Operational methods for the assessment of existing structures

Assessment of existing structures is an urgent issue of a great economic significance in most countries around the world as more than 50% of all construction activities concern existing buildings, bridges and other civil engineering works. Presently the Eurocodes which will be used in all CEN Member countries are primarily focused on the design of new structures. Additional operational rules for existing structures are still missing. The international standard ISO 13822 provides only general principles for the assessment of existing structures which should be further developed for their effective operational use in practice. The current project addresses the importance for implementing principles of the assessment and verification of existing structures in practice in the Czech Republic and other partner countries. The project is supported by the Czech Chamber of Chartered Engineers (ČKAIT). The project consortium, under the leadership of the Klokner Institute of the Czech Technical University in Prague (KI CTU), consists of the Secondary Technical School of Civil Engineering (CZ) and the research institutions and universities from four EU Member States (DE, ES, IT, NL) and one associated country (TR). All researchers of the partnership are involved in research projects dealing with reliability assessment of existing structures. They participate in the national and international standardization activities within organizations CEN and ISO. The project outcomes include vocational training materials based on documents of the international research organization Joint Committee on Structural Safety JCSS and international research projects, selected outcomes of the previous project of the Leonardo da Vinci programme (developed by 5 partners of the present consortium in 2008-2010) and also on background documents to new European and international standards. A basic project outcome is the already published Handbook 1 “Innovative Methods for the Assessment of Existing Structures” which focuses on methodologies to assess and evaluate the condition of existing structures. The methodologies provided are independent from type of structure and material and are compatible to the background methodologies used in the Eurocodes. Practical techniques for the assessment of existing structures and associated case studies based on the methodologies of Handbook 1 are presented in this Handbook 2 of this project entitled “Operational Techniques for the Assessment of Existing Structures”. Handbook 2 consists of ten chapters. Chapter 1 gives a brief overview of the basic concepts and important terminology used in the assessment of existing structures. Chapter 2 summarizes currently used techniques including non-destructive testing, inspection and monitoring and provides quantitative information for their implementation. Chapter 3 reviews the basic aspects of structural modelling and analysis and discusses them in an application dealing with a masonry building; thereby an equivalent frame model, a finite element model and a kinematic model are compared. Chapter 4 describes the verification procedure compatible to the Eurocodes by using updated partial factors and design values and based on the methodological aspects discussed in Handbook 1. Practical applications of updating are then shown in Chapter 5. They deal with the reinforcement steel strength, with proof load and with updating of earthquake action parameters. Chapter 6 deals with concrete structures; it summarizes first practical codes, standards and recommendations. It also includes two case studies dealing a) with strengthening of concrete columns and b) with construction of additional storeys i.e. with implementation of additional loading in an existing concrete building. Assessment of existing metal structures is presented in Chapter 7. General aspects are provided and illustrated in the reassessment of an 115-year old truss bridge. The implementation of operational techniques in the assessment and rehabilitation of existing timber structures is shown in Chapter 8. The degradation of timber properties is discussed and illustrated in a characteristic case study of a building in Lucca (Italy). Particular attention is paid to heritage buildings which are treated in a separate chapter namely Chapter 9. Basic aspects of investigations techniques are provided. Three case studies of heritage structures in Italy are analysed in detail a) the rehabilitation of a historical sanctuary near L’Aquila, b) the requalification of an old bell tower in Pisa and c) the repair of a masonry arch bridge in Carrara. Finally Chapter 10 addresses the important issue of existing structures in seismic zones. The seismic retrofit of the structures is summarised, basic techniques are presented together with their implementation in two case studies concerning the strengthening of a r.c. school in Denizli (Turkey) and the repair of an earthquake damaged r.c. residential building in Molise (Italy). It is believed that the material of this Handbook 2 is presented in an understandable way for the practicing engineers reflecting the experience of the authors and supported with many case studies described herein in detail. The methodologies presented in Handbook 1 are referred to and in addition many references are provided for background material and further study.