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

Keywords: Unreinforced masonry, spandrel, numerical study, simplified micro model Reference EPFL-CONF-181571 Record created on 2012-10-01, modified on 2016-08-09

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Numerical analysis of Masonry Spandrels with Shallow Arches

Code design of Unreinforced Masonry (URM) buildings is based on elastic analysis, which requires as input parameter the effective stiffness of URM walls. Current approaches estimate the effective stiffness as fixed ratio of the gross sectional stiffness but comparisons with experimental results have shown that this does not yield satisfactory predictions. In this paper, a recently developed analytical model for the force-displacement response of URM walls is used to investigate the effective stiffness. First, the key features of this model are summarised. In further course, the model is used to predict the effective stiffness of full-scale tests on modern unreinforced clay brick masonry walls and the results are compared to the provisions of Eurocode 8. Concluding, the model is used to investigate the sensitivity of the effec-tive stiffness to the wall geometry and axial loading.

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Effective stiffness of unreinforced brick masonry walls

Examining the results of a large set of quasi-static cyclic tests on unreinforced masonry (URM) walls showed that the drift capacity of URM walls reduces with increasing wall size. Such a size effect is of concern since most wall tests were carried out on test specimens with heights much smaller than actual story heights. In modern URM buildings the wall height is, however, often equal to the story height. Current drift capacity models implemented in structural design codes do not account for this size effect, thereby they tend to overestimate the drift capacity of URM walls with heights equal to the story height. The objective of this paper is to review existing evidence for size effects on the drift capacity of URM walls and discuss possible reasons for this effect. The paper starts with a general review of size effects in quasi-brittle structures and a review on existing numerical and experimental evidence for size effects in the seismic response of URM walls. It puts forward the notion that for walls failing in flexure the size effect is largely caused by the confining effect of the foundation, which diminishes with increasing height, while for walls failing in shear the size effect stems mainly from the post-peak response and the formation of a crushing band of the height of a brick. It concludes with an outlook on future research needs for quantifying the size effect on the drift capacity of URM walls in flexure and shear.

Size effects in drift capacities of URM walls

Fibre-reinforced polymers (FRP) strengthening can be applied to decrease the seismic vulnerability of existing masonry buildings, both with regard to in-plane and out-of-plane failure mechanisms. Experimentally, the impact of strengthening solutions has been thoroughly studied. There are, however, few efficient and reliable numerical modeling approaches that can accurately capture the effect of such strengthening on the seismic response of the masonry building. Therefore, we herein develop and validate a modeling approach to capture the effect of FRP strengthening on the behaviour of masonry walls. To model this effect, we use a recently developed macro-element, which can capture both in-plane and out-of-plane failure modes. In the macro-element, the intervention is modelled by adding ﬁbres representing the longitudinal FRP strips to the section model. These fibres were modelled as linear elastic in tension up to the failure with a zero compressive strength. Transversal FRP strips effect the shear strength, and in the macro-element, this is accounted for by increasing the cohesion in the equation for the shear strength. To validate the model, we also compare the numerical simulations with existing experimental results obtained from the literature. Overall, the proposed modeling approach accurately predicts the in-plane and out-of-plane response, implying that equivalent frame models can predict the response of masonry buildings with FRP-strengthened walls. To conclude, the models described in this paper can be used for a time-efficient assessment. Moreover, it can help in selecting the optimal strengthening approach for future retrofitting. This aspect is especially important for the cultural heritage structures, where excessive retrofitting should be avoided.

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Eqivalent frame models for frp-strengthened masonry buildings

Keywords: Reinforced concrete slabs ; Cyclic behaviour ; Slab-column connection Reference EPFL-CONF-224466 Record created on 2017-01-17, modified on 2017-01-17

Katrin Beyer

Papers

Numerical analysis of Masonry Spandrels with Shallow Arches

Effective stiffness of unreinforced brick masonry walls

Size effects in drift capacities of URM walls

Eqivalent frame models for frp-strengthened masonry buildings

Analytical model for slab-column connections subjected to cyclically increasing drifts