Non-Destructive Assessment of the Adhesion at the Interface Between FRCM Reinforcements and Masonry Substrates by Non-Linear Ultrasonic Technique

The strong diffusion of Fiber Reinforced Cementitious Matrix (FRCM) composites for the reinforcement of historic masonry constructions requires suitable experimental techniques for assessing possible defects in the adhesion between FRCM and masonry, and between FRCM layers. To this aim, in this paper, an innovative nonlinear ultrasonic approach based on the Side-band Peak Count (SPC) technique is proposed. This approach is discussed and validated through experimental tests made on tuff substrates reinforced with FRCM mortars embedding a basalt fibers grid and having known artificial defects at the adhesion between tuff and FRCM as well as in the fiber gri

Experimental and Numerical Analysis of a FRCM Reinforced Parabolic Tuff Barrel Vault

An experimental and numerical analysis of the structural behaviour of a barrel tuff masonry vault strengthened by a Fiber Reinforced Cementitious Matrix (FRCM) reinforcement system it is proposed. The geometry and the materials of the vault are representative of some historical constructions in Apulia (Italy). The vault, under the action of the self-weight and of a distributed load representative of the infill, has been first damaged by differential settlement of abutments, and then repaired and strengthened by FRCM composites. Finally the structure has been subjected to a increasing concentrated load on the extrados. A 3D heterogeneous FE Abaqus numerical model describing the above mentioned experimental conditions is carried out in order to reproduce the response of the FRCM reinforced vault. The obtained experimental and numerical results allows for discussing the structural behaviour of the reinforced vault, and then the effectiveness of the employed reinforcement

Experimental Data for the Calibration of a Non-Linear Numerical Model for Describing the Response of Masonry Constructions under Cyclic Loading

One of the crucial issues in the still open problem of seismic analyses of masonry constructions is the study of the structural capacity for cyclic loadings; the difficulties are even more pronounced when constructions embedding curved elements like arches, vaults and domes have to be studied. In order to develop effective nonlinear numerical models, the latter have to be capable of representing the relevant aspects of the experimental behavior, and the mechanical parameters of the model have to be carefully calibrated with reference to suitable experimental test results. In this paper the outcomes of experimental tests on a tuff masonry arch under cyclic loading are proposed and discussed, along with the results of experimental tests on the masonry materials (blocks and mortar) aimed at determining the compressive, flexural and shear behavior

Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere

Saturn Atmospheric Structure and Dynamics

2 Saturn inhabits a dynamical regime of rapidly rotating, internally heated atmospheres similar to Jupiter. Zonal winds have remained fairly steady since the time of Voyager except in the equatorial zone and slightly stronger winds occur at deeper levels. Eddies supply energy to the jets at a rate somewhat less than on Jupiter and mix potential vorticity near westward jets. Convective clouds exist preferentially in cyclonic shear regions as on Jupiter but also near jets, including major outbreaks near 35°S associated with Saturn electrostatic discharges, and in sporadic giant equatorial storms perhaps generated from frequent events at depth. The implied meridional circulation at and below the visible cloud tops consists of upwelling (downwelling) at cyclonic (anti-cyclonic) shear latitudes. Thermal winds decay upward above the clouds, implying a reversal of the circulation there. Warm-core vortices with associated cyclonic circulations exist at both poles, including surrounding thick high clouds at the south pole. Disequilibrium gas concentrations in the tropical upper troposphere imply rising motion there. The radiative-convective boundary and tropopause occur at higher pressure in the southern (summer) hemisphere due to greater penetration of solar heating there. A temperature “knee ” of warm air below the tropopause, perhaps due to haze heating, is stronger in the summer hemisphere as well. Saturn’s south polar stratosphere is warmer than predicted by radiative models and enhanced in ethane, suggesting subsidence-driven adiabatic warming there. Recent modeling advances suggest that shallow weather laye

SPC non-linear ultrasonic technique for detecting adhesion defects in FRCM reinforcements for masonry constructions

Nowadays Fiber Reinforced Cementitious Matrix (FRCM) composites are considered as a primary strengthening technique for reinforced concrete and masonry constructions, especially for historic buildings. Historic structures exhibit a pronounced seismic vulnerability, entailing the risk of losing important parts of the world's cultural heritage. A vast literature is available on issues like the interactions, the adhesion, and the delamination strength between FRCM composites and masonry. However, much fewer studies concern the detection of possible defects in the adhesion between FRCM and masonry, formed during the application of the reinforcement or during the service life of the construction, for example, from exceptional loads like earthquake, fire, etc. These defects can strongly undermine the effectiveness of the strengthening intervention, and thus the structural safety of the reinforced construction. Here, an innovative nonlinear ultrasonic technique called Side-band Peak Count (SPC) is proposed for detecting defects in the adhesion between FRCM composite layers and masonry substrates. The SPC technique reprocesses the results of the ultrasonic guided wave tests by relating the level of the non-linearity of the ultrasonic response due to the damage, to the appearance of additional secondary components in the spectrum of the received signal. Experiments are conducted on masonry tuff specimens reinforced with FRCM mortars and basalt fibers grid embedment. Specimens with known artificial defects are tested. Defects are fabricated both at the FRCM-tuff interface and within the FRCM layer, i.e., at the interface mortar-reinforcement fiber grid. The effectiveness of the proposed approach is investigated and discussed. © 2022 SPIEImmediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A model for the hysteretic behavior of shape memory alloys under repeated loading cycles

We propose a simple model for the hysteretic behavior of shape memory alloys under repeated loading cycles. Our basic assumption is a two-well free energy density that varies with the loading history due to the modifications of the material properties during the phase transition processes. The model reproduces important experimental observations ranging from multi-plateaux transition paths and the variations of the stress-strain hysteresis loop with the loading history, to internal loops for incomplete phase transitions and return point memory property

Whole Earth Telescope observations of BPM 37093: a seismological test of crystallization theory in white dwarfs

BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 MO) to theoretically crystallize while still inside the ZZ Ceti instability strip (Teff ~ 12 000 K). As a consequence, this star represents our first opportunity to test crystallization theory directly. If the core is substantially crystallized, then the inner boundary for each pulsation mode will be located at the top of the solid core rather than at the center of the star, affecting mainly the average period spacing. This is distinct from the “mode trapping” caused by the stratified surface layers, which modifies the pulsation periods more selectively. In this paper we report on Whole Earth Telescope observations of BPM 37093 obtained in 1998 and 1999. Based on a simple analysis of the average period spacing we conclude that a large fraction of the total stellar mass is likely to be crystallized