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Consistent Source-to-Site Distance Metrics in Ground-Motion Prediction Equations and Seismic Source Models for PSHA

Julian J. Bommer, M.EERI and Sinan Akkar

Earthquake Spectra 28, pp. 1-15 (2012); doi:http://dx.doi.org/10.1193/1.3672994

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Most modern ground-motion prediction equations (GMPE) use definitions of the source-to-site distance that reflect the dimensions of the fault rupture for larger earthquakes rather than using point-source measures relative to the epicenter or hypocenter. This is a positive development since it more realistically reflects the fact that energy is released from the crust around the entire fault rupture during a large earthquake. However, seismic source configurations defined for probabilistic seismic hazard analysis (PSHA) almost invariably include areas of distributed point-source seismicity in addition to linear fault sources, particularly in regions of lower earthquake activity. Herein, two GMPEs are derived from the same dataset to demonstrate the errors that can result from combining point-source simulations and extended-source distance metrics. The case is made for all ground-motion model developers to consider deriving pairs of equations, one using an extended-source distance metric, the other a point-source measure.

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89.20.Kk	Engineering
93.85.Rt	Seismic methods
02.50.Cw	Probability theory

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Empirical Correlations between Peak Ground Velocity and Spectrum-Based Intensity Measures

Brendon A. Bradley

Earthquake Spectra 28, pp. 17-35 (2012); doi:http://dx.doi.org/10.1193/1.3675582

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Empirical correlation equations between peak ground velocity (PGV) and several spectrum-based ground motion intensity measures are developed. The intensity measures examined in particular were: peak ground acceleration (PGA), 5% damped pseudo-spectral acceleration (SA), acceleration spectrum intensity (ASI), and spectrum intensity (SI). The computed correlations were obtained using ground motions from active shallow crustal earthquakes and four ground motion prediction equations. Results indicate that PGV is strongly correlated (i.e., a correlation coefficient of ρ = 0.89) with SI, moderately correlated with medium to long-period SA (i.e., ρ ≈ 0.8 for vibration periods 0.5–3.0 seconds), and also moderately correlated with short period SA, PGA and ASI (ρ ≈ 0.7-0.73). A simple example is used to illustrate one possible application of the developed correlation equations for ground motion selection.

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89.20.Kk	Engineering
91.30.Mv	Strong motions and shock waves
91.30.Px	Earthquakes

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Empirical Correlations between Cumulative Absolute Velocity and Amplitude-Based Ground Motion Intensity Measures

Brendon A. Bradley

Earthquake Spectra 28, pp. 37-54 (2012); doi:http://dx.doi.org/10.1193/1.3675580

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Empirical correlation equations are developed between cumulative absolute velocity (CAV) and other common ground motion intensity measures, namely, peak ground acceleration (PGA), peak ground velocity (PGV), 5% damped pseudo spectral acceleration (SA), acceleration spectrum intensity (ASI), spectrum intensity (SI), and displacement spectrum intensity (DSI). It is found that, for a given earthquake rupture, CAV has the strongest correlation with high and moderate frequency intensity measures (IMs), that is, ASI, PGA, PGV and high-frequency SA, and to a lesser extent with low frequency IMs (DSI and low-frequency SA). The largest positive correlations of approximately 0.7 however are not high in an absolute sense, a result of the cumulative nature of CAV. The equations allow estimation of the joint distribution of these intensity measures for a given earthquake rupture, enabling the inclusion of CAV, and its benefit as a cumulative intensity measure, in seismic hazard analysis, ground motion selection, and seismic response analysis.

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89.20.Kk	Engineering
91.30.Mv	Strong motions and shock waves

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Proposed Method for Probabilistic Estimation of Peak Component Acceleration Demands

Joshua S. Clayton and Ricardo A. Medina

Earthquake Spectra 28, pp. 55-75 (2012); doi:http://dx.doi.org/10.1193/1.3673623

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A probabilistic method is proposed to quantify peak component acceleration (PCA) demands for nonstructural components attached to elastic and inelastic structures. Incremental dynamic analyses and site-specific ground-motion hazard information are used to estimate PCA hazard curves and component uniform hazard spectra (CUHS) based on various structural and nonstructural parameters. For a given structural system, the primary parameters of interest are the location of the component within the structure, the ratio of the period of the component to the modal periods of the primary structure, and the component damping ratio. Representative results for shear wall structures illustrate the value of applying the method to acceleration-sensitive components, as the quantification of CUHS facilitates the implementation of performance-based design and evaluation approaches. The variability in the component responses presented highlights the need for a robust probabilistic seismic demand estimation methodology for nonstructural components in which the major sources of variability are incorporated.

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89.20.Kk	Engineering
81.40.Jj	Elasticity and anelasticity, stress-strain relations
46.40.Jj	Aeroelasticity and hydroelasticity
02.50.Cw	Probability theory

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Strong-Motion Data from Structural Response Recorders in Indian Earthquakes

Sudhir K. Jain, A. D. Roshan, Siddharth Yadav, Sonam Srivastava, and Prabir C. Basu

Earthquake Spectra 28, pp. 77-103 (2012); doi:http://dx.doi.org/10.1193/1.3672977

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In the 1960s several hundred structural response recorders (SRR) were installed all over India. An SRR is a simple instrument consisting of six seismoscopes that provide “maximum response” during an earthquake, without providing the time history. In the past earthquakes, these SRRs have provided several hundred records but they have not been effectively utilized for hazard studies because the measurements from these instruments are considered crude. This paper compares the data obtained from SRRs with that from more modern strong-motion accelerographs (SMAs) for four earthquakes in India. It is shown through statistical analysis that the response obtained from the SRRs is comparable to that from the SMAs. A method has been presented for estimating peak ground acceleration (PGA) from SRR data. Thus, it is shown that SRRs can provide a substantial amount of PGA data for attenuation studies. Many countries may find SRRs useful because of the low costs associated with their manufacture and maintenance.

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89.20.Kk	Engineering
93.85.Rt	Seismic methods

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Inelastic Responses of Two-Way Asymmetric-Plan Structures under Bidirectional Ground Excitations—Part I: Modal Parameters

Jui-Liang Lin, Keh-Chyuan Tsai, and Wen-Chia Yang

Earthquake Spectra 28, pp. 105-139 (2012); doi:http://dx.doi.org/10.1193/1.3672425

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It has been found that any one vibration “mode” of an inelastic multistory two-way asymmetrical building structure can be represented by a three-degree-of-freedom (3DOF) modal system representing two modal translations and one modal rotation. This study introduces the inelastic response spectra constructed from the inelastic 3DOF modal systems, which is specifically useful for multistory two-way asymmetric-plan buildings subjected to bidirectional ground excitations. These spectra for asymmetrical structures (SAS) provide the three-component inelastic peak modal responses of multistory two-way asymmetric-plan buildings subjected to bidirectional ground excitations. In order to construct the SAS, the independent elastic parameters of the 3DOF modal systems were identified and the inelastic 3DOF modal parameters versus the strength ratio relationships were established. The parametric study of the 3DOF modal parameters showed the ranges and the variation trends of these parameters. Two example buildings are analyzed to verify the effectiveness of the above-mentioned investigations.

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89.20.Kk	Engineering
43.40.-r	Structural acoustics and vibration
02.30.-f	Function theory, analysis

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Inelastic Responses of Two-Way Asymmetric-Plan Structures under Bidirectional Ground Excitations—Part II: Response Spectra

Jui-Liang Lin, Wen-Chia Yang, and Keh-Chyuan Tsai

Earthquake Spectra 28, pp. 141-157 (2012); doi:http://dx.doi.org/10.1193/1.3672426

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Based on the studies in the companion paper, this paper presents the inelastic response spectra for asymmetrical structures (SAS) under bidirectional ground excitations. Firstly, the constant-strength SAS were constructed and compared with the corresponding conventional constant-strength response spectra. It was found that the modal ductility demands of an asymmetric-plan structure could be significantly overestimated from the conventional constant-strength response spectra as the nonlinear “modal” rotation and translations may not be proportional. Furthermore, the translation-rotation interaction effect is not considered in the conventional constant-strength response spectra. Secondly, the influences of the three-degree-of-freedom (3DOF) modal parameters on the ductility demand were extensively studied. Thirdly, the normalized peak edge translation spectra were also investigated. It was found that the normalized peak edge translation resulting from a single vibration mode may be overestimated twofold by using the single-degree-of-freedom (SDOF) modal systems.

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89.20.Kk	Engineering
89.60.Gg	Impact of natural and man-made disasters
43.40.-r	Structural acoustics and vibration
46.35.+z	Viscoelasticity, plasticity, viscoplasticity

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Perception and Communication of Seismic Risk: The 6 April 2009 L’Aquila Earthquake Case Study

Fausto Marincioni, Federica Appiotti, Maurizio Ferretti, Caterina Antinori, Paola Melonaro, Antonio Pusceddu, and Roberto Oreficini-Rosi

Earthquake Spectra 28, pp. 159-183 (2012); doi:http://dx.doi.org/10.1193/1.3672928

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On Monday, 6 April 2009 at 3:32 a.m. (local time), a moment magnitude 6.3 earthquake with an epicenter located near the city of L’Aquila, in central Italy, killed 308 people, injured 1,500, left 22,000 homeless, and temporarily displaced another 65,000. This study examines a sample of the affected population and finds that despite the long list of historical earthquakes that struck the region and the swarm of foreshocks occurring up to four months before the main shock of 6 April, the residents of L’Aquila had a rather low earthquake risk perception and an unjustified confidence in the seismic safety of their houses. This low perception of earthquake risk and ignorance of the real structural resistance of buildings appear to have inhibited the individual and collective propensity to develop emergency plans. This situation was further exacerbated by the lack of clear and forthright communication from the emergency management authorities about the impossibility of precisely predicting earthquakes and about the risks posed by many of the city’s old buildings.

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89.20.Kk	Engineering
89.60.Gg	Impact of natural and man-made disasters
91.30.Mv	Strong motions and shock waves

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The Effects of Building Characteristics and Site Conditions on the Damage Distribution in Boumerdès after the 2003 Algeria Earthquake

Abdelghani Meslem, Fumio Yamazaki, Yoshihisa Maruyama, Djillali Benouar, Abderrahmane Kibboua, and Youcef Mehani

Earthquake Spectra 28, pp. 185-216 (2012); doi:http://dx.doi.org/10.1193/1.3675581

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This study highlights the major contributing factors to the observed damage distribution in the city of Boumerdès after the 2003 Algeria earthquake. The results of field investigations and statistical analyses show that a majority of the damaged buildings, mostly mid-rise reinforced concrete (RC) moment-frame systems, were located on steep slopes and small hilltops, along river valleys. The horizontal-to-vertical (H/V) ratios from free-field microtremor measurements at these sites did not show clear results. In contrast, buildings with the same structural characteristics located on flat ground did not suffer much damage, and clear peaks were observed from the H/V ratio curves. The amplification effects of topography have not been incorporated into the revised Algerian seismic code, but the results from this study show the importance of considering this factor when designing new buildings for earthquake resistance.

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89.20.Kk	Engineering
02.50.-r	Probability theory, stochastic processes, and statistics

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Numerical Evaluation of Nonlinear Response of Broad Cylindrical Steel Tanks under Multidimensional Earthquake Motion

Zuhal Ozdemir, Mhamed Souli, and Yasin M. Fahjan

Earthquake Spectra 28, pp. 217-238 (2012); doi:http://dx.doi.org/10.1193/1.3672996

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In this paper, a fluid-structure interaction (FSI) algorithm of the finite element method (FEM), which can take into account the effects of geometric and material nonlinearities of the tank, buckling of the tank shell, and nonlinear sloshing behavior of the contained liquid, is utilized to evaluate the actual behavior of broad cylindrical steel tanks when subjected to strong earthquake motions. In order to clarify a key question—whether anchoring would prevent earthquake damage to tanks—numerical analyses are carried out on the same tank model having two different support conditions: anchored and unanchored. In addition to two horizontal components of ground motion, the vertical component is also taken into account in order to determine the relative importance of vertical ground motion in the behavior of tanks. The consistency of provisions presented in current design codes and numerical analysis results is evaluated.

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89.20.Kk	Engineering
81.40.Lm	Deformation, plasticity, and creep
47.85.-g	Applied fluid mechanics
02.70.Dh	Finite-element and Galerkin methods
46.70.-p	Application of continuum mechanics to structures
46.32.+x	Static buckling and instability

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Performance of the San Salvatore Regional Hospital in the 2009 L’Aquila Earthquake

H. John Price, Adriano De Sortis, and Marko Schotanus, M.EERI

Earthquake Spectra 28, pp. 239-256 (2012); doi:http://dx.doi.org/10.1193/1.3673595

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The San Salvatore Hospital in Coppito was closed shortly after the 6 April 2009 L’Aquila earthquake, even though the buildings on its campus experienced only limited and localized structural damage. The decision to close part or all of an essential facility such as a hospital can be easily made in the heat of the moment after a disaster, but reopening even portions of such a facility is far more complex and raises a large number of operational issues. A documented pre-established program for post-event safety inspections, as well as training in its implementation for both on-site and backup personnel, is vital to the continued operation of any essential facility. While continued operation after an event may be the targeted goal, it may not actually be fully achieved, in particular for older facilities, and some disruption is to be expected. Management of realistic expectations is a vital part of the program for post-event safety inspections.

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89.20.Kk

Engineering

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Updated PGA, PGV, and Spectral Acceleration Attenuation Relations for Iran

Hamid Saffari, Yasuko Kuwata, Shiro Takada, and Abbas Mahdavian

Earthquake Spectra 28, pp. 257-276 (2012); doi:http://dx.doi.org/10.1193/1.3673622

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We have developed updated attenuation relations for peak ground acceleration (PGA), peak ground velocity (PGV), and acceleration response spectra with 5% damping on the basis of the data (78 earthquakes and 351 records) pertaining to strong ground motion in Iran. Moment magnitude, distance, fault mechanism, site class, and zone were the model parameters considered. A term for the saturation of the acceleration amplitude was also used in the model in order to improve the estimations in near-source regions. A nonlinear regression analysis was performed to obtain the coefficients. A comparison between the data set used in the current study for Iran and two next generation attenuation (NGA) models showed good correlation between our model and the Campbell-Bozorgnia NGA model. The model described is applicable for moment magnitudes from 5.0 to 7.3, distances from 15 to 135 km, and site classes with an average shear-wave velocity at a subsurface depth of 30 m (AVS30) of more than 175 m/s.

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89.20.Kk	Engineering
91.30.Px	Earthquakes

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Shake Table Tests on One-Quarter Scale Models of Masonry Houses Retrofitted with PP-Band Mesh

Navaratnarajah Sathiparan, Paola Mayorca, and Kimiro Meguro

Earthquake Spectra 28, pp. 277-299 (2012); doi:http://dx.doi.org/10.1193/1.3675357

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This paper introduces a technically feasible and economically affordable retrofitting option for seismically vulnerable masonry structures in developing countries using polypropylene bands (PP-bands). The results of the basic material tests and shake table tests on building models show that the PP-band retrofitting technique can enhance the safety of both existing and new masonry buildings, even during severe ground motions, for instance an earthquake with a Japan Meteorological Agency (JMA) seismic intensity of 7. Therefore, the proposed method is an optimum solution for promoting safer building construction in developing countries and can contribute to earthquake disaster mitigation in the future.

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89.20.Kk	Engineering
89.60.Gg	Impact of natural and man-made disasters
81.70.Bt	Mechanical testing, impact tests, static and dynamic loads

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Seismic Damage to Bridges during the 27 February 2010 Magnitude 8.8 Chile Earthquake

Frank Schanack, Galo Valdebenito, and Jorge Alvial

Earthquake Spectra 28, pp. 301-315 (2012); doi:http://dx.doi.org/10.1193/1.3672424

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The 27 February 2010 Chile earthquake is currently the fifth-strongest earthquake measured in the world. Despite this fact, the damage to the road infrastructure can be classified as moderate. Of the 6,000 state bridges in the affected region, only about 30 bridges had to be closed to traffic. This paper includes the most pertinent results of a field investigation of the seismic damage to 100 bridges. The majority of the bridges exhibited only minor damage such as concrete spalling, expansion joint damage, and settlement of the embankment. However, severe damage was reported in 19 bridges, including web rupture due to a missing end diaphragm, a span collapse due to insufficient anchorage and missing stoppers, a span collapse due to a small seat length, and cracking at the welding notch in the steel girders. The most important lessons learned are described and recommendations for future bridge designs are given.

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89.20.Kk	Engineering
89.60.Gg	Impact of natural and man-made disasters
46.50.+a	Fracture mechanics, fatigue and cracks

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Ground Motion Recordings from the M_w 6.3 2009 L’Aquila Earthquake in Italy and their Engineering Implications

Jonathan P. Stewart, M.EERI, Giuseppe Lanzo, Alessandro Pagliaroli, Giuseppe Scasserra, Giuseppe Di Capua, Silvia Peppoloni, Robert Darragh, M.EERI, and Nicholas Gregor, M.EERI

Earthquake Spectra 28, pp. 317-345 (2012); doi:http://dx.doi.org/10.1193/1.3673621

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The 2009 L’Aquila earthquake sequence includes the April 6 M_w 6.3 main shock and triggered events on April 7 and 9, each recorded on a digital network having five stations on the hanging wall of the main shock fault. We describe a geometric source model drawing upon inversions by others. We describe record-specific ground motion data processing that includes the incorporation of static displacements of up to 13 cm (downdrop of hanging wall). The resulting database includes 47, 38, and 31 corrected triaxial recordings from the April 6, 7, and 9 events, respectively. We present site conditions for recording stations, including recent surface wave and borehole geophysics. We demonstrate that the high-frequency data are weaker than expected for normal fault earthquakes of these magnitudes and that the data attenuate with distance at rates generally consistent with modified next generation attenuation (NGA) equations for Italy that were available prior to the event.

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89.60.Gg	Impact of natural and man-made disasters
91.30.Px	Earthquakes
91.30.Mv	Strong motions and shock waves
89.20.Kk	Engineering

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Estimated Temporal Variation of Losses Due to a Recurrence of the 1933 Long Beach Earthquake

Jennifer Swift, M.EERI, John Wilson, and Toan Nguyen Le

Earthquake Spectra 28, pp. 347-365 (2012); doi:http://dx.doi.org/10.1193/1.3672995

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The temporal variation of damage and loss estimates are presented in decadal increments since 1950 for an earthquake on the Newport-Inglewood Fault (NIF) equivalent to the M_w 6.4 1933 Long Beach earthquake. Deterministic damage and loss calculations were performed utilizing Hazus-MH software and updated structural inventories. We estimate that building stock loss density (total losses within each census tract divided by tract area) due to the recurrence of this event in 1950 would have been about $84 million, increasing to $300 million in 2006 (2002 replacement costs). With the phenomenal growth in new construction in Long Beach over the past 50 years, the results indicate that the proportion of wood and unreinforced masonry (URM) buildings predicted to suffer at least moderate damage has stabilized. Given the many seismic sources in this region which also pose significant threats, we demonstrate that modeling tools such as Hazus-MH can provide meaningful estimates of future losses from earthquakes.

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89.20.Kk	Engineering
89.60.Ec	Environmental safety
89.60.Gg	Impact of natural and man-made disasters

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Experimental and Analytical Studies of Hospital Piping Assemblies Subjected to Seismic Loading

Arash E. Zaghi, A.M.EERI, E. “Manos” Maragakis, M.EERI, Ahmad Itani, M.EERI, and Elliott Goodwin

Earthquake Spectra 28, pp. 367-384 (2012); doi:http://dx.doi.org/10.1193/1.3672911

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The seismic characteristics of welded and threaded hospital piping assemblies were investigated with and without seismic restrainers under various intensities of seismic loading using a biaxial shake table. Experimental results showed that the restrainers limited the displacements; however, they did not reduce the acceleration responses. No leakage was detected in the welded assembly up to a drift ratio of 4.3%; however, threaded piping suffered minor leaks at a drift ratio of 2.2% and experienced connection failure at a drift ratio of 4.3%. A simplified computational model was developed and calibrated with experimental data using SAP2000. The effective stiffness of the seismic restrainers was determined to be 10% of full stiffness due to their initial slack. The analyses showed that the dynamic response of the piping system as braced in these experiments with similar boundary conditions was predominantly kinematic with minimal inertial effects.

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89.20.Kk	Engineering
91.30.Mv	Strong motions and shock waves
46.40.-f	Vibrations and mechanical waves

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Comparison of Peak Ductility Demand of Inelastic SDOF Systems in Maximum Elastic Response and Major Principal Directions

Katsuichiro Goda, M.EERI

Earthquake Spectra 28, pp. 385-399 (2012); doi:http://dx.doi.org/10.1193/1.3673606

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This study investigates the orientation dependency of the peak ductility demand of inelastic single-degree-of-freedom (SDOF) systems of known strengths by taking the record-to-record variability of seismic effects into account. The probabilistic characteristics of the peak ductility demand in recording directions on the horizontal plane are compared with those in the maximum elastic response direction and the major principal direction. The analysis results indicate that the peak ductility demand depends on how input ground motions are defined in terms of record orientation. The observed orientation dependency can be explained by noting the response spectral shapes of scaled ground motion records in specific directions. The results have important implications for current earthquake engineering practice, suggesting that separate peak ductility demand models should be used for different ground motion directions to evaluate the seismic performance of structures consistently and without bias.

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89.20.Kk	Engineering
81.40.Lm	Deformation, plasticity, and creep
46.35.+z	Viscoelasticity, plasticity, viscoplasticity
02.50.Cw	Probability theory