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CONTENTS
Volume 6, Number 4, October 2021
 


Abstract
In this study, the progressive collapse behavior (full load and displacement control methods) of low-rise models representing 2-bay2storey and 3-bay3storey reinforced concrete framed structures located in high seismic zone, designed by Indian codes (IS 456:2000 and IS 1893-2016) for envelope loading combination are assessed with and without U.S. General Services Administration (GSA) guidelines. For displacement-controlled mechanism, a target displacement of 2%, 4% and 5% of the height of structure are considered. Non-linear static behavior of the structure is investigated through (a) Hinge formation pattern (b) Displacement of Joints adjacent to removed column along x-axis and z-axis (c) and Pushdown capacity curves. The results indicate that the Hinge formation patterns are similar for envelope loading combination and GSA loading combination, and the accuracy of the displacement-controlled method is much remarkable compared to full load method, therefore a standard formula is obligatory for calculating the target displacement to control progressive collapse, based on structural requirements unlike the dynamic increase factor calculations based on the structural capacity. With increase in each span and height of structure consecutively, pushdown capacity curves indicate that the base shear increases approximately by two times whereas the displacement in downward direction reduces by 59% and 62.4% for corner column removal and middle column removal cases respectively.

Key Words
displacement-controlled method; envelope loading combination; full load-controlled method; nonlinear static analysis; progressive collapse; U.S. General services administration (GSA) Guidelines

Address
Tariq Ahmad Sheikh:Department of Civil Engineering, National Institute of Technology, Srinagar, Jammu and Kashmir, India

J.M. Banday:Department of Civil Engineering, National Institute of Technology, Srinagar, Jammu and Kashmir, India

Mohammed A. Hussain:Department of Civil Engineering, I.S.L Engineering College, Bandlaguda, Chandrayangutta, Hyderabad, Telangana, India

Abstract
The seismic performances of suspended ceilings are mostly evaluated via shaking table tests, whose results can be intuitively understood. However, these tests become impracticable when the ceiling surface area is beyond the limit of the shake table. Hence, simulation analysis becomes an alternative method. However, simulation analysis for suspended ceilings has not been yet developed and is used as an auxiliary method. To provide a new approach for evaluating the seismic performances of suspended ceilings, we have proposed numerical models for a new seismic integrated ceiling in previous studies, including 1) models (shell elements) for the intersections of the ceiling members and 2) models (beam elements) for ceiling units. Based on our previous studies, we created a model with a ceiling surface area of 264 m2 and analyzed via LS-DYNA as an example to evaluate the seismic performance of the new seismic integrated ceiling. To confirm the seismic behavior of the new seismic integrated ceiling during earthquakes, as an example, JMA Kobe earthquake waves were input into the simulation model for the first time. Via the simulation analysis, it was confirmed that the seismic performance of the new seismic integrated ceiling was satisfactory even when the ceiling surface area exceeded 200 m2.

Key Words
integrated ceiling; numerical model; seismic ceiling; seismic evaluation; simulation analysis; suspended ceiling

Address
Zhilun Lyu:Okuju Corporation, 5-3-7 Nishitemma, Kita-Ku 530-0047, Osaka, Japan

Masakazu Sakaguchi:Asahibuilt Industry, Corporation Limited, 4-32-8, Kamatahommachi, Otaku 144-0052, Tokyo, Japan

Tomoharu Saruwatari:JSOL Corporation, 2-2-4 Tosabori, Nishi-Ku 550-0001, Osaka, Japan

Yasuyuki Nagano:Graduate School of Information Science, University of Hyogo, 7-1-28, Minatojima-minamimachi,
Chuo-Ku 650-0047, Kobe, Japan

Abstract
In the framework of nonlocal strain gradient theory, the dynamic responses of a porous functionally graded (FG) nano-size beam under half-sine impulse load and thermal environment. The half-sine impulse load has been modeled as a point load located on the top surface of the nano-size beam. The exerted impulse load leads to the transient vibrations of the nano-size beam at a prescribed time. The porous beam has been described with two pore distributions named even-type and uneven-type pores. The formulation has been developed based upon the refined beam model while the equations will be solved numerically using differential quadrature (DQ) method. Finally, the dynamic deflections in transient region will be derived with the usage of Laplace transform technique. It will be indicated that temperature variation, pore distribution and nano-scale factors have remarkable influences on dynamic resonse of the nano-size beam subjected to sine-type impulse loads.

Key Words
integrated ceiling; seismic ceiling; ceiling modules; FEM analysis

Address
Mouayed H.Z. Al-Toki:Middle Technical University, Technical College, Baghdad, Iraq

Raad M. Fenjan:Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Ridha A. Ahmed:Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Nadhim M. Faleh:Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Wael Najm Abdullah:Al-Mustansiriah University, Engineering Collage P.O. Box 46049, Bab-Muadum, Baghdad 10001, Iraq

Abstract
This experimental study was conducted to determine nut factors based on four combinations of washers and nuts. A prestressing force was applied to a long reinforcing bar using the torque–tension method. All the sets exhibited a linear trend. The nut factors for combinations of the flat washers and hex nuts, spring washers and hex nuts, flat washers and heat-treated nuts, and flat washers and self-locking nuts were 0.228, 0.224, 0.299, and 0.397, respectively. Additionally, the relaxation of the flat washers and hex nuts in a relatively long-term period (40 days in this study) was evaluated, and eight specimens subjected to various initial prestressing forces were analyzed. The average change in prestressing force was -3.98%. It is necessary to consider prestressing force loss for relatively long-term when prestressing force is applied to a long reinforcing bar.

Key Words
nut factor, prestressing force, relatively long-term relaxation; torque–tension, washer and nut

Address
Seung-Hyeon Hwang:Department of Architectural Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Youngtong-gu, Suwon, Kyonggi-Do, 16227, Republic of Korea

Sanghee Kim:Department of Architectural Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Youngtong-gu, Suwon, Kyonggi-Do, 16227, Republic of Korea

Keun-Hyeok Yang:Department of Architectural Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Youngtong-gu, Suwon, Kyonggi-Do, 16227, Republic of Korea

Abstract
In earthquake engineering, vibration control is a set of engineering tools aimed at mitigating seismic effects on structural members. Once the seismic waves have penetrated a building, there are a number of ways to control them to mitigate their damaging effects and improve the seismic performance of the building. Dissipate the wave energy inside the structure with properly designed dampers, distributing the wave energy over a wider frequency range and absorbing the resonant portions of the entire wave frequency band using what are known as mass dampers. The effect of mass attenuator on the reduction of fundamental frequency of beams made of functionally graded material (FGM) with annular and rectangular cross sections is studied. Mori-Tanaka homogenization scheme, conventional mixing rule and power law functions are used to model the material gradation. Various classical boundary conditions as well as shear hinge natural condition are considered. The lumped mass attenuator is connected to the beam at an arbitrary position without sliding. The total potential energy is minimized by using the spectral Ritz method to calculate the fundamental frequency and the corresponding mode shape. A reduction in the frequencies is observed in the presence of the attached lumped mass attenuator. The dimensionless frequency reduction is affected by the amount and position of the lumped mass. The position of the lumped mass attenuator plays an important role in vibration control of the beam.

Key Words
classical beam theory; lumped mass damper; material gradation; spectral ritz method; vibration analysis

Address
Abbas Heydari:Department of Civil Engineering, Technical and Vocational University (TVU), Tehran, Iran

Abstract
In Korea, a 15.2-mm diameter strand is preferred for a post-tensioning (PT) method to reduce the total tendon and anchor number. However, the anchor for the Ø15.2-mm strand is large and sometimes inefficient while the anchor using the Ø12.7 mm single-strand is common in the United States. This study developed a post-tensioned anchor for Ø15.2-mm unbonded single-strand tendons to address the existing trend in domestic PT construction. The shape of the anchor is optimized to minimize the von Mises stress through a finite element analysis by varying the shape of the tubular body, bearing plate, and gussets. In addition, the design is also determined in consideration of a jacking device, accessories, and workability. ACI 423.7-14, on the other hand, requires the use of an encapsulation system, which is highly resistant to corrosion, for elevated floors. Therefore, the encapsulated anchor was also developed to enhance the durability of PT tendons and buildings.

Key Words
anchor; design optimization; encapsulation; finite element analysis; post-tensioning

Address
Ah Sir Cho:Department of Architecture, Dongyang Mirae University, 445 Gyoungin-ro, Guro-gu, Seoul,Republic of Korea

Thomas H.-K. Kang:Department of Architecture & Architectural Engineering and Engineering Research Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea


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