Installation of Roadside Corrugated Beam Guardrails
1. Roadside corrugated beam guardrails are classified into Class A and Class S according to their impact resistance level. Class S guardrails are reinforced and suitable for use on particularly dangerous roadside sections. The center-to-center spacing of the Class S guardrail posts is 2m.
2. The transverse layout of roadside corrugated beam guardrails should not allow the guardrail surface to encroach upon the highway construction clearance limits, and should not significantly reduce the lateral earth pressure on the outer edge of the guardrail posts. The minimum distance from the outer edge of the post to the edge of the shoulder is specified as follows: when the width of the earth shoulder is 75cm, it should not be less than 25cm; when the width of the earth shoulder is 50cm, it should not be less than 14cm.
3. End design of roadside guardrails: The starting and ending points of the roadside corrugated beam guardrails should be treated. The head can be designed as a ground anchor type or a round head type. A transition section should be provided between the upstream round head end in the opposite direction of traffic and the standard section of the guardrail. The downstream end in the same direction of traffic can be laid in a straight line with the standard section of the guardrail.
4. The anti-blocking block of the roadside corrugated beam guardrail is a load-bearing component between the corrugated beam and the post. It is suitable for road sections where the types of vehicles in the traffic flow are relatively complex, and there are concerns that colliding vehicles may get stuck at the guardrail posts; or for road sections where the curb has an adverse effect on the trajectory of colliding vehicles. Guardrail anti-blocking blocks are divided into two types: Type A and Type B. Type A is suitable for round posts.
5. Roadside guardrails should be installed in solid earth shoulders. When guardrail posts encounter soft foundations, they should be placed in concrete foundations. If possible, replaceable guardrail posts should be used.
Installation of Corrugated Beam Guardrails in the Central Median
1. Corrugated beam guardrails installed in the central median are classified into Am and Sm levels according to their impact resistance rating. Sm level guardrails are reinforced and suitable for areas with important structures within the central median. For road sections where lateral displacement of the guardrail needs to be restricted, there are two structural types: separate and combined. Separate guardrails are suitable for road sections with relatively wide medians, numerous objects within the median, and buried pipelines beneath it. Combined guardrails are suitable for road sections with narrower medians, fewer structures within the median, or fewer buried pipelines.
2. The transverse layout of the corrugated beam guardrail for the median should be determined based on the width and cross-sectional shape of the median. When using a separate layout, the guardrail surface should not encroach upon the public space. Within the road construction clearance limits.
3. When separate guardrails are installed in the median strip with curbs, the corrugated beam guardrails should have anti-blocking blocks. Furthermore, when the placement within the median strip is limited, the minimum C-value from the corrugated beam guardrail surface to the curb surface can be reduced to 25cm.
4. When combined corrugated beam guardrails are used in the median strip, the centerline of the guardrail posts coincides with the road centerline. When there are structures or underground pipelines within the road centerline, the centerline of the guardrail posts can be shifted to one side, or the combined type can be changed to separate guardrails.
5. The combined corrugated beam guardrail consists of posts, horizontal beams, corrugated beams, and fasteners. The posts can be made of round or channel steel. The horizontal beams consist of two channel steels, installed on either side of the posts. Both ends of the horizontal beams are connected to the corrugated beam panels. The maximum combined width of the two corrugated beams is 100cm, which can be adjusted according to the width of the central divider.
6. Guardrails installed at the beginning, end, and openings of the central divider should have end treatment. For separately installed corrugated beam guardrails, the ends should be consistent with the alignment of the central divider. Within a certain length (e.g., 16m), the corrugated beam guardrail gradually narrows inwards from two parallel lines towards the divider, generally in a parabolic shape. The post spacing is 2m, and the radius of the rounded ends should be consistent with the alignment of the divider openings, generally 25cm.
The combined corrugated beam guardrail consists of posts, horizontal beams, corrugated beams, and fasteners. The posts can be made of round or channel steel, installed on either side of the posts. Third, the guardrails in the triangular area at traffic divergence points should be constructed in the same way as the roadside corrugated beam guardrails and should be laid out according to the alignment and topography of the triangular area. The minimum length for installation is as follows: reinforced (Class S) guardrails should be used within 8 meters of both ends on the side closest to the highway mainline and within 8 meters of both ends on the side closest to the ramp. Six spans of Class A guardrails should be installed between the reinforced guardrails, and the guardrails on both sides of the triangular area should be connected with rounded ends. Crash pads should be installed within the danger triangle area.
The center height of the crossbeam of the corrugated beam guardrail, measured from the road surface, is 60cm from the center of the connecting bolt holes. When a curb is present, the center height of the crossbeam, measured from the top surface of the curb, is also 60cm from the center of the connecting bolt holes. When the corrugated beam guardrail has anti-blocking blocks, its center height remains unchanged. The posts of the corrugated beam guardrail are generally buried in the soil foundation, and the burial depth is specified as follows:
1. When the guardrail post is buried in the soil and there is no curb, the burial depth should not be less than 110cm.
2. When the guardrail post is buried in the soil and there is a curb, the burial depth should not be less than 125cm. When a combined corrugated beam guardrail is used in the central median strip, the embedment depth of the posts should not be less than 110cm.
Secondly, the concrete foundation embedment method can be used for guardrail posts in the following situations:
1. Posts are placed in locations where driving is impossible, such as bridges, passageways, or culverts.
2. There are underground pipelines or rocky road sections below the posts.
3. Other special circumstances.
The embedment depth of the posts in concrete should generally not be less than 40cm. For ease of maintenance, a flange assembly connection method can be used. The dimensions of the concrete foundation and the connection strength of the flanges should be determined by calculation according to different situations. When conditions permit, replaceable guardrail posts should be used.