Construction Management - pdf - c18.pdf - po ang - Januszek66

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Chapter 18

Construction Operations

PROSIDYC: Simulation Program for Construction Operations

The Need

Currently 3D-modelling is the trend in the simulation area. However,

developing 3D models of construction operations is very complex and time

consuming. In general, the study of construction operations requires a tool

that provides solutions without requiring the input of copious amounts of

data. In order for a construction company to use a simulation tool, the

methodology has to be presented in a very simple and graphical context.

Pictorial and schematic tools are easily accepted. In contrast, if the

methodology appears to be too theoretical or analytical it will be avoided

by construction practitioners.

Construction of ﬂoating caissons utilized

PROSIDYC as a tool to increase

production.

The Technology

PROSIDYC is a system for simulating construction operations jointly developed by the

Planning and Methods Unit of Dragados y Construcciones, Madrid, Spain and the

Division of Construction Engineering & Management at Purdue University.

PROject SImulation Dragados Y Construcciones (PROSIDYC) is a computer based

system for analyzing construction job site production processes. It is used to improve

productivity in the ﬁeld by studying resource utilization and cycle times and identifying

opportunities for production improvement. PROSIDYC uses the CYCLic Operations

NEtwork (CYCLONE) modeling format. A set of graphical modeling elements are

utilized to develop a network model of the process of interest. The model identiﬁes

waiting or delay states as well as active productive states. The computer program allows

the modeler to identify resources which are underutilized and bottlenecks in the process.

The use of this approach has achieved 100% success in productivity improvement on

the processes studied. Improvements range from 30% to 200%. Data support the fact that

Harbor site layout.

Caisson Construction Valencia, Spain.

PROSIDYC/CYCLONE

Flow diagram.

18-1

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Chapter 18

Construction Operations

for every hour of analyst time used, a saving of $2,000 is realized. Therefore, for 100

hours of engineering-time invested, a saving of $200,000 is achieved. PROSIDYC was

used to achieve major cost savings in the massive breakwater in Valencia shown here.

18.1

MODELING CONSTRUCTION OPERATIONS

In Chapter 1, the hierarchy of construction management was described as shown in Figure

18.1. Activities deﬁne the structure of projects. The basic building block required to un-

derstand and analyze construction operations is the work task. A meaningful description

of a construction operation requires the deﬁnition of the basic work tasks and the manner

in which the available resources (e.g., cranes, crews, materials, etc.) perform or process

through the work tasks. In this sense individual resources can be said to traverse or ﬂow

through work tasks. The sequential and logical relationships between the various work tasks

deﬁne the technology being used. The actual working of the operation can then be described

by locating and monitoring, from time to time, the various resource entities as they dynam-

ically traverse the static structure of the operation. A simple graphical modeling system

can be used to analyze the work ﬂow and develop the productivity for a given construction

operation.

18.2

BASIC MODELING ELEMENTS

A modeling format for ﬂow modeling construction operations can be developed using four

graphical symbols:

Figure 18.1 Hierarchical levels in construction management.

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18.3

Building Process Models

Modeling Element

Name of Element

Description of Modeling Element

The normal work task modeling element can

commence as soon as a unit (e.g. resource)

arrives from a preceding element; it is

unconstrained.

NORMAL

The constrained work task modeling element

requires multiple resources (e.g. cranes,

crews) before it can begin. A combination of

resources is required to start. Otherwise similar

to the normal work task modeling element.

COMBI

The idle state of a resource entity symbolically

represents a waiting location (i.e. a queue)

where resources wait prior to being combined.

QUEUE

The directional flow modeling element shows

the logical flow of resources.

ARROW

Figure 18.2 Basic modeling elements.

1. Active-state square node representing a work task

2. Idle-state circle representing a delay or waiting position for a resource entity

3. Directional ﬂow arrow representing the path of a resource entity as it moves between

idle and active states

The symbols used (see Fig. 18.2) for each modeling element are designed to be simple

and helpful in developing schematic representations of the construction operation being

modeled. Two basic shapes (squares and circles) are used to model active and waiting re-

source states; together with directed arrows (arcs) for resource ﬂow direction, they help to

provide a quick visual grasp of the structure of a construction operation. These symbols

are the basic modeling elements of the CYCLONE (CYCLic Operations Network) mod-

eling system. They are used to build networks of active and idle states to represent cyclic

construction processes.

It is convenient to distinguish between the unconstrained (i.e., normal) work task and

the constrained (i.e., requiring the initial satisfaction of conditions) work task. While all

work tasks are modeled schematically as square nodes, the constrained work task is modeled

as a square node with a corner slash. Thus a total of four symbols is required for the modeling

of the structure and resource entity ﬂow of construction operations (see Fig. 18.2).

The active working-state models are the NORMAL and COMBI modeling elements.

Both have a square-node format and model work tasks. Since the work task is the basic

component of a construction operation, it should be chosen so that its name or description

is sufﬁcient to convey to a crew member or supervisor the nature, technology, work content,

and resources needed to fulﬁll the work task.

Simple examples of work task activities are breaking open brick pallets, preparing

column formwork, and loading trucks with front-end loaders. The deﬁnition of a work task

thus requires a verbal description, an indication of the resource entities involved, and a

deﬁnition of the time required (duration) to complete the task.

18.3

BUILDING PROCESS MODELS

The relative sequence and logic of the work tasks and processes that make up a construction

operation constitute the technological structure of the operation. The modeling elements

can be used in a variety of patterns to model construction operations.

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Chapter 18

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Figure 18.3 Schematic outline of earth-moving operation.

As an example, consider the development of a model for an earth-moving operation

that involves the loading of trucks with earth for transport to a dump area. A pictorial

representation of the operation is shown in Figure 18.3; it uses a front-end loader, some

trucks, and earth.

In order to develop the framework of the earth-moving operation, it is necessary to

identify the major resources involved (i.e., trucks, front-end loader, and soil) and establish

the various states (i.e., both the active working states and the passive waiting states) that

the resources traverse in their work assignment paths and cycles. Finally, the integration of

the resource paths and cycles establishes the basic structure of the operation.

Each truck, for example, is idle while it waits (i.e., queues) for loading; it enters active

working states when it is being loaded, dumping, traveling loaded to the work site, and

returning empty for another load. A simple model of this work cycle is shown in Figure

18.4a using a single COMBI “Load truck” work task that requires earth and a front-end

loader for initiation; three NORMAL work task elements, “Loaded truck travel,” “Truck

dump activity,” and “Empty truck return”; a single QUEUE element, “Join truck queue”;

and ﬁve arrows indicating the logical relationships between the various truck states.

18.4

STRUCTURE OF CONSTRUCTION OPERATIONS

The front-end loader can be initially modeled by a unit cycle involving the active-state

COMBI element “FEL (front-end loader) loading,” the idle QUEUE element “FEL idle,”

and two entity ﬂow directional logic arrows (see Fig. 18.4b).

In Figure 18.4c, a soil path model is shown that uses a source QUEUE node “soil

stockpile” and a sink destination soil dump QUEUE node together with a COMBI work

task “Loaded into truck” and NORMAL work tasks “Transport by truck” and “Dumped”

to portray the soil involvement in active work states. Finally, four directional arrows are

required to develop the path structure.

The integrated model incorporating the truck and front-end loader cycles together

with the soil path from stockpile to dump is shown in Figure 18.4d. Model integration is

achieved by combining or “overlaying” active states which are common to two or more

resource cycles. For instance, “load truck” in the truck cycle is the same active state (work

task) as “loaded into truck” in the soil cycle and “FEL Loading” in the loader cycle. These

three states are combined in the integrated model to be one active state “LOAD.”

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18.5

Modeling Procedure

Figure 18.4 Development of operational structure; (a) truck cycle, (b) loader cycle, and

This model can be used as the basis for further development involving dump area

spotters and queues, dozer stockpiling operations, and truck maintenance, as well as the

basis for further detail such as a more precise description of the front-end loader loading

cycle. An extension of the skeletal structure of the earth-moving operation to include dozer

stockpiling and spreading operations together with a dump spotter foreman is shown in

Figure 18.5. A counter element (represented by a ﬂag) has been added to note the point in

the network at which production will be measured.

The foregoing presentation illustrates that the structure of construction operations can

be developed and illustrated through the proper use and labeling of the basic modeling

elements. The model structure can be used in explaining the construction technology and

construction method of the construction operation to ﬁeld personnel and managers.

18.5

MODELING PROCEDURE

The procedure for modeling a given construction process involves four basic steps. The

steps, as shown in Figure 18.6, are as follows:

1. Flow Unit Identiﬁcation .Asaﬁrst step, the modeler must identify the system

resource ﬂow units (e.g., resources such as earth, cranes, crews, etc.) that are

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