Showing papers on "Slab published in 1976"

Method of making a twisting ball panel display

Abstract: A method of making a display characterized by a plurality of particles which have an electrical anisotropy due to hemispherical surface coatings of different Zeta potential and their distribution in a volume of a dielectric liquid and which also have an optical anisotropy due to the hemispherical surface coatings having different optical characteristics. The particles are mixed with a light transparent liquid which is subsequently cured to form an elastomeric or rigid slab. Following curing of the liquid, the slab is emersed in a plasticizer (dielectric liquid) which is absorbed by the slab and which causes the slab to expand slightly. Expansion of the slab around the particles provides a plasticizer-filled cavity around each particle which cavities allow the particles to rotate to provide a display in accordance with their optical anisotropy but does not allow substantial translation of the particles.

Geophysical and Geochemical Constraints at Converging Plate Boundaries?Part I: Dehydration in the Downgoing Slab

Abstract: Summary Geochemical constraints based upon compositions and mechanisms of formation and eruption of island arc volcanic rocks strongly suggest hydrous conditions in the region of primary magma generation. The source of most of the water is probably dehydration of the oceanic crust during underthrusting. Chemical reactions involving dehydration of representative oceanic crustal assemblages absorb enough heat to possibly negate any frictional heat which may be generated along the Benioff-Wadati zone in the upper 75 to 100 km of the underthrust zone. Calculations of thermodynamic parameters of relevant reactions at elevated pressures and temperatures show that N 50cal of heat are absorbed per gramme of oceanic crust dehydrated. The result of this heat absorption is suppression of isotherms not only in the oceanic crustal section of the downgoing slab but also in the overlying mantle wedge. Therefore, low heat fiow measured from the trenches to the volcanic arcs may be caused in part by the heat-sink effect of dehydration in the downgoing slab. The water released by dehydration either remains in the slab promoting its melting and the generation of andesitic primary magmas and/or escapes into the overlying wedge of mantle promoting its melting and the generation of the basaltic or andesitic primary magmas. The major thermal effect of the released water is to cool the wedge overlying the slab. The progressive geochemical changes in arc volcanism both in space and time may be controlled by the thermal conditions at the downgoing slab-peridotite wedge interface.

Bridge deck behaviour

Abstract: Preface. Structural forms and calculation methods. Beam decks and frames. Slab decks. Beam-and-slab decks. Multicellular decks. Box-girder decks. Space frame methods and slab membrane action. Shear lag and edge stiffening. Skew, tapered and curved decks. Distribution coefficients. Temperature and prestress loading. Harmonic analysis and folded plate theory. Finite element method. Stiffnesses of supports and foundations. Appendices. A: Product integrals. Functions of load on a single span. Harmonic components. B: Calculation of torsion constants for solid beams. Author index. Subject index.

Underthrusting and Quaternary faulting in northern Central America

Abstract: Earthquakes relocated by joint hypo-center determination define an inclined seismic zone in Guatemala and El Salvador approximately 15 km thick. This zone is segmented by one large change of strike and dip and two smaller changes in dip. The inclined seismic zone marks the upper part of the underthrust slab and the discontinuities represent breaks segmenting the slab. The breaks occur in areas where they had been predicted on the basis of abrupt discontinuities in the volcanic chain. Quaternary faulting is dominated by transcurrent fault zones. Left-lateral strike-slip fault zones strike transverse to the arc and coincide with the proposed breaks in the underthrust slab. Right-lateral fault zones strike parallel to the arc and approximately coincide with the volcanic chain. Subsidence of at least 500 m has occurred along the strike of the left-lateral and right-lateral fault zones and created a grid of troughs and depressions. The amount of horizontal movement is about 10 km for the transverse and longitudinal fault zones. These seismic and geologic data suggest a segmented underthrusting process in northern Central America. The wedge of overriding lithosphere and the underthrust slab have transverse structures in the same areas. The left-lateral motion on N30°E-striking transverse faults can be deduced from the segmentation and an increasing rate of plate convergence to the southeast.

Heat flow, gap formation and break-outs in the continuous casting of steel slabs

Abstract: A theoretical investigation of heat flow and gap formation in the mold of a continuous slab caster has been undertaken using a mathematical model, with the ultimate purpose of predicting the casting conditions which can lead to break-outs. The mathematical model that has been developed for this study is capable of treating the heat flow and air gap as coupled phenomena, and can accept operating variables such as slab size, casting speed, mold taper, and thermal conductivity of the mold powder, as input. Four different cases of slab casting have been investigated; and it has been found that hot spots can form on the surface of the slab within a few centimeters of the corners. Depending on their temperature, it is suggested that these hot spots may give rise to the formation of break-outs off the corners of the slab. From an examination of the behavior of the hot spots, the susceptibility of the cases studied to break-outs has been evaluated. The usefulness of the present analysis in qualitatively ascertaining the location and extent of mold wear under different casting conditions has also been examined.

Extrusion casting apparatus

Abstract: Apparatus for manufacturing precast, prestressed, hollow-core, concrete slabs, including an extruder which is movable along a fixed casting bed to extrude from a relatively dry concrete mix a slab having longitudinally extending hollow cores and grout keyways extending along the slab sides. Multiple, core-forming augers in the extruder are shaped and positioned with respect to a feed opening in the extruder in a manner which eliminates cavitations in the slab and provides smooth, well formed slab surfaces and proper bonding between the concrete and prestressing wires.

Strength of Slab-Column Connections with Shear and Unbalanced Flexure

Abstract: Tests were conducted on eight 1/2-scale models of reinforced concrete interior flat plate-column connections transferring shear and unbalanced moment from gravity and simulated seismic loading. The slab at the connection contained either no shear reinforcement or shear reinforcement in the form of either cranked bars, structural steel shearhead or closed vertical stirrups. The simulated seismic loading was statically applied, either monotonically or cyclically in the inelastic range. The strength and ductility of the connections, and the modes of failure, were compared. The connections without shear reinforcement failed suddenly in diagonal tension. The use of cranked bars as shear reinforcement increased the strength of the connection but did not increase the ductility. The use of a structural steel shearhead resulted in an increase in strength and in a limited increase in ductility. The use of closed vertical stirrups around the slab bars, which passed through the column, resulted in an increase in the strength and in a substantial increase in the ductility of the connection.

Edge-lifting system for a concrete slab

Abstract: A system for the edge-lifting of a horizontally disposed concrete slab either for transport or tilt-up operations, and embodying components which, after positioning in the slab form, become embedded in the slab after the wet concrete is poured and has become set or hardened. Such components include a horizontal reinforcing bar which extends through the edge region of the slab at a low level and imparts reaction force to a slab-lifting anchor bolt thereabove through the medium of a hanger clip at the time that the slab is lifted. The anchor bolt is fixedly positioned in the slab form and the hanger clip is hung on the anchor bolt and serves to support the reinforcing rod therebeneath in cradle-like fashion preparatory to a concrete-pouring operation for slab-forming purposes. The hanger clip of the system obviates the necessity of creating an upward offset in the reinforcing rod and hanging the rod directly on the anchor bolt at the point of the offset.

Concrete slab hoisting apparatus

Abstract: A socket cavity formed in a concrete slab of the type poured horizontally and subsequently tilted up, which cavity affords engagement of hoisting equipment to the slab. The inner portion of the cavity is in the form of a frusto-conical wall surface communicating with the surface of the cavity through a cylindrical bore concentric with the frusto-conical surface. The cavity is formed by placing in the slab form an expendable flask-like hollow article formed of synthetic resin or the like which is left in the slab after erection thereof. Engaging apparatus cooperable with the cavity which has on the inner end thereof arms that are pivotally moveable between a retracted position and an extended position, the arms engaging the frusto-conical wall of the cavity when in the extended position. The apparatus includes mechanism at the outer end thereof for effecting retraction or extension of the arms, the mechanism being remotely operable so as to afford disengagement of the hoisting mechanism from the slab from a remote location after erection of the slab.

Mechanism of mantle earthquakes near the junction of the kurile and the northern honshu arcs

Abstract: The geometry of the slab as well as the stress inside the slab near the junction of the Kurile and the northern Honshu arcs, that is, the Hokkaido corner, are studied based on the seismicity and the focal mechanism solutions of mantle earthquakes. Focal mechanism solutions vary depending on the focal depth and the local strike of the slab. The distribution of mantle earthquakes and the variation of the mechanism solutions reveal slab contortion on the Kurile side of the Hokkaido corner. The relative motion on the fault plane is estimated based on the analysis of source processes of mantle earthquakes. The sense of the earthquake slip motion is consistent with the sense of the slab contortion. This may indicate that the slab contortion, suggesting a plastic deformation, results partly from the earthquake slip motion.

Textures in /sup 3/He-A: Hydrodynamic and magnetic effects in a slab

Abstract: The Ginzburg-Landau equations are used to analyze the equilibrium configuration of $^{3}\mathrm{He}\ensuremath{-}A$ in a slab, subject to either a bulk hydrodynamic flow or a uniform tipped magnetic field. Both perturbations can induce an orientational transition from an essentially uniform texture to one with large deformations. The associated phase boundaries are determined both variationally and exactly.

Punching of flat plates under static and dynamic horizontal forces.

Abstract: The results of a laboratory investigation on the strength and deformation of flat slab floors at their connection with columns when subjected to static or dynamic horizontal forces are presented. Six full scale specimens of a slab-column connection were subjected to a constant axial force representing gravity load, and a varying static and dynamic moment transferred between the column and the slab. The amount of the flexure reinforcement in the slab was variable. No shear reinforcement was provided. Results indicate higher strength and higher energy absorption capacities of the slab in the dynamic tests. The increase in bending reinforcement in both the static and dynamic tests resulted in an increase in strength, but with an important decrease in the energy absorption capacity and the ductility. These two properties are important requirements, particularly for structures designed to resist dy­ namic loads, such as blast waves or earthquakes.

Field testing of a reinforced concrete highway bridge to collapse

Abstract: A three-span reinforced concrete slab bridge was loaded to collapse. The slab was 9.75 m (32 ft) wide and 30.5 cm (12 in) thick, and on each edge was cast a 92 by 25.4-cm (34 by 10-in) curb. Loading was produced by hydraulic rams that were reacted to by overhead steel beams attached to the piers by tension rods through the slabs. the load was increased at intervals, and at each interval deflection and strain on the concrete surface were measured. The strength of the concrete and steel materials was more than the design minimum values; average cylinder strength was 47.33 MPa (6865 lbf/in square) compared with a design value of 20.68 MPa (3000 lbf/in square), and average steel coupon yield strength was 365.77 MPa (53 050 lbf/in square) compared with a design value of 275.79 MPa (40 000 lbf/in square). The results indicate that (a) the measured concrete stresses were lower than the calculated values; (b) the load causing first permanent set was accurately predicted by calculaing the yield moment in the slab; (c) the collapse load was accurately predicted by considering the formation of yield moments along the centerline and over the piers of the bridge for a channel section loaded around its weak axis; and (d) based on the line load for the center span, it would take 8 HS20-44 trucks placed in the center of the bridge to cause any permanent deflection and 20 HS20-44 trucks to cause collapse. /Author/

Optical surface topography mapping system

Abstract: A first laser beam is reflected from the front and rear surfaces of a partially silvered glass slab generating a diverging set of interference fringes which are collimated by a positive lens. A second set of fringes is generated by a second laser beam and second partially silvered glass slab and is positioned to project through the first slab and is collimated by the same positive lens. The second pattern is aligned coaxially and mutually perpendicular to the first pattern creating a rectangular parallopiped grid pattern projected upon an observed object.

Method and apparatus for symmetrically cooling heated workpieces

Abstract: The disclosure pertains to an arrangement for cooling a heated workpiece, such as, strip or slab as it issues from a rolling mill or continuous slab caster. The longitudinally moving workpiece is caused to pass between a number of coolant discharge headers arranged above and below the workpiece in which, during its cooling, the coolig rates of the upper and lower surfaces of the workpiece differ. The effective discharge of the headers is varied to equalize the cooling rates of the upper and lower surfaces of the workpiece to symmetrically cool the workpiece.

Ultimate strength of continuous composite beams

Abstract: Ultimate strength and failure modes of continuous composite beams are studied experimentally and theoretically. The theoretical analysis is based on a stress-strain relationship for steel including elastic, plastic, and strain-hardening regions and a stress-strain relation for concrete including ascending and descending portions. Behavioral studies were conducted for a series of beams in which steel sections, concrete slab thickness, and amounts of longitudinal slab reinforcement are varied. Three two-span continuous composite beams were tested. Theoretical values of ultimate load are in good agreement with test results. Based on experimental and theoretical results, design requirements are proposed for ultimate strength design of continuous composite beams.

The resistance of an infinite slab with a disc electrode as a mixed boundary value problem

Abstract: We consider the resistance of an infinite slab of material with a disc contact source on one side and with current collected over the entire back plane. By imposing the boundary condition of a constant potential over the source region, the problem becomes one of mixed boundary conditions, requiring the solution of a pair of dual integral equations. These equations are solved in terms of a Fredholm integral equation of the second kind. Calculations of the resistance are performed for values of slab thicknesses ranging from 0·05 to 4 times the disc contact radius, and the solutions obtained agree closely with Foxhall and Lewis' electrolytic tank measurements. The results are used to establish the range of validity of two approximate methods previously proposed for correction factor calculations in spreading resistance measurements on semiconductor device structures.

Patient shifting aid and method of using same

Abstract: A new and improved patient shifting aid and method of using same for assistance in transferring of reclining patients normally unable to propel themselves between patient supports, for example, a stretcher and bed. The patient is essentially placed on a flexible plastic shifting slab having a low friction coefficient for relatively easy sliding and minimizing the direct application to the patient of any shifting force, as well as easily enabling sliding the shifting slab under a patient. While the plastic slab is flexible, the slab is strong enough to enable normal lifting of a patient by two or more persons. In addition, patient X-rays may be taken through the shifting slab further reducing patient handling.

Joint-forming device

Abstract: A device for forming surface joints in hardenable slab type structural materials such as freshly poured concrete is disclosed. The elongated joint former includes a pliable section having a depth which may be approximately one-fourth the thickness of the slab, with outwardly extending fins near its bottom and with a split upper end formed by a pair of separable walls. For implanting the pliable section in a fresh slab prior to its setting, a relatively rigid T-shaped implanting member is inserted into the split and the joint former is driven or vibrated down into the slab until the upper end of the pliable section is approximately even with or slightly below the surface of the slab. The T-shaped member is later removed, leaving an open-topped cavity in the joint into which particle fines eventually accumulate to continually push outwardly on the pliable member on either side of the split and thereby urge the sides of the pliable member against the slab and form an effective water seal during periods of slab expansion and contraction.

Note on the theory of transmission of electromagnetic waves in a coal seam

Abstract: A coal seam is idealized as a resistive slab bounded by more conductive rock. The source is taken to be a vertical electric dipole. It is shown that the dominant mode has relatively low attenuation.

Cusp shape reflectors to pump disk or slab lasers

Abstract: A two-dimensional ray tracing program is used to predict the performance of lighthouses to pump disk or slab lasers. The model is tested by comparing calculations with the results of light intensity and fluorescence measurements. Pumping efficiency and uniformity are investigated as functions of lamp spacing in a configuration employing cusp shape and plane back reflectors. It is found that doubling the number of lamps from an arrangement that provides optimal coupling brings an improvement in pumping of typically 60%.

Composite construction interrupted reinforced concrete slab - has parts linked by girders with cutouts or latticed

Abstract: The reinforced-concrete element, for use in composite construction, consists of a slab which is interrupted at one or more points. The interrupted parts of the slab (1) are joined together by one or more girders (3) which project upwards. The girders are pref. provided with cutouts (4) above the slab or the girders may be in the form of a steel lattice structure. The slab may be bent upwards at the edges (2). Individual slabs may be bent out of line at a shallow angle relative to each other. Site concrete can be easily built in as sheathing crane handling and rapid assembly are easy and min. reinforcement on site is needed. Individual loads are distributed crossways and a slender optical finish is practicable.