Showing papers on "Slab published in 1989"
TL;DR: In this paper, the role of H2O in the production of arc magmas at convergent plate boundaries was examined in both the downgoing lithosphere and the overlying mantle wedge.
Abstract: Dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of H2O in the production of magmas at convergent plate boundaries. The subduction of oceanic lithosphere, occurring with increasing pressures and rising temperatures, causes liberation of H2O from the slab. Amphibole, which can be stable to the highest PT conditions among hydrous phases in the slab, decomposes at around 90 km depth. It follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab-derived H2O is not a direct trigger for the production of arc magmas. Instead, the H2O released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals (serpentine, talc, amphibole, chlorite, and phlogopite). This hydrated peridotite is dragged downward on the slab toward higher PT regions and releases H2O to shallower potential magma source regions in the mantle wedge. Combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge, it is concluded that those minerals decompose beneath the forearc region. On the other hand, high PT experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front. Phlogopite in the peridotite decomposes to release H2O at a deeper level (about 200 km). H2O liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites. Along with the migration of H2O through the above processes, subduction components, especially large ion lithophile elements, can be overprinted on the magma source region, which governs the geochemical characteristics of arc magmas.
707 citations
TL;DR: In this article, a mechanism is proposed to explain epeirogenic motions of craton interiors in terms of the response of the lithosphere to subduction by analyzing the tilt of chronostratigraphic sequences in which the bounding horizons were deposited at approximately the same elevation with respect to sea level.
Abstract: A mechanism is proposed to explain epeirogenic motions of craton interiors in terms of the response of the lithosphere to subduction. The effects of changes in sea level are distinguished from subsidence of the basement by analyzing the tilt of chronostratigraphic sequences in which the bounding horizons were deposited at approximately the same elevation with respect to sea level. As an example, the Late Cretaceous subsidence and Tertiary uplift of the western interior of North America is examined, and a maximum tilt amplitude of 3 km, with a horizontal deflection scale of approximately 1400 km, is inferred. The link between platform sedimentation and subduction is tested by using numerical models of mantle convection which mimic the subduction and by examining the horizontal scale of the deflections to the overlying lithosphere. It is found that this scale is relatively insensitive to the temperature contrast between the slab and the surrounding mantle, the flexural rigidity of the lithosphere, and even the physical process assumed to govern the subduction. The most important factor affecting the scale is the dip of the subduction zone, and shallower subduction angles (less than 45°) can produce horizontal deflections of the order of 1000 km or more. In contrast, the vertical scale of the deflection is sensitive to all the above parameters. Using these results, two subduction models are introduced which predict both the time and length scales of the North American tilt, and it is conjectured that the process may be responsible for other regions of platform subsidence where subducted lithosphere may have passed beneath the continent at a shallow angle.
443 citations
TL;DR: In this paper, the authors investigate the evolution of lattice preferred orientation (LPO) of olivine crystals in thermal convective flows and find that the LPO becomes aligned with the flow direction when the flow is a progressive simple shear.
Abstract: Seismic anisotropy in the mantle is primarily due to deformation-induced lattice preferred orientation (LPO) of olivine crystals. The aim of this paper is to better understand how such LPO is produced by flow, and to learn whether observations of seismic anisotropy can be used to infer the local direction of flow within the mantle. The basis of the work is a two-dimensional theory which describes how LPO evolves during an arbitrary time-dependent deformation [Ribe, 1989]. I investigate the evolution of LPO beneath ocean ridges, above subducted slabs, and in thermal convective flows. The ocean ridge model predicts that the seismic anisotropy produced at a fast spreading ridge should be greater in magnitude than that produced at a slow spreading ridge, and that the fast axis should be more nearly horizontal. The subduction zone model predicts that strong seismic anisotropy should be produced above subducted slabs, with the fast axis aligned with the slab, regardless of the subduction angle. The evolution of LPO in typical convective flows is extremely complex, and depends strongly on such factors as the mode of heating and the surface boundary conditions. In general, there is no simple relation between the LPO and the local flow direction in any of the models considered. The attempt to use seismic anisotropy to map flow patterns on a global scale is therefore probably unwarranted. However, the LPO does become aligned with the flow direction when the flow is a progressive simple shear. Such a flow occurs in limited portions of the mantle: beneath the lithosphere at a fast spreading ridge, above subducted slabs, and in boundary layers beneath rigid surfaces such as continents. Observations of seismic anisotropy may therefore indicate the sense of shear at shallow depths in the mantle.
268 citations
TL;DR: In this paper, an analysis of 14 flights of marine terraces indicates a spatial pattern of varying uplift rates that agrees with that determined from previously dated terraces for the past 3-81 ka, and temporal changes in uplift rate from <1 m/ka to 3-5 m/k that may reflect response to changes in tectonic regime during passage of the Mendocino triple junction (MTJ).
Abstract: Analysis of the altitudinal spacing of 14 flights of marine terraces indicates a spatial pattern of varying uplift rates that agrees with that determined from previously dated terraces for the past 3-81 ka, and temporal changes in uplift rates from <1 m/ka to 3-5 m/ka that may reflect response to changes in tectonic regime during passage of the Mendocino triple junction (MTJ). A possible mechanism for regional uplift is growth of a slab window south of the MTJ. The region of most rapid uplift is 25-43 km south of the MTJ, immediately south of the northern boundary of the slab window. The coastline is tilted upward to the south in the region directly above the southern edge of the subducted Gorda plate. At Point Delgada, 55 km south of the present MTJ, where the northern edge of the slab window passes {approximately}300 ka, uplift rates have been 1.2 m/ka for at least 330 ka. More than 1.4 m.y. after passage of the southern edge of the subducted slab, at the Mendocino coast, uplift rates have been less than 0.4 m/ka for at least 330 ka.
198 citations
TL;DR: The geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics as discussed by the authors, and the possible effects of the existence and migration of slab windows on the Cordillera at various times include cessation of arc volcanism and replacement by rift or plate edge volcanism; lithospheric uplift, attenuation, and extension; and increased intensity of compressional tectonism.
Abstract: The geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics. As a consequence of subduction of the Kula-Farallon and East Pacific rises, slab windows formed and migrated beneath the North American Cordillera. The probable shape and extent of these windows, which represent the asthenosphere-filled gaps between two separating, subducting oceanic plates, are depicted from the Late Cretaceous to the present. Possible effects of the existence and migration of slab windows on the Cordillera at various times include cessation of arc volcanism and replacement by rift or plate- edge volcanism; lithospheric uplift, attenuation, and extension; and increased intensity of compressional tectonism. Eocene extensional tectonism and alkaline magmatism in southern British Columbia and the northwestern United States were facilitated by slab-window development.
198 citations
TL;DR: In this article, four well-calibrated thermobarometers were applied to pelitic samples collected along two cross-strike transects through the Main Central Thrust (MCT) zone and Tibetan Slab.
Abstract: The Main Central Thrust (MCT) south of Mt Everest in eastern Nepal is a 3 to 5km thick shear zone separating chlorite-bearing schist in the lower plate from sillimanite-bearing migmatitic gneiss in the overlying Tibetan Slab. The metamorphic grade increases through the MCT zone toward structurally higher levels. Previous workers have suggested that either post- or synmetamorphic thrust movement has caused this inversion of metamorphic isograds. In an effort to quantify the increase in grade and to constrain proposed structural relations between metamorphism and slip on the fault, four well-calibrated thermobarometers were applied to pelitic samples collected along two cross-strike transects through the MCT zone and Tibetan Slab. Results show an increase in apparent temperature up-section in the MCT zone from 778 K to 990 K and a decrease in temperature to ∼850 K in the lower Tibetan Slab, which is consistent with synmetamorphic thrust movement. A trend in calculated pressures across this section is less well-defined but, on average, decreases up-section with a gradient of ∼28MPa/km, resembling a lithostatic gradient. Pressure-temperature paths for zoned garnets from samples within the MCT zone, modelled using the Gibbs' Method, show a significant decrease in temperature and a slight decrease in pressure from core to rim, which might be expected for upper plate rocks during synmetamorphic thrust movement. Samples from the uppermost Tibetan Slab yield higher temperatures and pressures than those from the lower Tibetan Slab, which may be evidence for later‘resetting’ of thermobarometers by intrusion of the large amounts of leucogranite at that structural level.
181 citations
TL;DR: In this article, a velocity contrast of 5-10% occurs over a distance of 10-20 km to depths of at least 350 km, and the authors investigated whether such sharp contrasts can result form thermal structure, compositional differences, phase changes, or other effects such as preferred mineral orientation.
Abstract: Seismological studies of the interface between downgoing slabs of subducted lithosphere and the overriding mantle provide constraints against which models of mantle and slab temperature and bulk composition can be tested. These studies, employing waves reflected and converted at the slab/mantle interface, suggest that a velocity contrast of 5-10% occurs over a distance of 10-20 km to depths of at least 350 km. The authors have investigated whether such sharp contrasts can result form thermal structure, compositional differences, phase changes, or other effects such as preferred mineral orientation. Using a mantle and slab temperature model, a petrologic model of mantle and slab mineralogy, and a data base of elastic properties of mantle and slab phrases, theoretical seismic velocities were calculated and compared with the observed velocity contrast and boundary thickness constraints. At 9.6 GPa and 1000C (conditions modeled at the slab/mantle interface at {approximately}280-km depth), cooler temperatures in the slab interior produce, at constant composition, only approximately a 1.75% V{sub p} increase into the slab in any of the peridotitic and eclogitic mineralogies investigated. Variation in V{sub p} among the different bulk compositions is only approximately 0.5%. These contrasts are substantially lower than those obtained from the seismological studies andmore » indicate that temperature and bulk compositional differences between mantle and slab are inadequate to cause the observed velocity contrasts. They propose that phase transformations in mantle and slab mineralogies, notably elevation of the olivine-spinel phase change normally occurring at 400-km depth, are important factors in these sharp contrasts. Other contributing effects may include preferential mineral orientation near the slab surface and, at shallower depths, the presence of partial melt or hydrous fluid evolved from dehydration reactions along the interface.« less
129 citations
TL;DR: In this paper, Hartree-Fock calculations of the (0001) and (1010) crystal faces of α-alumina have been performed using a slab model and taking full account of two-dimensional periodicity.
112 citations
TL;DR: In this paper, an optical waveguide system consisting of an unclad fiber core suspended at a constant distance parallel to the surface of an infinite extended dielectric slab is investigated.
Abstract: An optical waveguide system consisting of an unclad fiber core suspended at a constant distance parallel to the surface of an infinite extended dielectric slab is investigated. Fiber and slab are both embedded in a homogeneous dielectric medium. The fate of light initially launched into the fiber depends on the relationship between the refractive index values of the slab and fiber. When the refractive index of the fiber is considerably larger than that of the slab, the latter exerts little influence on the wave, so that almost no power is transferred out of the fiber. When the refractive indexes of fiber and slab are more nearly the same, a beating phenomena is observed, that is, light is exchanged periodically between the fiber and the slab. However, after some distance the beating dies out. Some of the light energy remains in the combined system of fiber and slab, which can be regarded as a ridge waveguide, while the remaining light spreads out laterally in the slab. If the refractive index of the slab is considerably larger than that of the fiber, the slab acts as a drain on the light initially launched into the fiber. The light power in the fiber decreases exponentially with the distance along the fiber axis as it is transferred to the slab where it is carried away. >
85 citations
TL;DR: In this paper, the authors synthesize S wave synthetics by superposition of Gaussian beams for teleseismic S waves radiated by deep focus earthquakes located within the zone of high seismic velocities that define a descending lithospheric slab and demonstrate a phenomenon of slab diffraction that acts to lengthen the apparent pulse width of the S wave.
Abstract: Seismograms are synthesized by superposition of Gaussian beams for teleseismic S waves radiated by deep focus earthquakes located within the zone of high seismic velocities that define a descending lithospheric slab. The S wave synthetics demonstrate a phenomenon of slab diffraction that acts to lengthen the apparent pulse width of the S wave. Low-frequency energy leaks out of the slab and travels to the receivers along paths in the lower-velocity region surrounding the slab. Seismograms synthesized in fully three-dimensional models of slab structure show that slab diffraction strongly depends on the azimuth of the receiver with respect to strike of the slab. Slab diffraction lengthens the pulse width of S waves in the entire azimuthal range on the dipping side of the slab. As the azimuth approaches the strike of the slab, the diffracted phase may evolve into a higher-frequency, impulsive phase, which arrives after the minimum time arrival. Some slab models predict the slab phase to become a superposition of multipathed, ray theoretical arrivals as the azimuth approaches the strike of the slab. As the azimuth varies through the strike of the slab toward the side opposite the direction of dip, the slab phase is rapidly extinguished. Rapid variations in the complexity of S waveforms recorded along azimuths parallel to the strike of the slab are consistent with the predictions of synthetic seismograms. Evidence of slab diffraction in the S waveforms of the deepest focus earthquakes supports the hypothesis of slab penetration beyond 650 km depth. Broadband S waveforms from deep focus earthquakes in the Kuril-Kamchatka slab suggest that this slab penetrates below 650 km and that it may suffer some distortion in shape and advective thickening below this depth.
80 citations
TL;DR: In this article, a model is formulated to describe the drying process of a consolidated finite slab of wet porous material by forced convection of hot, dry air past the exposed surface of a slab.
TL;DR: In this article, the authors used the dual node technique to study the state of stress in the overriding and subducting plates meeting at a subduction zone and demonstrated that substantial horizontal deviatoric compressive stress occurs in the trench-arc region as a result of the downpull of the dense slab and the associated surface depression including the trench and other downflexing of the plates.
TL;DR: The pullout capacity of slab anchors in homogeneous sand depends on several factors including the type and density of the sand, and the depth, size, inclination, and shape of the slab as mentioned in this paper.
Abstract: The pullout capacity of slab anchors in homogeneous sand depends on several factors including the type and density of the sand, and the depth, size, inclination, and shape of the slab. Although num...
TL;DR: In this paper, the steady state vibration of a subway-soil-building system is determined using an appropriate finite element model using two different track support systems: direct fixation and a floating slab.
Abstract: The steady‐state vibration of a subway‐soil‐building system is determined using an appropriate finite element model. The vibration level in the podium block of the building is obtained for two different track support systems: direct fixation and a floating slab. A pair of unit harmonic loads is used to simulate the wheel loading from a single train. Because the subway consists of twin double boxes, different loading combinations are used to determine the maximum velocity response in the podium for the frequency range of interest. It is found that the vibration levels for the floating slab track system exceed those of the direct fixation track system in the low frequency range. However, in the high frequency range, the floating slab track system behaves as an effective vibration isolator.
TL;DR: In this paper, the longitudinal shear flow in composite steel and concrete beams is transferred across the steel-flange/concrete-slab interface at a discrete number of points by the dowel action of individual connectors.
Abstract: The longitudinal shear flow in composite steel and concrete beams is transferred across the steel‐flange/concrete‐slab interface at a discrete number of points by the dowel action of individual connectors. The dispersal of these concentrated loads into the concrete slab induces lateral tensile forces in the slab, which may cause the slab to split and lead to a loss of interaction and of shear strength. An analysis of 50 reinforced and unreinforced push‐out tests that failed by splitting, and finite element model studies of the shear flow in composite beams, have led to a method of predicting the occurrence of splitting due to the local action of individual connectors and the global action of groups of connectors. It has been found that transverse reinforcement does not prevent splitting but limits the extent of the split and hence limits the loss of interaction and shear connection.
TL;DR: In this paper, the authors considered two possibilities: 1) the event might be an unusual event in the sense that its location is unrelated to the position of the subducted slab and that there is probably no slab around it, or 2) the slab, at this depth, might be lying horizontally on top of the 650 km discontinuity, and the unusual event occurred in this horizontal part.
Abstract: An unusual earthquake (mb=6.2) occurred in the Izu-Bonin Island region in July 1982. The event, occurring at a depth of 545 km, was clearly separated from the main inclined seismic zone by a distance of about 200 km. To diagnose the situation, we have considered two possibilities: 1) the event might be an unusual event in the sense that its location is unrelated to the position of the subducted slab and that there is probably no slab around it, or 2) the slab, at this depth, might be lying horizontally on top of the 650 km discontinuity, and the unusual event occurred in this horizontal part. Both possibilities have been modeled structurally. We have computed the P-wave travel times for the present event, as well as for two other events located unambiguously in the inclined part of the seismic zone by employing a 3-D ray tracing program. The computed travel time residuals have been compared with the observations at stations in western Japan. The observations are found to be consistent with the model of the horizontally lying slab. Our result, thus, suggests that the slab might be horizontal at this depth in this part of the Izu-Bonin Islands.
01 Jul 1989
TL;DR: In this paper, a detailed 3D finite difference model of a slab floor was used to generate 93 annual simulations in parametric groups focusing on effects of size and shape, soil properties, boundary conditions, climate, insulation, and building shadow.
Abstract: : Earth-coupled heat transfer processes have been recognized in recent years as a potential source of significant energy savings in both conventional and earth-sheltered designs, Because of the complexity of the building/soil/ atmosphere interaction, however, important aspects of earth-coupled heat transfer are not well understood. There is a particular lack of three- dimensional foundation heat loss data. In this study, a detailed three- dimensional finite difference model of a slab floor was used to generate 93 annual simulations in parametric groups focusing on effects of size and shape, soil properties, boundary conditions, climate, insulation, and building shadow. These results indicate that soil thermal conductivity, ground surface conditions, foundation design, and floor shape/size are essential elements of a general change in heat transfer rate. Floors, heat transfer, Foundation (structures), Energy consumption.
TL;DR: In this paper, generalized impedance boundary conditions for a planar, homogeneous, magnetic dielectric slab grounded by a perfect electric conducting plane and for a magnetically-coated circular cylinder were derived by invoking the duality principle.
Abstract: Generalized impedance boundary conditions are derived for a planar, homogeneous, magnetic dielectric slab grounded by a perfect electric conducting plane and for a magnetic dielectric coated, perfect electric conducting circular cylinder. By invoking the duality principle, generalized resistive boundary conditions are also obtained for a planar, transparent dielectric slab. In the method followed here, it is not necessary to have a prior knowledge of the Fresnel reflection and/or transmission coefficients of the configuration under study to obtain the generalized boundary conditions. The boundary conditions developed here for the planar slab recover the exact Fresnel reflection and transmission (for the transparent slab) coefficients. Finally, the boundary conditions for the coated cylinder are used to obtain a solution for the scattering of an obliquely incident plane wave field, and this result is compared with the exact solution.
TL;DR: In this paper, it is argued that the large ion lithophile element (LILE) contents of island-arc tholeiites are dominated by the contribution from the subducted slab, whereas those of continental margin rocks are dominant by that from the mantle wedge.
Abstract: The large ion lithophile element (LILE) contents of island-arc tholeiites are dominated by the contribution from the subducted slab, whereas those of continental margin rocks are dominated by that from the mantle wedge. It is therefore argued that the LILE abundances in the destructive-margin rocks that are most depleted in high field strength elements offer the best indication of the LILE flux from the subducted slab, and that the slab contributes ∼25% of the Sr in average new crust. The remainder is derived from the mantle wedge, which is the principal site of crust generation and therefore must be replenished about every 75 m.y. Sr isotope arguments suggest that <5% of the Sr in new crust is from recycled continental crust with average crustal 87Sr/86Sr ratios. In the model outlined here, ≤5% of the Rb, Ba, and K in new crust is from the subducted slab, which is in contrast to previous suggestions that as much as 90% of the K in new crust might be from recycled continental material. As little as 3% of the Sr in subducted crust is required for the slab-derived flux, which further implies that most of the LILE in oceanic crust are recycled deep into the upper mantle.
TL;DR: In this paper, an experimental investigation of the shear strength of composite plate girders with rectangular web cut-outs is described, and it is shown that if adequate tension connectors are provided between the plate girder and composite concrete slab, the shears strength of the composite girder would be significantly higher than that of the plate Girder alone.
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31 May 1989
TL;DR: In this paper, the studs have a flange which abuts the inner surface of the slab, and a plurality of tabs which project downwardly from the flange to key the stud.
Abstract: Composite building panels comprising a slab of cementitious fiber reinforced material and a stud framework keyed thereto. The studs have a flange which abuts the inner surface of the slab, and a plurality of tabs which project downwardly from the flange to key the stud. Adjacent tabs are axially spaced apart, and may also be transversely staggard, to reduce the incidence of cracking of the slab, and may be upset from the flange material. The slabs may be relatively thin i.e. 2 cms. The tabs may also serve to retain rod or mesh reinforcement in thicker slabs.
TL;DR: In this article, two-dimensional, Cartesian finite difference models of compressible convection with constant and variable viscosity and fixed bottom temperature are presented, and density variations according to the Adams Williamson equation of state are included.
Abstract: Two-dimensional, Cartesian finite difference models of compressible convection with constant and variable viscosity and fixed bottom temperature are presented. Density variations according to the Adams Williamson equation of state are included. In the case of constant viscosity convection, viscous and adiabatic heating damp the flow. Compressible density variations hardly influence geoid undulations; however, the lower thermal boundary layer becomes thinner, and the mean cell temperature increases. In the case of variable viscosity, the nonlinear coupling between compression, adiabatic and viscous heating, and a temperature-, pressure-, and stress-dependent rheology leads to important consequences: The upwelling flow broadens and plumes are retarded. The flow strongly concentrates toward the downwelling region and becomes mechanically decoupled from the interior of the cell by a low-viscosity region. This mechanism seems to be important for the formation of subducting slabs. Extrapolated to mantle conditions, two low-viscosity regions are predicted flanking the slab on either side and inhibiting an early dispersal and mixing of slab material into the mantle. This process might be aided by an increase of negative buoyancy forces with depth as observed in the models. Further results are as follows: Increasing the dissipation number in variable viscosity convection may either damp or speed up convection, depending on the rheology. Models with internal heating and a fixed bottom temperature show that the threshold to time-dependent variable viscosity convection is drastically reduced if the anelastic liquid approximation is applied instead of the extended Boussinesq approximation.
TL;DR: The behavior of composite floor beams in eccentrically braced steel frames (EBFs) subjected to severe cyclic loading was experimentally investigated in this paper, where they were found to yield and dissipate energy primarily in shear and have a greater cyclic capacity compared to bare steel links.
Abstract: The behavior of composite floor beams in eccentrically braced steel frames (EBFs) subjected to severe cyclic loading was experimentally investigated. The objectives of this study were to assess the cyclic strength and ductility of links in composite floor systems, and to determine the extent of the floor‐slab participation in the response of EBFs to earthquake loading. Six short links with a composite floor slab, and two short, bare steel links were tested using two‐thirds‐scale EBF subassemblies. The composite links, designed using current provisions for short, bare steel links, were found to yield and dissipate energy primarily in shear, and have a greater cyclic capacity compared to bare steel links. Web buckling in the composite links was adequately controlled using bare‐steel‐link design criteria to assure cyclic ductility. The extent of slab damage in the composite specimens was remarkably small and occurred primarily in the vicinity of the link. The test results indicate that the floor slab by itse...
TL;DR: In this paper, it was shown that the components of positive and negative buoyancy must be almost equal in order to cause significant component separation or to selectively block deep penetration of buoyant slab components in the transition zone.
Abstract: Subducted oceanic lithosphere consists of a sandwich of component layers (MORB underlain by depleted parent mantle). These layers give rise to intrinsic density contrasts within the slab which have been hypothesized to cause component separation after subduction. We explore this process through numerical models of simple layered slabs and through convection models which incorporate large, local chemical density contrasts. We show that the components of positive and negative buoyancy (density contrast × component volume) must be almost equal in order to cause significant component separation or to selectively block deep penetration of buoyant slab components in the transition zone. Published petrological constraints on component densities and relative volumes indicate that such buoyancy neutralization is not achieved in subducted slabs. Therefore, component separation should not occur on the timescale associated with the sinking of slabs through the upper mantle and transition zone.
Patent•
27 Jun 1989
TL;DR: In this article, a three-layer insulated concrete panel includes as the middle layer an insulating slab having grooves which provide a form for casting of concrete supporting ribs integral with a layer of concrete cast over the face.
Abstract: A three-layer insulated concrete panel includes as the middle layer an insulating slab having grooves which provide a form for casting of concrete supporting ribs integral with a layer of concrete cast over the grooved face. A layer of material, such as particle board, is bonded to the ungrooved face of the slab. In preparing the panel, the slab is placed on a flat surface with the particle board face down. Forms are then placed in spaced-apart relation to panel edges, and concrete is cast into the forms and grooves and over the grooved panel face. The insulating slab provides a form for casting of supporting ribs and is permanently retained in the panel, giving it a high insulating value. An assembly of such panels in a roof or ceiling structure is disclosed wherein individual panels are placed in final position, and joints between adjacent panel edges are obtained by covering exposed strips along adjacent panel edges with a cap member and applying concrete over the cap member.
TL;DR: In this paper, the effect of torsional stiffness of the transverse beam elements on the effective width of slab participating as a tension flange to the longitudinal beam was investigated on three one-half scale reinforced concrete beamcolumn-slab subassemblages.
Abstract: The effective width of slab to be used for the case of lateral loading has not been explicitly addressed in design codes. Ignoring the slab contribution to the flexural capacity of the beams leads to a significant underestimation in structural strength. It may also lead to a failure mechanism different than that anticipated. Tests were conducted on three one‐half scale reinforced concrete beamcolumn‐slab subassemblages to determine the influence of the torsional stiffness of the transverse beam elements on the effective width of slab participating as a tension flange to the longitudinal beam. The effect of initial damage due to loading in the transverse direction was also investigated for one of the models. All of the models were subjected to the same cyclic lateral load history. It was concluded that the effective width of slab was greater for the models with increased transverse torsional stiffness. The difference in strength among the models was larger at the earlier loading cycles. At the maximum load...
TL;DR: In this article, the bulging behavior of the solidified shell in continuously cast slabs has been numerically analyzed using the elasto-plastic and creep Finite Element Method.
Abstract: The bulging behavior of the solidified shell in continuously cast slabs have been numerically analyzed using the elasto-plastic and creep Finite Element Method. Three-dimensional model has been applied in order to investigate the effect of the narrow face shell on restraining the bulging deflection. Three-dimensional shell profile and temperature distribution in it have been determined using the segregation considered solidification analysis method. In this way, strains occurring at the solidification front near the narrow face of the slab, as well as those occurring in the broad face have been computed. The computed bulging deflection have been in good agreement with measurements, and the relationship between the strain caused by the bulging and the internal cracks have been investigated. In addition, the effect of the slab width on the bulging are discussed.
TL;DR: In this article, a torsional oscillator containing a slab of liquid 3He of thickness 105 µm and diameter 8.38 mm is described, where the uniform texture for the A phase gives values of ρs⊥ and η44.
Abstract: Experiments on a torsional oscillator containing a slab of liquid3He of thickness 105 µm and diameter 8.38 mm are described. Normal phase experiments confirm the theory of the oscillator dynamics but an apparent descrase in the measured value of ηT2 at lowT casts doubt on the existing slip theory. Measurements for the uniform texture for the A phase give values of ρs⊥ and η44. The ρs⊥ measurements suggest that the A-phase energy gap is enhanced by a factor 1.24 over the BCS value. Distortion of the uniform texture by a magnetic field perpendicular to the slab occurs at a threshold field slightly smaller than predicted. Measurements for fields at different angles to the slab enable accurate values to be deduced for the superfluid density anisotropy and two other viscosity coefficients. The remaining two viscosity coefficients are only poorly determined. Flow alignment of the orbital texture was achieved by increasing the oscillator amplitude. A different texture obtained on some occasions after warming from the B phase was investigated but is not understood.
TL;DR: In this article, an experimental study of the diffusion and condensation of water vapour in fibreglass slab insulations is reported, where water is sprayed on the hot face of the slab and it is tested in a heat flow meter apparatus.
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28 Jun 1989TL;DR: In this article, a flexible sealing sheet with a removable edge is used to expose the lower end of a gel slab to a buffer solution to permit the performance of an electrophoretic separation in the enclosure once the gel has been formed.
Abstract: Slab gels are cast in a gel enclosure which consists of a flat rectangular plate held against a larger plate by a flexible sealing sheet with a removable edge. The smaller plate is retained within raised edges along three sides of the larger plate and rests on a pair of shoulders along two of the raised edges. The sealing sheet spans all three raised edges and the smaller plate resting between them, thereby sealing three sides of the chamber between the plates, the width of the chamber being established by the shoulders. One edge of the sealing sheet is removable to expose the lower end of the gel slab to a buffer solution to permit the performance of an electrophoretic separation in the enclosure once the gel has been formed. A depression in the raised edge underlying the removable edge of the sealing sheet increases the access of a buffer solution to the lower end of the gel slab during electrophoresis.