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CONTENTS
Volume 27, Number 5, November 2018
 

Abstract
This study presents the reliability assessment of a 100.5 m tall reinforced concrete chimney at a glass factory under wind loading by using vibration-based identified modal values. Ambient vibration measurements were recorded and modal values such as frequencies, shapes and damping ratios were identified by using Enhanced Frequency Domain Decomposition (EFDD) method. Afterwards, Finite Element Model (FEM) of the chimney was verified based on identified modal parameters. Reliability assessment of the chimney under wind loading was performed by obtaining the exceedance probability of demand to capacity distribution. Demand distribution of the chimney was developed under repetitive seeds of multivariate stochastic wind fields generated along the height of chimney. Capacity distribution of the chimney was developed by Monte Carlo simulation. Finally, it was found that reliability of the chimney is lower than code suggested limit values.

Key Words
industrial chimney; system identification; wind loading; reliability analysis

Address
M. Orcun Tokuc: Tekfen Construction, Istanbul, Turkey
Serdar Soyoz: Department of Civil Engineering, Bogazici University, Istanbul, Turkey

Abstract
The prediction of multimode flutter relies, to a larger extent than bimodal flutter, on accurate modeling of the self-excited forces since it is challenging to perform experimental validation by using aeroelastic tests for a multimode case. This paper sheds some light on the accuracy of predicted self-excited forces by comparing numerical predictions of self-excited forces with measured forces from wind tunnel tests considering the flutter vibration mode. The critical velocity and the corresponding flutter vibration mode of the Hardanger Bridge are first determined using the classical multimode approach. Then, a section model of the bridge is forced to undergo a motion corresponding to the flutter vibration mode at selected points along the bridge, during which the forces that act upon it are measured. The measured self-excited forces are compared with numerical predictions to assess the uncertainty involved in the modeling. The self-excited lift and pitching moment are captured in an excellent manner by the aerodynamic derivatives. The self-excited drag force is, on the other hand, not well represented since second-order effects dominate. However, the self-excited drag force is very small for the cross-section considered, making its influence on the critical velocity marginal. The self-excited drag force can, however, be of higher importance for other cross-sections.

Key Words
forced vibration test; flutter; bridge aerodynamics; section model; aerodynamic derivatives

Address
Bartosz Siedziakoand Ole Oiseth:Department of Structural Engineering, Norwegian University of Science and Technology, Richard Birkelands vei 1A, 7491 Trondheim, Norway



Abstract
This work examines vibration and bending response of carbon nanotube-reinforced composite plates resting on the Pasternak elastic foundation. Four types of distributions of uni-axially aligned single-walled carbon nanotubes are considered to reinforce the plates. Analytical solutions determined from mathematical formulation based on hyperbolic shear deformation plate theory are presented in this study. An accuracy of the proposed theory is validated numerically by comparing the obtained results with some available ones in the literature. Various considerable parameters of carbon nanotube volume fraction, spring constant factors, plate thickness and aspect ratios, etc. are considered in the present investigation. According to the numerical examples, it is revealed that the vertical displacement of the plates is found to diminish as the increase of foundation parameters; while, the natural frequency increase as the increment of the parameters for every type of plate.

Key Words
bending; vibration; CNTRC plate; plate theory

Address
Boumediene Bakhadda: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria;
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Mohamed Bachir Bouiadjra: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes,
Faculté de Technologie, Département de génie civil, Algeria;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Fouad Bourada: Département de Génie Civil, Institut de Technologie, Centre Universitaire de Ain Témouchent, Algeria
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
5Centre Universitaire Ahmed Zabana de Relizane, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia







Abstract
The physical infrastructure of the power systems, including the high-voltage transmission towers and lines as well as the poles and wires for power distribution at a lower voltage level, is critical for the resilience of the community since the failures or nonfunctioning of these structures could introduce large area power outages under the extreme weather events. In the current engineering practices, single circuit lattice steel towers linked by transmission lines are widely used to form power transmission systems. After years of service and continues interactions with natural and built environment, progressive damages accumulate at various structural details and could gradually change the structural performance. This study is to evaluate the typical existing transmission tower-line system subjected to synoptic winds (atmospheric boundary layer winds). Effects from the possible corrosion penetration on the structural members of the transmission towers and the aerodynamic damping force on the conductors are evaluated. However, corrosion in connections is not included. Meanwhile, corrosion on the structural members is assumed to be evenly distributed. Wind loads are calculated based on the codes used for synoptic winds and the wind tunnel experiments were carried out to obtain the drag coefficients for different panels of the transmission towers as well as for the transmission lines. Sensitivity analysis is carried out based upon the incremental dynamic analysis (IDA) to evaluate the structural capacity of the transmission tower-line system for different corrosion and loading conditions. Meanwhile, extreme value analysis is also performed to further estimate the short-term extreme response of the transmission tower-line system.

Key Words
ransmission tower-line system; wind tunnel experiments; dynamic analysis; capacity curves; extreme value analysis

Address
Huawei Niu: Wind Engineering Research Center, Hunan University, Changsha, China
Xuan Li and Wei Zhang: Department of Civil and Environmental Engineering, University of Connecticut, Storrs, Connecticut 06269, USA

Abstract
Tall buildings are subjected to wind loading that can cause excessive wind-induced vibration. This vibration can affect the activities of the inhabitants of a building and in some cases fear for safety. Many codes and standards propose the use of curves of perception of acceleration that can be used to verify the serviceability limit state; however, these curves of perception do not take into account the uncertainty in wind-climate, structural properties, perception of motion and maximum response. The main objective of this study is to develop an empirical expression that includes these uncertainties in order to be incorporated into a simple procedure to evaluate the wind-induced acceleration in tall buildings. The use of the proposed procedure is described with a numerical example of a tall building located in Mexico.

Key Words
wind-induced motion; tall buildings; serviceability limit state; mean peak acceleration; Mexico

Address
Adrian Pozos-Estrada: Instituto de Ingeniería, Universidad Nacional Autónoma de México, Coyoacán C.P. 04510, Mexico City, Mexico

Abstract
In this paper, stress distribution for a structurally stable greenhouse is considered in the present paper with subsequent investigation into the detailed stress distribution contour with the variation of self-weight and wind pressure level designation method under wind velocity of less than 30 m/sec. For reliable analysis, wind pressure coefficients of a single greenhouse unit were modeled and compared with experiment with correlation coefficient greater than 0.99. Wind load level was designated twofold: direct mapping of fluid dynamic analysis and conversion of modeled results into wind pressure coefficients (CP). Finally, design criteria of EN1991-1-4 and NEN3859 were applied in terms of their wind pressure coefficients for comparison. CP of CFD result was low in the most of the modeled area but was high only in the first roof wind facing and the last lee facing areas. Besides, structural analysis results were similar in terms of stress distribution as per EN and direct mapping while NEN revealed higher level of stress for the last roof area. The maximum stress levels are arranged in decreasing order of mapping, EN, and NEN, generating 8% error observed between the EN and mapping results under 30 m/sec of wind velocity. On the other hand, effect of dead weight on the stress distribution was investigated via variation of high stress position with wind velocity, confirming shift of such position from the center to the forward head wind direction. The sensitivity of stress for wind velocity was less than 0.8% and negligible at wind velocity greater than 20 m/sec, thus eliminating self-weight effect.

Key Words
computational fluid dynamics (CFD); stress distribution; venlo-type greenhouse; wind load; wind pipe; Wind pressure coefficients (CP)

Address
Deog-jae Hur, Jung-Hun Noh and Hyun ju Lee: Research & Business Corporation Center, Institute for Advanced Engineering, 175-28,Goan-ro, 51 beon-gil, Beagam-myeon,
Cheoin-gu,Yongin-si, Gyeonggi-do, Republic of Korea
Hyoung woon Song: Plant Engineering Division, Institute for Advanced Engineering, 175-28,Goan-ro, 51 beon-gil, Beagam-myeon, Cheoin-gu,Yongin-si, Gyeonggi-do, Republic of Korea



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