Showing papers on "Slab published in 1970"

Thermal regime of a downgoing slab and new global tectonics

Abstract: The new global tectonics and sea-floor spreading hypotheses imply downwarping and descent of the lithosphere in island-arc regions. These downgoing slabs of crust and upper-mantle material will affect the local temperature regime. Geophysically observable variables of surface-heat flux and gravity and seismic travel times will be influenced by the temperature. Using a quasi-dynamic computational scheme and a finite difference solution of the conservation of energy equation we have determined the effects of spreading rate, adiabatic compression, radioactivity, phase changes, and strain heating on the temperature regime of a downgoing slab. Effects of these parameters on surface heat flux, gravity anomalies, and local seismic travel time are also estimated. Predicted travel-time anomalies show good agreement with observed anomalies in Japan and Tonga-Kermadec. Several implications on the localized mechanical behavior of the upper mantle and the evolution of a downwarping slab are made on the basis of our computational results.

Radiation losses of tapered dielectric slab waveguides

Abstract: In this paper we calculate radiation losses of a single mode dielectric slab waveguide for TE and TM modes. The theory is based on the determination of the radiation losses of one abrupt step. We obtain the losses of arbitrarily deformed waveguides by regarding the arbitrary deformations as a succession of infinitely many infinitesimal steps. This method yields the same results as a very different method presented earlier. It allows us to calculate the losses of TM modes that were hard to obtain by the earlier method. The radiation losses of single mode slab waveguides with abrupt steps of a 2:1 ratio are surprisingly low and can be kept below 1 percent by dimensioning the guide properly. The loss advantage of linear tapers becomes noticeable only when the tapers are very long. An optimized taper changes more rapidly in its wider portion and becomes more gradual in its narrow part.

Surface magnetostatic modes of a ferrite slab

Abstract: The wavenumber and the group velocity of the magnetostatic surface wave guided by a ferrite slab magnetized parallel to its face are investigated. One aspect of experimental observation of the group delay times of the magnetostatic surface waves supported by a ferrite slab without and with a metal plate placed against one of the faces is explained.

A theory of snow slab failure

Abstract: Existing theories of snow slab failure emphasize failure either in the tensile zone of the slab or along the slab base. The tensile zone theories do not explain measured fracture angles or the observed fact that a necessary condition for extensive fracturing is weakness in the basal plane. On the other hand, the basal theories do not explain where the tensile stress originates and why brittle failure commences in the tensile zone and propagates into the basal plane. A new model is proposed wherein the critical value of the maximum principal stress evaluated at the tensile zone is coupled to the inability of the slab to sustain basal stress. A scale analysis of the equilibrium equations shows that this model predicts the measured fracture angles and large values for the maximum principal stress.

Characteristics of Magnetostatic Surface Waves for a Metalized Ferrite Slab

Abstract: Detailed calculations of the characteristics of the magnetostatic surface waves in a ferrite slab with a metalized surface are presented. The region of validity of the effective boundary condition model (EBCM) discussed by Seshadri is established. It is shown that the dispersion characteristics of overlayed magnetic systems can be modified and tailored to have a variety of frequency‐versus‐wavenumber properties. In general the modes are lossy and the degree of damping depends critically on the characteristic lengths of the problem.

Composite concrete slab and steel joist construction

Abstract: A composite action open-web steel joist, supporting beams and girders, and reinforced concrete slab interconnection. Upper apex portions of the steel joist webbing protrude through the upper chord members of the joist, and through apertures provided in the sheet metal formwork placed over such joists prior to the pouring of the concrete slab. The improvement relates to a continuous round rod secured near the apex of each projecting web member parallel to the longitudinal axis of the joist and a reinforcing wire mesh draped between said rods, thus permitting greater spacing between said joists, whereby said protruding apex portions, said rods and said draped wire mesh will be encased within the slab to act as shear interconnection and reinforcement devices therein, to secure the joist and formwork together, to enhance the locking of the concrete slab to the protruding joist apex portions, and to the supporting beams through the joist end connection welded to the beam or girder, and to reinforce said concrete slab. This improvement makes optional the use of wedge members forced between such protruding joist apex portions.

Analysis of structural behavior of AASHO road test rigid pavements

Abstract: THE STUDY WAS CONDUCTED TO EXAMINE EXISTING THEORIES FOR STRUCTURAL BEHAVIOR OF RIGID PAVEMENTS IN VIEW OF THE LARGE AMOUNT OF CONTROL FIELD PERFORMANCE DATA COLLECTED DURING AASHO ROAD TEST. THE STUDY IS CENTERED AROUND TWO PRINCIPLE INDICATORS OF RIGID PAVEMENT PERFORMANCE; STRESSES IN THE PAVEMENT SLABS AND PAVEMENT DEFLECTIONS UNDER LOAD. ATTENTION IS ALSO GIVEN TO THE PATTERNS OF SLAB CRACKING AND FAILURE UNDER THE VEHICULAR TRAFFIC. A CRITICAL REVIEW IS PRESENTED OF EXISTING THEORIES OF STRUCTURAL BEHAVIOR OF RIGID PAVEMENTS. SIMPLE ANALYTICAL EXPRESSIONS FOR EVALUATION OF THE COEFFICIENT OF SUBGRADE REACTION IN TERMS OF KNOWN CHARACTERISTICS OF THE SLAB IN SUBGRADE ARE PRESENTED. THE STRUCTURAL BEHAVIOR OF THE RIGID PAVEMENTS OF THE AASHO ROAD TEST IS STUDIED. IT IS SHOWN THAT THE OVER-ALL RESPONSE OF THE AASHO SUBGRADE TO LOADS IS COMPARABLE TO RESPONSE OF AN IDEAL ISOTROPIC ELASTIC SOLID. WITH PROPER SELECTION OF THE COEFFICIENTS OF SUBGRADE REACTION, THE WINKLER SUBGRADE MODEL (USED IN THE WESTERGAARD THEORY OF RIGID PAVEMENTS) CAN ALSO LEAD TO GOOD PREDICTIONS OF PAVEMENT STRESSES AND DEFLECTIONS. THE COEFFICIENT OF SUBGRADE REACTION FOR THE AASHO PAVEMENT/SUBGRADE SYSTEMS IS A VARIABLE QUALITY, WHICH IS INVERSELY PROPORTIONAL TO THE PAVEMENT SLAB THICHNESS. IT IS DEMONSTRATED THAT THE COMBINED TENSILE STRESS IN PAVEMENT SLABS REPRESENTS THE BEST INDICATOR OF PAVEMENT PERFORMANCE. AN EXPRESSION RELATING THE ULTIMATE NUMBER OF AXLE-LOAD APPLICATIONS TO THE FLEXURAL STRENGTH OF THE PAVEMENT MATERIAL, THE THICKNESS OF THE PAVEMENT SLAB, AND THE MAGNITUDE OF THE AXLE-LOAD IS DESIRED, INDICATING THAT THE PAVEMENT LIFE SHOULD BE PROPORTIONAL TO THE FOURTH POWER OF STRENGTH AND TO THE FIFTH POWER OF SLAB THICKNESS AND INVERSELY PROPORTIONAL TO THE FOURTH POWER OF THE AXLE- LOAD. THIS EXPRESSION OFFERS A RATIONAL BASIS FOR EVALUATION OF A EQUIVALENT NUMBER OF AXLE-LOAD APPLICATIONS FOR RIGID PAVEMENTS SUBJECTED TO MIXED TRAFFIC.

Plate Tectonics in the Hispaniola Area

Abstract: Seismic and other geophysical and geological evidence suggest that the Caribbean plate, at eastern Hispaniola, is being underthrust by a relatively small slab of Americas plate The slab is terminated at its southeastern and northwestern ends by hinge faults, which mark the juncture of the Puerto Rico and Cayman transform faults, respectively, with the slab Age determinations, based on the length of the seismic zone associated with this slab, indicate an upper Tertiary time of origin for this eastern Hispaniola miniature arc structure

Neutron Transport in a Nonuniform Slab with Generalized Boundary Conditions

Abstract: We prove the existence and the uniqueness of the solution of the initial‐value problem for neutron transport in a nonuniform slab with generalized boundary conditions, which include the vacuum and the perfect reflection boundary conditions as particular cases Moreover, we show that the position‐dependent transport operator has at least one real eigenvalue and we indicate the asymptotic behavior of the neutron density as t → + ∞

Penetration of an electromagnetic wave into a hot plasma slab.

Abstract: The penetration of a small‐amplitude high‐frequency electromagnetic wave into a plasma slab is calculated making allowance for the thermal motion of electrons. For low collision rates the electromagnetic field distribution in the plasma is strongly dependent on the ratio of the wave period to the transit time of electrons crossing the slab.

Gripping and sealing system for slab facing materials

Abstract: A mounting system for slab facing materials including a plurality of contiguous slabs, each slab having a kerf formed in the peripheral edges thereof. This system includes a structural channel member for each facing slab edge, with the structural channel members having first flange portions for cooperatively gripping each slab, and second flange portions with the second flange portions of adjacent channel members of two contiguous slabs defining first and second plunum chambers. Spline means inserted into the first plenum chamber act as both a moisture stop and an air pressure equalizer while gasket means are inserted into the second plenum chamber for cushioning and sealing purposes. Third flange portions of the channel members serve as a joiner member for attachment lugs. Structural channel members for corner joints are also set forth.

Tile for coating and decorating surfaces

Abstract: A tile for coating and decorating surfaces includes a slab which is of rigid material of light weight capable of adopting any polygonal shape having an even number preferrably four sides. Ribs extend peripherally around the slab perpendicular to the rear surface thereof. Two adjacent sides of the slab each have a pair of identical projections extending therefrom. The projections are centrally perforated. The two other adjacent sides of the slab each have a pair of female recesses for coupling with the lugs of adjacent slabs to form the coating. The rear surface is provided with reinforcement ribs, which form an air insulating chamber. A plate of insulating material is located on the edges of the ribs. The top surface of the slab is bevelled and is coated with a colored sheet and a thin coating made of transparent and waterproof material which protects the top surface.

Propagation constants of resonant waves on homogeneous, isotropic slab waveguides.

Abstract: A general graphical study of the complex valued propagation constants, defining the various types of TE waves that are resonant on optical thin-film (slab) waveguides, is presented. The dielectric constants of both the slab and its surroundings are allowed to take on all possible complex values. The corresponding waves are classified in to two general types: surface waves, with conductive losses only; and leaky waves, with both conductive and radiative losses.

Method for construction and erection of floor slabs

Abstract: The method of constructing and elevating a building floor slab which comprises the utilization of a frame in the center of the floor slab to which a plurality of sections, such as four sections, are hinged or flexibly connected and then moving the sections about their connection to the frame into a contracted position in plan view of the slab and then elevating the slab to the desired height and then expanding the slab and positioning it on the framework of the building and then subsequently elevating similar slabs by cables passing through the center frame of the slab as a hoistway to position additional slabs below the uppermost slab. In some cases the top slab may be used as a roof.

Composite end connection for steel joists

Abstract: A COMPOSITE ACTION JOIST END INTERCONNECTION WITH A SUPPORTING BEAM AND CARRYING A CONCRETE SLAB IS DESCRIBED AN OUTWARDLY-EXTENDING END PORTION OF THE TOP CHORD OF A STEEL JOITS IS PROVIDED AT THE UNDERSIDE WITH BEARING MEANS ADAPTED TO SEAT UPON AND BE SECURED TO THE SUPPORTING BEAM, WHEREBY, WHEN THE SUPPROTED CONCRETE SLAB IS POURED IN PLACE IN SUCH MANNER AS TO EXTEND OVER AND UPON THE SUPPORTING BEAM, THE JOIST END INTERCONNECTING THEREWITH IS ENCASED WITHIN THE SLAB CONCRETE TO EFFECT THE COMPOSITE ACTION BETWEEN THE SUPPORTING STEEL AND THE CONCRETE

Design of composite beams with formed metal deck

Abstract: THE AISC SPECIFICATION FOR BUILDINGS DOES NOT PROVIDE FOR COMPOSITE BEAMS WITH A FORMED METAL DECK BETWEEN THE STEEL AND CONCRETE SLAB. WHEN THE METAL DECK CORRUGATIONS ARE PARALLEL TO THE BEAM, THEY DO NOT INTERFERE WITH THE STEEL-CONCRETE INTERACTION AND THE CONDITION IS SIMILAR TO A HAUNCHED SLAB FOR WHICH THE SPECIFICATION PROVISIONS ARE APPLICABLE. HOWEVER, WHEN THE METAL DECK IS PLACED PERPENDICULAR TO THE STEEL BEAMS AND SHEAR CONNECTORS ARE PLACED IN THE RIBS OF THE CORRUGATIONS, THE BEHAVIOR OF THE COMPOSITE SYSTEM MAY DIFFER SUBSTANTIALLY FROM THE EXPECTED BEHAVIOR. STUDIES INDICATE THAT ALL CORRUGATIONS HAVE LITTLE OR NO INFLUENCE ON BEAM BEHAVIOR AND THAT BEAMS COULD BE DESIGNED AS THOUGH THE SLABS WERE SOLID. TESTS ON COMPOSITE BEAMS WITH RIBS UP TO 1 AND 1/2 INCH, ARE SUMMARIZED IN THE FIGURE. WITH INCREASING RIB HEIGHT, THE FLEXURAL CAPACITY OF THE BEAMS WAS DECREASED AS A RESULT OF THE REDUCTION IN SHEAR CONNECTION STRENGTH. THE REDUCTION IN FLEXURAL CAPACITY IS ANALOGOUS TO THE REDUCTION OBSERVED IN CONVENTIONAL COMPOSITE BEAMS WHEN PARTIAL SHEAR CONNECTION IS AVAILABLE. THIS REDUCED FLEXURAL CAPACITY CAN BE DETERMINED WHEN THE STRENGTH OF THE SHEAR CONNECTION IS KNOWN. THE SLAB WIDTH AND CONNECTOR SIZE AFFECT THE CONNECTORS STRENGTH. THE FLEXIBILITY OF THE SHEAR CONNECTOR HAS SOME EFFECT ON THE BEHAVIOR OF THE RIB AND ITS ABILITY TO RESIST SHEAR. TENTATIVE DESIGN RECOMMENDATIONS ARE PRESENTED FOR COMPOSITE BEAMS WITH FORMED METAL DECK UP TO 3 IN. HIGH.

Influence of metal plate on surface magnetostatic modes of magnetic slab

Abstract: The dispersion relationships for surface magnetostatic modes propagating in a ferrite slab with a conducting plate at a small distance parallel to the surface of the slab have been derived. It is shown that the group velocity of the surface magneto-static mode in this configuration can be both positive and negative, depending on the wavelength of the mode and the distance of the conducting plate from the ferrite surface.

The location and timing of deep slab avalanches

Abstract: Win ter o bservations in the n orthern R ocky M ounta ins of M onta na show two periods during which on e m ay expect a colla psing snowpack a nd accompa nying ava la nches: ( I ) shad ed a nd sh el tered a reas: DecemberFebrua ry; (2) sunny a nd exposed a reas: M a rchM ay. T hese periods ap pear to be linked in part to the cycl ic rise a nd fa ll of strength in the basa l snow layer. It is sugges ted that sh eltered slopes a re often a bou t a ha lf-cycl e ah ead of sunny slopes because sheltered slopes tend to reta in the ea rl y snows which la ter become the critica ll y weak basa l layer on th ese slopes. R EsuME. L a localisation dal1s I' espace et le temps des avalanches de plaques epaisses. L es observa tions fa ites en hiver da ns les R ocky M ounta ins du nord d e Monta na ont permis de constate r qu 'il existe d eux pe riodes a u COUl'S desq uell es on peut s'a ttendre it un effondrement d 'amas d e neige accom pagne d 'avala nches: ( I ) lieux ombrages e t a brites : decembrefevri er ; (2) li eux ensolei ll es et decouverts: ma rsm a i. Ces pe riodes sem blen t etre li ees en pa nie it l 'augmenta tion cycliq ue et it la perte d e force de la couche d e base d e la neige. Il est suggere q ue les pentes abritees on t souven t un d emi-cycle d'avance sur les pentes ensoleillees, pa rce q ue les pentes a britees tendent a re tenir les premieres neiges qui . p lus ta rd , fo rmen t la couche critiq uement fa ibl e su r ces pentes. ZUSAMMENFASSUNG. Vorkollllllen 1lI/.d Ablaiif tiifer Schlleebrell-Lawinen. vVinte rbeobachtungen in den nordlichen R ocky M ounta ins von M onta na lassen 2 Perioden erkennen, in den en ma n zusammenbrechende Schneeschichten und die sie begl eitenden L a winen erwarren kann: ( I) scha ttige und geschutzte Flachen : DezemberFebrua r ; (2) sonnige u nd ungeschutz te F lachen : M a rzM a i. Diese Period en scheinen zum Tei l m it d em zyklischen Zuund Abnehmen der Festigkeit in del' untersten Schneeschicht zusammenzuha ngen. Es wird a ngenommen . dass geschutz te Abha nge oft den sonnigen Abhangen urn ungefahr einen h alben Zyklus vera us sind, da geschu tz te Abha nge d azu neigen, den fruhfn Schnee zu bewahren, d er spa ter zur kritisch schwachen G rundschich t a uf diesen Abha ngen wird. I NTROD UCTION D eep slab avalanches a re here defin ed as those snow avalanches initiated by the sudden collapse of the basal layers of the snow pack under the overl ying snow load . As such , these avalanches would constitu te a genetic subtype under the Swiss classifica tion \" ground slab avala nche\" (Quervain , 1966) or the U. S. Forest Service \" climax avalanche\" ([U .S. D ept. of Agriculture. Fores t Service] , 196 1) . Two conditions at the base of the snowpack are worth y of note: ( I) A poorly sintered , low-densi ty basal layer which frequently di splays subhedra l to euhedral depth hoar crystals; (2) A pre-collapse basal streng th to load ratio (S/L) of < 4 where streng th is measured with the snow resistograph and load is taken wi th the Mt R ose snow sampler (Bradley and Bowles, 1967) . The resistograph is an instrument which plo ts a profil e of snow streng th as a function of d epth in the pack. T o obta in SIL, a resistogram is first taken to iden tify the position and streng th of the weakes t layer near the base . The M t R ose sampler is then used to obtain a m easure of the snow load overlying tha t weak layer. In this paper S/L is considered to be a general index of systemic strength . A collapsing snowpack, deep slab avalanches a nd S/L < 4 a re all considered to be indices of crit ical systemic weakness. D eep slab avalanches, though common in the northern R ocky Mountains of M ontana, a re by no means a universa l win ter phenom enon. In my 19 winters of observa tion in the Bozema n area , there have onl y been four I would class as years of widespread deep slab avalanches. On the other hand, it is also true that each year has revealed som e broad areas of slope which have d eveloped a t som e mom ent the general criti cal weakness leading to collapse a nd a valanche. These same slopes in other years might remain completely stable for the whole season or might achieve so littl e synchronization of weak zones that general failure never develops. 253 J OU R N AL OF G L AC 10LO GY This paper is concerned wi th two factors which help bring about synchronous basal weakness and collapse over b road a reas. These two factors are the systemic streng th cycle a nd the location of the first permanen t snows of winter. SYST EMIC STRENGT H CY CLES Observations in the Bridger Range of M ontana (Brad ley, 1966 ; Brad ley a nd Bowles, 1967) showed the possibility of estimating the susceptibili ty of the snowpack to collapse by obtaining the strength to load ratio a t the base of the pack. In addition , it was shown that while this ratio generally d ecreases as the season advances, i t is a lso subject to significant oscilla tions, proba bly as the resul t of the interplay between m etamorphic weakening and load consolida tion . Cyclic weakness of basal snow was a lso no ted by R och ( 1966) . Metamorphic weakening accompanied by accumula ting snow load ultimately m ay lead to compressional fa ilure of the basal layer. This m ay be sudden and accompa nied by snowpack fracture. More often , however, the pack appa rently subsides plastically. In ei ther case, the subsidence brings about a period of stability and basal consolida tion b efore m etamorphism

Meat analog apparatus

Abstract: An apparatus for continuously producing a slab of fibrous, meatlike product in which amorphous heat coagulable dough is forwarded from a hopper by converging conveyors which induce substantially unidirectional transverse distension of the dough which distended dough, upon being heated sufficiently to induce coagulation, is transformed into a meat-like slab of substantially parallel, bonded, fibers.

Slab heating method and apparatus

Abstract: A preheated slab of metal is moved through induction heating units to raise its temperature prior to rolling. Electric radiant heating devices are spaced along the slab before and after it passes through the induction heating units to maintain the elevated temperature of the slab by directing radiant heat toward the slab in an amount sufficient to compensate for heat loss from the slab to the atmosphere.

Concrete ceiling slab form installation and dome-supporting shore assembly therefor

Abstract: A supporting shore for a concrete ceiling slab, having a vertically and downwardly shiftable rotatable member which normally supports the adjacent truncated four corners of a quadrilaterally arranged group of four inverted generally rectangular pan-shaped slab-supporting domes and which, in the lowered and rotated position of the member, moves out of operative register with two of the four corners so as to release the other two corners for dome-removal purposes, while at the same time the shore continues to support the concrete ceiling slab until the latter has become fully hardened.