Precast Units
Installation of the precast units was completed in 17 weeks. It involved
handling, positioning, and grouting of 5,565 precast units of 12 different
configurations. The work was accomplished by three crews working consecutively.
An erection crew was responsible for the unloading, initial erection,
and temporary bracing of the units. An alignment crew was responsible
for plumbing, connecting, and welding the units. A grouting crew followed
to confirm final alignment, grout connections, and cleanup.
The operation was allowed three weeks to reach its steady state on the
learning curve before starting the productivity analysis. The learning-curve
effect was observed as the production rate increased from 24 units per week
to over 50 units per week. This production rate, however, was still unacceptable
to the contractor who decided to include this operation in the productivity
study.
By taping the installation procedure, conducting brainstorming sessions,
and performing productivity analysis similar to that described for the tilt-up
operation, several productivity-related problems were identified. The analysis
showed that unnecessary extra handling occurred because the precast
units were delivered in the wrong order and frequently the units were loaded