Significance of the achievement - summary: Invitation for Ambraseys Lecture is a prestigious award given to the leading European researchers in the field of earthquake engineering and seismology. It is awarded to only one person in 2 years. Significance of the achievement – description: The analysis of structures is a fundamental part of seismic design and assessment. It began more than a hundred years ago, when static analysis with lateral loads of about 10% of the weight of the structure was adopted in seismic regulations. For a long time seismic loads of this size remained in the majority of seismic codes worldwide. In the course of time, more advanced analysis procedures were implemented, taking into account the dynamics and nonlinear response of structures. In the future methods with explicit probabilistic considerations may be adopted as an option. In this paper, the development of seismic provisions as related to analysis is summarized, the present state is discussed, and possible further developments are envisaged. The paper presents a written version of the "Ambraseys Lecture" ( http://www.eaee.org/prof.-nicholas-ambraseys-distinguised-lectures), which will be the main keynote lecture at the 16th European Conference on Earthquake Engineering in 2018. The paper provides a summary of the development of the provisions related to the analysis in the seismic regulations. The current state and anticipated possible further developments in this area are also addressed. The article, which comprises 42 pages, also includes the achievements of the research group, i.e. the extended N2 method, which allows the method to be used in the case of buildings when torsion and/or higher modes have an important influence on the seismic response of buildings, and the practice-oriented simplified probabilistic method for the assessment of seismic risk.
COBISS.SI-ID: 8244065
Significance of the achievement - summary: Results of these research achievements have been already included in the final draft of the new version of the European standards Eurocode 8. They represent an important contribution towards the explicit introduction of the probabilistic procedures into design. Significance of the achievement - description: Decision models for the verification of seismic collapse safety of buildings are introduced. The derivations are based on the concept of the acceptable (target) annual probability of collapse, whereas the decision making involves comparisons between seismic demand and capacity, which is familiar to engineering practitioners. Seismic demand, which corresponds to the design seismic action associated with a selected return period, can be expressed either in terms of an intensity measure (IM) or an engineering demand parameter (EDP). Seismic capacity, on the other hand, is defined by dividing the near-collapse limit-state IM or EDP by an appropriate risk-targeted safety factor (γim or γedp), which is the only safety factor used in the proposed decision model. Consequently, the seismic performance assessment of a building should be based on the best possible estimate. For a case study, it is shown that if the target collapse risk is set to 1e−4 (0.5% over a period of 50 years), and if the seismic demand corresponds to a return period of 475 years (10% over a period of 50 years), then it can be demonstrated that γim is approximately equal to 2.5 for very stiff buildings, whereas for buildings with long periods the value of γim can increase up to a value of approximately 5. The model using γedp is equal to that using γim only if it can be assumed that displacements, with consideration of nonlinear behaviour, are equal to displacements from linear elastic analysis. Results of these research achievements were already included in the final draft of new Eurocode 8.
COBISS.SI-ID: 8259681
Significance of the achievement - summary: Unique experimental results are presented (due to their size structural walls are relatively seldom tested; only few tests were done on shake tables; in particular tests of the coupled walls have been practically non-existent). Therefore there was a great interest of the research community in these results to be published. Significance of the achievement - description: A shake-table test of a 1:3 scale model of a thin, lightly reinforced concrete (RC), 5-story coupled wall, representing a typical apartment building with a high wall-to-floor area ratio, was performed. The wall consisted of two T-shaped piers, faced to each other by the webs, which were connected at each story level by the coupling beam and slab. The wall was subjected to a series of uniaxial and biaxial seismic excitations. Two different structural details providing different degrees of confinement were used at the free edges without boundary columns. The lightly confined free edges of the flanges (using hairpin transverse reinforcement) behaved satisfactorily in the case of moderate seismic demand. Due to the beam-slab interaction and the slab, which was considerably ticker than in typical buildings, the coupling beams were much stronger than expected, causing brittle shear failure of the overloaded wall piers under bidirectional excitation. The analyzed wall developed substantial strength and low ductility. The main observations of the experiment were confirmed by the results of postexperimental analytical studies performed using a three-dimensional (3D) multiple vertical-line element model, which has been incorporated into a well-known open-code program system.
COBISS.SI-ID: 7937121
Significance of the achievement - summary: Seismic resistance is a key factor contributing to the resilience of heritage buildings. Significance of the achievement - description: Cultural heritage assets, the bearers of historic evidence, are under continuous pressure of changing, deterioration and destruction. Therefore, there is a need to identify and monitor the related risks and develop appropriate measures for increasing the resilience of cultural heritage especially those located in seismic-prone areas.. The activities for establishing of a European system for data collection and its application in the field of preventive conservation are on-going process where the issue of risks and resilience is well addressed. Recently there is an interest for developing a model of built heritage resilience related to mitigation and reaction on sudden environmental impacts following the resilience models of contemporary buildings. However, these models cannot be simply extended to heritage buildings because of their specific character. In this chapter a contribution to acceptable resilience model of heritage buildings is presented.
COBISS.SI-ID: 8076129
Significance of the achievement - summary: Use of the recycled materials has an important contribution to the sustainability of the built environment. In this field of research D. Antolinc got a reward for the “Best innovation in the field of energetics” presented at the event “Inovacija energetike ’17; Kranj, Slovenija”. Significance of the achievement - description: The paper deals with the influence of recycled aggregate, gained by crushing hardened concrete that was previously used in construction, on the properties of concrete mixture in fresh and hardened state. Selective demolition of the RC structure was used to produce concrete rubbles. As reference concrete mixture, ordinary concrete OC used in the initial phase of the RRT+ program in the framework of COST Action TU1404 was selected. For the preconditioning of coarse recycled aggregate the same procedure as for the coarse natural aggregate used in the OC concrete was followed. This approach proofed to be very efficient in solving problem of high water absorption of recycled aggregates in fresh concrete. Type and content of the SP and W/C ratio were adjusted in order to provide adequate workability. The obtained results show that concrete mixtures with the recycled concrete aggregate can possess adequate properties in fresh state, if highly efficient PCE SP is used. Reduction in mechanical properties in hardened state is relatively low, even in case of full replacement of natural aggregate by crushed concrete grains. Next step will be study of durability properties of these concrete mixtures. Production of precast structural and non-structural elements is field where the developed concrete mixtures can be applied in most efficient way.
COBISS.SI-ID: 8312673