MGS with Longer Transition from Full to Quarter Post Spacing

Report Number(s): 610211-01-05

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 block outs. TxDOT DATs terminated each end of the guardrail system. Beginning with the upstream DAT, there were four distinct sections of the installation:

1. a 37 ft-6-inch-long section (posts 3 through 9) with full post spacing at 75 inches.
2. a 12 ft-6-inch-long transition section (posts 9 through 13) with half post spacing at 37½ inches.
3. a 62 ft-6-inch-long section (posts 13 through 53) with quarter post spacing at 18¾-inches; and
4. a 43 ft-9-inch-long section (posts 53 through 60) with full 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. Following the failed MASH test 3-21 on the transition from full to quarter post spacing, the research team modified the transition with the addition of a post. This was intended to lengthen the transition and minimize the pocketing behavior seen in the failed crash test.

Test Level: 3

MASH Test Number: 3-21

Proprietary/Non-proprietary: Non-proprietary

Pass/Fail: Pass

Evaluation: Testing + Engineering Analysis

Sponsor: Texas Department of Transportation