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CONTENTS
Volume 23, Number 2, February 2019
 

Abstract
As one of the most important parameters in structural health monitoring, structural frequency has many advantages, such as convenient to be measured, high precision, and insensitive to noise. In addition, frequency-change-ratio based method had been validated to have the ability to identify the damage occurrence and location. However, building a precise enough finite elemental model (FEM) for the test structure is still a huge challenge for this frequency-change-ratio based damage detection technique. In order to overcome this disadvantage and extend the application for frequencies in structural health monitoring area, a novel method was developed in this paper by combining the cross-model cross-mode (CMCM) model updating algorithm with the frequency-change-ratio based method. At first, assuming the physical parameters, including the element mass and stiffness, of the test structure had been known with a certain value, then an initial to-be-updated model with these assumed parameters was constructed according to the typical mass and stiffness distribution characteristic of shear buildings. After that, this to-be-updated model was updated using CMCM algorithm by combining with the measured frequencies of the actual structure when no damage was introduced. Thus, this updated model was regarded as a representation of the FEM model of actual structure, because their modal information were almost the same. Finally, based on this updated model, the frequency-change-ratio based method can be further proceed to realize the damage detection and localization. In order to verify the effectiveness of the developed method, a four-level shear building was numerically simulated and two actual shear structures, including a three-level shear model and an eight-story frame, were experimentally test in laboratory, and all the test results demonstrate that the developed method can identify the structural damage occurrence and location effectively, even only very limited modal frequencies of the test structure were provided.

Key Words
cross-model cross-mode model updating algorithm; structural frequency-change-ratio based method; structural health monitoring; damage detection; shear buildings

Address
Yabin Liang, Qian Feng, Heng Li and Jian Jiang: Hubei Key Laboratory of Earthquake Early Warning, Institute of Seismology, CEA, Wuhan, China;
Wuhan Institute of Earthquake Engineering Co Ltd, Wuhan, China


Abstract
Impact forces induced by external object collisions can cause serious damages to civil engineering structures. While accurate and prompt identification of such impact forces is a critical task in structural health monitoring, it is not readily feasible for civil structures because the force measurement is extremely challenging and the force location is unpredictable for full-scale field structures. This study proposes a novel approach for identification of impact force including its location and time history using a small number of multi-metric observations. The method combines an augmented Kalman filter (AKF) and Genetic algorithm for accurate identification of impact force. The location of impact force is statistically determined in the way to minimize the AKF response estimate error at measured locations and then time history of the impact force is accurately constructed by optimizing the error co-variances of AKF using Genetic algorithm. The efficacy of proposed approach is numerically demonstrated using a truss and a plate model considering the presence of modelling error and measurement noises.

Key Words
augmented Kalman filter; genetic algorithm; strain gauges; accelerometers; impact force

Address
Muhammad M. Saleem: Department of Civil Engineering and Engineering Mechanics, The University of Arizona,
1209 E 2nd street Tucson, AZ 85719, USA;
Department of Civil Engineering, University of Engineering and Technology Lahore, G.T. Road Lahore, 54890, Pakistan
Hongki Jo: Department of Civil Engineering and Engineering Mechanics, The University of Arizona,
1209 E 2nd street Tucson, AZ 85719, USA


Abstract
This research deals with wave propagation of the functionally graded (FG) nano-beams based on the nonlocal elasticity theory considering surface and flexoelectric effects. The FG nano-beam is resting in Winkler-Pasternak foundation. It is assumed that the material properties of the nano-beam changes continuously along the thickness direction according to simple power-law form. In order to include coupling of strain gradients and electrical polarizations in governing equations of motion, the nonlocal non-classical nano-beam model containg flexoelectric effect is used. Also, the effects of surface elasticity, di-electricity and piezoelectricity as well as bulk flexoelectricity are all taken into consideration. The governing equations of motion are derived using Hamilton principle based on first shear deformation beam theory (FSDBT) and also considering residual surface stresses. The analytical method is used to calculate phase velocity of wave propagation in FG nano-beam as well as cut-off frequency. After verification with validated reference, comprehensive numerical results are presented to investigate the influence of important parameters such as flexoelectric coefficients of the surface, bulk and residual surface stresses, Winkler and shear coefficients of foundation, power gradient index of FG material, and geometric dimensions on the wave propagation characteristics of FG nano-beam. The numerical results indicate that considering surface effects/flexoelectric property caused phase velocity increases/decreases in low wave number range, respectively. The influences of aforementioned parameters on the occurrence cut-off frequency point are very small.

Key Words
flexoelectric; surface effects; residual surface stresses; functionally graded beam; flexoelectricity

Address
Ali Ghorbanpour Arani, Mahmoud Pourjamshidian and
Mohammad Arefi: Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Postal Code: 87317-53153, Kashan, Iran
M.R. Ghorbanpour Arani: Electrical Engineering Faculty, Amirkabir University of Technology, Tehran, Iran

Abstract
In this study, Semi-active Tuned Mass Dampers (STMDs) are employed in order to cover the prevailing uncertainties and promote the efficiency of the Tuned Mass Dampers (TMDs) to mitigate undesirable structural vibrations. The damping ratio is determined using type-1 and type-2 Fuzzy Logic Controllers (T1 and T2 FLC) based on the response of the structure. In order to increase the efficiency of the FLC, the output membership functions are optimized using genetic algorithm. The results show that the proposed FLC can reduce the sensitivity of STMD to excitation records. The obtained results indicate the best operation for T1 FLC among the other control systems when the uncertainties are neglected. According to the irrefutable uncertainties, three supplies for these uncertainties such as time delay, sensors measurement noises and the differences between real and software model, are investigated. Considering these uncertainties, the efficiencies of T1 FLC, ground-hook velocity-based, displacement-based and TMD reduce significantly. The reduction rates for these algorithms are 12.66%, 26.43%, 20.98% and 21.77%, respectively. However, due to nonlinear behavior and considering a range of uncertainties in membership functions, T2 FLC with 7.2% reduction has robust performance against uncertainties compared to other controlling systems. Therefore, it can be used in actual applications more confidently.

Key Words
semi-active tuned mass damper; fuzzy system; genetic algorithms; optimization; ground-hook control

Address
Meysam Ramezani: International Institute of Earthquake Engineering and Seismology, P.O. Box 19537-14453, Tehran, Iran
Akbar Bathaei and Seyed Mehdi Zahrai: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran

Abstract
The main objective of this study is to evaluate the true fracture energy and monitor the damage progression in steel fibre reinforced concrete (SFRC) specimens using acoustic emission (AE) features. Four point bending test is carried out using pre-notched plain and fibre reinforced (0.5% and 1% volume fraction) - concrete under monotonic loading. AE sensors are affixed at different locations of the specimens and AE parameters such as rise time, AE energy, hits, counts, amplitude and duration etc. are obtained. Using the captured and processed AE event data, fracture process zone is identified and the true fracture energy is evaluated. The AE data is also employed for tracing the damage progression in plain and fibre reinforced concrete, using both parametric- and signal- based techniques. Hilbert - Huang transform (HHT) is used in signal based processing for evaluating instantaneous frequency of the acoustic events. It is found that the appropriately processed and carefully analyzed acoustic data is capable of providing vital information on progression of damage on different types of concrete.

Key Words
acoustic emission; fracture energy; fracture process zone; fibre reinforced concrete; wave transformation; HHT

Address
Nawal Kishor Banjara, Saptarshi Sasmal and V. Srinivas: Special & Multifunctional Structures Laboratory (SMSL), CSIR-Structural Engineering Research Centre,
Taramani, Chennai-600113, India


Abstract
The probabilistic tsunami risk assessment of large coastal areas is challenging because the inland propagation of a tsunami wave requires an accurate numerical model that takes into account the interaction between the ground, the infrastructures, and the wave itself. Classic mesh-based methods face many challenges in the propagation of a tsunami wave inland due to their ever-moving boundary conditions. In alternative, mesh-less based methods can be used, but they require too much computational power in the far-field. This study proposes a hybrid approach. A mesh-based method propagates the tsunami wave from the far-field to the near-field, where the influence of the sea floor is negligible, and a mesh-less based method, smooth particle hydrodynamic, propagates the wave onto the coast and inland, and takes into account the wave structure interaction. Nowadays, this can be done because the advent of general purpose GPUs made mesh-less methods computationally affordable. The method is used to simulate the inland propagation of the 2004 Indian Ocean tsunami off the coast of Indonesia.

Key Words
smooth particle hydrodynamic; parallel computing; tsunami risk assessment; probabilistic approach; dynamic analysis

Address
Fritz Sihombinga and Marco Torbol: Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea

Abstract
An accurate non-model-based method for delamination identification of laminated composite plates is proposed in this work. A weighted mode shape damage index is formulated using squared weighted difference between a measured mode shape of a composite plate with delamination and one from a polynomial that fits the measured mode shape of the composite plate with a proper order. Weighted mode shape damage indices associated with at least two measured mode shapes of the same mode are synthesized to formulate a synthetic mode shape damage index to exclude some false positive identification results due to measurement noise and error. An auxiliary mode shape damage index is proposed to further assist delamination identification, by which some false negative identification results can be excluded and edges of a delamination area can be accurately and completely identified. Both numerical and experimental examples are presented to investigate effectiveness of the proposed method, and it is shown that edges of a delamination area in composite plates can be accurately and completely identified when measured mode shapes are contaminated by measurement noise and error. In the experimental example, identification results of a composite plate with delamination from the proposed method are validated by its C-scan image.

Key Words
laminated composite plate; delamination identification; non-model-based method; mode shape; polynomial fit

Address
Yongfeng Xu: Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221, USA
Da-Ming Chen and Weidong Zhu: Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
Guoyi Li and Aditi Chattopadhyay: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287, USA

Abstract
Achieving a pervious concrete (PC) with appropriate physical and mechanical properties used in pavement have been strongly investigated through the use of different materials specifically from the global waste materials of the populated areas. Discarded tires and the rubber tire particles have been currently manufactured as the recycled waste materials. In the current study, the combination of polymer, silica fume and rubber aggregates from rubber tire particles have been used to obtain an optimized PC resulting that the PC with silica fume, polymer and rubber aggregate replacement to mineral aggregate has greater compressive and flexural strength. The related flexural and compressive strength of the produced PC has been increased 31% and 18% compared to the mineral PC concrete, also, the impact resistance has been progressed 8% compared to the mineral aggregate PC and the permeability with Open Graded Fraction Course standard (OGFC). While the manufactured PC has significantly reduced the elasticity modulus of usual pervious concrete, the impact resistance has been remarkably improved.

Key Words
pervious concrete (PC); polymer; Silica fume (SF); rubber aggregate (RA); permeability; abrasion resistance; impact resistance

Address
Diyuan Li: 1School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Ali Toghroli: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
Mahdi Shariati: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Fathollah Sajedi: Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Dieu Tien Bui: Geographic Information Science Research Group, Ton Duc Thang University, Ho Chi Minh City, Viet Nam;
Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
Peiman Kianmehr: Department of Civil Engineering, American University in Dubai, Media City, Dubai, UAE
Edy Tonnizam Mohamad: Centre of Tropical Geoengineering (GEOTROPIK), Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia
Majid Khorami: Universidad UTE, Facultad de Arquitectura y Urbanismo, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador


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