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

The Unreinforced Wall (URM) elements that are most susceptible to out-of-plane failure are wall elements of the upper storeys where the accelerations are largest. In modern URM buildings with reinforced concrete slabs, the out-of-plane mechanism involves typically a storey-high wall element, which is subjected at its base and top to the accelerations of the corresponding floor slabs. The accelera-tion time histories of the two slabs differ as a result of the deformability of the in-plane loaded walls and their rigid body rotations. Existing studies on the out-of-plane response of URM walls analysed walls that were subjected to the same input motion at the top and bottom of the wall. In few studies, the motion was modified by a spring modelling the in-plane flexibility of the slabs. This article investigates how the response of walls subjected to different accelerations at the top and bottom differ from the response of walls that are subjected to the same, mean acceleration at the top and bottom. The topic is investigated by means of a parametric study using discrete element modelling and by means of simple mechanical models using rigid body mechanisms. The article concludes that in particular the relative displacement between the top and base of the wall contributes to the reduced out-of-plane resistance. The non-constant force distribution over the wall height has only a lesser influence. The paper concludes with recommendations for future research.

Effect of static and kinematic boundary conditions on the out-of-plane response of brick masonry walls

Despite the fact that displacement-based methods are now frequently applied when assessing the seismic performance of unreinforced masonry (URM) structures, the displacement capacity of in-plane loaded URM piers is still estimated from empirical rather than mechanical relationships. One idea for estimating a pier’s force-displacement curve including its displacement capacity that has been put forward in the past is based on the double integration of the curvature profile. The curvature is derived assuming a bilinear stress-strain relationship in the compression domain and neglecting the tensile strength of the masonry. We tested several identical URM piers under different constant axial load and shear span ratios while applying quasi-static horizontal cyclic in-plane loading. During testing, we tracked with a set of cameras the displacement of four LEDs on each full brick of the masonry piers. Therefore, we were able to determine the local deformations, e.g. average strains in the bricks and deformations of the joints. In this paper we will present experimentally determined local and global deformation quantities of one pier dominated by flexural deformations and compare these to the estimates from the analytical model. Differences between model and experiment will be discussed and first estimates of performance limits describing local deformations will be proposed.

Flexural deformations of URM piers: Comparison of analytical models with experiments

Although mixed reinforced concrete (RC) - unreinforced masonry (URM) wall structures are often used, experimental and numerical studies on their seismic behaviour are scarce. Previous studies pointed out that the obtained results from numerical simulations are strongly dependant on the modelling assumptions. Two quasi-static cyclic tests on mixed RC-URM wall structures were recently completed at EPFL: the tests were carried out using a novel set up capable of measuring the reaction forces (axial force, bending moment, shear force) at the base of the URM wall and allowing to back-calculate the reaction forces at the base of the RC wall. A further objective of the research programme is to provide general guidelines for the analysis of mixed RC-URM wall structures using different numerical approaches. In the paper, a micro-modelling / shell element approach was adopted to study the seismic behaviour of such mixed structures; the numerical results – in terms of reaction forces, inter-storey drifts and deformed shapes – are discussed and compared against the obtained experimental results.

Seismic behaviour of mixed RC-URM wall structures: comparison between numerical results and experimental evidence

Keywords: Unreinforced masonry ; Force-based beam element ; Shear-flexure interaction Reference EPFL-CONF-224472 Record created on 2017-01-17, modified on 2017-01-18

Force-based finite element for modelling the cyclic behaviour of unreinforced masonry piers

In many countries reinforced concrete (RC) flat slabs supported on columns is one of the most commonly used structural systems for office and industrial buildings. To increase the lateral stiffness and strength of the structure, RC walls are typically added and carry the largest portion of the horizontal loads generated during earthquakes. While the slab-column system is typically not relevant with regard to the lateral stiffness and strength of the structure, each slab-column connection has to have the capacity to follow the seismically induced lateral displacements of the building while maintaining its capacity to transfer vertical loads from the slab to the columns. If this is not the case, brittle punching failure of the slab occurs and the deformation capacity of the entire building is limited by the deformation capacity of the slab-column connection. This article presents an analytical approach for predicting the moment resistance of all mechanisms that contribute to the strength of the slab-column connection when subjected to earthquake-induced drifts. The approach is based on the Critical Shear Crack Theory (CSCT). The performance of the model is verified comparing the analytical predictions with experiments from the literature. The influence of gravity induced loads on the flexural behaviour of slab-column connections under seismic loading as well as the contribution of the various resistance-providing mechanisms for increasing drifts are discussed.

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Katrin Beyer

Papers

Effect of static and kinematic boundary conditions on the out-of-plane response of brick masonry walls

Flexural deformations of URM piers: Comparison of analytical models with experiments

Seismic behaviour of mixed RC-URM wall structures: comparison between numerical results and experimental evidence

Force-based finite element for modelling the cyclic behaviour of unreinforced masonry piers

Lateral force resisting mechanisms in slab-column connections: An analytical approach