1,721,077 research outputs found
The Rolling Shear Influence on the Out-of-Plane Behavior of CLT Panels: A Comparative Analysis
No full textEffect 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
Seismic Retrofit of Existing Masonry Buildings through Inter-story Isolation System: A Case Study and General Design Criteria
No full textThis paper investigates the potentials of inter-story isolation systems (IIS) for retrofitting irregular masonry buildings by means of an isolated vertical addition realised on the roof of the existing structure. By assuming a case study, a wide parametric analysis is firstly carried out on lumped-masses model for identifying the dynamic properties of the isolated superstructure that minimizes the global seismic response. Hence, a 3D FE model is adopted for the detailed design and analysis of the IIS structure, with different solutions, in order to regularize the global seismic response of the IIS complex. Finally, some general design criteria are suggested
AN INSIGHT ON THE ROLE OF THE DESIGN PROCEDURES ON DAMAGE TOLERANCE AND COST OF CLT BUILDINGS IN SEISMIC AREAS
No full textPhysical characteristics of timber as a construction material offer a high-performance option for the design and erection of buildings in seismic-prone area. Massive Cross-Laminated Timber (CLT) buildings represent a vehicle to increase the building sustainability and a robust workaround to heavyweight constructions. This paper is intended as a contribution in the reviewing the most common design procedures for the seismic design of CLT buildings and their implications on structural features and technological solutions, focusing the attention particularly on overall seismic performance, damage tolerance, construction costs and environmental impact. As a starting point of a more comprehensive study, the assessment is made with reference to a real building, which is representative of a wide class of buildings recently designed and erected in many Italian regions exposed to low and moderate seismic hazard. As a common reference, the analysis has been carried out according to a two-dimensional model of the panels, assumed to be elastic, varying the type of connections at the base, the presence of pre-stressing steel bars for rocking control and of dissipative devices. The main outcomes of the study can be summarized as follows: (i) the structural seismic behavior of CLT buildings is significantly influenced by the structural schemes adopted for walls and connections; (ii) construction costs and environmental impact decrease when enhanced design procedures are used
Role of perpendicular to grain compression properties on the seismic behaviour of CLT walls
No full textIn-plane seismic behaviour of Cross-Laminated Timber (CLT) walls is influenced by panel-to-panel and panel-to-foundation mechanical connections, which consist of hold-downs and angle brackets. Due to the platform constructional technology, the orthogonal to grain timber-to-timber contact is also involved in the seismic response of the panels. To date, literature theoretical approaches to evaluating the flexural load-bearing capacity of CLT panels focus their attention on the schematization of hold-downs and angle brackets only, under evaluating the role of timber compressed in the perpendicular direction. In this paper the influence of orthogonal to grain timber properties on the overall seismic behaviour of CLT walls has been investigated, proposing a general theoretical model to schematize the panel-to-panel and panel-to-foundation connections. A parabola-rectangle constitutive behaviour has been defined to describe the orthogonal to grain timber behaviour in the connection zones, while hold-downs and angle brackets are modelled adopting literature models. Five different failure conditions, described by mathematical formulations, able to describe the entire axial force-bending moment interaction domain have been defined. The proposed model has also been employed to schematize the connection zones in multi-storey CLT walls with openings, allowing to investigate the effect of the orthogonal to grain properties on its seismic behaviour. Results of nonlinear analyses demonstrate a significant influence of orthogonal to grain timber properties on seismic behaviour of the walls, affecting their strength, stiffness, ductility and collapse mechanisms
Non-linear FE Modelling of UR Masonry Buildings: Shear-Flexural Behaviour of Piers and Spandrels
No full textNumerous studies focus on analysing the dynamic behaviour of URM buildings under horizontal forces and interpreting potential in-plane collapse modes. Understanding the mechanical behaviour of masonry structures remains challenging due to their intrinsic heterogeneity and the various possibilities of material combinations. Consequently, the modelling phase becomes crucial for seismic vulnerability assessments of masonry buildings, particularly concerning differences in the shear-flexural behaviour of piers and spandrels. In this paper, after briefly reviewing the Equivalent Frame (EF) and Finite Element (FE) approaches, simple masonry elements such as piers have been modelled using these methods under various loading and constraint conditions. By comparing the results obtained issues related to shear behaviour were detected. All models were developed in SAP2000 using two different approaches: lumped-plasticity and distributed-plasticity. Notably, the software automatically defines shear behaviour based on flexural behaviour without offering modification options. Therefore, a simplified method for primally considering the shear collapse is proposed. By analysing the stress-state due to vertical loads and evaluating the strength domain of the analysed pier, a layered shell element section with appropriate geometric and mechanical properties can be defined for the pier, based on internal equilibrium conditions. This approach permits determining the minimum strength value for the modelled pier basing on its strength domain, considering the predominant behaviour (either shear or flexure) and enabling visualization of the related deformed shape. Comparisons between theoretical and numerical results are provided with the aim of better calibrating the proposed method
Campioni lignei estratti da travi in castagno antico: studio sperimentale e caratterizzazione meccanica
No full textOpen issues on non-linear modelling for seismic assessment of existing masonry buildings
No full textThe difficulties on the assessment of the seismic capacity of existing masonry buildings through non-linear FEM analyses have been examined in this paper, in the framework of the equivalent frame modeling. A significant problem lies in identifying an adequate equivalent frame idealization of the walls, i.e., capable of providing an acceptable response of the numerical model. Indeed, the geometrical complexity characterizing real masonry buildings, often due to irregular distribution of the wall openings, leads to choices and expedients which are impossible to codify and may only be defined on a case-by-case basis. Consequently, an adequate engineering judgment, which must obviously be considered when the results are being interpreted, is required. Linear and non-linear analysis were adopted on equivalent frame schemes of existing walls highlighting the problems of identifying geometric patterns, as well as defining the mechanical model of the spandrels or the influence of connection degree between orthogonal walls on the seismic behavior. In this paper some possible solutions to the problems are proposed, also with reference to specific study cases
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