Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Seismic Response Analysis for Three-pylon Cable-stayed Bridge Under Foundation Scour
Yihua Cai1, Huaimao Yang2, Jiali Zeng3
1

Guangdong Provincial Highway Construction Corporation，Guangzhou，China.

2 CCCC Highway Bridges National Engineering Research Centre CO., Ltd.，Beijing, China.
3 Huangmaohai Link Ad-ministration Centre，Zhuhai，China.

ABSTRACTEngineering Hydrological Survey and Design Code" stipulates thegeneral scour calculation formula of the bridge foundation. Chen andLi.(2019) predicted the general scour of the bridge after the change ofwater and sediment in the lower reaches of the Yangtze River, and theresults are closer to the actual measurement. Ye and Zhang (2007)
conducted a preliminary exploratory study on the influence of changes
in riverbed scour depth on the seismic response of large piled bridges,
and the results showed that changes in riverbed scour depth had a great
impact on the seismic response of large piled bridges, with the increasein scour depth , the seismic response of the bridge structure is not
monotonously decreasing, but a peak may appear. Yang and Ma (2015)
studied the effect of scour on the seismic response of long-span selfanchored suspension bridge pylons, and provided a reference for theseismic design of such bridges under scour conditions. Liang and Liu(2017) used probabilistic seismic demand analysis methods to establish
seismic vulnerability models of bridge pile foundations under different
scour depths. The results showed that with the increase of scour depth,
the failure probability of bridge pile foundations under earthquake
increased significantly. Li and Gong (2019) studied the influence of
pile foundation scour on the seismic response of offshore long-spancable-stayed bridges, the adverse effect of scour on the bridge increases
with the increase in the intensity of ground motions, the local scour ofthe pile foundation will further aggravate the danger of the bridge under
the action of earthquake. Chen (2019) took the PC cable-stayed bridgeas the research object, and showed that scour has a certain influence on
the seismic response of the key section bending moment of the mainpylon. None of the above studies involved the three- pylon cable-stayed
bridge.

Taking the long-span three-pylon cable-stayed bridge with the main
span of 720m in the sea-crossing project as the object, the influence ofthe different scour depths on the seismic responses of the structure wasanalyzed. The research shows that with the increase of the scour depth,
the overall stiffness of the structure and the frequency of the main modeshape gradually decrease, but the change is small; the scour of pilefoundation has the greatest impact on the force of the pile foundation,and has a greater impact on the internal force of the bottom of pylon;
The pile foundation scour depth has different influence rules on
different parts of the structure, and the seismic effect does notnecessarily increase with the increase of scour depth.

KEY WORDS: three-pylon cable-stayed bridge; earthquake;scour; seismic response.
INTRODUCTION
The bridge foundation is directly affected by water scour. Scour leads
to the exposure of the foundation of the bridge pier or the reduction of
the soil covering, which leads to weakening of the restriction of the soilon the structure. This will lead to a reduction in structural rigidity,
which will definitely affect the dynamic characteristics and seismic
capacity of the bridge structure, especially for flexible structures like
cable bridge. The scour disease of the basic structure is one of the mostimportant reasons for the failure of the function of the bridge structure
and the loss of its safety performance. From 1966 to 2005, thecollapsed bridges in the United States caused by the scour of the bridge
infrastructure accounted for 60% of the total collapsed bridges(Kattelland Eriksson,1998),and the scour has made a quarter of the bridges inthe United States unsafe. In the coastal waters of my country, the scourof the foundation of cross-sea bridges is one of the important factors
affecting the safety of the bridge (Yang, Zhang and Li, 2021).
Therefore, it is particularly important to study the seismic performanceof structures under the combined action of scour and earthquake.

BRIDGE PROFILE AND SEISMIC LOADS
Calculation model
The Huangmaohai Bridge is the three-pylon cable-stayed bridge withthe largest main span in the world. The Huangmaohai Bridge has alarge span, relatively small stiffness, and low damping. The earthquakeand other dynamic catastrophes faced cannot be ignored, and the scour
depth has a direct impact bridge stiffness, its reasonable value has asignificant impact on the dynamic effect of the bridge. This paper takes
Huangmaohai Bridge as the research object, establishes a full bridge

The general scour depth is usually less than the local scour depth.
Melville and Coleman (2000) believe that the general scour depth is
only about 10% of the local scour depth. China's "Highway706