Although repair and strengthening under non-seismic actions is not yet covered by the relevant material-dependent Eurocodes, this Part of Eurocode 8 was pecifically developed because:
- For most of the old structures seismic design was not considered originally, whereas the ordinary actions were considered, at least by means of traditional construction rules Seismic hazard evaluations in accordance with the present knowledge may indicate the need of strengthening campaigns.
- The occurrence of earthquakes may create the need for important repairs.
Furthermore, since within the philosophy of Eurocode 8 the aseismic design of new structures is based on a certain acceptable degree of structural damage in the event of the design earthquake, criteria for redesign (of structures designed according to Eurocode 8 and subsequently damaged) constitute an integral part of the entire process for seismic structural safety.
In strengthening and repair situations, qualitative verifications for the identification and elimination of major structural defects are very important and should not be discouraged by the quantitative analytical approach proper to this Part of Eurocode 8. Preparation of documents of more qualitative nature is left to the initiative of the National Authorities.
This Standard addresses the structural aspects of repair and strengthening, which is only one component of a broader strategy for seismic risk mitigation that includes pre and/or post-earthquake steps to be taken by several responsible agencies.
In low seismicity zones, this Standard may be adapted to local conditions by appropriate National Annexes.
The scope of Eurocode 8 is defined in 1.1.1 of EN 1998-1 and the scope of this
Standard is defined in 1.1. Additional parts ofEurocode 8 that are planned are indicated in 1.1.3 of EN 1998-1.
Its scope is the following:
- To provide criteria for the evaluation of the seismic performance of existing individual structures.
- To describe the approach in selecting necessary corrective measures
- To set forth criteria for the design of the repair/strengthening measures (i.e. conception, structural analysis including intervention measures, fmal dimensioning of structural parts and their connections to existing structural elements).
When designing a structural intervention to provide adequate resistance against seismic actions, structural verifications shall also be made with respect to non-seismic load combinations.
Reflecting the basic requirements of EN 1998-1, this Standard covers the repair and strengthening of buildings and, where applicable, monuments, considering commonly used structural materials (concrete, steel, masonry and timber).
Although the provisions of this Standard are applicable to all categories of buildings, the repair or strengthening of monuments and historical buildings often requires different types of provisions and approaches, which should take in proper consideration the nature of the monuments.
Since existing structures:
(i) reflect the state of knowledge of the time of their construction,
(ii) possibly contain hidden gross errors,
(iii) may have been submitted to previous earthquakes or other accidental actions
with unknown effects, structural evaluation and possible structural intervention are typically subjected to a different degree of uncertainty (level of knowledge) than the design of new structures.
Different sets of material and structural safety factors are therefore required, as well as different analysis procedures, depending on the completeness and reliability of the information available.
