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.     

Windmill Erection and Maintenance: Challenges for Crane Design

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.     

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.     

Collision Free Path Planning of Cooperative Crane Manipulators Using Genetic Algorithm

This paper presents a new approach for automated path planning of cooperative crane manipulators using a genetic algorithm (GA). The inverse kinematic problem, i.e., determining the joint angle configuration for the cooperative crane manipulator system in moving the object from pick location to place location, is defined as an optimization problem and solved using GA. For generating the collision-free path, GA with an interference detection algorithm is employed and search is made in the manipulator joint angle space (configuration space). The effectiveness of the proposed approach for automated path planning is demonstrated by comparing the performance of the present approach with the earlier heuristic search proposed by Sivakumar et al. The GA approach finds a near-optimal path with lower path cost and less computational time than earlier heuristic searches.     

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.     

Lampson Transi-Lift Mobile Crane: Concept, Design, and Use

The Lampson Transi-Lift mobile crane is a lifting system purposely designed for construction activities related initially to nuclear power facilities. The combination of capacity, increased working hook height, and an unmatched radius to capacity ratio allowed for use of innovative construction techniques that decreased the construction schedule, increased facility integrity and construction safety, and reduced overall plant construction costs. The versatility of the Lampson Transi-Lift was immediately recognized, and it has become a mainstay of the heavy lift industry since its introduction in the late 1970s. Oil and gas, general construction, and offshore construction activities have all since benefitted from the unique capabilities of this heavy lift crane     

大吨位铸造吊主起升结构形式探讨

结合国内在用多台大吨位铸造吊的使用情况 ,分类比较了它们的主起升结构形式 ,并详细分析了各种结构的优缺点 ,为大吨位铸造吊主起升机构选型提供了一定的指导     

“Soft” Considerations in Equipment Selection for Building Construction Projects

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.     

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.     

Algorithm for Generating Samples of Homogeneous Gaussian Fields

A new algorithm is developed for generating samples of stationary Gaussian random fields. The algorithm is based on a model derived from the spectral representation theorem for weakly stationary random fields. The model consists of a superposition of a random number of waves with random amplitude and frequency, can match the second moment properties of any target random field, and becomes Gaussian as the intensity of two independent Poisson processes, defining the number of waves and their frequencies, increases indefinitely. In contrast to the current Monte Carlo simulation algorithms, the proposed algorithm: (1) does not produce periodic samples; and (2) does not require the discretization of the frequency domain. The proposed Monte Carlo algorithm is applied to generate samples of a stationary Gaussian field defined on 2.     

Evaluation of a Genetic Algorithm for the Irrigation Scheduling Problem

A typical irrigation scheduling problem is one of preparing a schedule to service a group of outlets which may be serviced simultaneously. This problem has an analogy with the classical earliness/tardiness problem in operations research. In previously published work an integer program was used to solve this problem, however such scheduling problems belong to a class of combinatorial problems known to be computationally demanding (N-P hard). This is widely reported in operations research. Hence integer programs can only be used to solve relatively small problems usually in a research environment where considerable computational resources and time can be allocated to solve a single schedule. For practical applications metaheuristics such as genetic algorithms, simulated annealing, or tabu search methods need to be used. However as reported in the literature, these need to be formulated carefully and tested thoroughly. This paper demonstrates the importance of robust testing of one such genetic algorithm formulated to solve the irrigation scheduling problem with simultaneous outlets serviced against an integer program formulated to solve the same problem.     

钼精矿加压氧化过程中添加剂的选择

就硫酸、氧化钙、木素磺酸盐、铜铁离子等多种添加剂对钼精矿酸性加压氧化浸出工艺中钼转化率的影响进行了研究。试验结果表明:氧化钙不利于钼的转化,钼以钼酸钙的形式进入渣中,较难被浸出;木素磺酸盐、硫酸、铜铁离子等对钼转化率影响较小,在加压氧化过程中不建议进行添加;新型添加剂可有效提高钼的转化率,且可有效提高矿浆的流动性,降低矿浆黏度,有利于实现过程的连续化生产。     

Nonlinear Error Propagation Analysis for Explicit Pseudodynamic Algorithm

A technique to evaluate the error propagation of the pseudodynamic testing of a nonlinear system is proposed. This technique mainly relies upon the introduction of the degree of nonlinearity to describe the variation of stiffness for each time step. The commonly used Newmark explicit method is chosen for this study and it is analytically proved that the upper stability limit is enlarged for the case of stiffness softening and is reduced for the case of stiffness hardening. These theoretical results are thoroughly confirmed with numerical examples. It is also theoretically and numerically verified that for each time step stiffness softening encounters less error propagation while stiffness hardening experiences more severe error propagation than for the stiffness invariant case. This is because stiffness softening results in the decrease of the natural frequency and the value of the degree of softening nonlinearity while stiffness hardening leads to the increase of the natural frequency and the value of the degree of hardening nonlinearity.     

重载提升台同步液压系统仿真设计

介绍采用D&C system simulator软件,对重载提升台两只油缸同步液压系统仿真设计。通过对两只液压缸升降过程同步精度(相对位置误差)和速度稳定性进行分析,对存在的问题进行了改进,保证了液压系统运行平稳可靠。     

Efficient Algorithm for Computing Einstein Integrals

Analytical approximations to Einstein integrals are proposed. The approximations represented by two fast-converging series are valid for all values of their arguments. Accordingly, the algorithm can be easily incorporated into professional software like HEC-RAS or HEC-6 with minimum computational effort.     

DETRANS: Efficient Algorithm for Static Analysis of Determinate Trusses

A fast and storage‐efficient algorithm for the computation of the static response of determinate trusses to nodal loading is proposed. In terms of the number of bars in the truss, M; the algorithm is of computational complexity O(M2) and requires only O(M) primary storage, for M linearly independent loadings. The motivation to develop a fast algorithm stems from the need for such an algorithm in the fast and efficient control of adaptive space cranes. The algorithm is based on the well‐known method of joints. Although the traditional method of joints computes response only for simple determinate trusses, the algorithm includes the extension for the compound and complex determinate trusses by generalizing the Henneberg method. It has been coded in FORTRAN77 into a computer program called DETRANS (Determinate Truss Analysis System). The theoretical basis of the algorithm, the data structures used in the program, and the computational complexity analysis are given.     

Integrated Genetic Algorithm for Optimization of Space Structures

Gradient‐based mathematical‐optimization algorithms usually seek a solution in the neighborhood of the starting point. If more than one local optimum exists, the solution will depend on the choice of the starting point, and the global optimum cannot be found. This paper presents the optimization of space structures by integrating a genetic algorithm with the penalty‐function method. Genetic algorithms are inspired by the basic mechanism of natural evolution, and are efficient for global‐searches. The technique employs the Darwinian survival‐of‐the‐fittest theory to yield the best or better characters among the old population, and performs a random information exchange to create superior offspring. Different types of crossover operations are used in this paper, and their relative merit is investigated. The integrated genetic algorithm has been implemented in C language and is applied to optimization of three space truss structures. In each case, an optimum solution was obtained after a limited number of iterations.     

Semi-Implicit Integration Algorithm for Stochastic Analysis of Multi-Degree-of-Freedom Structures

This paper presents a semi-implicit integration algorithm for random vibration problems that is appropriate for analyzing large structures, nonlinear hysteretic systems, and structural control problems. This semi-implicit approach results in a recursive expression for the mean and covariance response. A state-space representation of the equations of motion is adopted for deriving the algorithm. The solution of the state-space equations is first obtained, after which the expected value of the resulting equations is taken so as to obtain the first two moments. A stability condition for the method is also derived. Three numerical examples, a linear oscillator, a Duffing oscillator, and a multi-degree-of-freedom system with hysteretic supplemental damping devices, are provided to illustrate the effectiveness of the proposed method. Results compare well with Monte Carlo simulation, indicating that the semi-implicit integration algorithm is accurate and stable.