101,952 research outputs found
Government debt and economic growth: heterogeneity, asymmetries, and the role of net debt
No full textUsing data on 167 countries over 1970-2019, this study gathers new evidence about the government debt-growth relationship. We jointly address several features of the panel - foremost asymmetry, cointegration, endogeneity, country heterogeneity and cross-sectional dependence. We find that increases in per-worker debt are detrimental to the long-run dynamics of output, but our nonlinear estimates suggest that changes in government debt propagate their effects through different channels. Applying alternatively gross and net public debt as a measure of indebtedness yields different results too, as happens with the adoption of different estimators. The magnitude of the effects depends on the model specification, indicating that cross-country estimates of the debt-growth nexus require parsimonious interpretations
Ageing of pultruded glass fibre reinforced polymer composites exposed to combined environmental agents
No full textThis paper presents an experimental research on the durability of pultruded Glass Fibre Reinforced Polymer
(GFRP) composites applied in building construction. Three different matrices have been used with Eglass
fibres: isophthalic polyester, orthophthalic polyester and vinylester. The degradation of the
mechanical and aesthetical performance of the composites has been monitored through a process of
accelerated artificial ageing in a climatic chamber, simulating the combined effect of high temperature,
freeze–thaw cycles, moisture and ultraviolet (UV) radiation. Tensile, bending and interlinear shear
strength tests have been performed to measure the variation of some mechanical properties during
six months of artificial exposition. A consistent reduction of the mechanical performance has been
observed. Aesthetical appearance has been affected as well both in terms of loss of lightness and colour
variation.
The data collected have been compared to those after one year of natural ageing in external atmosphere.
It has been observed that the considered artificial ageing produces a higher degradation of some
mechanical properties if compared to the natural ageing in north Italy climate, accelerating the effects of
the environment
Ageing of pultruded GFRP composites for building constructions exposed to combined environmental agents
No full textThis paper presents an ongoing research on the durability of pultruded Glass Fiber Reinforced Polymer (GFRP) composites applied, as structural or cladding members, to building construction. Three different compositions of pultruded profiles have been tested:
Vinylester/E-glass, Isophthalic Polyester/E-glass and Orthophthalic Polyesther/E-glass. The degradation of the mechanical and aesthetical performance of the composites have been monitored through a process of artificial ageing in a climatic chamber, simulating the
combined effect of high temperature, freeze-thaw cycles, moisture (high levels of relative humidity close to the saturation grade) and UV radiation
EFFECTS OF COMBINED ENVIRONMENTAL AGENTS ON PULTRUDED GFRP COMPOSITES FOR BUILDING CONSTRUCTIONS
No full textThe aim of present research is to monitor the effect of a combination of relevant environmental agents on some mechanical and aesthetical properties of GFRP materials produced with different resins. Glass fiber pultruded profiles have been exposed in a climatic chamber to a combination of elevated and sub-zero temperatures, moisture (high levels of relative humidity close to the saturation grade) and UV radiation. Three GFRP composites have been investigated: isophthalic polyester/E-glass, orthophthalic polyester/E-glass and vinylester/E-glass. Mechanical and aesthetical performances have been collected over 24 consecutive weeks. Tensile, flexural and inter-laminar shear tests have been performed on aged specimens and un-aged materials. Moreover, change in colour and lightness has been measured during the ageing period.
The features of the materials after the artificial ageing have been compared to those of specimens exposed to natural ageing in external atmosphere of a semi-continental large city like Milan (Italy). The specimens, exposed to the natural climate, have been tested after 12 month
Do the components of government expenditure affect the long-run dynamics of private investments? A heterogeneous panel analysis with a multifactor error structure
No full textUsing data on 30 OECD countries over 1993-2019, this paper examines the ties between the components of government expenditure and the supply side of the private sector. We employ an ECM version of the novel dynamic common correlated effects estimator (DCCE) in order to account for nonstationarity, country-heterogeneity, and cross-sectional dependence. The estimates suggest that allocating public resources toward general public services and health positively affects the long-run dynamics of private investments. Conversely, rises in the expenditure on housing and social protection are associated with significant crowding-out effects
A kinematic method for shakedown and limit analysis of periodic heterogeneous media
No full textIn this Chapter the kinematic (second, Koiter's) shakedown theorem is applied to the representative volume of periodic heterogeneous media with Huber-Mises local plastic behavior. The adopted formulation of shakedown analysis is based on periodicity boundary conditions, conventional finite element modeling and penalization enforcement of plastic incompressibility. A cost-effective iterative solution procedure is discussed and computationally tested. Numerical tests and engineering applications are presented with reference to perforated plates and metal-matrix unidirectional fiber-reinforced composites
Shear response of masonry blockwork panels
No full textIn this paper, the first step of an experimental investigation is detailed dealing with the behavior of 1,20m x 1,20m blockwork masonry panels shear loaded. The results of standard diagonal compression tests have been compared with the ones of others more innovative tests with a single predetermined plane of failure parallel and perpendicular to the bed joints. The different behavior of the masonry have been discussed, especially with regards to the failure mechanisms observed and the constitutive relations experimentally obtained. The Digital Image Correlation technique has been used to detect the initiation and propagation of the damage, and to have a better insight on the crack patterns. The analysis of the results showed the non-isotropic shear response of the panels, which is related to the bond pattern and to the consequent structure. The inadequacy of standard diagonal compression tests to grasp this fundamental aspect turned out to be undeniable
Biaxial tearing properties of woven coated fabrics using digital image correlation
No full textArchitectural fabrics as construction materials can experience tearing failure caused by inevitable flaws, which greatly degrade the tensile resistance. This paper presents an experimental study which deals with the crack tearing properties of PVC coated fabrics. Effect of the initial crack length and orientation on tearing behavior were investigated with quasi-static biaxial tensile loading of cruciform specimens, setting the same load rate in warp and weft directions. The brittle failure of the PVC coated fabric had always the crack propagation along warp or weft direction. Defining the tearing residual strength (TRS) as the residual load carrying capacity of a cracked fabric, it was found that the TRS decreased nonlinearly with the increase of initial crack length, but with negligible variation of the crack orientation. Moreover, to better understand the tearing failure mechanism, the full field strain was measured by 2D digital image correlation (DIC) technique. This provided a detailed distribution of the strain components near the crack tip during biaxial loading
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