PICKING UP THE PIECES: SOUTHERN CALIFORNIA SHORING COLLAPSE

During concrete placement for a 16 inch-thick post-tensioned slab of a new bus terminal in southern California, the formwork shoring collapsed. In addition to destroying the new placement, the collapse impacted and engulfed the existing deck below with a snarled mess of wet concrete, steel reinforcement, shattered formwork, and mangled shoring components.

Initially retained to investigate the cause of the shoring collapse, engineers from Pivot quickly took on an increasing role to remediate the affected existing structure and ensure its safety. While simultaneously working on the collapse investigation, Pivot personnel designed repairs to the post-tensioned beams and slabs as well as the supporting columns, and worked with the client to implement the repairs.

After the collapse debris was completely removed, engineers from Pivot investigated the integrity of the existing deck, which bore the brunt of the collapse. Pivot personnel used a suite of nondestructive testing techniques, including surface penetrating radar and impact-echo, to determine that the structure below the collapse was sound and safe for use.

When future end users expressed continued concern for the building’s safety at the collapse area, the owners requested a load test of the structure. Pivot personnel designed and managed the test, which included 4 temporary pools filled with 27 inches of water, safety shoring below, instrumentation, real-time data collection, and coordination of work with all parties. Engineers from Pivot closely monitored slab and beam deflections throughout the load test using string potentiometers. The load test results confirmed conclusions from the nondestructive evaluation—the portion of the structure in question is entirely safe and ready for service.

PROJECT SERVICES:

Collapse Investigation

Structural Assessment

Load Testing

Structural Repair Design

Deflection Monitoring

Nondestructive Testing

Impact-echo

Surface Penetrating Radar

Ultrasonics