In countries with a moderate seismic hazard, the classical methods developed for strong motion prone countries to estimate the seismic behaviour and subsequent vulnerability of existing buildings are often inadequate and not financially realistic. The main goals of this paper are to show how the modal analysis can contribute to the understanding of the seismic building response and the good relevancy of a modal model based on ambient vibrations for estimating the structural deformation under moderate earthquakes. We describe the application of an enhanced modal analysis technique (Frequency Domain Decomposition) to process ambient vibration recordings taken at the Grenoble City Hall building (France). The frequencies of ambient vibrations are compared with those of weak earthquakes recorded by the French permanent accelerometric network (RAP) that was installed to monitor the building. The frequency variations of the building under moderate earthquakes are shown to be slight (~2%) and therefore ambient vibration frequencies are relevant over the elastic domain of the building. The modal parameters extracted from ambient vibrations are then used to determine the 1D lumped-mass model in order to reproduce the inter-storey drift under weak earthquakes and to fix a 3D numerical model that could be used for strong earthquakes. The correlation coefficients between data and synthetic motion are close to 80% and 90% in horizontal directions, for the 1D and 3D modelling, respectively.

The purpose of this work is to investigate solutions for an enhanced multifiber beam element accounting for shear and torsion. Higher order interpolations functions are used to avoid any shear locking phenomena and the cross section warping kinematics is extended to non-linear behavior using advanced constitutive laws. The efficiency of the proposed modeling strategies is tested with experimental results of concrete structural elements subjected to severe loading.

International audienceThis paper presents a novel macroelement for single vertical piles in sand developed within the hypoplasticity theory, where the incremental nonlinear constitutive equations are defined in terms of generalized forces, displacements and rotations. Inspired from the macroelement for shallow foundations of Salciarini and Tamagnini [Acta Geotechnica, 4(3):163--176, 2009], the new element adopts the intergranular displacement mutuated from Niemunis and Herle [Mechanics of Cohesive--Frictional Materials, 2:279--299, 1997] to reproduce the behavior under cyclic loading. Analytical and numerical strategies are provided to calibrate the macroelement's parameters. Comparisons with experimental results show the performance of the macroelement that while being simple and computational fast is suitable for finite element calculations and engineering design