Using Nonlinear Static Procedures for the Seismic Assessment of Irregular RC Buildings

The application of Nonlinear Static Procedures (NSPs) to assess the seismic vulnerability of existing structures has become widely accepted and extensively used in the literature as well as in engineering practice. Nevertheless, their success in predicting the response of irregular buildings is not yet fully verified. The main goal of the present study is to evaluate the capability and accuracy of some of the existing nonlinear static procedures (N2 and ACSM, in this case) to estimate the seismic performance of irregular structures. In order to accomplish this objective, four existing buildings, irregular in plan and elevation, were subjected to an extensive number of nonlinear static and dynamic analyses. The comparisons, focused on both global and local response parameters provide first indications on the reliability of static procedures to estimate the actual response of irregular RC buildings.N/

Effect of Different Modelling Assumptions on the Seismic Response of RC Structures

The introduction of new regulations for seismic assessment of structures established stricter performance requirements for existing buildings. In order to account for the poor seismic behaviour of such buildings, recent seismic codes, namely Eurocode 8 (EC8), introduce a number of prescriptions regarding issues such as analysis type, load distribution, accidental eccentricity, etc. At the same time, these codes give room for engineering judgment to be used with reference to the definition of structural and non-structural elements such as slabs or infill walls, and obviously leave the modelling assumptions, such as Finite Elements typology, meshing, mass modelling, etc. to the analyst decision. As such, four existing RC buildings, representative of traditional Mediterranean construction, considering different modelling assumptions, were subjected to an extensive number of nonlinear static analyses. The interpretation of possible deviations in the results will hopefully provide indications on the relative importance of each modelling parameter or decision.N/

Correction to: Deterministic seismic risk assessment in the city of Aigion (W. Corinth Gulf, Greece) and juxtaposition with real damage due to the 1995 Mw6.4 earthquake (Bulletin of Earthquake Engineering, (2019), 17, 2, (603-634), 10.1007/s10518-018-0464-z)

An incorrect version of Fig. 15 was erroneously published in the original article and needs to be correctly read as with this updated version. © 2018, Springer Nature B.V

Τhe November 2015 Mw6.4 earthquake effects in Lefkas Island

This work describes the outcome of two field surveys in Lefkada Island, after the 17.11.2015 earthquake of Mw6.4 at its southwestern peninsula. Geo-environmental effects were observed throughout the western flanks of the mountain massif, parallel to the activated fault. Structural damage was mainly observed in the epicentral area where macroseismic intensity was assessed as VIII, based on registered damage and assumed vulnerability per building typology. Both modern and traditional buildings exhibited notable seismic performance. The distribution of the damage per building category is presented, based on site surveys and post-seismic usability characterization by the local Earthquake Rehabilitation Organization. The survey highlights the frequent presence of the so-called “pontelo” dual system at both ground floor and two-story stone masonry buildings at the western mountain villages. This structural type, unique within the Greek territory, revealed significant seismic performance and the need of engineering restoration measures is underlined

Validation and improvement of Risk-UE LM2 capacity curves for URM buildings with stiff floors and RC shear walls buildings

This paper addresses seismic vulnerability assessment at an urban scale and more specifically the capacity curves involved for building damage prediction. Standard capacity curves are a function of predefined building typology and are proposed in the Risk-UE LM2 method for computation of the corresponding damage grades. However, these capacity curves have been mainly developed for building stock of southern European cities and the accuracy of their application with different building features, such as the ones of cities of northern Europe should be assessed. A recent research project of seismic scenarios for the cities of Sion and Martigny in Switzerland provided the opportunity to check the capacity curves of Risk-UE LM2 method. Within the framework of this project, a detailed analysis was achieved for more than 500 buildings. These buildings were typical Swiss buildings and were composed of both unreinforced masonry buildings with stiff floors and reinforced concrete buildings. The construction drawings of each building were collected in order to have the most accurate information about their main structural characteristics. The typological classification that has been adopted was developed in a recent research project. Based on the individual features of the buildings, individual capacity curves were defined. Results of the seismic assessment applied to the 500 buildings compare very well with those obtained by using Risk-UE LM2 method for unreinforced masonry buildings with stiff floors. A slight improvement may be proposed for buildings with three stories through their introduction to the category of low-rise instead of mid-rise buildings. By contrast, accuracy for reinforced concrete buildings with shear walls is very poor. Damage prediction using related capacity curves of Risk-UE LM2 method does not correspond to reality. Prediction is too pessimistic and moreover damage grades increase with the height category (low-rise, mid-rise and high-rise) of these buildings which is in contradiction with the observed damages for this type of buildings. Improvements are proposed to increase the accuracy of the seismic vulnerability assessment for northern European building stock. For unreinforced masonry buildings, a slight modification of the limits of the height category of buildings using the ones defined for RC buildings improves the damage prediction. For reinforced concrete buildings with shear walls improved capacity curves derived from the typological curves of the specific typology C are proposed

Geometric structure and properties of linear time invariant multivariable systems in the controller canonical form

In this study, the authors analyse some fundamental structural properties of linear time-invariant multivariable systems in the controller canonical form and present a direct method for the computation of bases and associated friends for output-nulling, input-containing and reachability subspaces in terms of the parameters of the system and the invariant zero structure, both in the non-defective and in the defective case. Using this analysis, it is possible to express the solvability conditions of important control and estimation problems in terms of easily checkable conditions on the system matrices

Seismic risk and loss assessment for Kalamata (SW Peloponnese, Greece) from neighbouring shallow sources

A large amount of new and existing data was applied, aiming at delineating structural seismic risk in the earthquake prone modern city of Kalamata (SW Peloponnese) that was largely reconstructed after the devastating Mw=5.8 earthquake of September 13, 1986. Synthetic site-specific ground motion parameters derived from the nearest known shallow hazardous seismogenic sources were combined with EMS-98 structural vulnerability estimates of the city’s building stock and four structural and economic loss models have been developed on a building-block scale. Assuming absence of non-linear, near-source effects, the building stock of Kalamata is anticipated to present sufficient seismic behaviour, due to the large number of new and innovative constructions replacing the demolished ones after the 1986 earthquake. © 2018 – OGS