I-35 NEX Central February 2024 Newsletter

February 2024: Issue 15

In this issue

1 l Superelevation: It's Not What You Think

2 l Construction Update

3 l Active Construction Sites

4 I Out on a Limb: Eccentric Bent Caps

5 l Contact Us

The I-35 Northeast Expansion (NEX) Central project consists of construction of approximately 9.5 miles of elevated, non-tolled lanes from I-410 North to FM 3009. The elevated lanes will provide one high occupancy vehicle (HOV) lane and two general purpose lanes in each direction. There will be direct connections to I-410 N and Loop 1604 W. Expected completion date is December 2027.

Superelevation: It's Not What You Think

Your eyes are not deceiving you. Yes, that column cap is tilted, 2.5 degrees, to be exact. This is known as superelevation.

When you hear the term "superelevation" in relation to road construction, you might think of super tall bridges, but that wouldn’t be correct. Superelevation refers to the rotation of road pavement to assist drivers by counteracting lateral acceleration produced by road curves.

What does this mean? When a driver navigates through a curve on a road or bridge, the road is often banked or tilted at an angle, which is known as superelevation. It helps drivers maintain a safe speed while navigating curved roads, helps prevent skids and rollovers, especially in wet or icy conditions or at high speeds. It also allows traffic to maintain some speed on curves, preventing excessive slowdowns and it also helps with driver comfort as they come around a curve.

Superelevation involves raising the pavement's outer edge above the curve's inner edge. This is an important safety feature in the design of any road with curves. The design of a superelevated road must be precise, and when done correctly, most people barely even notice it’s there. To see superelevation at work, just watch a NASCAR race. The banking on the tracks of the Sprint Cup series varies from 12 to 36 degrees.

Without superelevation, curves would have to be taken at much lower speeds. Large vehicles are particularly vulnerable to rollover crashes due to their high center of gravity.

The next time you drive through a banked curve on the highway, you can thank superelevation for keeping you safe and speeding up your journey.

Construction Update

Setting bridge beams on the westbound frontage road of I-410 near Perrin Beitel reached new heights.

Two significant milestones were achieved this month on the I-35 NEX Central project's direct connection from southbound I-35 to westbound I-410. On the westbound frontage road of I-410, near Perrin Beitel, eight bridge beams were placed on the column caps, reaching almost 75 feet above I-410. This marks the highest bridge beams that have been lifted on the project to date. Moreover, it was the first time the bridge beams were set during the daytime operation. Until now, all beam settings have taken place overnight. The reasons for the daytime operation were to set as many beams as possible before bad weather could delay the project's progress and the available space between the lifting operation and the traveling public.

Active Construction Sites

The map below highlights where active construction is currently taking place on I-35 NEX Central, indicated by the traffic cones. The active construction sites shown on the map below are intended to indicate major construction operations. You can view project information and lane closures at www.i35nex.com. Please note construction preparation work, including placement of barriers, is also ongoing within the limits of the project.

Excavation of new lanes of Loop 1604. The Loop 1604 westbound and eastbound bypass is closed for the demolition of the existing bridge and the construction of a new bridge. Drilled shafts and column foundations work continues in the area of the I-35 and Loop 1604 interchange. Retaining wall construction is also taking place in that area. Expect overnight closures of the westbound frontage road of Loop 1604 from Gateway Boulevard to Gateway Place for setting caps.

Drilled shafts, column, and cap work continues on the northbound frontage road of I-35 from Olympia Parkway to Evans Road.

Bridge construction continues on southbound I-35 in the Pat Booker Road area. Long-term left lane closure of the southbound I-35 frontage road from McMorris Boulevard to IKEA-RBFCU Parkway for drilled shaft and column construction continues in place.

Long-term closure of the left lane on southbound I-35 frontage road between Toepperwein Road and Judson Road for retaining wall, drilled shaft, column, and cap work. Long-term closure of the left lane on northbound frontage road of I-35 from Judson Road to Toepperwein Road for drainage, column, and cap work.

Long-term alternating lane closure on the southbound frontage road of I-35 between Thousand Oaks Drive and Whirlwind Drive for roadway reconstruction, paving, and drilled shaft work.

Beam setting, column and cap construction continues at the I-35 and I-410 interchange. Drilled shaft work north of Walzem Road on the northbound and southbound side of I-35. Long-term left lane closure in both directions on Fratt Road from I-35 to Austin Highway for drilled shaft, column, and cap work.

Bridge work continues in the area of I-410 from Perrin Creek to Perrin Beitel. Alternating lane closures on eastbound frontage road of I-410, entrance ramp closure, and right mainlane closure from Perrin Beitel to Austin Highway for striping and barrier work.

Out on a Limb: Eccentric Bents

"Eccentric bent caps" or "C-bents" on southbound I-35 near Loop 1604.

Have you noticed these oddly shaped column caps on the I-35 NEX Central project? One side of the column cap is longer than the other. These types of column caps are called "eccentric bents" or "c-bents."

C-bent bridge columns are columns that support the bridge deck through cantilevered beams on one side only. They are usually used where the bridge column has to be offset due to space restrictions, such as an existing roadway, or underground obstructions, such as utility lines.

The elevated lanes must align with the existing roadway, limiting flexibility to move left or right. However, adjusting the column positions can maximize space and overcome any site or functional constraints while still keeping the elevated lanes aligned.

C-bent design from the I-35 NEX Central project

Not only do C-bents look different at the top they are also different underground. Traditional monoshaft columns have a single drilled shaft beneath the column. A C-bent has two or more drilled shafts with a concrete footing below the column, which forms the shape of a “C,” hence the name C-bent.

Questions or Comments

I-35 NEX Central Project

(726) 800-4809

i35nexcentral@txdot.gov

Public Information Office

7330 San Pedro Ave

Suite 600

San Antonio, TX 78216

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