The tests were made on a Riehlé 100,000-lb. machine in the Experimental
Engineering Laboratory of Tulane University of Louisiana. The machine is
provided with a cast-iron beam for cross-bending tests. The distance
between supports was 12 ft. The method of support was as follows: Each
end of the beam was provided with a steel roller which rested on the
cast-iron beam of the testing machine, while above the roller, and,
directly under the beam tested, there was a steel plate 6 by 8 in. in
area and 1 in. thick. The area was sufficiently great to distribute the
load and prevent the shearing of the fibers of the wood. The head of the
Riehlé machine is 10 in. wide. A plate, 3/8 in. thick, 6 in. wide and 18
in. long, was placed between the head of the machine and the beam
tested.
[Illustration: FIG. 1.--DEFLECTON CURVES BEAM I]
[Illustration: FIG. 2.--DEFLECTON CURVES BEAM II]
TABLE 1.--SUMMARY OF RESULTS OF TRANSVERSE TESTS OF BEAMS AT TULANE
UNIVERSITY, FEBRUARY 10TH TO MARCH 2D, 1909.
Columns in table:
1. Number of beam.
2. Top or butt of log.
3. Width, in inches.
4. Height, in inches.
5. I = (bh^3)/12
6. Actual at elastic limit.
7. Maximum.
8. At elastic limit.
9. Maximum.
10. At elastic limit.
11. E = (Pl^3)/(48dI)
12. Weight, in pounds per cubic foot.
===========================================================================+
| | b | h | I | LOADS: |S = (Plc)/(4I) | d, |
| | | | | | |INCHES.|
| |------+-------+-------+-----------------+---------------+-------+
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
------+---+------+-------+-------+--------+--------+-------+-------+-------+
I | B | 6.28 | 15.94 | 2,120 | 22,000 | 45,900 | 2,975 | 6,200 | 0.41 |
I | T | 6.00 | 15.69 | 1,934 | 20,000 | 38,000 | 2,915 | 5,540 | 0.465 |
| | | | | | | | | |
II[A]| T | 6.37 | 15.81 | 2,098 | 20,000 | 43,450 | 2,722 | 5,918 | 0.380 |
II | B | 6.41 | 16.41 | 2,360 | 16,000 | 25,040 | 1,999 | 3,130 | 0.430 |
| | | | | | | | | |
III | T | 5.88 | 15.68 | 1,871 | 24,000 | 45,130 | 3,608 | 6,785 | 0.535 |
III | B | 5.88 | 15.90 | 1,965 | 21,000 | 35,190 | 3,054 | 5,120 | 0.515 |
| | | | | | | | | |
IV | T | 6.00 | 15.43 | 1,835 | 22,000 | 38,425 | 3,320 | 5,810 | 0.465 |
IV | B | 6.12 | 15.87 | 2,032 | 22,000 | 35,500 | 3,090 | 4,983 | 0.660 |
| | | | | | | | | |
V | B | 6.00 | 16.00 | 2,048 | 22,000 | 47,000 | 3,090 | 6,610 | 0.400 |
V[A]| T | 6.00 | 15.87 | 1,999 | 14,000 | 22,050 | 1,998 | 3,145 | 0.315 |
| | | | | | | | | |
VI[A]| B | 5.50 | 15.75 | 1,790 | 22,000 | 51,330 | 3,484 | 8,925 | 0.450 |
VI[A]| T | 5.87 | 15.62 | 1,865 | 20,000 | 44,000 | 3,013 | 6,627 | 0.410 |
| | | | | | | | | |
VII | B | 6.56 | 15.62 | 2,083 | 34,000 | 51,900 | 4,580 | 6,985 | 0.620 |
VII[A]| T | 6.22 | 15.62 | 1,975 | 20,000 | 49,000 | 2,845 | 6,970 | 0.380 |
===========================================================================+
[Footnote A: Failed in longitudinal shear.]
==============================================
E | |
| |
-----------+ |
11 | 12 | Remarks.
-----------+------+---------------------------
1,575,000 | 50.2 | } Close-grained pine,
1,383,000 | 47.5 | } long-leaf.
| |
1,562,000 | 40.5 | } Coarse loblolly,
979,000 | 42.2 | } large knots.
| |
1,489,000 | 40.4 | } Close-grained, long-leaf
1,288,000 | 44.2 | } no knots.
| |
1,601,000 | 40.8 | } Loblolly, with
1,017,000 | 41.5 | } knots.
| |
1,670,000 | 47.2 | } Long-leaf yellow
1,382,000 | 42.1 | } pine.
| |
1,695,000 | 50.2 | } Long-leaf yellow
1,625,000 | 45.2 | } pine.
| |
1,637,000 | 43.7 | } Long-leaf yellow
1,658,000 | 40.2 | } pine.
==============================================
The deflection was measured on both sides of each beam by using silk
threads stretched on each side from nails driven about 2 in. above the
bottom of the beam and directly over the rollers which formed the
supports. From a small piece of wood, tacked to the bottom of the beam
at its center and projecting at the sides, the distance to these threads
was measured. These measurements were taken to the nearest hundredth of
an inch. The mean of the deflections was taken as the true deflection
for any load.
[Illustration: FIG. 3.--DEFLECTON CURVES BEAM III]
[Illustration: FIG. 4.--DEFLECTON CURVES BEAM IV]
In computing the various quantities shown in Table 1, the summary of
results, the load has been assumed as concentrated at the center of the
beam. While it is true that the load was spread over a length of about
12 in., due to the width of the head of the machine and the plate
between it and the beam tested, it is also true that there were
irregularities, such as bolt-holes and, in some cases, abrasions due to
wear, that could not well be taken into account. Hence, it was deemed
sufficiently accurate to consider the load as concentrated. Besides the
horizontal bolt-holes, shown in the photographs, there were vertical
bolt-holes, at intervals in all the beams. The latter were 7/8 in. in
diameter, and in every case they were sufficiently removed from the
center of the length of the beam to allow the maximum moment at the
reduced section to be relatively less than that at the center of the
beam. For this reason, no correction was made for these holes. The
broken beams often showed that rupture started at, or was influenced by,
some of the holes, especially the horizontal ones.
While some of the heavy oils of a tarry consistency remained, they were
only to be found in the sappy portions of the long-leaf pine and in the
loblolly (Specimens II and IV). Exposure in a semi-tropical climate for
26 years had resulted in the removal of the more volatile portions of
the creosote oil. The penetration of the oil into the sap wood seemed to
be perfect, while in the loblolly it varied from a fraction of an inch
to 1-1/2 in. In the heart wood there was very little penetration across
the grain. The timber had been framed and the holes bored before
treatment. The penetration of the creosote along the grain from the
holes was often from 4 to 6 in.
Circular 39 of the Forest Service, U. S. Department of Agriculture,
entitled "Experiments on the Strength of Treated Timber," gives the
results of a great many tests of creosoted ties, principally loblolly
pine, from which the following conclusions are quoted:
"(1) A high degree of steaming is injurious to wood. The degree of
steaming at which pronounced harm results will depend upon the
quality of the wood and its degree of seasoning, and upon the
pressure (temperature) of steam and the duration of its
application. For loblolly pine the limit of safety is certainly 30
pounds for 4 hours, or 20 pounds for 6 hours." [Tables 3, 6, and
7.]
"(2) The presence of zinc chlorid will not weaken wood under static
loading, although the indications are that the wood becomes brittle
under impact." [Tables 3 and 4.]
[Illustration: FIG. 5.--DEFLECTON CURVES BEAM V]
[Illustration: FIG. 6.--DEFLECTON CURVES BEAM VI]
"(3) The presence of creosote will not weaken wood of itself. Since
apparently it is present only in the openings of the cells, and
does not get into the cell walls, its action can only be to retard
the seasoning of the wood." [Tables 3, 4, 5, and 6.]
[Illustration: FIG. 7.--DEFLECTON CURVES BEAM VII]