Real-time monitoring of tower cranes

REAL-TIME MONITORING OF TOWER CRANES ON CONSTRUNCTION SITES
*M. A. NADAR, C. A. AWAKIAN, and H. K. KHOURY
American University of Beirut
Bliss Street
Beirut, Lebanon

REAL-TIME MONITORING OF TOWER CRANES ON CONSTRUNCTION SITES
ABSTRACT
Harsh and dynamic construction sites are generally equipped with cranes in order to rapidly and
conveniently move heavy loads from one location to the other. If not properly inspected and managed, this
operation can be very hazardous and lead to accidents. As such, a reliable and self-contained monitoring
system that can update construction and safety personnel about the status of the crane, the weight of the
load lifted, the location of the boom with respect to nearby buildings and other tower cranes, and the
weather conditions under which the crane is operating, is deemed necessary. This can lead to significant
time and cost savings as well as safety and productivity improvement due to the accuracy and immediacy
of relevant on-site crane information delivery. This paper evaluates the capability of wireless sensor
networks (WSN) for monitoring tower crane operations in construction environments. A reliable long
range WSN system is implemented and information is obtained from various special-purpose sensors
(temperature, vibration, wind, proximity, etc.) deployed at strategic locations on the crane. The sensors are
mounted on special motes that relay data to and from each other and a central hub. The latter continuously
monitors and manages network performance and relays incoming data to the host application. This
application, in turn, visualizes sensed data with the location of sensor nodes in 2-D construction space and
triggers the alarming system through a re-programmed definition of safe and prohibited conditions or zones
on site.
KEYWORDS
ISARC, Crane incidents, Construction safety, Crane monitoring, Crane automation
INTRODUCTION
The construction world has witnessed countless incidents relating to crane operation over the years.
Fortunately, data about these incidents has gradually been gathered, and the issue has become clearer. The
statistics available will be presented briefly, which will help one understand the nature of these incidents,
and will help put this research’s aim well into perspective. “A Review of Crane Safety in the Construction
Industry” written by Richard L. Neitzel in 2001 sets up an informative platform for the work to be
conducted. In this paper, Neitzel mentions ‘over a 1,000 construction injuries involving cranes and hoisting
equipment’ in a single year in 23 states in the U.S.A, which shows that crane accidents is indeed a serious
issue. The related causes for such incidents have been studied by several different individuals and
administrations over the years. Earlier, in 1996, OSHA (Occupational Safety & Health Administration
(US)) conducted a study enclosing 502 crane related deaths. The main causes were identified, and are
shown in Table 1. Another study was conducted by Linda Levine. In her 2008 paper titled ‘Worker Safety
in the Construction Industry: The Crane and Derrick Standard’, Levine studies the causes of fatalities at
construction sites in 2007. The information gathered is outlined in Table 2. A third study conducted by the
Health and Safety Laboratory in 2010, entitled ‘Tower Crane incidents worldwide’ also aimed at
discovering the cause of crane incidents between the years 1989 and 2009. The results are found in Table 3.

Table 1- Causes of Death from Crane Incidents(OSHA-1996)
Cause of Incident Percentage Occurrence (%)
Death by Electrocution 39
Dismantling/Disassembly 12
Boom Collapse 8
Crane Overturn 7
Rig Failure 7
Overloading 4
Hit by Carried Load 4
Other 19
Table 2- Causes of Crane Incidents (Linda Levine-2008)
Dismantling 34
Harsh Weather 18
Foundation Problems 2
Mechanical Problems 5
Mishandling 7
Electrical Problems 1
Other 33
Table 3- Causes of Deaths from Crane Incidents (Health and Safety Laboratory-2010)
Crane Falling 38
Crane Contact with Objects 17
Non-Crane Related 45
Looking at these statistics for a second, one can easily notice that there are some discrepancies regarding
the percentages between the different studies. These differences boil down to several different reasons
including the time the study was made, the sample size, and whether we are speaking simply about crane
incidents, or deaths from crane incidents. Back in 1996, according to Table 1, electrocution caused 39% of
deaths from crane incidents, whereas in 2008, it only consisted at 1%. This is probably due to the poor
wiring that was done in 1996. But looking at the percentages in a more general manner, one notices that
crane incidents, more often than not, happen due to very apparent problems, such as tipping of the crane, or
its contact with other objects. The methods proposed in this research will introduce possible solutions to
these problems, which if implemented properly, can reduce crane incidents by a significant amount.
METHODS
System Hardware
The core of this research is the tool we are using to read, transmit, and manipulate sensor data- The
“SmartMesh-XT™ Evaluation Kit”. ‘SmartMesh’ networks are dependable, particularly low-power,
wireless meshed and can be used for a broad diversity of monitoring purpose, such as structure automation,

industrial supervision, or remote site safety. Figure 1 shows the different items that come with the
evaluation kit, including 12 ‘Motes’ that can read data and transmit it wirelessly, and the ‘Smartmesh
Manager’, which manages the data from all the motes.
Figure 1: SmartMesh Evaluation Kit
There are many advantages to the hardware used. The motes have a very long range, extending up to 75
meters when placed outdoors. They are also ultra-low power; the motes can last for years doing their job
perfectly. Motes are able to read analog and digital data, send data wirelessly to the manager, serially to
another device, and have a digital output in order to actuate external devices. A vital characteristic of the
technology is that the motes can deliver the information of other motes that are much more distant from the
manager and thus extending the range of communication. In fact the motes may deliver their own data
collected by the sensors mounted on them in addition to data arriving by motes that lie further away, all
through wireless interaction. Moreover, the path of the message is self-healing, i.e. if one of the motes (for
an unknown reason) seizes from functioning, the mote that was using it as a trail (called “parent”) to
deliver its data will automatically choose another nearby mote to do the job. Figure 2 shows how the data is
sent between motes and the manager.
Figure 2 – Wireless Data Communication with Smartmesh
Distance Sensors
Photoelectric sensors (Figure 3) will be used to detect nearby objects and in this case, the proximity of
the hook to the lifting loads or the jib. They will also be employed to sense the proximity of other cranes in

the nearby area. Their sensing range is up to 3 meters, with diffusive reflective type and through beam type
ranging up to 50 meters.
Figure 3- Photoelectric sensors
Temperature Sensors
Precision temperature sensors (Figure 4), having a wide operating scale, will be placed on different
areas of the crane, and will be used to set the temperature range and warning signal discretionarily in case
the threshold temperatures are approached or exceeded.
Figure 4- Temperature sensor
Wind Sensors
The wind sensor is a four blade propeller (Figure 5). The prop’s rotation generates an “AC sine wave
voltage signal” that will be transmitted by the mote to notify the operator of severe weather conditions. The
location of the wind sensor must be at the very top of the tower in order to function at its best.
Figure 5- Wind Sensor

System Software
The Smartmesh kit comes with an application called ‘Smartmesh Console 1.6’ (Figure 6) that allows
the user to view all the information needed related to the motes and the manager. The program allows the
user to view the communication map, i.e. which signal is being sent where and by which mote. It gives an
overview of how the information is reaching the manager. The software also shows the actual sensor
voltages received, and the time that this information was received, which allows accurate analysis of the
data. Smartmesh Console allows you to put alarms on certain events, which means that an alarm will be
turned on when a certain sensor exceeds a pre-set value, or if a certain mote stops working. This makes our
system very reliable and very aware of what is happening on site. A final use of the program is that it can
send signals to the motes to shut down, to output a digital signal to start something, or to change which
motes communicate with which in order to get a better wireless network. In order to manipulate the data as
needed, a serial communication is set up between the manager and a laptop. Our project utilizes MATLAB
to receive the information, process it, and to convert the voltage values received to actual temperature,
distance, and other values. The datasheets of the sensors demonstrate the relationship between the voltage
values and the respective physical values of the sensor.
Figure 6- Smartmesh Console 1.6
System User Interface
The user interface for now is implemented on MATLAB. This interface displays the incoming data
from the motes in real-time, providing live 2-D movement of the crane, and graphs for thresholds and how
the physical parameters are changing over time. The interface is still primitive, and will be later upgraded,
giving the engineer more information in a more refined way. The work until now is purely proof of concept,
so the values used in the simulations are not coming from an actual sensor, but are pre-defined. Figure 7
shows the interface for the distance between the hook and load. The exact value is shown in the bottom
right corner, in addition to 2 views that will allow the engineer to have a general idea of the distances
involved. Figure 8 shows the interface for the wind speed, while Figure 9 shows the interface for the
temperature. The graphs are upgraded as new values are received. These are the panels the engineer will be
dealing with as sensor information is received from the motes.

Figure 7- Interface of Distance
Figure 8- Interface of Wind Speed
Figure 9- Interface of Temperature

RESULTS
Experiments have been conducted on the Smartmesh Kit, and on the response of the MATLAB interface
with random sensor values. Results have been positive in general with very little problems faced. Varying
voltages were connected to the Smartmesh motes, which were spread apart in an area randomly with
distances reaching 20 meters. The motes accurately read the voltages, and accurately transmitted them to
the manager. The Smartmesh console does a good job at displaying the data and showing information
about the wireless signals and general network performance. MATLAB also responded well with the
random values given; updates were happening quickly and smoothly, and the interface performed its
function well.
CONCLUSIONS
Construction sites are always prone to incidents especially when dealing with cranes. Our
proposed method aims to decrease these incidents as much as possible. The simulations have been positive
till now, but the real results can only be deduced when the actual sensors are employed and the system is
fully functional. The Smartmesh system is very efficient to use for sensor networks, and is an easy solution
to the problem many construction sites face. There is still a large amount of experiments to be done in
order to find the optimal location for the sensor placements. Through the coming months, our experiments
will become more factual, and results will become more tangible. Real sensors will be first employed on a
human sized crane on campus, later moving to testing on an actual crane in a real life construction site.
REFERENCES
Isherwood, R. (2010). Tower crane incidents worldwide. Retrieved from Health and Safety Executive
website http://www.hse.gov.uk/research/rrpdf/rr820.pdf
Levine, L. (2008). Worker safety in construction industry: The crane and derrick standard. Washington,
DC: Congressional Research Service. http://digitalcommons.ilr.cornell.edu/key_workplace/547/
Neitzel, R., Seixas, N., & Ren, K. (2001). A review of crane safety in the construction industry. Retrieved
from University of Washington website
http://depts.washington.edu/frcg/content/NeitzelCraneSafetyReview.pdf

Real-time monitoring of tower cranes

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