Construction Production Planning

A new branch of optimization, Optimal Control Theory, is used as a computational method to formulate and solve construction production planning problems. An example of the literature, Griffis' application of queueing theory to determine the optimal number of trucks to perform an earthmoving job, is used. It is shown that under the presence of weather varying conditions, optimal production rates may be time varying. A feedback solution is found. The implications of such solution are discussed. A simulation is performed to compare the use of varying and constant production rates.     

Fuzzy Clustering Model for Estimating Haulers’ Travel Time

This paper presents a two-step fuzzy clustering method for estimating haulers’ travel time. The proposed method provides a generic tool that can be incorporated in models dedicated for estimating earthmoving production. The estimated travel time takes into account the acceleration and deceleration in the transition zones. The developed method utilizes linear regression and fuzzy subtractive clustering. Seven factors influencing haulers’ travel time were first identified and their significance was then quantified using linear regression. The regression analysis was performed utilizing 180 training cases, generated using commercially available software for different models of haulers. The data were generated randomly to represent a wide range of possible combinations of factors affecting travel time of haulers across different types of road segments. The training data were subsequently used in the development of the proposed method. Unoptimized subtractive clustering, optimized Takagi–Sugeno zeroth-order subtractive clustering, and optimized Takagi–Sugeno first-order subtractive clustering were used in estimating haulers’ travel time. Their performance was evaluated using 36 test cases, also generated randomly in a similar manner to those utilized for training. The optimized Takagi–Sugeno first-order subtractive clustering model was found to outperform the other two, and was accordingly used in the proposed method. A numerical example is presented to demonstrate the use of the developed method and illustrate its accuracy.     

Past and Future of Construction Equipment—Part IV

The development of construction equipment has followed the major changes in global transportation. In 1420, Giovanni Fontana was dreaming of and diagramming dredging machines. Development of the steam shovel was driven by a demand for an economical mass excavation machine to support the era of railroad construction. The Cummins diesel engine was developed in the early 1900s as the road-building phase of transportation construction began. In the short term, the basic machine frame will not change, but productivity, accuracy, and utility should improve because of enhancements. Machines will evolve into a mobile counterweight driven by an energy-efficient powerplant. This mobile counterweight will serve as a work platform for an array of hydraulic tools, and it will have synthesized computers that instantly communicate by satellite with distant management teams reporting diagnostics, production, and position.     

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.     

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.     

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.     

SERC—A Model for Estimating Construction Inputs

One of the main problems in the process of design and management of construction projects is obtaining accurate information for preliminary estimates. This information is crucial for the development of integrated systems for construction management because of the relationship between construction input data and subjects such as estimating, cost control, scheduling, resource management, etc. Existing methods for estimating input that originated in industrial engineering are inadequate for the unique conditions of the construction industry. The model described in this paper applies statistical analysis of data from past projects, and enables the user to estimate the data needed for the construction of a new project. The model is based on the following components: Project items and their quantities; inputs needed to produce those items; and factors that affect inputs of a specific project. The model equation was calculated using multiple regression techniques. The paper concludes with a case study of a construction input configuration for a concrete structure.     

“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.     

Estimating Performance Time for Construction Projects

The prediction of performance time for construction projects is a problem of interest to both researchers and practitioners. This research seeks to gain insight into the significant factors impacting construction duration by developing a regression model. Data were collected for 856 facility projects completed between 1988 and 2004. These data were analyzed using Bromilow’s time-cost (BTC) model (1969) as well as multiple linear regression. The multiple linear regression model was found to provide the most acceptable prediction. As in the BTC model and previous research reported in the literature, a significant correlation was found to exist between cost and duration. However, several other factors were also identified that resulted in significantly lower than average construction durations. These include projects completed within certain management groupings, managed by a certain construction agent, and designed by in-house personnel.     

人工挖孔桩在施工中几个特殊问题技术处理

近几年,全国许多地区采用了人工挖孔桩,并得到推广,其特有的大承载力优势得到了许多设计、施工单位的认可,确实是一种在软弱地基上经济适用的基础形式,但在施工中还存在着一些问题,我们在通过对采用人工挖孔桩基础的工程实践中,积累了一些经验,处理了一些特殊的问题,取得了良好的效果。     

国外厚板生产线工艺及设备特点

本文介绍了国外5000mm左右轧机厚板厂的装备情况,并对板坯热送、板形控制、控轧控冷、超声波探伤及热处理等生产技术的发展情况进行了论述。     

AHP-Based Equipment Selection Model for Construction Projects

Selection of equipment for construction projects, a key factor in the success of the project, is a complex process. Current models offered by the literature fail to provide adequate solutions for two major issues: the systematic evaluation of soft factors, and the weighting of soft benefits in comparison with costs. This paper presents a selection model based on analytic hierarchy process (AHP), a multiattribute decision analysis method, with a view to providing solutions for these two issues. The model has the capacity to handle a great number of different criteria in a way that truly reflects the complex reality, to incorporate the context and unique conditions of the project, and to allow for manifestation of user experience and subjective perception. The model was implemented in an in-house developed system that was improved and validated through testing by senior professionals. The main academic contribution of the study is in the modification of AHP to correspond with the nature of equipment selection and in its utilization as an effective means for the formalization of knowledge possessed by competent, experienced practitioners. On the practical side, the proposed model offers an efficient, convenient tool that forces the users into orderly, methodical thinking, guides them in making logical, consistent decisions, and provides a facility for all necessary computations.     

Excavation Game: Computer-Aided-Learning Tool for Teaching Construction Engineering Decision Making

This paper reports on an interactive computer-aided-learning (CAL) tool that was developed for the education of construction engineering students: the excavation game. It builds on the large potential of using CAL in education. CAL tools could offer a better learning environment for students, as they provide an excellent opportunity for applying and testing the management skills learned in classroom, but are difficult to implement in reality. In this research, the CAL tool focuses on improving students’ decision-making skills in the aspects of excavation and related activities. These are excavation equipment, dewatering, and soil-support methods. It also covers mobilization, surveying, safety, overtime shifts, and reporting. Students compete with regard to time, cost, and quality of construction of a given project. The game flow is nonlinear as it depends on students’ decisions. Wrong decisions deviate the construction flow to a path that costs money and time, while reducing quality. This must be corrected costing extra money and time. The game was tested by senior practicing engineering and university professors. Then, it was tested by senior undergraduate construction students. Both groups agreed that the game responds, to a great extent, to the characteristics of effective CAL software, and that the information provided could not be easily assimilated or practiced through the usual tutorial or demonstration educational format. 18% of the professionals and 72% of students indicated the usefulness of the game in applying management and decision-making skills. 60–70% of students believed that it improved their technical skills in dewatering, soil-support, and excavation activities. In addition, 80% of the professionals found the game presenting realistic soil-support and excavation situations, while 72% of students became more appreciative of the interdependencies between activities.     

Production System Loading–Cycle Time Relationship in Residential Construction

Production home building possesses characteristics similar to manufacturing processes, such as the construction of more or less similar houses repeatedly and a growing demand for mass customization of homes. As a result of these similarities, larger homebuilders often attempt to view their production system as an assembly line process. However, the management tools generally utilized by these home builders are those used in other sectors of the construction industry, such as critical path method scheduling, cost estimating, and earned value analysis. These management tools do not provide an explanation or control/prediction tools for many undesirable situations that arise during home building, such as increasing cycle time which slows delivery of product to consumers and increases project capital costs, and increasing amounts of work in process that increases capital investment and thereby decreases company financial performance. In order to bring better management tools to the residential construction industry, this study examines relationships between cycle time, work in process, system throughput, new construction starts, and the capacity of the production system using building permit data for new single family homes in Chandler, Ariz. The applicability of Little’s law, a basic equation used in factory production management models, to a residential production system is examined. This study shows a definite, predictable relationship between cycle time, work in process, and production system throughput. It provides a pathway for further study of production system characteristics that have historically not been included in construction management models, with the expectation of developing new construction management tools that will account for more of the characteristics of construction production systems that affect project performance and company financial performance.     

点动式自动取样机的研制及其在生产中的应用

以电磁铁为原动力,根据杠杆原理来驱动取样器机构运作,研制了点动式自动取样机。点动式取样机不仅适应了选矿厂的取样环境,而且取样技术满足选矿技术要求,解决了当前选矿厂取样工作不规范和工人劳动强度大的问题,对强化企业管理和增加效益具有十分重要的现实意义。     

Criticism of CPM for Project Planning Analysis

Published criticism in recent years concerning the inadequacy of Critical Path Method (CPM) as a project planning tool is identified and grouped under six major headings with reference to the publications in which the criticism were contained. These are answered from the writer's field experience and from experiences published by other authors. The object of the analysis is to see whether or not CPM as a project planning tool can meet the required functions of planning in construction, including consideration of legal and contractual framework and the complex and interdisciplinary nature of the project environment. The analysis reveals that, despite numerous criticism, project and construction planning should be done using CPM scheduling. Main factors affecting successful planning are realistic estimation of the productivity of crews in the context of expected job‐management efficiency conditions, and inclusion of sufficient time buffers between dissimilar trades. CPM is found to be equally useful as a planning tool for linear or repetitive projects. The limitations of this technique are identified in terms of the defined planning functions in the engineering phase of capital projects. A broad model for management of the engineering phase in revenue‐generating projects is suggested.     

Case for Drug Testing of Construction Workers

Drug use has been shown to have a negative affect on both job safety and productivity. Due to the high accident rates in the construction industry it is vital for management to take necessary steps to implement programs and procedures that will increase construction safety and worker productivity. While the effects of a drug-related jobsite accident can be catastrophic for individuals and companies, management should realize that drug use among employees can be damaging to moral, productivity, and quality even if it does not result in accidents. The level of teamwork required for excellent work is harder to achieve and efforts to improve project management by team building are hurt by the absenteeism and short-term employment typical of the employee that abuses drugs. Other areas where the project management of a construction company is compromised by worker drug use are recruitment and retention of human resources, career growth management, and safety. Drug testing construction workers is an effective method for reducing the number of impaired workers on a project site, increasing overall project safety, worker morale, productivity, and profits. There are ethical and legal questions on both sides of the issue and any such management initiative must be balanced with worker rights.     

Implications of Even Flow Production Methodology for U.S. Housing Industry

Production building in the residential sector is often described as the portion of the construction industry that is most like the manufacturing sector. In modern tract construction in the United States, a small number of models are generally repeated several times in a relatively confined area, using specialized trade contractors to complete each phase of each home. Management of the handoffs between predecessor and successor trade contractors is therefore a critical component in the successful completion of a residential project. In order to bring more reliable planning to this process, a workflow-leveling strategy known as even flow production has come into use in the industry in recent years. Even flow production is a strategy intended to reduce the variability in the workflow for trade contractors in the process, thereby gaining production efficiencies. In practice, different operational definitions are in use. This paper describes a series of simulation experiments to identify the management implications of two common strategies (activity-based versus start-based). A special-purpose simulation template was built for the Simphony environment for this purpose. The pace chosen for the flow of activities was found to significantly affect the speed at which the subdivision was completed. The even flow strategy was found to affect the subdivision completion time only slightly, but to have a significant impact on workflow variability and management effort. Control of the pace of starts of only the first activity exhibited nearly the same degree of variability as if the pace of starts were matched to a sales pace.     

Drivers for Cost Estimating in Early Design: Case Study of Residential Construction

This paper proposes the use of a series of independent variables for an early estimation of the building construction cost of residential buildings. Based on 70 German residential properties, these variables serve as the cost drivers of a project, and the regression model, tested against the 70 properties, has a mean absolute percentage error of 9.6%. When applied to predict the cost of five more properties that were excluded from the 70 in the regression model, the percentage error ranges between–12 and 13%. The identified cost drivers are: compactness of the building, number of elevators, size of the project, expected duration of construction, proportion of openings in external walls, and region.     

Fuzzy Numbers in Cost Range Estimating

Range estimating is a simple form of simulating a project estimate by breaking the project into work packages and approximating the variables in each package using statistical distributions. This paper explores an alternate approach to range estimating that is grounded in fuzzy set theory. The approach addresses two shortcomings of Monte Carlo simulation. The first is related to the analytical difficulty associated with fitting statistical distributions to subjective data, and the second relates to the required number of simulation runs to establish a meaningful estimate of a given parameter at the end of the simulation. For applications in cost estimating, the paper demonstrates that comparable results to Monte Carlo simulation can be achieved using the fuzzy set theory approach. It presents a methodology for extracting fuzzy numbers from experts and processing the information in fuzzy range estimating analysis. It is of relevance to industry and practitioners as it provides an approach to range estimating that more closely resembles the way in which experts express themselves, making it practically easy to apply an approach.