Fractional Differential Equations

https://orbilu.uni.lu/bitstream/10993/13726/1/phu-meshless.pdf

Review: Meshless methods: A review and computer implementation aspects

Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and includes means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a revision of ASCE/SEI 7-05, offers a complete update and reorganization of the wind load provisions, expanding them from one chapter into six. The Standard contains new ultimate event wind maps with corresponding reductions in load factors, so that the loads are not affected, and updates the seismic loads with new risk-targeted seismic maps. The snow, live, and atmospheric icing provisions are updated as well. In addition, the Standard includes a detailed Commentary with explanatory and supplementary information designed to assist building code committees and regulatory authorities. Standard ASCE/SEI 7 is an integral part of building codes in the United States. Many of the load provisions are substantially adopted by reference in the International Building Code and the NFPA 5000 Building Construction and Safety Code. Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice. Note: New orders are fulfilled from the second printing, which incorporates the errata to the first printing.

Minimum Design Loads for Buildings and Other Structures

Surface roughness has a huge impact on many important phenomena. The most important property of rough surfaces is the surface roughness power spectrum C(q). We present surface roughness power spectra of many surfaces of practical importance, obtained from the surface height profile measured using optical methods and the atomic force microscope. We show how the power spectrum determines the contact area between two solids. We also present applications to sealing, rubber friction and adhesion for rough surfaces, where the power spectrum enters as an important input.

/pdf/on-the-nature-of-surface-roughness-with-application-to-finn99eaoj.pdf

On the nature of surface roughness with application to contact mechanics, sealing, rubber friction and adhesion.

http://www.multiscaleconsulting.com/publications/Contact_mechanics_for_randomly_rough_surfaces.pdf

Contact mechanics for randomly rough surfaces

Under the hypothesis of a perfectly brittle phenomenon, avalanche triggering can be investigated numerically by means of Linear Elastic Fracture Mechanics (LEFM) Since, however, the real phenomenon is intrinsically dynamical, another aspect to investigate is represented by dynamic fracture propagation In this paper, we model dynamic crack propagation into a dry snow slab and we investigate the possibility to arrest the crack propagation through the presence of weak zones distributed along the extension of the snow slope Assuming that the weak layer is almost collapsed, we simulate the efficiency of artificial voids in the slab to arrest fracture propagation, into the framework of Dynamical Fracture Mechanics We put forward here a new philosophy for the use of artificial discontinuities (void) into the snowpack able to perform as crack arresters  distributed along the snow slope area: the target is to split a large avalanche slab into smaller slabs, causing small avalanches to propagate with less catastrophic effects

/pdf/numerical-study-of-fracture-arrest-on-snow-cover-4swjq2fryb.pdf

Numerical study of fracture arrest on snow cover

The results of a number of multiaxial compression tests performed on cylinders made of self-consolidating concrete (SCC), with and without steel fibers, are presented in this paper. In the experimental campaign, four "reference" confining pressures (0, 1, 3 and 10 MPa) were applied on the lateral surface of the specimens. After the first stage of loading, when a hydraulic stress was applied to the cylinders, and progressively increased up to a pre-established confining pressure, a longitudinal compressive load was applied as well, up to concrete failure by crushing. The stress-strain relationships of different SCCs, measured with the aid of local transducers, show the increase of concrete strength, and of the corresponding strain, with the confining pressure. However, compared to the values measured in ordinary (vibrated) concrete, the strains at the peak stress are higher in self-consolidating concrete. In addition, the test results give indications on how to modify the stress-strain relationships formulated so far for ordinary concrete, in the case of SCC subjected to multiaxial compression. To this end, by using the Colonnetti's theory of "elastic coactions", a new formulation of the well-known Sargin's relationship is proposed in the paper.

Stress-strain relationship for steel fiber-reinforced self-consolidating concrete under multiaxial compression

In 2003, an ancient Greek Gymnasium was found in Naples, Italy, during the excavation for a new underground station. The artifacts had to be cut into blocks to be temporarily removed from the site and then reallocated after the end of the work. In this article, after describing the results of the chemical analyses and mechanical tests performed on the masonry specimens extracted from the gymnasium, a model to describe the cutting process is proposed. By means of this model, the optimal relations between kinetic, static, and energy quantities have been found, which can improve the regularity of the cutting process, permitting to minimize damage on bricks and mortar. A key physical quantity — called the “cutting strength” — is introduced and calculated through back analysis, starting from the experimental data recorded on site. The values of the cutting strength can be related to the results of the compression tests by means of a scaling law obtained through a fractal approach. Finally, a model for the wear...

Optimization of Cutting Process for Ancient Masonry: The Greek Gymnasium in Naples

Triggering of dry snow slab avalanches and a new concept of active defence

The performance of fiber-reinforced self-compacting concrete (FR-SCC) under compression are investigated. In general, its ductility is comparable with that of normal vibrated concrete (NC) and self-compacting concrete (SCC) in the presence of confinement. This aspect can be shown by analyzing the mechanical behavior of cylindrical specimens under uniaxial and triaxial compression tests. The post-peak response is defined in terms of F(w), which is a non-dimensional function that relates the inelastic displacement w and the relative stress applied during softening. In the case of SCC, the presence of fibers increases the value of F(w) corresponding to the value of w. Starting from this performance, the mechanical behavior of a low-carbon footprint SCC is also considered. The results of this study indicate that the idea of introducing a new generation of concrete mixtures, capable of maintaining high values of F(w) with a reduced amount of cement, is possible.

Bernardino Chiaia

Papers

Numerical study of fracture arrest on snow cover

Stress-strain relationship for steel fiber-reinforced self-consolidating concrete under multiaxial compression

Optimization of Cutting Process for Ancient Masonry: The Greek Gymnasium in Naples

Triggering of dry snow slab avalanches and a new concept of active defence

Sustainability and mechanical performances of fiber-reinforced self-compacting concrete (FR-SCC)