U. S. Department of Labor
Occupational Safety and Health Administration
Directorate of Science, Technology and Medicine
Office of Science and Technology Assessment
Overhead Launching Gantry Crane
Safety and Health Information Bulletin
Safety and Health Information Bulletin
SHIB 05-01-2006
This Safety and Health Information Bulletin is not a standard or regulation, and
it creates no new legal obligations. The Bulletin is advisory in nature,
informational in content, and is intended to assist employers in providing a
safe and healthful workplace. Pursuant to the Occupational Safety and Health Act,
employers must comply with hazard-specific safety and health standards
promulgated by OSHA or by a state with an OSHA-approved state plan. In addition,
pursuant to Section 5(a)(1), the General Duty Clause of the Act, employers must
provide their employees with a workplace free from recognized hazards likely to
cause death or serious physical harm. Employers can be cited for violating the
General Duty Clause if there is a recognized hazard and they do not take
reasonable steps to prevent or abate the hazard. However, failure to implement
any recommendations in this Safety and Health Information Bulletin is not, in
itself, a violation of the General Duty Clause. Citations can only be based on
standards, regulations, and the General Duty Clause.
Purpose
The purpose of this Safety and Health Information Bulletin (SHIB) is:
To inform overhead launching gantry crane users of the hazards
associated with deviating from the manufacturers guidelines on the use of
overhead launching gantry cranes, such as unanticipated movement or collapse
of the structure during use;
To highlight that all employers using overhead launching gantry cranes
in segmental or similar bridge construction must comply with all
manufacturers guidelines, including proper anchoring of the cranes during
launching, to prevent transversal or longitudinal movement of the
structure; and
To provide information that employers can use to address these hazards.
Background OSHA's Toledo, Ohio, Area Office investigated a
fatal accident involving the collapse, during a launch sequence, of an overhead
launching gantry crane used during segmental bridge construction. The equipment
involved was an overhead truss with a self-launching under-bridge (overhead
launching gantry) manufactured by Paola De Nicola of Italy for the construction
of the Maumee River Crossing in Toledo, Ohio (see Figures 1 and 2).
Figure 1: General Configuration of the Overhead Launching Gantry
Manufactured by Paola De Nicola for the Maumee River Crossing
For problems with accessibility in using figures and illustrations in this
document,
please contact the Directorate of Science, Technology and Medicine at (202) 693-2300.
Figure 2: Two Launching Gantries Side-by-side
For problems with accessibility in using figures and illustrations in this
document,
please contact the Directorate of Science, Technology and Medicine at (202) 693-2300.
The launching gantry is used to place concrete bridge and pier segments for
elevated roadways and bridges by spanning the distance between a finished road
segment and the next roadway pier or column. While spanning this distance, the
launching gantry picks up each bridge segment and suspends the segments from
beneath the overhead truss moving the segments into place. The segments are then
epoxied together and post-tensioned into place. Following the successful
placement of the roadway segments beneath the overhead truss, the entire
launching gantry is then moved forward to the next span along its previously
launched under-bridge. The under-bridge provides a temporary bridge over the
span for the front leg of the launching gantry to travel and position the
structure over the next span. (See Figure 3)
Figure 3: Launching Gantry with Suspended Segments
For problems with accessibility in using figures and illustrations in this
document,
please contact the Directorate of Science, Technology and Medicine at (202) 693-2300.
For this particular design, the manufacturer required the
use of four anchoring bars for each of the four rear legs (sixteen total
anchoring bars) and two anchoring bars for each of the two telescoping front
legs (four anchoring bars total). The anchoring bars in the rear were designed
to be pre-stressed to 600 kilo-Newton's per bar (approximately 135,000 pounds of
force per bar) to provide resistance to the longitudinal and transversal forces
primarily during the launching of the under-bridge. The front leg anchors were
to be pre-stressed to resist transversal forces, such as those created by wind.
Accident Investigation
The accident investigation revealed that the employer had not designed the pier
segments to accommodate each of the anchoring locations, reportedly because of
congestion in the segments with other items such as stressing cables. It was
further determined that the employer used only a few anchoring bars during the
initial launches and as work progressed began using fewer and fewer anchoring
bars. On the day of the accident, there were no anchoring bars for the four rear
leg and only one anchoring bar in each of the front legs. Additionally, the
front leg anchors had not been stressed to the appropriate force and were only
tightened with a wrench. A few months prior to the collapse of the launching
gantry, the employer had experienced a movement of about 2 centimeters at the
rear legs during a launch when using a total of only two rear-leg anchoring
bars.
The manufacturer's instructions provided that such movement could lead to a
collapse of a launching gantry.
Figure 4: View of the Launching Gantries after the Accident
For problems with accessibility in using figures and illustrations in this
document,
please contact the Directorate of Science, Technology and Medicine at (202) 693-2300.
Conclusion
OSHA's Cranes and Derricks standard, 29 CFR 1926.550(a)(1)
requires
employers to comply with the manufacturer's specifications and limitations
applicable to the operation of any and all cranes and derricks.
In the event that manufacturer's specifications are not available, the
limitations assigned to the equipment shall be based on the determination
of a qualified engineer competent in the field; such determinations must
be appropriately documented, recorded and available for review, as
necessary, by affected parties and any authorities having jurisdiction.
Reference Standard
29 CFR 1926.550(a)(1) - The employer shall comply with
the manufacturer's specifications and limitations applicable to the operation of
any and all cranes and derricks. Where manufacturer's specifications are not
available, the limitations assigned to the equipment shall be based on the
determinations of a qualified engineer competent in this field and such
determinations will be appropriately documented and recorded. Attachments used
with cranes shall not exceed the capacity, rating, or scope recommended by the
manufacturer.
