The roughly 180,000 daily motorists who traverse the Howard Frankland Bridge along Interstate 275 and across Tampa Bay can be forgiven if they view the ongoing construction work as nothing out of the ordinary or even eye-catching.

目前，大多数低级，大约三英里长的桥结构的唯一可见迹象是仍在形成的子结构。从一个项目终点看，完成的子结构工作的视图令人印象深刻地扩展到距离。

Since construction began in late 2020, the Florida Dept. of Transportation reports that, as of February, more than 1,200 of the 3,006 pilings necessary for the new eight-lane bridge’s foundations have been driven. Crews have constructed 120 of the project’s 549 bridge footings and completed 110 of the planned 549 bridge columns and 38 of the necessary 226 pier caps. With its substructure configuration matching that of the two twin bridges that comprise the current Howard Frankland—one of which will remain in place—the new span will feature 113 piers in support of its 112 spans.

Hundreds of concrete piles, columns and pier caps appear along the three-mile-long length of the emerging bridge structure.
Photo courtesy Archer Western

Despite the impressive achievement marked by those numbers, Greg Fullington, project executive for the Archer Western-Traylor Bros. joint venture leading construction of the $865-million design-build project, describes the work as “pretty standard.”

而且，尽管该项目作为低级结构的地位并没有将其作为“签名”桥梁的资格，但对于坦帕湾地区来说，这无疑是一个大项目，而不是一种。

这座新桥将作为对当前霍华德·弗兰克兰（Howard Frankland）的更新和扩展，由两个四车道结构组成：一座1950年代后期的桥梁，该桥梁从圣彼得堡（St. Petersburg）北行，并于1990年完成了一个结构。处理坦帕的南行I-275交通。

The “expansion” comes from the new bridge’s capacity being twice that of the existing four-lane spans. In all, the new bridge structure will comprise eight total lanes, including four general-use lanes for southbound traffic along with four tolled express lanes—two each for northbound and southbound.

Once the new bridge is completed in late 2025—per the schedule—southbound traffic will switch over to the new bridge and its four general-purpose lanes. Crews will then perform maintenance on the current southbound bridge before switching northbound traffic from the oldest span and onto the 1990s bridge.

The new bridge span doubles that of the existing structures and will feature eight travel lanes, including four tolled express lanes.
Image courtesy BCC Engineering

直接但棘手

富灵顿说，迄今为止，尽管与堆驾驶工作的进展较慢，但弓箭手西部 - 特雷洛兄弟的合资企业仍按计划进行。他认为，尽管堆积工作延迟，但在提早时间表打滑期间发起的夜间钻探使该项目保持正轨。

Another item that’s helped keep the contractor on pace is the state’s approval of a special permit issued by the Florida Dept. of Environmental Protection for use of a “mixing zone” for purposes of measuring turbidity caused by drilling and other operations. Extending up to 500 ft from the pier locations, contractors are able to measure turbidity from the edge of that zone instead of immediately adjacent to the work. To date, contractors have stayed within limits, helping to keep crews productive, says Fullington.

Since construction commenced in October 2020, crews have driven 40% of the necessary 3,006 piles. Like Fullington, Marianne Brinson, senior project engineer with Atkins, the project’s construction engineering and inspection firm, seems to downplay the project challenges as she describes construction of the bridge substructure as “straightforward.”

That may be true, but at the same time, the Tampa Bay geology has been throwing the team some curves. “This scope certainly is the most challenging on the project,” Fullington says. “This is very difficult foundation geology.”

Well-known for its irregularity, Tampa Bay’s geology can vary in seemingly random and isolated spots. For example, on numerous occasions—and as designed—the contractor has had to use the common method of splicing piles to reach bearing capacity. Sometimes, though, Fullington says, along the same pier line that required a spliced pile to reach capacity, crews have struggled to drill through rock.

That scenario played out in extreme fashion at pier 93, Fullington says, where crews had to drill through rock to get to a minimum tip of 75-78 ft for one pile. Along the same pier, about 50 ft away, however, crews drove spliced piles to approximately 250 ft without getting “near capacity on it,” he says.

该项目西端的这一观点显示了承包商在桥梁项目的两端的工作方式。
Photo courtesy Archer Western

Daniel Raymat, director of structures for BCC Engineering—and engineer of record for the bridge structures—concurs with Fullington that the project’s variable rock layer and unique soil conditions have “probably been the biggest challenge.”

From the construction of the two existing structures, engineers had plenty of historical data to rely upon as they precisely designed each of the 113 piers for the specific conditions they anticipated for each location.

“Each pier had to be uniquely designed for a specific soil condition,” Raymat explains, adding that, overall, pile lengths vary from 60 to 220 ft. Even in close proximity, the team expected “a lot of variability,” he says.

Despite the extensive historical information available to them, “We didn’t know at any given pier just how much variability there was going to be,” adds Ariel Millan, BCC executive vice president.

团队经验ected to see anywhere from 60 to 100 ft of variability between minimum and maximum pile depths on a single pier, Millan adds. Still, without being certain of what to expect at every pile location, “you have to assume you’re going to have to splice a certain number of piles.”

While the contractor expected the final number of piles to exceed the official estimate of 3,006, it remains to be seen if the joint venture gave itself sufficient excess piles. The number that would ultimately be required “was a big risk for us,” Fullington says. While he adds that the joint venture “did carry additional length in our estimate ... we’ve seen more piles run longer” instead of shorter than expected.

The 6.4-mile-long project also includes a causeway portion at its west end.
Photo courtesy Archer Western

So far, so good

像桥梁建造者一样，FDOT项目工程师Greg Deese同意，当前的施工阶段是“最关键的”。

“Once we get out of the ground, the job becomes a little simpler,” he says. “Once the pile-driving is done, it should be a really good job to finish up.”

To that end, FDOT states that beam placement is slated to start by late spring, followed by the commencement of deck construction by early summer.
到目前为止，尽管存在地下障碍，但承包商仍在按时保持计划的能力，这是FDOT的荣誉。

Deese said what has stood out to him when visiting the site is the safety consciousness of the crews, noting that “you can tell they’re taking pride in their work.”

Despite the hazards of marine work, the contractor says the project has been able to achieve a good safety record to date.
Photo by Scott Judy for ENR

布林森（Brinson）与阿特金斯（Atkins）有着类似的看法，并指出合资企业对现场工作人员进行调查的观点是其每月合作努力的一部分，这表明工人到目前为止感到积极。

To Brinson, those surveys confirm that “it’s obvious that everybody is clearly showing a great respect level for each other,” including the field workers.

To that end, Fullington says the joint venture has utilized such tools as recognition of Crews of the Month and other ways to keep employees engaged and otherwise proud to be working on this landmark project. The focus on workers is key to productivity, safety and keeping staff satisfied and on the payroll, he says.

Overall, despite what he calls an “extended learning curve” with the foundations, Fullington says “we’re where we expected to be, on schedule.”