Civil Engineering December 2022 | Vol 30 No 11

Civil Engineering December 2022 25 foundation. This requires special consideration for connec- tions of services such as water pipes, power cables, communi- cation networks and other structures which need to be linked with junctions that can allow such large movements. Q Q Unlike traditional fixed-base systems, there is a need for ad- ditional knowledge by designers, contractors and maintenance personnel on all relevant aspects of the base isolation system, its operation parameters and maintenance requirements. Examples of civil engineering structures where base isolation has proved to be beneficial include: Q Q Buildings: Due to their high center of gravity, high-rise buildings are prone to earthquake risk. However, this is not restricted to high-rise buildings; it also includes buildings that host sensitive equipment, or which are structurally vulnerable to earthquakes, such as those constructed from large shell elements. Examples of iconic buildings with base isolation in- clude the Apple Park building in the United States of America and Shinagawa Season Terrace building in Japan. Q Q Nuclear power plants (NPPs): Due to the sensitivity and high-risk nature of NPPs, extra protection is often provided to a nuclear facility by using base isolation on nuclear reactor structures so that they are sufficiently protected from po- tential earthquake damage. Built in the 1970s, Koeberg NPP, located near Cape Town, is one of the first NPPs in the world constructed with a base isolation system. Q Q Bridges: A bridge’s superstructure is often isolated from its substructures by using isolators at the interface between the two bridge elements. However, some creative designs were implemented on the South Rangitikei Rail Bridge in New Zealand in the 1970s, where base isolation devices were installed at the base of the bridge’s 75 m tall piers. Q Q Liquid storage tanks: Ground motion induces hydrodynamic forces on the stored fluid, which results in increased fluid pressures on the tank’s walls. This could result in potential environmental contamination or safety risks if such tanks should fail. To keep economical wall thicknesses of lateral walls, storage tanks, particularly where safety and environ- mental risks are high, such as with liquified natural gas, are increasingly stored in base isolated tanks to limit potential risks associated with ground movement. Q Q Railway lines: Buildings constructed near railway lines can be protected from vibrations induced by trains through the use of base isolation, which can be applied to either the railway structure or the buildings’ foundations. Base isolation is an important technical solution for dealing with the effects of ground vibrations/movements on civil infrastruc- ture. Designers are encouraged to explore base isolation as a po- tential technical solution wherever there are risks to the structure from ground vibrations. The application of base isolation does not need to be restricted to new infrastructure. Retrofitting existing buildings has proved to be highly beneficial for older structures designed using older seismic design methods which were not as stringent as the cur- rent design standards.