JNIOSH

Abstract of RIIS Report ( SH-1960-1 )

National Institute of Occupational Safety and Health, Japan

Report on the Load Tests of Steel Arch-Supports for Tunnelling

SH-1960-1-1
Yoshitada MORI

: The use of steel arch-supports in the tunnelling is increasing recently in Japan. This tendency is due to the fact that steal arch supports are superior to timberings from many view-points, in order to protect a person from the fall of roof of tunnel.
    These tests are a part of the writer's investigation, which is still continuing, on how to design and how to erect steel arch-supports.
    In this report eight full-sized load tests and sixteen model load tests of steel arch-supports for tunnelling are described.
    Each test support for full-sized load test consisted of three members which were jointed with yieldable joints to each other or welded to each other, a span of support being about 5 m, a hight of support being about 3.2 m, and a member section of support being V type and 24 kg/m or 20 kg/m in unit weight. The support was loaded at three or five points with oil jacks, the loads being normal to the arch line.
    In case of the non-yieldable arch-support with welding joints, the effects of two types of load were compared, in one of them five jacks were all active, while in the other three jacks were active and two jacks were passive. But there was no actual difference between them, for the support began to undergo the failure when plastic-hinge were formed at several points of the support in each case. It was also recognized in the case of non-yieldable support that the more the centrifugal displacements at loading points were allowed, the less the bearing power of the support became.
    In the case of yieldable support, it was found that the yieldable joint used in this test was more suitable for a member of 24 kg/m section than for that of 20 kg/m section, so that the support with 24 kg/m members sustained its yieldability unless the deformation of the support was not so much. The axial force on the section near a joint was between 10 ton and 15 ton while the support was yielding.
    In model load tests, test supports had members of V section, I section and rail section in a scale of one-fourth respectively, and each support consisted of a half circle of 0.7 m radius and two side legs of 0.7 m in height. The load on a support was a concentrated toad at the crown or one of other points of the arch, and directed to the center of the base of support.
    As a result obtained, a support with V section, which section-modulous-ratio Zx/Zy was smallest, was stronger than the one with any other section. A support with members of larger section-modulous-ratio tended to be laterally deformed.
    The findings described so far are considered to be right under the condition of these tests, but it will be necessary to test further supports under other conditions, in particular the investigation of the lateral buckling of arch-support is very important.

Measurement of Frictional Coefficient of Ingot-Tongs-Tips in Lifting Materials

SH-1960-1-2
E.AKIYAMA and T.HAKAMAZUKA

: The frictional coefficient of tongs-tips with various radius were measured with the experimental apparatus. We obtained the following result. The friction differed from the general idea, that is to say, the kinetic frictional force was larger than the conventional statical force under the same load, and the more the tip slided, the more the value rose. The statical frictional coefficient was in the range between 0.17 and 0.35. The radius of tip did not affect the value of the coefficient.

Shift-System Labor and its Burdens on the Living Body

SH-1960-1-3
C.GOTOH

: In order to make clear how the labor of shift system affects the living body and to establish the counter measures necessary for maintaining the health of workers by determining the rational form of labor, the writer conducted investigations as follows:
  1. Measurements of fatigue with Flicker test.
  2. Investigation of length of each part in the living hours.
  3. Efficiency, rate of absenteeism and accident rate.
  4. Investigation of attitude.
    As the result, the writer obtained the following findings:
  1. The debility increases in the order of 8 hr. day shift, 12 hr. day shift, 8 hr. might shift and 24 hr. labor.
  2. As the working hours, the commuting hours or both of them increase, the sleeping hours and the free hours are forced to decrease.
  3. There are correlations between the form of shift and the efficiency, the rate of absenteeism and the accident rate.
  4. If any shift form is continuously repeated, the worker tends to adapt himself to it and to become to feel less fatigue.

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