Bridge collision guardrail

Beam guardrails refer to guardrails installed on bridges. Their purpose is to prevent out-of-control vehicles from crossing the bridge. They serve the functions of preventing vehicles from breaking through, crossing over, or jumping across the bridge, as well as beautifying the bridge architecture. There are many ways to classify bridge guardrail types. In addition to the installation location, they can also be categorized based on structural features and collision resistance performance. According to the installation location, they can be divided into bridge-side guardrails, central bridge guardrails, and pedestrian lane boundary guardrails; according to structural features, they can be categorized into beam-column (metal and concrete) guardrails, reinforced concrete wall expansion guardrails, and composite guardrails; and according to collision resistance performance, they can be classified into rigid guardrails, semi-rigid guardrails, and flexible guardrails.

The selection of bridge guardrail types should initially be determined by the highway grade, considering the collision resistance level. Factors such as safety, coordination, the characteristics of the protected objects, and the site's geometric conditions should be taken into account. Then, choose the structural form based on its own structure, economy, and safety, as well as construction, maintenance, and other factors. Common types of bridge guardrails include concrete guardrails, wire rope guardrails, and guardrails with corrugated steel beams.

Whether for aesthetics or protection, this issue has been indirectly placed under a "microscope" after multiple vehicles have crashed through the guardrails and fallen into the river.

In fact, the guardrails on both sides of the bridge are more focused on pedestrian safety, while the curbs between the sidewalks and lanes serve as the main "defense line" against vehicles. On urban bridges, curbs are set at the intersections of the sidewalks and lanes. The primary function of this defense line is to intercept vehicles, preventing collisions between vehicles and pedestrians or with the bridge. The guardrails on the outer side of the bridge are mainly for protecting pedestrians and have weaker collision resistance.

Why is guardrail safety often overlooked? For a long time, bridge designers and managers in China have primarily focused on the safety of the main structure and the risk of collapse, neglecting how to ensure the safety of vehicles and pedestrians through auxiliary structures like curbs and guardrails. There's still much room for improvement here, with many detailed tasks to be addressed. In contrast, Western developed countries are more rigorous and meticulous. "They have already given careful consideration to the design of guardrails and lamp posts on bridges. For instance, if a vehicle hits a lamp post, they think about how to ensure the lamp post won't fall down and hit the car after the crash, thereby ensuring public safety."

"No bridge guardrail can prevent all accidental collisions." Guardrails have preventive and protective functions, yet there is no bridge guardrail that can withstand accidental collisions in all situations. In other words, it's difficult to estimate how much weight of vehicles at what speed would collide with guardrails to ensure no riverfall accidents occur. If large vehicles collide with guardrails at high speeds or large angles of attack (nearly vertical), the impact force may exceed the guardrail's protective capacity limits, making it challenging to guarantee that the vehicles won't be ejected from the bridge.