Nonlinear simulation of masonry vaults under earthquake loading

Masonry vaults are present in a large number of historical structures and often used as floor-ing and roofing systems in monumental palaces and religious buildings, typically incorporat-ing no backfill. Many of these structures are located in seismic regions and have been shownto be particularly vulnerable during recent earthquakes, with a need for accurate modelling to avoid future losses. Masonry vaults are often analysed using limit analysis procedures un-der the hypotheses of no-tension material and absence of sliding along the masonry joints.However, this method can be inaccurate for barrel vaults found in buildings, which are typi-cally slender with no backfill. In this case, the masonry tensile strength and the progressive damage propagation play an important role in the nonlinear behaviour and ultimate strength of the vault. In this study, a detailed mesoscale finite element mesoscale approach is used to model slender unreinforced barrel vaults subjected to cyclic quasi-static and dynamic load-ing. According to this approach, 3D solid elements connected by 2D damage-plasticity inter-faces are used to represent the arrangement of bricks and mortar present in the masonry. Theproposed numerical description is first validated against the results from physical tests on a barrel vault under quasi-static cyclic loading. Subsequently, the shear response of a prototype vault is analysed by performing nonlinear simulations under prescribed horizontal displace-ments at the supports, considering also the influence of previous damage induced by earth-quakes with different magnitudes

Nonlinear static analysis of an asymmetric unreinforced masonry building using macro-element modelling approach

Past seismic events showed that irregular structures are subjected to more damage compared to the regular ones. Although seismic codes prohibit or discourage irregularities by imposing certain penalties, the design of these type of structures can be inevitable due to functional and architectural concerns. In fact, structures designed as regular configuration can also present behavior induced by torsional effects due to progressive damage and irregular load distribution after experiencing seismic events. The present paper focuses on the seismic performance of a half-scale two story unreinforced masonry building with asymmetric structural configuration. Structural irregularity both in plan and as openings in elevation was considered. Nonlinear static analyses were performed using macro-element modeling approach in two different software available for masonry structures, namely 3DMacro and TREMURI. Results obtained from the two software were compared in terms of capacity and damage patterns. It was seen a considerable difference in capacity curves. Additionally, several sensitivity analyses were carried out and sensitivity of the model to certain parameters, such as tensile strength, friction coefficient, and shear strength, was assessed.PUMA - Experimental and Numerical Pushover Analysis of Masonry Buildings - PTDC/ECI-EGC/29010/201

The need for conservation management in European 19th century urban housing

The prediction of the dynamic response of Unreinforced Masonry Structures (URMS) is a very complex task, since it is governed by material degradation and cyclic hysteric behaviour. Procedures based on nonlinear static analyses have been proposed for the seismic assessment of URMS, without properly considering hysteretic energy dissipation during the dynamic response. Even though dynamic nonlinear analyses provide satisfactory simulations of the seismic response, its application requires considerable computational effort and high user expertise for the accurate definition of the material properties, making it unsuitable for practical applications. However, simplified macro-element strategies, capable of simulating in-plane and outof-plane nonlinear responses, could represent a satisfactory engineering solution in the dynamic context. In this study the nonlinear static and dynamic in-plane behaviour of URMS was assessed by means of plane discrete models. The preliminary numerical investigation evidenced the need to define suitable hysteric constitutive laws for reliable nonlinear dynamic analyses of URMS.(undefined

High rate, fast timing Glass RPC for the high {\eta} CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to $6.10^{34} cm^{-2} s^{-1}$ . The region of the forward muon spectrometer ($|{\eta}| > 1.6$) is not equipped with RPC stations. The increase of the expected particles rate up to $2 kHz/cm^{2}$ (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provides a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity (LR) glass is proposed to equip at least the two most far away of the four high ${\eta}$ muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux is presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.Comment: 14 pages, 11 figures, Conference proceeding for the 2016 Resistive Plate Chambers and Related Detector

The application of cortical layer markers in the evaluation of cortical dysplasias in epilepsy

The diagnostic criteria for focal cortical dysplasia type I (FCD I) remain to be well and consistently defined. Cortical layer-specific markers (CLM) provide a potential tool for the objective assessment of any dyslamination. We studied expression patterns of recognised CLM using immunohistochemistry for N200, ER81, Otx1, Map1b (subsets of V/VI projection neurones), Pax6, Tbr1, Tbr2 (differentially expressed in cortical neurones from intermediate progenitor cells), Cux 1 (outer cortical layers) and MASH1 (ventricular zone progenitors). Dysplasia subtypes included FCD I and II, dysplasias adjacent to hippocampal sclerosis (HS) or dysembryoplastic neuroepithelial tumours (DNTs); all were compared to neonatal and adult controls. Laminar expression patterns in normal cortex were observed with Tbr1, Map1b, N200 and Otx1. FCDI cases in younger patients were characterised by abnormal expression in layer II for Tbr1 and Otx1. FCDII showed distinct labelling of balloon cells (Pax6, ER81 and Otx1) and dysmorphic neurones (Tbr 1, N200 and Map1b) supporting origins from radial glia and intermediate progenitor cells, respectively. In temporal lobe sclerosis cases with dysplasia adjacent to HS, Tbr1 and Map1b highlighted abnormal orientation of neurones in layer II. Dyslamination was not confirmed in the perilesional cortex of DNT with CLM. Finally, immature cell types (Otx1, Pax6 and Tbr2) were noted in varied pathologies. One possibility is activation of progenitor cell populations which could contribute to the pathophysiology of these lesions

A 3D discrete macro-element for modelling the out-of-plane behaviour of infilled frame structures

A high percentage of new and existing framed buildings (either in concrete or steel) are built with unreinforced masonry infilled walls leading to the structural typology known as Infilled Frame Structures (IFS). In these structures, the masonry infills are built after the construction of the main structural frame and are considered as non-structural elements. For this reason, the contribution of unreinforced masonry infills is generally neglected, in the structural analysis of IFS, leading to inaccuracies in the prediction of their seismic nonlinear response. In this paper a three-dimensional discrete element method, able to simulate the complex interactions, in-plane and out-of-plane, in IFS is presented. In the proposed approach, the infill wall is modelled by means of an original spatial discrete element previously introduced for the analysis of UnReinforced Masonry (URM) Structures. Since the attention is focused on the behaviour of the masonry infills, the frame elements have been assumed as linear elastic beams interacting with the macro-elements through plane nonlinear interfaces. In the paper, after a theoretical description of the proposed approach, several experimental–numerical comparisons are provided for investigating the out-plane behaviour of infilled frames. The achieved results demonstrate the accuracy and the significant potential of using the proposed approach for the non-linear analysis of IFS under different loading conditions.(undefined)info:eu-repo/semantics/publishedVersio

A macroscale modelling approach for nonlinear analysis of masonry arch bridges

Masonry arches represent the most important structural components of masonry arch bridges. Their response is strongly affected by material nonlinearity which is associated with the masonry texture. For this reason, the use of mesoscale models, where units and mortar joints are individually represented, enables accurate response predictions under different loading conditions. However, these detailed models can be very computationally demanding and unsuitable for practical assessments of large structures. In this regard, the use of macro-models, based on simplified homogenised continuum representations for masonry, can be preferable as it leads to a drastic reduction of the computational burden. On the other hand, the latter modelling approach requires accurate calibration of the model parameters to correctly allow for masonry bond. In the present paper, a simplified macro-modelling strategy, particularly suitable for nonlinear analysis of multi-ring brick-masonry arches, is proposed and validated. A numerical calibration procedure, based on genetic algorithms, is used to evaluate the macro-model parameters from the results of meso-scale “virtual” tests. The proposed macroscale description and the calibration procedure are applied to simulate the nonlinear behaviour up to collapse of two multi-ring arches previously tested in laboratory and then to predict the response of masonry arches interacting with backfill material. The numerical results confirm the ability of the proposed modelling strategy for masonry arches to predict the actual nonlinear response and complex failure mechanisms, also induced by ring separation, with a reduced computational cost compared to detailed mesoscale models

A two-level macroscale continuum description with embedded discontinuities for nonlinear analysis of brick/block masonry

A great proportion of the existing architectural heritage, including historical and monumental constructions, is made of brick/block masonry. This material shows a strong anisotropic behaviour resulting from the specific arrangement of units and mortar joints, which renders the accurate imulation of the masonry response a complex task. In general, mesoscale modelling approaches provide realistic predictions due to the explicit representation of the masonry bond characteristics. However, these detailed models are very computationally demanding and mostly unsuitable for practical assessment of large structures. Macroscale models are more efficient, but they require complex calibration procedures to evaluate model material parameters. This paper presents an advanced continuum macroscale model based on a two-scale nonlinear description for masonry material which requires only simple calibration at structural scale. A continuum strain field is considered at the macroscale level, while a 3D distribution of embedded internal layers allows for the anisotropic mesoscale features at the local level. A damage-plasticity constitutive model is employed to mechanically characterise each internal layer using different material properties along the two main directions on the plane of the masonry panel and along its thickness. The accuracy of the proposed acroscale model is assessed considering the response of structural walls previously tested under in-plane and out-of-plane loading and modelled using the more refined mesoscale strategy. The results achieved confirm the significant potential and the ability of the proposed macroscale description for brick/block masonry to provide accurate and efficient response predictions under different monotonic and cyclic loading conditions