Partial safety factors for prestressed concrete girders strengthened with CFRP laminates

This paper provides a framework for the calibration of partial safety factors in prestressed concrete (PC) girders strengthened in flexure with carbon fibre-reinforced polymer (CFRP) laminates. A hybrid approach was proposed to take advantage of comprehensive non-linear numerical models in reliability analysis using a first order reliability method (FORM) in conjunction to the response surface method (RSM). The PC girders selected for analyses were taken from real structures designed and built since the 1980s, based on old standards, now requiring strengthening and upgrade due to partial corrosion of prestressing strands. Using the proposed approach, a sensitivity analysis was performed to identify the most relevant variables and assess the area of CFRP laminates needed to restore the capacity to new design standards. Following this study, a partial safety factor was proposed for strengthening PC girders using CFRP laminates. A sensitivity analysis also showed the traffic loads and model uncertainties to be the most important variables for calibration

Partial safety factors for prestressed concrete girders 2 strengthened with CFRP laminates

This paper provides a framework for the calibration of partial safety factors in prestressed concrete (PC) girders strengthened in flexure with carbon fiber-reinforced polymer (CFRP) laminates. A hybrid approach was proposed to take advantage of comprehensive nonlinear numerical models in reliability analysis using a first-order reliability method (FORM) in conjunction with the response surface method (RSM). The PC girders selected for analyses were taken from real structures designed and built in the 1980s based on old standards that now require strengthening and upgrade due to partial corrosion of the prestressing strands. Using the proposed approach, a sensitivity analysis was performed to identify the most relevant variables and assess the area of CFRP laminates needed to restore capacity up to new design standards. A partial safety factor was proposed for strengthening PC girders using CFRP laminates. Sensitivity analysis showed that traffic loads and model uncertainties are the most important variables for calibration. (C) 2019 American Society of Civil Engineers.Portuguese Science and Technology Foundation (FCT)Portuguese Foundation for Science and Technology [SFRH/BD/76345/2011]Australian Research CouncilAustralian Research Council [DE150101703, LP140100591]FCT, within Institute for Sustainability and Innovation in Structural Engineering (ISISE) [UID/ECI/04029/2013]info:eu-repo/semantics/publishedVersio

Effects of bondline thickness in externally bonded joints processed with vacuum assisted resin infusion

The interfacial behaviour between concrete and fibre reinforced polymer (FRP) materials has been investigated for two commonly used processing techniques, wet lay-up sheets and pultruded laminates. However, the experimental database on the bond between concrete and FRP plates processed with Vacuum Assisted Resin Infusion (VARI) technique is limited. In this paper, the bond characteristics between the VARI processed FRP plates and concrete substrate is studied. Tests provide investigative analysis of the interface behaviour of the adhesively bonded joints processed with the VARI technique. Experiments carried out using a new modified single lap shear test set-up enables the slip between FRP plate and substrate to be monitored during the test with higher precision. During the testing, the effect of the FRP thickness on the interface behaviour was considered by variation of the bondline from 2 mm to 6 m

Effect of Biodegradable Binder Properties and Operating Conditions on Growth of Urea Particles in a Fluidized Bed Granulator

Granulation is an important step during the production of urea granules. Most of the commercial binders used for granulation are toxic and non-biodegradable. In this study, a fully biodegradable and cost-effective starch-based binder is used for urea granulation in a fluidized bed granulator. The effect of binder properties such as viscosity, surface tension, contact angle, penetration time, and liquid bridge bonding force on granulation performance is studied. In addition, the effect of fluidized bed process parameters such as fluidizing air inlet velocity, air temperature, weight of primary urea particles, binder spray rate, and binder concentration is also evaluated using response surface methodology. Based on the results, binder with higher concentration demonstrates higher viscosity and higher penetration time that potentially enhance the granulation performance. The viscous Stokes number for binder with higher concentration is lower than critical Stokes number that increases coalescence rate. Higher viscosity and lower restitution coefficient of urea particles result in elastic losses and subsequent successful coalescence. Statistical analysis indicate that air velocity, air temperature, and weight of primary urea particles have major effects on granulation performance. Higher air velocity increases probability of collision, whereby lower temperature prevents binder to be dried up prior to collision. Findings of this study can be useful for process scale-up and industrial applicatio

Bi-parametric optimal partition invariancy sensitivity analysis in linear optimization

Linear optimization, Bi-parametric sensitivity analysis, Optimal partition, Invariancy region, Optimal value function,