Project Description:
In late September 2001, after
the Army and the FBI had completed their crime scene investigation, ECS was
called upon to complete two major tasks. The first was to assist the Structural
Engineer of Record in determining how much of the fire-damaged concrete
structure required demolition. The second was to determine if additional piles
were required to support the replacement structure, or demonstrate that the
existing foundations could support the higher loads of the replacement
structure. ECS, Ltd. was later retained to perform concrete quality control
testing during replacement of the concrete structure. The
ECS Involvement:
·
ECS performed concrete coring operations to obtain samples of
damaged and undamaged concrete to provide a comparison for evaluation. Tests
were performed on the concrete including compressive strength testing of the
cores as well as Petrographic analysis. The reinforcing steel was subjected to
metallurgical and tensile strength testing. Utilizing the data developed by
ECS, Ltd., the Structural Engineer of Record defined the limits of demolition
required. The data was also useful in the design of structural upgrades to
beams and columns subjected to high heat stress to limit the amount of
demolition required.
·
ECS performed soil load testing designed to account for the
replacement structure for the damaged portion being able to resist various
internal and external forces; one that would be heavier than the original
structure. Having to perform the foundation load test with the damaged
structure overhead presented several major challenges.
·
Additional vibration could not be induced which may further
compromise the integrity of the structure.
·
Due to low overhead clearances within the structure, the use of
driven reaction piles or dead weight reactions was unfeasible.
·
Columns and the 2nd floor above were continuously
monitored for settlement and distress during the loading test procedures.
·
ECS monitored concrete placement, tracked curing conditions, and
sampled and tested more than 5,000 concrete cylinders using an on-site
laboratory. Due to the accelerated construction schedule, three full-time ECS
technicians monitored concrete operations during extended construction shifts.