II. Protection Setting of Wave Beam in Central Separation Zone
1.The corrugated beam located in the central dividing zone can be divided into Am and SM according to the anti-collision grade. Sm grade guardrail is a reinforced type, and it is suitable for sections with important structures in the central dividing zone and it needs to restrict the transverse displacement of guardrail. Structurally, there are two types: Separate type and composite type. Separate guardrail is suitable for section with relatively wider central dividing zone. There are more objects in the central zone and pipelines are buried under the central partition zone. Composite guardrails is suitable for section with relatively less narrow central dividing zone. There are less objects in the central zone and pipelines are not or less buried under the central partition zone.
2.The cross-section layout of the guardrail with corrugated beam in the central partition zone should be determined according to the width and cross-section form of the central partition zone. When layout according to separate type, it is inappropriate for the guardrail surface to intrude within the limits of highway construction.
3.When the separated corrugated beam
is located in the central partition zone with curb stone, the corrugated beam guardrail should have anti-blocking blocks. Moreover, when the central partition zone is relatively tense, the minimum C value from the corrugated beam guardrail surface to the edge stone surface can be reduced to 25 cm.
4.When the composite corrugated beam is used in the central partition zone, the central line of the guardrail column should coincide with the middle line of the highway. When there are structures in the middle line of highway and underground pipelines are laid, the center line of guardrail column can be shifted to one side, or the combination type can be changed into a separate type so as to bypass the structure in the center line position.
5.Composite corrugated beam consists of pillars, diaphragms, corrugated beams and fasteners. Columns can be made of circular or grooved steel. The diaphragm beam consists of two channel steels, which are installed on both sides of the column. Both ends of the diaphragm beam are connected with corrugated beam plates respectively. The maximum combined width of the corrugated beams on both sides is 100 cm, and can be adjusted appropriately according to the width of the central dividing zone.
6.The guardrail at the starting point of the central dividing belt, the end point and the opening should be handled with ending process. The end of the separated corrugated beam shall be in line with the central separating strip. Within a certain length (e.g. 16m), the guardrail of corrugated beam gradually narrows from two parallel lines to a certain proportion in the separating zone. It is usually parabolic. The column spacing is 2 m. The radius of the round end should be in accordance with the line shape at the opening of the separating belt, generally 25 cm.