Local structural effects in fiber-reinforced polymer web-core sandwich structures

Glass fiber-reinforced polymer (GFRP) pultruded decks and sandwich panels currently represent two of the most extensive applications of FRP materials for load-bearing structural components in the bridge and building domains. Based on the state of the art, the global structural behavior of both systems has been fairly well investigated. Nonetheless, local effects governing in most cases the global behavior have been barely addressed. Selected local structural effects relevant to the global structural performance of pultruded GFRP bridge decks and GFRP-foam web-core sandwich structures are therefore investigated in this research. The effect of the core geometry of pultruded GFRP decks on the systemâs behavior in its transverse-to-pultrusion direction was experimentally investigated. The experimental work conducted on two deck designs with trapezoidal- and triangular-cell cross sections showed that the transverse structural performance depends on the cell geometry. Furthermore, the systemsâ transverse bending and in-plane shear stiffness were evaluated and the results indicated that a triangular core causes a more pronounced bi-directional behavior of the deck when it is subjected to concentrated loads. The local behavior of the web-flange junctions (WFJs) of the pultruded deck with trapezoidal cells was experimentally investigated regarding energy dissipation capacity and recovery subsequent to unloading. The experimental responses reported for two junction types with similar geometry and fiber architecture but different initial imperfections demonstrated that dissimilar imperfections could significantly affect WFJ behavior and change it from brittle to ductile. The time-dependent recovery and energy dissipation mechanisms of the WFJs exhibiting a ductile response were evaluated; the viscoelastic effects were found to be small in both cases. The rotational behavior of all WFJ types present in the trapezoidal-core deck was characterized. An experimental procedure based on three-point bending and cantilever experiments conducted on the web elements was developed and used for this purpose. The rotational stiffness, strength and failure modes of the WFJs differed depending on the web type, location of the WFJ within the deck profile, existing initial imperfections and direction of the applied bending moment. Numerical simulations of the full-scale deck were performed to demonstrate the validity of the experimental moment-rotation (M-Ï) relationships and simplified M-Ï curves provided. The effects of creep on the load-bearing behavior of GFRP-foam web-core sandwich structures were investigated. A study of the creep behavior of polyurethane (PUR) foams was conducted and showed that in order to assess the long-term structural performance of the sandwich system, the foam anisotropy, density and loading type should be considered. The creep behavior of web-core sandwich panels, and specifically the structural aspects affected by the web-core interaction, were analyzed using the GFRP-PUR sandwich roof of the Novartis Campus Main Gate Building as case study and currently available design guidelines. The resulting sandwich designs depended on the applied design recommendations. Finally, provisions for the cross-sectional design of the hybrid web-core were proposed

Characterization of rotational behavior of web-flange junctions of pultruded GFRP bridge decks

The rotational behavior of the web-flange junctions (WFJs) of a pultruded GFRP bridge deck system was investigated. The rotational response of three WFJ types was characterized. An experimental procedure based on three-point bending and cantilever experiments conducted on the web elements and simple analytical models was used. The WFJs generally exhibited non-rigid and nonlinear behavior. The overall moment-rotation relationships, rotational stiffness, strength and failure modes differed depending on the web type, the location of the WFJ within the deck profile, the initial imperfections and the direction of the bending moment applied. Simplified expressions to model the WFJ rotational behavior were derived. The validity of the experimental and idealized rotational responses was assessed by means of numerical simulations of full-scale experiments conducted on the GFRP deck

Performance in Transverse Direction of Fiber‐Reinforced Polymer Bridge Decks

Pultruded glass fiber‐reinforced polymer (GFRP) bridge decks distribute punctual vehicular loads to the underlying superstructure and can also act as the upper chord of hybrid main girders. The deck’s structural performance in both cases is influenced by its transverse behavior. The static bending behavior in the transverse‐to‐pultrusion direction of two GFRP bridge deck systems with trapezoidal (DS) and triangular (AS) cell cross‐sectional geometry was experimentally studied. Different load transfer mechanisms were found in DS (frame‐dominated) and AS (truss‐governed) depending on the cell geometry. The DS deck exhibited a lower apparent bending stiffness and degree of composite action between the face sheets than the AS deck, which was attributed to the lower transverse in‐plane shear stiffness provided by the trapezoidal core than by the triangular core. The system in‐plane shear moduli were estimated from the experimental deflection results

Evidence for a black hole in the historical X-ray transient A 1524-61 (=KY TrA)

We present VLT spectroscopy, high-resolution imaging and time-resolved photometry of KY TrA, the optical counterpart to the X-ray binary A 1524-61. We perform a refined astrometry of the field, yielding improved coordinates for KY TrA and the field star interloper of similar optical brightness that we locate $0.64 \pm 0.04$ arcsec SE. From the spectroscopy, we refine the radial velocity semi-amplitude of the donor star to $K_2 = 501 \pm 52$ km s$^{-1}$ by employing the correlation between this parameter and the full-width at half-maximum of the H$\alpha$ emission line. The $r$-band light curve shows an ellipsoidal-like modulation with a likely orbital period of $0.26 \pm 0.01$ d ($6.24 \pm 0.24$ h). These numbers imply a mass function $f(M_1) = 3.2 \pm 1.0$ M$_\odot$. The KY TrA de-reddened quiescent colour $(r-i)_0 = 0.27 \pm 0.08$ is consistent with a donor star of spectral type K2 or later, in case of significant accretion disc light contribution to the optical continuum. The colour allows us to place a very conservative upper limit on the companion star mass, $M_2 \leq 0.94$ M$_\odot$, and, in turn, on the binary mass ratio, $q = M_2/M_1 \leq 0.31$. By exploiting the correlation between the binary inclination and the depth of the H$\alpha$ line trough, we establish $i = 57 \pm 13$ deg. All these values lead to a compact object and donor mass of $M_1 = 5.8^{+3.0}_{-2.4}$ M$_\odot$ and $M_2 = 0.5 \pm 0.3$ M$_\odot$, respectively, thus confirming the black hole nature of the accreting object. In addition, we estimate a distance toward the system of $8.0 \pm 0.9$ kpc.Comment: 7 pages, 5 figure

The natural ocean acidification and fertilization event caused by the submarine eruption of El Hierro

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The orbital period, black hole mass and distance to the X-ray transient GRS 1716-249 (=N Oph 93)

We present evidence for a 0.278(8) d (=6.7 h) orbital period in the X-ray transient GRS 1716-249 (=N Oph 93), based on a superhump modulation detected during the 1995 mini-outburst plus ellipsoidal variability in quiescence. With a quiescent magnitude of r=23.19+-0.15 N Oph 93 is too faint to warrant a full dynamical study through dedicated time-resolved spectroscopy. Instead, we apply the FWHM-K2 correlation to the disc Halpha emission line detected in Gran Telescopio Canarias spectra and obtain K2=521+-52 km/s. This leads to a mass function f(M)=4.1+-1.2 Msun, thus indicating the presence of a black hole in this historic X-ray transient. Furthermore, from the depth of the Halpha trough and the quiescent light curve we constrain the binary inclination to i=61+-15 deg, while the detection of superhumps sets an upper limit to the donor to compact star mass ratio q=M2/M1<=0.25. Our de-reddened (r-i) colour is consistent with a ~K6 main sequence star that fills its Roche lobe in a 0.278 d orbit. Using all this information we derive a compact object mass M1=6.4+3.2-2.0 Msun at 68 per cent confidence. We also constrain the distance to GRS 1716-249 to 6.9+-1.1 kpc, placing the binary ~0.8 kpc above the Galactic Plane, in support of a large natal kick.Comment: Accepted for publication in MNRAS, 12 pages, 9 figures, 2 Table

Escuela de cocina en San Sebastián

Escuela de cocina en San Sebastiá

Escuela de cocina en San Sebastián

Escuela de cocina en San Sebastiá

Escuela de teatro en Almagro

Escuela de teatro en Almagro. Convocatoria Marzo. Plan 1996. Proyecto fin de carrera. Universidad Politécnica de Madrid. Escuela Técnica Superior de Arquitectur

Escuela de teatro en Almagro

Escuela de teatro en Almagro. Convocatoria Marzo. Plan 1996. Proyecto fin de carrera. Universidad Politécnica de Madrid. Escuela Técnica Superior de Arquitectur