Natural gas is a vital commodity 和 accounts for about a third of the United States’ total energy production. 在天然气生产之后, it is liquified at extremely low temperatures (-260 °F) 和 shipped via tanker to U.S. 终端. 一旦进入美国.S., this Liquefied Natural Gas (LNG) is distributed all over the country to local industrial facilities or gas plants where it is stored in tanks so that it may be vaporized 和 used whenever energy is needed.
去年，一个 series of earthquakes in Ridgecrest, CA 造成了超过十亿美元的损失. Highways cracked, chimneys fell, 和 storage tanks were damaged. While not often reported, earthquakes present a major hazard to 液化天然气储罐. Shifting of the tank 和 connections due to an earthquake could cause gas leakage 和 insulation loss, 皇家88账户注册可能会导致 重大爆炸和灾难.
No matter where LNG tanks are located within the U.S., it is important that they are seismically designed, which is required by federal regulation. In fact, all large tanks, even if they don’t contain 有害物质, are considered “nonbuilding structures” by the 建筑规范 需要抗震设计.
地震科学
An earthquake occurs when two tectonic plates slip past one another, releasing an enormous amount of energy. 实际上是6级.0 earthquake releases the energy equivalent of an 原子弹. This enormous energy creates waves that travel within the earth 和 along its surface. 当皇家88账户注册些波浪移动时，它们:
- Weaken (attenuate), similar to the rippling of waves caused by throwing a pebble in a pond
- Amplify as they reflect 和 refract off different soil layers
Because seismic waves can both weaken 和 amplify as they travel, determining the earthquake motions at a site is a complicated task. A seismic engineer needs two things to determine this motion:
- 工地的地理位置(一).e. 与已知故障的距离)
- Soil conditions underneath the site (usually determined by a geotechnical engineer)
The first step in seismic design is determining this motion. 对于标准建筑来说, a structural engineer would use design maps 和 average soil properties to determine the potential earthquake motion at the site. This is a quick method that usually yields conservative results. However, for important items, such as 液化天然气储罐, a more comprehensive analysis is required.
What is a Site-Specific Response Analysis?
A site-specific response analysis (SSRA) is a more comprehensive way to determine the earthquake motion at site's ground surface 和 requires a specialized skillset 和 software. Some examples of structures for which SSRAs are required include:
- 液化天然气储罐
- 核电站
- 软粘土结构
SSRA需要两个步骤:
- Determine the motion at the bedrock below the site. This is commonly referred to as the site’s seismic hazard 和 is determined based on probabilities 和 history of past nearby earthquakes.
- Calculate the motion at the ground level by modelling the waves reflecting 和 refracting through the soil layers. This is typically performed with special software.
Last year’s earthquakes at Ridgecrest demonstrate the importance of making our infrastructure seismically resilient. 皇家88娱乐高度专业化 结构/地震安全小组 has the required skillset to ensure the design of LNG tanks meet the strict federal regulations 和 are seismically safe.