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CONTENTS
Volume 20, Number 6, June 2021
 


Abstract
In order to reduce drifts in steel buildings located in high seismicity areas, structural engineers use deep columns despite what reported in some studies in the sense that deep columns can prematurely twist. In other studies, on the other hand, the use of deep columns is encouraged. The behavior of steel buildings with deep columns subjected to cyclic loading has been experimentally studied, but the effect of dynamic characteristics of strong motions and buildings, as well as the associated ductility demands, have not been considered. In this research, the seismic responses of steel buildings with medium columns are calculated in terms of drifts and ductility demands and compared to those of similar buildings with equivalent (same weight) deep columns. Results indicate that the drifts of the models with medium columns may be up to 60% larger than those of the models with deep columns implying that the drifts may significantly be reduced if deep columns are used. The reduction in terms of local ductility demands on beams may be up to 70%, but for the case of columns of high-rise buildings, the reduction is negligible. The reductions in story ductility demands are smaller than those of local ductility, as expected. Although it is generally accepted that nonlinear time history analysis is the most accurate and reliable analysis procedure, pushover analysis is broadly used to estimate seismic responses in terms of different parameters; however, the story ductility demands obtained from pushover while using deep columns are much larger than those of dynamic analysis.

Key Words
low-, mid- and high-rise steel buildings; drift and ductility demands; moment resisting frames; deep columns; nonlinear seismic analysis

Address
Alfredo Reyes-Salazar:Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Ciudad Universitaria, Culiacán, Sinaloa, México

Abstract
Earthquake Resistant Design Philosophy seeks (a) no damage, (b) no significant structural damage, and (c) significant structural damage but no collapse of normal buildings, under minor, moderate and severe levels of earthquake shaking, respectively. A procedure is proposed for seismic design of low-rise reinforced concrete special moment frame buildings, which is consistent with this philosophy; buildings are designed to be ductile through appropriate sizing and reinforcement detailing, such that they resist severe level of earthquake shaking without collapse. Nonlinear analyses of study buildings are used to determine quantitatively (a) ranges of design parameters required to assure the required deformability in normal buildings to resist the severe level of earthquake shaking, (b) four specific limit states that represent the start of different structural damage states, and (c) levels of minor and moderate earthquake shakings stated in the philosophy along with an extreme level of earthquake shaking associated with the structural damage state of no collapse. The four limits of structural damage states and the three levels of earthquake shaking identified are shown to be consistent with the performance-based design guidelines available in literature. Finally, nonlinear analyses results are used to confirm the efficacy of the proposed procedure.

Key Words
deformation demand; earthquake resistant design philosophy; limit states; structural damage states; levels of earthquake shaking

Address
Sunitha Palissery:Earthquake Engineering Research Centre, International Institute of Information Technology Hyderabad,
Gachibowli 500032, Telangana, India

Rupen Goswami:Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India

C.V.R. Murty:Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India

Abstract
On 25 April - 12 May 2015, a series of large earthquakes struck the north-central part of Nepal, causing not only a substantial number of casualties, but also heavy damage to the building structures and infrastructure facilities. Up to now, most of seismic reconnaissance studies about this event have attributed the structural damage and life losses to the relatively loose implementation of the building design codes in Nepal, as most of those damaged structures were largely owner-built. Based on the quite limited ground motion data, this paper investigated the primary characteristics of the Nepal earthquake sequence. It is highlighted that the pulse-like features are significant at both the soft and rock sites, which is also responsible for the unique characteristics of the main-shock ground motions other than site effects.

Key Words
Nepal earthquake; main-shock ground motions; pulse-like; aftershock ground motions

Address
Yi Pan:School of Civil Engineering, Southwest Jiaotong University, Chengdu, China/ Key Laboratory of High-speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu, China

Zhiwang Chang:School of Civil Engineering, Southwest Jiaotong University, Chengdu, China/ Key Laboratory of High-speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu, China

Cuihua Li:College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou, China

Shengjie Shi:Chongqing Construction Science Research Institute, Chongqing, China

Abstract
In this study, the seismic performance of a self-centering post-tensioned precast concrete (PC) frame with an enlarged beam end is evaluated for retrofit of a soft first story structure. A finite element model of a post-tensioned beam-column assembly with an enlarged beam end is validated by comparison with experimental results, and is used to validate an analytical model of the proposed system. Then the analytical model is used to retrofit a soft first story structure with only columns in the first story and infill walls above. A multi-objective optimization of the retrofit system is carried out using genetic algorithm. The seismic performance of the retrofitted structure is assessed by incremental dynamic analysis and fragility analysis. The analysis results show that the retrofit system calibrated by the optimization procedure is effective in increasing the seismic performance of the soft first story structure.

Key Words
seismic retrofit; soft first-story structures; multi objective optimization; genetic optimization; post-tensioned precast concrete frame

Address
Jonathan Assefa Dereje:Department of Civil Engineering and Architectural Engineering, Sungkyunkwan University, Suwon, Republic of Korea

Mohamed Nour Eldin:Department of Civil Engineering and Architectural Engineering, Sungkyunkwan University, Suwon, Republic of Korea

Jinkoo Kim:Department of Civil Engineering and Architectural Engineering, Sungkyunkwan University, Suwon, Republic of Korea

Abstract
Vulnerability analysis is a crucial method to study the seismic performance of tunnels. Two benchmark cross-sections of tunnels, namely circular and rectangular cross-sections, are selected as the research object to investigate the transverse seismic property of tunnels. A finite element model is established by SAP2000 software, and the influences of various site types, depths of burial of the tunnel, and cross-section sizes on the transverse seismic capacity of a tunnel are discussed. The probabilistic seismic demand model of ground motion intensity measures and the engineering demand parameters are determined by utilizing a modified incremental dynamic analysis (IDA) method, and the reasonable ground motion intensity measures are specified by analyzing four evaluation criteria. The failure probability of the structure under each earthquake intensity and the seismic vulnerability curve of the construction are calculated to evaluate the transverse seismic performance of the tunnel by combining the probabilistic seismic demand model with the limits on the engineering demand parameters. The numerical results indicate that PGA is the ground motion intensity measure suitable for the transverse seismic performance of the tunnels. The site type has the most significant influence on the structural damage, and site type IV is the most dangerous under an earthquake. The tunnel has better seismic resistance in the elastoplastic stage, and a tunnel with a large depth of burial is more hazardous than the one with a small depth of burial. A tunnel with a large cross-section has a higher probability of damage than the one with a small cross-section.

Key Words
tunnel; ground motion intensity measure; transverse seismic performance; engineering demand parameters; incremental dynamic analysis; fragility curves

Address
Zhengfang Dong:Institute of Geotechnical and Rail Transport Engineering, Henan University, Kaifeng, 475004, China

Chenyang Kuo:Institute of Geotechnical and Rail Transport Engineering, Henan University, Kaifeng, 475004, China

Chunshun Zhang:Department of Civil Engineering, Monash University Clayton Campus, 23 College Walk (B60), Clayton Campus, Melbourne, Australia

Qing Guo:Institute of Geotechnical and Rail Transport Engineering, Henan University, Kaifeng, 475004, China

Fankai Zeng:Institute of Geotechnical and Rail Transport Engineering, Henan University, Kaifeng, 475004, China


Abstract
In this article, a steel moment connection of beam to the column called a slotted web and bolt flange plate moment connection is introduced and the seismic performance of the connection is assessed by modeling the finite element. The connection consists of two slots in the beam web and bolted plates to the beam flange at the area of connection of the beam to the column to create a plastic hinge in an area farther from the column face, thus reducing the plastic strain equivalent to the panel zone and welding the beam-to-column connection area. The beam is connected to the slab on the side so that no plastic hinge is created against the side buckling. A numerical study has been performed to find the effectiveness of the proposed connection parameters. The results showed that following the limitations in this study, the SW-BFP connection had better hysteresis behavior than the SW connection. The deformation capacity of the connection in the SW-BFP connection (slotted web and bolt flange plate moment connection) has increased up to 112% compared to the connection of the beam with the slot web (SW). The sheet bolted to the beam flange on both sides of the beam with the slot die causes the buckling modes to occur later and reduces the stress by 23.93% in the beam-to-column connection area and 20.94% in the connection panel zone compared to the SW connection. Also, adding bolt-to-beam plates to the SW connection reduces the plastic strain in the panel zone by 87%, while the strain value in the beam-to-column connection area has reached zero.

Key Words
slotted connection; ductility; energy absorption; plastic hinge; beam to column connection

Address
S. Mohammad S. Kolbadi:Department of Civil Engineering, Faculty of Structure and Architecture, Technical and Vocational University (TVU), Tehran, Iran

Hosein Piri:Department of Civil Engineering, Shahroud university of Technology, Semnan, Iran

Ali Keyhani:Department of Civil Engineering, Shahroud university of Technology, Semnan, Iran

S. Mahdi S. Kolbadi:Department of Civil Engineering, KNTU of technology, Tehran, Iran

Masoud Mirtaheri:Department of Civil Engineering, KNTU of technology, Tehran, Iran


Abstract
As a new type of composite components, thin-walled concrete-filled steel tubes (CFSTs) have some advantages in terms of economy and processing. After the steel tube wall thins, the local buckling performance decreases and the stiffness decreases, which is not conducive to the structural safety. In this paper, combining the advantages of traditional spiral hoops and a stiffener, a new constraint in the form of a screw stiffener was proposed. On this basis, the composite member of thin-walled CFSTs with spiral ribs was put forward. The horizontal hysteretic test was carried out for the new composite column, and the failure mode, hysteretic characteristics, ductility, and energy dissipation capacity were obtained. The results showed that, compared with the traditional form, the seismic bearing capacity of the new composite column was increased by 11% and the ductility was increased by 45%. The deformation capacity was significantly improved. Based on experimental research, the seismic bearing capacity calculation and seismic damage assessment of the composite column were studied, and the practical calculation and the two-parameter damage assessment method considering the interaction between deformation and energy were proposed, which were in good agreement with the test results. This study can provide a technical basis for its engineering application. The composite column has good seismic performance, durability, and fire resistance, and thus has potential for application in practice.

Key Words
thin-walled concrete-filled steel tubular; spiral stiffener; hysteretic test; seismic performance; damage evaluation

Address
Zhen-shan Wang:State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, China/ School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an, China

Yong-jian Feng:School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an, China

Hong-chao Guo:School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an, China

Jun-long Lu:School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an, China

Jian-bo Tian:School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an, China


Abstract
Over the last decade, Algeria has realized the highway project. It covers more than 1,200 km joining Algeria's eastern and western borders in the northern part of the country. This region is characterized by a high level of seismic activity. In total, this project contains more than 530 bridges, knowing that the design of these bridges was carried out with a simplified method namely the coefficient method, and does not comply with the requirements of the new Algerian seismic code for bridges RPOA-2008. For this reason, the development of fragility curves for these structures is necessary. This paper aims to develop analytical fragility curves for component and system fragility curves for post-tensioned girder highway bridges that represent the most common configuration in Algeria taking into account different spectral intensity measurements and the soil class based on the shear wave velocity specified in the Algerian bridge design code. Incremental dynamic analysis (IDA) is performed longitudinally on the bridge. Sixty seismic ground motions are scaled and employed for the time history nonlinear analysis. A variety of intensity measurements are chosen and the optimal intensity measurement with the lowest dispersion is proposed.

Key Words
component and system fragility, incremental dynamic analysis, probabilistic seismic demand model, intensity measure, limit states

Address
Fouad Kehila:Department of Civil Engineering, National Earthquake Engineering Research Center CGS 01 Rue Kaddour RAHIM, BP 252, Hussein Dey, Algiers, Algeria

Mustapha Remki:Department of Civil Engineering, National Earthquake Engineering Research Center CGS 01 Rue Kaddour RAHIM, BP 252, Hussein Dey, Algiers, Algeria

Nadjib Hemaidi Zourgui:High National School of Built and Ground Works ENSTP, BP 32 Rue Sidi Garidi, Kouba, Algiers, Algeria

Abderrahmane Kibboua:Department of Civil Engineering, National Earthquake Engineering Research Center CGS 01 Rue Kaddour RAHIM, BP 252, Hussein Dey, Algiers, Algeria

Hakim Bechtoula:Department of Civil Engineering, National Earthquake Engineering Research Center CGS 01 Rue Kaddour RAHIM, BP 252, Hussein Dey, Algiers, Algeria


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