Critical path effect based delay analysis method for construction projects

Assessing schedule delay's impact on total project duration to distribute delay liability remains a controversy. None of existing delay analysis methods is perfect because including an element of assumptions, subjective assessment and theoretical projection. Windows-based delay analysis methods are excellent in identifying and measuring construction schedule delays. Based on a previous study identifying potential problems in available windows-based delay analysis methods, this study proposes an innovative windows-based delay analysis method, called the effect-based delay analysis method (the EDAM method). The EDAM method performs delay analysis using extracted windows and determines delay impacts by considering the effects of delays on the critical path(s). According to its application to hypothetical cases and comparisons with other methods, the EDAM method is efficient in delay analysis and effective in solving concurrent delays and determining schedule shortened. The proposed EDAM method is a good alternative for schedule delay analysis for construction projects.     

Material and equipment procurement delays in highway projects in Nepal

Delay in the delivery of materials and equipment to construction sites is often thought of as a contributory cause of cost overruns in construction projects in developing countries. A cursory examination of the environment in which projects are executed in developing countries appears to support this thinking. However, there does not seem to have been much research work conducted that investigates whether this is actually the case and also assesses the causes of these delays and magnitude of their impacts on project costs. This research was aimed at firstly ascertaining the occurrence of material and equipment procurement delays in highway projects in Nepal. An assessment of the causes of the delays and the magnitude of their impact on project costs was also made. The survey method was used in conducting this research involving 22 highway projects. The main causes of material and equipment procurement delay were found to be (in rank order) organizational weaknesses, suppliers' defaults, governmental regulations and transportation delays. However, the actual impact of these delays on project costs was found to be on average, only about 0.5% of the total budgeted cost of the projects. Among materials, delays in the supply of aggregates were found to occur most frequently while delays associated with pavers occurred most frequently among equipment.     

Fire services installation related contributors of construction delays

Delay is a common problem in the construction industry and there are several reasons that can contribute to delaying a project. In Hong Kong, completion of fire services installation is prerequisite to completing/finishing a building construction work. The fire services installation must be completed for application of an occupation permit for a building. Fail to obtain the permit on time would lead to construction delay. Apparently, fire services contractors play an important role in obtaining the occupation permit for a project completion. The economic losses due to construction delay could be very significant. This research identified, from a list of 49 pre-determined factors in nine categories (shown in Appendix A), the principal factors contributed to construction delays in a fire services installation. In particular, a questionnaire survey of 52 fire services contractors and 32 consulting engineers was conducted in order to obtain their professional judgements about the relative importance of the contributors of construction delay related to the fire services installation. The result showed that the principal contributors were: (1) improper site co-ordination and management of the electrical and mechanical installations, (2) lack of timely decision making of the client, and (3) defects identified during the fire services inspection by local authorities. In addition differing views were found between the consulting engineers and contractors on the areas identified were: (1) site management and supervision, (2) workload of the project staff, (3) the procedures for equipment approval, and (4) working experience of the parties. A monitoring and quality assurance system would be required in these areas to minimize the risk of the probable construction delay.     

Resource constrained project scheduling using simulation

Resource allocation is one of the most important issues of construction management. Two problems of resource allocation are of concern: resource levelling and resource scheduling. Traditionally, the resource scheduling problem is solved using either heuristic methods or optimization techniques. When heuristic methods are used, resource scheduling is treated as a subsequent problem for the CPM analysis. In this paper, the resource scheduling problem is handled using simulation, where logic dependence and resource availability limits are considered simultaneously during the time scheduling process. Simulation is applied to the resource scheduling problem at the project level. A simulation system called SIRBUS is used to schedule construction projects under resource constraints. Constant resource demand of activities is assumed, and the activity once started cannot be interrupted. Six example projects previously solved by different heuristic methods are re-solved using simulation. The results are compared with the latest heuristic models: current float technique and ranked positional weight method. In addition to the advantage that resource availability is considered during time scheduling as a starting point, which is an apparent feature of simulation, SIRBUS gives good results compared with existing heuristic methods.     

The effects of construction delays on project delivery in Nigerian construction industry

Construction delay has become endemic in Nigeria. It is imperative to create awareness of the extent to which delays can adversely affect project delivery. This paper identifies, by questionnaire evaluates and through empirical method assesses the effects of construction delays. The findings showed that time and cost overruns were frequent effects of delay. Delay had significant effect on completion cost and time of 61 building projects studied. Client-related delay is significant in Nigeria. Acceleration of site activities coupled with improved clients' project management procedure and inclusion of appropriate contingency allowance in precontract estimate should assuage the adverse effect of construction delays.     

Incorporating rework into construction schedule analysis

Rework has been a primary cause of cost and schedule overruns in large construction projects. While several research efforts have analyzed the causes and effects of rework and provided guidelines to reduce rework, almost no research exists to analyze the impact of rework timing and quantity on schedule delays and to support decisions on cost effective recovery. This research presents a quantitative mechanism for schedule analysis considering rework. The mechanism has three aspects: (1) a new schedule representation of rework magnitude as negative percentage complete for affected activities, documented on the specific date on which the rework is detected; (2) a modified daily-windows delay analysis to apportion project delays among the responsible parties; and (3) an optimization technique for determining the least costly corrective action strategy that recovers project delays. The proposed approach is applied to a case study to demonstrate its ability to consider rework impact, in combination with other progress events by other project parties. This research offers an innovative quantitative approach to consider rework timing and amount in delay analysis and corrective action optimization.     

A framework for Virtual Interactive Construction Education (VICE)

Training and process analysis in the construction industry has not taken full advantage of new technologies in simulation, modeling, and semantic web and software engineering. The purpose of this research is to develop a framework for a virtual interactive construction education system taking full advantage of these technologies. The modules will simulate the construction process for a facility from start to finish using information drawn from domain experts using real projects in the built environment. These modules can be used as training tools for new employees where they attempt to optimize time and cost in a virtual environment given a limited number of equipment, time and employee options. They can also be used as a process analysis tool before, during and after construction where a number of situational variables could be analyzed for exposure of potential risk. These modules would be particularly useful for repetitive construction where the initial project or task is analyzed for optimization and risk mitigation. This paper describes the framework using a residential construction example that is a 900 square foot (about 85 m²) wood frame single family house designed for the United States.     

多事件交叉干扰下的工期索赔方法

在工程施工过程中,工期延误是很常见的,产生的原因也非常复杂,因此工期延误的责任归属和责任定量化对于索赔非常重要。针对多事件交叉干扰下工期延误引起的工期索赔责任归属难以判断和责任比例难以测量的问题,通过分析初始事件原则、不利于承包商原则和责任分摊原则的索赔处理机制以及网络计划的计算方法,提出一种程序化计算方法,即通过设置一系列易于嵌入计算机程序的变量,无需进行关键路线的分析,即可对各工序对于工期延误造成的影响进行较为精确的分析和排序。     

A fuzzy logic approach to model delays in construction projects using rotational fuzzy fault tree models

Delays in construction projects are inevitable and, as a result, claims and disputes arise. Different causes of delay can come into play and therefore the need to identify and classify different causes of project delay arises. Different factors that contribute to project delay affect the likelihood of project delay in different degree of effectiveness. Fuzzy fault tree analysis (FTA) is suggested by this research to estimate the likelihood of project delay. Likelihood of delay membership function is further quantified using the weighted average defuzzification method. Two fuzzy logic models are implemented into the fuzzy FTA, using Visual Basic software: the models discussed in this research are Baldwin's rotational model and the Angular model. Comparison between the two fuzzy logic models has been carried out. Validation of the fuzzy FTA computer model is performed. Validation of the model was performed for adequacy and applicability of the model. On average, the validation performed by independent construction engineers and fuzzy logic experts produced satisfactory results. The computer software suggested by this study is an attempt to assess the likelihood of the project delay, which helps reduce delays in construction projects that can cause time loss.     

An evaluation of the accuracy of the multiple regression approach in forecasting sectoral construction demand in Singapore

In the current state of research in construction demand modelling and forecasting there is a predominant use of the multiple regression approach, particularly the linear technique. Because of the popularity, it may be useful at this stage to gain an insight into the accuracy of the approach by comparing the forecasting performance of different forms of regression analysis. It is only through such formal means that the relative accuracy of different regression techniques can be assessed. In a case-study of modelling Singapore's residential, industrial and commercial construction demand, both linear and nonlinear regression techniques are applied. The techniques used include multiple linear regression (MLR), multiple log-linear regression (MLGR) and autoregressive nonlinear regression (ANLR). Quarterly time-series data over the period 1975–1994 are used. The objective is to evaluate the reliability of these techniques in modelling sectoral demand based on ex-post forecasting accuracy. Relative measures of forecasting accuracy dealing with percentage errors are used. It is found that the MLGR outperforms the other two methods in two of the three sectors examined by achieving the lowest mean absolute percentage error. The general conclusion is that nonlinear techniques are more accurate in representing the complex relationship between demand for construction and its various associated indicators. In addition to improved accuracy, the use of nonlinear forms also expands the scope of regression analysis.     

Object-Oriented Model for Freeway Work Zone Capacity and Queue Delay Estimation

Abstract:   Existing computer models used to estimate queue delay upstream of the work zone have a number of shortcomings. They do not provide any model to estimate work zone capacity, which has a significant impact on the congestion and traffic queue delays. They cannot be used to perform scenario analysis for work zones with various characteristics such as work zone layout, number of closed lanes, work intensity, and work time. In this article, an object-oriented (OO) model is presented for freeway work zone capacity and queue delay and length estimation. The model is implemented into an interactive software system, called IntelliZone, using Microsoft Foundation Classes (MFC) and a hierarchy of multiple specialized frameworks. A three-layer application architecture is created to separate the application functions and classes from MFC classes. The high-level application domain layer is divided into packages. IntelliZone's capacity estimation engine is based on pattern recognition and neural network models incorporating a large number of factors impacting the work zone capacity. This research provides the foundation for a new generation of advanced decision support systems for effective management of traffic at work zones .     

乌龙江大桥复合材料防船撞系统的设计与施工

本文围绕乌龙江大桥,探讨了新型自浮式复合材料防撞系统的设计理念和施工工艺。自浮式复合材料防撞结构具有整体吸能效果好,耐腐蚀、造价低廉、适合水位变化上下浮动的优点,克服了传统钢套箱防撞设施的局限性。该防撞保护设施后期维护工作量小,在遭受船舶撞击后,便于局部维修与节段更换。节段预制拼装工艺避免了传统防撞的设施安装的诸多问题且大大缩短了施工工期,取得了显著的经济与社会效益。     

Anwendung verschiedener Injektionstechniken als Sicherungsmaßnahmen im Zuge der Baumaßnahme Nord‐Süd‐Stadtbahn Köln,Los Nord

Application of different grouting techniques as safety measures for the construction works of Cologne's North‐South Urban Light Railway. Construction the northern section of Cologne's North‐South Urban Light Railway difficult geological conditions existed. Therefore it was necessary to conduct different safety measures for the adjacent buildings and the tunnelling with grouting techniques during the construction. The so called Keller Soilfrac® technique and the jet grouting technique Soilfrac® were applied. Soilfrac® technique was basically initiated from working pits to stabilize and strengthen the soil layers around the tunnel to be excavated. The jet grouting technique was used under extremely cramped working conditions for the underpinning of buildings and the construction of blocks as starting blocks for the tunnel shield method. The grouting techniques were used for various construction jobs. Below seven different jobs are described.     

谨慎的积极:议农村住屋建造体系及其技术选择

农村整治与规划是新农村建设的重要内容之一,住屋建造则是农村整治与规划建设的主要内容和关键技术。深入论述了农村住屋建造面临的普遍问题、研究的意义和现状,认为农村住屋建造研究是建筑从业者十分值得研究的课题,也是其他学科难以介入的领域;提出农村住屋建造体系研究的5个具体方向,认为必须十分谨慎地使用现代技术,因地制宜地应用各种适宜的建造方式和技术,避免农村规划与建设中出现的粗糙简单,减少"大建设中大破坏"的现象。     

掌控曲面表皮建造中的平面拟合

本文以曲面表皮建造中建筑师在设计、建造过程的失控问题为着眼点,通过分析现有技术的特点,认识到失控源自于建筑师难以同时处理曲面的平面拟合与特定材料的施工工艺,进而提出开发基于目标材料系统的曲面表皮模拟建造软件的一般方法,并以德国莱茵辛克矩形内扣板系统为例,展示模拟软件Auto Zink带来的曲面表皮互动设计过程。     

The nature and effects of construction delays

A method for assessing delay claims, regularly used in the USA, is described, together with procedures which have been proposed for dealing with concurrent delays. These treatments are reviewed to identify their shortcomings which in some instances stem from a view of the nature of delays which is not consistent with the way in which delays actually occur. The various types of delay are examined to consider how these treatments might be amended to provide more realistic solutions. It is suggested that concurrent delays need only be separately considered when they affect a single activity, and the concept of parallel critical paths in an as-built network is thought to be invalid. The delays themselves are not always fixed in when they might have their effects and it is felt to be important that this be recognized. Finally a procedure is suggested to select days of exceptional adverse weather artificially, so that critical path method (CPM) analyses may be carried out.     

Analysing factors affecting delays in Indian construction projects

Construction projects in India are experiencing widespread delays. Due to a dramatic shift in the capacity and volume of the Indian construction sector over the last decade, the need of a systematic analysis of the reasons of delays and developing a clear understanding among the industry professionals are highly crucial. Using a selected set of 45 attributes, this research first identified the key factors impacting delay in Indian construction industry and then established the relationship between the critical attributes for developing prediction models for assessing the impacts of these factors on delay. A questionnaire and personal interviews have formed the basis of this research. Factor analysis and regression modelling were used to examine the significance of the delay factors. From the factor analysis, most critical factors of construction delay were identified as (1) lack of commitment; (2) inefficient site management; (3) poor site coordination; (4) improper planning; (5) lack of clarity in project scope; (6) lack of communication; and (7) substandard contract. Regression model indicates slow decision from owner, poor labour productivity, architects' reluctance for change and rework due to mistakes in construction are the reasons that affect the overall delay of the project significantly. These findings are expected to be significant contributions to Indian construction industry in controlling the time overruns in construction contracts.     

Classification of production systems for industrialized building: a production strategy perspective

The purpose is to develop a matrix for classifying production systems for construction with various degrees of industrialization. Previous attempts to classify industrialized production systems for construction focus on dimensions such as the design process, the product technology, or the supply chain structure, but none of them acknowledge the importance of how orders are actually won in the market and that different market segments have different requirements. Using production strategy theory as a base, a matrix is developed linking market requirements, via the product offering, to the design of the production system. The matrix positions typical production systems based on their respective degrees of product standardization and volumes relative to the degree of offsite production. Similar to production systems in manufacturing, production systems for construction also deliver manufacturing outputs at different levels, indicating that the choice of production system will affect the competitiveness of the company. The applicability of the matrix is exemplified through three case illustrations of concepts for industrialized building, and these show that the matrix can be used to analyse the production systems’ relative strengths and weaknesses. The matrix can also be used as a guide when developing new, or adjusting existing, production systems for industrialized building so that they will match market requirements and offer competitiveness.     

A Multimedia Construction Delay Management System

The need for acquiring, storing, processing, and presenting quality data in a timely manner in support of construction project management is well recognized. Therefore, a properly developed information system that manages the required data is crucial to the success of project management. However, one type of useful data and information, namely, multimedia (pictures, videos, and audio), has not been appropriately acquired and/or managed in construction. Researchers are just beginning to explore and evaluate the benefits of multimedia information in construction applications. This paper discusses some of the potential applications of multimedia in construction and describes the implementation of a prototype multimedia information system for construction delay management. The system tracks a variety of data types related to delays, including pictures, videos, and audio.