Construction Feedback

The Boone County engineering staff, along with the prime contractor and the precast manufacturer, were interviewed to obtain feedback on the bridge replacement project. Information obtained can be categorized into three main areas: project positives, project negatives, and suggestions to possibly improve the construction of such bridges.

6.2.1 Feedback from the Boone County Engineering Staff

Boone County was the owner of the bridge and responsible for the construction inspection throughout the project. Bob Kieffer, Boone County Engineer, and Scott Kruse, Assistant to the Engineer, were both interviewed after the bridge was completed for feedback from the owner. During construction of the bridge, Dave Anthony was the Boone County Engineer, however, Mr. Kieffer, as Assistant Engineer, was intimately involved with the project. Mr. Kruse was the field engineer responsible for the construction inspection and was at the bridge site on a daily basis. A summary of the feedback from the Boone County engineering staff follows.

• The precast substructure caps were all set in a short amount of time and without difficulty.

• The deck panels were all set in a short amount of time and without difficulty. The delivery of the panels caused most of the delay while setting the panels, not the actual process of setting the panels.

Negative aspects of the project:

• The county did not save any time or money with this project. While the county was aware the project would be slightly more expensive than traditional construction, the engineers were under the impression there would be a time-savings involved.

• The Boone County engineers are not familiar with pipe piling. Concrete encased piles would have been preferred over the steel pipe piles. Repainting the piles will be more maintenance for the county.

• Boone County felt the design calculations for the piles were not conservative. Several piles had to be tapped the day after initial driving to meet bearing requirements.

• The quality of the panel finish was poor.

• Construction progress had to wait on the precast elements. The substructure could have been set earlier but the abutments had not been fabricated. Panel placement was also delayed because the panels were not on site.

• The precast abutment and pier caps cracked during transportation.

• The Iowa State Ready Mix representative was never present on the construction site when concrete was being placed. There were difficulties with the specialty concrete mix and having someone present from the concrete supplier would have been helpful.

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Suggestions for improvement:

• The backer rod used in the transverse joints did not work well. Instead of the backer rod, expansive spray foam might work better in the transverse joints.

• Better workmanship on all of the joints could have prevented the need for grinding the bridge deck. If grinding is absolutely necessary, joints should be finished one- fourth of an inch high to ensure the joints are ground smooth and prevent low spots. • The panels did not need a roughened finish since the deck was to be ground. The

joints would be easier to finish if the panels were not roughened.

6.2.2 Feedback from Petersen Contractors, Inc.

Petersen Contractors, Inc. (PCI) was the prime contractor for the Boone County bridge replacement project. Justin Clausen, project manager, and John Benjamin, foreman for the project, were both given a chance to offer feedback. Mr. Clausen compiled his feedback in a document which can be found in Appendix II. Mr. Benjamin was interviewed over the phone. A summary of the feedback from PCI follows.

Positive aspects of the project:

• Deck panel sizes worked out well. • Precast pier caps worked well. • Precast abutments worked well. • Post-tensioning worked very well. Negative aspects of the project:

• There were difficulties with the specialty concrete. The designer should have a better handle on the mix design of that concrete and the admixtures being specified.

• The formwork for grouting the post-tensioning channels and under the deck panels was time consuming (putting up the formwork took at least 100 man-hours, not including the time to strip the formwork).

• The deck grinding was poor. The ends of the deck couldn’t be properly ground because of the gravel approaches.

Suggestions for improvement:

• Use a beam with a wider top flange to allow more room for the post-tensioning channel.

• Modify the pier diaphragm pour so that none of the deck panels have to be removed. • Coordinate letting, shop drawings, fabrication, and construction so that cold weather

does not become an issue. If the project was let in the fall, the winter could have been used for shop drawing submissions and approval and fabrication of precast elements and construction could begin immediately in the spring.. This way, construction would not have to wait for the fabrication and delivery of precast elements and construction would be finished before cold weather.

• Review the end panel anchorages to make tendon placement easier.

• An overlay on the bridge would eliminate problems associated with grinding the bridge deck.

• A precast barrier rail would be much faster than the CIP barrier rail used.

• Use precast wing walls instead of CIP. The formwork for the wing walls was also time-consuming.

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6.2.3 Feedback from Andrews Prestressed Concrete

Andrews Prestressed Concrete fabricated all of the precast elements associated with this project. Teresa Nelson, project manager, compiled feedback in a document, which can be found in Appendix II. A summary of the feedback from Andrews Prestressed Concrete follows.

Positive aspects of the project:

• ISU and PCI were easy to work with.

• It was easy to resolve fabrication issues or mistakes and oversights in the plans. Negative aspects of the project:

• The anchor plate was not quite the full depth of the panel. This made it very difficult to assure that the plate was suspended off of the casting bed.

Suggestions for improvement:

• Look into a larger size mesh in end panels to allow for larger openings to aid in placement and consolidation of concrete.

• Change the design of the anchor plate in the end panels.

• Use larger diameter holes for the post-tensioning tendon to allow pipe sleeves to pass thru in lieu of butting against the anchor plate.

6.2.4 Feedback from Iowa State University

Researchers at Iowa State University provided feedback based on the fabrication and construction of the substructure elements tested in the laboratory. T.J. Wipf and F.W. Klaiber, as Co-Principal Investigators for the laboratory testing provided some feedback, a summary of which follows.

Positive aspects of the project:

• Reinforcement and the connection between the pile and CMP were easy to fabricate. Negative aspects of the project:

• CMP was not a standard size; had to be special ordered.

• Pipe piling was hard to find and not a common size used in Iowa; pipe was obtained out of state.

Suggestions for improvement:

• Use standard CMP sizes to reduce cost and eliminate special orders.

• Use piles that are standard in Iowa. This will make the piles easier to obtain and ensure owners and contractors are familiar with the product (see comments from Boone County Engineers Office).