scholarly journals A multi-mechanical nonlinear fibre beam-column model for corroded columns

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Mehdi Kashani ◽  
Laura N Lowes ◽  
Adam J Crewe ◽  
Nicholas A Alexander
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Design Methodology ◽  
Low Cycle Fatigue ◽  
Nonlinear Behaviour ◽  
Cycle Fatigue ◽  
Rc Columns ◽  
Vertical Bars ◽  
Cyclic Degradation ◽  
The Impact

Purpose A new modelling technique is developed to model the nonlinear behaviour of corrosion damaged reinforced concrete (RC) bridge piers subject to cyclic loading. The model employs a nonlinear beam-column element with multi-mechanical fibre sections using OpenSees. The nonlinear uniaxial material models used in the fibre sections account for the effect of corrosion damage on vertical reinforcing, cracked cover concrete due to corrosion of vertical bars and damaged confined concrete due to corrosion of horizontal tie reinforcement. An advance material model is used to simulate the nonlinear behaviour of the vertical reinforcing bars that accounts for combined impact of inelastic buckling and low-cycle fatigue degradation. The basic uncorroded model is verified by comparison of the computation and observed response of RC columns with uncorroded reinforcement. This model is used in an exploration study of recently tested reinforced concrete components to investigate the impact of different corrosion models on the inelastic response of corrosion damaged RC columns. Design/methodology/approach A series of pushover and cyclic analyses on a hypothetical corroded RC columns are conducted. The impact of corrosion on reinforcing steel and concrete is modelled. The influence of cyclic degradation due to low-cycle fatigue is also modelled. Findings (1) Corrosion has a more significant impact on ductility loss of RC columns than the strength loss (plastic moment capacity). (2) It was found that the flexural failure is initiated by buckling of vertical bars and crushing of core concrete which then followed by fracture of bars in tension. (3) The analyses results showed that for seismic performance and evaluation of existing corroded bridges monotonic pushover analysis is insufficient. The cyclic degradation due to low-cycle fatigue has a significant influence on the response of corroded RC columns. Originality/value The finite element developed in this paper is the most comprehensive model to date that is able to capture the onlinear behaviour of corroded RC columns under cyclic loading up to complete collapse.

Fatigue Behaviour of the Novel Titanium Alloys TIMETAL® 407 and TIMETAL® 412

2021 ◽  
Author(s):  
◽  
William Davey
Keyword(s):  
Crack Initiation ◽  
Titanium Alloys ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Charpy Impact ◽  
Fatigue Behaviour ◽  
High Energy ◽  
Process Window ◽  
Cycle Fatigue ◽  
The Impact

TIMETAL®407 (Ti-407) is a medium strength (~650MPa 0.2%YS) titanium alloy, recently developed by TIMET, in conjunction with Rolls-Royce plc for use in applications requiring high energy absorption at impact. Preliminary Charpy Impact (V notch) testing showed Ti-407 to absorb nearly twice the impact energy of Ti-6-4 and exhibit more than 2.5 times the lateral expansion. Further initial testing suggested the high cycle fatigue (HCF) run out stress of Ti-407 matches that of Ti-6-4 and other high strength alpha-beta titanium alloys. Ti-407 displayed more than double the tool life than that of Ti-6-4. The reduction in tool wear supports lower forces required for faster, more efficient machining. Compared to Ti-6-4, the relatively low elevated temperature flow stress, greater malleability and wide process window should allow Ti-407 to be processed with fewer reheats, while exhibiting reduced surface cracking and giving a consistently good surface finish. Optimised Ti-407 manufacturing processes should allow parts to be formed closer to net shape giving higher yields and requiring less machining to the components finished size. This project has evaluated HCF, as well as low cycle fatigue (LCF) and dwell fatigue crack initiation mechanisms in Ti-407, to clarify the effects of alloy chemistry, microstructural morphology and scale, and crystallographic texture. A derivative of Ti-407, Ti-412 (~750MPa 0.2%YS) was also tested towards the end of the project and helped to further elucidate understanding of the fatigue characteristics of the two alloys. Of interest was the strong HCF response displayed relative to the monotonic tensile strength. As well as the investigation into the crack initiation mechanisms, an assessment of crack propagation across a range of microstructural conditions was carried out on Ti-407 material.

Cyclic Deformation and Buckling Behavior of Pipe With Local Metal Loss Subjected to Seismic Ground Motion

2011 ◽  
Author(s):  
Masaki Mitsuya ◽  
Hiroshi Yatabe
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Earthquake Resistance ◽  
Metal Loss ◽  
Cycle Fatigue ◽  
Longitudinal Length

Buried pipelines may be deformed due to earthquakes and also corrode despite corrosion control measures such as protective coatings and cathodic protection. In such cases, it is necessary to ensure the integrity of the corroded pipelines against earthquakes. This study developed a method to evaluate the earthquake resistance of corroded pipelines subjected to seismic ground motions. Axial cyclic loading experiments were carried out on line pipes subjected to seismic motion to clarify the cyclic deformation behavior until buckling occurs. The test pipes were machined so that each one would have a different degree of local metal loss. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. The pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines, with varying degrees of local metal loss, a finite-element analysis method was developed that simulates the cyclic deformation behavior. A combination of kinematic and isotropic hardening components was used to model the material properties. These components were obtained from small specimen tests that consisted of a monotonic tensile test and a low cycle fatigue test under a specific strain amplitude. This method enabled the successful prediction of the cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss. In addition, the effect of each dimension (depth, longitudinal length and circumferential width) of local metal loss on the cyclic buckling was studied. Furthermore, the kinematic hardening component was investigated for the different materials by the low cycle fatigue tests. The kinematic hardening components could be regarded as the same for all the materials when using this component as the material property for the finite-element analyses simulating the cyclic deformation behavior. This indicates that the cyclic deformation behavior of various line pipes can be evaluated only based on their respective tensile properties and common kinematic hardening component.

Pipe Elbows Under Strong Cyclic Loading

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Cyclic Loading ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Fatigue Curve ◽  
Design Codes ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Fatigue Design ◽  
Process Piping

Motivated by the response of industrial piping under seismic loading conditions, the present study examines the behavior of steel process piping elbows, subjected to strong cyclic loading conditions. A set of experiments is conducted on elbow specimens subjected to constant amplitude in-plane cyclic bending, resulting into failure in the low-cycle-fatigue range. The experimental results are used to develop a low-cycle-fatigue curve within the strain-based fatigue design framework. The experimental work is supported by finite element analyses, which account for geometrical and material nonlinearities. Using advanced plasticity models to describe the behavior of elbow material, the analysis focuses on localized deformations at the critical positions where cracking occurs. Finally, the relevant provisions of design codes (ASME B31.3 and EN 13480) for elbow design are discussed and assessed, with respect to the experimental and numerical findings.

scholarly journals Flexural performance of RC columns with FRCC jacketing

2019 ◽  
Vol 97 ◽  
pp. 03037 ◽  
Author(s):  
Marta Del Zoppo ◽  
Costantino Menna ◽  
Marco Di Ludovico ◽  
Alberto Balsamo
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Strain Distribution ◽  
Deformation Capacity ◽  
Rc Buildings ◽  
Flexural Capacity ◽  
Rc Columns ◽  
Flexural Performance ◽  
Repair Technique ◽  
Control Column

A new repair technique consisting on a light jacketing with Fibre Reinforced Cementitious Composites (FRCC) for existing reinforced concrete (RC) buildings has been recently proposed to reduce durability problems of RC members and enhance their capacity. In this work, the effects of FRCC jacketing on the flexural capacity of existing RC columns, with and without a pre-damage, has been evaluated of full-scale specimens under cyclic loading. Digital Imagine Correlation (DIC) was also adopted for understanding the strain distribution in the FRCC jacket. The results shown that the FRCC jacket without a proper anchorage slightly enhanced the flexural capacity of the column. The strengthened column experienced a low damage with respect to control column, but occurrence of premature failures did not allow the achievement of high levels of deformation capacity and ductility.

scholarly journals Low Cycle Fatigue Life Evaluation of Notched Specimens Considering Strain Gradient

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1001
Author(s):  
Shenghuan Qin ◽  
Zaiyin Xiong ◽  
Yingsong Ma ◽  
Keshi Zhang
Keyword(s):  
Cyclic Loading ◽  
Constitutive Model ◽  
Strain Gradient ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Plastic Behavior ◽  
Cycle Fatigue ◽  
New Model ◽  
Hysteresis Behavior ◽  
Notched Specimens

An improved model based on the Chaboche constitutive model is proposed for cyclic plastic behavior of metal and low cycle fatigue of notched specimens under cyclic loading, considering the effect of strain gradient on nonlinear kinematic hardening and hysteresis behavior. The new model is imported into the user material subroutine (UMAT) of the finite element computing software ABAQUS, and the strain gradient parameters required for model calculation are obtained by calling the user element subroutine (UEL). The effectiveness of the new model is tested by the torsion test of thin copper wire. Furthermore, the calibration method of strain gradient influence parameters of constitutive model is discussed by taking the notch specimen of Q235 steel as an example. The hysteresis behavior, strain distribution and fatigue failure of notched specimens under cyclic loading were simulated and analyzed with the new model. The results prove the rationality of the new model.

scholarly journals Low Cycle Fatigue Failure of a Sitka Spruce Tree in Hurricane Winds

2014 ◽  
Vol 40 (5) ◽  
Author(s):  
Warren Leigh
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Wind Speed ◽  
Fatigue Failure ◽  
Low Cycle Fatigue ◽  
Failure Prediction ◽  
Picea Sitchensis ◽  
Cycle Fatigue ◽  
Hurricane Wind ◽  
The Impact

Pine plantations are prone to stem breakage due to high cyclic stress levels associated with hurricane force winds. Stress analytical and finite element simulation models were constructed of a representative profile of a (Sitka) Picea sitchensis tree. The profile surface stress (S) was determined due to the combined load of tree self-weight and hurricane wind speed. The results were complemented by reference to two other studies by other researchers that investigated the impact of fatigue cycles on failure (N) of pine wood and tree sway cycles to present a stem fatigue life prediction. The position of maximum surface profile stress and trunk fracture initiation location was ascertained from a non-uniform stress response. No stress uniformity along the trunk profile was observed for any wind-load case examined. The analytical model and finite element analysis of the P. sitchensis tree trunk profile revealed a statically adequate strength reserve factor of 1.4, which suggested another mode of failure was responsible. Fatigue life failure prediction was examined under cyclic and same-stress amplitude related to the hurricane wind speed of 33 m s-1. Predicted trunk fracture occurred in 2.6 hours, which dramatically reduced to two minutes with an increase in wind speed of only 1 m s-1. The calculated exposure time was similar to that recorded during Hurricane Hugo’s transit in 1989. The time-to-failure prediction obtained by the method of analysis provided in this study seemed plausible, and that the profile associated with the P. sitchensis tree would suffer trunk breakage by low cycle fatigue failure.

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