1. 6. CONSTRUCTION SIMULATION
Objective:
To understand the principles of computer-based construction simulation, and to develop expertise in applying the CYCLONE simulation method to construction planning:
Summary:
6.1 Introduction
6.2 The CYCLONE Method
6.3 Application to Simple Earthmoving Systems
6.4 Stochastic vs Deterministic Simulation

2. 6.1 INTRODUCTION Fig. 6-1:Simulation as a Dynamic Modeling Technique
Simulation is a dynamic modeling tool:
it mimics the processes on site as a sequence of snapshots (called system states);
this makes it very versatile (can in principle take any factor into account);
you cannot miss out states (the only way to find the end state is to go through all intermediate states);
each state is computed from the previous state using a 3-phase algorithm.
State 1
State 2
3 phase algorithm
State 3
3 phase algorithm
State 4
and so on …
A state is a snapshot
of the system at a given
point in time, for example:
how much concrete is in a truck,
location of a scraper on a haul road,
the time of day, etc…
The 3-phase algorithm advances the model from its state at one
point in time to its state at the next point in time:
phase 1: determine the next point in simulation time, and advance the simulation clocks:
(eg: update the remaining duration for a truck traveling
on a haul road);
phase 2: update the state of each component to match the new
point in time:
(eg: update the amount of concrete in the foundation);
phase 3: decide what will happen over the next period in time:
(eg: if a truck has dumped its load, should it now start to
return to the excavator or go for refueling?)

3. Applications: Planning the effective use of resources:
How many trucks to use;
What capacity concrete mixers to minimize duration;
Designing and improving construction methods:
Whether to use cranes with skips or concrete pumps to pour concrete;
FIFO (first-in-first-out) queues, or serve trucks with the largest capacity first;
Estimating probable project durations.
Estimating the influence of unforeseen circumstances on progress.
Monitoring and controlling work in progress.

4. 6.2 THE CYCLONE METHOD Fig. 6-2:Main CYCLONE Modeling Components
The NORMAL activity: this is performed by productive resources (equipment, crews, etc..) and it typically takes time to perform.
The COMBI activity: this is similar to the NORMAL activity, except that it requires a resource to be available on every preceding queue node. A resource is taken from each preceding QUEUE NODE and combined into 1 resource for the execution of the activity. It can only be preceded by QUEUE NODES.
The QUEUE NODE: this represents a point in a system where productive resources may have to wait to be processed. A resource will wait here until it can be combined with a resource from each of the other QUEUE NODES preceding a COMBI activity. An important function associated with this component is GEN which splits an arriving resource into several resources.
The FUNCTION NODE: this performs simple functions, an important example of which is to consolidate arriving resources into a single resource (the opposite of the GEN function).
The ARC : this connects the above components, defining the flow of resources through the system. 1 resource is output from every ARC leaving a component.
The ACUMULATOR : this measures system productivity at a specific location.

5. 6.3 APPLICATION TO SIMPLE EARTHMOVING SYSTEMS
Fig. 6-3:Simple CYCLONE Scraper Based Earthmoving Model
Haul
BULLDOZER CYCLE
Return
to start
of cut
Push
load
Dump
SCRAPERS CYCLE
Return
Wait for
scraper
Wait for
bulldozer
1bulldozer at start
3 scrapers at start

6. Fig. 6-4: CYCLONE Excavator-Truck Based Earthmoving Model
In this system, the excavator must perform 10 cycles to load one truck
Haul
Sleu
Wait for
excavator
GEN 10
CON
EXCAVATOR CYCLE
Dig
load
Dump
DUMP TRUCKS CYCLE
p = 0.95
Return
p = 0.05
Wait for
dump truck
Sleu
back
1 excavator (1.5 cu yd bucket)
Repair
5 dump trucks at start
(15 cu yd capacity each)

7. Fig. 6-5: CYCLONE Permit System
In this system, the truck needs a permit to cross a bridge. This is to
limit the bridge to one truck at a time.
Permit to
cross bridge (1)
permit is released
for next truck
Dig
load
Wait for
dump truck
excavator
Haul
Dump
Return
EXCAVATOR CYCLE
DUMP TRUCKS CYCLE
1 excavator (1.5 cu yd bucket)
5 dump trucks at start
(15 cu yd capacity each)
Sleu
back
GEN 10
CON
Wait for
permit
Cross
bridge