Joint Stiffness Influence on the First-Order Seismic Capacity of Dry-Joint Masonry Structures: Numerical DEM Investigations

Heritage masonry structures are often modelled as dry-jointed structures. On the one hand, it may correspond to the reality where the initial mortar was weak, missing, or has disappeared through time because of erosion and lixiviation. On the other hand, this modelling approach reduces complexity to the studied problem, both from an experimental and theoretical/numerical point of views, while being conservative. Still, for modelling purposes, in addition to the joint friction, numerical approaches require a specific elastic parameter, the dry-joint stiffness, which is often hard to estimate experimentally. This work numerically investigates the effect of the joint stiffness on the collapse of scaled-down tilting test experiments carried out on perforated dry-joint masonry shear walls. It is found that geometrical imperfections of bricks and the absence of vertical precompression load can lead to very low equivalent dry-joint stiffness, which strongly affects the results, both in terms of collapse and damage limit state (DLS) loads, with practical implications for the engineering practice

Energy loss mechanisms of rocking blocks: experimental observations

A variety of different structures experience rocking motion when subjected to dynamic actions, making rocking dynamics a fundamental problem of earthquake engineering. Rocking motion presents peculiar dynamic characteristics, such as negative stiffness during pivoting and non-smooth phenomena during impacts. Hence, modelling of the rocking problem faces significant challenges. One of the most significant is related to the energy losses that occur during impacts, commonly represented by the coefficient of restitution. Despite the numerous theoretical attempts to accurately estimate the coefficient of restitution, it is apparent that experimental observations are essential in providing a direct insight into the complex and non-smooth phenomena of rocking motion. To this end, the present work conducts an extended experimental campaign on the free-rocking motion of limestone blocks. More specifically, a total of 36 blocks are tested, corresponding to 12 different geometrical aspect ratios. The free-rocking motion is thoroughly analysed, while attention is also given to three-dimensional effects. Finally, the coefficient of restitution is experimentally quantified and compared with both previous theoretical and experimental results gathered from the literature.- (undefined

Beam dynamics studies in SPIRAL II LINAC

ACCInternational audienceThe proposed LINAG driver for the SPIRAL 2 project aims to accelerate a 5-mA D+ beam up to 20 A.MeV and 1-mA beam for q/A=1/3 up to 14.5 A.MeV. It is acontinuous wave regime (cw), designed for maximum efficiency in the transmission of intense beams. It consists of an injector (two ECR sources + a Radio Frequency Quadrupole) followed by a superconducting section based on an array of independently phased cavities. This paper presents beams dynamics studies associated to the LINAG driver. End-to-end simulations (low-energy beam lines, RFQ, medium-energy beam line, SC linac) are shown

SPIRAL II Project (electron option) - Preliminary Design Study

This document presents a Preliminary Design Study (PDS) of the electron option of the SPIRAL II project

Dynamic behaviour of drystone retaining walls: shaking table scaled-down tests

International audienceIn this paper, an experimental study aiming at understanding the seismic behaviour of dry stone retaining walls is presented. Harmonic shaking table tests have been carried out on scaled-down dry-joint retaining walls involving parallelepiped bricks. It is found that a thicker wall is more resistant and that a given retaining wall is less sensitive to higher frequencies. For those higher frequencies, the walls accept larger displacements before collapsing. The displacements start to occur from a given threshold, which depends on the wall geometry but not on the frequency of the base motion. The typical toppling failure is observed for slender wall and/or low frequency inputs. For less slender walls or higher frequency inputs, walls experience local sliding failures until the complete collapse of the system. The acceleration at failure reported during the dynamic tests have been compared to the corresponding pseudo-static resistance, enabling a conservative estimate of the seismic behaviour coefficient for pseudo-static analysis of this class of retaining walls. This novel experimental dataset is aimed to serve as a validating framework for future numerical or analytical tools in the field

Beam diagnostic overview of the SPIRAL2 RNB section

International audienceAn extension to the existing GANIL facility in Caen, France is under construction. The new SPIRAL 2 construction will be realized in two phases, for the first phase the construction started in January 2011 and will consists of the accelerator buildings with two experimental facilities S3 and Neutrons for science (NFS). The second phase is the so called production building where radioactive ions are produced through the ISOL (Isotope Separation On Line) method. The produced radioactive ion beams (RIBs) will be extracted and accelerated up to 60keV from the ion sources, after beam purification the beam will be driven in the secondary beam lines either to a new experimental facility DESIR (Decay, excitation and storage of radioactive ions) constructed during the second phase of the new installation or the RIBs will be charge breed to form multi-charged ions that will be driven to the existing GANIL facility and post accelerated in the CIME cyclotron. This overview article gives a description of the secondary beam lines, the foreseen beam diagnostics which will allow tuning and controlling the radioactive ion beams in the secondary beam lines constructed in the SPIRAL2 Phase 2

Beam dynamics studies in SPIRAL II LINAC

ACCInternational audienceThe proposed LINAG driver for the SPIRAL 2 project aims to accelerate a 5-mA D+ beam up to 20 A.MeV and 1-mA beam for q/A=1/3 up to 14.5 A.MeV. It is acontinuous wave regime (cw), designed for maximum efficiency in the transmission of intense beams. It consists of an injector (two ECR sources + a Radio Frequency Quadrupole) followed by a superconducting section based on an array of independently phased cavities. This paper presents beams dynamics studies associated to the LINAG driver. End-to-end simulations (low-energy beam lines, RFQ, medium-energy beam line, SC linac) are shown