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CONTENTS
Volume 23, Number 4, October 2022
 


Abstract
This work addresses the optimization controller design problem combining the AI evolution bat (EB) optimization algorithm with a fuzzy controller in the practical application of a reinforced concrete frame structure. This article explores the use of an intelligent EB strategy to reduce the dynamic response of Lead Rubber Bearing (LRB) composite reinforced concrete frame structures. Recently developed control units for plant structures, such as hybrid systems and semi-active systems, have inherently non-linear properties. Therefore, it is necessary to develop non-linear control methods. Based on the relaxation method, the nonlinear structural system can be stabilized by properly adjusting the parameters. Therefore, the behavior of a closed-loop system can be accurately predicted by determining the behavior of a closed-loop system. The performance and durability of the proposed control method are demonstrated by numerical simulations. The simulation results show that the proposed method is a viable and feasible control strategy for seismically tuned composite reinforced concrete frame structures.

Key Words
fuzzy dynamics; lead rubber bearing; nonlinear algorithmic systems; reinforces concrete frame; smart control and analysis

Address
Z.Y. Chen, Yahui Meng, Ruei-yuan Wang: School of Science, Guangdong University of Petrochemical Technology, Maoming 525000, Guangdong, China
Timothy Chen: California Institute of Technology, Pasadena, CA 91125, USA

Abstract
Due to the large volume and generally as a public building, the damage of large-span space structures under various non-conventional loads will cause greater economic losses, casualties, and social impacts, etc. Therefore, it is particularly important to evaluate the seismic performance of large-span space structures. This paper taked a multipurpose sports center as an example and considered its synergistic deformation based on the method of equivalent damping ratio. Furthermore, The ABAQUS software was used to analyze the time-history and energy response of the multipurpose sports center under the action of rare earthquakes, and proposed a quantitative damage index to assess the overall damage of the structure. Finally, the research results indicated that the maximum inter-story drift ratio of the multipurpose sports center under the action of rare earthquakes was less than its limit value. The frame beams presented different degrees of damage, but the key members were basically in an elastic state. The bearing capacity did not reach the limit value, which satisfied the intended seismic performance target. This study taked an actual case as an example and proposed a relevant damage evaluation system, which provided some reference for the analysis of the seismic performance of large-span space structures.

Key Words
damage index; energy response; equivalent damping ratio; large-span space structures; seismic performance

Address
Jun Wei, Lexiang Zhou, Fei Chen: Department of Civil Engineering, Qinghai University, Xining 810016, China
Qingshun Yang: Department of Civil Engineering, Qinghai University, Xining 810016, China; Key Laboratory of Building Energy-saving Materials and Engineering Safety in Qinghai Province, Qinghai University, Xining810016, China

Abstract
The dynamic behavior of a single pile was investigated by using analytical and numerical studies. The focus of this study was to develop the dynamic p-y curve of a pile for pseudo-static analysis considering the shear wave velocity of the soil by using three-dimensional numerical analyses. Numerical analyses were conducted for a single pile in dry sand under changing conditions such as the shear wave velocity of the soil and the acceleration amplitudes. The proposed dynamic p-y curve is a shape of hyperbolic function that was developed to take into account the influence of the shear wave velocity of soil. The applicability of pseudo-static analysis using the proposed dynamic p-y curve shows good agreement with the general trends observed by dynamic analysis. Therefore, the proposed dynamic p-y curve represents practical improvements for the seismic design of piles.

Key Words
dynamic horizontal subgrade reaction modulus; dynamic p-y curve; pseudo-static analysis; shear wave velocity

Address
Sumin Song, Sangseom Jeong: Department of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic Korea
Hyunsung Lim, Seongyong Park: Hanwha Engineering and Construction, Seoul 04541, Republic of Korea

Abstract
Traditional metal dampers have disadvantages such as a higher yield point and inadequate adjustability. The experimental results show that the low yield point steel has superior energy dissipation hysteretic capacity and can be applied to seismic structures. To overcome these deficiencies, a novel compound metal damper comprising both low yield point steel plates and common steel plates is presented. The optimization objectives, including "maximum rigidity" and "full stress state", are proposed to obtain the optimal edge shape of a compound metal damper. The numerical results show that the optimized composite metal damper has the advantages such as full hysteresis curve, uniform stress distribution, more sufficient energy consumption, and it can adjust the yield strength of the damper according to the engineering requirements. In view of the mechanical characteristics of the compound metal damper, the equivalent model of eccentric cross bracing is established, and the approximate analytical solution of the yield strength and the yield displacement is proposed. A nonlinear simulation analysis is carried out for the overall aseismic capacity of three-layer-frame structures with a compound metal damper. It is verified that a compound metal damper has better energy dissipation capacity and superior seismic performance, especially for a damper with double-objective optimized shape.

Key Words
full stress; low yield point steel; metal damper; seismic control; topology optimization

Address
Haoxiang He, Jiawei Ding, Lei Huang: Beijing Key Lab of Earthquake Engineering and Structural Retrofit, Beijing University of Technology, Beijing, 100124, China

Abstract
To improve the seismic performance of suspended ceiling structures, various vibration-damping devices have been developed. However, the devices made of metals have a limit in that they cause large deformation and seriously damages the exterior of the suspended ceiling structure from the wall. As a results, their strengthening effect of the suspended ceiling structure was minimal. Thus, this study employed a spring and vibration-proof rubber effectively controlled vibrations without increasing horizontal seismic loads on the ceiling to enhance the seismic resistance of suspended ceiling structures. The objective of the study is to examine the dynamic properties of a seismic damping-isolation unit (SDI) with various details developed. The developed SDI was composed of a spring, embossed rubbers, and prestressed bolts, which were the main factors enhancing the damping effect. The shaking table tests were performed on eight SDI specimens produced with the number of layers of embossed rubber (ns), presence or absence of a spring, prestressed force magnitude introduced in bolts (fps), and mass weight (Wm) as the main parameters. To identify the enhancement effect of the SDI, the dynamic properties of the control specimen with a conventional hanger bolt were compared to those of the SDI specimens. The SDI specimens were effective in reducing the maximum acceleration (Ac max), acceleration amplification factor (ap), relative displacement (oR), and increasing the damping ratio (f) when compared to the control specimen. The Ac max, ap and fR of the SDI specimens with two rubbers, spring, and fps of 0.1fby, where fby is the yielding strength of the screw bolt were 57.8%, 58.0%, and 61.9% lower than those of the conventional hanger bolt specimens, respectively, resulting in the highest f(=0.127). In addition, the 𝛼𝑝 of the SDI specimens was 50.8% lower than those specified in ASCE 7 and FEMA 356. Consequently, to accurately estimate the 𝛼𝑝 of the SDI specimens, a simple model was proposed based on the functions of fps stiffness constant of the spring (K), Wm, and ns.

Key Words
dampers; earthquake/seismic isolation; earthquake/seismic performance; free vibration/frequencies; structural dynamics

Address
Keun-Hyeok Yang, Ju-Hyun Mun: Department of Architecture Engineering, Kyonggi University, Gyeonggi-do 16227, Republic of Korea
Chae-Rim Im, Eun-Bee Won: Department of Architectural Engineering, Kyonggi University, Graduate School, Gyeonggi-do 16227, Republic of Korea

Abstract
Uncertainty quantification is the most important challenge in seismic fragility assessment of structures. The precision increment of the quantification method leads to reliable results but at the same time increases the computational costs and the latter will be so undesirable in cases such as reliability-based design optimization which includes numerous probabilistic seismic analyses. Accordingly, the authors' effort has been put on the development and validation of an approach that has reduced computational cost in seismic fragility assessment. In this regard, it is necessary to apply the appropriate methods for consideration of two categories of uncertainties consisting of uncertainties related to the ground motions and structural characteristics, separately. Also, cable-stayed bridges have been specifically selected because as a result of their complexity and the according time-consuming seismic analyses, reducing the computations corresponding to their fragility analyses is worthy of studying. To achieve this, the fragility assessment of three case studies is performed based on existing and proposed approaches, and a comparative study on the efficiency in the estimation of seismic responses. For this purpose, statistical validation is conducted on the seismic demand and fragility resulting from the mentioned approaches, and through a comprehensive interpretation, sufficient arguments for the acceptable errors of the proposed approach are presented. Finally, this study concludes that the combination of the Capacity Spectrum Method (CSM) and Uniform Design Sampling (UDS) in advanced proposed forms can provide adequate accuracy in seismic fragility estimation at a significantly reduced computational cost.

Key Words
cable-stayed bridge; sampling methods; seismic analysis methods; seismic fragility assessment; uncertainty quantification

Address
Vahid Akhoondzade-Noghabi, Khosrow Bargi: School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran


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