In-Place FE Modeling of Unbonded Flexible Pipelines Capturing Pressure Stiffening and Decoupled Axial/Nonlinear Bending Stiffness

2010 ◽  
Author(s):  
Edvin Hanken ◽  
Evelyn R. Hollingsworth ◽  
Lars S. Fagerland
Keyword(s):  
Water Injection ◽  
Bending Stiffness ◽  
Axial Stiffness ◽  
Fe Model ◽  
Nonlinear Bending ◽  
Upheaval Buckling ◽  
History Effects ◽  
System Integrity ◽  
Non Linear ◽  
Bending Behaviour

For fast track pipeline projects the need for costly installation vessels and sophisticated materials for rigid pipeline water injection systems, have made flexible pipelines a competitive alternative. They can be installed with less costly construction vessels, provide a competitive lead time and a corrosion resistant compliant material. Flexible pipelines have relative high axial stiffness and low non-linear bending stiffness which is a challenge to model correctly with FE for in-place analyses of pipelines. Whilst some FE programs can model the non-linear bending behaviour of a flexible pipeline at a given pressure, current FE tools do not include the effect of increased bending resistance as the system is pressurized. Therefore, a 3D FE model in ANSYS was developed to simulate the decoupled axial and nonlinear bending behaviour of a flexible, including the bend stiffening effect for increasing pressure. A description of the model is given in this paper. It will be demonstrated how the FE model can be used to simulate the 3D nonlinear catenary behaviour of an high pressure flexible pipeline tied into a manifold during pressurization. Due to high manifold hub loads during pressurization it is essential that such a model is capable of capturing all effects during pressurization to achieve an acceptable confidence level of the system integrity. It is also described how the FE model is used for upheaval buckling design, capturing non-linearities and load history effects that can reduce the conservatism in the design.

Study on bearing stiffness characteristics with residual stress in carburized layer

2020 ◽  
pp. 095440622096079
Author(s):  
Junshuai Liang ◽  
Ning Li ◽  
Jingyu Zhai ◽  
BaoGang Wen ◽  
Qingkai Han ◽  
...  
Keyword(s):  
Residual Stress ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
High Load ◽  
Axial Stiffness ◽  
Fe Model ◽  
Low Load ◽  
Bearing Stiffness ◽  
Carburized Layer ◽  
Stiffness Characteristics

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.

scholarly journals Low Cost Frictional Seismic Base-Isolation of Residential New Masonry Buildings in Developing Countries: A Small Masonry House Case Study

2017 ◽  
Vol 11 (1) ◽  
pp. 1026-1035 ◽  
Author(s):  
Ahmad Basshofi Habieb ◽  
Gabriele Milani ◽  
Tavio Tavio ◽  
Federico Milani
Keyword(s):  
Finite Element ◽  
Seismic Vulnerability ◽  
Base Isolation ◽  
Low Cost ◽  
Element Model ◽  
Shaking Table ◽  
Fe Model ◽  
Isolation System ◽  
Finite Element Software ◽  
Non Linear

Introduction:An advanced Finite Element model is presented to examine the performance of a low-cost friction based-isolation system in reducing the seismic vulnerability of low-class rural housings. This study, which is mainly numerical, adopts as benchmark an experimental investigation on a single story masonry system eventually isolated at the base and tested on a shaking table in India.Methods:Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ for the friction coefficient, which was experimentally obtained through the aforementioned research. The FE model adopted here is based on a macroscopic approach for masonry, which is assumed as an isotropic material exhibiting damage and softening. The Concrete damage plasticity (CDP) model, that is available in standard package of ABAQUS finite element software, is used to determine the non-linear behavior of the house under non-linear dynamic excitation.Results and Conclusion:The results of FE analyses show that the utilization of friction isolation systems could much decrease the acceleration response at roof level, with a very good agreement with the experimental data. It is also found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is that there was little damage appearing in systems with frictional isolation during numerical simulations. Meanwhile, a severe state of damage was clearly visible for the system without isolation.

Robustness evaluation of CSMM based finite element for simulation of shear critical hollow RC bridge piers

2019 ◽  
Vol 37 (1) ◽  
pp. 313-344
Author(s):  
Vijay Kumar Polimeru ◽  
Arghadeep Laskar
Keyword(s):  
Finite Element ◽  
Earthquake Engineering ◽  
Bridge Piers ◽  
Fe Model ◽  
Content Type ◽  
Aspect Ratios ◽  
Linear Behavior ◽  
Non Linear ◽  
Reversed Cyclic ◽  
Rc Bridge Piers

Purpose The purpose of this study is to evaluate the effectiveness of two-dimensional (2D) cyclic softened membrane model (CSMM)-based non-linear finite element (NLFE) model in predicting the complete non-linear response of shear critical bridge piers (with walls having aspect ratios greater than 2.5) under combined axial and reversed cyclic uniaxial bending loads. The effectiveness of the 2D CSMM-based NLFE model has been compared with the widely used one-dimensional (1D) fiber-based NLFE models. Design/methodology/approach Three reinforced concrete (RC) hollow rectangular bridge piers tested under reversed cyclic uniaxial bending and sustained axial loads at the National Centre for Research on Earthquake Engineering (NCREE) Taiwan have been simulated using both 1D and 2D models in the present study. The non-linear behavior of the bridge piers has been studied through various parameters such as hysteretic loops, energy dissipation, residual drift, yield load and corresponding drift, peak load and corresponding drift, ultimate loads, ductility, specimen stiffness and critical strains in concrete and steel. The results obtained from CSMM-based NLFE model have been critically compared with the test results and results obtained from the 1D fiber-based NLFE models. Findings It has been observed from the analysis results that both 1D and 2D simulation models performed well in predicting the response of flexure critical bridge pier. However, in the case of shear critical bridge piers, predictions from 2D CSMM-based NLFE simulation model are more accurate. It has, thus, been concluded that CSMM-based NLFE model is more accurate and robust to simulate the complete non-linear behavior of shear critical RC hollow rectangular bridge piers. Originality/value In this study, a novel attempt has been made to provide a rational and robust FE model for analyzing shear critical hollow RC bridge piers (with walls having aspect ratios greater than 2.5).

Towards imperfection insensitive buckling response of shell structures-shells with plate-like post-buckled responses

2016 ◽  
Vol 120 (1224) ◽  
pp. 233-253 ◽  
Author(s):  
S. C. White ◽  
P. M. Weaver
Keyword(s):  
Variable Stiffness ◽  
Axial Stiffness ◽  
Asymptotic Model ◽  
Imperfection Sensitivity ◽  
Asymptotic Results ◽  
Buckling Mode ◽  
Design Variables ◽  
Non Linear ◽  
Buckling Stability ◽  
Post Buckling

ABSTRACTThe imperfection sensitivity of cylindrical panels under compression loading is shown to be not only reduced but effectively eliminated using stiffness tailoring techniques. Shells are designed with variable angle-tow (VAT) laminae, giving their laminates variable-stiffness properties over the surface co-ordinates. By employing an asymptotic model of the non-linear shell behaviour and a genetic algorithm, the post-buckling stability was maximised with respect to the VAT design variables. Results for optimised straight-fibre and VAT shells are presented in comparison with quasi-isotropic designs. In the straight-fibre case, small improvements in the post-buckling stability are shown to be possible but at the expense of the buckling load. In the VAT case, on the other hand, considerable improvements in the post-buckling stability are obtained and drops in axial stiffness and load associated with buckling are reduced to negligible levels. The improvements are shown to be a result of a benign membrane stress distribution prior to buckling and a localisation of the buckling mode. The asymptotic results are compared with non-linear finite-element analyses and are found to be in good agreement. Potential future multi-objective optimisation studies are discussed.

ON DETECTION OF DEFECTS IN BEAMS AND TRUSSES FROM DYNAMIC RESPONSES

2000 ◽  
Vol 24 (1A) ◽  
pp. 1-31
Author(s):  
S. Lukasiewicz ◽  
K. Palka
Keyword(s):  
Bending Stiffness ◽  
Least Square ◽  
Dynamic Responses ◽  
Axial Stiffness ◽  
Mathematical Form ◽  
The Finite Element Method ◽  
Identification Procedure ◽  
Identification Method ◽  
Model Equations ◽  
Source Of Information

This paper presents an identification method to detect cracks and corroded members in vibrating structures. The mathematical identification procedure based on the least square technique uses the measured dynamic response of a structure as the source of information. The application of the Finite Element Method (FEM) for the representation of all constraints and model equations allows presentation of the identification process in a simple and very efficient mathematical form. Propagation of cracks and other failures of the members cause changes in the bending and axial stiffness of the members. One can detect the crack by observing the change in the bending stiffness caused by the closing and opening of the crack in two different configurations. The proposed identification method provides highly precise calculated results which allows detection of small changes in the bending stiffness of the members resulting from cracks and corrosion. The method was tested on simulated experimental data.

Further Advances on Concrete Coating Impact on Pipeline Strength

2017 ◽  
Author(s):  
Alberto Battistini ◽  
Luca Catena ◽  
Adelina Mancini ◽  
Lorenzo Marchionni ◽  
Antonio Parrella ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Damage Evolution ◽  
Bending Stiffness ◽  
The State ◽  
Fe Model ◽  
Deformation Capacity ◽  
Strain Concentration ◽  
Concrete Damage ◽  
Strength And Deformation ◽  
Concrete Coating

Concrete Weight Coating is used in offshore industry to provide for pipeline vertical and lateral stability against waves and currents and to guarantee protection against fishing activities. Reinforced concrete coating of adequate strength, especially in case of thick coatings for stringent in-place stability requirements, entails additional bending stiffness and consequently strain concentration at field joints, thus significantly affecting the state of stress and strain on the pipe steel during laying firstly, and then during operations. Attention of the offshore pipeline industry has been focused in the development of experimental and theoretical activities in a more scientific way, which aimed to satisfy the need of a better knowledge in this field. Both analytical and FEM solutions are available in the free literature and relevant standards to predict the contribution of concrete coating layer on global pipeline strength and deformation capacity and simplified threshold values for the concrete damage are provided, as well. Generally, for installation analysis purpose, a pipeline with equivalent mechanical behavior (bending moment-curvature relationship) and physical (weight) properties is used in installation and operation analyses. No assumptions are typically made on concrete damage evolution to evaluate the decay of pipe capacity beyond the elastic range. In this paper new advances in modelling the mechanical behavior of concrete coated joints are discussed. In particular an advanced ABAQUS finite element model is proposed to take into account the effect of concrete coating damage on the overall capacity. The following effects have been accounted: • Non-linear stress-strain relationship of the steel at large usage factors/curvatures on the strain concentration at the field joint. • Concrete coating damage evolution on global pipeline bending stiffness. In this paper: • The state-of-the-art about published materials, numerical studies and design approaches on concrete material modelling and concrete coated pipes is briefly presented; • A FEM based analysis methodology is drawn and proposed for the strength and deformation capacity assessment of a concrete coated pipe; • The FEM model is calibrated on available full scale tests; • The results of a project case study performed with ABAQUS FE Model are given.

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