How Earthquake Base Isolation Protects Buildings

A

Earthquakes send energy through the ground as waves. When a building rests directly on a rigid foundation, some of that motion travels upward into its columns, floors, and contents. Damage can result not only from a structure collapsing but also from furniture overturning and equipment moving suddenly. Engineers therefore use different methods to limit how much ground motion reaches a building. One method, called base isolation, allows the ground and the building above to move somewhat independently. It does not prevent an earthquake or make a structure immune to every hazard. Instead, it aims to reduce the strong horizontal accelerations transmitted from the foundation to the occupied floors.

地震以波的形式通过地面传递能量。当一栋建筑直接坐落在刚性地基上时，一部分运动会向上传到它的柱子、楼板和室内物品上。损害不仅可能来自结构倒塌，也可能来自家具翻倒和设备突然移动。因此，工程师采用不同的方法来限制传到建筑上的地面运动。其中一种方法叫作基础隔震，它允许地面和上方的建筑在一定程度上各自独立地运动。它不能阻止地震，也不能让建筑免受所有危害。它的目的是减少从地基传到有人使用的楼层上的强烈水平加速度。

B

A common isolation device consists of layers of rubber and steel. The rubber permits controlled horizontal deformation, while thin steel sheets reinforce the assembly so it can carry the building’s vertical weight. Some bearings contain a lead core that helps dissipate movement energy. Other systems use sliding surfaces designed to move within a limited range. In each case, the building must be designed to accommodate a gap around its base: if it hits a surrounding wall during a major earthquake, much of the benefit can be lost. Flexible connections are also required for pipes, cables, and other services crossing between the moving building and the stationary ground.

一种常见的隔震装置由橡胶层和钢板层组成。橡胶允许受控的水平变形，而薄钢板则加固整个组件，使它能够承受建筑的竖向重量。有些支座含有铅芯，有助于消耗运动能量。另一些系统则使用设计成在有限范围内移动的滑动面。无论哪种情况，建筑在设计时都必须在底部周围留出间隙：如果在大地震中建筑撞上了周围的墙，大部分好处就可能丧失。对于横跨在运动的建筑与静止的地面之间的管道、电缆和其他设施，也需要使用柔性连接。

C

Isolation systems are not suitable for every project. A very tall building may respond to earthquake forces differently from a low or medium-height structure, so designers must study its natural period of vibration and the expected ground conditions. Soft soil can amplify some types of shaking, and sites close to a fault may experience rapid ground movements that demand unusual travel distances. Engineers use simulated earthquake records and physical tests to judge whether the isolators have adequate movement capacity. In existing buildings, installation can require temporary supports so workers can place the bearings beneath structural columns. This complex retrofit may be worthwhile for hospitals or emergency centres where operation after an earthquake is especially important.

隔震系统并不适用于每一个项目。一栋非常高的建筑对地震力的反应可能不同于低层或中等高度的建筑，因此设计者必须研究它的自振周期和预期的场地条件。软土可能会放大某些类型的震动，而靠近断层的场地可能会出现快速的地面运动，需要异常大的位移量。工程师利用模拟地震记录和实物测试来判断隔震装置是否有足够的位移能力。在既有建筑中，安装时可能需要设置临时支撑，以便工人把支座放到结构柱的下方。对于医院或应急中心这类震后尤其需要继续运作的建筑来说，这种复杂的加固改造可能是值得的。

D

After installation, isolation bearings need regular inspection and maintenance. Workers look for damage, corrosion, obstacles within the movement gap, and changes that might restrict sliding or rubber deformation. Replacing a bearing can be a specialized operation, so access for future maintenance should be included in the original design. Engineers also consider non-earthquake loads, such as strong winds, to make sure a system responds appropriately under ordinary conditions. The purpose is resilience rather than a guarantee of zero damage: a well-designed isolated building may still need repairs after an unusually severe event. Continued performance depends on engineering design, construction quality, and the condition of its isolation components over time.

安装之后，隔震支座需要定期检查和维护。工作人员会检查是否有损坏、腐蚀，位移间隙内是否有障碍物，以及是否出现可能限制滑动或橡胶变形的变化。更换支座可能是一项专业性很强的作业，因此在最初的设计中就应考虑日后维护的通道。工程师还会考虑地震以外的荷载，比如强风，以确保系统在平常条件下也能作出适当的响应。目标是增强抗灾韧性，而不是保证零损害：一栋设计良好的隔震建筑在遭遇异常强烈的地震后，仍然可能需要维修。它能否持续发挥作用，取决于工程设计、施工质量以及隔震部件长期的状况。

Reading Test 049

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