Legislative Council Question 3 : "Seismic resisting capability of buildings" by the Hon Patrick Lau and a written reply by the Secretary for Housing, Planning and Lands, Mr Michael Suen, in the Legislative Council
Following is a question by the Hon Patrick Lau and a written reply by the Secretary for Housing, Planning and Lands, Mr Michael Suen, in the Legislative Council today (February 28):
The recent earthquake in Taiwan had caused damages to buildings and underground pipelines there. Residents in Hong Kong also felt that earthquake and have expressed concern about the safety of local buildings and underground pipelines. It is learnt that the existing Buildings Ordinance (Cap. 123) does not require private buildings in Hong Kong to possess seismic resisting designs, but only requires them to withstand wind gusts of 250 kilometres per hour. It has been reported that old buildings constructed before the fifties in the last century do not even possess any wind resisting designs. It has also been reported that the new code of practise ("CoP") issued by the Buildings Department in December 2006 requires new buildings to be added with seismic resisting designs. In this connection, will the Government inform this Council:
(a) of the respective numbers of buildings which do not have seismic resisting capability, or the wind resisting capability as prescribed by law, broken down by the 18 local administrative districts;
(b) of the earthquake intensity that new buildings are able to withstand as required under the above CoP issued by the Buildings Department; and
(c) whether it has assessed the seismic resisting capability of underground pipelines (in particular gas pipes), and drawn up contingency measures to deal with any major incidents arising from large-scale gas leakages caused by earthquakes; and whether the authorities have any plans to train qualified personnel capable of carrying out inspections on the gas leakage sites concerned?
As Hong Kong is not geographically situated within active seismic belts, the possibility of having serious earthquakes in the territory is relatively low. The strongest locally felt earthquake recorded by the Hong Kong Observatory since 1905 is of Intensity VI to VII under the "Modified Mercalli Scale" (MMS). This locally felt earthquake took place in 1918 and inflicted minor damage on walls of a few buildings constructed under the prevailing building standards at that time. This has been the only earthquake that has caused damage in Hong Kong since 1905.
Replies to the three parts of the question are as follows:
(a) The extant Buildings Ordinance does not require private buildings in Hong Kong to possess seismic-resistant designs. However, as early as from the 1930s, buildings in Hong Kong had to be designed to withstand wind gusts of 130 km per hour. In the 1950s, this wind-resistance requirement was enhanced to the ability to withstand wind gusts of 250 km per hour. Wind-resistant designs help strengthen building structures and thus make such buildings possess a high load-resisting capacity. Even if an earthquake of MMS Intensity VII occurs, such buildings will still be safe and suffer no serious damage.
(b) As required by the Buildings Department since December last year, all new concrete buildings have to comply with the "Code of Practise for Structural Use of Concrete 2004". Apart from setting out requirements which improve the design of concrete structures, the Code of Practise also provides guidelines for enhancing the structural behaviour of buildings at beam-column joints. Although these guidelines are not specifically provided for the seismic resisting design of concrete buildings, they could enhance the seismic resisting capability of such buildings.
(c) As Hong Kong is not geographically situated within active seismic belts, the possibility of having serious earthquakes in the territory is relatively low. This being the case, the relevant legislation and codes of practise in Hong Kong do not specifically require that underground pipes should be seismic resistant. Nevertheless, local public underground pipes, including feed pipes, drain pipes, gas pipes, etc., are designed for Hong Kong's environment in accordance with widely recognised international standards. Gas distribution pipelines are strong enough to withstand vibrations caused by heavy vehicles and soil settlement and can therefore withstand tremors to some extent.
Regarding contingency measures for gas leakages, Towngas continuously monitors the gas distribution network through an electronic monitoring and data reception system. In case of gas leakages caused by damaged gas pipes and drastic plunges in gas pressure of the distribution network, the system will send out alarm signals. Personnel in the control room will duly turn off the shut-off valve of the main gas supply pipeline by remote control to prevent further gas leakages. Regarding liquefied petroleum gas (LPG) distribution pipelines, there are also proper safety devices and shut-off valves to prevent massive gas leakages.
In the event of emergencies, the gas supply companies will take contingency measures according to the established emergency procedures. They will also closely liaise with the Electrical and Mechanical Services Department and other government departments to tackle the incidents. In case of the occurrence of any serious incidents including earthquakes in Hong Kong, the Security Bureau will, according to the circumstances, promptly initiate the established contingency measures. It will also coordinate the command and control centres of the emergency services and support departments to carry out rescue, recovery and restoration work.
Under the existing registration system, each Registered Gas Installer and persons who are competent to manage LPG stores are required to receive training on the use of gas detectors and master the necessary skills. Hence, they will be able to locate leakage in gas leak incidents and take contingency measures promptly.
Ends/Wednesday, February 28, 2007
Issued at HKT 13:03