24 research outputs found
Comendador Escrivá, Poesie. Edizione critica, introduzione e commento a cura di Ines Ravasini
No full textComendador Escrivá, one of the most significant voices of the late XV century, is author of a small collection of poems, rich in interesting cues and not lacking novelties if compared to the panorama of the Castilian courtly love poetry of that time. A native of Valencia, Escrivà lived and worked between the Levantine capital and Aragonese Naples, absorbing influences both from the Catalan and the Italian literary tradition: in his verse, in fact, the Castilian codified manner of speaking about love is blended with reminiscences of the allegoric prose of Roís de Corella’s Valencian circle and with some initial attempts to imitate Italian Petrarchism.
The critical edition if his works is accompanied by a linguistic and historical-literary comment, that aims at underlining the multiple influences featured in his production. The introductory study, apart from resuming and delving into the controversial question of the identification of the poet, sets the Comendador’s works in the frame of the cultural relationships between Italy and Spain, in a crucial moment in the history of Castilian lyrical tradition that prelude its great flowering in the XVI century
Application of an analytical method for the design for robustness of RC flat slab buildings
No full textNowadays the structural engineering community needs reliable and design-oriented methods for the design of low and medium-rise reinforced concrete (RC) buildings with regard to progressive collapse. In this context, the current work aims to validate and apply a new analytical method suitable for the design for robustness of RC buildings characterised by the presence of flat slabs falling in low and medium consequence classes. The analytical method presented in this study is an extension of a method recently proposed by some of the authors for the analysis of two-way slabs in which flexural capacity and punching and post-punching failure criteria are added to reproduce the ultimate behaviour of flat slabs. In this paper, the design for robustness is applied together with the design for ultimate and serviceability limit states in the framework of the partial safety factor method of verification for RC flat slabs. The analytical method is applied as a direct method to evaluate the level of robustness of RC flat slabs to sustain a localised failure simulated by considering an internal column removal scenario. First, the method is validated by comparing the analytical results with both experimental data available in the literature and nonlinear finite element results obtained by adopting a multi-layered shell element approach and the PARC_CL 2.0 crack model. The comparison of the results demonstrates the reliability of the analytical approach in reproducing the ultimate load and ultimate chord rotation of flat slabs with a good approximation by considering the effect of tensile membrane action (TMA). Second, in strategies based on unidentified accidental actions, the analytical method is used to carry out a parametric analysis in the context of an internal column loss scenario. The parametric analysis allows the level of robustness to be evaluated by varying the main geometrical properties that affect the failure mode, resistance and ductility of RC flat slabs. Finally, the paper presents—for a given span and span-to-depth ratio—the required reinforcement ratios, design load in the accidental load combination and ultimate chord rotation in the form of design nomographs useful for engineering
Nonlinear Dynamic Response of a Precast Concrete Building to Sudden Column Removal
No full textRobustness of reinforced concrete (RC) structures is an ongoing challenging research topic in the engineering community. During an extreme event, the loss of vertical load-bearing elements can activate large-deformation resisting mechanisms such as membrane and catenary actions in beams and floor slabs of cast-in-situ RC buildings to resist gravity loads. However, few studies have been conducted for precast concrete (PC) buildings, especially focused on the capacity of such structures to withstand column loss scenarios, which mainly relies on connection strength. Additional resistance resource and alternate load paths could be reached via tying systems. In this paper, the progressive collapse resistance of a PC frame building is analyzed by means of nonlinear dynamic finite element analyses focusing on the fundamental roles played by beam-to-column connection strength and tying reinforcement. A simplified modelling approach is illustrated in order to investigate the response of such a structural typology to a number of sudden column-removal scenarios. The relative simplicity of the modelling technique is considered useful for engineering practice, providing new input for further research in this field
Progressive collapse fragility of substandard and earthquake-resistant precast RC buildings
No full textSeveral natural and man-made disasters have highlighted that precast reinforced concrete (RC) buildings often
have insufficient levels of structural robustness, which is the last line of defence under extreme events. Even
though robustness studies were originated by the progressive collapse of the Ronan Point precast RC building in
1968, such a structural feature of disaster resilience has been partially investigated in case of precast RC
buildings to date. In this study, a precast RC frame structure representative of low-rise commercial buildings is
analysed under different column loss scenarios, which can produce the partial or total collapse of the structural
system. Two building classes are considered, namely, buildings designed only to gravity loads and buildings
designed for earthquake resistance. Structural robustness is probabilistically assessed through a fragility analysis
procedure, using three-dimensional fibre-based finite element models with nonlinear links simulating connections,
large-displacement incremental dynamic analysis, and multiple performance limit states for damage
assessment. The output of the study is threefold: (i) a detailed assessment of the effects of column loss on precast
RC frame buildings, quantifying the major role of structural detailing and beam-column connections; (ii) a
fragility-informed evaluation of beneficial effects of seismic detailing on structural robustness, which can drive
designers in retrofitting of existing precast RC buildings and decision-makers towards prioritization-related issues;
and (iii) the generation of typological fragility curves for progressive collapse risk assessment in both singleand
multi-hazard environments. Progressive collapse fragility curves can be convolved with more classical
fragility models describing the failure of single components (under, e.g., flow-type landslide impact, vehicle
collision or blast) and hazard, to assess systemic structural risk
Progressive collapse assessment of gravity-load designed European RC buildings under multi-column loss scenarios
No full textNatural and man-made disasters often produce the collapse of multiple structural members at the ground floor of
buildings, which may trigger a progressive collapse of the structure. Nonetheless, only a few experimental tests
and numerical studies have been carried out to assess the effects of multiple column loss.
In this paper, the progressive collapse capacity of gravity-load designed, reinforced concrete (RC) buildings
complying with Eurocode 2 is numerically investigated, considering both simultaneous and sequential removal
of ground-floor columns. The study focuses on a benchmark RC frame used in previous investigations on singlecolumn
loss scenarios, using nonlinear fibre-based capacity modelling and incremental dynamic analysis.
Progressive collapse capacity was evaluated at multiple structural scales, in terms of axial strains, beam drifts
and gravity load resisted by the structure after column loss. Analysis results allowed the quantification of both
load and drift capacities under varying relative location and deactivation times of removed columns, as well as
the control point. A comparison with numerical/experimental data highlighted that the sudden loss of two
consecutive columns can drastically reduce the load capacity, resulting in a progressive collapse of the RC
framed structure. A sequential loss of columns induced either positive or negative variations in load capacity,
depending on the ratio between removal times, whereas drift capacity significantly reduced in almost all cases
Bearing Capacity Assessment of RC Flat Slab Frame Structures
No full textAfter the Ronan Point partial collapse (1968), several design methods have been proposed in Technical Code and Guidelines to mitigate the progressive collapse phenomenon of reinforced concrete structures, such as Tying Force prescriptive rules and Alternative Load Path analysis. The latter is a direct method, where the capacity of the structure to sustain the applied loads after the loss of a loadbearing element is investigated. Two different approaches are used in this study to analyse the ultimate resisting mechanisms of reinforced concrete flat slab in case of a column loss scenario: 1) a simplified approach which consists of an analytical method developed in the framework of the strip method and that takes into the tensile membrane effect, 2) a detailed approach which consists of a finite element analysis using multi-layered shell elements where the nonlinear behaviour is evaluated using the PARC_CL 2.0 crack model, implemented in Abaqus Code as user subroutine. The aim of this paper is the progressive collapse assessment of a reinforced concrete flat slab frame structure by comparing the simplified and the detailed approaches with experimental data available in literature
Capacity assessment of uncorroded and corroded dapped‐end beams by NLFE and strut‐and‐tie based methods
No full textThe verification of dapped-end beams degraded by corrosion is a problem, especially for existing bridges in service. This paper proposes a nonlinear finite element (NLFE) modeling procedure and a simple strut-and-tie based procedure for predicting the response of dapped-end beams subjected to chloride corrosion. Firstly, the finite element modeling strategy, based on the adoption of multilayer shell elements and the PARC_CL 2.1 crack model is described. Then, the degradation effects on concrete, rebars, and steel-to-concrete interaction are defined as a function of the propagation period of corrosion. In particular, the effects of corrosion on the reinforcement are modeled by applying a reduction of tensile strength that considers for both the reduction of cross-section and the ultimate strain caused by pitting. Concrete splitting cracking due to volume expansion during rust formation is modeled by reducing the mechanical properties of concrete. Corrosion effects in steel-to-concrete interaction are modeled by applying a bond strength decay to the spring elements connecting corroded rebars-modeled with truss elements-and concrete multilayer shell elements. The proposed finite element procedure is used to study two scenarios based on different spatial distributions of corrosion-prone areas. Subsequently, a simplified analytical approach based on the strut-and-corroded tie method-called S&CT method-is proposed and compared with the finite element outcomes. Finally, the validations of the two proposed methods are presented with respect to a corroded dapped-end beam, showing that corrosion of rebars affects the resistance mechanisms of the dapped-end beam, by reducing both resistance and ductility. The proposed simplified analytical S&CT method provides conservative and safe results compared to the numerical NLFE model and to experimental data
SEISMIC ASSESSMENT OF EXISTING CIRCULAR HOLLOW RC PIERS SUBJECTED TO CORROSION THROUGH NLFEA
No full textThe capacity assessment of existing Reinforced Concrete (RC) bridges is a fundamental step to define rational intervention and retrofit strategies. Most of the Italian RC bridges date back to the second half of the last century and were therefore designed for gravity loads only or according to obsolete seismic codes, with inadequate structural detailing and poor-quality construction materials. The situation is further aggravated by aging and degradation over time, together with the limited maintenance level, which can lead to an increase in the seismic vulnerability of the infrastructure. Reinforcement corrosion is a major factor in the reduction of the seismic performance of RC bridges over time and can modify the expected failure mode of primary bridge components, such as piers. To investigate the effect of corrosion on RC piers, a non-linear finite element (NLFE) approach is presented in this work, based on the adoption of the PARC_CL 2.1 crack model, developed at the University of Parma, Italy, for RC elements subjected to cyclic loads and implemented as a user subroutine within the Abaqus FE package. Among the most remarkable features of the model stands out its capability to accurate simulate rheological phenomena, shear failures, reinforcement buckling, as well as the effects of corrosion on the structural response over time. The effectiveness of the proposed approach in the case of bridges is first proved through comparison with experimental data available in the literature on circular hollow RC piers. Finally, the model is applied to evaluate the time-varying capacity reduction of RC piers under aggressive environmental conditions, by considering the decay of the mechanical features and the role of rebars’ buckling
Capacity assessment of corroded reinforced concrete frames subjected to differential ground settlements
No full textDifferential ground settlements often cause serious structural damage in Reinforced Concrete (RC) buildings. The load capacity of RC buildings can be further reduced due to durability problems. Rein-forcement corrosion can produce a shift of the collapse mechanism from ductile to brittle modes. The aim of this work is to investigate the structural response of a typical Italian RC framed building from the ‘60s, under the combined effects of differential ground settlements and material degradation. To this end, nonlinear finite element analyses are performed at different assessment times, with consider-ation of different damage scenarios. The response evolution over time is described through significant structural parameters that can be easily monitored through SHM systems
Assessment of an Existing RC Frame Subjected to Differential Settlements using Nonlinear Finite Element Analysis
No full textThe paper concerns the assessment of a reinforced concrete frame subjected to uneven strong settlements.
The structure is representative of existing Italian residential buildings designed for gravity loads
only. Fibre-based nonlinear finite element models are developed, to evaluate structural performance
and damage propagation under increasing displacements. The results obtained from a simple, yet quite
common approach in progressive collapse analyses, based on a 2D model of a single frame, are compared
to the outcomes of 3D models of the whole structure, considering two different spatial layouts
for foundations. The contribution of secondary beams and foundation footing to the overall spatial stability
of the building is then quantified
