scholarly journals Practical Model Proposed for the Structural Analysis of Segmental Tunnels

2020 ◽  
Vol 10 (23) ◽  
pp. 8514
Author(s):  
Jatziri Y. Moreno-Martínez ◽  
Arturo Galván ◽  
Fernando Peña ◽  
Franco Carpio
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Limit State ◽  
Structural Response ◽  
3D Models ◽  
Complex Model ◽  
Numerical Results ◽  
Point Of View ◽  
Simplified Model ◽  
Ultimate Limit State

The construction of tunnels has become increasingly common in city infrastructure; tunnels are used to connect different places in a region (for transportation and/or drainage). In this study, the structural response of a typical segmental tunnel built in soft soil was studied using a simplified model which considers the coupling between segmental rings. From an engineering point of view, there is a need to use simple and reliable finite element models. Therefore, a 1D model based on the Finite Element Method (FEM) composed of beam elements to model the segments and elastic-linear springs and non-linear springs to model the mechanical behavior of the joints was performed. To validate the modeling strategy, the numerical results were compared to (lab-based) experimental results, under an Ultimate Limit State, obtained from the literature, and a comparison between numerical results considering a 3D numerical complex model which included the nonlinearity of concrete, reinforcing steel and the joints was performed. With this simplified model, we obtained a prediction of approximately 95% of the ultimate loading capacity compared to the results developed in the experimental and 3D models. This proposed model will help engineers in practice to create “rational” structural designs of segmental tunnel linings when a “low” interaction between rings is expected.

scholarly journals Assessment of Buckling Behaviour on an FPSO Deck Panel

2020 ◽  
Vol 27 (3) ◽  
pp. 50-58 ◽  
Author(s):  
Ozgur Ozguc
Keyword(s):  
Finite Element ◽  
Limit State ◽  
Practical Interest ◽  
Structural Response ◽  
Ultimate Limit State ◽  
Imperfection Sensitivity ◽  
Stiffened Panels ◽  
Structural Capacity ◽  
Response Subject ◽  
Ultimate Limit

AbstractStiffened plates are the main structural building block in ship and offshore hulls and their structural response subject to loads is a topic of significant practical interest in ship and offshore structural design. To investigate the structural capacity for design and evaluation purposes, it is becoming an efficient and reliable practice to carry out non-linear finite element (FE) analysis. The present study is to assess the buckling strength of a stiffened deck panel on an FPSO vessel using the nonlinear finite element code ADVANCE ABAQUS, where imperfection sensitivity work is also accounted for. The cases studied correspond to in-plane bi-axial compression in the two orthogonal directions. The findings are compared with the DNVGL PULS (Panel Ultimate Limit State) buckling code for the stiffened panels. It is found that the strength values from the ADVANCE ABAQUS and DNVGL PULS code are very close. The results and insights developed from the present work are discussed in detail.

Permafrost Thawing-Pipeline Interaction Advanced Finite Element Model

2009 ◽  
Author(s):  
Jianfeng Xu ◽  
Basel Abdalla ◽  
Ayman Eltaher ◽  
Paul Jukes
Keyword(s):  
Finite Element ◽  
Energy Demand ◽  
Large Scale ◽  
Limit State ◽  
The Arctic ◽  
Ultimate Limit State ◽  
Fe Model ◽  
Field Development ◽  
Thaw Settlement ◽  
Permafrost Thawing

The increasing energy demand has promoted the interest in exploration and field development in the Arctic waters, which holds one quarter of the world’s petroleum reserves. The harsh conditions and fragile environment in the arctic region introduce many challenges to a sustainable development of these resources. One of the key challenges is the engineering consideration of warm pipelines installed in permafrost areas; found mainly in shallow waters and shore crossings. Evaluations have to be made during the pipeline design to avoid significant thaw settlement and large-scale permafrost degrading. In this paper, a three-dimensional (3D) finite element (FE) model was developed to study the interaction between buried pipelines transporting warm hydrocarbons and the surrounding permafrost. This interaction is a combination of several mechanisms: heat transfer from the pipeline, results in permafrost thawing and formation of thaw bulb around the pipeline. Consequently, the thaw settlement of soil beneath the pipeline base results in bending strains in the pipe wall. For safe operations, the pipe should be designed so that the induced strains do not exceed the ultimate limit state conditions. The developed model helps in accurate prediction of pipe strains by using finite element continuum modeling method as opposed to the more commonly used discrete (springs) modeling and hand calculations. It also assesses the real size of the thaw bulb and the corresponding settlement at any time, thus preventing an over-conservative design.

Risk Analysis for the Construction Phases of Long-Span CFST Arch Bridge Based on Finite Element Analysis

2011 ◽  
Vol 225-226 ◽  
pp. 823-826
Author(s):  
Yu Feng Zhang ◽  
Guo Fu Sun
Keyword(s):  
Finite Element ◽  
Risk Analysis ◽  
Limit State ◽  
Ultimate Limit State ◽  
Element Analysis ◽  
Nonlinear Buckling ◽  
Finite Element Program ◽  
Arch Bridge ◽  
Cfst Arch Bridge ◽  
Element Program

As a part of virtual simulation of construction processes, this paper deals with the quantitative risk analysis for the construction phases of the CFST arch bridge. The main objectives of the study are to evaluate the risks by considering an ultimate limit state for the fracture of cable wires and to evaluate the risks for a limit state for the erection control during construction stages. Many researches have been evaluated the safety of constructed bridges, the uncertainties of construction phases have been ignored. This paper adopts the 3D finite element program ANSYS to establish the space model of CFST Arch Bridge, and to calculate the linear, the geometrical nonlinear and the double nonlinear buckling safety factors under the six different lode cases. Then the bridge’s risks are evaluated according to the results calculated which provide a reference for design of similar project.

Three-dimensional finite element modelling of a full-scale geosynthetic-reinforced, pile-supported embankment

2015 ◽  
Vol 52 (12) ◽  
pp. 2041-2054 ◽  
Author(s):  
R. Kerry Rowe ◽  
K.-W. Liu
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Three Dimensional ◽  
Single Layer ◽  
Full Scale ◽  
Numerical Results ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Pile Supported Embankment

The performance of four sections of a full-scale embankment constructed on soft soil is examined using a fully coupled and fully three-dimensional finite element analysis. The four sections had similar embankment loadings but different improvement options (one unimproved, one with pile-support only, one with a single layer geotextile-reinforced platform and pile-support, and one with two layers of geogrid-reinforced platform and pile-support). Like the field data, the numerical results show that the inclusion of piles decreases the settlement at the subsoil surface to 52% of that for the unimproved section, and the addition of a single layer of geotextile reinforcement (J = 800 kN/m) further reduced settlement to only 31% of that of the unimproved section. The effects of geosynthetic reinforcement and multiple layers of reinforcement on the performance of the pile-supported embankment are discussed. The relative load transfer is calculated using eight existing methods and they are compared with the field measurements and numerical results.

scholarly journals Structural Phenomenon of Cement-Based Composite Elements in Ultimate Limit State

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
I. Iskhakov ◽  
Y. Ribakov
Keyword(s):  
Limit State ◽  
Structural Response ◽  
Minimax Principle ◽  
Ultimate Limit State ◽  
Spatial Structures ◽  
Design Concepts ◽  
Dynamic Loadings ◽  
Ultimate Limit ◽  
Additional Equation ◽  
Theoretical Results

Cement-based composite materials have minimum of two components, one of which has higher strength compared to the other. Such materials include concrete, reinforced concrete (RC), and ferrocement, applied in single- or two-layer RC elements. This paper discusses experimental and theoretical results, obtained by the authors in the recent three decades. The authors have payed attention to a structural phenomenon that many design features (parameters, properties, etc.) at ultimate limit state (ULS) of a structure are twice higher (or lower) than at initial loading state. This phenomenon is evident at material properties, structures (or their elements), and static and/or dynamic structural response. The phenomenon is based on two ideas that were developed by first author: quasi-isotropic state of a structure at ULS and minimax principle. This phenomenon is supported by experimental and theoretical results, obtained for various structures, like beams, frames, spatial structures, and structural joints under static or/and dynamic loadings. This study provides valuable indicators for experiments’ planning and estimation of structural state. The phenomenon provides additional equation(s) for calculating parameters that are usually obtained experimentally and can lead to developing design concepts and RC theory, in which the number of empirical design coefficients will be minimal.

Redistribution of longitudinal moments in straight, continuous concrete slab – steel girder composite bridges

2006 ◽  
Vol 33 (4) ◽  
pp. 471-488 ◽  
Author(s):  
A Ghani Razaqpur ◽  
Afshin Esfandiari
Keyword(s):  
Finite Element ◽  
Concrete Slab ◽  
Limit State ◽  
Slab Thickness ◽  
Ultimate Limit State ◽  
Bridge Design ◽  
Moment Redistribution ◽  
Composite Bridges ◽  
Composite Bridge ◽  
Aashto Lrfd

The effect of loading and geometric parameters on the transverse and longitudinal redistribution of moments in continuous composite bridges, comprising a concrete slab on parallel steel girders, is investigated with the nonlinear finite element method. Fifty bridges are analyzed over their entire range of loading up to failure, and their moment redistribution factors are determined and compared with the relevant predictions of the Canadian Highway Bridge Design Code (CHBDC) and the AASHTO LRFD Bridge Design Specifications. The parameters studied included truck position along the bridge, number of loaded lanes, bridge width, number of girders, slab thickness, degree of composite action, and presence of diaphragms. The study reveals that among the preceding parameters only the number of loaded lanes and the bridge width significantly affect transverse redistribution of moments at ultimate limit state (ULS). However, most of the preceding parameters affect longitudinal redistribution at ULS. Finally, it is demonstrated that plastic analysis of composite multi-girder continuous bridges, treated as an equivalent beam, provides a reasonable estimate of their longitudinal moment redistribution capacity at ULS. It is demonstrated that the actual load-carrying capacity of a composite bridge may be more than 50% higher than that predicted by the CHBDC or AASHTO code. Such higher predicted capacity may obviate the need for retrofit in some cases.Key words: analysis, bridge, composite, concrete, distribution, finite element, inelastic, load, steel.

scholarly journals Structural analisys of concrete pre-stressed reservoirs for sludge fermentation – water waste treatment plant bucharest – glina. numerical fem assessment of the structural response for static in-duty loads

2013 ◽  
Vol 9 (1) ◽  
pp. 42-58
Author(s):  
Tudor Bugnariu
Keyword(s):  
Waste Treatment ◽  
Numerical Models ◽  
Limit State ◽  
Treatment Plant ◽  
Structural Response ◽  
Soil Mass ◽  
Ultimate Limit State ◽  
Element Analysis ◽  
Waste Treatment Plant ◽  
Water Waste

Abstract The paper refers to a structural finite element analysis on the reservoirs for sludge fermentation subjected to static in-duty loads, at Glina Water Waste Treatment Plant. The purpose was to assess the stress and deformation states in subsequent erection and service conditions, to verify the design provisions and to emphasize the sensitivities, for a structure which was designed in the ‘80s based on analytical procedures. The results obtained on the numerical models highlight the importance of the soil-structure interaction, in peculiar the one influenced by the soil mass deformability, on the overall structural response. Based on the calculated stresses, all structural components were verified according to the actual design codes at the ultimate limit state and the service limit state (water tightness/crack emergence).

scholarly journals Reliability of Buried Pipes in Heterogeneous Soil Subjected to Seismic Loads

2021 ◽  
Vol 11 (1) ◽  
pp. 6708-6713
Author(s):  
H. Benzeguir ◽  
S. M. Elachachi ◽  
D. Nedjar ◽  
M. Bensafi
Keyword(s):  
Structural Reliability ◽  
Limit State ◽  
Bending Moment ◽  
Longitudinal Direction ◽  
Point Of View ◽  
Ultimate Limit State ◽  
Buried Pipe ◽  
Limit States ◽  
Ground Acceleration ◽  
Buried Pipes

Dysfunctions and failures of buried pipe networks, like sewer networks, are studied in this paper from the point of view of structural reliability and heterogeneity of geotechnical conditions in the longitudinal direction. Combined soil spatial variability and Peak Ground Acceleration (PGA) induce stresses and displacements. A model has been developed within the frame of geostatistics and a mechanical description of the soil–structure interaction of a set of buried pipes with connections resting on the soil by a two-parameter model (Pasternak model). Structural reliability analysis is performed considering two limit states: Serviceability Limit State (SLS), related to large "counter slope" in a given pipe, and Ultimate Limit State (ULS), corresponding to bending moment.

scholarly journals EXAMPLE OF GRAGUAL TRANSFORMATION OF STIFFNESS MATRIX AND MAIN SET OF EQUATIONS AT ADDITIONAL FINITE ELEMENT METHOD

2020 ◽  
Vol 16 (2) ◽  
pp. 14-25
Author(s):  
Anna Ermakova
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stiffness Matrix ◽  
Limit State ◽  
Ultimate Limit State ◽  
Nonlinear Properties ◽  
Design Diagram ◽  
Ultimate Limit ◽  
Gradual Transformation ◽  
Element Method

The paper considers the example of gradual transformation of the stiffness matrix and the main set of equations at Additional Finite Element Method (AFEM). It is corresponded to the increase of load and the ideal failure model of structure. AFEM uses the additional design diagrams and additional finite elements (AFE) for this operation. This process is illustrated by the transformation of design diagram of bended concrete console from the beginning of its loading to the collapse. The structure reveals four physical nonlinear properties before the ultimate limit state. Every nonlinear property appears under the action of corresponded load. The stiffness matrix and the set of equations are changed under influence of the value of load and the presence of observed nonlinear properties at this moment.

Sign in / Sign up

Export Citation Format

Share Document