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EPB Methodology

The following are relevant precis of the new EPB Methodology set by the MBIE as required under subsection 133AV of The Act to illustrate the new process for Council and engineers in identifying Potentially EPB's and EPB's.

1. Territorial Authorities (Council) Identify Potentially Earthquake-prone Buildings:

1.1 Scope for identifying these buildings:

Council must identify Potentially EPB's that fall within certain categories (profile categories) specified in section 1.2 below, within the time frames specified in section 133AG of The Act: or may at any time if it suspects the building may be EPB asset out in section 1.3 below.

If Council has identified a Potentially EPB it must notify the owner and request an assessment in accordance with section 133AH of The Act.

When identifying buildings Council must consider any investigations it may have undertaken under previous EPB requirements and the information it holds about these buildings, e.g. previous assessments.

Council is not expected to identify parts of buildings when identifying Potentially EPB's. This is for the engineer to consider in the assessment process.

Council will not consider buildings which are exempt, or not of a specified category, when identifying Potentially EPB buildings.

1.2 How to identify using profile categories:

Council must identify Potentially EPB's in its area using the profiles categories as follows; -

  1. Residential buildings of 2 or more storey and that are either a hostel, boarding-house, or other specialised accommodation; or, contain 3 or more household units (refer to section 133AA (2) of The Act); or [Note: this part was added by Council to show compliance with Section 133AA(2) of The Act]
  2. that fall within the following profile categories for a high seismic risk area;

Category A - Unreinforced masonry construction (URM), i.e. buildings originally built of masonry (brick, block, stone) without apparent form of reinforcement or independent lateral support and includes strengthened URM, unless there is evidence the strengthening achieves at least 34% NBS.

Category B - Pre-1976 construction that is three storey, or 12 m, high above the lowest ground level immediately adjacent to any part of the exterior face of the building, other than URM. This category includes buildings of one or two storeys that are 12m, or more, high.

Category C - Pre-1935 construction that is one or two storeys high, other than URM.

Notes:

(a) How to apply the categories;

(i) the age of a building is the date of construction of the earliest part, not any subsequent addition or alteration.

(ii) the height of the building is the maximum vertical distance measured from ground immediately adjacent the face of the building to the roof apex perpendicular to the adjacent ground. The lowest ground level adjacent the building may not provide the maximum height of the building above the ground adjacent the building. [this is a Council variation of the explanation provided in the EPB Methodology]

(iii) evidence of a building age and construction can be obtained from plans, specifications, drawings, photos, aerial photos, Google Earth imagery or other documented evidence. Any visual inspection should confirm the evidence. [this is a Council variation of the explanation provided in the EPB Methodology]

(b) The following buildings are excluded from the profile categories;

(i) a building constructed primarily of timber framing without other construction materials providing lateral support,

(ii) a building strengthened to at least 34% NBS,

(iii) a building Council has previously notified the owner is not EPB,

(iv) a building that is subject to the provisions of Schedule 1AA of The Act,

(v) a building which meets the criteria set out in section 3.3 below,

(vi) buildings for which Council obtains information or a special study that shows a particular subset of buildings is not EPB due to particular circumstances or special local characteristics, where there is robust technical basis for this information or study.

1.3 How to identify at any time:

Council may at any time identify a building as a potentially EPB if it has reason to suspect the building may be EPB. Those reasons may include;

  • (a) Council receives an engineering assessment, or other evidence, that contains information about the building's seismic performance capability which indicates the building may be an EPB.
  • (b) Council becomes aware of issues that could affect or impact the buildings seismic performance capability, such as;
  • (i) particular construction types, which are not included in a profile Category, but which may include EPB's, e.g. a timber framed building of two or more storeys on a significant slope; or
  • (ii) complex design or construction with known conditions that require further engineering analysis, such as; non-ductile columns; no effective connection between diaphragms and primary structural elements; stairs which are seismically separated with ledge and gap supports.
  • (iii) ground conditions which could lead to a significant loss of support for primary structural elements.

2. Engineers Carry Out Assessments Of Potentially Earthquake-Prone Buildings:

When an owner receives from Council a request for the supply of an assessment, they must supply one of the following;

  • a new or previous assessment; or
  • evidence of a factual error with respect to Council's decision the building is a potentially EPB; or
  • notification that the owner will not be supplying an assessment.
    • An assessment must meet the following requirements;
    • If Council accepts a previous assessment the owner is not required to obtain a new assessment, [unless the previous assessment is too old and does not provide sufficient detail and/or information for Council to make a decision on the building's seismic performance capacity].

This section refers to Parts A, B and C of the Engineering Assessment Guidelines (EAG).

2.1 Scope for engineering assessments:

2.2 Qualification requirements:

An assessment must be overseen and signed off by an engineer with relevant skills and experience in structural and earthquake engineering, and [the creation and use of previous] assessments of existing buildings, and be able to interpret and apply the requirements and technical methods set out in the Engineering Assessment Guidelines (EAG). At a minimum, that engineer must be a structural engineer who is a Chartered Professional Engineer (CPEng).

2.3 Determining the appropriate form of assessment:

The engineer must determine whether an Initial Seismic Assessment (ISA) or Detailed Seismic Assessment (DSA), as described in the EAG is appropriate for the building, in accordance with the framework set out in the following figure.

Framework for determining the type of engineering assessment required

The EAG recommends that an ISA is carried out as the first step in a DSA.

For an ISA to be used as an assessment, and therefore as a basis for determining whether or not the UC of a building is exceeded in ME shaking, the engineer must be confident that the result reflects the building's expected seismic behaviour.

In particular the engineer must;

2.4 Technical requirements for the assessment:

An ISA must meet the requirements of Parts A and B of the EAG.

A DSA must meet the requirements of Parts A and C of the EAG.

An assessment must: -

  • include necessary inspections of the building as follows;
  • consider either the original structural design building plans and or engineering calculations; or, in lieu of plans or calculations, prepare and use appropriately justified assumptions in place of information that would have otherwise been obtained from the plans or calculations, and
  • consider parts of buildings in accordance with the scope and definitions of parts as set out in section 2.4.1 below,
  • consider whether the Potentially EPB comprises a shared structural form or shares structural elements with any other adjacent titles; and, if this is the case, consider the extent to which the low scoring elements, i.e. those scoring below 34% NBS, affect or do not affect the structure as a whole - as described in the EAG,
  • determine the UC of the building and its parts and the earthquake shaking demand to produce the % NBS,
  • for buildings less the 34% NBS, determine the mode of failure and physical consequence of the building or parts, and the nature of the significant life safety hazard and/or likely damage to other property.

2.4.1 Considering parts of buildings:

The Act refers to a building or part of a building. Therefore, an assessment of a Potentially EPB must consider parts of buildings as described below.

A building part is an individual building element that would pose a significant life safety hazard if it is able to:

A significant life safety hazard is an unavoidable danger that a number of people are exposed to.

An assessment of a Potentially EPB must consider and include parts of buildings in accordance with Part A of the EAG.

An engineer will need to exercise judgement in applying the EPB provisions to part of buildings. Whether a particular building element is considered a part of a building will depend on the individual circumstances of the building and whether a significant life safety hazard is present. The justification or reasoning for inclusion, or exclusion, of a part should be clearly reported. However, the consideration of part for the purposes of assessing Potentially EPB's is not intended to be as broad in scope as the application of the term parts' for the structural design of new buildings.

Parts of buildings likely to be a significant life safety hazard, that would be expected to be included in an assessment, are described in Part A of the EAG.

2.5 Reporting requirements:

The resulting report must be provided to Council together with a summary of the assessment in accordance with the EAG. The following information must be provided in the summary:

  • a statement of appropriate qualifications and experience (supplemented with any relevant training attendance) of the engineer overseeing and signing off the assessment, and
  • the relevant building information, and
  • a statement of confirmation that an external and internal inspection of the building was completed as part of the assessment; or, appropriate commentary where an internal inspection was not completed, and
  • a description of the engineering methodology used and key parameters; and, if the assessment is an ISA, a confirmation statement that the ISA provides a result that the engineer is confident reflects the buildings expected behaviour, and
  • sufficient details about the building and any parts that score less than 34% NBS and therefore pose a significant life safety hazard, to allow Council to evaluate the possible consequences of failure, and
  • if the building comprises a shared structural form or shares structural elements with any other adjacent titles, information about the extent to which the low scoring elements, i.e. those scoring less than 34 % NBS, affect or do not affect the structure as a whole, and
  • the % NBS for the building, and
  • for buildings with less than 34% NBS, a statement on the expected mode of failure and physical consequence of the building or part, and the nature of the significant life safety hazard and/or likely damage to other property.

The report and summary must be accompanied by all documentation considered in undertaking the assessment; or, in place of appending this documentation, a list with specific references to the documentation used. This must include the plans, drawings and calculations considered; or, in lieu of these, an appropriate justification of the assumptions used for information that would have otherwise been obtained from those documents.

3. Territorial Authorities (Council) Decide On Earthquake-Prone Buildings:

3.1 Scope for these decisions:

This methodology sets out how Council is required to determine whether a Potentially EPB is an EPB, and if it is, it's earthquake rating by specifying: -

  • in sections 3.2 and 3.3, criteria which must be met by the assessment, or a previous assessment, for Council to accept the assessment, and
  • in sections 3.4 and 3.5, how Council is to determine if the building is EPB in accordance with section 1.0 of this methodology.

[If Council is relying on a previous assessment,] before determining whether a building is EPB or not, Council should notify the owner that the building is Potentially EPB and give the owner the option to either agree with and use the previous assessment and the NBS rating it provides, or to supply Council a new assessment in accordance with Section 2.0 above.

If an owner has a previous assessment that does not meet the criteria set out in 3.3 of this methodology, an owner may commission an engineer, as defined in section 2.2 above, to revisit the assessment and address the missing criteria retrospectively. If the owner can provide supplementary evidence from the engineer that addresses the missing criteria, Council may accept the previous assessment.

If Council does not accept a previous or new assessment it should advise the owner why it is not accepted.

Under section 133AK (4) of The Act, if Council does not receive, or is notified the owner does not intend to supply, an assessment Council must proceed as if it had determined the building is EPB.

3.2 Criteria for accepting an engineering assessment:

An assessment must meet the requirements set out in section 2.0 above, including being reported in accordance with section 2.6 above.

Council must accept the assessment if these requirements are met.

If Council has concerns about whether the assessment meets the requirements set out in section 2.0 above, it may request further substantiation from the owner.

3.3 Criteria for recognising a previous assessment:

A previous assessment may be in the form of an Initial Evaluation Procedure (EIP), an Initial Seismic Assessment (ISA), a Detailed Engineering Evaluation (DEE), or a Detailed Seismic Assessment (DSA). It may be held on Council's records before 1 July 2017 or provided by an owner after 1 July 2017.

Council may accept a previous assessment if either: -

  • the assessment;
  • There is evidence that the assessment has undergone an independent review by a CPEng.
  • The assessment was undertaken as part of a programme of assessments (by either Council or owner) that was subject to a moderation process with appropriate technical input and programme oversight from a suitably qualified engineer or engineers with relevant skills in structural and earthquake engineering and in assessments of existing buildings.
  • was undertaken by a suitably qualified engineer with relevant skills in structural and earthquake engineering and assessments of existing buildings. As a minimum the engineer is expected to be a Chartered Professional Engineer (CPEng), or equivalent, i.e. Registered Engineer prior to 2002, and who held that status at the time the assessment was undertaken, and
  • contains evidence that an external and internal inspection was carried out as part of the assessment, or appropriate commentary where an internal inspection was not carried out, and
  • references the relevant Standard or Guidelines for acceptable engineering methods in effect at the time, e.g. the Assessment and Improvement of the Structural Performance of Buildings in Earthquakes Guidelines produced in June 2006 by the NZ Society for Earthquake Engineering, or a draft version of the Engineering Assessment Guidelines released for use in June or August 2016, and
  • Clearly states the assessment outcome, reported as % NBS, however

If Council has concerns about whether the assessment meet the requirement set out above, Council may request further substantiation from the owner.

3.4 Determining if a building is earthquake-prone:

If Council accepts an assessment, in accordance with this methodology, it must then determine whether or not the building is EPB in accordance with sections 133AB and 133AK of The Act.

[Section 133AB(1)(a) says a building is EPB if the assessment states the building's seismic rating is less than 34% NBS.]

Section 133AB(1)(b) says a building is EPB if;

  • access to the building is not likely to be difficult, limited or infrequent, and when that access is to an area affected by The mode of failure and physical consequence' is identified in the assessment report and is likely to cause damage to other property, or
  • there is another reason why collapse of the building or failure of the elements, identified in the assessment report would be likely to cause injury or death to a number of persons in or near the building, or damage to other property.
  • the current and possible occupancy of the building, and
  • the possible accessibility to the building, or near vicinity of the building, i.e. whether people can approach or enter, and
  • if there are any neighbouring buildings and the proximity of these, and
  • The mode of failure and physical consequence' as identified in the assessment report.

This decision should be informed by consideration of the following information;

3.5 Determining the earthquake rating:

If Council determines a building is EPB in accordance with section 3.4 above, it must assign the building an earthquake rating. This rating will be the %NBS specified in the assessment report. The NBS value will determine the earthquake rating category, as prescribed in The Building Regulations 2005, which will determine the form of the EPB Notice to be issued by Council for the building.

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