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CONTENTS
Volume 6, Number 2, June 2019
 

Abstract
The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles\'relative scour depth on the bridge natural frequency of the first four vibration modes.

Key Words
bridge; natural frequency; modal analysis; scour depth

Address
Reza Akbari: Office of Road Maintenance, Road Maintenance and Transportation Organization, Tehran, Iran
Saeed Maadani: Department of Engineering, Takestan Branch, Islamic Azad University, Takestan, Iran
Alireza Abedi: Department of Engineering, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran
Shahrokh Maalek: School of Civil Engineering, University of Tehran, Tehran, Iran

Abstract
Present study concerns the safety evaluation of SefidRud dam\'s block No. 18 regarding probable crack propagation in the foundation gallery under a MCE record. Accordingly, a 3D finite element model of the block in companion with the reservoir and the foundation is modeled. All the associated thermal and structural parameters are derived via calibration with the records of thermometers and pendulums installed inside the dam body. The origination of the cracks and their whereabouts are determined by primary thermal and static analyses and through a linear dynamic analysis the potential failure zone and their extent and level are studied. The foundation gallery is the most probable zone among the other intensive tensile stress area to compromise the dam stability. Therefore, the nonlinear analysis of this risky region is inevitable. The results depict the permissible expansion of the cracks inside the gallery even under another future earthquake in MCE level. As a consequence, the general dam performance is assessed safe in spite of the seepage flow rate growth from the gallery fractures.

Key Words
Buttress dam; calibration; cracked Initial condition; post earthquake stability; SefidRud dam

Address
Hasan Mirzabozorg and Amirhossein Roohezamin: Department of Civil Engineering, K. N. Toosi University of Technology, Valiasr Avenue, Tehran, Iran
Mohsen Ghaemian:Department of Civil Engineering, Sharif University of Technology; Azadi Avenue,
P.O. Box 11365-9313, Tehran, Iran


Abstract
Bridge scour is one of the predominant causes of bridge failure. Current climate deterioration leads to increase of flooding frequency and severity and thus poses a higher risk of bridge scour failure than before. Recent studies have explored extensively the vibration-based scour monitoring technique by analyzing the structural modal properties before and after damage. However, the state-of-art of this area lacks a systematic approach with sufficient robustness and credibility for practical decision making. This paper attempts to develop a data-driven methodology for bridge scour monitoring using support vector machines. This study extracts features from the bridge dynamic responses based on a generic sensitivity study on the bridge\'s modal properties and selects the features that are significantly contributive to bridge scour detection. Results indicate that the proposed data-driven method can quantify the bridge scour damage with satisfactory accuracy for most cases. This paper provides an alternative methodology for bridge scour evaluation using the machine learning method. It has the potential to be practically applied for bridge safety assessment in case that scour happens.

Key Words
bridge scour; modal properties; machine learning; feature extraction; feature selection; support vector machines

Address
Zhiming Zhang and Chao Sun: Department of Civil and Environmental Engineering, Louisiana State University,
3255 Patrick F. Taylor Hall, Baton Rouge, LA 70803, United States
Changbin Li: Department of Computer Science, University of Texas at Dallas, 800 W Campbell Rd, Richardson, TX 75080, United States
Mingxuan Sun: Division of Computer Science and Engineering, Louisiana State University,
3325 Patrick F. Taylor Hall, Baton Rouge, LA 70803, United States




Abstract
In present article, a size-dependent refined thick beam element has been established based upon nonlocal elasticity theory. Next, it is used to explore vibration response of porous metal foam nanobeams on elastic medium. The established beam element introduces ten degrees of freedom. Different porosity distributions called uniform, symmetric and asymmetric will be employed. Herein, introduced thick beam element contains shear deformations without using correction factors. Convergence and verification studies of obtained results from finite element method are also provided. The impacts of nonlocality factor, foundation factors, shear deformation, slenderness ratio, porosity kinds and porosity factor on vibration frequencies of metal foam nano-sized beams have been explored.

Key Words
free vibration; refined beam theory; porous nanobeam; nonlocal elasticity; porosities

Address
Ammar F.H. Al-Maliki, Nadhim M. Faleh and Abbas A. Alasadi: Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Abstract
There have been a few checking frameworks intended to ensure and improve the nature of their regular habitat. The greater part of these frameworks are constrained in their capacities. In this paper, the insightful checking framework intended for debacle help and administrations has been exhibited. The ideal administrations, necessities and coming about plan proposition have been indicated. This has prompted a framework that depends fundamentally on ecological examination so as to offer consideration and security administrations to give the self-governance of indigenous habitats. In this sense, ecological acknowledgment is considered, where, in light of past work, novel commitments have been made to help include based and PC vision situations. This epic PC vision procedure utilized as notice framework for avalanche identification depends on changes in the normal landscape. The multi-criteria basic leadership strategy is used to incorporate slope data and the level of variety of the highlights. The reproduction consequences of highlight point discovery are shown in highlight guide coordinating toward discover steady and coordinating component focuses and effectively identified utilizing these two systems, by examining the variety in the distinguished highlights and the element coordinating.

Key Words
landslide; natural disaster; feature based; computer vision; natural disasters detection; event warning system

Address
Tim Chen: Faculty of Information Technology, Ton Duc Thang University, Ho Chi Minh City, Vietnam
C.F. Kuo: Faculty of Science, Monash University, Melbourne, 3122 Victoria, Australia
J.C.Y. Chen: Engineering and Decision Centre, Covenant University, 10 Idiroko Road, Canaan Land, Ota, Ogun State, Nigeria



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