442 research outputs found
Seismic performance of Nepalese schools: A full-scale test of a typical unreinforced masonry wall
No full textThis paper presents the preliminary results of an experimental investigation on the seismic performance of a large-scale typical Nepalese school URM wall. Hence, it proposes a retrofitting method for its strengthening. The test subjected a 5m x 3m masonry brick wall, set in 1:6 cement–sand mortar, to a two-way ramp cyclic loading to determine shear cracking failure. The results show that the wall exhibited a Grade 2 type of failure that indicates a slight structural damage with both diagonal and horizontal cracks, at 4mm displacement loading, in the mortar joints. The failure pattern is similar to those obtained in similar works in the literature
Experimental qualification of seismic strengthening of URM buildings in Nepal
No full textNepalese buildings are typically constructed using unreinforced masonry (URM) as the lateral load-bearing system. In the 2015 Nepal Gorkha earthquake several URM buildings suffered heavy damage. The limited economic resources available in the country and the challenge of strengthening a large portfolio of buildings highlight the need for low-cost retrofitting techniques. This paper presents a large-scale experimental campaign aimed at quantifying the seismic performance of a typical URM wall when strengthened with splints and bandages. This represents one of the retrofit techniques that are most widely-used in Nepal. A 5 × 3 m URM wall was constructed using 1:6 cement–sand mortar as per the mechanical properties identified by material testing in Nepal. The URM wall was tested under a two-way ramp cyclic loading. Typical crack patterns associated with URM were observed. The wall was subsequently retrofitted with 8 mm rebars as splints and bandages and tested to failure. The results show that the strength of the retrofitted wall is almost twice that of the URM wall. The observed crack damage improved from EMS-98 Grade 2, with horizontal and diagonal shear cracks in the mortar bed, to Grade 1, with hairline cracks on the rendered splints and bandages. Overall, the experiment demonstrated the efficiency of this practical, low-cost retrofitting technique that is tailored to traditional Nepalese URM buildings. This work can be used to advise local stakeholders in the construction industry as well as to act as a benchmark to improve the reliability of fragility functions for URM buildings in Nepal
Appendix_A – Supplemental material for The SAFER geodatabase for the Kathmandu Valley: Geotechnical and geological variability
No full textSupplemental material, Appendix_A for The SAFER geodatabase for the Kathmandu Valley: Geotechnical and geological variability by Charlotte EL Gilder, Rama Mohan Pokhrel, Paul J Vardanega, Flavia De Luca, Raffaele De Risi, Maximilian J Werner, Domniki Asimaki, Prem Nath Maskey and Anastasios Sextos in Earthquake Spectra</p
Efficiency of alternative intensity measures for the seismic assessment of monolithic free-standing columns
No full textThis paper deals with the dynamic response of a free-standing ancient column in the Roman Agora of Thessaloniki, Greece as a means to shed more light on the complex behaviour of rocking bodies under seismic excitation. Numerical analyses utilizing discrete element method were carried out with the use of multiple seismic records selected based on the disaggregation of the seismic hazard for the region of interest. To identify their impact on structural performance, earthquake Intensity Measures, such as Peak Ground Acceleration and Peak Ground Velocity are examined for the case of a column that sustained no visible permanent deformations during the Ms=6.5 Thessaloniki earthquake of 1978. The analysis revealed a weak correlation of PGA and PGV with the response results and a significant influence of the mean frequency (fm) of the seismic motion. No coupling was found between the maximum displacement of the top during the oscillation and the permanent post-seismic deformations. The complementarity of both earthquake Intensity Measures in the structural vulnerability assessment is also depicted
Seismic design and demand assessment of isolated and innovative timber lateral load resisting systems
No full textThis dissertation examines the seismic design and demand assessment of isolated and innovative timber lateral load resisting systems for buildings. The dissertation begins by examining the optimal stories of installation and the effective stiffness and damping properties of a single and multiple isolation layers installed at a case study building, using an Inter-Story Isolation (ISI) configuration. As result of this study, the optimal stories of installation of the isolation layers are identified and the decrease in response with increasing the number of isolation layers is quantitatively assessed. Then, a framework is presented for conducting seismic reliability analysis using a multi-fidelity surrogate model. The presented approach features an expensive high-fidelity model and a cheap low-fidelity model and it is illustrated for an example base-isolated building. The multi-fidelity approach provides good accuracy in assessing the probability of failure of the system by utilizing only minimal high-fidelity model evaluations.
Next, the dissertation investigates the design and seismic demand assessment of innovative timber lateral-load resisting systems. First, a novel dual system is examined, comprising a Light Timber Frame (LTF) which is equipped with friction connections and coupled to a rocking Cross-Laminated Timber (CLT) wall equipped with self-centering hold-downs. LTF works as the energy-dissipating sub-system or fuse, while CLT helps in imposing a uniform drift distribution throughout building elevation and in self-centering the system at the end of the seismic event. The dissertation closes by examining the effect of Soil-Structure Interaction (SSI) and frequency dependence of soil-foundation dynamic behavior on the seismic demand of CLT walls coupled with dissipating connectors. The effect of SSI is shown to be significant for a five-story coupled CLT wall frame founded on heterogeneous soil with a soft upper layer.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat
Experimental Seismic Assessment of the Effectiveness of Isolation Techniques for the Seismic Protection of Existing RC Bridges
No full textThe seismic vulnerability assessment of existing and new lifeline systems, especially transportation systems, is becoming of paramount importance in resilient social communities. Unfortunately, the transportation systems, especially in Italy, were mainly built in the late 60’s and early 70’s and were designed primarily for gravity loads. As a result, most of the reinforced concrete (RC) bridges do not employ seismic details and their structural performance has often been found to be inadequate under earthquake strong motions. In addition, existing seismic codes of practice, especially in Europe, do not contain specific guidelines for the reliable assessment of existing RC bridges.
The present chapter illustrates the outcomes of two recent experimental seismic performance assessment carried out on typical portal frames and single columns existing reinforced concrete (RC) bridge designed for gravity loads only. The experimental response has been assessed by means of pseudo-dynamic and shake table testing. Intervention schemes employing innovative materials and technologies have also been considered as retrofitting measures to mitigate the onset of damage. The comprehensive experimental investigations prove the effectiveness of the isolation systems in preventing damage in the RC piers, especially limiting the maximum shear at the base of the piers, lowering the lateral drifts, preventing the onset of plastification in the frame sections and inhibiting the occurrence of the shear failure in the transverse beams of the RC portal frames of the pier
Data Set of PLOS Computational Paper PCOMPBIOL-D-18-02181R1
No full textFigures Data of PLOS Computational paper:Modeling of the axon plasma membrane structure and its effects on protein diffusionAuthors: Yihao Zhang, Anastasios V. Tzingounis, and George LykotrafitisCorresponding Author: George Lykotrafitis, Ph.D.University of ConnecticutStorss, CT UNITED STATES</div
Effect of spatial variability of seismic motion, local site conditions and soil-structure interaction on the inelastic dynamic analysis of rc bridges
No full textDuring strong ground motion, it is expected that bridge structures are subjected to excitation that is spatially variable along their longitudinal axis in terms of amplitude, frequency content and arrival time, a fact primarily attributed to wave passage, loss of coherency and local site conditions. Furthermore, the foundation interacts with the soil and the superstructure, thus affecting the dynamic response of the bridge. Towards this direction, a comprehensive methodology that couples the above phenomena is proposed and the computer code ASINC (Asynchronous Support Input Calculator) is developed. For the generation of spatially correlated seismic motions, the code combines the simulation formula proposed by Deodatis (1986) with a site response analysis of damped multiple-layer soil profiles laying on an elastic bedrock. The motions are then filtered in order to account for the kinematic interaction between the foundation and the surrounding soil, whereas the complex dynamic impedance matrix is derived depending on the foundation type and the potential pile-to-pile interaction (Makris and Gazetas 1992). In order to account for the development of a plastic hinge at the base of the RC pier section, the corresponding rotational springs are further modified (Kappos and Sextos 2001). Having obtained different time histories and spring-dashpot systems for all the support points, inelastic dynamic analysis of the bridge can then be performed with the use of any commercial finite element code, without the requirement of complex soil-structure modeling and special inelastic features. In order to check the reliability of the methodology and code developed, extensive tests were performed for all stages of the proposed process, utilizing complementary finite element analysis, use of alternative computer codes, previous research studies and closed-form solutions, where available. Moreover, two direct comparisons were performed in terms of both seismic input and structural response. In particular, the proposed approach was tested against a) recorded data available at Euroseis-test, a densely instrumented and geophysically well-investigated valley located in the Volvi basin, near Thessaloniki, Greece (Raptakis et al. 2000) and b) the effect of such an asynchronous input on a 300m length bridge studied within the framework of a research project in support of Eurocode 8. The results in both cases show satisfactory agreement and together with the tests carried out at successive analysis stages establish a level of confidence for use of the code parametric analyses and seismic design. Having developed and validated the computer code ASINC for the generation of suitably modified ground motion suites and spring-dashpot foundation systems at each support point of a bridge, an extensive parametric analysis scheme is applied. For that purpose, a well-studied bridge structure (Calvi and Pinto 1996) was considered, consisting of four 50m spans supported on three hollow section piers of unequal heights that vary from 7 to 21m and are designed according to Eurocode 8. The bridge is assumed to be founded on a multi-layer subsoil structure through a 2x2 pile group at each support location and is excited in the transverse direction by the Kallithea record obtained during the 1999 Athens earthquake, scaled to a PGA of 0.24g. Various scenarios are constructed incorporating different combinations of site effects, spatial variability and soil-structure-interaction phenomena, all used as an input for the inelastic dynamic analysis of the bridge. The parametric analysis also involves alternative bridge models in terms of structural system (fundamental period, overall and span length, boundary conditions, pier-deck connection and foundation flexibility). The results are being compared with the superstructure action effects of an elastic fixed base bridge structure that is excited synchronously. The above set of parametric analyses targets to highlight (a) the importance of including/neglecting the spatial variability, site effects and soil-structure-interaction in the inelastic dynamic analysis of bridges (b) their relative effect when they are all included in the analysis and (c) the feasibility of applying the proposed methodology within the context of current practice and code provisions. The results indicate that all the aforementioned phenomena could, under certain circumstances, have a significant role in the modification of the earthquake input motion as well as on the structural response of the bridge itself. Furthermore, they confirm the critical role played by local site conditions either in terms of overall motion amplification or as a source of variability when they substantially differ among the support points (Zerva 1999, Saxena et al. 2000). It is also concluded that the response of the bridge is strongly affected by asynchronous motion, especially with respect to higher modes excitation, increase of the pseudo-static component of the response and potential increase of the relative displacements. Notwithstanding the difficulties to draw general conclusions for such a multiparametric problem, the parametric study contributes to the identification of the extreme cases where the above effects are clearly beneficial or detrimental, while it illustrates the applicability of the overall methodology towards a more comprehensive design process
The state of modern Greek language as spoken in Victoria
No full textDeposited with permission of the author. © 1986 Dr. Anastasios TamisThis thesis reports a sociolinguistic study, carried out between 1981 and 1984, of the state of the Modern Greek (MG) language in Australia, as spoken by native-speaking first-generation Greek immigrants in Victoria. Particular emphasis is given to the analysis of those characteristics of the linguistic behaviour of these Greek Australians which can be attributed to the contact with English and to other environmental, social and linguistic influence. (For complete abstract open document
ICT applications for new generation seismic design, construction and assessment of bridges
No full textThis study focuses on the recent advances in information and communication technologies (ICTs) and their applications in the seismic design, construction and assessment of bridges. It aims to review and critically demonstrate advanced numerical analysis methods, open source finite element programs, web-based engineering tools, decision-making systems, collaborative on-site and remote research tools, frameworks for hybrid simulation, data and metadata dissemination and archiving, wireless data transmission and structural health monitoring, as well as earthquake-specific geographical information system applications; all developed and implemented recently, in order to enhance our understanding regarding the response of bridges under earthquake loading and thus, ultimately, mitigate seismic risk. The study concludes with the current research needs and challenging opportunities in integrating the current technological advancements in modern seismic codes and construction practice.</p
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