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CONTENTS
Volume 22, Number 6, June 2022
 

Abstract
Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

Key Words
concentric circular rings; energy absorption; shear buckling; shear capacity; slenderness ratio; steel plate shear wall

Address
Ali Akbar Farrokhi:Department of Civil Engineering, Nour Branch, Islamic Azad University, H25G+735, Nour, Iran
Sepideh Rahimi:Department of Civil Engineering, Nour Branch, Islamic Azad University, H25G+735, Nour, Iran
Morteza Hosseinali Beygi:Faculty of Civil Engineering, Babol Noshirvani University of Technology, HM6J+F64, Babol, Iran
Mohamad Hoseinzadeh:Department of Civil Engineering, Nour Branch, Islamic Azad University, H25G+735, Nour, Iran

Abstract
The quasi-static finite element (FE) approaches are widely used for the seismic analysis of tunnels. However, the conventional quasi-static approaches may cause significant deviations when the tunnel excavation process is simulated prior to the quasi-static analysis. In addition, they cannot account for vertical excitations. Therefore, this paper first highlights the limitations of conventional approaches. A hybrid quasi-static FE approach is subsequently proposed and extensively validated for various conditions. The hybrid approach is simple and not time consuming, and it can be used for the preliminary seismic design of tunnels, especially when the tunnel excavation and vertically propagating P-waves are considered.

Key Words
finite element; P-waves; quasi-static; seismic analysis; tunnel excavation

Address
Wusheng Zhao:State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,Chinese Academy of Sciences, Wuhan, China,University of Chinese Academy of Sciences, Beijing 100049, China
Kun Zhong:State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,Chinese Academy of Sciences, Wuhan, China,University of Chinese Academy of Sciences, Beijing 100049, China
Weizhong Chen:State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,Chinese Academy of Sciences, Wuhan, China,University of Chinese Academy of Sciences, Beijing 100049, China
Peiyao Xie:State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,Chinese Academy of Sciences, Wuhan, China,University of Chinese Academy of Sciences, Beijing 100049, China

Abstract
It is of great importance to be able to evaluate different structural systems not only based on their seismic performance but also considering their lifetime service costs. Many structural systems exist that can meet the engineering requirements for different performance levels; therefore, these systems shall be selected based on their economic costs over time. In this paper, two structural systems, including special steel moment-resisting and the ordinary concentric braced frames, are considered, which are designed to meet the three performance levels: Immediate Occupancy (IO), Life Safety (LS), Collapse Prevention (CP). The seismic behavior of these two systems is studied under three strong ground motions (i.e., Tabas, Bam, Kajour earthquake records) using the Perform3D package, and the incurred damages to the studied systems are examined at two hazard levels. Economic analyses were performed to determine the most economical structural system to meet the specified performance level requirements, considering the initial cost and costs associated with damages of an earthquake that occurred during their lifetime. In essence, the economic lifetime study results show that the special moment-resisting frames at IO and LS performance levels are at least 20% more economical than braced frames. The result of the study for these building systems with different heights designed for different performance levels also shows it is more economical from the perspective of long-term ownership of the property to design for higher performance levels even though the initial construction cost is higher.

Key Words
cost; economic analysis; performance-based earthquake engineering; performance level; steel structure

Address
Hamid RavanshadNia:Department of Civil Engineering, Tarbiat Modares University of Tehran, Iran
Hamzeh Shakib:Department of Civil Engineering, Tarbiat Modares University of Tehran, Iran
Mokhtar Ansari:Department of Civil Engineering, Bozorgmehr University of Qaenat, Qaen, Iran
Amir Safiey:Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, CO, U.S.A.

Abstract
The residual displacement ratio (RDRs) response spectra have been generally used as an important means to evaluate the post-earthquake repairability, and the ratios of residual to maximum inelastic displacement are considered to be more appropriate for development of the spectra. This methodology, however, assumes that the expected residual displacement can be computed as the product of the RDRs and maximum inelastic displacement, without considering the correlation between these two variables, which inevitably introduces potential systematic error. For providing an adequately accurate estimate of residual displacement, while accounting for the collapse resistance performance prior to the repairability evaluation, a probability-based procedure to estimate the residual displacement demands using the nonlinear static analysis (NSA) is developed for single-degree-of-freedom (SDOF) systems. To this end, the energy-based equivalent damping ratio used for NSA is revised to obtain the maximum displacement coincident with the nonlinear time history analysis (NTHA) results in the mean sense. Then, the possible systematic error resulted from RDRs spectra methodology is examined based on the NTHA results of SDOF systems. Finally, the statistical relation between the residual displacement and the NSA-based maximum displacement is established. The results indicate that the energy-based equivalent damping ratio will underestimate the damping for short period ranges, and overestimate the damping for longer period ranges. The RDRs spectra methodology generally leads to the results being non-conservative, depending on post-yield stiffness. The proposed approach emphasizes that the repairability evaluation should be based on the premise of no collapse, which matches with the current performance-based seismic assessment procedure.

Key Words
equivalent damping ratio; maximum inelastic displacement; nonlinear static analysis; probabilistic analysis; residual displacement; SDOF systems

Address
Zhibin Feng:Faculty of Infrastructure Engineering, Dalian University of Technology, No.2 Linggong Road, Ganjingzi District, Dalian, China
Jinxin Gong:Faculty of Infrastructure Engineering, Dalian University of Technology, No.2 Linggong Road, Ganjingzi District, Dalian, China

Abstract
Using the nonlinear static procedures has become very common in seismic codes to achieve the nonlinear response of the structure during an earthquake. The capacity spectrum method (CSM) adopted in ATC-40 is considered as one of the most known and useful procedures. For this procedure the seismic demand can be approximated from the maximum deformation of an equivalent linear elastic Single-Degree-of-Freedom system (SDOF) that has an equivalent damping ratio and period by using an iterative procedure. Data from the results of this procedure are plotted in acceleration- displacement response spectrum (ADRS) format. Different improvements have been made in order to have more accurate results compared to the Non Linear Time History Analysis (NL-THA). A new procedure is presented in this paper where the iteration process shall not be required. This will be done by estimation the ductility demand response spectrum (DDRS) and the corresponding effective damping of the bilinear system based on a new parameter of control, called normalized yield strength coefficient (η), while retaining the attraction of graphical implementation of the improved procedure of the FEMA-440. The proposed procedure accuracy should be verified with the NL-THA analysis results as a first implementation. The comparison shows that the new procedure provided a good estimation of the nonlinear response of the structure compared with those obtained when using the NL-THA analysis.

Key Words
capacity spectrum; ductility/ductility factor; inelastic response; pushover analysis; response spectrum

Address
Abdelmounaim Mechaala:National Earthquake Engineering Research Center, CGS, Rue Kaddour Rahim, BP 252 Hussein-Dey, Algiers, Algeria
Benazouz Chikh:Laboratoire TPITE, Ecole Nationale Supérieure des Travaux Publics (ENSTP), Algiers, Algeria

Abstract
One of the most important parameters affecting nonlinear soil-structure interaction, especially rocking foundation, is the vertical factor of safety (F.Sy). In this research, the effect of F.Sy on the behavior of rocking foundations was experimentally investigated. A set of slow, cyclic, horizontal loading tests was conducted on elastic SDOF structures with different shallow foundations. Vertical bearing capacity tests also were conducted to determine the F.Sy more precisely. Furthermore, 10% silt was mixed with the dry sand at a 5% moisture content to reach the minimum apparent cohesion. The results of the vertical bearing capacity tests showed that the bearing capacity coefficients (Nc and Ny) were influenced by the scaling effect. The results of horizontal cyclic loading tests showed that the trend of increase in capacity was substantially related to the source of nonlinearity and it varied by changing F.Sy. Stiffness degradation was found to occur in the final cycles of loading. The results indicated that the moment capacity and damping ratio of the system in models with lower F.Sy values depended on soil specifications such cohesiveness or non-cohesiveness and were not just a function of F.Sy.

Key Words
hysteresis damping ratio; moment capacity; residual rotation; rocking foundation; scaling effect; settlement; soil-structure interaction; vertical factor of safety

Address
S.M. Hadi Moosavian:School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran
Abbas Ghalandarzadeh:School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran
Abdollah Hosseini:School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran

Abstract
To study the empirical seismic fragility of a reinforced concrete girder bridge, based on the theory of numerical analysis and probability modelling, a regression fragility method of a rapid fragility prediction model (Gaussian first-order regression probability model) considering empirical seismic damage is proposed. A total of 1,069 reinforced concrete girder bridges of 22 highways were used to verify the model, and the vulnerability function, plane, surface and curve model of reinforced concrete girder bridges (simple supported girder bridges and continuous girder bridges) considering the number of samples in multiple intensity regions were established. The new empirical seismic damage probability matrix and curve models of observation frequency and damage exceeding probability are developed in multiple intensity regions. A comparative vulnerability analysis between simple supported girder bridges and continuous girder bridges is provided. Depending on the theory of the regional mean seismic damage index matrix model, the empirical seismic damage prediction probability matrix is embedded in the multidimensional mean seismic damage index matrix model, and the regional rapid prediction matrix and curve of reinforced concrete girder bridges, simple supported girder bridges and continuous girder bridges in multiple intensity regions based on mean seismic damage index parameters are developed. The established multidimensional group bridge vulnerability model can be used to quantify and predict the fragility of bridges in multiple intensity regions and the fragility assessment of regional group reinforced concrete girder bridges in the future.

Key Words
comparison of fragility between simple supported girder bridge and continuous girder bridge; empirical regional rapid prediction fragility analysis; mean seismic damage index matrix; reinforced concrete group girder bridges; seismic intensity

Address
Si-Qi. Li:School of Civil Engineering, Heilongjiang University, No.74, Xuefu Road, Harbin City, China, School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin City, China, Longjian Road and Bridge Co., Ltd., No. 109, Songshan Road, Harbin City, China
Yong-Sheng. Chen:Institute of Engineering Mechanics, China Earthquake Administration, No.29, Xuefu Road, Harbin City, China
Hong-Bo. Liu:School of Civil Engineering, Heilongjiang University, No.74, Xuefu Road, Harbin City, China, Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education
Ke. Du:School of Civil Engineering, Heilongjiang University, No.74, Xuefu Road, Harbin City, China

Abstract
High-rise buildings (HRBs) are considered one of the most common structures nowadays due to the population growth, especially in crowded towns. The lack of land in crowded cities has led to the convergence of the HRBs and the absence of any gaps between them, especially in lands with weak soil (e.g., liquefaction-prone soil), but then during earthquakes, these structures may be exposed to the risk of collision between them due to the large increase in the horizontal displacements, which may be destructive in some cases to the one or both of these adjacent buildings. To evaluate methods of reducing the risk of collision between adjacent twin HRBs, this research investigates three vibration control methods to reduce the risk of collision due to five different earthquakes for the case of two adjacent reinforced concrete (RC) twin high-rise buildings of 15 floors height without gap distance between them, founded on raft foundation supported on piles inside a liquefaction-prone soil. Contact pounding elements between the two buildings (distributed at all floor levels and at the raft foundation level) are used to make the impact strength between the two buildings realistic. The mitigation methods investigated are the base isolation, the tuned mass damper (TMD) method (using traditional TMDs), and the pounding tuned mass damper (PTMD) method (using PTMDs connected between the two buildings). The results show that the PTMD method between the two adjacent RC twin high-rise buildings is more efficient than the other two methods in mitigating the earthquake-induced pounding risk.

Key Words
base isolation; high-rise buildings; lead rubber bearing; liquefaction-prone soil; piled raft foundation; pounding tuned mass damper (PTMD); reinforced concrete; seismic pounding; soil-structure interaction; tuned mass damper (TMD); vibration control

Address
Ahmed Abdelraheem Farghaly:Department of Civil and Architectural Constructions, Faculty of Technology and Education, Sohag University, Sohag, 82524, Egypt
Denise-Penelope N. Kontoni:Department of Civil Engineering, School of Engineering, University of the Peloponnese, GR-26334 Patras, Greece, School of Science and Technology, Hellenic Open University, GR-26335 Patras, Greece

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