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Aging Dallas Bridge Saved
The Houston Street Viaduct is a four lane vehicular bridge crossing the Trinity River Flood Zone south of downtown Dallas. When originally constructed in 1912, the viaduct was the longest concrete bridge of its kind in the world with a total length recorded at 5,106 lineal feet. The original cost of construction in 1912 was $675,000.
Flash flooding and high river levels had severely eroded the soil bank of the Trinity River surrounding structural Pier #44. Previous attempts to reinforce the pier footing with steel sheet piling and an additional 24-inch thick concrete pile cap had proven to be no match for raging floodwaters. The sheet piling was ripped open, exposing the concrete piles of the pier's footing to additional soil erosion.
Due to the weakened state of the footing for Pier #44, the pier itself developed structural cracking in each of its three legs. Some cracks were recorded up to 2 inches in width. The structural integrity of the pier was now compromised and permanent repairs were required.
Engineering survey and design specifications completed by HNTB Architects and Engineers of Dallas called for the following long-term repairs to be implemented before further damage was sustained by Pier #44.
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Structural enhancement of Pier #44.
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Re-slope the earth banks of the Trinity River in the surrounding area of Pier #44.
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Form and pour the exposed cavity under the concrete pile cap with lean concrete to completely encapsulate the exposed concrete pile group.
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Allow lean concrete to reach design strength before removal of damaged steel sheet piling and other debris.
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Form and pour a 2-foot thick reinforced concrete / slurry wall to depths averaging between 30 to 36 feet. This wall was to completely surround the concrete pile footing group.
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Form and pour a 2-foot thick concrete pile cap heavily reinforced and tied into the surrounding wall described above.
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Reslope surrounding earth banks and backfill against slurry wall.
Since the scope of the work would require the extensive use of heavy equipment in close proximity of Pier #44, the engineering report called for the structural enhancement to be completed before heavy work could commence. Design called for the addition of 18 - 1.375-inch diameter, high-strength threaded bars bolted through the legs of the concrete pier. In addition, all cracks in the pier legs were to be repaired by a combination of cement grout pumping and epoxy resin pressure injection.
The services of CSDA contractor-member Concrete Penetrating Co. of Dallas were contracted as a specialty subcontractor by General Contractor, T.J. Lambrecht, for the installation of the threaded bars and injection of concrete structures. One of the main reasons that Concrete Penetrating Co. was selected was because it was the only company in the region capable of performing both crack repair and core drilling with 100% of its own work-free. Concrete Penetrating Co. was equal to the task in manpower, experience and related equipment required to complete the work within the schedule of the project's timetable.
Factors that complicated the job consisted of the unavailability of water or electric power on the site while access to the pier was via the flood plain. In addition, the 2.50-inch diameter boltholes were to be drilled horizontal and parallel to the top of the pier cap while the face of the pier sloped approximately 14 degrees from plumb. This required the construction and use of an adjustable jack plate to mount the drill securely and achieve the tolerances specified.
To begin this job, Concrete Penetrating Co. first performed high-pressure water blasting on all structural cracks in the columns of the pier to remove impacted river debris. Next, non-shrink cement grout was pumped into the large cracks in the pier columns while epoxy resin was injected into the smaller cracks by a combination of bulk loader injection of epoxy paste and pressure pump injection of epoxy injection resin.
Next, the 2.5-inch diameter holes were core drilled through the columns of the concrete pier for the installation of high strength, threaded bar. Through the use of the original structural drawings and on-site rebar meters, the consulting engineer group located the holes that were to be core drilled in a manner that minimized the disturbance of the original reinforcement. The length of the holes varied from 14.25 feet at lowest level to 11.5 feet at highest level (columns taper in thickness). The equipment utilized for diamond core drilling consisted of a high speed hydraulic drive drill motor complete with roller carraige. Power was supplied by a trailer mounted diesel hydraulic unit complete with 200 feet of high pressure hydraulic hose. The diamond core drill bit was 2.5-inches in diameter in a continuous tube design with extension tubes of caried length.
Next, Concrete Penetrating Co. drilled horizontal 12-inch diameter x 8-inch deep countersinks at either end of 2.5-inch diamond core holes to accommodate the threaded rebar bearing plate. Then the 1.375-inch diameter high-strength threaded bar complete with bearing plate and nut was installed.
After the temporary rebar was installed, the 1-inch diameter x 30-inch long cement grout injection ports were core drilled at 45-degree angles to intersect the 2.5-inch diameter bolt cavity. Identical bleed ports were core drilled at opposite ends of the bolt cavity. Then the threaded rebar was removed and followed by a high-pressure water blast (5000 PSI) throughout the threaded rebar cavity and countersinks to remove slurry paste from the core drilling process. Last, all eighteen lengths of the threaded rebar were installed and torqued to specified load. The exposed ends of the threaded rebar were coated with a combination corrosion inhibitor / cement grout bonding agent. To complete this job, the threaded rebar cavity and countersinks were pumped to point of overflow with non-shrink cement grout, the plywood forming was removed from the countersink, with a complete dressing-out of countersinks and coating with a penetrating concrete sealer.
This job was completed in a 4-week period in the fall of 1996. There were 18 - 2.5-inch diameter holes averaging 13 lineal feet for a total of 235 lineal feet, 36 - 12-inch diameter x 8-inch deep countersinks, and 36 - 1-inch diameter x 30-inch deep grout injection ports at 45 degree angles drilled.
Reasons for specifying concrete drilling included the structural integrity of the Pier and accuracy of the holes drilled. The Pier was an 85-year old structure in distress. The main concern was to structurally reinforce the pier with 18 high-strength bars while not adding any further vibration to the structure. Diamond core drilling provided a clean accurate hole without disturbing the structural integrity of the pier.
In summary, Concrete Penetrating Co. completed the structural enhancement of Pier #44 in 38 working days with approximately 760 on-site man-hours. With the completion of the structural enhancement of Pier #44, the major work specified by the consulting engineers will proceed on schedule. Expected completion of the project is spring 1997, with the total project estimated to cost $450,000.
Concrete Penetrating Co., headquartered in Dallas, Texas, was established in 1977 under the present ownership and currently employs a staff of 35.
The services of CSDA contractor-member Concrete Penetrating Co. of Dallas were contracted as a specialty subcontractor by General Contractor, T.J. Lambrecht, for the installation of the threaded bars and injection of concrete structures. One of the main reasons that Concrete Penetrating Co. was selected was because it was the only company in the region capable of performing both crack repair and core drilling with 100% of its own work-free. Concrete Penetrating Co. was equal to the task in manpower, experience and related equipment required to complete the work within the schedule of the project's timetable.
Factors that complicated the job consisted of the unavailability of water or electric power on the site while access to the pier was via the flood plain. In addition, the 2.50-inch diameter boltholes were to be drilled horizontal and parallel to the top of the pier cap while the face of the pier sloped approximately 14 degrees from plumb. This required the construction and use of an adjustable jack plate to mount the drill securely and achieve the tolerances specified. To begin this job, Concrete Penetrating Co. first performed high-pressure water blasting on all structural cracks in the columns of the pier to remove impacted river debris. Next, non-shrink cement grout was pumped into the large cracks in the pier columns while epoxy resin was injected into the smaller cracks by a combination of bulk loader injection of epoxy paste and pressure pump injection of epoxy injection resin.
Next, the 2.5-inch diameter holes were core drilled through the columns of the concrete pier for the installation of high strength, threaded bar. Through the use of the original structural drawings and on-site rebar meters, the consulting engineer group located the holes that were to be core drilled in a manner that minimized the disturbance of the original reinforcement. The length of the holes varied from 14.25 feet at lowest level to 11.5 feet at highest level (columns taper in thickness). The equipment utilized for diamond core drilling consisted of a high speed hydraulic drive drill motor complete with roller carraige. Power was supplied by a trailer mounted diesel hydraulic unit complete with 200 feet of high pressure hydraulic hose. The diamond core drill bit was 2.5-inches in diameter in a continuous tube design with extension tubes of caried length.
Next, Concrete Penetrating Co. drilled horizontal 12-inch diameter x 8-inch deep countersinks at either end of 2.5-inch diamond core holes to accommodate the threaded rebar bearing plate. Then the 1.375-inch diameter high-strength threaded bar complete with bearing plate and nut was installed.
After the temporary rebar was installed, the 1-inch diameter x 30-inch long cement grout injection ports were core drilled at 45-degree angles to intersect the 2.5-inch diameter bolt cavity. Identical bleed ports were core drilled at opposite ends of the bolt cavity. Then the threaded rebar was removed and followed by a high-pressure water blast (5000 PSI) throughout the threaded rebar cavity and countersinks to remove slurry paste from the core drilling process. Last, all eighteen lengths of the threaded rebar were installed and torqued to specified load. The exposed ends of the threaded rebar were coated with a combination corrosion inhibitor / cement grout bonding agent. To complete this job, the threaded rebar cavity and countersinks were pumped to point of overflow with non-shrink cement grout, the plywood forming was removed from the countersink, with a complete dressing-out of countersinks and coating with a penetrating concrete sealer.
This job was completed in a 4-week period in the fall of 1996. There were 18 - 2.5-inch diameter holes averaging 13 lineal feet for a total of 235 lineal feet, 36 - 12-inch diameter x 8-inch deep countersinks, and 36 - 1-inch diameter x 30-inch deep grout injection ports at 45 degree angles drilled.
Reasons for specifying concrete drilling included the structural integrity of the Pier and accuracy of the holes drilled. The Pier was an 85-year old structure in distress. The main concern was to structurally reinforce the pier with 18 high-strength bars while not adding any further vibration to the structure. Diamond core drilling provided a clean accurate hole without disturbing the structural integrity of the pier.
In summary, Concrete Penetrating Co. completed the structural enhancement of Pier #44 in 38 working days with approximately 760 on-site man-hours. With the completion of the structural enhancement of Pier #44, the major work specified by the consulting engineers will proceed on schedule. Expected completion of the project is spring 1997, with the total project estimated to cost $450,000.
Concrete Penetrating Co., headquartered in Dallas, Texas, was established in 1977 under the present ownership and currently employs a staff of 35.
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