1,720,997 research outputs found
Basilica churches under seismic actions: Classification and non-linear behaviour of masonry macro-elements
No full textThe paper provides a contribution for the evaluation of seismic capacity of typical macro-elements of basilica type churches through non-linear static analyses. Previous studies conducted by the authors on the behaviour of masonry churches under the earthquake actions showed how these structures are particularly vulnerable to the horizontal loads due to their specific geometrical configuration, characterized by open plan, slender walls, lack of effective connections between transversal walls, thrusting structures. In this paper, fourteen basilica churches located in Central and Southern Italy are analysed by sub-structuring the whole building in its constituting macro-elements. Each macro-element is then analysed by using pushover analysis with the aim of determining its horizontal capacity and the corresponding failure mechanism. The comparison among the results of the seismic analysis allow for defining eight classes of macro-elements, each one characterized by peculiarity in geometric characteristics, in architectural function and seismic response
Validation of numerical results of complex seismic analysis through simple analytics
No full textThe paper analyzes the application of the numerical findings of the program, which is becoming increasingly difficult for civil and structural design. Since, as in many other countries, the verification of design using a software model is now required by current Italian codes as well. Given this, the structural engineer must provide a technical report using a licensed software tool, attached to other project documents to get the Seismic Authorization at the local Civil Engineering Department offices. Following a brief explanation of structural analysis methodologies, this study presents a criterion for assessing the applicability of numerical findings obtained using any structural software. Three case studies of this criterion are shown to demonstrate how to check them using simple manual calculations: (i) the normal stress in RC columns subjected to gravity loads; (ii) the periods of vibration, participating masses, and seismic base shear derived from dynamic modal analysis; and (iii) the main parameters characterizing the pushover curves of existing buildings. Finally, this work underlines the significance of confirming the application of numerical results obtained by software in civil and structural design. The offered criteria and scenarios exhibit realistic techniques to ensure accuracy and reliability in structural performance assessment, according to the structural requirements imposed by current codes in Italy and similar countries
Analytical modelling for the seismic assessment of pointed arches supported by buttresses
No full textThe seismic behaviour of arches is investigated to provide a contribution to the stability of arches with a pointed shape supported by buttresses. The limit analysis (LA) for masonry structures has been herein implemented in analytical modelling based on the use of nonlinear programming techniques for investigating the potential failure mechanisms associated with pointed arches under horizontal forces. A critical assessment of the positioning of hinges over the arch embrace is conducted here. This will allow for a better prediction of the capacity of these structures under seismic actions. The lateral action, which activates the investigated failure mechanisms, is also computed by implementing this new analytical model. This is assessed both in terms of horizontal loading multiplier and associated ground accelerations. Furthermore, by comparing numerical results derived from scientific literature, it was possible to validate the reliability of the here presented analytical model
Statics of buttressed masonry arches in light of traditional design rules
No full textThe mechanical behavior of masonry arches is governed by equilibrium not by strength. Consequently, the traditional design rules obey to geometrical parameters and relative ratios. In this framework, state of art rules developed up to 18th century by Leonardo, Alberti, Palladio, De La Hire, De Belidor, Mascheroni et al., as well as the design indications of treatises and handbooks of 19th and 20th centuries, consist of simple geometrical values to be assigned to the arch and supporting buttress in order to build safe arches under the acting force of gravity. The validity of these design rules is confirmed by the presence of many ancient arched structures that withstood the test of time. In the light of previous considerations, the paper aims at providing an overview of the design rules used in the past centuries for buttressed arches with circular outline and characterized by different angles of embrace. To this end, the state-of-art on the design of the least thickness required for the stability of circular arches is firstly discussed. The inherent design rules have been classified in three generations depending on time when they were formulated. Afterwards, the state-of-art rules for the design of buttresses supporting arches are illustrated and compared. The design indications are provided in terms of minimum thickness required for the stability of buttress carrying the actions (vertical loads and horizontal thrust) induced by the supported arch. The design rules for buttress are also classified into three classes depending on the used approach. The overall aim of this study is an historical rereading of the design rules conceived over the centuries for circular buttressed arches, which are here compared and summarized in diagrams allowing for an immediate understanding of the influence of geometrical parameters characterizing itself on its mechanical behavior
Proposal of a simple expression for predicting the horizontal capacity of masonry walls
No full textIn this paper, a simple expression for predicting the horizontal capacity of multistorey unreinforced masonry frames is proposed and discussed in the framework of limit analysis approach. To this aim, the panels of Convent of San Carlo all'Arena in Naples has been analyzed via nonlinear static analysis. The results have been compared with the values provided by the application of the proposed simple expressions, which only depend on geometrical parameters and external loads. The results show that the values obtained with the simplified formula are very close to the values obtained by pushover analysis, especially if higher compressive strength values are assumed, and the scatters assume greater values as the irregularity in the arrangement of the openings in the vertical and horizontal direction increases
Seismic capacity of buttressed masonry arches
No full textMasonry buttressed arches have been designed in the past for vertical actions deriving from gravity loads and horizontal actions determined by the thrust of the arch. Horizontal actions consequent to earthquake motions were not usually taken into account in the design of these structures. This, despite of the high vulnerability of such typology, frequently characterizing monumental buildings. This paper addresses the problem of the capacity of buttressed masonry arches with a circular shape and different angles of embrace, under horizontal actions induced by seismic motions. To this aim, in the framework of Limit Analysis for masonry structures, the seismic analysis of a large sample of buttressed arches is provided and discussed. The outcomes of numerical analysis have shown that the activated failure mechanisms change in presence of horizontal actions. The results of the analysed large sample are very consistent in terms of lateral capacity since the horizontal load multiplier increases with the thickness of the buttresses and decreases with the buttress slenderness. The paper provides an unexpected result for thin arches since in this case semi-circular arches become more vulnerable than segmental
Effect of panel zone on non-linear behaviour of mrfs in the light of seismic codes
No full textThis paper deals with a critical analysis of the current seismic design criteria provided by Eurocode 8 for Moment Resisting Frames. This approach is based on the capacity design principle, in which the design is governed by the strength and stability of the structural elements and by hierarchy ofstrength, this in order to allows development of high dissipative collapse mechanism. The drawbacks of this approach is that the maximum required inter-storey drifts, at service limit states, are not directly satisfied. This leads to an enlargement of geometrical dimensions of the elements, producing significant over-strength and nullifying the use of high behaviour factors. In this paper, an alternative design criterion is proposed. According to this the design is governed by maximum inter-storey drift at service limit state, whereas the satisfaction of capacity design rules is contextually verified. This means to design the structure with seismic actions corresponding toservice earthquakes (i.e. unitary q-factor). Linear and non-linear static analyses on 3, 6 and 9-storey steel frames were performed to compare the design methodologies in terms of push-over curves (i.e.over-strength), interstorey- drifts and collapse mechanisms. Furthermore, the effect of panel zone on the global seismic response of frames was taken into accountin the performed analyses. It has been properly modelled using one of the most diffused literature model, the so called Krawinkler's 'frame model', accounting both its elastic and plastic behaviour
A proposal for evaluation of seismic vulnerability of complex masonry building with additions: the case of Zoological Station Anton Dohrn
No full textNowadays, interest in the preservation of cultural built heritage is globally increasing. The assessment of seismic vulnerability of existing masonry buildings is a complex task as their morphological evolution is often characterised by transformations, aggregations, addition of structural portion to existing ones and modifications developed over centuries. In this paper the seismic vulnerability of the Zoological Station Anton Dohrn in Naples has been evaluated. It is a complex masonry building that includes six parts (the central part, West wing, East wing, two connecting parts and the library) built in different periods. Preliminary analysis, as the evaluation of geometric parameters (for example the ratio between the area of masonry walls and the geometric area), and nonlinear static analysis, by using the equivalent frame model, of central part and connecting parts, part A and B, respectively, have been carried out. Due to the complexity of the building, two hypotheses have been considered. The first hypothesis involves the analysis of the central part and the connecting parts as isolated structures, neglecting the interaction between the parts; the second hypothesis considers a perfect interaction between the parts that are analysed as a single structure. By discussing the results obtained, a proposal for the evaluation of the seismic vulnerability of complex masonry buildings with additions of structural portions is formulated
Complex monumental buildings. Definition of complexities and structural implications
No full textIn the present paper, the typical complexities of masonry structures are investigated and discussed throughout the case of San Carlo all'Arena Convent in order to underline their structural implications. It is a masonry building located in Naples that has a strong historical interest because of its different occupancy over time. It is part of an aggregate, with adjacent buildings with different height and a church. Located on a hill, the Convent case study is characterized by variable height and a rectangular plan with a courtyard. During its history, it was subjected to modifications, as the additions of parts in plan and of floors, and alterations, as openings which are often misaligned in vertical direction and are not characterized by the same sizes as the existing ones. For this reason, this masonry building allows the analysis of the typical complexities of masonry structures. Among these, the following will be highlighted: the evolution in the time, the interconnection among different constructions, addition of floors, the presence of different occupancy, foundations at different heights and the presence of alterations, as addition of openings. To discuss this issue, the complexities and their structural implications of San Carlo all'Arena Convent in Naples are analysed
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