End Bearing Research Articles

Strength of Lapped Splices in Reinforced Concrete Columns

Results of 51 tests on full scale columns with main reinforcement lap-spliced are presented. Difficulties in evaluating the strength of these specimens led to the development of an alternative method of calculation based on the stress-strain relationship for the concrete. The contribution of the end bearing of the reinforcement is evaluated, and the influence of splice length, concrete strength, and positioning of ties on splice strength is discussed. It is shown that bond strength and end bearing strength may each be regarded as the sum of two components, one related to bursting force and the other to concrete strength. A new type of bond test is used to show that more heavily ribbed bars develop greater average bond stresses. /Author/

On the Continuous Monitoring of Oil-Film Thickness in an Engine Bearing

This paper describes research involving the measurement of oil-film thickness in a large end bearing of a medium-sized medium-speed marine diesel engine. The design of the transducer and its novel signal conditioning circuitry is discussed. Comparisons are made between the measured results and numerical predictions.

Proposed ACI Standard: Standard Specification for End Bearing Drilled Piers

Proposed ACI Standard: Standard Specification for End Bearing Drilled Piers

On the Continuous Temperature Monitoring of an Engine Bearing

Measurements of bearing surface temperature were made in a large end bearing of a marine diesel engine, the data being communicated by a mechanical linkage attached to the connecting rod. The engine was run with the lubricating oil heavily diluted with fuel oil, and also with a variety of load conditions on the test cylinder. Some observations were made immediately after a rapid start in order to assess the effects of priming of the lubrication system. The observations are discussed and some qualitative conclusions drawn.

Correlations between cone resistance and vane shear strength in some Scandinavian soft to medium stiff clays: Discussion

The writers thank Ladanyi and Vogan for their interesting discussions, and in particular for adding their field measurements to the data given in the paper. The results reported by Ladanyi are important since they present reasonably long term measurements of socket base stresses. The results show that even in fractured rock the load distribution ratio between the end bearing and bond components of stress support the findings of Osterberg and Gill (1973) as shown on their Figs. 1 and 2. Vogan raises the possibility that load transfer to the socket base may be stress dependent;

Friction and end bearing tests on bedrock for high capacity socket design: Reply

Rock sockets are used to transfer axial loads to bedrock by a combination of periferal contact bond and end bearing. The load distribution with embedded depth in relation to rock properties actually measured is discussed. Case histories are presented.The results of full scale and bearing and friction tests carried out on various rock types are given. A relation between the unconfined compression strength of rock and the developed concrete to rock bond value is reported.

Friction and end bearing tests on bedrock for high capacity socket design

Rock sockets are used to transfer axial loads to bedrock by a combination of periferal contact bond and end bearing. The load distribution with embedded depth in relation to rock properties actually measured is discussed. Case histories are presented.The results of full scale and bearing and friction tests carried out on various rock types are given. A relation between the unconfined compression strength of rock and the developed concrete to rock bond value is reported.

Design of externally pressurised gas-lubricated porous journal bearings

Design charts for the evaluation of the performance characteristics of externally pressurized, porous gas bearings under static loading are presented for a wide range of parameters for direct use in practice. The theoretical results are obtained from a rigorous analysis by simultaneous solution of the continuity equation (derived from Darcy's law) and the modified Reynolds' equation satisfying the boundary conditions of sealed end bearings. The effect of the feeding parameter on static behaviour is discussed. Finally, a design procedure of one such bearing is described.

Derivation and Scope of the Dunkerley Equation

Dunkerley's equation is derived from Raleigh's principle and is shown to hold well under certain conditions for the fundamental mode of vibration, but not at all for the higher modes. This is checked by exact solutions for the cantilever with end load and for a shaft bearing a central load and held in pin-type end bearings. For the loaded cantilever, equations are given for the motion produced by a shock applied either to the base of the cantilever or to the end load.

Changes in the structure and composition of automobile big-end bearing materials and their relation to bearing failure

Changes in the composition and structure of automobile big end bearings during operation were examined by X-ray diffraction and electron probe X-ray microanalysis. It was found that evolution of heat and severe plastic flow of the surface layer caused diffusion of Sn into Cu, resulting in the formation of intermetallic compounds such as ε-Cu 3Sn. Similar changes were obtained by heating an unused bearing at 170°C for 120 h. It is suggested that the formation of intermetallic compounds such as ε-Cu 3Sn is a contributory factor in bearing failure.

Discussion of “Performance of Four Foundations on End Bearing Piles”

Discussion of “Performance of Four Foundations on End Bearing Piles”

Discussion of “Performance of Four Foundations on End Bearing Piles”

THE AUTHORS HAVE PRESENTED A CONSIDERABLE AMOUNT OF INTERESTING SETTLEMENT AND PORE PRESSURE DATA FOR PILE FOUNDATIONS. THE PILE-GROUP SETTLEMENT DATA ARE PARTICULARLY INTERESTING BECAUSE OF THE OPPORTUNITY TO COMPARE THE MEASURED VALUES WITH VALUES PREDICTED THEORETICALLY. ANALYSES RELATING PILE-GROUP AND SINGLE-PILE SETTLEMENTS HAVE BEEN DESCRIBED BY POULOS FOR INCOMPRESSIBLE FRICTION AND END-BEARING GROUPS. IN THESE ANALYSES, THE GROUP-PILE AND SINLE-PILE SETTLEMENTS ARE RELATED BY SUPER POSITION OF INTERACTION FACTORS FOR TWO PILES: THE INTERACTION FACTOR, ALPHA, BEING THE INCREASE IN SETTLEMENT DUE TO THE SECOND PILE AS A FRACTION OF THE SINGLE PILE SETTLEMENT. FACTOR ALPHA IS A FUNCTION PRIMARILY OF THE LENGTH-TO-DIAMETER RATIO, THE PILE SPACING RELATIVE TO THE DIAMETER, AND THE COMPRESSIBILITY OF THE PILE RELATIVE TO THE SOIL, EXPRESSED AS THE PILE STIFFNESS FACTOR K, WHICH FOR A SOLID-PILE SECTION IS THE RATIO OF THE MODULUS OF THE PILE TO THAT OF THE SOIL. ALTHOUGH GROUPS IN RELATIVELY SQUARE ARRAYS HAVE BEEN CONSIDERED, THE EXACT CONFIGURATION OF THE PILE WITHIN THE GROUP HAS LITTLE EFFECT ON THE GROUP SETTLEMENT, ESPECIALLY FOR GROUPS CONTAINING LARGER NUMBERS OF PILES. THE COMPUTER RELATIONSHIP BETWEEN SETTLEMENT AND GROUP SIZE, TOGETHER WITH THE AUTHORS MEASURED VALUES, IS SHOWN IN FIG. 14. BECAUSE OF THE CONSIDERABLE SCATTER IN THE MEASURED VALUES, A LINEAR REGRESSION LINE HAS BEEN CALCULATED FOR THESE VALUES AND IS ALSO SHOWN IN FIG. 14. IT CAN BE SEEN THAT THE AGREEMENT BETWEEN THE COMPUTER AND MEASURED SETTLEMENTS IS SUFFICIENTLY GOOD TO SUGGEST THAT THE THEORETICAL ANALYSIS IS CAPABLE OF PROVIDING A REASONABLE MEANS OF PREDICTING GROUP SETTLEMENTS FROM A KNOWLEDGE OF THE SINGLE-PILE SETTLEMENT. /DISCUSSER/

Discussion of “Performance of Four Foundations on End Bearing Piles”

Discussion of “Performance of Four Foundations on End Bearing Piles”

Performance of Four Foundations on End Bearing Piles

The performance of four buildings each supported on end bearing concrete-filled pipe piles is evaluated. The piles were driven through a deep deposit of soft clay and are end-bearing in stiff glacial till and weathered shale. The paper presents measurements of building settlement, pile tip settlement of both test piles and foundation piles, pore pressures induced by the pile driving, and movements of adjacent buildings on shallow foundations caused by pile driving. The pile-supported buildings settled less than 0.5 in. The main conclusions from the study are: (1) The pile design load is controlled by tip punching considerations, because the settlement of the pile tip is small until the tip-bearing capacity is approached; (2) preaugering is effective in reducing pore pressures induced by the pile driving; and (3) even with preaugering, pile driving in soft clay can cause significant movement of adjacent buildings at distances up to 50 ft.

Closure to “End Bearing and Skin Friction Resistance of Piles”

Closure to “End Bearing and Skin Friction Resistance of Piles”

Discussion of “End Bearing and Skin Friction Resistance of Piles”

Discussion of “End Bearing and Skin Friction Resistance of Piles”

End Bearing and Skin Friction Resistance of Piles

A device with which it is possible to separate the point resistance from the total bearing capacity by measuring the compression of the lower part of a test pile is described. This method has been used extensively in Sweden during the last three years. Results from a load test with a driven reinforced concrete pile in which the new device has been used indicate that the skin friction resistance can be calculated from the undrained shear strength of the surrounding cohesive soil. The test results also indicate that the point resistance can be estimated from the stress wave equation.

On the Critical Speeds of a Continuous Shaft-Disk System

The effect of gyroscopic moments on the critical speeds of a shaft-disk system mounted in short end bearings is investigated. Representation of the shaft as having continuously distributed mass and elasticity allows accurate determination of higher critical speeds. Frequency equations are obtained for the critical speeds associated with both backward and forward whirling modes. The first four critical speeds (backward and forward whirling modes) are given for a range of shaft and disk sizes and for various disk locations on the shaft. Experimental verification is given for the first and second critical speeds.

Horizontally Curved Steel Girders; Fabrication and Design

The use of horizontally curved steel girders in bridge construction is relatively new. In 1961 there were probably not more than half a dozen bridges built with curved girders. In the American Bridge Div. of U. S. Steel Corporation, total inquiries for bridges using curved girders had only amounted to approximately 1,500 tons by the end of 1965. However, in 1966 alone inquiries amounted to more than 1,600 tons. These guidelines are based on the supposition that misalignment between the span and the abutments can be tolerated. If not, the bearing devices must act in a plane tangent to the curve at the end bearing, and the effect of restricted movement must be considered in the design of the span and the bearings. As knowledge is further developed on the design and fabrication of curved girders, they will become more and more commonplace as highway bridge structures which fit particular locations as economically and esthetically as possible.

Reinforced Masonry Bearing Walls and Prestressed Slabs For High-Rise Construction

FOUNDATIONS Park Mayfair East contains 126 luxury-type apartments and has perimeter underground parking at the base of the tower. The foundation for this building consists of drilledshaft caissons varying in diameter from 12 in. up to 48 in. These caissons were drilled into the Denver formation, and a combination of end bearing and side shear on the caissons resists the vertical load of the building. Concrete walls 12 in. thick bear upon the caissons and extend to the first floor to form a beam support for the reinforced masonry bearing walls above the first floor. These 12in. concrete walls also carry the twin-tee slabs of the first floor.