ROSE Programme

Lauzacco, Italy

ROSE Programme

Lauzacco, Italy
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Welch D.P.,ROSE Programme | Sullivan T.J.,University of Pavia | Calvi G.M.,IUSS Pavia
Journal of Earthquake Engineering | Year: 2014

Various loss assessment methodologies have been proposed and developed over the past decades to provide risk assessment on a regional scale. There is an increasing need, however, to provide engineers with practical tools for building-specific loss assessment. Recently, progress has been made towards probabilistic loss models such as the PEER framework. However, as comprehensive probabilistic methodologies could be too complex for practicing engineers, this article presents a simplified probabilistic loss assessment methodology that builds on a direct displacement-based framework. The methodology is tested via examination of two RC frame buildings and encouragingly shows similar results to the PEER methodology. © 2014 Copyright A. S. Elnashai.


Silva V.,University of Aveiro | Crowley H.,EUCENTRE | Varum H.,University of Aveiro | Pinho R.,University of Pavia | Sousa R.,ROSE Programme
Earthquake Engineering and Structural Dynamics | Year: 2014

The recognition of fragility and vulnerability functions as a fundamental tool in seismic risk assessment has led to the development of more and more complex and elaborate procedures for their computation. Although these functions have been traditionally produced using observed damage and loss data, more recent studies propose the employment of analytical methodologies as a way to overcome the frequent lack of post-earthquake data. The variation of the structural modelling approach on the estimation of building capacity has been the target of many studies in the past; however, its influence on the resulting vulnerability model for classes of buildings, the impact in loss estimations or propagation of the uncertainty to the seismic risk calculations has so far been the object of limited scrutiny. In this paper, an extensive study of static and dynamic procedures for estimating the nonlinear response of buildings has been carried out to evaluate the impact of the chosen methodology on the resulting capacity, fragility, vulnerability and risk outputs. Moreover, the computational effort and numerical stability provided by each approach have been evaluated and conclusions drawn regarding the optimal balance between accuracy and complexity. © 2013 John Wiley & Sons, Ltd.


Fox M.J.,ROSE Programme | Sullivan T.J.,University of Pavia | Beyer K.,Ecole Polytechnique Federale de Lausanne
Journal of Earthquake Engineering | Year: 2014

Capacity design aims to ensure controlled ductile response of structures when subjected to earthquakes. This article investigates the performance of existing capacity design equations for reinforced concrete coupled walls and then proposes a new simplified capacity design method based on state-of-the-art knowledge. The new method is verified through a case study in which a set of 15 coupled walls are subject to nonlinear time-history analyses. The article includes examination of the maximum shear force in individual walls in relation to the total maximum shear force in the coupled wall system, and subsequently provides recommendations for design. © 2014 A. S. Elnashai.


Fox M.J.,ROSE Programme | Sullivan T.J.,University of Pavia | Beyer K.,Ecole Polytechnique Federale de Lausanne
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2014

Reinforced concrete coupled walls are a common lateral load resisting system used in multi-storey buildings. The effect of the coupling beams can improve seismic performance, but at the same time adds complexity to the design procedure. A case study coupled wall building is designed using Force-Based Design (FBD) and Direct Displacement-Based Design (DDBD) and in the case of the latter a step by step design example is provided. Distributed plasticity fibre-section beam element numerical models of the coupled walls are developed in which coupling beams are represented by diagonal truss elements and experimental results are used to confirm that this approach can provide a good representation of hysteretic behaviour. The accuracy of the two different design methods is then assessed by comparing the design predictions to the results of non-linear time-history analyses. It is shown that the DDBD approach gives an accurate prediction of inter-storey drift response. The FBD approach, in accordance with NZS1170.5 and NZS3101, is shown to include an impractical procedure for the assignment of coupling beam strengths and code equations for the calculation of coupling beam characteristics appear to include errors. Finally, the work highlights differences between the P-delta considerations that are made in FBD and DDBD, and shows that the code results are very sensitive to the way in which P-delta effects are accounted for.


Nievas C.I.,ROSE Programme | Sullivan T.J.,University of Pavia | Sullivan T.J.,European Center for Training and Research in Earthquake Engineering
Bulletin of Earthquake Engineering | Year: 2015

While quite extensive research has been undertaken during the last decades to extend the direct displacement-based design (DDBD) method to a wide range of structural types and materials, it is recognized that there are still some areas requiring further study and development. Steel structures and, more specifically, steel moment resisting frames with setbacks are one of these and, therefore, this work aims to investigate the seismic response of such structures designed according to the DDBD procedure currently prescribed for regular frames and to elaborate specific recommendations based on the results obtained. The main aspects to be considered are the adequacy of the displacement profile and higher mode reduction factor to be used, as well as the suitable strength distribution required. In a trial application of the current DDBD procedure, two two-dimensional 12-storey frames with setbacks are designed, and the solutions obtained are used to develop models of the structures, which are then subject to a series of non-linear time-history analyses at increasing levels of intensity, using spectrum-compatible scaled accelerograms. The results obtained are contrasted with those of Karavasilis et al. (J Constr Steel Res 64:644–654, 2008), which were developed for steel frames designed via code methods. It is recognized that the DDBD method can benefit from the expressions developed by these authors, and recommendations for the adjustment of the DDBD higher mode reduction factors are subsequently proposed. The efficacy of the latter is evaluated by the design and verification at a range of diverse intensities of a set of two-dimensional frames of 6, 9 and 12 storeys, and satisfactory outcomes are obtained. These results have been fundamental in revealing the need for future research regarding the influence of the design spectral shapes, ductility demand and P-Delta instability in the dynamic amplification of drifts due to higher mode effects. © 2015, Springer Science+Business Media Dordrecht.


Brunesi E.,ROSE Programme | Brunesi E.,European Center for Training and Research in Earthquake Engineering | Bolognini D.,ROSE Programme | Bolognini D.,European Center for Training and Research in Earthquake Engineering | And 2 more authors.
Materials and Structures/Materiaux et Constructions | Year: 2015

Since eighties, 400 and 500 mm thick precast-prestressed concrete hollow core slabs, characterized by increasingly optimized cross-sections with non-circular voids, became very common. However, deeper slabs with long spans, which have to resist high line loads acting close to the supports, are subjected to initial web shear cracking and may fail at loads less than those predicted by traditional codes prescriptions. The shear strength capacity of these members without transverse reinforcement is evaluated through a campaign of detailed nonlinear finite element analyses, matching experimental test data collected from past programs. Constitutive models, based on nonlinear fracture mechanisms, are considered to numerically reproduce the experimental response of single span, simply supported, isolated hollow core units, highlighting web-shear failure mechanism, due to short development length and lack of transverse reinforcement. The adopted diffuse smeared fixed cracking constitutive model allows a reliable prediction of shear stress distributions and crack patterns for these members in their inelastic branch. The presence of a variable inclined strut is clearly evident. Peak shear stress is localized at the bottom side of the cross-section, rather than at the level of the centroid. The experienced brittle web-shear failure mechanism is governed by hollow core shapes with circular or non-circular voids, as evidenced by the evolution of the principal tensile strain distributions. Typically, less inclined, more rounded, diagonal crack, controlled by the smooth web width variation along depth, is opposed to a fairly constant variation of the fracture angle inclination, governed by the abrupt and irregular web width drop. © 2014, RILEM.


O'Reilly G.J.,ROSE Programme | Sullivan T.J.,University of Pavia
Journal of Earthquake Engineering | Year: 2015

A series of eccentrically braced frames (EBF) are designed and subjected to nonlinear analyses to highlight ambiguities and differences in current seismic design provisions for EBF structures. This provides motivation to implement better guidance for the checking of local displacement demand considerations and move towards a displacement-based design approach. A recently proposed direct displacement-based design (DDBD) procedure for EBFs is then described and further developed in this article through the calibration of a spectral displacement reduction factors that relate the displacement of an inelastically responding structure to that of the equivalent linear representation used in the DDBD of EBFs. Such an expression is calibrated as part of this study using an experimentally validated numerical model also proposed here for the EBF links such that the actual hysteretic behavior of the links is well represented. The DDBD guidelines are applied to EBF systems from 1–15 stories in height and their performance is verified via nonlinear dynamic analyses using two different sets of design spectrum compatible ground motions. The results of the study indicate the robustness of the proposed DDBD method in limiting the interstory drifts to design limits for a variety of EBF systems with short links, thus demonstrating that the proposed DDBD method is an effective tool for seismic design of EBFs. © 2015, Taylor & Francis. All rights reserved.


O'Reilly G.J.,ROSE Programme | Sullivan T.J.,University of Pavia
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

This paper investigates the importance of numerical modelling decisions on the seismic assessment of reinforced concrete (RC) structures typical of construction practice in Italy prior to the introduction of seismic design codes in the 1970's. In particular, means of accounting for the formation of a shear hinge in the beam-columns, longitudinal reinforcement slippage due to the use of smooth bars with end-hooks, and the strength and stiffness degradation associated with the lapping of longitudinal reinforcement in beam and column member end zones are discussed. A numerical model is validated by developing existing models in the literature capable of representing such behaviour and comparing with results obtained from quasi-static cyclic testing of a three storey RC frame. A case study structure designed using design provisions employed in Italy prior to the 1970's is then analysed via a series of dynamic analyses using ground motions representative of seismic hazard in Italy. An assessment of the structures is conducted at different return periods to determine the median storey drift and peak floor accelerations, as these demand parameters are typically used for refined performance assessment studies. For the considered structure, a number of cases are considered, where various modelling parameters are included or excluded to highlight the influence of each of these on the overall response of the structure. From this study, the importance of different numerical modelling decisions on the seismic assessment of pre-1970s' RC construction in Italy is highlighted and recommendations are provided for the modelling of phenomena critical to the seismic performance assessment process.


Fox M.J.,ROSE Programme | Sullivan T.J.,University of Pavia
Earthquake Engineering and Structural Dynamics | Year: 2016

A procedure for incorporating record-to-record variability into the simplified seismic assessment of RC wall buildings is presented. The procedure relies on the use of the conditional spectrum to randomly sample spectral ordinates at relevant periods of vibration. For inelastic response, displacement reduction factors are then used to relate inelastic displacement demand to the spectral displacement at the effective period for single-degree-of-freedom systems. Simple equations are used to convert back and forth between multi-degree-of-freedom RC wall buildings and equivalent single-degree-of-systems so that relevant engineering demand parameters can be obtained. Consideration is also given to higher-mode effects by adapting existing modal combination rules. The proposed method is applied to several case study buildings, showing promising results in the examination of inter-storey drift ratio and shear forces. The proposed method captures the variation in the distribution of structural response parameters that occurs with variations in structural configuration, intensity, engineering demand parameter of interest and site characteristics. Discussion is provided on possible ways to improve the accuracy of the procedure and suggestions for additional future work. © 2016 John Wiley & Sons, Ltd.


O'Reilly G.J.,ROSE Programme | Sullivan T.J.,University of Pavia
Earthquake and Structures | Year: 2016

Eccentrically braced frames (EBFs) represent an attractive lateral load resisting steel system to be used in areas of high seismicity. In order to assess the likely damage for a given intensity of ground shaking, fragility functions can be used to identify the probability of exceeding a certain damage limit-state, given a certain response of a structure. This paper focuses on developing a set of fragility functions for EBF structures, considering that damage can be directly linked to the interstorey drift demand at each storey. This is done by performing a Monte Carlo Simulation of an analytical expression for the drift capacity of an EBF, where each term of the expression relies on either experimental testing results or mechanics-based reasoning. The analysis provides a set of fragility functions that can be used for three damage limit-states: concrete slab repair, damage requiring heat straightening of the link and damage requiring link replacement. Depending on the level of detail known about the EBF structure, in terms of its link section size, link length and storey number within a structure, the resulting fragility function can be refined and its associated dispersion reduced. This is done by using an analytical expression to estimate the median value of interstorey drift, which can be used in conjunction with an informed assumption of dispersion, or alternatively by using a MATLAB based tool that calculates the median and dispersion for each damage limit-state for a given set of user specified inputs about the EBF. However, a set of general fragility functions is also provided to enable quick assessment of the seismic performance of EBF structures at a regional scale. © 2016 Techno-Press, Ltd.

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