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A methodology for the evaluation of the annual probability of occurrence of post-elastic seismic damage in realistic structures is presented. The seismic damage hazard analysis (SDHA) is carried out here by coupling conventional seismic hazard analysis (SHA) for the site and the structural response to earthquakes of different intensities. The structural performance is statistically investigated by conducting appropriate non-linear dynamic analyses for a limited set of real ground-motion records that might potentially pose a threat to the structure at the site. The merging of these two approaches permits calculation of the seismic hazard faced by the structure in direct damage terms. The methodology is presented in this paper with the aid of a simple illustrative case study where the annual probability of damage and, eventually, failure of a power house steel structure is computed. This methodology can find practical applications in seismic retrofit of nuclear power plant structures and in the evaluation of seismic damage hazards in new structure designs.
Planning and designing railway tunnels with an explicit reference to safety issues is becoming of utmost importance since the combination of high speed, mixed goods–passenger traffic and extreme length of the new tunnels under design or concept evaluation, have sensitively modified the inherent safety of the railway tunnel. Although the probability of occurrence of accidental events may still be considered rather low, the possible consequences of such events in long tunnels can be catastrophic, therefore raising the overall risk to levels that may be no more acceptable. The scope of this paper is to illustrate the state-of-practice related to risk analysis of long railway tunnels. First, ambitious tunnel projects are briefly reviewed. The applicable risk-analysis procedures are then described and discussed. The problem of risk appraisal is addressed and quantitative target safety levels are proposed. Safety systems for risk reduction are outlined.
Structural Eurocodes offer the opportunity of harmonized design standards for the European construction markets and the rest of the world. Eurocodes aim at delivering structures with an appropriate degree of reliability and in an economic way. The reliability requirements of the Eurocodes and the associated background philosophy are discussed in this contribution. The definition and the measure of reliability in standards and especially in the Eurocodes are reviewed. The procedures for selecting target and acceptable re-liability levels are summarized and the reliability differentiation in the Eurocodes is highlighted. Global failure aspects including robustness are briefly discussed. Finally examples from case studies are provided demonstrating the applicability and the benefits from the reliability differentiation approach.
Since resistance against extreme environmental actions explicitly forms part of the basis of structural design, the implications of climate change emphatically needs to be considered. This paper presents the results of a survey of climate change developments in South Africa and Germany from the perspective of its rele-vance to extreme actions on infrastructure. It is concluded that the importance of climate change is broad and varied. However incorporation into practice is mostly nominal. Although general trends of climate change are confirmed, proper information on changes in extreme conditions is limited. Coastal engineering seems to be the field which is most active in providing for climate change. It is concluded that risk based methodologies developed to treat the variability and uncertainties of extreme actions and consequences in present practice provide a sound basis for treating the effects of climate change in a rational and optimal manner. It is also clear that there is strong motivation for extensive research as the best action to be taken presently, anticipating appropriate adjustment of reoptimized design methodologies.
The results of a survey of climate change developments in South Africa and Germany from the perspective of its relevance to extreme actions on infrastructure are presented in this paper. It is concluded that the importance of climate change is broad and varied. However incorporation into practice is mostly nominal. Although general trends of climate change are confirmed, proper information on changes in extreme conditions is limited. Coastal engineering seems to be the field which is most active in providing for climate change. It is concluded that risk-based methodologies developed to treat the variability and uncertainties of extreme actions and consequences in present practice provide a sound basis for treating the effects of climate change in a rational and optimal manner. It is also clear that there is strong motivation for extensive research as the best action to be taken presently, anticipating appropriate adjustment of re-optimised design methodologies.
Solar energy represents a clean, natural and sustainable source of energy. Solar photovoltaic panels can be installed on roofs of structures or in the ground. This contribution focusses on ground-mounted systems, which are presently widely implemented. At present limited guidelines on the design of solar ground-mounted structures are available. Usually standards for the design of normal buildings are applied. However, the design of ground-mounted structures significantly differs from common structural design by: (1) a lower design lifetime (20-25 years) is accepted; (2) failure is not associated with the loss of human life; (3) resistance uncertainties need due attention; (4) uplift wind forces dominating structural reliability are associated with a large scatter. That is why the reliability analysis and optimal design of ground-mounted solar systems is investigated herein. The failure costs and especially their ratio to the initial costs are analyzed considering the data provided from the industry. Probabilistic reliability analyses are carried out and optimum design levels are computed for representative cost ratios. The optimal target reliability depends on the ratio between failure and initial costs; reliability index of 3.5 corresponds to a reasonable cost ratio of 10.
Specification of the target reliability levels is one of the key issues of the assessment of existing structures. ISO 13822:2010 and ISO 2394:1998 indicate procedures for deriving the target reliability levels by optimisation of the total cost related to an assumed remaining working life of a structure. In the submitted study this approach is applied to estimate the target reliability levels of an existing structural member in conjunction with the human safety criteria. Obtained results are critically compared with the recommendations given in present standards. It appears that the requirement on the same target reliability levels for existing structures as for new structures is uneconomical. Further, the cost optimisation seems to yield rather low reliability levels and human safety criteria become commonly decisive for specification of the target reliabilities of existing structures.