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Structure Repair: BS EN 1504 vs. ACI 562 (2019)

posted Sep 6, 2021, 8:01 AM by jeffery jim
1. Structure repair simplistically refers to works that involved when repair, rehabilitate and/or rejuvenate structures or buildings that may have lapse its serviceability limits and may endangered inhabitants, occupants or adjacent properties to possibilities from risks and hazards arise from possible ultimate limit state.

2. Normally, structures which were designed to be permanent and should be able to remain in both limit states for a period of at least 50 years for Category 4. This is called the design lifespan. Monumental structures and bridges are under Category 5 and required to last for at least 100 years.

3. Structures have issues with lifespan and it is not related to engineering but material science where durability have been the core issues. As I have wrote in many articles previously, the shift of British Standard such as BS8110 Part 1:1985 until 1997 revision have seen many changes involving changes in durability. These render the progression of two supplementary documents such as BS5328 and BS EN 206 with the addition of BS 8500 as secondary key supplementary dossier. In 2004, Eurocode 2 or BS EN 1992 have replaced BS8110 as the standard for structural design for many part of Europe and have been adopted by Malaysia with with own annexed which is much stringent in requirements. This introduction also supersedes Malaysia's very own MS1995:1991 as it co-exists and mutually reflective (verbatim in my opinion) of BS 8110:1985. For most JKR project specification, the introduction of these supplementary dossiers have led to the newer revision for Standard Specification for Building Work 2005 with extensive addendum in 2014 revision.

4. Structural repair and prolongation/extension of structure lifespan of buildings and structures is relatively new in Malaysia. The design for a proper method in repair have been dynamic ever since where repair methods have not seen any proper standard provided by JKR Cawangan Kejuruteran Awam dan Struktur (CKAS) or Civil and Structural Branch and guidance provided for their Bahagian Kejuruteraan Forensic (BKF) or Forensic Engineering Department. Typical drawings have been used and disseminated where most consultants adopted their design methods and drawings. In many instances, the method proposed (may) not be suitable and in compliance with BS EN 1504.

5. BS EN 1504 is a European standard which speaks about product and systems for the protection and repair of concrete structures. It is never been a foolproof system which provides the right solution and application for each type of defect. Conventionally, JKR and/or consulting engineer(s) will conduct a survey based on visual inspection and reconnaissance works at site to look for telltale signs and assisted with limited testing. This shall be the basis for proposed structural repair but more often it becomes the basis for costing. The drawbacks here are the inconsistency if not false diagnosis which leads to wrong prognosis in tackling problems as well as procedures for the right method and/or principal based on BS EN 1504.

6. The issue with BS EN 1504 series with 10 parts have no specific information to guide professionals in determining diagnosis and prognosis. This series of specification only highlights the system requirements as per its own standard specification title. This cause many issues as many engineers have no direct access or ignorantly did not abide by normative references as suggested. This have major impact in guiding engineers in making the right prognosis.

7. ACI 562 (2019) is an American code which includes the assessment methods which highlight engineering details on superficial level to guide professionals in determining the right approach to evaluate and analysis. This particular standard covers more on the overall coverage for professionals to discharge their duties diligently but then again, what can a specification with content less than a 100 pages can do?

8. Both standard specifications have major impediments as a sole reference. BS EN 1504 speaks in detail about product to be used and compliance for certification for the use in Europe and suggestions for material to be use in the tropics. That is what the standard specification have thoroughly mentioned. ACI 562 on the other hand is a summary of information which also make some normative references as guidance which requires additional read and ACI 562 should be read in the light of these normative references.

9. As a professional engineer and a professional member for material institute, the issue of proper diagnosis and prognosis of the building and/or structural condition should go beyond these two standards. Hence, none of both are superior than the other. I reckon both as standard bases to start a good assumption for possible prognosis structural repair works. Nevertheless, these are least substantial when discussing about the completeness for discharging duties diligently and professionally.

10. Concrete is a material which is known as a hybrid or a matrix which involves a lot of binders and components which may lead to many issues in regard to durability. One have to be a geologist to understand the properties of aggregates and minerals, and their chemical stability when induced by other constituents. Apart from that, one have to be a good material scientist to unravel mysteries during diagnosis and probe deeper to understand the science behind such dilapidation, delamination or even degradation of a structure and/or its components. In addition to these, one must be a civil and structural engineer in order to have the fundamental grasp on design function and criteria. It is an inter-disciplinary field where every information is substantial in providing a thoroughgoing assessment and summation processes.

11. Continuous learning and exposure in both hands-on construction and experience in design office may lend a handful help but it is the way forward to really understand the issues in regards to concrete structure or building failure.

12. I hope this clarifies my standing when discussing about both standard specifications. Personally, I do not like parsimonious explanations which relate a defect type straight to a solution. It is wrong and it is not appropriate when you are holding the badge as a professional and at the same time in an engineering predicament.