The paper presents the results of an investigation into the dispersion values, expressed in terms of limit-state spectral accelerations, which could be used for the pushover-based risk assessment of low-height to mid-height reinforced concrete frames and cantilever walls. The results of an extensive parametric study of a portfolio of test structures indicated that the dispersion values due to record-to-record variability and modelling uncertainty (ß ls,ru) are within the range from 0.3 to 0.55 for the near collapse limit state, and between 0.35 and 0.60 for the collapse limit state. The dispersions (ß ls,ru) proposed for the code-conforming and the majority of old (non code-conforming) frames are in between these values. On the other hand, the dispersions proposed for the old frames with a soft storey and an invariant plastic mechanism, and for the code-conforming cantilever walls, are at the lower and upper bounds of the presented values, respectively. The structural parameters that influence these dispersions were identified, and the influence of different ground motion sets, and of the models used for the calculation of the rotation capacities of the columns, on the calculated fragility parameters was examined and quantified. The proposed dispersion values were employed in a practice-oriented pushover-based method for the estimation of failure probability for eight selected examples. The pushover-based risk assessment method, although extremely simple and economical when compared with more rigorous probabilistic methods, was able to predict seismic risk with reasonable accuracy, thus showing it to be a practical tool for engineers.
COBISS.SI-ID: 7490657
The research team is actively involved (see Section 2) in the SAVI - NSF Science Across Virtual Institutes initiative “Virtual International Institute for Performance Assessment of Wall Systems”. This report was presented on the 3rd Workshop in the frame of the conference of the New Zealand Society for Earthquake Engineering 5 years after the Christchurch earthquakes. A journal paper related to this topic (FISCHINGER, Matej, KANTE, Peter, ISAKOVIĆ, Tatjana. Shake-table response of a coupled RC wall with thin t-shaped piers. Journal of structural engineering), which has immediately attracted big interest , was published at the beginning of 2017 (while majority of the work was done in 2016). Therefore, the paper is not directly included in this report. It is important to realize that each individual wall is a part of a complex 3D building system. While frequently neglected in the design and research, 3D interacting mechanisms are important in buildings with structural walls. Some of these mechanisms: the uplift of the wall boundary elements due to yielding, the fluctuating axial force due to rocking, bi-axial loading, the interaction due to the slab coupling and the resulting axial-flexural-shear interaction are addressed in the paper, based on the results of several experiments and benchmark studies. The need for the adequate numerical tools has been identified. A relatively simple, yet robust multiple-vertical-line-element model in which the springs are monitored with force-displacement relationships (rather than stress-strain) was developed, which has been able to respond to some of these challenges. The latest 3D version of this element, which can monitor shear-flexural interaction, was incorporated into the OpenSees platform. This element was very successfully used in several benchmark predictions involving many uncertain parameters and complex structural interaction, thus proving its robustness and efficiency.
COBISS.SI-ID: 7584865
The seismic vulnerability of twelve industrial precast building classes has been investigated by conducting nonlinear dynamic analyses on sample buildings from these building classes and taking into account selected seismic events. The results of the study can be used for seismic risk and loss estimation of precast building stock by considering the collapse of buildings and several other damage states, which were defined on the basis of the physical damage occurring to the vertical panels, horizontal panels, or masonry infills. The use of fragility functions derived on the basis of spectral acceleration corresponding to the so-called optimal period of the building class is suggested. Fragility functions are also presented for the peak ground acceleration, which is an intensity measure, independent of the building class. This means that all these fragility functions can be used to discuss how the variation of structural configurations, code levels, and the type of non-structural components and their fastenings affect the overall seismic response of industrial precast building classes, at a given level of the seismic intensity measure. It can be concluded that the vulnerability of non-structural elements is the largest in the case of precast buildings with horizontal panels, followed by those with masonry infills and vertical panels. It was also observed that non-structural components have an impact on the structural collapse, both in terms of reducing the median and increasing the dispersion of the collapse fragility functions. It was also observed that a higher seismic design force may worsen the seismic performance of a precast building if the connections are not adequately designed.
COBISS.SI-ID: 7465057
Consolidation methods used for structural and non-structural elements of buildings with cultural value, in order to improve their seismic resistance, are based on the use of new materials which are compatible with the original materials of these historic buildings. The article presents an approach to the design of compatible lime injection grouts for consolidation of decorative plasters of cultural heritage buildings, which are detached from the substrate. The approach originates from recent findings in design of compatible injection grouts for systematic grout injection of masonry walls that were damaged in the earthquake or their seismic resistance is too low. Established test methods for these materials are modified so that they are suitable for evaluating the key properties of non-structural grouts in the laboratory and in the field. The results of the tests showed that a non-structural grout consisting of 1 volume part of hydrated lime CL 90-S and 3 volume parts of inert limestone filler, with 0.5 % of the polycarboxylate ether based superplasticizer, fulfilled most of the established requirements.
COBISS.SI-ID: 7486561
In the paper, five procedures for the assessment of the seismic performance of low-rise RC buildings at different levels of complexity are presented and discussed. They include simple procedures based on methods originally developed in Japan (levels 1 and 2), the N2 method with two variants of the mathematical model (levels 3 and 4), and non-linear dynamic analysis (level 5). The procedures have been applied to seismic assessments of three RC building structures. A small difference between the N2 and NDA results was observed, whereas the results of the procedures at the first two levels are much more conservative. On the other hand, the amount of input data and of computational work increases with the increasing complexity level. Research is still needed on the definitions of capacities, especially the shear capacity of the structural members, and on the capacity of the whole structure. The initial effective stiffness of the structure proved to be the most important quantity which determines the seismic demand.
COBISS.SI-ID: 7137121