Challenges and Opportunities for Innovation in the Public Works ...

project team, including project management, the owner, engineering,
and construction.
Computerized modeling also provides the capability to more fully
integrate both design and construction with the facility's
operations and maintenance requirements. This can be achieved by
passing the as-built model to the owner for future use and linking
the model to the owner's customized plant database.
Construction used the proposal model to refine the demolition
sequence of the existing precipitators and duct work. Crane
studies were conducted with a library of premodeled cranes to
analyze access, placement, capacity, and boom reach. A 4600
Manitowoc luffing tower crane was selected based on capacity,
reach, and the minimal number of setups required. After the crane
was chosen, sizes of the existing duct-work sections were then
identified for removal. The 3-D modeling system enables densities
to be applied to each modeled solid and the corresponding weights
to be determined. Cuts in the duct work were identified that
maximized the size of the sections to the capacity of the crane.
Centers of gravity were also calculated for each duct section to
identify rigging pick points. Using this quantitative information
obtained from the model, in conjunction with 3-D graphic images as
a guide, a preliminary outage demolition schedule was developed
using Primavera's Finest Hour scheduling package. The demolition
sequence model was then refined based on the critical path and
manloading capabilities shown on the schedule.
When the design reached the final stages, construction made copies
of the models and began to take them apart to experiment with
different construction scenarios. Duct work was again sized to the
capacity of the crane at the placement boom length. The new duct
work installation sections were analyzed and scheduled similarly to
the duct work removal sections. The demolition and installation
sequence models were integrated to facilitate a complete outage
construction sequence. This sequence model revealed that
modifications needed to be made to the corresponding duct work
construction schedule where original assumptions did not hold.
Isometric piece mark sketches were then created that identified the
duct mark number, weight, and sequence of installation. These
sketches were sent to the duct vendor, at their request, to assist
in the duct work fabrication and delivery schedule (Figure 3).
Using the 3-D system, construction personnel developed their own
erection drawings from the engineering models. Pipe spool sizes
and field weld locations were identified on the model, based upon
construction requirements. Isometric sketches were then developed
with each spool piece, hanger, and field weld identified. Welding
procedures and test information were included for each weld. The
materials management module provided an automatically generated
materials list, by spool piece, for each pipeline, which was fed
into the purchasing system. The isometric sketches and bills of
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