MGS Transition from Full to Quarter-Post Spacing

Report Number(s): 610211-01-4

Description: The 181 ft-3-inch-long test installation was comprised of a 31-inch high, 12-gauge, 4-space, W-beam guardrail system. The W-beam rail was supported by 72-inch wide-flange posts with 14-inch-tall wood blockouts. TxDOT DATs terminated each end of the guardrail system. Beginning with the upstream DAT, there were four distinct sections of the installation:

1. a 49 ft-3-inch-long section (posts 3 through 10) with full post spacing at 75 inches;
2. a 75-inch-long transition section (posts 10-11-12) with half post spacing at 37½ inches;
3. a 62 ft-6-inch-long section (posts 12 through 52) with quarter post spacing at 18¾-inches; and
4. a 43 ft-9-inch-long section (posts 52 through 60) with post spacing at 75 inches. In the full post spacing sections, a 10-inch button-head guardrail bolt secured each blockout to a post.

In the quarter and half post spacing sections, the bolts secured the rail only at half post spacing. Therefore, no additional slots were cut in the W-beam rail. Additionally, the quarter and half post spacing sections did not have posts bolted to the rail at splice locations. In the full-post spacing sections, the W-beam rails were spliced at midspan between the posts. The wide-flange posts were embedded 40 inches deep in drilled holes that were backfilled with crushed limestone base and compacted to meet MASH strength requirements

Test Level: 3

MASH Test Number: 3-21

Proprietary/Non-proprietary: Non-proprietary

Pass/Fail: Fail

Evaluation: Full-Scale Crash Testing

Sponsor: Texas Department of Transportation