Lauzacco, Italy
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Morandi P.,University of Pavia | Milanesi R.R.,UME School | Magenes G.,University of Pavia
Brick and Block Masonry: Trends, Innovations and Challenges - Proceedings of the 16th International Brick and Block Masonry Conference, IBMAC 2016 | Year: 2016

Within the European FP7 Project “INSYSME”, the research unit of the University of Pavia has conceived a new seismic resistant clay masonry infill system with the purpose of controlling damage in the masonry and reducing detrimental effects of the panel-frame interaction, through a combined use of sliding joints inserted in the masonry and deformable joints at the wall-frame interface. The idea behind the proposed solution stems from principles already implemented in the past, in particular with reference to work by Mohammadi et al. (2011) and Preti et al. (2012 and 2015). The originality of this solution stays in the adoption of different and innovative materials for the implementation of the flexible and sliding joints and in the experimental campaign, carried out on full scale reinforced concrete infilled frames and on a two-storey building, resorting to dynamic shaking table tests. In this paper, the principles behind the proposed system and the characteristics of the construction details and materials are defined, along with the available results of the mechanical characterization on the masonry. The first results of the experimental tests on single infilled frames are reported in the companion paper. © 2016 Taylor & Francis Group, London.

Sullivan T.J.,University of Pavia | Sullivan T.J.,European Center for Training and Research in Earthquake Engineering | Welch D.P.,UME School | Calvi G.M.,IUSS Pavia
Earthquake Engineering and Engineering Vibration | Year: 2014

The last decade or so has seen the development of refined performance-based earthquake engineering (PBEE) approaches that now provide a framework for estimation of a range of important decision variables, such as repair costs, repair time and number of casualties. This paper reviews current tools for PBEE, including the PACT software, and examines the possibility of extending the innovative displacement-based assessment approach as a simplified structural analysis option for performance assessment. Details of the displacement-based s+eismic assessment method are reviewed and a simple means of quickly assessing multiple hazard levels is proposed. Furthermore, proposals for a simple definition of collapse fragility and relations between equivalent single-degree-of-freedom characteristics and multi-degree-of-freedom story drift and floor acceleration demands are discussed, highlighting needs for future research. To illustrate the potential of the methodology, performance measures obtained from the simplified method are compared with those computed using the results of incremental dynamic analyses within the PEER performance-based earthquake engineering framework, applied to a benchmark building. The comparison illustrates that the simplified method could be a very effective conceptual seismic design tool. The advantages and disadvantages of the simplified approach are discussed and potential implications of advanced seismic performance assessments for conceptual seismic design are highlighted through examination of different case study scenarios including different structural configurations.

Welch D.P.,UME School | Sullivan T.J.,University of Pavia | Filiatrault A.,State University of New York at Buffalo
Bulletin of the New Zealand Society for Earthquake Engineering | Year: 2014

The seismic assessment of an existing building is often required, possibly due to a change in use, changes in legislation (as recently occurred in New Zealand), for insurance purposes or to permit continued occupancy following a major earthquake. This discussion paper explores three ways in which Building Information Modelling (BIM) could assist in the assessment and mitigation of seismic risk: (i) BIM could provide valuable data on characteristics of both structural and non-structural elements within a building to permit a reliable and holistic seismic risk assessment to be undertaken; (ii) administer a self-diagnosis process utilising damage information received from structural health monitoring technologies prior to and following an earthquake, thus reducing the need for potentially dangerous and time-consuming physical post-earthquake inspections; and (iii) enabling realisation of an emergency management hub within a building management system for implementing control processes to monitor and eventually shutdown damaged mechanical services (e.g. gas pipes) following an earthquake, thus limiting the negative consequences of earthquake induced damage. By providing a leading-edge discussion of these three subjects, with reference to building damage observed in previous earthquakes, important directions for research in BIM are identified that promise to provide a more effective means of seismic risk assessment and mitigation.

Beigi H.A.,University of Toronto | Christopoulos C.,University of Toronto | Sullivan T.J.,University of Pavia | Calvi G.M.,UME School
Earthquake Spectra | Year: 2016

Recently, the gapped-inclined brace system (GIB) has been developed as an effective retrofitting solution for soft-story buildings. This paper presents a cost-benefit study of a building retrofitted using the GIB system. A six-story, reinforced concrete (RC) frame with an open story at the ground level and masonry infills on all other floors is studied. To investigate the effectiveness of alternate retrofit configurations, different scenarios of GIB systems are numerically analyzed, expected repair costs for various levels of seismic intensity are computed, and cost benefit values are compared to each other and to those obtained when the building is strengthened and stiffened at the ground floor using conventional methods. Results show that GIB retrofit solutions are likely to represent significant cost benefits compared to traditional retrofit solutions. The results also indicate that GIBs do not need to be positioned at all column locations of the soft story, which could be beneficial in reducing the overall retrofit cost and improving architectural functionality of the retrofitted structure. © 2016, Earthquake Engineering Research Institute.

Agha Beigi H.,University of Toronto | Christopoulos C.,University of Toronto | Sullivan T.,University of Pavia | Calvi M.,UME School
Earthquake Engineering and Structural Dynamics | Year: 2015

This paper presents results from a numerical investigation into the seismic retrofit of a soft story frame using a novel gapped-inclined brace (GIB) system. The GIB system consists of a pinned brace and a gap element that is added to the first story columns of the frame. The inclusion of GIB elements in addition to increasing the lateral capacity of columns at the first story increases the post-yield stiffness ratio of the system and reduces the P-delta effects on the columns, while not increasing the first story lateral resistance or stiffness. This allows for the isolating benefits of the soft story to protect the upper floors of the structure from damage while avoiding excessive deformations and reducing the propensity for collapse. A six-story RC frame with masonry infills on all floors except for the first floor is studied. The dynamic response of the retrofitted building using the GIB system is investigated numerically and is compared with the response of the original un-retrofitted building and the same building in which masonry infills are added to the first story to mitigate the soft story response. Results from the nonlinear time-history analyses indicate that the GIB system could provide a reliable seismic retrofit mechanism for soft story buildings, which greatly reduces the likelihood of collapse by increasing the displacement capacity of the soft storey and by reducing P-delta effects, while minimizing the overall damage and losses in the building by taking advantages of the isolation that is provided by the soft story to the rest of the structure located above. © 2014 John Wiley & Sons, Ltd.

Agha Beigi H.,University of Toronto | Sullivan T.J.,University of Pavia | Christopoulos C.,University of Toronto | Calvi G.M.,UME School
Engineering Structures | Year: 2015

This paper examines the factors affecting the repair costs following major earthquakes, of reinforced concrete (RC) frame buildings with non-ductile detailing typical of construction practices in Italy and other parts of the world during the 1950s and 1960s. Two configurations of a RC frame structure, one with full infills and the other with partial infills, are numerically studied. Results of incremental dynamic analyses confirm that the partial infill RC structures, in which soft-story mechanisms form in the open story, are more likely to collapse. However, by undertaking a loss estimation study for different scenarios it is shown that the lower losses that are expected due to the reduced damage of non-structural components in upper levels could be an advantage of soft-story buildings provided that the collapse propensity is reduced at the first level. It is further shown that losses in soft-story buildings will be strongly affected by the repair value of the structural and non-structural components at the soft-story level relative to other levels and the magnitude of P-Delta effects. These observations indicate that an effective retrofit strategy, that would reduce both monetary losses and the probability of collapse, could be achieved by increasing the deformation capacity at the soft-story level without altering the isolating effect that the soft-story mechanism provides to the levels above and without any further intervention in the stories above. The changes in losses resulting from such a conceptual retrofit solution are presented in order to illustrate the merits of such an approach, that should therefore become the focus of future research. © 2015 Elsevier Ltd.

Mouyiannou A.,UME School | Rota M.,European Center for Training and Research in Earthquake Engineering | Penna A.,University of Pavia | Magenes G.,University of Pavia
Journal of Earthquake Engineering | Year: 2014

Performance-based earthquake engineering, developed over the last decades for the design and assessment of other structures, can also be applied for masonry structures if the particularities of masonry are incorporated into the procedure. According to this methodology, structural performance can be assessed according to damage states which are identified through displacement/damage indicators. While various methods for the identification of limit states from the results of nonlinear static analyses exist, the identification of damage states from the results of nonlinear dynamic analyses is still uncertain. This article investigates a number of criteria allowing to identify the attainment of significant limit states from the results of time history analyses, in terms of appropriately identified response quantities. These criteria are applied to five building prototypes and their results are compared. A comparison with the limit states derived from nonlinear static analyses is also made. © 2014 Copyright A. S. Elnashai.

Penna A.,University of Pavia | Rota M.,European Center for Training and Research in Earthquake Engineering | Galasco A.,University of Pavia | Mouyiannou A.,UME School
Computational Methods in Applied Sciences | Year: 2015

Despite being recognized as the most accurate analysis technique for the design and assessment of masonry structures, nonlinear dynamic analysis is not commonly used in the everyday engineering practice. Reasons for this can be found in the difficulties in the selection of appropriate input ground motion records, in the limited availability of computer programs allowing the performance of time history analysis, especially for the case of masonry structures, and in the issues related with interpretation of the results in terms of performance limits. Real records are well known to be a preferable choice with respect to artificial or synthetic ground motions, but the limited availability of real records often requires scaling them, with all the concerns associated with this operation. Also, a proper selection of seismic input requires some level of expertise, which is not so common in the professional field. Regarding numerical modelling of masonry buildings, an analysis tool capable of reproducing both global seismic response and local mechanisms would be the preferable option. Existing equivalent frame models including suitable nonlinear macro-elements representative of the behaviour of structural members allow performing time-history analyses of the global response of complete 3D building models. A modified macro-element model accounting for second order effects can be suitably adopted for the analysis of local failure modes, which are mainly associated with bending-rocking behaviour and out-of-plane wall response. © Springer International Publishing Switzerland 2015.

Fox M.J.,UME School | Stafford P.J.,Imperial College London | Sullivan T.J.,University of Pavia
Earthquake Engineering and Structural Dynamics | Year: 2016

Seismic hazard disaggregation is commonly used as an aid in ground-motion selection for the seismic response analysis of structures. This short communication investigates two different approaches to disaggregation related to the exceedance and occurrence of a particular intensity. The impact the different approaches might have on a subsequent structural analysis at a given intensity is explored through the calculation of conditional spectra. It is found that the exceedance approach results in conditional spectra that will be conservative when used as targets for ground-motion selection. It is however argued that the use of the occurrence disaggregation is more consistent with the objectives of seismic response analyses in the context of performance-based earthquake engineering. Copyright © 2016 John Wiley & Sons, Ltd.

Ntritsos N.,UME School | Ntritsos N.,National Technical University of Athens | Anastasopoulos I.,National Technical University of Athens | Anastasopoulos I.,University of Dundee | Gazetas G.,National Technical University of Athens
Geotechnique | Year: 2015

Results of a three-dimensional finite-element study for the effect of embedment on the undrained bearing capacity, the elastic stiffness, and the cyclic behaviour of square-in-plan foundations are presented. Uniaxial horizontal (Q) and pure-moment (M) limit loads, as well as the respective elastic stiffnesses (KHHand KMM) are obtained, and simplified models are developed to interpret the observed trends. The substantially different role of embedment in increasing elastic stiffness and in increasing ultimate loads is interpreted in simple soil mechanics terms. Extensive comparisons are made with the two-dimensional results for a strip foundation. Combined (QM) loading capacities are obtained and presented as ‘interaction’ diagrams; the significance of the vertical load (N) is also addressed. The importance of the type of contact between the foundation interfaces (vertical or horizontal) with the surrounding or underlying soil is explored. A substantial reduction in all capacities is shown when the interfaces are tensionless and of limited shear (sliding) resistance (TSI), compared with the capacities for the ideal case of fully bonded contact (FBC). The cyclic moment–rotation (M–θ) response of embedded foundations carrying a simple slender structure is investigated parametrically. It is found that the monotonic loading curves provide approximately the envelope for the cyclic M–θ loops. But the shape of these loops and the ensuing settlement of the foundation are both functions of the factor of safety (FSV) against vertical bearing capacity. In case of surface and shallowly embedded foundations with high values of FSV (i.e. with light loading or on very stiff soil) the loops pass nearly through the centre (M¼θ¼0) of the coordinate axes and the residual settlement is negligible; both are a consequence of the predominantly geometric non-linearity in the form of separation of the walls and uplifting of the base from the soil. On the contrary, with low FSV values (heavy loading or soft soil) and deeper relative embedment, broad hysteresis loops and accumulating settlement are the rule – a product of material inelasticity of the soil, under limited soil–foundation detachment. © 2015 Thomas Telford Ltd. All rights reserved.

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