I-75+Bridge+Collapse+–+Cincinnati

I-75 Bridge Collapse //Sharon Jankiewicz, BAE/MAE, Penn State, 2015 // toc
 * Cincinnati, Ohio - January 19, 2015 **

Introduction
Th e Hopple Street exit ramp collapsed onto I-75 S on January 19, 2015 during demolition at approximately 10:30 PM. One foreman was killed and the excavator operator was injured. As the center span collapsed, a semi truck crashed into the debris, injuring the driver. Demolition had been halted earlier in the week due to concerns about the upward deflection of some steel girders and inadequate remedial measures were put in place. The original overpass had been constructed during the early 1960s and consisted of three spans. The center span was 92 feet and was supported by the cantilevered ends of the east and west spans. Following a report from The US Department of Labor's Occupational Safety and Health Administration's Cincinnati office, the construction company, Kokosing Construction, was cited for two safety violations and fined $14,000.

Demolition Plan
The overpass comprised two piers and an east and west abutment as shown in Figure 3. The original demolition plan was submitted by Kokosing to the Ohio Department of Transportation on December 19, 2014. It outlined a saw and lift procedure which required the excavator to sit on the deck and place the slabs on a loader also on the deck. This method had a weight of 136,150 pounds, including equipment and total construction load (Peters 2014). According to a summary provided by John Householder of Kokosing, an alternative plan used a hoe and Genesis demolition tool sitting on the deck to chew up the concrete leading to a combined load of 110,800 pounds (Householder 2015). This plan was chosen and submitted to the ODOT on January 16, 2015 (Ayub 2015). The concrete deck was to be removed starting at the east abutment and then the steel girders would be removed, starting with the middle span (labeled Span 2 Sequence A in Figure 4), followed by the east span, and then the west span (Householder). Kokosing released the demolition plans to the public a day after the Cincinnati Enquirer threatened to sue for withholding the plan (Williams February 6, 2015).

[[image:failures/SAJ Tie Down Design.jpg width="445" height="552" align="right" caption="Figure 5 | Tie Down Design (courtesy of Kokosing)"]]Collapse
Construction company Kokosing Construction had a $91 million contract to remake a 1.6 mile stretch of Interstate 75 which included the Hopple Street interchange that crossed over I-75 (Williams, February 6). Demolition began on the night of January 18 beginning with crunching the concrete slab beginning at the east abutment and working west, as outlined in the revised demolition plan. As the concrete was removed, the remaining steel girders began to lift from their supports on the east abutment. Work was halted and an engineer was called in to provide a solution which was provided the next morning, but not reviewed by ODOT (Williams February 6, 2015). The engineer drew up a sketch calling for a 3/4" diameter coil rod through the bottom flange of the girders and a steel angle that was anchored into the abutment using 1" Hiliti Kwik Bolt anchors (Ayub 2015).

These changes were made by the afternoon of January 16 and demolition work began around 9 pm (Ayub 2015). The collapse occurred later that night at around 10:30 PM and I-75 was not to be closed during the demolition of the east span. According to documents released by Kokosing to the Cincinnati Enquirer, Kokosing faced a penalty of $3,000 for every 15 minutes I-75 had to be closed (Pilcher 2015). The center span gave way first and the east span quickly fell as well (Ayub 2015). A construction worker standing on the center span was killed, the excavator operator sustained injuries, and the driver of a tractor trailer driving on I-75 South crashed into the collapsed center span (Pilcher 2015). I-75 South was closed for nearly 24 hours while debris was cleared away (Pilcher 2015).



Investigation & Cause of Failure
OSHA began their investigation on January 22, 2015 with a team from the Cincinnati Area Office and the Directorate of Construction department (Ayub 2015). Kokosing also began their own investigation (London). While the investigations were ongoing, Kokosing would have an internal engineer and an Indianapolis-based engineering firm develop demolition plans simultaneously and only proceed if the plans agreed (Williams February 16, 2015). According to analysis by OSHA, the two girders supporting the excavator on the east span were subjected to an uplift force of 18,000 pounds as the concrete deck was removed, which was not accounted for in the original demolition plan (Ayub 2015). Although the anchors added on the day of the collapse were to counteract that uplift, the Hilti anchors did not have adequate axial tension and shear capacity and were only embedded 4.5 inches into the abutment (Ayub 2015). Even with the full 6 inches of embedment, the anchors still would have failed (Ayub 2015). Each girder of center span only had two bolts connecting to the girders of the east and west spans, and as the east span lifted, these bolts failed in tension and the center span fell as one piece (Ayub 2015).

Legal Action
OSHA concluded that the demolition plan was flawed and the field modifications were not adequately designed by the professional engineers (Ayub 2015). Although the Ohio Department of Transportation reviewed the documents, OSHA stated that "the contractor and not ODOT is responsible for the accuracy and completeness of the plan prepared by the contractor (Ayub 2015). On July 15, 2015, OSHA issued two citations for $7,000 each which Kokosing agreed to pay by August 31 (Hill 2015). The first violation was for placing the excavator on the deck during demolition which did not have sufficient strength as the deck was removed, and the second violation was for continuing demolition "without ensuring the corrective methods were effective in preventing collapse of the structure" (Hill 2015). As a part of these citations, Kokosing also agreed to have an independent engineering firm conduct bridge engineering surveys for five years (OSHA 2015). The family of the worker killed in the collapse sued the Ohio Department of Transportation for unspecified damages and $11,295 for funeral expenses (Thompson 2015). In total, the family sought damages of $25,000 as ODOT was responsible for safety of all workers (Carl 2015). The Ohio Department of Transportation responded by denying most of the allegations and claimed that the worker assumed the risk of injuries and death and was negligent (ODOT 2015). As of July 15, 2015, ODOT declined to comment to the news on the pending litigation (Foxx 2015).

Lessons Learned
As a result of this collapse, Kokosing learned that there needed to be more review of their demolition plans, even though they had been demolishing bridges since 1980 (Williams February 16, 2015). The sequencing of demolition is quite important and engineers need to understand how loads change throughout demolition. Based upon these changing loads, if existing conditions cannot support the loads, it is equally as important to design a support that can account for the demolition loads.

Conclusion
The Hopple Street overpass was a preventable collapse that resulted from poor assumptions of loading conditions and rushed calculations. Demolition plans had changed but they were not scrutinized as closely as they should have been. When the steel girders began lifting from their supports during demolition, workers understood that there was a problem, but the engineers did not adequately size the connection for the current loads. This caused the loss of life of one individual and caused injuries to two others. Even if work is limited by a tight schedule (especially when working near roads that must remain open during demolition), engineers are still expected to give each calculation the same level of care as any other calculation.

Additional Resources
Requires ENR login.
 * Cho, Aileen (February 2, 2015). “Contractor: Collapsed Ohio Overpass Had Engineer-Stamped Demo Plans” Engineering News-Record.**  (October 1 2015).