Eleni Smyrou

Sectional response of T-shaped RC walls

Deformation quantities such as strain, curvature and displacement are of paramount importance in seismic design within a performance-based procedure that aims to control the structural response at predefined levels of inelastic action. Given the importance of curvature expressions independent of strength for the design process, and for the particular case of T-shaped walls, the curvature trends at yield, serviceability and ultimate limit state are determined in graphical and analytical form. The comprehensive set of equations proposed in this work are strength independent and allow the reliable computation of limit-state curvatures, essential in a displacement-based design approach, and thus the realistic estimation of appropriate ductility factors in the design of T-shaped walls. Furthermore, results regarding the section properties of T-shaped walls, such as the elastic stiffness and the moment capacity for opposite directions of loading, offer additional information on T-shaped walls.

Behaviour of steel cushions subjected to combined actions

Mild steel is relatively low-cost and easily accessible material to fabricate some structural members. It would be a significant advantage if seismic energy dissipaters that are used in structures constructed in the earthquake prone areas, could also be produced on site. In this paper, a promising seismic energy dissipater made of mild steel, so-called steel cushion (SC) is presented. It is provided experimental and analytical responses of SCs subjected to bi-axial loadings. SC rolls under the lateral loading that allows relocation of the plasticized cross-section. Henceforth, SC dissipates considerable amount of seismic energy. A series of tests were performed to achieve experimentally the behavior of SC subjected to longitudinal and transversal loading. Finite Element Models (FEMs) were also generated to reproduce the experimental backbone curves and to predict the bi-directional response properties for discrete transversal forces and plate thicknesses. Closed-form equations were derived to determine yield and ultimate forces and the corresponding displacements as well as location of the plasticized sections. The behavior of SC could either be projected by the FEMs with the exhibited parameters or by means of the proposed closed-form equations and the normalized design chart.

Discussion on the response of unreinforced masonry to low-amplitude recursive loads: case of Groningen gas field

Unreinforced masonry (URM) is a fragile material that responds to cyclic load reversals in a non-ductile way, unless special measures are taken. Damage occurs in large amplitude loads causing partial or total collapse in some cases, as it was observed in the past earthquakes. Response of URM to recursive, frequent but low-amplitude seismic loads, on the other hand, is a relatively new topic that needs experimental and analytical validation. This paper focuses on Groningen URM buildings that have been subjected to low-amplitude load reversals in the last decades, especially in the very last decade, due to the induced seismicity caused by gas extraction. In the paper, previous experimental findings are reviewed mostly focusing on the range of low amplitudes. An exercise with existing hysteresis rules, trying to find residuals after recursive seismic actions, has been presented. Dimitrios Dais, Ihsan E. Bal, and Eleni Smyrou

Simulation of the earthquake-induced collapse of a school building in Turkey in 2011 Van Earthquake

Collapses of school or dormitory buildings experienced in recent earthquakes raise the issue of safety as a major challenge for decision makers. A school building is ‘just another structure’ technically speaking, however, the consequences of a collapse in an earthquake could lead to social reactions in the complex aftermath of a seismic tremor more than any other type of structure may possibly cause. In this paper a school building that collapsed during 2011 Tabanli, Van Earthquake in eastern Turkey, is analysed in order to identify the possible reasons that led to collapse. Apart from the inherent deficiencies of RC buildings built in Turkey in the 80s and 90s, its structural design exhibits a strikingly high asymmetry. In the analyses conducted, much attention has been given to the direction of the earthquake load and its coincidence with the bi-axial structural response parameters. The failure of the structure to comply with the 1975 Code, in vigor at the time of construction, has also been evaluated with respect to the structure’s collapse. Among the parameters that controlled the collapse, the high plan asymmetry and the coincidence of the vulnerable directions with the dominant shaking direction were critical, as well as the underestimation of the seismic hazard and the lateral design force level, specified by the then Turkish Earthquake Code.

Mitigating Seismic Risks in Historical Masonry: An Example Project

Protection of cultural heritage buildings against strong seismic events is one of the most challenging tasks modern engineers are called to tackle. Masonry structures are complex with regional and historical diversities rendering extremely difficult defining generalized rules. A holistic approach that involves interdisciplinary collaboration and a full package of engineering from monitoring to testing is a necessity. The sources for assessment, strengthening, and preservation are not enough for the entire inventory of heritage buildings, thus there always exists need for conducting risk studies to estimate the seismic risk these structures are exposed to. The main ingredient of seismic risk studies is the definition of the structural limit states, which is one of the most challenging topics since the historical structures rarely possess similarities among them while their response is characterized by complex interaction of structural components. This paper presents a scientific project funded to contribute to the mitigation of seismic risk in the historical peninsula of Istanbul where Eastern Rome, Byzantine, and Ottoman structures populate almost every street. A complete approach has been followed in the project, the main activities of which consist of creating a wide strong ground motion and ambient vibration network, building and testing large-scale specimens to define limit states of the masonry heritage structures and combining the monitoring an testing findings with analytical modelling tools. The project resulted in a Master Plan in which steps to be taken to protect the existing heritage buildings in the historical peninsula of Istanbul is proposed and discussed. NEED FOR A HOLISTIC APPROACH In parts of the world with a rich inventory of heritage structures, management, including intervention, of these structures has always been a challenge, especially for high levels of seismic hazard. Istanbul has experienced large magnitude earthquakes that caused tragic damages to the heritage building stock in the past (Bal et al., 2015). Unfortunately, decision for prioritizing the assessment and restoration of certain historical structures over others is commonly not based on a sound rationalized set of criteria, associated with technical and historical importance aspects, but is completely political, resulting in neglecting a number of historical structures that stay in obscurity despite their undeniable value. Funds are directed accordingly, without any optimization considerations though sources are limited, needs are immediate and ATC & SEI 2015 185