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

TThe supports of out-of-plane loaded unreinforced masonry walls in buildings are subjected to a motion that is filtered and amplified by the building structure and, in some cases, can be significantly different from the ground motion. Moreover, because these walls span one or several storeys, their top and bottom supports are subjected to motions that differ in phase and amplitude. In state-of-the-art assessment procedures for the out-of-plane stability of masonry walls any effect of a relative support motion is neglected. The objective of this paper is to study the effect of the relative support motion on the response of out-of-plane loaded vertically-spanning unreinforced masonry walls. The acceleration capacity of the walls is investigated by means of a discrete element model representative of different wall configurations. A set of ground motions covering a wide range of peak ground acceleration and peak ground displacement is used as input to the simulations. The relative motion between the wall supports is included in the model in a systematic way: firstly, through a motion that is non-synchronous but of equal amplitude; secondly, through a motion that is synchronous but of different amplitude. The effect of the relative support motion is studied on different wall configurations where the elastic modulus of masonry, the wall height-to-thickness ratio, the wall effective thickness and the overburden at the top wall are varied. The study shows that, because of the relative support motion, the acceleration capacity of the walls can drop by 20% and, in the cases where the overburden is high, by more than 50%.

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Quantifying the out-of-plane response of unreinforced masonry walls subjected to relative support motion

Dynamic testing of a four-storey building with reinforced concrete and unreinforced masonry wall: Data set

Earthquake loads can induce out-of-plane deformations in thin reinforced concrete (RC) walls that may lead to member out-of-plane failure or cause a premature in-plane collapse. Such instability phenomena have been observed after the recent earthquakes in Chile (2010) and New Zealand (2011). Walls with single layer of vertical reinforcement are more vulnerable to instability issues than the typical two-layer design. However, high material costs and the increasing demand of housing for low income population in Latin America (namely Colombia) over the last few years has prompted city administrations to build medium to high rise RC buildings using walls with single layers of vertical reinforcement. The results of a recent experimental campaign on thin RC walls performed by the authors confirmed the relevance of this topic, underlining the need for further investigations to study the effect of different parameters on the out-of-plane response, such as loading history, wall thickness, and longitudinal reinforcement ratio. This effort is currently being carried out by idealizing the wall boundary region—which primarily triggers the instability mechanism—as an equivalent column axially loaded in cyclic tension and compression, as commonly hypothesized by the existing phenomenological models. This paper presents the first results of a numerical study consisting of the application of a beam-column model.

Out-of-plane behaviour of reinforced concrete members with single reinforcement layer subjected to cyclic axial loading: beam-column element simulation

For a shake table test on a four-storey structure with both unreinforced hollow-core brick masonry (URM) walls and reinforced concrete (RC) walls, the test unit had to be constructed at half-scale. While past experience showed that testing RC structural elements at reduced scale leads to similar results as full-scale tests, a literature review on tests of scaled masonry revealed that scaling of masonry was more challenging. For instance, several researchers reported that the scaled masonry was stronger but less stiff than the full-scale masonry. However, previous work concentrated on the scaling of solid clay material and not all conclusions can be translated directly to masonry with modern hollow-core clay bricks. As a preparation to the shake table test, an extensive test program on full- and half-scale hollow-core brick masonry was conducted. This paper presents results of material tests that were conducted to develop a half-scale masonry that matched the full-scale masonry best. Our results are compared to previous investigations and the differences between scaling of masonry with solid and hollow-core bricks are discussed.

Scaling unreinforced masonry structures with hollow-core clay bricks for laboratory testing

In Switzerland many new residential buildings are constructed as unreinforced masonry (URM) structures or as mixed structures where URM walls are coupled with reinforced concrete (RC) walls by RC slabs. At present the boundary conditions of URM walls subjected to out-of-plane accelerations are still not well quantified. In the framework of a large research activity on RC-URM wall structures a shake-table test on a four-storey mixed structure was performed. The test specimen, which was built at half-scale, was designed in such a way to allow the collection of data on the effect of boundary conditions provided by the RC slabs and adjacent RC walls on the out-of-plane seismic behaviour of URM piers. This paper presents observations on the out-of-plane behaviour of the URM walls from the shake-table test and draws conclusions for the boundary conditions to be applied in numerical studies on URM piers in mixed RC-URM wall structures.

Katrin Beyer

Papers

Quantifying the out-of-plane response of unreinforced masonry walls subjected to relative support motion

Dynamic testing of a four-storey building with reinforced concrete and unreinforced masonry wall: Data set

Out-of-plane behaviour of reinforced concrete members with single reinforcement layer subjected to cyclic axial loading: beam-column element simulation

Scaling unreinforced masonry structures with hollow-core clay bricks for laboratory testing

Observations on out-of-plane behaviour of URM walls in buildings with RC slabs