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CONTENTS
Volume 18, Number 3, March 2020
 

Abstract
The scope of this study is the comparison between experimental results of tests performed on a base isolated building using helical wire rope isolators (WRs), and results of Nonlinear Response History Analyses (NRHAs) performed using SAP 2000, a commercial software for structural analysis. In the first stage of this research, WRs have been tested under shear deformation beyond their linear range of deformation, and analytical models have been derived to describe the nonlinear response of the bearings under different directions of loading. On the following stage, shaking table tests have been carried out on a 1/3 scale steel model isolated at the base by means of curved surface sliders (CSS) and WRs. The response of the structure under ground motion excitation has been compared to that obtained using numerical analyses in SAP 2000. The feasibility of modelling the nonlinear behavior of the tested isolation layer using multilinear link elements embedded in SAP 2000 is discussed in this paper, together with the advantages of using WRs as supplemental devices for CSSs base isolated structures

Key Words
seismic base isolation; wire rope isolators; shaking table tests; building structure

Address
Andrea Calabrese: Dept. of Civil Engineering & Construction Engineering Management, California State Univ. Long Beach, Long Beach, CA, USA
Mariacristina Spizzuoco:Department of Structures for Engineering and Architecture, University of Naples Federico II, Via Claudio 21, Naples, Italy
Daniele Losanno: Department of Structures for Engineering and Architecture, University of Naples Federico II, Via Claudio 21, Naples, Italy
Arman Barjani: Dept. of Civil Engineering & Construction Engineering Management, California State Univ. Long Beach, Long Beach, CA, USA



Abstract
Dams are important structures for management of water supply for irrigation or drinking, flood control, and electricity generation. In seismic regions, the structural safety of concrete gravity dams is important due to the high potential of life and economic loss if they fail. Therefore, the seismic analysis of existing dams in seismically active regions is crucial for predicting responses of dams to ground motions. In this paper, earthquake response of concrete gravity dams is investigated using the finite element (FE) method. The FE model accounts for dam-water-foundation rock interaction by considering compressible water, flexible foundation effects, and absorptive reservoir bottom materials. Several uncertainties regarding structural attributes of the dam and external actions are considered to obtain the fragility curves of the dam-water-foundation rock system. The structural uncertainties are sampled using the Latin Hypercube Sampling method. The Pine Flat Dam in the Central Valley of Fresno County, California, is selected to demonstrate the methodology for several limit states. The fragility curves for base sliding, and excessive deformation limit states are obtained by performing non-linear time history analyses. Tensile cracking including the complex state of stress that occurs in dams was also considered. Normal, Log-Normal and Weibull distribution types are considered as possible fits for fragility curves. It was found that the effect of the minimum principal stress on tensile strength is insignificant. It is also found that the probability of failure of tensile cracking is higher than that for base sliding of the dam. Furthermore, the loss of reservoir control is unlikely for a moderate earthquake.

Key Words
concrete gravity dams; fragility; safety; reliability; probability; earthquake engineering

Address
Ufuk Sen:General Directorate of State Hydraulic Works, Turkey
Ayman M. Okeil: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, Louisiana, USA

Abstract
The KiK-net by NIED is a vertical array measurement system. In the database of KiK-net, singular pulse waves were observed in the seismic record at the borehole of TTRH02 during the mainshock (the magnitude of Japan Meteorological Agency (MJ) 7.3, MW 6.8) and aftershock (Mj 4.2) of Tottori-ken Seibu earthquake in 2000. Singular pulse waves were also detected in the seismic records at the borehole of IWTH25 during the Iwate-Miyagi Nairiku earthquake in 2008 (MJ 7.2, MW 6.9). These pulse waves are investigated by using the wave shape analysis methods, e.g., the non-stationary Fourier spectra and the double integrated displacement profiles. Two types of vibration modes are discriminated as the occurrence mechanism of the singular pulse waves. One corresponds to the reversal points in the displacement profile with the amplitude from 10-4 m to 10-1 m, which is mainly related to the fault activity and the amplification pass including the mechanical amplification (collision) of the seismograph in the casing pipe. The other is the cyclic pulse waves in the interval of reversal points, which is estimated as the backlash of the seismograph itself with the amplitude from 10-5 m to 10-4 m.

Key Words
wave shape analysis; non-stationary fourier spectra; band-pass filter; KiK-net; borehole; backlash of seismograph in casing pipe; pulse wave

Address
Nuclear power department, Kajima Corporation, Tokyo 107-8348, Japan

Abstract
The usage of conventional tuned mass damper (TMD) was proved as an effective method for passive mitigating vortex-induced vibration (VIV) of a bridge deck. Although a variety of linear TMD systems have been so far utilized for vibration control of suspension bridges, a sensitive TMD mechanism to wind spectrum frequency is lacking. Here, we introduce a bistable tuned mass damper (BTMD) mechanism which has an exceptional sensitivity to a broadband input of vortex shedding velocity for suppressing VIV in suspension bridge deck. By use of the Monte Carlo simulation, performance of the nonlinear BTMD is shown to be more efficient than the conventional linear TMD under two different wind load excitations of harmonic (sinusoidal) and broadband input of vortex shedding. Consequently, an appropriate algorithm is proposed to optimize the design parameters of the nonlinear BTMD for Kap Shui Mun Bridge, and then the BTMD system is localized for the interior deck of the suspension bridge.

Key Words
bistable tuned mass damper (BTMD); nonlinear vibration control; wind vortex shedding; suspension bridges

Address
Saman Farhangdoust: Department of Civil and Environmental Engineering, Florida International University, Miami, FL 33174, USA
Pejman Eghbali:School of Railway Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran
Davood Younesian:School of Railway Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran


Abstract
The aim of the present contribution is to consider and underline the essential interactions among the historical knowledge, the seismic vulnerability assessment, the investigation experimental tools, the preservation of the architectural quality and the strengthening design in regard to architectural heritage conservation. These topics are argued in relation to Palazzo Murena in Perugia, designed in the eighteenth century by the famous Architect Luigi Vanvitelli, and currently headquarters of the city\' s University. Based on the surveys and the visual inspections, a preliminary a priori global analysis has been performed by means of the FME method. The obtained results permitted to plan an experimental tests campaign inclusive of structural health monitoring. The new achieved \"knowledge\" of the building allowed to refine the seismic safety assessment. In particular it was highlighted that the \"mezzanine floor\" can be a vulnerable element of the building with the collapse of its masonry walls. Preserving the architectural characteristics, a local reinforcement intervention is proposed for the above-mentioned level; this consists of the application of plaster with FRCM, assuring an adequate strength, without burden the masonry structure with additional weight, and therefore a decreasing of the seismic vulnerability. The necessity to consider, in this ongoing research, other local mechanisms is highlighted in the unfolding of the last part of work.

Key Words
architectural heritage preservation; irregular masonry structures; pushover analysis; damage assessment, F.R.C.M strengthening

Address
Riccardo Liberotti: Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Federico Cluni :Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy
Vittorio Gusella: Department of Civil and Environmental Engineering, University of Perugia, Perugia, Italy



Abstract
Experimental testing has been considered as one of the most straightforward approaches to realize the structural behavior for earthquake engineering studies. Recently, novel and advanced experimental techniques, which combine numerical simulation with experimental testing, have been developed and applied to structural testing practically. However, researchers have to take the risk of damaging specimens or facilities during the process of developing and validating new experimental methods. In view of this, a small-scale structural laboratory has been designed and constructed in order to verify the effectiveness of newly developed experimental technique before it is applied to large-scale testing for safety concerns in this paper. Two orthogonal steel reaction walls and one steel T-slotted reaction floor are designed and analyzed. Accordingly, a large variety of experimental setups can be completed by installing servo-hydraulic actuators and fixtures depending on different research purposes. Meanwhile, a state-of-the-art digital controller and multiple real-time computation machines are allocated. The integration of hardware and software interfaces provides the feasibility and flexibility of developing novel experimental methods that used to be difficult to complete in conventional structural laboratories. A simple experimental demonstration is presented which utilizes part of the hardware and software in the small-scale structural laboratory. Finally, experimental layouts of future potential development and application are addressed and discussed, providing the practitioners with valuable reference for experimental earthquake engineering.

Key Words
small-scale structural laboratory; structural testing; advanced experimental technique; earthquake engineering

Address
Pei-Ching Chen: Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, No.43, Sec.4, Keelung Rd., Taipei 10607, Taiwan
Guan-Chung Ting : Department of Mechanical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
Chao‐Hsien Li: Department of Structural Engineering, UC San Diego, 9500 Gilman Drive, La Jolla, California, United States

Abstract
Since the peak seismic response of a base-isolated building strongly depends on the characteristics of the imposed seismic ground motion, the behavior of a base-isolated building under different seismic ground motions is studied, in order to better assess their effects on its peak seismic response. Specifically, the behavior of a typical steel building is examined as base-isolated with elastomeric bearings, while the effect of near-fault ground motions is studied by imposing 7 pairs of near- and 7 pairs of far-fault seismic records, from the same 7 earthquake events, to the building, under 3 different loading combinations, through three-dimensional (3D) nonlinear dynamic analyses, conducted with SAP2000. The results indicate that near-fault seismic components are more likely to increase the building\'s peak seismic response than the corresponding far-fault components. Furthermore, the direction of the imposed earthquake excitations is also varied by rotating the imposed pairs of seismic records from 0° to 360°,with respect to the major construction axes. It is observed that the peak seismic responses along the critical incident angles, which in general differ from the major horizontal construction axes of the building, are significantly higher. Moreover, the influence of 5% and 10% accidental mass eccentricities is also studied, revealing that when considering accidental mass eccentricities the peak relative displacements of the base isolated building at the isolation level are substantially increased, while the peak floor accelerations and interstory drifts of its superstructure are only slightly affected.

Key Words
base isolation; seismic isolation; peak seismic response; near vs. far fault; incident angle

Address
Constantina Pavlidou:Departement of Civil & Environmental Engineering, School of Engineering, University of Cyprus, Nicosia, Cyprus
Petros Komodromos:Departement of Civil & Environmental Engineering, School of Engineering, University of Cyprus, Nicosia, Cyprus

Abstract
Incremental dynamic analysis (IDA) widely uses for the collapse risk assessment procedures of buildings. In this study, an IDA-based collapse risk assessment methodology is proposed, which employs a novel approach for detecting the near-collapse (NC) limit state. The proposed approach uses the modal pushover analysis results to calculate the maximum inter-story drift ratio of the structure. This value, which is used as the upper-bound limit in the IDA process, depends on the structural characteristics and global seismic responses of the structure. In this paper, steel mid-rise intermediate moment resisting frames (IMRFs) have selected as case studies, and their collapse risk parameters are evaluated by the suggested methodology. The composite action of a concrete floor slab and steel beams, and the interaction between the infill walls and the frames could change the collapse mechanism of the structure. In this study, the influences of the metal deck floor and autoclaved aerated concrete (AAC) masonry infill walls with uniform distribution are investigated on the seismic collapse risk of the IMRFs using the proposed methodology. The results demonstrate that the suggested modified IDA method can accurately discover the near-collapse limit state. Also, this method leads to much fewer steps and lower calculation costs rather than the current IDA method. Moreover, the results show that the concrete slab and the AAC infill walls can change the collapse parameters of the structure and should be considered in the analytical modeling and the collapse assessment process of the steel mid-rise intermediate moment resisting frames.

Key Words
IDA method; seismic collapse risk; near-collapse limit state; steel moment-resisting frames; AAC infill walls; composite action

Address
Mohammad M. Maddah :Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan St., North Dibajee, Farmanieh. Tehran, Iran
Sassan Eshghi:Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan St., North Dibajee, Farmanieh. Tehran, Iran

Abstract
Four full-scaled partially confined and unconfined masonry panels were tested with monotonic lateral loads. To study the effects of vertical force and boundary columns, two specimens with no boundary columns were subjected to different vertical forces, while two wing-wall specimens had the column placed eccentrically and in the middle, respectively. The specimens with no boundary columns exhibited ductile rocking behavior, where the lateral strength increased with increasing vertical compression. The wing-wall specimens with columns behaved as strut-and-tie systems. The column-panel interaction resulted in greater strength, lower deformation capacity and differences in failure modes. A comparison with analytical models showed that rocking strength can be accurately estimated using vertical force and the panel aspect ratio for panels with no boundary columns. The estimation for lateral strength on the basis of a panel section area indicated scattered error for wing-wall specimens.

Key Words
masonry; panels; experimentation; confinement

Address
Yi-Hsuan Tu:Department of Architecture, National Cheng Kung University, #1 University Road, Tainan City 701, Taiwan
Ting-Yi:Department of Architecture, National Cheng Kung University, #1 University Road, Tainan City 701, Taiwan
Tsung-Hua Chuang:TOP Associates, Architects, Planners & Engineers, 15F, #89, Tongde 6th St., Taoyuan Dist., Taoyuan City 330, Taiwan

Abstract
The use of passive energy dissipation devices has been widely used in the construction industry to minimize the probability of damage occurred under intense ground motion. In this study, collapse margin ratio (CMR) and fragility curves are the main parameters in the assessment to characterize the collapse safety of the structures. The assessment is done on three types of RC frame structures, incorporating three types of dampers, viscoelastic, friction, and BRB dampers. The Incremental dynamic analyses (IDA) were performed by simulating an array of 20 strong ground motion (SGM) records considering both far-field and near-field seismic scenarios that were followed by fragility curves. With respect to far-field ground motion records, the CMR values of the selected frames indicate to be higher and reachable to safety margin more than those under near-field ground motion records that introduce a high devastating impact on the structures compared to far-field excitations. This implies that the near field impact affects the ground movements at the site by attenuation the direction and causing high-frequency filtration. Besides that, the results show that the viscoelastic damper gives better performance for the structures in terms of reducing the damages compared to the other energy dissipation devices during earthquakes.

Key Words
collapse margin ratio; dampers; far-field; near-field; fragility curve; building resilience

Address
Puteri Nihal Che Kamaludin:School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
Moustafa Moufid Kassem:School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
Ehsan Noroozinejad Farsangi:Faculty of Civil and Surveying Engineering, Graduate University of Advanced Technology, Kerman, Iran
Fadzli Mohamed Nazri:School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
Eiki Yamaguchi:Department of Civil Engineering Kyushu Institute of Technology Tobata, Kitakyushu 804-8550, Japan



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