Consultations on a Performance Based Building Control in Hong Kong

[updated on Feb 25, 2019, adding the last paragraph and references]

So far Building Control in Hong Kong is still mostly prescriptive in nature, even though there have been several amendments of either the regulations or the practice notes to introduce performance based approaches in the past decades. For example, performance based fire safety designs are nowadays common in the industry.

Next Tuesday (26 Feb 2019), However, Buildings Department will table a paper [1] to the Legislative Council for implementing a performance based building control system, especially for Building (Construction) Regulations (B(C)R) which are more about construction materials and processes. You are urged to give your comments either directly to the government or to legislative councillors before next Tuesday.

For example, in Part 2 about Materials, "The extant prescriptive requirements for materials namely cement, sand, water, materials for damp proofing, chunam, aggregate, admixtures, reinforcement, prestressing tendons and concrete under the extant B(C)R will be transformed into new performance-based provisions, with the added requirement that the suitability and performance of materials must be verified by recognised tests." [1](emphasis added)

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For example, with the recent incident of broken prestressing tendons on the Shenzhen Bay Bridge, one of the alleged causes is the insufficient corrosion protection on the prestressing tendons [2]. It is also confirmed by comparing the 1992 with the 2006 edition of the CEDD (2019) General Specifications of Civil Engineering Works that corrosive protection is one of the major revisions in Chapter 17 about Prestressing [3] as follows:

“17.06 Prestressing tendons : (4) Grease for unbonded strand shall contain a corrosion inhibitor. Amd 1/2010”

“17.11 Particulars of prestressing systems: (f) Details of corrosion protection required for the prestressing system, [including type of grease for unbonded strand and the type of corrosion inhibitor to be adopted, and Amd 1/2010]”

“17.28 Storage of materials for prestressing systems: (2) Prestressing tendons and sheaths shall be stored in a dry and weatherproof store and in a manner that will not result in damage or deformation to the materials or in contamination of the materials.”

It may reflect that if the prescriptive specifications do not specify the requirements explicitly, then the construction industry would not do it properly, let alone if the requirements are not set out by regulations. Whether a performance based building control would help improve the situation, or worsen it? Can the problems be solved by specifying the performance requirements on corrosive prevention?

Another example may be related to the recent scandal of the works at the Hung Hum Station of the Shatin-Central Link Railway (HHS). Building Department proposes in paragraph 12 that “This part will set out the requirements that the structure of any building, street, building works and street works must fulfill the performance-based requirements for its strength as well as its serviceability. The structure must be capable of safely sustaining and transmitting to the ground the loads it has taken up in such a manner so as not to render inadequate the factor of safety of itself or the adjoining structures.” [1] (emphasis added)

In the HHS case, however, the contractor was found to have changed the design of the works substantially without prior approval of the Building Authority, according to a news report [4].

“According to a Non-Conformity Letter sent from Building Department to Highways Department in May 2015, the design changes were found to be not in compliance with Buildings Ordinance. The Building Authority raised the concerns on the contractor’s actions of covering up the major revision, and the structural safety and serviceability issues.” [5]

However, the contractor and some experts during the Investigation Committee’s hearings, defended that the changes are just overspecifications and are thus even better than the original design, so it is not required to be prior approved [6]

If the argument is true, then it reflects that the current prescriptive requirements on structural designs are not well understood in the industry. The contractors and consultants may not have the same understanding on what is a “substantial” change that requires prior approval of the Building Authority. Can overspecifications be acceptable to be exempted from prior approval when a performance based building control is implemented? Would a performance based approach allows the contractors and consultants to change the design more easily and frequently without caring about prior approval, provided that certain performance requirements can be satisfied in the changed designs? Yet, the experts emphasized only on structural safety without discussing on serviceability about the changes of the design.

Would a performance based building control helps prevent similar incidents would be of utmost importance to the construction industry in Hong Kong as the HHS has undermined the public confidence on the professionals and contractors of the construction industry in Hong Kong. It may be timely to debate the amendments from the prescriptive building control system to a more performance based building control system at the time when there are many irregular cases in the industry.

In fact, according to our previous study many building officials were unfamiliar with the techniques and models required for an evaluation of a performance based fire engineering design [7]. Furthermore, performance based approach would incur much higher building control cost and maintenance cost as any minor changes would have to be re-evaluated by carrying out a complete re-simulation due to the “emergent” characteristics of performance based design [8].

References

[1] Legco (2019) Proposed Amendments to the Building (Construction) Regulations, and the Building (Minor Works) Regulation, CB(1)593/18–19(04). https://www.legco.gov.hk/yr18-19/english/panels/dev/papers/dev20190226cb1-593-4-e.pdf

[2] SCMP (2019) Snapped cable on cross-border Shenzhen Bay Bridge results in closure of two lanes but Hong Kong’s highways chief says there are no structural safety issues, Feb 16. https://sg.news.yahoo.com/snapped-cable-cross-border-shenzhen-100715031.html

[3] CEDD (2006) General Specification for Civil Engineering Works, 2006 Edition. https://www.cedd.gov.hk/eng/publications/standards_handbooks_cost/index.html

[4] Apple Daily 蘋果日報 (2018) 屋宇署轟禮頓隱瞞刪鋼筋 憂結構安全,10月20日 (Chinese)。https://hk.news.appledaily.com/local/realtime/article/20181019/58813950

[5] Yiu, C.Y. 姚松炎 (2018) 沙中線紅磡站連續牆削牆事件疑問,Oct 20。(Chinese) https://vocus.cc/@ecyY/5bca85d9fd8978000150fbf9

[6] Yiu, C.Y. 姚松炎 (2019) 沙中線紅磡站聆訊中部份專家揭發過度設計,Jan 22。(Chinese) https://vocus.cc/@ecyY/5c47275dfd89780001ce422d

[7] Ho, D.C.W., Lo, S.M., Yiu, C.Y., Cheng, W.Y. and To, M.Y. To (2002) Building Officials’ Perception on the Use of Performance Based Fire Engineering Approach in Building Design — a Second Stage Study, International Journal on Engineering Performance-Based Fire Codes 4(4), 119–126.

[8] Yiu, C.Y. (2008) The Emergence of a Performance-Based Building Control System, Contractual and Regulatory Innovations in Building and Real Estate, p. 95–106. Hong Kong: Pace Publishing.

Written by

ecyY is the Founder of Real Estate Development and Building Research & Information Centre REDBRIC

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