Industrial Sponsorship

Dynamic Performance Investigation of Base Isolated Structures

By Ather K. Sharif

10.1 Standards Process - General Principles

A standard is a technical specification or other document available to the public. It is drawn up with the consensus of all interested parties affected by it, based upon consolidated results of science, technology and experience. It is aimed at the promotion of community benefits, and is approved by a body recognised at national (BSI), regional (CEN) or international (ISO) level. The British Standards Institute (BSI) was founded in 1901 (under a different name), being the first national standards body in the world. International Standards Organisation (ISO) was founded in 1947 and the European Committee for Standardisation (CEN) was founded in 1961. There are many other national and regional standards organisations (see BS 0 Part 1:1981). The standards organisations often provide secretarial support to the expert committees charged with the drafting of standards, and they co-ordinate and project manage this work to final production. The standards process gives solutions for repetitive applications, aimed at promoting consistent quality and economic production, making communication/ exchange of products and services easier.

The basic principles in the development of a standard are as follows:

Standards should be wanted (This relies on willingness by interested parties to reach voluntary agreement.)

Standards should be used (The publication of a standard is clearly of little value if it is not referred to.)

Standards should be planned (The benefits of a standard should be assessed in relation to the cost of preparation and maintenance, along with the time scale for their adequate development to deal with a current demand. In a rapidly changing field, a balance should be struck between the risk of inhibiting innovation and the spread of divergent and incompatible views. Standards should be reviewed at regular intervals, to avoid them becoming irrelevant or inhibiting progress.)

Standards should not be duplicated (The standards process can be pursued at different levels. A standard should logically be prepared at the broadest level, consistent with the needs of meeting the demands of the interested people in a reasonable time scale. The preparation of standards for identical subjects at different levels should be avoided.)

10.2 Development of a British Standard

A British Standard is developed by a committee of experts, invited from trade associations, professional institutions, research organisations, government departments, certification bodies or consumers with a relevant interest. Individual experts can also be co-opted by the technical committees. When a technical committee first meets, members may identify and invite additional representation on the technical committee, whose constitution is under constant review, changing to meet the subject matter. The size of the committee is a compromise to achieve a reasonably broad representation, whilst keeping it workable. Generally one nomination is permitted for each organisation on the committee. The committee will comprise a chairman, and a secretary, and may meet at intervals that suits the workload. Documents, with the exception of those marked for public comment are circulated privately amongst the committee members, and are not divulged to third parties, to avoid misunderstanding of documents that are still under development.

Requests for a new national standard can come from any source, and most frequently arise from established committees. Once a proposal is made for a new work item, it is considered in relation to the list of basic principles stated in section 10.1. A low sales potential for a standard is not taken to be a reason for rejecting or deferring a project (BS 0 Part 2,1981). Once a new work item is agreed, BSI makes announcements in their news circulars. Target dates are agreed for the circulation of a draft for public comment. The drafting commences with the development of an agreed scope and list of clause headings. The texts for the clauses are then developed outside the committee, usually by a small panel, or an individual knowledgeable on the subject. The secretary is then responsible to obtain views from members of the technical committee, co-ordination of related work and ensure overseas standards have not been overlooked.

Once the technical committee has approved a final version of the committee draft, it is made available for purchase as a draft for public comment over a 3-month period. The technical committee takes any public comments that arise into account. Where there are major comments, which reveal a lack of general consensus, as to the 'state of the art', the committee may need to reconsider the scope of the standard. Alternatively they may consider the possibility of publishing the document as a draft for development, or review the constitution of the committee and prepare a second draft for public comment.

When a technical committee has taken all the public comments into account and reaches consensus, there are formal procedures within BSI to obtain an authority for publication. The editing, typesetting, proof reading and printing responsibilities are then with BSI staff (BS O Part3, 1981). The standard is then available for purchase. Time scale for the entire process varies from 2 to 5 years, and longer for contentious subject matters.

There are procedures to update a standard. There may be routine amendments to deal with typographical errors. Technical amendments usually require technical committee approval and are normally circulated for public comment. There is usually a complete revision of the standard after 5 amendments. There are also reviews by the technical committee, usually every five years, to take a decision to confirm, revise or render the standard obsolete. Where a standard is deemed obsolete, it may be issued with an amendment stating that it should no longer be used for new situations, but may continue to be applicable to existing situations. Alternatively the standard may be withdrawn.

10.3 Development of an International Standard

In a similar way, International Standards may be developed to harmonise national standards, or to develop standards in new areas. The technical committee (or its working group) is made up of representatives from each national member body. A new work item can be proposed by any national member organisation, and where voted upon in favour, the new work item can be adopted. The committee would work on a draft, and when they have reached consensus, the text is submitted to all ISO member bodies for a five-month period to seek comments and a vote. The Draft International Standard (DIS) is approved if 2/3 of the participating member bodies vote in favour. The final text is prepared by the technical committee taking into account any comments, and is again submitted to member bodies for vote on the Final Draft International Standard (FDIS). If the text is again approved by 2/3 of the participating member bodies, then it is published as an International Standard (see ISO Directives Part 1:1995, & Part 3:1997). The time scale for the entire process varies, and an FDIS stage is aimed to be reached in 3years, with publications in about six months thereafter.

New standards are increasingly developed at an International or European level, rather than at a National level, in accordance with the principle that standards should be developed at the broadest level. There is however a danger that to achieve the necessary consensus of participating member bodies, much less can be said that can be agreed upon, which can make the end result less useful. An alternative approach is the development of informative documents, known as Technical Reports. ISO have also introduced a range of products which respond quickly to Industry needs, without having the full status of an International Standard (Smith, 1998).

10.4 Legal Status of Standards

The status of a standard depends upon the use that is made of it by the interested parties. It becomes binding if a claim of compliance is made, if it is invoked in a contract, or if it is called up in legislation. The standard can also be used as a trade description, when compliance is claimed. An International Standard may be implemented by a National Standards Organisation, and will therefore be used like any other National standard. The Standards organisations owe a duty of care in the preparation of standards. However it remains the responsibility of the user to ensure that a particular standard is appropriate to their needs.

A Court of Law may refer to the 'state of the art' knowledge described in a Standard, as a means of evaluating a case for negligence. Although compliance with a standard does not of itself infer immunity from legal obligations.

10.5 Existing Standard Concerned with Base Isolation

There is currently only one British Standard (BS6177, 1982) that deals with Base Isolation, and there are no other National or International Standards that deals with the subject of Base Isolation for vibration control of man made sources. The British Standard (BS6177) has the title ‘Selection and use of elastomeric bearings for vibration isolation of buildings’. It began originally as a Draft for Development (DD 47, 1975), and was updated and published in 1982 as a British Standard. BS6177 has not been subject to any amendments or revisions since it was first published. The standard gives useful guidance on the types of rubber bearings available, their design considerations, and factors for their use as a means of vibration isolation in buildings.

10.6 The Need for an Additional Standard

Whilst BS6177:1982 remains a useful document, it naturally does not reflect the current state of knowledge. In particular, it does not guard against the risk that Base Isolation may be inappropriately specified in certain circumstances, where either it is not adequately justified, or that there may be simpler alternative vibration control options which if properly considered may have resulted in a more cost effective solution. The standard does not adequately highlight the risk that Base Isolation could in some cases be detrimental to the dynamic performance of a building. It does not include the use of steel coil isolators, which were not used in the UK at the time the standard was issued.

In the light of more recent knowledge (Grootenhuis,1989; Newland and Hunt,1991; Cryer, 1994), and this thesis itself, it is appropriate that an additional standard be drawn up addressing the wider issues of the adoption and implementation of Base Isolation. During research for this thesis and as part of its objectives, the Author made a proposal to ISO for a new work item to prepare a standard dealing with the wider issues of Base Isolation. Some National comments arose on the proposal, with the principle element being a desire to see emphasis on characterisation of the source, with less emphasis on actual design procedures. It was approved as a new work item by ISO during 1998.

The Author concludes this thesis, with a proposal for this International Standard. It was originally submitted to ISO in March 1999 (see Sharif, 1999) as a very detailed standard and was received well, but there was a desire to also have a shorter high level document (ISO meeting minutes, docN208). The initial document was therefore redrafted by the Author (there being no formal comments) and submitted in October 1999 as a first stage committee draft for ISO/Technical Committee 108/SubCommittee2/Working Group 3.

In the proposed standard which follows, the page layout and numbering differs to the main text of this thesis, to meet ISO requirements for the layout of Drafts.