Information Aggregation Under Ambiguity: Theory and Experimental Evidence

We study information aggregation in a dynamic trading model with partially informed and ambiguity averse traders. We show theoretically that separable securities, introduced by Ostrovsky (2012) in the context of Subjective Expected Utility, no longer aggregate information if some traders have imprecise beliefs and are ambiguity averse. Moreover, these securities are prone to manipulation, as the degree of information aggregation can be influenced by the initial price, set by the uninformed market maker. These observations are also confirmed in our experiment, using prediction markets. We define a new class of strongly separable securities which are robust to the above considerations, and show that they characterize information aggregation in both strategic and non-strategic environments. We derive several theoretical predictions, which we are able to confirm in the lab

Seismic vulnerability of RC structures: Assessment before and after FRP retrofitting (case study)

In structural engineering, seismic assessment of existing structures is a crucial issue to provide adapted decisions in a vulnerability reduction context. Amongst the widely range of technical solutions for structural upgrading, external reinforcement by Fiber Reinforced Polymer (FRP) is an interesting tool. Nevertheless, the use of FRP as a retrofitting method is limited, one of the reasons being the lack of predictive numerical tools allowing the vulnerability assessment. Based on a case-study, this paper presents a simplified modeling strategy to assess the seismic vulnerability of an existing reinforced concrete building before and after FRP retrofitting. More specifically, the structure is simulated using multifiber beam elements, the model is validated with in-situ ambient vibrations records and a simplified method to consider FRP retrofitting is proposed. Non linear dynamic analysis studies are performed using a synthetic earthquake signal according to the Eurocode 8. Finally, local indicators, based on the European Macroseismic Scale (EMS 98), are adopted to quantify the damage level in the structure, before and after its FRP retrofitting.Keywords: earthquake; vulnerability; retrofitting; FRP; concrete; multifiber beam

Damage model for FRP-confined concrete columns under cyclic loading

International audienceIn structural engineering, seismic vulnerability reduction of existing structures is a crucial issue. External reinforcement with fiber-reinforced polymer (FRP) holds interest in achieving this aim. Its use as a retrofitting method is limited, however, for a number of reasons, including the lack of numerical tools for predicting cyclic loading. This paper presents a simplified stress-strain model suitable for monotonic and cycling loading capable of predicting the FRP's effect on reinforced-concrete columns. The model was inspired by two well-known concrete constitutive laws: one based on damage mechanics (La Borderie's concrete-damage model, 1991); the other on extensive experimental studies (Eid and Paultre's confined-concrete model, 2008). Validation is provided using experimental results on reinforced concrete columns subjected to axial and flexural cyclic loading. The proposed approach also deals with steel-bar rupture, considering low-cycle fatigue effects. All the simulations were conducted with multifiber Timoshenko beam elements

Seismic vulnerability reduction: numerical modeling of FRP reinforcement using multifiber beams elements

This paper presents a simplified modeling strategy for reproducing the behavior of beam-column structures reinforced with Polymer Reinforced Fibers (FRP). A 1D concrete constitutive model has been recently proposed, suitable for both monotonic and cycling loadings. The model is inspired on two well-known concrete laws, one based on damage mechanics theory (La Borderie concrete damage model) and one based on experimental studies (Eid & Paultre's confined concrete model). Spatial discretization is done using multifiber Timoshenko beam elements. Validation of the strategy is provided using two case studies: a retrofitted bridge pier and a vulnerability analysis on an existing building

Stress-strain model for FRP-confined concrete columns under cyclic and seismic loading

In structural engineering, seismic vulnerability reduction of existing structures is a crucial issue. External reinforcement with fiber-reinforced polymer (FRP) holds interest in achieving this aim. Its use as a retrofitting method is limited, however, for a number of reasons, including the lack of numerical tools for predicting cyclic loading. This paper presents a simplified stress-strain model suitable for monotonic and cycling loading capable of predicting the FRP's effect on reinforced-concrete col umns. The model is inspired by two well-known concrete constitutive laws: one based on damage mechanics (La Borderie's concrete-damage model, 1991); the other on extensive experimental studies (Eid & Paultre's confined-concrete model, 2008). Validation is provided using experimental results on reinforced concrete columns subjected to axial and flexural cyclic loading. All the simulations were conducted with multifiber Timoshenko beam elements

Analyse et Réduction de la Vulnérabilité Sismique d'une Structure Existante en Béton Armé : Renforcement par TFC

La réduction de la vulnérabilité sismique des structures existantes est un enjeu majeur. Le renforcement d'éléments par Tissus de Fibres de Carbone (TFC) offre une réponse intéressante à cette problématique. Ces travaux proposent une stratégie simplifiée de modélisation non linéaire permettant de prédire le comportement d'une structure en béton armé renforcée par TFC. Celle-ci est fondée sur l'utilisation d'éléments finis poutres multifibres ainsi que de modèles d'endommagement et de plasticité. Le confortement d'éléments en flexion et le confinement des poteaux sont étudiés. Plus spécifiquement une loi constitutive cyclique pour béton confiné est proposée. Cette loi est fondée sur deux modèles, le premier basé sur la théorie de l'endommagement et le second sur une série d'études expérimentales. Cette approche est validée à travers deux cas d'études : une pile de pont renforcée et une analyse de vulnérabilité d'un ouvrage sous sollicitations statiques (poussée progressive) et dynamiques

Retrofitting reinforced concrete structures with FRP: Numerical simulations using multifiber beam elements

In structural engineering, seismic vulnerability reduction of existing structures is a crucial issue. External reinforcement by Polymer Reinforced Fibers (FRP) is an interesting tool in order to fulfill this aim. However, the use of FRP reinforcement as a retrofitting method is limited, one of the reasons being the lack of predicting numerical tools for cyclic loading. This paper presents a method to predict the behavior of beam-column structures considering the FRP reinforcement effect. It describes the construction of a 1D concrete constitutive model suitable for monotonic and cycling loadings. The model is inspired on two well-known concrete models, the first one based on the damage mechanics theory (La Borderie concrete damage model), and the second one based on experimental studies (Eid & Paultre's confined concrete model). Validation of the approach is done using experimental results on reinforced concrete beam and columns submitted to axial and flexural cyclic loading. The proposed method deals also with steel bar rupture considering low cycle fatigue effects. All the simulations are done using multifiber Timoshenko beam elements

Real-time ECG Monitoring using Compressive sensing on a Heterogeneous Multicore Edge-Device

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In a typical ambulatory health monitoring systems, wearable medical sensors are deployed on the human body to continuously collect and transmit physiological signals to a nearby gateway that forward the measured data to the cloud-based healthcare platform. However, this model often fails to respect the strict requirements of healthcare systems. Wearable medical sensors are very limited in terms of battery lifetime, in addition, the system reliance on a cloud makes it vulnerable to connectivity and latency issues. Compressive sensing (CS) theory has been widely deployed in electrocardiogramme ECG monitoring application to optimize the wearable sensors power consumption. The proposed solution in this paper aims to tackle these limitations by empowering a gatewaycentric connected health solution, where the most power consuming tasks are performed locally on a multicore processor. This paper explores the efficiency of real-time CS-based recovery of ECG signals on an IoT-gateway embedded with ARM’s big.littleTM multicore for different signal dimension and allocated computational resources. Experimental results show that the gateway is able to reconstruct ECG signals in real-time. Moreover, it demonstrates that using a high number of cores speeds up the execution time and it further optimizes energy consumption. The paper identifies the best configurations of resource allocation that provides the optimal performance. The paper concludes that multicore processors have the computational capacity and energy efficiency to promote gateway-centric solution rather than cloud-centric platforms

La modellazione dei fenomeni di interazione terreno-struttura mediante macroelementi: elastoplasticità vs. ipoplasticità

International audienceIn this work two different macroelements for shallow foundations, recently developed in the framework of the theories of hardening plasticity and hypoplasticity, have been considered to evaluate the effects of the soil-structure interaction for a reinforced concrete viaduct subject to earthquake loading. To this aim, the predictions of the dynamic behaviour of the viaduct obtained with the two macroelements – in terms of forces and displacements – have been compared with those obtained for the case of rigid soil. Despite the differences existing in the mathematical structure of the constitutive equations of the two macroelements, the analyses have shown very similar results, both in terms of structural loads and in terms of computed displacements and rotations of the foundations. In the ideal case study considered in this work, the soil-structure interaction reduces significantly the structural load and the ductility demand of the piers. The example presented shows that the two macroelements adopted may represent a significant step forward in the implementation of simple, robust and accurate computational tools for the soil-structure interaction analysis, both for research and geotechnical design.Nel presente lavoro due diversi macroelementi per fondazioni superficiali, recentemente sviluppati nell’ambito delle teorie della plasticità incrudente e dell’ipoplasticità, sono impiegati per valutare gli effetti dell’interazione terreno-struttura per un viadotto in c.a. precompresso soggetto ad un evento sismico. A tale fine, le previsioni del comportamento dinamico del viadotto ottenute con i macroelementi – in termini di sollecitazioni e spostamenti – sono state confrontate con quelle ottenute nel caso di terreno di fondazione infinitamente rigido. Nonostante la struttura matematica delle equazioni costitutive implementate nei due macroelementi sia molto diversa, le simulazioni eseguite mostrano risultati molto simili, sia in termini di sollecitazioni negli elementi strutturali, che in termini di spostamenti orizzontali e rotazioni delle fondazioni. Nel caso esaminato, l’interazione terreno-struttura riduce in misura significativa le sollecitazioni nella struttura e la richiesta di duttilità nelle pile. L’esempio analizzato mostra che i due macroelementi presi in esame possono costituire un signi-ficativo passo in avanti nella messa a punto di strumenti di calcolo semplici, robusti ed accurati per l’analisi dei fenomenidi interazione terreno-struttura, non solo per scopi di ricerca ma anche a livello di progettazione ordinaria