验证了本文提出的动态调度方法的可行性及有效性。     

狭窄厂房空间150t钢包回转台安装方案介绍

针对狭窄厂房空间150 t钢包回转台的安装,研究设计了专用的两跨双台行车联合抬吊方案。设计和制造了双台行车联合抬吊的平衡梁吊具,并针对小曲率穿索半径,设计制造了专用的尼龙吊带进行穿索吊装。通过结合过渡支架平台的设计安装,运用两跨双台行车联合抬吊的新方案,成功实施了狭窄厂房空间150 t钢包回转台的安装,并保证了安装精度,安装过程安全可靠。     

大型铝电解操作天车的电磁场计算和受力分析

利用ansoft软件对铝电解天车磁场分布进行有限元仿真,通过对有无建筑物比对,有建筑物时的磁场强度和工厂测试值较接近。证明了模型的合理性。分析了天车在不同状态受到磁场的作用不同,天车静止时受到磁场主要作用在端梁上,并直接产生竖直向下其大小为290~430 kN的作用力,远大于天车运动时产生的电磁力,会导致天车启动困难;天车水平面合力为零,但内部因受到磁场的作用力都达200kN以上,会造成天车的扭曲变形。天车运动时,不仅在端梁上产生向下的250~300 kN作用力,同时天车整体会产生一个120~195kN侧向力,导致天车朝导向轮一侧跑偏。     

旁油路节流调速在CC1000履带起重机回转制动回路中的应用

旁油路节流调速与其它油路节流调速相比，性能较差（主要指速度负载特性），一般很少应用。而曼内斯曼德马克公司生产的ＣＣ１０００履带式起重机，在上车回转制动回路中，巧妙地应用了旁油路节流调速，交不利为有利，收到了良好效果。     

Measurement and Risk Scales of Crane-Related Safety Factors on Construction Sites

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.     

焦罐车旋转机构支承辊轮运行状态的探析

对焦罐车旋转机构支承辊轮的运行状态进行了分析。探讨了焦罐车旋转机构支承辊轮的三种型式：圆柱辊轮、腰鼓形辊轮及圆台形辊轮在运行状态下的滚动、磨损、效率。总结出支承辊轮的理想运行状态。     

Computational Methods for Coordinating Multiple Construction Cranes

The incremental coordination method a computational method for preplanning and coordinating the use of multiple tower cranes in relatively narrow construction sites is presented. The incremental coordination method considers the kinematics and the geometrical constraints of cranes to plan the motion of two or more cranes, which are being operated in collaboration. By following such planned motions, erection tasks are completed safely, even when the cranes are operated in close proximity of each other. This method allows the use of computers to plan and coordinate the crane activities from start to end of an erection process. This paper also explains the computational methods required by the incremental coordinate method including path-finding and collision detecting methods. An example case shows two construction cranes, each of three degrees-of-freedom, operating together on a building project where the working areas of the cranes intersect, hence possibility colliding with each other. A numerical test was conducted to verify the efficiency and effectiveness of applying the incremental coordination method in planning and synchronizing all motions of the two cranes to avoid any collision between the cranes themselves and collision with obstacles on the construction site.     

Automated Path Planning of Cooperative Crane Lifts Using Heuristic Search

The use of cooperative cranes can improve the cost effectiveness of heavy lift operations. However, the complexity in developing a reliable lift plan prevents the widespread use of cooperative crane lifts. The availability of a computer-aided planning system can improve planning efficiency and reliability. Path planning is an important subtask of the lift planning process. This paper presents work done to develop a computer aided path planner for two crane lifts. Two heuristic search methods, hill climbing and A?, were implemented for automating the path-planning task. Search space was represented using the concept of configuration space. The effectiveness of the search methods was evaluated by solving three problems with increasing levels of complexity. The formulation of these problems was based on the type of movement of cooperative cranes (in synchronous or asynchronous manner) and the presence of trapping space. It was found that while the hill climbing approach found feasible paths in a few seconds or minutes, these paths were far from optimal in situations containing trapping space. In contrast, the A? search resulted in near optimal paths, but the execution time was of the order of hours.