Structural Engineering International 2/2012 Technical Report 275 Swiss Standards for Existing Structures Eugen Brühwiler, Prof., Dr, Civil Eng., Civil Engineering Institute, Swiss Federal Institute of Technology—EPFL, Lausanne, Switzerland; Thomas Vogel, Prof., Civil Eng., Institute of Structural Engineering, Swiss Federal Institute of Technology—ETH Zurich, Switzerland; Thomas Lang, Civil Eng., Swiss Federal Office of Transportation, Bern, Switzerland; Paul Lüchinger, Dr, Civil Eng., Meyer Bauingenieure AG, Zürich, Switzerland. Contact: eugen.bruehwiler@epfl.ch DOI: 10.2749/101686612X13291382991209 to higher solicitation while meeting the safety requirements. Such an approach is needed to avoid rather cost-intensive or even unnecessary interventions (which are often the result of insuf- ficient know-how and information about the existing structure). Over the last 20 years, a methodol- ogy inherent to existing structures has evolved and has already been success- fully applied. However, it has not yet been really adopted in practice by the majority of structural engineers. This is explained by the fact that there are no standards available which the engineer can rely on. For this reason, the Swiss Society of Engineers and Architects (SIA) launched a pioneering project in 2005 to develop a series of standards for existing structures. In a country with a rather well-developed infrastructure such as Switzerland, the establishment of this series of standards is a real need arising from the fact that significantly more than half of all current and future structural engineering activities are and will be related to existing structures. Objectives for the New Standards The general objectives of the proj- ect consisted in editing a series of user-friendly standards dealing with all aspects of existing structures. In particular, the following typical chal- lenges for the structural engineer are addressed: – Higher live loads (such as traffic loads or live loads in buildings) are to be applied for which an existing struc- ture has not been initially designed. The structural engineer has to prove that these can be carried by the existing structure without asking for costly strengthening interventions. – In case the structural safety for higher live loads can be verified, the fatigue safety, the remaining Abstract In January 2011, the Swiss Society of Engineers and Architects (SIA) pub- lished a series of standards for existing structures. The standard entitled ‘existing structures—bases for examination and interventions’ specifies the principles, the terminology and the appropriate meth- odology for dealing with existing struc- tures. This standard is complemented by a series of standards which treat spe- cific items regarding ‘actions on exist- ing structures’, ‘existing concrete, steel, composite, timber and masonry struc- tures’ as well as ‘geotechnical aspects of existing structures’. It is expected that these standards will provide effective solutions on questions such as higher live loads, accidental actions or the res- toration and improvement of the dura- bility of existing structures. This paper highlights major principles, in particular those related to risk-based safety, pro- portionality of interventions and updat- ing of variables. Methodological aspects of the main activities, that is, exami- nation of structures and intervention measures, are described. Keywords: standards; existing struc- tures; updating; risk-based safety; pro- portionality; examination; interventions. Introduction When dealing with existing structures, most structural engineers apply stan- dards valid for the design of new struc- tures. This is a problematic approach as standards for new structures are in principle not, or only, analogously applicable to existing structures. The professional approach to exist- ing structures is based on an inherent methodology that essentially includes collecting detailed actual information as the structure already exists. The controlling parameters are determined more precisely, and for example, the structural safety of an existing struc- ture is proven using so-called updated values for actions and resistance. In this way, it can often be shown that an existing structure may be subjected Fig. 1: General overview on the series of standards SIA 269 for existing structures SIA 269 – Basis for examination and interventions 269/1 Actions 269/2 Concrete 269/3 Steel 269/4 Composite 269/5 Timber 269/6 Masonry 269/7 Geotechnics 269/8 Seismic aspects