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CONTENTS
Volume 26, Number 1, January 2018
 

Abstract
This research studies the dynamic analysis of a concrete column reinforced with titanium dioxide (TiO2) nanoparticles under earthquake load. The effect of nanoparticles accumulation in a region of concrete column is examined using Mori-Tanaka model. The structure is simulated mathematically based on the theory of sinusoidal shear deformation theory (SSDT). By calculating strain-displacement and stress-strain relations, the system energies include potential energy, kinetic energy, and external works are derived. Then, using the Hamilton\'s principle, the governing equations for the structure are extracted. Using these equations, the response of the concrete column under earthquake load is investigated using the numerical methods of differential quadrature (DQ) and Newark. The purpose of this study is to study the effects of percentage of nanoparticles, nanoparticles agglomeration, geometric parameters and boundary conditions on the dynamic response of the structure. The results indicate that by increasing the volume percent of TiO2 nanoparticles, the maximum dynamic deflection of the structure decreases.

Key Words
seismic response; concrete column; TiO2 nanoparticles; DQ; Newmark method

Address
Morteza Sharifi, Reza Kolahchi and Mahmood Rabani Bidgoli: Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran

Abstract
Full-scale measurements of wind action on the open roof structure of the WuXi grand theater, which is composed of eight large-span free-form leaf-shaped space trusses with the largest span of 76.79 m, were conducted during the passage of Typhoons HaiKui and SuLi. The wind pressure field data were continuously and simultaneously monitored using a wind pressure monitoring system installed on the roof structure during the typhoons. A detailed analysis of the field data was performed to investigate the characteristics of the fluctuating wind pressure on the open roof, such as the wind pressure spectrum, spatial correlation coefficients, peak wind pressures and non-Gaussian wind pressure characteristics, under typhoon conditions. Three classical methods were used to calculate the peak factors of the wind pressure on the open roof, and the suggested design method and peak factors were given. The non-Gaussianity of the wind pressure was discussed in terms of the third and fourth statistical moments of the measured wind pressure, and the corresponding indication of the non-Gaussianity on the open roof was proposed. The result shows that there were large pulses in the time-histories of the measured wind pressure on Roof A2 in the field. The spatial correlation of the wind pressures on roof A2 between the upper surface and lower surface is very weak.When the skewness is larger than 0.3 and the kurtosis is larger than 3.7, the wind pressure time series on roof A2 can be taken as a non-Gaussian distribution, and the other series can be taken as a Gaussian distribution.

Key Words
large-span roof; typhoon; full-scale measurements; peak wind pressure; wind pressure spectrum

Address
Ruoqiang Feng, Fengcheng Liu and Qi Cai: School of Civil Engineering, Member of the Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast Univ., Nanjing, China
Guirong Yan: Department of Civil, Architectural and Environmental Engineering, Missouri Univ. of Science and Technology, Rolla, MO, USA
Jiabing Leng: Zhongnan Construction Group Limited Company, Haimen of Jiangsu province, China

Abstract
This paper presents a beam finite element model of a vibrate wind blade in large elastic deformation subjected to the aerodynamic, centrifugal, gyroscopic and gravity loads. The gyroscopic loads applied to the blade are induced by her simultaneous vibration and rotation. The proposed beam finite element model is based on a simplex interpolation method and it is mainly intended to the numerical analysis of wind blades vibration in large elastic deformation. For this purpose, the theory of the sheared beams and the finite element method are combined to develop the algebraic equations system governing the three-dimensional motion of blade vibration. The applicability of the theoretical approach is elucidated through an original case study. Also, the static deformation of the used wind blade is assessed by appropriate software using a solid finite element model in order to show the effectiveness of the obtained results. To simulate the nonlinear dynamic response of wind blade, the predictor-corrector Newmark scheme is applied and the stability of numerical process is approved during a large time of blade functioning. Finally, the influence of the modified geometrical stiffness on the amplitudes and frequencies of the wind blade vibration induced by the sinusoidal excitation of gravity is analyzed.

Key Words
vibrate wind blade; large elastic deformation; finite element method

Address
Hedi Hamdi: Applied Mechanics and Engineering Laboratory, National Engineering School of Tunis,University of Tunis El Manar, 2092 Manar II, Tunis, Tunisia
Khaled Farah: Civil Engineering Laboratory, National Engineering School of Tunis,University of Tunis El Manar, 2092 Manar II, Tunis, Tunisia



Abstract
This paper describes the effect of different testing parameters (configuration of infrastructure and truck position on road) on truck aerodynamic coefficients under cross wind conditions, by means of a numerical approach known as Large Eddy Simulation (LES). In order to estimate the air flow behaviour around both the infrastructure and the truck, the filtered continuity and momentum equations along with the Smagorinsky–Lilly model were solved. A solution for these non-linear equations was approached through the finite volume method (FVM) and using temporal and spatial discretization schemes. As for the results, the aerodynamic coefficients acting on the truck model exhibited nearly constant values regardless of the Reynolds number. The flat ground is the infrastructure where the rollover coefficient acting on the truck model showed lowest values under cross wind conditions (yaw angle of 90), while the worst infrastructure studied for vehicle stability was an embankment with downward-slope on the leeward side. The position of the truck on the road and the value of embankment slope angle that minimizes the rollover coefficient were determined by successfully applying the Response Surface Methodology.

Key Words
cross wind; embankments; heavy vehicles aerodynamics; Large Eddy Simulation (LES); Finite Volume Method (FVM); Computational Fluid Dynamics (CFD)

Address
Alejandro Alonso-Estébanez and Pablo Pascual-Muñoz: Department of Transport, Projects and Process Technology, University of Cantabria, Avda. Los Castros s/n, 39005 Santander, Spain
Juan J. del Coz Díaz and Felipe P. Álvarez Rabanal: Department of Construction, GICONSIME Research Team, University of Oviedo, Departmental Building 7, 33204 Gijón, Spain
Paulino J. García Nieto: Department of Mathematics, Faculty of Sciences, University of Oviedo, 33007 Oviedo, Spain

Abstract
Wind damage of urban trees arises to be a serious issue especially in the typhoon-prone areas. As a family of tree species widely-planted in Southeast China, the structural behaviors of Plane tree is investigated. In order to accommodate the complexities of tree morphology, a fractal theory based finite element modeling method is proposed. On-site measurement of Plane trees is performed for physical definition of structural parameters. It is revealed that modal frequencies of Plane trees distribute in a manner of grouped dense-frequencies; bending is the main mode of structural failure. In conjunction with the probability density evolution method, the fragility assessment of urban trees subjected to wind excitations is then proceeded. Numerical results indicate that small-size segments such as secondary branches feature a relatively higher failure risk in a low wind level, and a relatively lower failure risk in a high wind level owing to windward shrinks. Besides, the trunk of Plane tree is the segment most likely to be damaged than other segments in case of high winds. The failure position tends to occur at the connection between trunk and primary branches, where the logical protections and reinforcement measures can be implemented for mitigating the wind damage.

Key Words
finite element modeling; fractal theory; grouped dense-frequencies; fragility assessment; probability density evolution method; Plane tree

Address
Yongbo Peng: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;
Shanghai Institute of Disaster Prevention and Relief, Tongji University, Shanghai 200092, China
Zhiheng Wang: Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA
Xiaoqiu Ai:Shanghai Institute of Disaster Prevention and Relief, Tongji University, Shanghai 200092, China



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