| 1. |
A new bridge name Basnight Bridge was built to replace the Bonner bridge in 2019. Part of the old bridge Bonner bridge was scheduled to remain for the pedestrian use. |
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True |
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False |
| 2. |
On April 14, 2021, when PCL employees were dismantling the last span left of the Bonner Bridge (Span 145), the span collapsed prematurely. A PCL employee engaged in steel cutting operations was killed. |
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True |
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False |
| 3. |
The superstructure ("Structural parts of the bridge that provide the horizontal span) of the three high-rise spans was supported on four bents, numbered from the north as Bent 143 to 146 (see Figures 3 and 5). |
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Four bents |
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Two bents |
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Six bents |
| 4. |
Which one of the plans below was issued as initial demolition plan of the bridge. The plans required the use of a crane located on a barge under the bridge for loading bridge components onto a cargo barge located under the bridge. The demolition plan included drawings and calculations. |
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Option One specified that the demolition should begin at one exterior span and proceed linearly to the other exterior span. |
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Option Two stipulated to remove one exterior span, then the other exterior span, and finally the middle span. |
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Both options were issued as a plan for demolition. |
| 5. |
On August 23, 2019, KCI modified the initial demolition plan and allowed PCL to use cranes on a |
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trestle positioned alongside the existing bridge |
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crane on a barge. |
| 6. |
On October 10, 2019, KCI issued the modified demolition plan specific for the three high rise spans, which incorporated the following five requests from PCL:
- remove trestle and add the "Crofton" crane on a barge below for removing Spans 144 to 146;
- cut diaphragms / lateral bracing 7 F8 between the two interior girders before securing
- rigging to girders;
- remove the previously designed excavator from the bridge deck (no equipment on top of the bridge deck);
- increase deck panel pick size; and
- rigging updates.
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True |
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False |
| 7. |
On January 27, 2021, KCI provided PCL with the final demolition plan for the three high-rise spans. In the final demolition plan, KCI ___________ Option Two because PCL would remove the three spans in a linear process. |
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Did not include |
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Did include |
| 8. |
KCI planned to demolish the three high-rises pans in five phases. The demolition plan is reproduced in Figure 10 and outlined in the steps below:
- Make transverse cuts on concrete deck in Span146. The transverse cuts shall extend one foot past the centerline of the exterior girders (see Phase 1 in Figure 10).
- Remove overhang / parapet sections in Span146,including:
- Install rigging on the overhang / parapet section to be removed;
- Make longitudinal cuts on the centerline of the exterior girders supporting the overhang / parapet section to be removed to free the concrete section (see Figure 11);
- Lift the overhang / parapet section and lower the section on to a barge below the bridge; and
- Repeat steps (a) to (c) to remove remaining overhang / parapet sections in the span.
- Make longitudinal cuts over girder centers to free concrete deck pieces. The longitudinal cuts shall be made on parts that will be immediately lifted, and the entire concrete deck of the span shall not be precut. Concrete deck pieces shall be rigged and lowered onto a barge below the bridge.
- Cut diaphragms and bottom lateral bracing between the two interior girders.
- After the concrete deck is completely removed in Span146, install rigging on steel girder sections, and the four girder sections shall be rigged and lowered onto a barge below the bridge in pairs.
- Repeat steps1 to 3 to remove the concrete deck slabs and parapets in the middle Span 145.The steel girders and bracing shall be uncut and remain in place after removing concrete deck slabs and parapets.
- Repeat steps1 to 3 to remove the concrete components in Span 144.
- Once the concrete components in Spans144 and 145 are removed, repeat steps 4 and 5 to remove steel girders in Span 145.
- Repeat steps 4 and 5 to remove steel girders in Span 144.
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True |
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False |
| 9. |
Based on the evidence collected, observations of the collapsed structure, and structural analyses performed, OSHA concludes that: The contractor retained a structural engineering firm to develop a demolition plan for the three high-rise spans of the bridge. However, the contractor did not follow the plan to remove the bridge spans. |
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Did follow the plan |
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Did not follow the plan |
| 10. |
The contractor used different demolition sequences and developed its own demolition plans without performing any engineering surveys and calculations to determine the adequacy of the structure and the potential for unplanned collapse of any portion of the structure during the demolition. Unfortunately, the contractor carried out the demolition operation of the three high-rise spans in such a way that, ____________________________ resulting in the premature collapse of the navigation span. |
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the structural members were loaded beyond their load-carrying capacities |
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The barge would not be able to have such a big, elevated crane on top of it. |
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