Simulation of brittle damage for fracture process of endodontically treated tooth

The mechanics of brittle damage in porcelain of an endodontically treated maxilla incisor tooth was simulated using finite element method (FEM). For this purpose a very complex composite structure of endodontically treated tooth is simulated under transverse loading. Three dimensional (3D) model of human maxilla incisor tooth root was developed based on Computed Tomography (CT) scan images. Crown, core cement, resin core, dental post, post cement and dentin were created using SolidWorks software, and then the model was imported into ABAQUS-6.9EF software for nonlinear behavior analysis. This study utilizes finite element method to simulate onset and propagation of crack in ceramic layer (porcelain) by the cause of both tension and compression loading related to complexity of the geometry of tooth implant. The simulation has been done using brittle damaged model available in ABAQUS/Explicit in quasi-static load condition. The load-displacement response of whole structure is measured from the top of porcelain by controlling displacement on a rigid rod. Crack initiated at the top of porcelain bellow the location of the rod caused by tension damage at equivalent load of 590 N. Damage in porcelain accounts for up to 63% reduction of whole structure stiffness from the undamaged state. The failure process in porcelain layer can be described by an exponential rate of fracture energy dissipation. This study demonstrated that the proposed finite element model and analysis procedure can be use to predict the nonlinear behavior of tooth implant

Structural capacity assessment of corroded RC bridge piers

A new numerical model is developed that enables simulation of the nonlinear flexural response of reinforced concrete (RC) components and sections with corroded reinforcement. The numerical model employs a displacement based beam-column element using the classical Hermitian shape function. The material nonlinearity is accounted for by updating element stiffness matrices using the moment-curvature response of the element section considering uniform stiffness over the element. The cover concrete strength is adjusted to account for corrosion induced cover cracking and the core confined concrete strength and ductility are adjusted to account for corrosion induced damage to the transverse reinforcement. The numerical model is validated against a bench mark experiment on a corroded RC column subject to lateral cyclic loading. The verified model is then used to explore the impact of corrosion on the inelastic response and the residual capacity of corroded RC sections. The results show that considering the effect of corrosion damage on RC sections changes the failure mode of RC columns

Effect of Copper And/Or Bacitracin On The Sulphur Amino Acid Requirements Of Turkeys

A nonsignificant but consistent depressing effects from additions of combined copper (120 ppm) and zinc bacitracin (50 or 75 g per ton) was observed in a previous study. One of the factors that has been suspected to be affected by copper is utilization of sulfur containing amino acids. Thus, a factorial experiment was conducted to study the effect of copper (120 ppm) and/or zinc bacitracin (25 g per ton) on the level of sulfur amino acids at 85%, 100% and 115% of NRC (1977) requirements. The low protein density series of Guenthner et al. (1978) was used (23, 20, 18, 16, 14 and 12%). Dietary protein level was reduced at 4-week intervals

Computational Modelling Strategies for Nonlinear Response Prediction of Corroded Circular RC Bridge Piers

A numerical model is presented that enables simulation of the nonlinear flexural response of corroded reinforced concrete (RC) components. The model employs a force-based nonlinear fibre beam-column element. A new phenomenological uniaxial material model for corroded reinforcing steel is used. This model accounts for the impact of corrosion on buckling strength, post-buckling behaviour and low-cycle fatigue degradation of vertical reinforcement under cyclic loading. The basic material model is validated through comparison of simulated and observed response for uncorroded RC columns. The model is used to explore the impact of corrosion on the inelastic response of corroded RC columns

Nonlinear fiber element modeling of RC bridge piers considering inelastic buckling of reinforcement

An advanced modelling technique is developed to model the nonlinear cyclic response of circular RC columns using fibre-based section discretisation method. A comparison between different reinforcing steel models is made. Through a comprehensive parametric study the influence of inelastic buckling of vertical reinforcement on the cyclic response of circular RC columns is investigated. The results have been compared and validated against a set of experimental datasets. The proposed calibrated model accounts for the influence of inelastic buckling of vertical reinforcement and interaction of stiffness of horizontal ties reinforcement with vertical reinforcement. The model also accounts for the fracture of vertical bars due to low-cycle high-amplitude fatigue degradation. Therefore, this model is able to predict the nonlinear cyclic response of circular RC columns up to complete collapse. The results show that the existing uniaxial material models of reinforcing bars that are calibrated using stress-strain behaviour of isolated bars cannot represent the behaviour of reinforcing bars inside RC columns. Moreover, it is found that the buckling length of vertical reinforcement has a significant influence on the pinching response of RC columns and also reduces the low-cycle fatigue life of buckled reinforcemen