Comparative Durability Analysis of CFRP Strengthened RC Highway Bridges

The paper presents parametric analysis of durability factors of RC highway bridges strengthened with CFRP laminates during their service life. Durability factors considered are concrete cover and CFRP laminate thickness. Three deterioration factors were considered. First, growth of live load with time. Second, resistance reduction due to chloride-attack corrosion which causes reduction in steel properties. Corrosion losses are evaluated through a time–temperature dependent corrosion current. Two types of corrosion are considered; uniform and pitting corrosion. Third, deterioration due to aging of CFRP. The reliability analysis is controlled by three failure modes; concrete crushing, CFRP mid span debonding and CFRP rupture. Monte-Carlo simulation is used to develop time dependent statistical models for rebar steel area and live load extreme effect. Reliability is estimated in term of reliability index using FORM algorithm. For illustrative purpose, a RC bridge is assumed as an example. The reliability of interior beam of the bridge is evaluated under various traffic volumes and different corrosion environments. The bridge design options follow AASHTO-LRFD specifications. The present work also extends to calibrate CFRP resistance safety factor corresponds to three target reliability levels, β = 3.5, 3.85, and 4.2. The results of the analysis have shown that corrosion has the most significant effect on bridge life time followed by live load growth. Pitting corrosion type is more hazardous than uniform. Also, initial safety index is proved to be traffic dependent. AASHTO design equation (that corresponds βtarget = 3.5) seems to be overestimated for strengthening purpose. Strengthening with (βtarget = 4.2) provide better reliability than βtarget proposed by AASHTO provision with no significant differences in CFRP amounts required

Seismic retrofitting of reinforced concrete structures using composites

International audienc

Time-variant flexural reliability of RC beams with externally bonded CFRP under combined fatigue-corrosion actions

Time-variant reliability analysis of RC highway bridges strengthened with carbon fibre reinforced polymer CFRP laminates under four possible competing damage modes (concrete crushing, steel rupture after yielding, CFRP rupture and FRP plate debonding) and three degradation factors is analyzed in terms of reliability index β using FORM. The first degradation factor is chloride-attack corrosion which induces reduction in steel area and concrete cover cracking at characteristic key times (corrosion initiation, severe surface cover cracking). The second degradation factor considered is fatigue which leads to damage in concrete and steel rebar. Interaction between corrosion and fatigue crack growth in steel reinforcing bars is implemented. The third degradation phenomenon is the CFRP properties deterioration due to aging. Considering these three degradation factors, the time-dependent flexural reliability profile of a typical simple 15 m-span intermediate girder of a RC highway bridge is constructed under various traffic volumes and under different corrosion environments. The bridge design options follow AASHTO-LRFD specifications. Results of the study have shown that the reliability is very sensitive to factors governing the corrosion. Concrete damage due to fatigue slightly affects reliability profile of non-strengthened section, while service life after strengthening is strongly related to fatigue damage in concrete

Detection of Faults and Drifts in the Energy Performance of a Building Using Bayesian Networks

Despite improved commissioning practices, malfunctions or degradation of building systems still contribute to increase up to 20% the energy consumption. During operation and maintenance stage, project and building technical managers need appropriate methods for the detection and diagnosis of faults and drifts of energy performances in order to establish effective preventive maintenance strategies. This paper proposes a hybrid and multilevel fault detections and diagnosis (FDD) tool dedicated to the identification and prioritization of corrective maintenance actions helping to ensure the energy performance of buildings. For this purpose, we use dynamic Bayesian networks (DBN) to monitor the energy consumption and detect malfunctions of building equipment and systems by considering both measured occupancy and the weather conditions (number of persons on site, temperature, relative humidity (RH), etc.). The hybrid FDD approach developed makes possible the use of both measured and simulated data. The training of the Bayesian network for functional operating mode relies on on-site measurements. As far as dysfunctional operating modes are concerned, they rely mainly on knowledge extracted from dynamic thermal analysis simulating various operational faults and drifts. The methodology is applied to a real building and demonstrates the way in which the prioritization of most probable causes can be set for a fault affecting energy performance. The results have been obtained for a variety of simulated situations with faults deliberately injected, such as increase in heating preset temperature and deterioration of the transmission coefficient of the building\u27s glazing. The limitations of the methodology are discussed and are translated in terms of the ability to optimize the experiment design, control period, or threshold adjustment on the control charts used

Reliability and availability estimation of a photovoltaic system using Petri networks

Many photovoltaic (PV) systems are nowadays installed all around the world. However, the reliability and the availability estimation of photovoltaic systems have not been received great attention from researchers. Reliability and availability are important consideration in the life-cycle of such systems. This paper presents a methodology for estimating the reliability and the availability of a photovoltaic system using Petri networks. Each component - module, wires and inverter - is detailed in Petri networks and several laws are used in order to determine the reliability and system availability. The degradation function of each componenthas been taken into account. Results show that Petri networks simplify the reliability and availability modeling and analysis

Reliability under Seismic Loads of RC Structures Strengthened with FRP using Polynomial Dimensional Decomposition approximation

The present study aims to estimate effectiveness of applying FRP strengthening in order to enhance the seismic structural reliability of RC frames. Two FRP strengthening configurations were compared: applying flexural FRP strengthening to members – beams/columns – of the RC frame and applying FRP confinement to columns of the frame. Seismic reliability was expressed in term of fragility estimates which involves performing nonlinear time history analysis recoding the maximum lateral top drift as a dynamic demand. A nonlinear time history analysis was carried out using finite elements method FEM. In order to reduce the computational effort, an efficient meta-modeling using Polynomial Dimensional Decomposition PDD in conjunction with the Monte-Carlo Simulation (MCS) was used. In addition, a sensitivity analysis using Sobol indices and Morris screening method were applied to evaluate importance of each random variables considered in the analysis . The proposed approach was applied to a typical three-story RC frame. Numerical results demonstrate the efficiency and computational advantages of the proposed meta-model using PDD for the seismic reliability assessment of structures. Furthermore, it was found that enhancement in seismic reliability corresponds to flexural type is quite higher than that corresponds to confining type