Opening Address. Professor L A Clark OBE, FREng. Professor of Structural Engineering, The University of Birmingham

Transcription

1 Opening Address Professor L A Clark OBE, FREng Professor of Structural Engineering, The University of Birmingham Chairman of the Thaumasite Expert Group Report Abstract Professor Clark will give an outline of the history of the field cases of thaumasite in the UK which led to the UK Government setting up the Thaumasite Expert Group which he chaired. The challenges which the Group faced will be described and the rationale for the membership of the Group explained. The scope and outcomes of the two subsequent reviews of the recommendations of the Group will be presented briefly. Finally, reference will be made to the link between the work of the Group and the recent research at the University of Sheffield.

2 Thaumasite Sulfate Attack The UK Experience Professor L A Clark OBE FREng Professor of Structural Engineering The University of Birmingham Chairman Thaumasite Expert Group

3 History 1990 Domestic properties Feb 1998 M5 bridges

4 Tredington Ashchurch Bridge TSA discovered during strengthening of piers for impact loading Bases and piers had been constructed in excavation backfilled with excavated clay Concrete in a sump

5 TSA in M5 bridge foundation

6 TSA in M5 bridge foundations

7 History 1990 Domestic properties Feb 1998 M5 bridges March 1998 Question in House of Commons 25/3/ 1998 Contacted by DETR to chair TEG 1/4/1998 Appointed Chairman by Minister and announced to House 13/5/1998 TEG announced to House by Minister

8 Thaumasite Expert Group Brief Prepare interim advice and guidance Consult widely Report to DETR within six months

9 Scope of Brief Identification of structures at risk Diagnosis Appraisal Structural assessment Prognosis and remedial action Specification Further research

10 Expert Group Had to deal with a range of issues: Scientific Lack of data Commercial interests Public concerns over safety Professional clients and owners (bridges) House owners and mortgage lenders highly emotive

11 Expert Group Members Chairman: Chartered Structural and Civil Engineer 12 Members representing organisations and institutions from the scientific, design, specification, supply, contracting (civil and building), government, client, surveying, valuing and mortgage lending sectors Secretary from BRE 2 Technical Experts from BRE 32 Consultees from 15 organisations

12 History 1990 Domestic properties Feb 1998 M5 bridges March 1998 Question in House of Commons 25/3/ 1998 Contacted by DETR to chair TEG 1/4/1998 Appointed Chairman by Minister 13/5/1998 TEG announced to House by Minister 15/5/1998 First meeting of Group 7/12/1998 Report presented to Minister 25/ Report published

13 Report of Thaumasite Expert Group

14 Reaction to Report Well received Balanced Advice safe and robust No significant adverse impact on industry sectors Some problems of interpretation

15 Reviews of Report March 2000 First Review - One-Year March 2002 Second Review - Three-Years Second Review not officially accepted by Government until January 2003 as a result of change of responsibility from DETR to ODPM

16 Scope of Reviews New Guidance Dissemination Current impact and awareness Problems New cases New features New research Guidance in preparation

17 Outcomes of Reviews Recommendations robust Problems of interpretation Data do not permit relaxations other than those in BRE SD1 About 50 new cases Concrete containing siliceous aggregates Reinforcement bond

18 BRE Special Digest SD1 Provides guidance on concrete in aggressive ground Replaces BRE Digest 363 Published in 2001 in 4 Parts Includes guidance on special products such as precast concrete pipes Second Edition in updates to BS EN 197-1:2000 and BS 8500:2002

19 Part 1 of Special Digest 1 (SD1)

20 Research Report identified research areas Sheffield University has been one of the centres which has taken up the research challenge Mixes Reaction mechanism Clay/concrete interface

21 Seminar Purpose Disseminate the results of research at Sheffield UK has significant experience of the management of TSA Other countries have research expertise and cases of TSA We need to share experience and best practice for the benefit of society