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NDT of cyclically loaded metal structures

K.I. Yeryomin
M.V. Nashchokin
Magnitogorsk State Academy of Mining and Metallurgy
Lenin av. 38
Magnitogorsk, 455000, Russia

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As a result of the studies carried out the most heavily loaded parts at the crane secondary truss supporting joint of the division of a continuous casting of steel have been found to be an upper tension flange at the conjugation place with the supporting diaphragm and the wall. The basic stress swing in the flange is Dsb1 = 0.36sy. A higher swing of the basic stresses is in a zone of a stiffening rib reinforced by a plate Dsb1 = 0.41sy, Dsb1 = 0.65sy.

With double-sided loading of CST supporting joint the level of stresses becomes 2.0-2.5 times higher. In the result of the processing of experimental studies data the following has been established: at the primary truss upper chords of the trussed transporter cranes tensile stresses vary from 0.1sy to 0.8 sy. Tensile stresses at the primary truss lower chords of the trussed transporter cranes vary from 0.04sy to 0.6sy when the span is being loaded.

The most heavily loaded members of the lattice are bearing diagonals at the rigid supports in which compressive stresses reach 0.6sy when the bracket on the side of the rigid support is being loaded. For the transporter crane with a composite system of the span the maximum values of the basic compressive stresses at the upper chord reach 0.7sy when loading directly a rigid support by a loaded trolley; basic tensile stresses reach 0.2sy when loading the bracket on the side of a flexible support. The maximum values of tensile stresses are at the points located at the crack encls 1.02sy and 0.7sy when loading the bracket on the side of a rigid support.

The most heavily loaded deck I-beams are the beams located in the middle of the lattice transporter crane bridges. These deck girders operate with the alternating load the stress reaching ±0.8sy. The basic compressive stresses reach the yield point when a loaded trolleyis located on the bracket on the side of the rigid support.

The maximum stresses at vertical diaphragm fixing angles are horizontal components of the normal stresses which lead to cracking at the pick. These angles are overstressed and deformed by the alternating loading. The experiment showed that a considerable reducing of stresses at the welded crack mouth did not take place. In the result of the experimental works performed on studying the state of stress and strain of the cyclically loaded metal structures it has been established:

References

  1. K.I. Yeryomin, S.A. Nischeta, M.V. Nashchokin. Study of the actual operation of cyclically loaded building metal structures. Magnitogorsk, 1996, 228 p,
  2. A.B. Zlochevsky. Experimental methods in building mechanics. Moscow: Stroyizdat, 1983, 192 p, [book]
  3. M.L. Daichik, N.I. Prigorovsky, G.H. Khurshudov. Methods and means of natural tensiometry. Reference book. Moscow: Mashinostroenie, 1989, 240 p, [book]

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