Heiti verkefnis : 

Multi Hazard Assessment of LongSpan Bridges in South Iceland

Verkefnastjóri : 

Rajesh Rupakhety

Stutt lýsing á verkefninu:

Bridges are a critical component of transportation infrastructure. Many highway bridges in Iceland are old and some of them single-lane. In the near future, it is expected that many of the bridges will need to be replaced. Recent development in tourism industry has placed even more pressure on an already aging transportation infrastructure in Iceland. It is expected that some long-span bridges will need to be constructed in the future. An example is the planned bridge crossing Ölfus river in Selfoss. Since some of these structures lie in the South Iceland Seismic Zone, which is seismically very active, they are expected to be affected by forward-directivity ground motion with significant low frequency energy. Near-fault ground motions dominate hazard scenario in this area (see Rupakhety et al., 2016), where local site effects further amplify ground motion in the frequency range of 1Hz, a frequency close to the fundamental frequency of many long-span bridges. The proposed project will study this problem in detail and suggest appropriate improvements in response analysis and design. Apart from seismic actions, the bridges are exposed to severe wind conditions. Combined action of wind and strong near-fault ground motions on long-span bridges has not been thoroughly investigated in the scientific literature. The originality of this project lies in a detailed investigation of this issue, identification of critical scenarios, and study of mitigation measures. The proposed project will study this problem in detail and suggest appropriate improvements in response analysis and design. Apart from seismic actions, the bridges are exposed to severe wind conditions. Combined action of wind and strong near-fault ground motions on long-span bridges has not been thoroughly investigated in the scientific literature. The originality of this project lies in a detailed investigation of this issue, identification of critical scenarios, and study of mitigation measures. The proposed project will study this problem in detail and suggest appropriate improvements in response analysis and design. Apart from seismic actions, the bridges are exposed to severe wind conditions. Combined action of wind and strong near-fault ground motions on long-span bridges has not been thoroughly investigated in the scientific literature. The originality of this project lies in a detailed investigation of this issue, identification of critical scenarios, and study of mitigation measures.

Tilgangur og markmið:

The main research questions of the proposed project are listed below. 

(i) Because long-span bridges are flexible structure, they are vulnerable to long-period and impulsive motion commonly observed near earthquake faults. The proposed research aims to understand to what extent near-fault effects are critical for the safety of such structures, and whether (and in what ways) their fragility to near-fault ground motion is significantly higher than that to ordinary ground motions.

(ii) How can the combined effect of stochastic wind and ground motion be incorporated in overall fragility analysis, and what practical implications does it have in design and analysis?

To answer these research questions, the following objectives will be pursued. 

(i)  To establish fragility functions of long-span bridges subjected to wind and near-fault ground motions.

(ii) To study the response of uncontrolled and controlled cable-stayed bridges under a set of near-fault earthquake excitations and strong wind forces.