CHAPTER 1 INTRODUCTION

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1 1 CHAPTER 1 INTRODUCTION 1.1 GENERAL Planning and Scheduling of construction projects has always been a significant factor determining the successful completion of a project due to competition, time, space and resource constraints, penalties and incentives that are predominant in this sector. A well-planned and meticulously scheduled project invariably becomes a successful project and contributes directly or indirectly to the development of any nation. Planning and scheduling of construction projects are being carried out with bar charts, milestone charts and network techniques and software packages based on these techniques. The use of scheduling tools helps the project manager to determine the slack times available between activities and critical paths for decision making during the course of the project. Based on this information, the scheduler (project manager) further manipulates and reschedules the activities in a project so as to complete the project optimally. The most important criteria in predicting the completion or duration of a project is by defining the probable production rates of activities involved in order to provide resources appropriately to these activities. The allocation of duration for each activity is based on the production rate of a crew that is employed to carry out the activity keeping in mind the total project time. Standard data books for analysis of rates of activities in construction projects provides us with guidelines which can be used to determine production rates for various activities of a project.

2 2 1.2 LINEAR PROJECTS Construction projects consist of activities which have a discrete or continuous relationship between them. In other words the start or progress of an activity depends on the completion of a previous activity in discrete systems whereas progress of activities is simultaneous in continuous systems. The progress of both the discrete and continuous activities has no bearing on the location of the activity as far as the linearity of the project is confined to small distances. Linearity may either be vertical or horizontal. Typical examples of vertical linearity are high rise constructions like towers and skyscrapers and horizontal linearity are projects like roads, rails, pipelines etc. Recent literature review on scheduling has indicated that by using conventional techniques the critical paths, floats of activities can be determined by network based techniques only for projects with discrete activities, which is typical of activities in building construction projects without vertical and horizontal linearity. But for activities with spatial and continuous relationships as in activities of road projects and high rise constructions such techniques fail to give the required information to the project manager (Johnston 1981). From the review of the schedule prepared by some leading road constructors, it has been observed that the usual order of activities in road construction are diversion, clearing, earthwork, embankment, sub base, sub grade, macadam, asphalting, kerbs and culverts. From this list of activities it is seen that road projects have a combination of discrete and linear activities. Discrete activities such as culverts, underpasses are similar to activities as in a building project and occur only at distinct locations on a road. Linear activities form the bulk of the activity types in road projects such as clearing, earthwork, base course, macadam, asphalt etc which occur along the entire stretch of the road project and succeeding activities progress while the preceding activities are still on going. Moreover,

3 3 road projects are executed in various sections depending on the availability of working space and resources with the same crew or with different crews for each of these sections. If the sections are comparatively long, then there is a possibility of crew allocations for the succeeding activities while the preceding activities are still in progress. Also, road projects are characterized with repetitive activities spanning the section lengths at various locations of the project. These types of projects are classified as linear projects and scheduling them with conventional methods shall not provide us with accurate results. The limitations of network techniques in bringing out the required information about linear activities has been studied by Harmelink and Rowings (1998) and hence there is a need to critically evaluate the current techniques used by constructors in road sector. The standard data book for analysis of rates for roads and bridges published by the Indian Roads Congress (IRC) provides us with guidelines which can be used as base information in defining production rates for various activities of a road project. A simple and efficient scheduling methodology seems to be the need of the hour as road sector is poised for a major development in a country like India. Table 1.1 Indian Road Network Category Expressways 200 Length (km) National Highways State Highways Major District Roads Rural and Other Roads Total Length

4 4 According to the data indicated by National Highway Authority of India (NHAI) in June 2013, national highways constitute about 1.7% of the road network but carry about 40% of the total traffic. About 65% of freight and 80% of passenger traffic is carried by the road sector. Number of vehicles has been growing at an average rate of 10.16% per annum over the last 5 years. Table 1.1 shows the details of road network in the country ( 1.3 SECTIONS OF A ROAD Road structure cross section normally composes of the following layers and can be represented in a simple form as in Figure 1.1. The thickness of these layers, pavement composition and other specifications such as materials etc are provided as per standard codes of practice. 1) Subgrade layer 2) Subbase layer 3) Base course 4) Surface course/wearing course Although a pavement s wearing course is most prominent, it is the subgrade which decides the life of the pavement. The subgrade can be composed of a wide range of materials and its performance in a great way depends on its load bearing capacity, moisture content and shrinkage or swelling characteristics. Capping layers are provided only on weak subgrades so to improve their strength. It is usually a granular type of material laid to provide a working platform on which the subbase layers can be constructed.

5 5 The subbase is a layer of granular material provided above the subgrade generally with natural gravel. It should be clean and free from organic matter and should be able to be compacted by a roller. The material should conform to stipulated standards. It enables traffic stresses to be reduced to acceptable levels in the subgrade. It acts as a drainage layer between subgrade and road base and also intercepts upward movement of water by capillary action. The road base and base course are layers immediately below the wearing course which are subjected to severe loading conditions. They are constructed with superior quality materials as per codal recommendations. Wearing course Base course Road base Subbase Capping Subgrade Figure 1.1 Typical Sections of a Road The surface course or the wearing course forms top layers of the pavement which is in direct contact with the wheel load of the vehicle. The top layers are normally constructed with bituminous pavements conforming to standards. 1.4 CURRENT SCHEDULING TRENDS In the subcontinent, it has been noted that the Gantt chart output using the MS Project software is the most widely adopted method for road project scheduling, which has wide range of facilities and functions. The start to start relationships, finish to start relationships of the activities in a road

6 6 project are well depicted in the MS project outputs. These outputs are shown as bars horizontally against the duration and therefore the progress of work can be interpreted as percentage of the total quantity of work that needs to be completed. But, this chart fails to depict the actual location at which any activity is at any point of time and also cannot accurately show the exact critical path and floats due to the nature of relation ships of the linear activities which cannot be indicated with a network. Linear scheduling enables to locate even the discrete events like culverts, bridges etc with their chainages. The CPM has been widely used around the world as a premier scheduling tool in project management due to its analytical capabilities and compatibility to resource utilization, crashing and time cost trade offs. All these have been possible due to the logical representation of activities through networks as per their actual relationships in a project which provides the following detailed information. (Vohra 2001) i) Determination of start to start and start to end timings between activities ii) Determination of earliest start times, completion times, latest start times and completion times of activities. iii) Critical paths of the activities and its floats as a result of the above information. Due to this information, crashing, resource planning and time cost trade off have all become possible with the CPM. But, it was found later that the CPM could not be applied to projects, which consist of activities whose actual relationship during execution fail to be represented by a network. Road works fall under such category of projects and their scheduling approach needs a critical study in the present scenario.

7 7 1.5 PRODUCTION RATE APPROACH Scheduling of construction projects has never been simple due to the uncertainties prevailing in the construction industry. The reasons for these uncertainties may be global or local, universal or centered, all of which challenges the outcome of a construction project. Also, road constructions or highway construction is a major segment in the construction industry, which is unique in its characteristics due to nature of relationships of its activities among each other, its influence on traffic, services and the environment and the materials used for its construction. All these aspects comprise of numerous parameters with varying degrees of complexity. Scheduling a project under these circumstances in turn depends on this complexity and variation in the parameters. The reasons involved may broadly be classified into predictable and unpredictable based on its nature. One respite while dealing with highway projects is that it can be broadly divided into 7 characteristic activities viz, site clearing, marking and leveling, sub grade, sub base course, road base course, base course and wearing course. Even though the number of activities in highway projects may be limited, a large amount of uncertainty is prevalent in execution which makes its project scheduling cumbersome. In other words there is a variation of production rates of activities in projects based on numerous factors. Reaching a consensus on probable production rates of activities in such situations can be a better option to obtain a more valid and realistic schedule. 1.6 DEFINITIONS Construction project scheduling deals with progress of activities in a project and accomplishments of milestones with respect to targets and tools that are associated in this process. Road project scheduling has its own peculiarity as progress of activities is along the length, breadth and depth of the road. Several terms connected with this research have been explained in

8 8 the respective sections of this thesis based on literature study. Progress rates and production are two important measures of road project development and these terms have been extensively used in this work. Progress Rates Progress rates in the simplest form may be defined as development based on time. Although such a meaning has relevance in road project scheduling, progress rates adopted in this work refers to the distance covered per unit time. Due to site practices, distances have been specified in kilometers (km) and time in days. Thus progress rates have been indicated in km/day. Progress rates have been used in chapter 4 of this work to explain the concept and applications of LSM. Planned rates, least rates and float rates are terms that have been used in association with progress rates. Linear Production Rate Production in road project may refer to accomplishment of work with respect to time. Linear production rate adopted in this work refers to the time consumed for completion of unit distance of the road. Days/km has been used as the unit in expressing linear production rate. Linear production rate in this work has been calculated based on the total time spent for completing a certain length of the road. This term has been used to indicate the timedistance relationship for a particular section of the road project in chapter 5 and in the development of an algorithm. Productivity Productivity is an economic measure of output per unit of input. Inputs include labour and capital, while output is typically measured in revenues. Productivity measures may be examined collectively or viewed

9 9 industry by industry to examine trends in labor growth, wage levels and technological improvement. Productivity in road construction refers to the output work based on a crew assignment. This term has been used to indicate the constructor s plans with an objective to produce desired results in chapter 7. Production Rate In manufacturing production rate means the number of goods that can be produced during a given period of time. Alternatively, it means the amount of time it takes to produce one unit of a good. In construction, it refers to the rate at which workers are expected to complete a certain segment, such as a road or building. The production rate will depend on the resources, choice of technology and various other factors considered. Production rate in this work has been used to determine the quantity of work accomplished based on time and constitutes the core focus behind this research. Production rate is based on productivity calculations which means it caters to the output arrived out of an input of resources. This term has been widely used in this work and mostly significant to chapter 7 of the thesis. Unless production rates are used to define the quantity of work dimensionally without ambiguity, its reference in this work is to be considered as linear production. 1.7 NEED FOR THE STUDY From the review on scheduling methods currently used in the construction industry, it is clearly understood that the compatibility of the scheduling tool is purely based on the type of project, its component tasks and their production rates and nature of relationship between them. Therefore it becomes mandatory for project scheduling to depict the reality of the construction process in a project. The linear scheduling method (LSM) has

10 10 been cited on several occasions as a promising tool for use in scheduling road and similar linear projects. The efficiency of linear scheduling to handle production rates of activities and incorporate uncertainty prevailing in project execution needs to be investigated comprehensively and a more sort after scheduling approach is to be developed for linear construction. Moreover in a country like India, where infrastructure growth is constantly under stress due to higher gross domestic product ( GDP) targets set every year, only constructors equipped with state of the art technology shall be able to deliver the project facilities on time. India s transport sector is large and diverse; it caters to the needs of nearly 1.2 billion people. In 2007, the sector contributed about 5.5 percent to the nation s GDP with road transportation contributing a lion s share. A recent study has stated 18,637 km of expressways needs to be built by the end of the 13th five-year plan period by the year Infrastructure development (for expressway projects alone), on such a massive scale would require about INR 4500 billion (USD billion) according to the study. The budget for the year has recorded an outlay of INR 373 billion (USD 6.29 billion) for the road sector. Therefore considering these factors, an attempt has been made to enhance the scheduling approach adopted in road projects. 1.8 STUDY AREA OF THE WORK The four laning of the recently completed road from Krishnagiri (km 94.00) to Thopurghat (km ) in the southern state of Tamilnadu, India has mainly been taken for study in this work. The project was executed by one of the major constructors in India who won several awards for this project. The project was completed in thirty months starting July 2006 and ending January The major scope of works consists of widening of existing carriageway, construction of new carriageways, bypasses, service roads,

11 Figure 1.2 Project Site Map 11

12 12 ramps, cross drainage structures and bridges. The total length of the project is 62.50km ( km to km ) with strengthening of Thopurghat section for a length of 7.4km ( km to km ) and 156 numbers of cross drainage structures and bridge works. The alignment of the new road has been made in such a way by introducing four major bypasses that avoids major settlement and rehabilitation issues along the length of the project. Introduction of RE walls at pivot points of the project helped in avoiding major land acquisition constraints. All the villages in the locality are well connected by service roads and underpasses to access the main highway. The average delay due to land acquisition and shifting of utility services was reported as 8 months. Hence the effective construction period has been 22 months. Data such as layer wise status of the project, section wise details of completion of work, summary of work completed with respect to the estimated quantity of work and the final MS project schedule as per actual durations followed have been collected from the site. The location map with important towns, chainages and bypasses in the project have been shown in Figure 1.2.The details of the schedule with mileages followed in the project have been shown in Appendix 2. Data from similar type of projects have been acquired for arriving at an appropriate method of scheduling based on probable production rates of activities in linear construction for individual stretches and a highway project on a whole. Thus, scheduling in construction projects depends on the type of project, its component activities, exposure conditions, tools currently developed and contribution of the project to the growth of a nation. With the current trends of infrastructure development and growth plans in the Indian subcontinent, in particular the road sector, an attempt has been made to evolve a simple methodology to satisfy this requirement.