Box Culvert Guardrail – Phase II (405160-23)

Problem Statement

New or replacement guardrail installations frequently must pass over new or existing reinforced concrete box culverts for various types of highways. In many cases, the depth of embankment over the box culvert is very shallow and it will not allow the proper length of steel or timber posts to be installed without interfering with the concrete box culvert. A typical detail in these cases is a shortened W6x9 or W6x20 steel post attached to a steel base plate bolted into the box culvert. For existing box culverts, a proprietary epoxy injected bolt system or equivalent is used. These systems are difficult to install and can cause damage to the box culverts that are difficult to repair.

Background

In 1988, Hirsch and Beggs reported on a study using a W6x9 steel guard post with a base plate anchored to a 6-inch thick culvert slab. Static load tests and a full-scale crash test were performed on this design as part of this study. The testing performed on this design was successful. In 2002, Polivka, Reid, Faller, Rohde, and Sicking reported on a similar design bolted to a box culvert with approximately 9 inches of fill on top of the box culvert. The objective of this research was to develop a strong-post, W-beam guardrail system that can be rigidly attached to the surface of concrete box culverts. This new guardrail system was designed to meet the Test Level 3 (TL-3) performance criteria found in NCHRP Report 350. Dynamic pendulum and full scale crash testing on this design was also successful. Information from these studies as well as other research will be used to develop a new box culvert guardrail post design that meets TL-3 requirements.

Objective

Develop a guardrail design for typical box culverts that will meet TL-3, simplify contractor installation for the existing box culverts and minimize damage to the box culverts when hit.

Benefits

A properly designed TL-3 detail will create a safe operating environment for the public, reduce installation costs and minimize damage to the box culverts.

Recent Testing

During Phase I, a full-scale crash test was performed on a prototype W-beam guardrail on box culvert. Click on the link below for the report from Phase I testing:

Crash Testing and Evaluation of W-Beam Guardrail Box Culvert — Phase I
Executive Summary — Phase I

MASH Test 3-11 of the W-Beam Guardrail on Low-Fill Box Culvert – Phase II