• Wind and Structures
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• 제14권2호
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• pp.133-151
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• 2011

For a detailed investigation of the dynamic behaviour of slender bridges under wind action especially the motion-induced fluid forces should be available not only for harmonic motions but also for more general ones. If linear transfer behaviour is assumed, the force-displacement relation for almost arbitrary motions can be handled in the frequency domain using aerodynamic transfer functions. In aerospace engineering as well as in bridge engineering, these functions are usually approximated by special kinds of complex-valued rational functions which depend on complex frequencies. The quality of this approximation is evaluated for several bridge cross sections in this article. It is shown that rational functions are for some sections scarcely suitable to realistically represent the transfer behaviour of motion-induced aerodynamic forces for arbitrarily complex frequencies.

• Geomechanics and Engineering
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• 제15권3호
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• pp.861-868
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• 2018

Recent occurrences of earthquakes in Korea have increased the importance of considering how horizontal loads affect foundation structures as a result of wind and dynamic impact. However, to date, there are few studies on tunnelling-induced behaviour of ground and pile structures simultaneously subjected to horizontal and vertical loads. In this research, therefore, the behaviour of ground and single piles due to tunnelling were investigated through a laboratory model test. Three cases of horizontal loads were applied to the top of the pile. In addition, a numerical analysis was carried out to analyse and compare with the results from the laboratory model test.

• Wind and Structures
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• 제8권1호
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• pp.61-78
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• 2005

This paper presents results from an investigation of the structural behaviour of a very slender 90 m high steel chimney erected at V$\ddot{a}$xj$\ddot{o}$ in southern Sweden in 1995. The chimney is equipped with a mechanical friction-type damper at the top. Due to a mistake during erection and installation of the chimney the transport fixings of the damper were not released properly and the chimney developed extensive oscillations in the very first period of service. This caused a great number of fatigue cracks to occur within a few months of service. After the functioning of the damper had been restored and the fatigue cracks were repaired an extensive program was initiated in 1996 to monitor the structural behaviour of the chimney under wind loading. In the investigation data were collected for more than six years of continuous measurements and regular observations of the chimney. The data obtained have some general relevance with respect to wind data, behaviour of a slender structure under wind loading, and the effect of a mechanical damper. Also some theoretical studies were performed as part of the investigation of the chimney.

• Computers and Concrete
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• 제8권1호
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• pp.23-41
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• 2011

The behaviour of concrete confined by transverse reinforcement is a classical topic. Numerous studies have been conducted to establish the stress-strain relationships for concrete under various confining reinforcement arrangements. Many empirical and semi-empirical formulas exist. Simplified analytical models have also been proposed to evaluate the increase in the strength and ductility of confined concrete. However, relatively few studies have been conducted to utilise advanced computational models for a realistic simulation of the behaviour of concrete confined by transverse reinforcement. As a matter of fact, high fidelity simulations using the latest numerical solvers in conjunction with advanced material constitutive models can be a powerful means to investigating the mechanisms underlying the confining effects of different reinforcement schemes. This paper presents a study on the use of high fidelity finite element models for the investigation of the behaviour of concrete confined by stirrups, as well as the interpretation of the numerical results. The development of the models is described in detail, and the essential modelling considerations are discussed. The models are then validated by simulating representative experimental studies on short columns with different confining reinforcement schemes. The development and distribution of the confining stress and the subsequent increase in the axial strength are examined. The models are shown to be capable of reproducing the behaviour of the confined concrete realistically, paving a way for systematic parametric studies and investigation into complicated confinement, load combination, and dynamic loading situations.

• Smart Structures and Systems
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• 제15권6호
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• pp.1521-1542
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• 2015

The use of shape memory alloys (SMAs) in dynamical systems has an increasing importance in engineering especially due to their capacity to provide vibration reductions. In this regard, experimental tests are essential in order to show all potentialities of this kind of systems. In this work, SMA springs are incorporated in a dynamical system that consists of a one degree of freedom oscillator connected to a linear spring and a mass, which is also connected to the SMA spring. Two types of springs are investigated defining two distinct systems: a pseudoelastic and a shape memory system. The characterisation of the springs is evaluated by considering differential calorimetry scanning tests and also force-displacement tests at different temperatures. Free and forced vibration experiments are made in order to investigate the dynamical behaviour of the systems. For both systems, it is observed the capability of changing the equilibrium position due to phase transformations leading to hysteretic behaviour, or due to temperature changes which also induce phase transformations and therefore, change in stiffness. Both situations are investigated by promoting temperature changes and also pre-tension of the springs. This article shows several experimental tests that allow one to obtain a general comprehension of the dynamical behaviour of SMA systems. Results show the general thermo-mechanical behaviour of SMA dynamical systems and the obtained conclusions can be applied in distinct situations as in rotor-bearing systems.

• Steel and Composite Structures
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• 제2권1호
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• pp.67-84
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• 2002

Traffic decks of steel or composite motorway bridges sometimes provide the opportunity of using the composite action between an existing steel deck and a reinforced concrete plate (RC plate) in the process of rehabilitation, i.e., to increase the load-carrying capacity of the deck for concentrated traffic loads. The steel decks may be orthotropic decks or also unstiffened steel plates, which during the rehabilitation are connected with the RC plate by shear studs, such developing an improved local load distribution by the joint behaviour of the two plate elements. Investigations carried out, both experimentally and numerically, were performed in order to quantitatively assess the combined static behaviour and to qualitatively verify the usability of the structure for dynamic loading. The paper reports on the testing, the numerical simulation as well as the comparison of the results. Conclusions drawn for practical design indicated that the static behaviour of these structures may be very efficient and can also be analysed numerically. Further, the results gave evidence of a highly robust behaviour under fatigue equivalent cyclic traffic loading.

• Computers and Concrete
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• 제18권6호
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• pp.1195-1211
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• 2016

In this study, seismic behaviour of reinforced concrete buildings using the pushover and incremental dynamic analysis method was investigated. A numerical study was performed for a reinforced concrete frame building. Pushover analysis according to uniform and triangular load shapes and incremental dynamic analyses were performed for selected building. For the nonlinear analysis, three ground motion records were selected to ensure compatibility with the design spectrum defined in the Turkish Seismic Code. The maximum response, dynamic pushover curve, capacity curves, interstorey drifts and moment rotation curves for various element ends of the selected building were obtained. Results were compared each other and good correlation was obtained between the dynamic analyses envelope with static pushover curves for the building.

• Structural Engineering and Mechanics
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• 제15권6호
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• pp.653-668
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• 2003

Many papers which deal with the dynamic instability of shell-like structures under the STEP load have been published. But, there have been few papers related to the dynamic instability of hybrid cable domes. In this study, the dynamic instability of hybrid cable domes considering geometric nonlinearity is investigated by a numerical method. The characteristic structural behaviour of a cable dome shows a strong nonlinearity, so we determine the shape of a cable dome by applying initial stress and examine the indirect buckling mechanism under dynamic external forces. The dynamic critical loads are determined by the numerical integration of the nonlinear equation of motion, and the indirect buckling is examined by using the phase plane to investigate the occurrence of chaos.

• 한국정밀공학회지
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• 제3권2호
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• pp.91-101
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• 1986

This paper deals with the effect of static and dynamic cuttig force and the behaviour of drill life in drilling process. The experiments are performed with cemented carbide drills and high speed steel drills of 10mm in diameter and in an annealed SM45C. The conclusions are as follows (1) Dynamic cutting force is varied with the dept of hole. (2) Dynamic cutting forces of torque and thrust are increase with the increase in feed and cutting speed. (3) Chipping influence the dynamic cutting force of thrust than torque, and in the case of thrust, the amplitude is 3-7 times large than ordinary cutting state. (4) Prediction of drill life can be obtained from more easily the amplitude of static cutting force than that of dynamic cutting force.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.1045-1075
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• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.