The Zijin Bridge
On the fateful day of June 14, 2019 at 2:12 am, a couple of sedan cars were passing sequentially over the bridge — Zijin. Suddenly, the column near the span 3 started buckling as soon as first car reached the center of the pier3.
Being a symbol of Heyuan City, China, Zijin bridge has been operational since 1972 with the life expectancy of 100 years. Constructed across the Dongjiang River from northwest to southeast to connect the Hezi road, it was the second river-crossing bridge of the city.
A beautiful, 9 meter wide arch bridge that ran 420 meter across the river, suffered a slight dislocation at the west abutment in 2007. Several small cracks in the central arch ring raised the alarm that led to the traffic restrictions on it. In due course of time, unable to manage the local vehicle congestion, the restriction was lifted in 2011. The traffic volume then continued to increase annually and reached the volume of 7000 vehicles a day. Meanwhile the bridge underwent a significant maintenance in 2015.
A heavy downpour resulted in a severe flooding at several locations, in the months of May and June, 2019. Fengshuba Reservoir was discharged and the river turned turbulent. On June 14, 2019 all hell broke loose…
At 2:12:19 a.m…
The first sedan reached the pier 3 while the car behind it, was at the middle of the span 2. The first plastic deformation began at the span 3 near pier 2 (red circled). The deformation occurred at the right hand side of the traffic direction. The deck (/road) near pier 2 sank slightly.
At 2:12:20 a.m…
The second plastic deformation started at the end of span 3 before pier 3 and it had become a non-statically indeterminate structure (loosely meaning, unpredictable). At that juncture, the second car reached the middle of the span 3 while the front vehicle was passing the middle of the span 4. The major plastic deformation occurred at the middle of the span 3 due to the vehicle load and the car started sinking along with the span 3.
At 2:12:22 a.m…
The story was not over. Next, a new plastic deformation occured in the middle of the span 4 due to the vehicle load and pier 3 had no support in the direction of the span 3. In addition to the sinking of the middle span, new plastic deformations appeared on both sides of span 4. With this collapsed the span 4 along with the car.
At 2:12:23 a.m…
The Pier 3 column fell in the direction of span 3 notwithstanding the force from the falling span 4 and eventually crumbled into the water.
What caused all these…?
THE ILLEGAL SAND MINING…!
The collapse was triggered by the arch foot of pier 2 that weakened the pier 3. The weak pier 3 initiated the chain reaction that pulled down the spans 3 & 4. The long-term illegal sand extraction might have emptied the river sand, downstream of the pier, leading to the displacement of the pier(s). As a result the pier(s) started inclining over a period of time.
As shown in the image, the inclination is at the right side of the traffic direction and the first crack appeared at the same side that triggered the collapse of the bridge that should have stood proud for the next 50 years.
Source of Information & Images: “Lessons Learnt from Bridge Collapse: A View of Sustainable Management”, February 2020, Sustainability 12(3):1205 DOI 10.3390/su12031205