Earthquake Retrofit Study (Rebar in floor slab)

A large ongoing earthquake retrofit project is underway at a large medical college hospital. During the upgrades, a large structural enhancement beam is planned in the basement. The concrete will be poured through the first floor slab into the beam forms, and therefore, requiring coring through the structural slab. In order to not damage the structural integrity of the floor, we were called upon to provide geophysical services in marking out the rebar in the floor slab.

Systematic traversing and continuous monitoring with GPR was conducted over the search areas. GPR traversing was performed at each of the proposed core locations using a 900 MHz in order to identify rebar and beams. Additionally, a M-100 rebar locator was used to provide correlation/confirmation with the GPR data. The use of both instruments allowed us to map the rebar where they were spaced only a few inches apart.

In addition to mapping the floor reinforcement, several concrete columns and ceiling beams were scanned in order to delineate the configuration and spacing of the reinforcement. Both longitudinal and Traverse bars were identified.

900 MHz Antenna in use at the site

Rebar and Main Beam show in radar images.

M-100 rebar locator in use at the site.