Joint Bars Research Articles

Analysis and tests of boned insulted rail joints subjected to vertical wheel loads

In traditional railroad tracks, joint bars are being used to connect the ends of adjoining rails. Because the vertical bending stiffness of two bars is generally much lower than of the rails, the passing wheels generate larger deflections in the joint region. This in turn leads to larger wheel forces caused by the dynamics of the passing vehicles and to accelerated track deterioration. In recent decades these expansion joints are being eliminated by the introduction of the continuously welded rails (CWRs). However, the retention of the automatic block signaling system created the need for electrically insulated joints is that the bending stiffness of the insulated joints bars is even smaller than of the non-insulated bars that are being eliminated. There are very few published analyses of joints in track; especilly of insulated joints. The purpose of this paper is to contribute to a better understanding of the mechanics of rail joints. At first an analysis is presented for the joint tests to be conducted. Then a test program is described that utilizes actual bonded joints. The obtained test results are then compared with the corresponding analytical results. The agreement is good. This confirms the validity of the assumed joint model and of the presented analysis. The paper concludes by analyzing the effect of a rail joints in a CWR track caused by a vertical wheel load.

引き抜き試験によるはり主筋の機械式定着耐力の評価

The mechanical anchorages of main bars in beam-column joints of reinforced concrete structures are tried to use in some construction systems. In these systems, the nuts with small flange which can be arranged at minimum required spacing are used as mechanical anchorages, but the design concept of the mechanical anchorage in reinforced concrete structures is not established yet. Ninety eight pull-out tests have already been carried out to clarify the development mechanism of the mechanical anchorage and to evaluate the ultimate anchorage capacities. The equation to predict the ultimate capacity of the mechanical anchorage is proposed in this paper. The predicted capacities agree with the experimental ones which were obtained in this experimental study or in previous experimental studies by other facilities.

Numerical analysis of a railroad bolt hole fracture problem

A finite element beam model was used to study the effects of joint bar looseness, rail height mismatch and train speed on the crack driving force for a crack emanating from a bolt hole in the web of a railroad rail. The model accounts for looseness by simulating gaps of varying sizes between rail and joint bars, while the effects of height mismatch were simulated by imposing an impulse to the end of one rail and using modal analysis to determine rail forces. The analysis shows that the crack driving force increases by about 25% as the joint loosens, primarily due to the increase in dynamic wheel load. The results also indicate that a rail height mismatch of 0.25 in. could cause fracture at train speeds as low as 10 mph, if the toughness of the rail steel is low.

Developments in HSLA steel products

The technology of microalloyed steels is expanding beyond its original emphasis on low-carbon, severely control-rolled strip and plate products. A variety of economical, high-strength, tough, as-rolled or as-forged microalloyed products are replacing more expensive heat-treated steels. Recrystallization-controlled rolling is being utilized to produce very fine ferrite grain sizes and good toughness in strip, plate and bar products processed with relatively high rolling temperatures. High-strength microalloyed long products such as railroad joint bars, truck frame rails and flat bars for truck trailer construction are replacing heat-treated parts. Microalloyed, medium-carbon forging steels are used extensively for automobile engine and suspension components. Fully pearlitic high-carbon rods are being microalloyed to enhance the properties of wire and springs.

Slip of Steel Bars in Concrete Joints Under Cyclic Loading

A closed form solution for predicting the generalized slip response of reinforcing steel bars anchored inside beam-column joints is presented. It allows computation of bond stresses, steel stresses, and slip distribution along the bar anchorage length under given generalized steel stresses at the boundaries. The solution takes advantage of some theoretical and experimental observations regarding the bond and steel stress characteristics inside a beam-column joint. The main features of the proposed model is that it depends only on the monotonic ascending portion of the local bond stress-slip relationship of the reinforcing bar, and it bypasses the definition of its local bond stress-slip relationship under severe slip reversals. Results predicted by the model are found to be in good agreement with experimental results and finite element predictions.

鉄筋コンクリート部材における付着劣化過程の解析的研究 : (その1)解析モデル,解析手法,解析例

This paper describes a theoretical investigation into the hysteretic behavior of end hinges in reinforced concrete members under the influence of bond deterioration processes of main bars. End hinges and adjacent embedment regions in reinforced concrete members wer represented by mathematical models which consisted of steel elements, concrete fiber elements and bond links. Hysteresis rules for stress-strain relations of materials and bond strees-slip relations of link elements were postulated. Then, the equilibrium condition of section forces in a hinge was iteratively gained. Slippage of bars in beam column joints and bond splitting failures of reinforced concrete columns were studied.

Joint Bar Association Proposal for Canadian-U.S. Dispute Settlement

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Anchorage Behavior Of 90-degree Hooked BeamBars In Reinforced Concrete Knee Joints

Beam bars of reinforced concrete structures are usually anchored with 90-degree hooks in exterior beam-column joints. However, there have been far fewer studies on the anchorage behavior of 90-degree hooked-bar than on straight-bar anchorage. In our previous paper, we divided the anchorage failure of 90-degree hooked bars in exterior beam-column joints in a middle storey in a building into three modes: side split failure; local compression failure; and raking-out failure, in which a concrete block, approximating the inside dimensions of the hooked bar in size, is raked out toward the beam side of the column due to the presence of many beam bars and/or to short development length within the joint. The purpose of this paper was to clarify the anchorage performances on the raking-out failure mode of beam top-bars with 90-degree hooks arranged in an exterior beam-column joint in the roof story of a building. Fifteen specimens of knee joints with various arrangements of L-shaped beam bar anchorage and various material properties, were subjected to pull-out loading on the beam top-bars. From the experimental results, we were able to conclude that: (1) the anchorage mechanism depends on stress transmission from the tail portion of the beam bar hooks to the adjacent column bars in a joint and that the anchorage mechanism in a knee joint was quite different from that in a exterior beam-column joint in a middle story; (2) the main factors in influencing anchorage strength are tail length, horizontal distance between tail and column bars and between tail bars and the beam end, lateral reinforcement ratio within the joint and concrete strength; and (3) accurate estimation of anchorage strength can be obtained by taking into account the influence of the above mentioned factors.

Impulsive Motion of a System

In an article entitled “Two Problems on Impulsive Motion” (M. G., XLIV, p. 95) the writer (J. O’Keeffe) complains of the lack of method in elementary books on problems such as the initial motion of two jointed bars under the action of an impulse. In our view, such problems are best treated, in an elementary course, by reducing the total momentum of the system to a single linear momentum and a momentum-couple. The necessary equations are then obtained by using the principle of equivalence of this system with that of the impulses. This treatment makes it clear why and in what form it is correct to take moments about the point at which the bars are hinged. Below we give the general treatment, and also the application to this particular problem.

Die technische Mechanik: elementares Lehrbuch für mittlere maschienentechnische Fachschulen und Hilfsbuch für studierende höherer technischer Lehranstalten

IN the very early part of this excellent work there is a certain lack of system, inasmuch as, although the author very properly treats first of the equilibrium of a particle, he assumes the nature of the stress exerted in such rigid bodies as the bars of a framework, the crank and connecting rod of an engine, &c. The nature of such forces is never properly appreciated by the student who is truly a beginner in the subject of dynamics—and, indeed, there is no part of statics in which students of even very considerable experience are so apt to go wrong as that relating to the forces exerted by jointed bars. The author treats from the outset the equilibrium of forces acting in space of three dimensions without having previously disposed of the simpler two dimensional case, a course which meets with the approval of many teachers, although it seems to the reviewer to be the less simple method. Herr Stephan enunciates the parallelogram law for the composition of forces (or vectors generally) at the outset, and assumes it as a result of experiment—which, on the whole, is perhaps the wisest plan for a teacher. Near the end of the book, however, he gives the ordinary Newtonian proof of the proposition. Die technische Mechanik: elementares Lehrbuch für mittlere maschienentechnische Fachschulen und Hilfsbuch für studierende höherer technischer Lehranstalten. By P. Stephan, &c. Erster Teil: Mechanik Starrer Körper. Pp. viii + 344. (Leipzig: Teubner, 1904.) Price 7 marks.

Note on the Kinematics of a Quadrilateral

I send a note on the following problem, a solution of which was requested of me by one of the tutors at King's College, Cambridge.We are given a quadrilateral of four jointed bars ABCD (fig. 83). The bar CD being held fast, find the tangent to the locus of P, the intersection of DA, CB in any position; and verify the following construction for the radius of curvature of the path of P:—Let PQ be the third diagonal, draw through P a perpendicular to PQ meeting BA, CD in L and L′; through L and L′ draw parallels to PQ meeting AD in M and M′; through M and M′ draw perpendiculars to AD meeting the normal at P in O and O′; then will