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CONTENTS
Volume 83, Number 6, September25 2022
 


Abstract
Fastening systems have a significant role in the response of railway slab track systems. Although experimental tests indicate nonlinear behavior of fastening systems, they have been simulated as a linear spring-dashpot element in the available literature. In this paper, the influence of the nonlinear behavior of fastening systems on the slab track response was investigated. In this regard, a nonlinear model of vehicle/slab track interaction, including two commonly used fastening systems (i.e., RFFS and RWFS), was developed. The time history of excitation frequency of the fastening system was derived using the short time Fourier transform. The model was validated, using the results of a comprehensive field test carried out in this study. The frequency response of the track was studied to evaluate the effect of excitation frequency on the railway track response. The results obtained from the model were compared with those of the conventional linear model of vehicle/slab track interaction. The effects of vehicle speed, axle load, pad stiffness, fastening preload on the difference between the outputs obtained from the linear and nonlinear models were investigated through a parametric study. It was shown that the difference between the results obtained from linear and nonlinear models is up to 38 and 18 percent for RWFS and RFFS, respectively. Based on the outcomes obtained, a nonlinear to linear correction factor as a function of vehicle speed, vehicle axle load, pad stiffness and preload was derived. It was shown that consideration of the correction factor compensates the errors caused by the assumption of linear behavior for the fastening systems in the currently used vehicle track interaction models.

Key Words
fastening system, nonlinear behavior, rail foot, rail web, railway slab track

Address
Javad Sadeghi, Mohammad Seyedkazemi: School of Railway Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
Amin Khajehdezfuly: Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Ahvaz, Iran

Abstract
In this paper, an analytical formulation is proposed to predict the vertical vibration response due to the pedestrian walking on a footbridge considering the human-structure interaction, where the footbridge and pedestrian are represented by the Euler beam and linear oscillator model, respectively. The derived coupled equation of motion is a nonlinear fourth-order partial differential equation. An uncoupled solution strategy based on the combined weighted residual and perturbation method) is proposed to reduce the tedious computation, which allows the separate integration between the bridge and pedestrian subsystems. The theoretical study demonstrates that the pedestrian subsystem can be treated as a structural system with added mass, damping, and stiffness. The analysis procedure is then applied to a case study under the conditions of single pedestrian and multi pedestrians, and the results are validated and compared numerically. For convenient vibration design of a footbridge, the simplified peak acceleration formula and the idea of decoupling problem are thus proposed.

Key Words
footbridge, human-structure interaction, perturbation method, vibration serviceability

Address
Liang Cao, Hailei Zhou: 1College of Civil Engineering, Hunan University, Changsha 410082, China; Key Laboratory for Damage Diagnosis of Engineering Structures of Hunan Province, Hunan University, Changsha 410082, China
Y. Frank Chen: Department of Civil Engineering, The Pennsylvania State University, Middletown, PA, USA

Abstract
This study aims to determine the cause of the load resistance loss in storage racks that can be attributed to external forces such as earthquakes and to improve safety by developing reinforcement systems that can prevent load resistance loss. To this end, a static cyclic loading test was performed on pallet racks commonly used in logistics warehouses. The test results indicated that a pallet rack exposed to an external force loses more than 50% of its load resistance owing to the damage caused to column-beam joints. Three reinforcement systems were developed for preventing load resistance loss in storage racks exposed to an external force and for performing differentiated target functions: column reinforcement device, seismic damper, and viscoelastic damper. Shake table testing was performed to evaluate the earthquake response and verify the performance of these reinforcement systems. The results confirmed that, the maximum displacement, which causes the loss of load resistance and the permanent deformation of racks under external force, is reduced using the developed reinforcement devices. Thus, the appropriate selection of the developed reinforcement devices by users can help secure the safety of the storage racks.

Key Words
fragile member reinforcement system; seismic performance; shake table testing; storage racks

Address
Gwanghee Heo: Department of International & Plant Engineering, Konyang University, 121 Daehak-ro, Chungcheongnam-do 32992, Korea
Chunggil Kim: Public Safety Research Center, Konyang University, 121 Daehak-ro, Chungcheongnam-do 32992, Korea
Eunrim Baek: Seismic Research and Test Center, Pusan National University, 49 Busandaehak-ro, Mulgeum-eup, Yangsan-si, Korea
Seunggon Jeon: Department of Construction Safety & Disaster Prevention, Chungnam State University, 55, Haksa-gil, Cheongyang-gun,Chungcheongnam-do 33303, Korea

Abstract
In this paper, the vibration of a moderately thick plate to a moving mass is investigated. Pasternak foundation with a variable subgrade modulus is considered to tackle the shortcomings of Winkler model, and an analytical-numerical solution is proposed based on the eigenfunction expansion method. Parametric studies by using both CPT (Classical Plate Theory) and FSDT (First-Order Shear Deformation Plate Theory) are carried out, and, the differences between them are also highlighted. The obtained results reveal that utilizing FSDT without considering the rotary inertia leads to a smaller deflection in comparison with CPT pertaining to a thin plate, while it demonstrates a greater response for plates of higher thicknesses. Moreover, it is shown that CPT is unable to properly capture the variation of the plate thickness, thereby diminishing the accuracy as the thickness increases. The outcomes also indicate that the presence of a foundation contributes more to the dynamic response of thin plates in comparison to moderately thick plates. Furthermore, the findings suggest that the performance of the moving force approach for a moderately thick plate, in contrast to a thin plate, appears to be acceptable and it even provides a much better estimation in the presence of a foundation.

Key Words
circular plate, classical plate theory, Mindlin plate theory, moving mass, Pasternak foundation, shear deformation, Winkler foundation

Address
Mohsen Rezvani Alile, Mohammad Ali Foyouzat and Massood Mofid: Department of Civil Engineering, Sharif University of Technology, Tehran, Iran

Abstract
This research investigates the free vibration of porous advanced composite plates resting on Winkler/Pasternak/ Kerr foundations by using a new hyperbolic quasi three dimensional (quasi-3D) shear deformation theory. The present theory, which does not require shear correction factor, accounts for shear deformation and thickness stretching effects by parabolic variation of all displacements across the thickness, and satisfies the stress-free boundary conditions on the upper and lower surfaces of the plate. In this work, we consider imperfect FG plates with porosities embedded within elastic Winkler, Pasternak or Kerr foundations. Implementing an analytical approach, the obtained governing equations from Hamilton's principle according to FG plates are derived. The closed form solutions are obtained by using Navier technique, and natural frequencies of FG plates are found, for simply supported plates, by solving the results of eigenvalue problems. A comprehensive parametric study is presented to evaluate effects of the geometry of material, mode numbers, porosity volume fraction, Power-law index and stiffness of foundations parameters on free vibration characteristics of FG plates.

Key Words
elastic foundations, free vibration, functionally graded plates, porosity, quasi-3D HSDT

Address
Mohamed Rabhi: Department of Civil Engineering and Hydraulics, Faculty of Technology, University of Saida Dr Moulay Tahar, PO Box 138, City En-Nasr 20000 Saida, Algeria
Kouider Halim Benrahou: Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria; Department of Civil Engineering and Public Works, Faculty of Technology, University of Sidi Bel Abbes, Algeria
Redha Yeghnem: Department of Civil Engineering and Hydraulics, Faculty of Technology, University of Saida Dr Moulay Tahar, PO Box 138, City En-Nasr 20000 Saida, Algeria;
Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria
Hicham Zakaria Guerroudj: Department of Civil Engineering and Hydraulics, Faculty of Technology, University of Saida Dr Moulay Tahar, PO Box 138, City En-Nasr 20000 Saida, Algeria
Abdelhakim Kaci: Department of Civil Engineering and Hydraulics, Faculty of Technology, University of Saida Dr Moulay Tahar, PO Box 138, City En-Nasr 20000 Saida, Algeria;
Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria; Department of Civil Engineering and Public Works, Faculty of Technology, University of Sidi Bel Abbes , Algeria; YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Abstract
The stud shear connector is the main force transfer member in the steel-concrete composite member, and the mechanical behavior is very complicated in the concrete. The concrete around the stud is subjected to the pry-out local pressure concentration of the stud, which can easily produce splitting mirco-cracks. In order to solve the problem of pry-out local splitting of stud shear connector, a kind of stud shear connector with constraint measure is proposed in this paper. Through the push-out test, the interface shear behavior of the new stud shear connector between steel and concrete flange plate was studied, and the difference between the new stud shear connector and the traditional stud connector was compared. The results show that the stud shear connector with constraint measure can effectively avoid the adverse effect of local pressure splitting by relying on its own constraint measure. The shear stiffness of the interface between steel and concrete flange plates is greatly improved, which provides a theoretical basis for the design of strong connection coefficient of steel-concrete composite structures.

Key Words
stud shear connector; constraint measure; slip; shear stiffness; transverse reinforcement

Address
Jingjing Qi, Zuwei Xie, Zhi Huang, Weirong Lv, Weihua Shi: School of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
Hua Cao: Hunan Architectural Design Institute Limited Company, Changsha 410012, China

Abstract
This study investigated the effect of the strengthening efficiency of unbonded steel-bar truss system on the out-ofplane behavior of perforated masonry walls. Four full-scale unreinforced masonry (URM) walls with two different planes were prepared using the unbonded steel-bar truss system and a URM walls without strengthening. All masonry walls were tested under constant axial and cyclic lateral loads. The obtained test results indicated that the pinching effect in the out-plane behavior of masonry walls tends to decrease in the in- and out-of-plane strengthened URM walls using the unbonded steel-bar truss system with the higher prestressing force ratio (Rp) of vertical reinforcing bars in the unbonded steel-bar truss system, regardless of the perforated type of the masonry wall. Consequently, the highest maximum shear resistance and cumulative dissipated energy at peak load in the post-peak behavior were observed in the in- and out-plane strengthened URM walls with the highest Rp values, which are 2.7 and 6.0 times higher than those of URM. In particular, the strengthening efficiency of the unbonded steel-bar truss system was primarily attributed to the vertical prestressed steel-bars rather than the diagonal steel-bars, which indicates that the strains in the vertical prestressed steel-bars at the peak load were approximately 1.6 times higher than those in the diagonal steel-bars.

Key Words
out-of-plane behavior, perforated masonry wall, shear capacity, strengthening, unbonded steel-bar truss unit

Address
Seung-Hyeon Hwang: Department of Architectural Engineering, Graduate School, Kyonggi University, 154-42 Gwanggyosan-ro, Youngtong-gu, Suwon, Kyonggi-do, Korea
Ju-Hyun Mun, Keun-Hyeok Yang, Sanghee Kim: Department of Architectural Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Youngtong-gu, Suwon, Kyonggi-do, Korea

Abstract
Despite its disadvantages, soft story can reduce the damage to the upper floors by concentrating drift in that specific story provided that large drifts are avoided. Gapped-Inclined Brace (GIB) with reduced P-delta effects and the control of soft story stiffness makes it possible to take advantage of the soft story in buildings and increase their capacity for energy dissipation. OpenSees software is used in this study to validate and modify the GIB model's shortcomings. Also, the analysis method for this element is changed for design. The modified element is evaluated in 3D analysis. Finally, to retrofit an existing building, this element is used. Based on the Iranian seismic code, a six-story reinforced concrete building is modelled and studied with 3D analysis. In this building, the construction shortcomings and elimination of infills on the ground floor cause the formation of a soft story. Results of nonlinear static analysis, nonlinear dynamic, and incremental dynamic analysis using both components of seismic acceleration applied to the structure at different angles and the fragility curves indicate the improvement of the retrofitted structure's performance using the modified element to reach the required performance level following the retrofit code.

Key Words
3D nonlinear analysis, infills, modified gapped-inclined brace, retrofit, soft story

Address
Soroush Nodehi: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran
Seyed Mehdi Zahrai: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran; Department of Civil Engineering, University of Ottawa, Ottawa, Canada

Abstract
The effectiveness and accuracy of the strain-based approach applied for analysis of two kinds of heterogeneous hollow cylinders subjected to thermal and mechanical loads are examined in this study. One is a multilayer cylinder in which the material in each layer is assumed to be linearly elastic, homogeneous and isotropic. Another is a hollow cylinder made of functionally graded materials with arbitrary gradient. The steady state condition without heat generation is considered. A sector in-plane finite element in the polar coordinate system based on strain approach is used. This element has only three degrees of freedom at each corner node. Analytical solutions available in the literature are presented to illustrate the accuracy of the sector element used. The obtained results for displacements and stresses are shown to be in good agreement with the analytical solutions.

Key Words
functionally graded materials; heterogeneous; multilayer cylinder; sector in-plane finite element; strain-based approach

Address
Asma Bouzeriba: Department of Science and Technology, Faculty of Science and Technology, Mechanical Engineering Materials and Structures Laboratory, Tissemsilt University, Algeria
Cherif Bouzrira: Department of Civil Engineering, Faculty of Science and Technology, Mohammed Seddik Ben Yahia University, Jijel, Algeria

Abstract
This paper analyzes the variation law of the pipe lateral vibration characteristics, it was treated as a beam model, and was dispersed into several subunits based on the FEM. The corresponding stiffness and mass matrix of the pipe was deduced by using Hermite interpolation function, and the overall dynamic balance equation was established. The lateral vibration under different pipe lengths, thicknesses and towing speeds are solved by integral method. The results show that the pipe vibration trend decreases first and then increases, and the vibration value at the ore bin is larger than that at the pump set, and the value at the top is the largest, and the least value location can change with the length increase. Increasing length and thickness can reduce lateral vibration value, while increasing speed can increase the value. Neither the thickness nor the towing speed will change the location where the least value occurs. The vibration intensity will increase with the decrease of pipe length and thickness and the increase of towing speed.

Key Words
deep-sea mining, FEM, integral method, lateral vibration, stepped mining pipe

Address
Linjing Xiao and Qiang Liu: College of Mechanical & Electronic Engineering, Shandong University of Science and Technology, Qingdao 266590, China


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