Multi-level designing structures in tsunami-prone areas
Ottosha B. Sabirova
engineer, Emperor Alexander I St. Petersburg state transport university, "Industrial and civil construction" department. Russian Federation, St. Petersburg
Rubric: Design, building and reconstruction of a seismic constructions
Key words: Multi-level design, combination coefficients, wave splash height, tsunami hazard, bridge categories
The paper proposes a two-level approach to the calculation of structures for the tsunami effect. The concept of the design tsunami and the maximum design tsunami and their corresponding limit states is introduced. The estimated loads on the bridge piers from the design and maximum design tsunami are estimated, depending on the territory danger and the bridge responsibility. At the same time, bridges, in accordance with the approach adopted in transport construction, are divided according to their degree of responsibility into four categories. A formula is obtained to estimate the design splash value for the design and maximum design tsunami, depending on the bridge category. In addition, graphs are provided showing the frequency of the tsunami and the calculated wave height corresponding to this frequency. To estimate the combination coefficient of wind and tsunami loads, their equally probable pairs are considered. At the same time, the Weibull distribution is used to set the wind load, and for the tsunami load, the distribution given in the Code of Rules for Ensuring Tsunami Safety is used. Taking into account such load pairs is relevant for bridges with high piers, when the height of the splash does not exceed the pier height and there is a high probability of a simultaneous combination of wind and tsunami loads. The paper presents the calculations of surges for two types of tsunamis: the design one with a repeatability of once in 50 years and the maximum design one with a repeatability of once in 500 years for the Kamchatka region and the Kuril Islands for bridges of the first and second categories. Studies show that for the design tsunami and the maximum design tsunami, the coefficients of combinations with wind load differ significantly.
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