This paper contains ground-motion prediction equations (GMPEs) for average horizontal-component ground motions as a function of earthquake magnitude, distance from source to site, local average shear-wave velocity, and fault type. Our equations are for peak ground acceleration (PGA), peak ground velocity (PGV), and 5%-damped pseudo-absolute-acceleration spectra (PSA) at periods between 0.01 s and 10 s. They were derived by empirical regression of an extensive strong-motion database compiled by the “PEER NGA” (Pacific Earthquake Engineering Research Center’s Next Generation Attenuation) project. For periods less than 1s , the analysis used 1,574 records from 58 mainshocks in the distance range from 0 km to 400 km (the number of available data decreased as period increased). The primary predictor variables are moment magnitude M, closest horizontal distance to the surface projection of the fault plane R JB , and the time-averaged shear-wave velocity from the surface to 30 m VS30. The equations are applicable for M =5–8 , RJB 200 km, and VS30= 180– 1300 m / s. DOI: 10.1193/1.2830434

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Ground-motion prediction equations for the average horizontal component of PGA, PGV, and 5%-damped PSA at spectral periods between 0.01 s and 10.0 s

We present a new empirical ground motion model for PGA, PGV, PGD and 5% damped linear elastic response spectra for periods ranging from 0.01– 10 s. The model was developed as part of the PEER Next Generation Attenuation (NGA) project. We used a subset of the PEER NGA database for which we excluded recordings and earthquakes that were believed to be inappropriate for estimating free-field ground motions from shallow earthquake mainshocks in active tectonic regimes. We developed relations for both the median and standard deviation of the geometric mean horizontal component of ground motion that we consider to be valid for magnitudes ranging from 4.0 up to 7.5–8.5 (depending on fault mechanism) and distances ranging from 0 – 200 km. The model explicitly includes the effects of magnitude saturation, magnitude-dependent attenuation, style of faulting, rupture depth, hanging-wall geometry, linear and nonlinear site response, 3-D basin response, and inter-event and intra-event variability. Soil nonlinearity causes the intra-event standard deviation to depend on the amplitude of PGA on reference rock rather than on magnitude, which leads to a decrease in aleatory uncertainty at high levels of ground shaking for sites located on soil. DOI: 10.1193/1.2857546

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NGA Ground Motion Model for the Geometric Mean Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from 0.01 to 10 s

The true performance of ground-motion prediction equations is often not fully appreciated until they are used in practice for seismic hazard analyses and applied to a wide range of scenarios and exceedance levels. This has been the case for equations published recently for the prediction of peak ground velocity (PGV), peak ground acceleration (PGA), and response spectral ordinates in Europe, the Middle East, and the Mediterranean (Akkar and Bommer 2007a,b). This paper presents an update that corrects the shortcomings identified in those equations, which are primarily, but not exclusively, related to the model for the ground-motion variability.

Strong-motion recording networks in Europe and the Middle East were first installed much later than in the United States and Japan but have grown considerably over the last four decades. The databanks of strong-motion data have grown in parallel with the accelerograph networks, and in addition to national collections there have been concerted efforts over more than two decades to develop and maintain a European database of associated metadata ( e.g. , Ambraseys et al. 2004).

As the database of strong-motion records from Europe, the Mediterranean region, and the Middle East has expanded, there have been two distinct trends in terms of developing empirical ground-motion prediction equations (GMPEs): equations derived from a large dataset covering several countries, generally of moderate-to-high seismicity; and equations derived from local databanks for application within national borders. We refer to the former as pan-European models, noting that this is for expedience since the equations are really derived for southern Europe, the Maghreb (North Africa), and the active areas of the Middle East. The history of the development of both pan-European and national equations is discussed by Bommer et al. (2010), who also review studies that consider the arguments for and against the existence of consistent regional …

Empirical Equations for the Prediction of PGA, PGV, and Spectral Accelerations in Europe, the Mediterranean Region, and the Middle East

Seismic Rehabilitation of Existing Buildings

In code-based seismic design and assessment it is often allowed the use of real records as an input for nonlinear dynamic analysis. On the other hand, international seismic guidelines, concerning this issue, have been found hardly applicable by practitioners. This is related to both the difficulty in rationally relating the ground motions to the hazard at the site and the required selection criteria, which do not favor the use of real records, but rather various types of spectrum matching signals. To overcome some of these obstacles a software tool for code-based real records selection was developed. REXEL, freely available at the website of the Italian network of earthquake engineering university labs (http://www.reluis.it/index_eng.html), allows to search for suites of waveforms, currently from the European Strong-motion Database, compatible to reference spectra being either user-defined or automatically generated according to Eurocode 8 and the recently released new Italian seismic code. The selection reflects the provisions of the considered codes and others found to be important by recent research on the topic. In the paper, record selection criteria are briefly reviewed first, and then the algorithms implemented in the software are discussed. Finally, via some examples, it is shown how REXEL can effectively be a contribution to code-based real records selection for seismic structural analysis.

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REXEL: computer aided record selection for code-based seismic structural analysis

Determining crack kinematics from imaged crack patterns

The region of Basel is considered one of the most seismically vulnerable in Switzerland: in 1356, a very damaging earthquake hit the city, which nowadays is characterized by a significant concentration of population and economic activities. Hence, the Canton of Basel and the Swiss Federal Office for the Environment have promoted a comprehensive experimental and numerical research program, spanning from the evaluation of the seismic vulnerability of Basel’s heritage building stock to the identification of appropriate retrofit strategies. In particular, the experimental program aims at characterizing the mechanical properties of natural stone masonry and investigating the seismic performance of building aggregates typical of the historical city center. To this end, a unidirectional shake-table test was performed on the half-scale model of a natural stone masonry building aggregate, incorporating the main architectural and structural features of existing buildings in Basel’s historical center. The aggregate consisted of two three-story units. Double-leaf rubble stone masonry walls, with undressed blocks and river pebbles, constituted the vertical structural elements, while timber floors, simply supported by the transverse walls, provided flexible horizontal diaphragms. The two units were covered by roofs with different truss configurations, pitches, and side-gable wall heights. An incremental, unidirectional dynamic shake-table test was performed up to near-collapse conditions of the specimen, using input ground motions representative of realistic seismic scenarios (natural and induced) for the examined region. The selected records were scaled at different amplitudes, reaching spectral accelerations close to twice those associated with a 475-years return period for the region. The experimental response of the prototype building was also simulated via nonlinear static analysis. The structure was modeled using an equivalent-frame approach with nonlinear macroelements, as implemented in the TREMURI software. The numerical results were compared with the experimental response in terms of pushover and backbone curves and lateral displacement envelopes. The consistency between numerical simulations and experimental results was also verified in terms of damage pattern and activation of damage mechanisms.

Experimental and numerical assessment of the seismic performance of a half-scale stone masonry building aggregate

The increasing demand for housing in Colombia and several neighboring countries, together with the large relative cost of the materials, has prompted city administrations to build thin reinforced concrete (RC) wall buildings with a single layer of reinforcement. Such members may experience instability and large out-of-plane deformations under seismic action. The existing models idealize the wall boundary element as an equivalent column subjected to cyclic tensile-compressive loading, and past studies have identified the maximum tensile strain applied to the member as the governing parameter which triggers the out-of-plane deformation. The influence of the wall thickness, the reinforcement eccentricity, and the loading protocol, remain largely unaddressed. This paper presents, for the first time, the initial results of the application of a beam-column model — using distributed plasticity and section fibre discretization — to study the above mentioned variables and the influence of boundary conditions, among other aspects.

Katrin Beyer

Papers

Determining crack kinematics from imaged crack patterns

Experimental and numerical assessment of the seismic performance of a half-scale stone masonry building aggregate

Numerical simulation of instability of thin reinforced concrete walls using beam elements under tension-compression