Slab

About: Slab is a research topic. Over the lifetime, 31617 publications have been published within this topic receiving 318693 citations.

Ultimate Load Test of Slab‐on‐Girder Bridge

Abstract: An ultimate load test on a short-span simply supported bridge having six rolled-steel girders and a noncomposite deck slab is described. The main conclusions drawn from the test are as follows: (1) The bearing restraint forces reduced the bending moment at midspan by a minimum of 11%; (2) the transverse load distribution pattern of the bridge improves by a relatively small margin as the ultimate limit state is approached; (3) any composite action between the deck slab and a girder that may exist at service loads, and is due only to bond or friction between steel and concrete, completely breaks down as the load approaches the failure load for the girder; and (4) a girder continues to carry loads long after the formation of first yield.

Assay apparatus having piezoelectric slab generating effective diffraction grating in applied analyte-specific film

Abstract: A method and apparatus for assaying a species in a biological sample fluid. The apparatus comprises an SAW device (1) comprising a slab (2) of piezoelectric material on the upper surface (5) of which is formed an input transducer (3) and an output transducer (4). A source of RF energy is applied to the input transducer to generate a surface acoustic wave. Applied to the surface (5) is a thin layer (8) of a material capable of binding a species to be assayed. The sample (13) to be tested is applied to the top of the layer (8). A collimated light beam (1) from a source (9) is applied to the thin film from underneath the slab (2) and is collected by a photodetector (12). When the slab (2) is energized, the vibration sets up an effective diffraction grating which is coupled to the thin film and acts to diffract the light beam (10) applied to it. The energy in the diffracted beam, as measured by the photodetector ( 12), is indicative of the progress and result of the reaction between the layer 8 and the sample.

Computation of stresses in concrete roads

Abstract: COMPUTATION OF STRESSES IN CONCRETE ROADS MAY BE OBTAINED BY ASSUMING THE SLAB TO ACT AS A HOMOGENEOUS ISOTROPIC ELASTIC SOLID IN EQUILIBRIUM AND BY ASSUMING THE REACTIONS OF THE SUBGRADE TO BE VERTICAL ONLY AND TO BE PROPORTIONAL TO THE DEFLECTIONS OF THE SLAB. WITH THESE ASSUMPTIONS, THE ANALYSIS IS REDUCED TO A PROBLEM OF MATHEMATICAL THEORY OF ELASTICITY. THE REACTION OF THE SUBGRADE PER UNIT OF AREA AT ANY GIVEN POINT IS EXPRESSED AS A COEFFICIENT CALLED THE MODULUS OF SUBGRADE TIMES THE DEFLECTION AT THE POINT. THIS COEFFICIENT IS A MEASURE OF THE STIFFNESS OF THE SUBGRADE. A FORMULA IS GIVEN FOR THE RADIUS OF RELATIVE STIFFNESS. USING THESE MATHEMATICAL FORMULAS AND RELATIONSHIPS, THREE CASES OF LOADING WERE INVESTIGATED. THESE CASES ARE: (1) A WHEEL LOAD ACTS CLOSE TO A RECTANGULAR CORNER OF A LARGE PANEL OF THE SLAB, (2) THE WHEEL LOAD IS AT A CONSIDERABLE DISTANCE FROM THE EDGES, AND (3) THE WHEEL LOAD IS AT THE EDGE, BUT AT A CONSIDERABLE DISTANCE FROM ANY CORNER. THE QUESTION OF BALANCED DESIGNS FOR THE THREE CASES OF LOADING ARE ANALYZED AND TESTED BY THE USE OF TABLES. DEFLECTIONS ARE MATHEMATICALLY DETERMINED WHICH ARE DUE TO MORE THAN ONE WHEEL. TABLES ARE GIVEN FROM WHICH CORRESPONDING CRITICAL STRESSES MAY BE COMPUTED. CERTAIN INFLUENCES WERE LEFT OUT OF CONSIDERATION WHEN USING TABLES AND DIAGRAMS, ESPECIALLY THE FOLLOWING: (1) VARIATIONS OF TEMPERATURE, AND OTHER CAUSES FOR TENDENCY TO CHANGE VOLUME, (2) THE GRADUAL DIMINISHING OF THE THICKNESS FROM THE EDGE TOWARD THE INTERIOR, (3) LOCAL SOFT OR HARD SPOTS IN THE SUBGRADE, (4) HORIZONTAL COMPONENTS OF THE REACTIONS OF THE SUBGRADE, AND (5) THE DYNAMIC EFFECT, EXPRESSED IN TERMS OF THE INERTIA OF THE PAVEMENT AND SUBGRADE. THE HORIZONTAL COMPONENTS OF THE REACTIONS OF THE SUBGRADE, WHICH ARE DUE TO FRICTION, MAY HAVE A STRENGTHENING INFLUENCE, ESPECIALLY AT SOME DISTANCE FROM THE EDGES, BY CAUSING A DOME ACTION IN THE PAVEMENT. WITH KNOWN VALUES OF THE MAXIMUM PRESSURE DEVELOPED BETWEEN THE TIRE AND THE PAVEMENT, THE EFFECT OF THE INERTIA OF THE PAVEMENT MAY POSSIBLY BE EXPRESSED APPROXIMATELY IN TERMS OF AN INCREASED VALUE OF THE MODULUS OF SUBGRADE REACTION.

The 1977 Sumba earthquake series: Evidence for Slab pull force acting at a subduction zone

Abstract: The great 1977 Sumba earthquake occurred at the eastern Sunda trench, just west of the collision of Australian continental lithosphere with the island arc. The length of the aftershock zone of this normal-faulting earthquake is about 200 km. Aftershocks are concentrated 65–115 km east of the main shock epicenter, with very few aftershocks in a 50-km-long segment that spans the main shock epicenter. Relocated hypocenters and focal mechanism data are consistent with normal faulting throughout the upper 28 km of the oceanic lithosphere. There is no evidence for thrust faulting of the deeper aftershocks. These data imply that the neutral bending surface must be at least 35–40 km deep. A second aftershock zone, about 180 km northwest of the main shock, became active immediately following the main shock, but events were concentrated during days 50–52. This zone is a 70-km-long lineation that trends toward the main shock epicenter and reflects right-lateral, strike-slip faulting within the subducted oceanic plate. Seismicity exists to a depth of about 650 km in the very old plate beneath the Sunda-Banda arc, and that plate's negative buoyancy causes very large slab pull forces. Great interface thrust earthquakes are absent at the Sumba region, and slab pull forces are inferred to have partially decoupled the subducted plate from the overriding plate. This decoupling permits slab pull stresses to be guided updip to the region of the Sumba main shock. Such shallow-acting slab pull provides a bending moment at the trench and explains the deformation and timing observed for the entire Sumba earthquake series. In this model, slab pull forces stretch the subducted plate until the increasing stresses at the shallow subduction zone lead to a subduction zone earthquake. Postseismically, the released oceanic plate undergoes a pulse of downdip strain, returning the plate to a less extended state. The moment of this downdip plate motion could exceed the seismic moment of the main shock.