Various stress return algorithms in elastoplastic analyses using the finite element method require the evaluation of the contact (or penetration) stress state (Figure 1), defining…
Abstract
Various stress return algorithms in elastoplastic analyses using the finite element method require the evaluation of the contact (or penetration) stress state (Figure 1), defining the transition from elastic to elastoplastic behaviour. Various iterative schemes are commonly used to evaluate contact stress state with a great degree of precision, as subsequent analysis process (forward Euler, mid‐point rule stress return scheme) is greatly affected by the evaluation of the contact stress state, as has been stressed by several authors.
Hua‐Peng Chen and Nenad Bicanic
The paper aims to identify both the location and severity of damage in complex framed buildings using limited noisy vibration measurements. The study aims to directly adopt…
Abstract
Purpose
The paper aims to identify both the location and severity of damage in complex framed buildings using limited noisy vibration measurements. The study aims to directly adopt incomplete measured mode shapes in structural damage identification and effectively reduce the influence of measurement errors on predictions of structural damage.
Design/methodology/approach
Damage indicators are properly chosen to reflect both the location and severity of damage in framed buildings at element level for braces and at critical point level for beams and columns. Basic equations for an iterative solution procedure are provided to be solved for the chosen damage indicators. The Tikhonov regularisation method incorporating the L‐curve criterion for determining the regularisation parameter is employed to produce stable and robust solutions for damage indicators.
Findings
The proposed method can correctly assess the quantification of structural damage at specific locations in complex framed buildings using only limited information on modal data measurements with errors, without requiring mode shape expansion techniques or model reduction processes.
Research limitations/implications
Further work may be needed to improve the accuracy of inverse predictions for very small structural damage from noisy measurements.
Practical implications
The paper includes implications for the development of reliable techniques for rapid and on‐line damage assessment and health monitoring of framed buildings.
Originality/value
The paper offers a practical approach and procedure for correctly detecting structural damage and assessing structural condition from limited noisy vibration measurements.
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William Algaard, Alan Agar and Nenad Bicanic
A novel integral form time‐integration algorithm for pseudodynamic testing is proposed, based on the Newmark implicit algorithm. The scheme builds on the recently proposed…
Abstract
A novel integral form time‐integration algorithm for pseudodynamic testing is proposed, based on the Newmark implicit algorithm. The scheme builds on the recently proposed integral form of the Newmark explicit algorithm which exhibits improved abilities to handle rapidly varying loads and stiffness properties during pseudodynamic testing, but displays some numerical damping and conditional stability. The enhancement is based on the inclusion of an additional term in the displacement predictor, which not only renders the algorithm more consistent, but it eliminates numerical damping and makes the algorithm unconditionally stable.
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Hillal Ayas, Mohamed Chabaat and Lyes Amara
The purpose of this paper is to introduce a new numerical approach for studying a cantilever bar having a transverse crack. The crack is modeled by an elastic longitudinal spring…
Abstract
Purpose
The purpose of this paper is to introduce a new numerical approach for studying a cantilever bar having a transverse crack. The crack is modeled by an elastic longitudinal spring with a stiffness K according to Castiglione’s theorem.
Design/methodology/approach
The bar is excited by different longitudinal impulse forces. The considered problem based on the differential equation of motion is solved by the method of characteristics (MOC) after splitting the second-order motion equation into two first-order equivalent equations.
Findings
In this study, effects of the crack size and crack’s position on the reflected waves from the crack are investigated. The results indicate that the presence of the crack in the cantilever bar generates additional waves caused by the reflection of the incident wave by the crack.
Originality/value
A numerical approach developed in this paper is used for detecting the extent of the damage in cracked bars by the measurement of the difference between the dynamic response of an uncracked bar and a cracked bar.
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Giovanna Lilliu and Alberto Meda
Fire analysis of precast segmental tunnels involves several problems, mainly related to the soil-structure interaction during fire exposure, coupled with material degradation…
Abstract
Fire analysis of precast segmental tunnels involves several problems, mainly related to the soil-structure interaction during fire exposure, coupled with material degradation. Temperature increase in the tunnel is the cause of thermal expansion of the lining, which is resisted by the soil pressure. Furthermore, the increase of temperature in the lining leads to severe damage to the reinforced concrete precast elements, which can jeopardise structural safety.
This problem has been analysed using an ideal case of a precast segmental tunnel excavated in a stratified soil. The analysis has been conducted with a commercial nonlinear FE element code. Initially, excavation of the tunnel was modelled in order to predict stresses in the lining due to the soil pressure and eventually fire exposure was considered. The reinforced concrete lining was modelled with a crack model in order to simulate the actual behaviour.
Results show the importance of considering the interaction with the soil and the degradation of the concrete lining.
H. Tschöpe, P. Wriggers and E. Oñate
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical…
Abstract
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical point detection methods to problems with inequality constraints originating from damage and contact. A simple bilinear model is considered for the damage problems. A bilateral, frictionless contact formulation is used for the contact problems. Among the critical point detection methods the focus is laid on the critical displacement method and the extended system. At first a possible combination of both methods is evaluated by applying them to damage problems. A prediction method based on the extended system is developed to facilitate the comparison of both methods. Secondly, the extended system is used as a computation method for critical points in two‐dimensional contact problems.
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Particle scale simulation of industrial particle flows using discrete element method (DEM) offers the opportunity for better understanding the flow dynamics leading to…
Abstract
Particle scale simulation of industrial particle flows using discrete element method (DEM) offers the opportunity for better understanding the flow dynamics leading to improvements in equipment design and operation that can potentially lead to large increases in equipment and process efficiency, throughput and/or product quality. Industrial applications can be characterized as large, involving complex particulate behaviour in typically complex geometries. In this paper, with a series of examples, we will explore the breadth of large scale modelling of industrial processes that is currently possible. Few of these applications will be examined in more detail to show how insights into the fundamentals of these processes can be gained through DEM modelling. Some examples of our collaborative validation efforts will also be described.