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Volume 26, Number 5, November 2020

A design method of a Multiple Tuned Mass Damper (MTMD) system is presented for wind induced vibration control of a cable-supported roof structure. Modal contribution analysis is carried out to determine the dominating modes of the structure for the MTMD design. Two MTMD systems are developed for two most dominating modes. Each MTMD system is composed of multiple TMDs with small masses spread at multiple locations with large responses in the corresponding mode. Frequencies of TMDs are distributed uniformly within a range around the dominating frequencies of the roof structure to enhance the robustness of the MTMD system against uncertainties of structural frequencies. Parameter optimizations are carried out by minimizing objective functions regarding the structural responses, TMD strokes, robustness and mass cost. Two optimization approaches are used: Single Objective Approach (SOA) using Sequential Quadratic Programming (SQP) with multi-start method and Multi-Objective Approach (MOA) using Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The computation efficiency of the MOA is found to be superior to the SOA with consistent optimization results. A Pareto optimal front is obtained regarding the control performance and the total weight of the TMDs, from which several specific design options are proposed. The final design may be selected based on the Pareto optimal front and other engineering factors.

Key Words
multiple tuned mass dampers; vibration control; cable-supported roof; SQP with multi-start; NSGA-II

(1) X.C. Wang, Q. Teng, Y.F. Duan, C.B. Yun, S.L. Dong and W.J. Lou:
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China

One of the powerful data management tools is Building Information Modeling (BIM) which operates through obtaining, recalling, sharing, sorting and sorting data and supplying a digital environment of them. Employing SHM, a BIM in monitoring systems, would be an efficient method to address their data management problems and consequently optimize the economic aspects of buildings. The recording of SHM data is an effective way for engineers, facility managers and owners which make the BIM dynamic through the provision of updated information regarding the occurring state and health of different sections of the building. On the other hand, digital transformation is a continuous challenge in construction. In a cloud-based BIM platform, environmental and localization data are integrated which shape the Internet-of-Things (IoT) method. In order to improve work productivity, living comfort, and entertainment, the IoT has been growingly utilized in several products (such as wearables, smart homes). However, investigations confronting the integration of these two technologies (BIM and IoT) remain inadequate and solely focus upon the automatic transmission of sensor information to BIM models. Therefore, in this composition, the use of BIM based on SHM and IOT is reviewed and the economic application is considered.

Key Words
Building Information Modeling (BIM); SHM; IOT; sensor; network

(1) Yan Cao:
School of Mechatronic Engineering, Xi'an Technological University, Xi'an , 710021 China
(2) Sepideh Miraba Miraba:
Department of Architecture, Soore University, Tehran, Iran
(3) Shervin Rafiei Rafiei:
Department of Construction Engineering and Management, Amirkabir University of Technology, Tehran, Iran
(4) Aria Ghabussi Ghabussi:
Department of Civil, Environmental and Construction Engineering, Texas Tech University, Lubbock, TX 79409, USA
(5) Fateme Bokaei Bokaei:
Department of Civil and Architectural E ngineering, Eyvanekey University, Tehran, Iran
(6) Shahrizan Baharom Baharom:
Department of Civil Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan, Malaysia
(7) Pedram HaramipourHaramipour:
Department of Architecture, Shahid Beheshti University, Tehran, Iran
(8) Hamid Assilzadeh:
Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

For vibration control of stay cables in cable-stayed bridges, viscous dampers are frequently used, and they are regularly installed between the cable and the bridge deck. In practice, neoprene rubber bushings (or of other types) are also widely installed inside the cable guide pipe, mainly for reducing the bending stresses of the cable near its anchorages. Therefore, it is important to understand the effect of the bushings on the performance of the external damper. Besides, for long cables, external dampers installed at a single position near a cable end can no longer provide enough damping due to the sag effect and the limited installation distance. It is thus of interest to improve cable damping by additionally installing dampers inside the guide pipe. This paper hence studies the combined effects of an external damper and an internal damper (which can also model the bushings) on a stay cable. The internal damper is assumed to be a High Damping Rubber (HDR) damper, and the external damper is considered to be a viscous damper with intrinsic stiffness, and the cable sag is also considered. Both the cases when the two dampers are installed close to one cable end and respectively close to the two cable ends are studied. Asymptotic design formulas are derived for both cases considering that the dampers are close to the cable ends. It is shown that when the two dampers are placed close to different cable ends, their combined damping effects are approximately the sum of their separate contributions, regardless of small cable sag and damper intrinsic stiffness. When the two dampers are installed close to the same end, maximum damping that can be achieved by the external damper is generally degraded, regardless of properties of the HDR damper. Field tests on an existing cable-stayed bridge have further validated the influence of the internal damper on the performance of the external damper. The results suggest that the HDR is optimally placed in the guide pipe of the cable-pylon anchorage when installing viscous dampers at one position is insufficient. When an HDR damper or the bushing has to be installed near the external damper, their combined damping effects need to be evaluated using the presented methods.

Key Words
stay cable; vibration control; sag effect; viscous damper; HDR damper; modal damping; parameter optimization

(1) Fangdian Di, Limin Sun:
Department of Bridge Engineering, Tongji University, 1239 Siping Road, Shanghai, China
(2) Lin Chen:
State key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, China

Dynamic deflection monitoring is an essential and critical part of structural health monitoring for high-speed railway bridges. Two critical problems need to be addressed when using inclinometer sensors for such applications. These include constructing a general representation model of inclination-deflection and addressing the ill-posed inverse problem to obtain the accurate dynamic deflection. This paper provides a dynamic deflection monitoring method with the placement of optimal inclinometer sensors for high-speed railway bridges. The deflection shapes are reconstructed using the inclination-deflection transformation model based on the differential relationship between the inclination and displacement mode shape matrix. The proposed optimal sensor configuration can be used to select inclination-deflection transformation models that meet the required accuracy and stability from all possible sensor locations. In this study, the condition number and information entropy are employed to measure the ill-condition of the selected mode shape matrix and evaluate the prediction performance of different sensor configurations. The particle swarm optimization algorithm, genetic algorithm, and artificial fish swarm algorithm are used to optimize the sensor position placement. Numerical simulation and experimental validation results of a 5-span high-speed railway bridge show that the reconstructed deflection shapes agree well with those of the real bridge.

Key Words
high-speed railway bridge; dynamic deflection; optimal inclinometer sensor placement; inclination-deflection transformation; information entropy

(1) Shunlong Li, Xin Wang:
School of Transportation Science and Engineering, Harbin Institute of Technology, 73 Huanghe Road, 150090 Harbin, China
(2) Hongzhan Liu, Yi Zhuo, Wei Su, Hao Di:
China Railway Design Corporation, 300142 Tianjin, China

In this study, the experimental tests for the direct tensile strength measurement of Ultra-High Performance Concrete (UHPC) were numerically modeled by using the discrete element method (circle type element) and Finite Element Method (FEM). The experimental tests used for the laboratory tensile strength measurement is the Compressive-to-Tensile Load Conversion (CTLC) device. In this paper, the failure process including the cracks initiation, propagation and coalescence studied and then the direct tensile strength of the UHPC specimens measured by the novel apparatus i.e., CTLC device. For this purpose, the UHPC member (each containing a central hole) prepared, and situated in the CTLC device which in turn placed in the universal testing machine. The direct tensile strength of the member is measured due to the direct tensile stress which is applied to this specimen by the CTLC device. This novel device transferring the applied compressive load to that of the tensile during the testing process. The UHPC beam specimen of size 150 × 60 × 190 mm and internal hole of 75 × 60 mm was used in this study. The rate of the applied compressive load to CTLC device through the universal testing machine was 0.02 MPa/s. The direct tensile strength of UHPC was found using a new formula based on the present analyses. The numerical simulation given in this study gives the tensile strength and failure behavior of the UHPC very close to those obtained experimentally by the CTLC device implemented in the universal testing machine. The percent variation between experimental results and numerical results was found as nearly 2%. PFC2D simulations of the direct tensile strength measuring specimen and ABAQUS simulation of the tested CTLC specimens both demonstrate the validity and capability of the proposed testing procedure for the direct tensile strength measurement of UHPC specimens.

Key Words
ultra-high performance concrete; direct tensile strength; compressive to tensile load conversion; finite element method; discrete element method

(1) Hadi Haeri:
State Key Laboratory for Deep GeoMechanics and Underground Engineering, Beijing, 100083, China
(2) Nader Mirshekari:
Department of Civil Engineering, Islamic Azad University, Vramin-Pishva branch, Pishva, Iran
(3) Vahab Sarfarazi:
Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
(4) Mohammad Fatehi Marji:
Department of Mine Exploitation Engineering, Faculty of Mining and metallurgy, Institute of Engineering, Yazd University, Yazd, Iran

Solar towers, which often has a large aspect ratio and low fundamental natural frequency, were extremely prone to large amplitude of wind-induced vibrations, especially Vortex-Induced Vibration (VIV). A tiny Tuned Mass Damper (TMD) with conveniently adjustable eddy current damping was specially designed and manufactured for elastic wind tunnel tests of a solar tower. A series of numerical simulations by using the COMSOL software were conducted to determine three key parameters, including the thickness of the back iron plate and the conductive plate (Tb and Tc), the distance between the magnet and the conductive plate (Td). Based on the results of numerical simulations, a tiny TMD was manufactured and its structural parameters were experimentally identified. The optimized values of the tiny TMD can be conveniently realized. The tiny TMD was installed at the top of the elastic test model of a 243-meter-high solar tower, and a series of wind tunnel tests were carried out to examine the effectiveness of the TMD in suppressing wind-induced responses of the test model. The results showed that the wind-induced responses could be obviously reduced by the TMD, especially in the cross-wind direction. The cross-wind RMS and peak responses at the critical wind velocity can be reduced by about 86% and 75%, respectively. However, the maximum reduction of the responses at the design wind velocity is about 45%, obviously less than that at the critical wind velocity.

Key Words
solar tower; tuned mass damper; eddy current damping; vortex-induced vibration; wind tunnel tests

(1) Min Liu, Shouying Li, Zhengqing Chen:
Key Laboratory for Wind and Bridge Engineering of Hunan Province, College of Civil Engineering, Hunan University, Changsha 410082, China

In this paper, nonlinear vibration behaviors of multi-phase Magneto-Electro-Elastic (MEE) doubly-curved nanoshells have been studied employing Jacobi elliptic function method. The doubly-curved nanoshell has been modeled by using nonlocal elasticity and classic shell theory. An exact estimation of nonlinear vibrational behavior of smart doubly-curved nanoshell has been obtained via Jacobi elliptic function method. This method can incorporate the influences of higher order harmonics leading to an exact estimation of nonlinear vibration frequency. It will be indicated that nonlinear vibrational frequency of doubly-curved nanoshell relies on nonlocal effect, material composition, curvature radius, center deflection and electro-magnetic field.

Key Words
doubly-curved shell; nonlinear vibration; Jacobi elliptic function; magneto-electro-elastic material; nonlocal elasticity

(1) Sayed Sajad Mirjavadi, Masoud Forsat, A.M.S Hamouda:
Department of Mechanical and Industrial Engineering, Qatar University, P.O. Box 2713, Doha, Qatar
(2) Hassan Bayani:
Department of Electrical Engineering, Instituto Superior Técnico, UTL, Lisbon, Portugal
(3) Navid Khoshtinat:
Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
(4) Mohammad Reza Barati:
Fidar Project Qaem Company, Darvazeh Dolat, Tehran, Iran

The finite element solutions of thermal buckling load values of the graded sandwich curved shell structure are reported in this research using a higher-order kinematic model including the shear deformation effect. The numerical buckling temperature has been computed using an in-house specialized code (MATLAB environment) prepared in the framework of the current mathematical formulation. In addition, the mathematical model includes the excess structural distortion under the influence of elevated environment via Green-Lagrange nonlinear strain. The corresponding eigenvalue equation has been solved to predict the critical buckling temperature of the graded sandwich structure. The numerical stability and the accuracy of the current solution have been confirmed by comparing with the available published results. Thereafter, the model is extended to bring out the influences of structural parameters i.e. the curvature ratio, core-face thickness ratio, support conditions, power-law indices and sandwich types on the thermal buckling behavior of graded sandwich curved shell panels.

Key Words
FGM sandwich curved panels; HSDT; thermal buckling; FEM; MATLAB

(1) Brundaban Sahoo, Bamadev Sahoo:
Department of Mechanical Engineering, IIIT, Bhubaneswar: 751003, Odisha, India
(2) Nitin Sharma:
School of Mechanical Engineering, KIIT, Bhubaneswar: 751024, Odisha, India
(3) Kulmani Mehar:
Department of Mechanical Engineering, Madanapalle Institute of Technology and Science: 517325, Andhra Pradesh, India
(4) Subrata Kumar Panda:
Department of Mechanical Engineering, NIT, Rourkela: 769008, Odisha, India

A rotational pulse-echo ultrasonic propagation imager that can inspect cylindrical specimens for material nondestructive evaluations is proposed herein. In this system, a laser-generated ultrasonic bulk wave is used for inspection, which enables a clear visualization of subsurface defects with a precise reproduction of the damage shape and size. The ultrasonic waves are generated by a Q-switched laser that impinges on the outer surface of the specimen walls. The generated waves travel through the walls and their echo is detected by a Laser Doppler Vibrometer (LDV) at the same point. To obtain the optimal Signal-to-Noise Ratio (SNR) of the measured signal, the LDV requires the sensed surface to be at a right angle to the laser beam and at a predefined constant standoff distance from the laser head. For flat specimens, these constraints can be easily satisfied by performing a raster scan using a dual-axis linear stage. However, this arrangement cannot be used for cylindrical specimens owing to their curved nature. To inspect the cylindrical specimens, a circular scan technology is newly proposed for pulse-echo laser ultrasound. A rotational stage is coupled with a single-axis linear stage to inspect the desired area of the specimen. This system arrangement ensures that the standoff distance and beam incidence angle are maintained while the cylindrical specimen is being inspected. This enables the inspection of a curved specimen while maintaining the optimal SNR. The measurement result is displayed in parallel with the on-going inspection. The inspection data used in scanning are mapped from rotational coordinates to linear coordinates for visualization and post-processing of results. A graphical user interface software is implemented in C++ using a QT framework and controls all the individual blocks of the system and implements the necessary image processing, scan calculations, data acquisition, signal processing and result visualization.

Key Words
nondestructive material evaluation; laser ultrasonic; bulk wave propagation; rotational scan; cylinder inspection

(1) Hasan Ahmed, Young-Jun Lee, Jung-Ryul Lee:
Department of Aerospace Engineering, Korean Advanced Institute for Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea

This study aims at reporting a systematic procedure for evaluating the static and dynamic structural performance of steel bridges based on a short-period structural health monitoring measurement. Sungsu bridge located in Korea is considered as a case study presenting the most recent tests carried out to examine the bridge condition. Short-period measurements of Structural Health Monitoring (SHM) system were used during the bridge testing phase. A novel symmetry index is introduced using statistical analyses of deflection and strain measurements. Frequency Domain Decomposition (FDD) is implemented to the strain measurements to estimate the bridge mode shapes and damping ratios. Furthermore, Markov Chain Monte Carlo (MCMC) is also implemented to examine the reliability of bridge performance while ambient design trucks are in static or moving at different speeds. Strain, displacement and acceleration were measured at selected locations on the bridge. The results show that the symmetry index can be an efficient and useful measure in assessing the steel bridge performance. The results from the used method reveal that the performance of the Sungsu bridge is safe under operational conditions.

Key Words
bridge; output-only; behavior; frequency domain decomposition complex

(1) Mosbeh R. Kaloop, Jong Wan Hu, Dongwook Kim:
Department of Civil and Environmental Engineering, Incheon National University, Korea
(2) Mosbeh R. Kaloop, Jong Wan Hu:
Incheon Disaster Prevention Research Center, Incheon National University, Incheon, Korea
(3) Mosbeh R. Kaloop:
Public Works and Civil Engineering Department, College of Engineering, Mansoura University, Egypt
(4) Mohamed Elsharawy:
Civil and Construction Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Saudi Arabia
(5) Basem Abdelwahed:
Structural Engineering Department, College of Engineering, Mansoura University, Egypt

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