SoarNewSMTH｜Shaanxi S30 Shuiyang Expressway Yanping Village No. 2 Bridge Collapse Process Speculation

According to media reports, on July 20, the No. 2 bridge of Yanping Village, S30 Shuiyang Expressway, Shangluo City, Shaanxi Province, was impacted by flash floods, causing partial collapse of the bridge holes. Let’s take a look.

1. Overview and Incident Location

The S30 Zhashui-Shangyang Expressway starts from Xialiang Town, Zhashui County, Shangluo City, and ends at Chengguan Town, Shangyang County. It was completed and opened to traffic on December 19, 2018. The incident occurred at Yanping Village, Xingping Town, Zhashui County. The No. 2 bridge of Yanping Village crosses the Jinqian River, and the collapsed part is located at a 4 * 20m span.

2. Collapse Phenomenon

3. Conjecture of the Collapse Process

When the flood is large, it may carry larger floating objects (such as large stones), and the speed is faster, the impact force is greater (see discussion | the second model of stones hitting bridge piers, can bullets break the bridge piers?), even if the bridge piers cannot be broken, it is enough to cause the bridge piers to deform greatly.

The beam body deforms with the bridge pier, the beam end at the expansion joint position detaches from the top of the pier, and begins to fall. During the falling process, it continues to squeeze the bridge pier to continue deformation. Since the bridge pier has not completely lost support, the position of the maximum internal force of the beam body does not appear at the top of the pier, and the section cracks there. The beam body continues to fall, and the bridge pier is broken. The beam body breaks at the crack, and the beam end falls into the water, and the beam body breaks again.

4. Some Thoughts

(1) Cross-river bridges should pay attention to the anti-collision problem of bridge piers. For navigable rivers, attention should be paid to the prevention of ship collisions and floating object impacts; for non-navigable rivers, attention should be paid to the prevention of floating object impacts.
(2) Anti-collision measures include: appropriately increasing the section size of the bridge pier and adding buffer facilities.
(3) Longitudinal anti-falling beam measures should also be added to prevent the beam end from detaching from the top of the pier when floating objects hit.