Extracorporeal Membrane Oxygenation Support as Treatment for Early Graft Failure After Heart Transplantation

Early graft failure (EGF) is a major risk factor for death after heart transplantation (Htx) accounting for >40% of deaths within 30 days postoperatively. According to the last International Society for Heart and Lung Transplantation (ISHLT) consensus statement, the graft dysfunction (GD) is to be classified into primary (PGD), in case of an unknown triggering factor or secondary (SGD) where there is a discernible cause such as acute rejection, pulmonary hypertension, or known surgical complications. The diagnosis of GD is to be made within 24 h after completion of Htx surgery and a severity scale for GD should include mild, moderate, or severe grades based on specified criteria. Mechanical circulatory support (MCS) for GD should be considered when medical management is not sufficient to support the newly transplanted graft. Currently, extra‐corporeal membrane oxygenation (ECMO) is widely accepted as treatment of severe EGF, given its easy and quick setup, the system versatility, the optimal end‐organ perfusion provided, and the possibility of both biventricular and lung assistance by usage of a low‐cost single pump

Analisi teorico-sperimentale di solette in calcestruzzo armato con barre di FRP soggette ad incendio

La ricerca presentata in questa tesi ha esaminato l’aspetto della resistenza al fuoco di solette di calcestruzzo armate con barre o griglie di FRP non protette da materiali protettivi (sistemi di protezione passivi, costituiti da intonaci normali o da materiali isolanti speciali) ma dalla presenza del solo ricoprimento di calcestruzzo. La ricerca ha previsto sia attività sperimentali su campioni ed elementi strutturali in scala reale, sia analisi teoriche per l’elaborazione di modelli meccanici interpretativi e di metodiche semplificate per la valutazione della capacità portante in condizioni di incendio di solette armate con barre di FRP. Le analisi condotte hanno consentito di individuare i principali parametri influenti e di suggerire metodiche di progetto/verifica semplificate e soluzioni tecniche, utili anche per la messa a punto di eventuali linee-guida sull’argomento

The influence of fire scenarios on the structural behaviour of composite steel-concrete buildings

Fire Safety Engineering can be defined as a multi-discipline based on the application of scientific and engineering principles to the effects of fire in order to reduce the loss of life and damage to property by quantifying the risks and hazards involved and provide an optimal solution to risk mitigation. The correct identification of fire scenarios is the central stage in the process of the structural fire design. A design fire scenario is the description of the spread of a particular fire with respect to time and space. In the process of identification of design fire scenarios for the structural fire safety check, all fires must be assessed realistically, choosing those most severe for the structural response. This paper is devoted to evaluate the influence of fire scenarios on the structural behaviour of composite steel-concrete buildings. In order to that, an office building subjected to different fire scenarios was considered. In particular the fire scenarios were defined by both standard fire (prescriptive approach) and natural fire (performance approach). Finally, a comparison between the prescriptive approach and the FSE approach is presented

Calibration of a simplified method for fire resistance assessment of partially encased composite beams

Purpose-This paper aims to deal with the evaluation of the bending moment resistance of partially encased composite beams, heated from below by the standard-time temperature curve (ISO 834). Design/methodology/approach-EN 1994-1-2 provides two calculation models for evaluating the sagging and hogging moment resistance: the "general simplifed rules" and the "simplifed models" proposed in the Annex F. Findings-In this paper, these simplifed calculation models were implemented on several partially encased composite beams, by means of a parametric analysis. Then, the results were compared to those obtained through an advanced calculation model, such as the Moment-Curvature model, by means of a comparative analysis. Originality/value-The aim of the "parametric-comparative" analysis is the evaluation of the reliability of the Annex F simplifed models. This analysis was conducted by means of both numerical-numerical and numerical-experimental comparisons. This paper provides an alternative simplifed calculation model, which is easy to implement and very reliable

Application of criteria for selecting fire scenarios for structures within fire safety engineering approach

This paper deals with a crucial aspect of the application of Fire Safety Engineering (FSE), which is the definition of fire scenarios and the choice of the design ones for structures. FSE requires, moreover, the choice of performance levels, fire models and, generally, advanced thermo-mechanical analyses. The number of possible fire scenarios is usually too large and the analysis of each one is not practicable. Therefore, the design fire scenarios should be chosen, in order to analyse the most severe cases for the structure. The choice of the design fire scenarios could be carried out through two possible procedures, shown in this paper: a) the Fire Risk Assessment (FRA), whereby a proper estimation of the Risk associated to each fire scenario is conducted; b) the procedure proposed in EN1991-1-2 (Annex E), whereby a single group of design fire scenarios is defined, taking into account the phenomena capable to modify the fire development, by introducing some coefficients in the calculation of the fire density load. In this paper, the main concepts of the two methodologies are shown and discussed and a comparison is proposed referring to a case study, inspired to an existing office building

Thermo-mechanical analysis of steel columns using different finite element types and constitutive laws

Application of advanced calculation models requires special attention by the designer to the computing the software capacity and reliability and the type of finite element adopted for the structural model. Obviously the type of finite element (FE), used in the analyses, as well as the modelling of the thermo-mechanical properties, influence the analyses results. The proposed benchmark describes the comparison among analyses results performed for a tubular steel column in case of fire, which is modelled through the software STRAUS7 by using 1D (“beam”), 2D (“plate”) and 3D (“brick”) finite element. The analyses are carried out by adopting a simplified constitutive law of steel at high temperature, characterized by an elastic-perfectly plastic curve without hardening. In addition, in order to evaluate the influence of this simplified constitutive law on the analyses results, the 3D finite element model is also analysed through the software ABAQUS/Standard, in which the constitutive law of steel at high temperature is modelled according to Eurocode 1993-1-2

Influence of joint modeling on fire behaviour of steel frame structures

In this paper the comparisons between the analyses results of steel frame structure exposed to fire, carried out through SAFIR2011 and STRAND7 (or STRAUS7), are shown in order to perform a benchmark study between software, in which two different constitutive laws are implemented. Moreover, the analyses results of 1D and 3D Finite Element Models are shown, including or less joints model, in order to evaluate the influence of joint behaviour on global structural behaviour

Behaviour of FRP Reinforced Concrete Slabs in Case of Fire: Theoretical Models and Experimental Test

Several technical codes allow concrete structures reinforced with FRP to be designed, but few calculation models taking account of fire condition are available. Assuming that the anchoring of the reinforcement is ensured in cooler zones of the structure, a calculation procedure developed by authors allows the flexural capacity of the one-way FRP reinforced concrete slabs under fire conditions to be assessed. The procedure was used for the design in the fire situation of six concrete slabs reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. Such slabs were tested in case of fire by exposing them to heat in a furnace according to 150834 standard time temperature curve: four slabs have been tested under typical design loads in fire situation and two unloaded slabs have been tested after the cooling phase in order to evaluate their residual resistance. The experimental results confirmed that the effects of the high temperatures on both the deterioration of the material mechanical properties and the decrease of bond between FRP reinforcement and concrete are key aspects of the structural behavior of concrete members reinforced with FRP bars. Nevertheless the anchoring length at the end of the members not directly exposed to fire could ensure a fire resistance time higher than 180 minutes