Angles in Guardrail Construction
Steel angles are the standard members for road guardrail systems: they form the posts that anchor the rail into the ground, the brackets that hold the rail, and the diagonal braces that stiffen the assembly. The L-section resists the horizontal impact of vehicles and the lateral loads of wind, and its flat legs make bolted connections simple.
Guardrail angles are usually painted or galvanized, because roadside service is fully exposed to weather, de-icing salt and stone impact.
Grade Comparison
Guardrail angles are supplied in any of the following grades, which are equivalent for this duty:
Q235 per GB/T 700: minimum yield 235 MPa, the standard Chinese road grade.
SS400 per JIS G3101: minimum tensile 400 MPa, the common Asian trade grade.
A36 per ASTM A36: minimum yield 250 MPa, the US standard grade.
S235JR per EN 10025-2: minimum yield 235 MPa, the European standard grade.
S355JR per EN 10025-2: minimum yield 355 MPa, for higher impact resistance where posts are spaced wider.
Typical Sizes
Guardrail posts commonly use angles of 75 x 75 x 6 mm to 100 x 100 x 10 mm, and brackets use smaller angles of 50 x 50 x 5 mm. Posts are supplied with punched holes for the rail bolts and a bevelled top to shed water. Standard lengths of 2 m to 3 m are typical for posts, with 6 m bars for continuous rails.
Corrosion Protection
Hot dip galvanizing is the most common protection for guardrails, with coating weights of 450 to 600 g per square metre giving decades of life. Alternatively, powder coating or a two-coat paint system is used where colour is required. The zinc coating must be repaired at drilled holes and welds after installation.
Installation Practice
Posts are driven or set in concrete foundations at the spacing defined by the design, and the rails are bolted through the pre-punched holes. Brackets allow vertical adjustment to follow the road profile. All connections use galvanized bolts and nuts to match the protected members.
Frequently Asked Questions
Q: Which grade is required for highway guardrails?
Most specifications accept Q235 or SS400 for standard duty, and S355JR where the design calls for higher impact capacity.
Q: What is the typical post size?
Posts are usually 75 x 75 x 6 mm to 100 x 100 x 10 mm angles, depending on the rail system and spacing.
Q: Why are guardrail angles galvanized?
Roadside exposure to rain, salt and abrasion makes zinc coating the most economical way to guarantee long service life.
Q: Can angles be supplied with pre-punched holes?
Yes, posts and brackets are delivered with holes punched to the system drawing.
Q: How are the angles connected to the ground?
Posts are driven directly or set into concrete, and in rock conditions they are anchored with plates and bolts.