Chapter IX: Appendix: Sample Working Plan of the U.s. Forest Service

MECHANICAL PROPERTIES OF WOODS GROWN IN THE UNITED STATES

Working Plan No. 124

PURPOSE OF WORK

It is the general purpose of the work here outlined to provide:

(_a_) Reliable data for comparing the mechanical properties of various species;

(_b_) Data for the establishment of correct strength functions or working stresses;

(_c_) Data upon which may be based analyses of the influence on the mechanical properties of such factors as:

Locality;

Distance of timber from the pith of the tree;

Height of timber in the tree;

Change from the green to the air-dried condition, etc.

The mechanical properties which will be considered and the principal tests used to determine them are as follows:

Strength and stiffness--
Static bending;
Compression parallel to grain;
Compression perpendicular to grain;
Shear.

Toughness--
Impact bending;
Static bending;
Work to maximum load and total work.

Cleavability--
Cleavage test.

Hardness--
Modification of Janka ball test for surface hardness.

MATERIAL

_Selection and Number of Trees_

The material will be from trees selected in the forest by one qualified to determine the species. From each locality, three to five dominant trees of merchantable size and approximately average age will be so chosen as to be representative of the dominant trees of the species. Each species will eventually be represented by trees from five to ten localities. These localities will be so chosen as to be representative of the commercial range of the species. Trees from one to three localities will be used to represent each species until most of the important species have been tested.

The 16-foot butt log will be taken from each tree selected and the entire merchantable hole of one average tree for each species.

_Field Notes and Shipping Instructions_

Field notes as outlined in Form--_a_ Shipment Description, Manual of the Branch of Products, will be fully and carefully made by the collector. The age of each tree selected will be recorded and any other information likely to be of interest or importance will also be made a part of these field notes. Each log will have the bark left on. It will be plainly marked in accordance with directions given under Detailed Instructions. All material will be shipped to the laboratory immediately after being cut. No trees will be cut until the collector is notified that the laboratory is ready to receive the material.

DETAILED INSTRUCTIONS

_Part of Tree to be Tested_

(_a_) For determining the value of tree and locality and the influence on the mechanical properties of distance from the pith, a 4-foot bolt will be cut from the top end of each 16-foot butt log.

(_b_) For investigating the variation of properties with the height of timber in the tree, all the logs from one average tree will be used.

(_c_) For investigating the effect of drying the wood, the bolt next below that provided for in (_a_) will be used in the case of one tree from each locality.

_Marking and Grouping of Material_

The marking will be standard except as noted. Each log will be considered a "piece." The piece numbers will be plainly marked upon the butt end of each log by the collector. The north side of each log will also be marked.

When only one bolt from a tree is used it will be designated by the number of the log from which it is cut. Whenever more than one bolt is taken from a tree, each 4-foot bolt or length of trunk will be given a letter (mark), _a, b, c,_ etc., beginning at the stump.

All bolts will be sawed into 2-1/2" X 2-1/2" sticks and the sticks marked according to the sketch, Fig. 50. The letters _N, E, S,_ and _W_ indicate the cardinal points when known; when these are unknown, _H, K, L,_ and _M_ will be used. Thus, _N5, K8, S7, M4_ are stick numbers, the letter being a part of the stick number.

Only straight-grained specimens, free from defects which will affect their strength, will be tested.

_Care of Material_

No material will be kept in the bolt or log long enough to be damaged or disfigured by checks, rot, or stains.

_Green material_: The material to be tested green will be kept in a green state by being submerged in water until near the time of test. It will then be surfaced, sawed to length, and stored in damp sawdust at a temperature of 70°F. (as nearly as practicable) until time of test. Care should be taken to avoid as much as possible the storage of green material in any form.

_Air-dry material_: The material to be air-dried will be cut into sticks 2-1/2" X 2-1/2" X 4'. The ends of these sticks will be paraffined to prevent checking. This material will be so piled as to leave an air space of at least one-half inch on each side of each stick, and in such a place that it will be protected from sunshine, rain, snow, and moisture from the ground. The sticks will be surfaced and cut to length just previous to test.

_Order of Tests_

The order of tests in all cases will be such as to eliminate so far as possible from the comparisons the effect of changes of condition of the specimens due to such factors as storage and weather conditions.

The material used for determining the effect of height in tree will be tested in such order that the average time elapsing from time of cutting to time of test will be approximately the same for all bolts from any one tree.

_Tests on Green Material_

The tests on all bolts, except those from which a comparison of green and dry timber is to be gotten, will be as follows:

_Static bending_: One stick from each pair. A pair consists of two adjacent sticks equidistant from the pith, as _N_7 and _N_8, or _H_5 and _H_6.

_Impact bending_: Four sticks; one to be taken from near the pith; one from near the periphery; and two representative of the cross section.

_Compression parallel to grain_: One specimen from each stick. These will be marked "1" in addition to the number of the stick from which they are taken.

_Compression perpendicular to grain_: One specimen from each of 50 per cent of the static bending sticks. These will be marked "2" in addition to the number of the stick from which they are cut.

_Hardness_: One specimen from each of the other 50 per cent of the static bending sticks. These specimens will be marked "4."

_Shear_: Six specimens from sticks not tested in bending or from the ends cut off in preparing the bending specimens. Two specimens will be taken from near the pith; two from near the periphery; and two that are representative of the average growth. One of each two will be tested in radial shear and the other in tangential shear. These specimens will have the mark "3."

_Cleavage_: Six specimens chosen and divided just as those for shearing. These specimens will have the mark "5." (For sketches showing radial and tangential cleavage, see Fig. 45.)

When it is impossible to secure clear specimens for all of the above tests, tests will have precedence in the order in which they are named.

_Tests to Determine the Effect of Air-drying_

These tests will be made on material from the adjacent bolts mentioned in "_c_" under Part of Tree to be Tested. Both bolts will be cut as outlined above. One-half the sticks from each bolt will be tested green, the other half will be air-dried and tested. The division of green and air-dry will be according to the following scheme:

STICK NUMBERS

Lower bolt, 1, 4, 5, 8, 9, } Tested etc. } green Upper bolt, 2, 3, 6, 7, 10, }

Lower bolt, 2, 3, 6, 7, 10, } Air-dried etc. } and Upper bolt, 1, 4, 5, 8, 9, } tested

All green sticks from these two bolts will be tested as if they were from the same bolt and according to the plan previously outlined for green material from single bolts. The tests on the air-dried material will be the same as on the green except for the difference of seasoning.

The material will be tested at as near 12 per cent moisture as is practicable. The approximate weight of the air-dried specimens at 12 per cent moisture will be determined by measuring while green 20 per cent of the sticks to be air-dried and assuming their dry gravity to be the same as that of the specimens tested green. This 20 per cent will be weighed as often as is necessary to determine the proper time of test.

_Methods of Test_

All tests will be made according to Circular 38 except in case of conflict with the instructions given below:

_Static bending_: The tests will be on specimens 2" X 2" X 30" on 28-inch span. Load will be applied at the centre.

In all tests the load-deflection curve will be carried to or beyond the maximum load. In one-third of the tests the load-deflection curve will be continued to 6-inch deflection, or till the specimen fails to support a 200-pound load. Deflection readings for equal increments of load will be taken until well past the elastic limit, after which the scale beam will be kept balanced and the load read for each 0.1-inch deflection. The load and deflection at first failure, maximum load and points of sudden change, will be shown on the curve sheet even if they do not occur at one of the regular load or deflection increments.

_Impact bending_: The impact bending tests will be on specimens of the same size as those used in static bending. The span will be 28 inches.

The tests will be by increment drop. The first drop will be 1 inch and the increase will be by increments of 1 inch till a height of 10 inches is reached, after which increments of 2 inches will be used until complete failure occurs or 6-inch deflection is secured.

A 50-pound hammer will be used when with drops up to 68 inches it is practically certain that it will produce complete failure or 6-inch deflection in the case of all specimens of a species. For all other species, a 100-pound hammer will be used.

In all cases drum records will be made until first failure. Also the height of drop causing complete failure or 6-inch deflection will be noted.

_Compression parallel to grain_: This test will be on specimens 2" X 2" X 8" in size. On 20 per cent of these tests load-compression curves for a 6-inch centrally located gauge length will be taken. Readings will be continued until the elastic limit is well passed. The other 80 per cent of the tests will be made for the purpose of obtaining the maximum load only.

_Compression perpendicular to grain_: This test will be on specimens 2" X 2" X 6" in size. The bearing plates will be 2 inches wide. The rate of descent of the moving head will be 0.024 inch per minute. The load-compression curve will be plotted to 0.1 inch compression and the test will then be discontinued.

_Hardness_: The tool shown in Fig. 43 (an adaptation of the apparatus used by the German investigator, Janka) will be used. The rate of descent of the moving head will be 0.25 inch per minute. When the penetration has progressed to the point at which the plate "_a_" becomes tight, due to being pressed against the wood, the load will be read and recorded.

Two penetrations will be made on a tangential surface, two on a radial, and one on each end of each specimen tested. The choice between the two radial and between the two tangential surfaces and the distribution of the penetrations over the surfaces will be so made as to get a fair average of heart and sap, slow and fast growth, and spring and summer wood. Specimens will be 2" X 2" X 6".

_Shear_: The tests will be made with a tool slightly modified from that shown in Circular 38. The speed of descent of head will be 0.015 inch per minute. The only measurements to be made are those of the shearing area. The offset will be 1/8 inch. Specimens will be 2" X 2" X 2-1/2" in size. (For definition of offset and form of test specimen, see Fig. 38.)

_Cleavage_: The cleavage tests will be made on specimens of the form and size shown in Fig. 45. The apparatus will be as shown in Fig. 44. The maximum load only will be taken and the result expressed in pounds per inch of width. The speed of the moving head will be 0.25 inch per minute.

_Moisture Determinations_

Moisture determinations will be made on all specimens tested except those to be photographed or kept for exhibit. A 1-inch disk will be cut from near the point of failure of bending and compression parallel specimens, from the portion under the plate in the case of the compression perpendicular specimens, and from the centre of the hardness test specimens. The beads from the shear specimens will be used as moisture disks. In the case of the cleavage specimens a piece 1/2 inch thick will be split off parallel to the failure and used as a moisture disk.

RECORDS

All records will be standard.

PHOTOGRAPHS

_Cross Sections_

Just before cutting into sticks, the freshly cut end of at least one bolt from each tree will be photographed. A scale of inches will be shown in this photograph.

_Specimens_

Three photographs will be made of a group consisting of four 2" X 2" X 30" specimens chosen from the material from each locality. Two of these specimens will be representative of average growth, one of fast and one of slow growth. These photographs will show radial, tangential, and end surfaces for each specimen.

_Failures_

Typical and abnormal failures of material from each site will be photographed.

_Disposition of Material_

The specimens photographed to show typical and abnormal failures will be saved for purposes of exhibit until deemed by the person in charge of the laboratory to be of no further value.

SHRINKAGE AND SPECIFIC GRAVITY

Appendix to Working Plan 124

PURPOSE OF WORK

It is the purpose of this work to secure data on the shrinkage and specific gravity of woods tested under Project 124. The figures to be obtained are for use as average working values rather than as the basis for a detailed study of the principles involved.

MATERIAL

The material will be taken from that provided for mechanical tests.

RADIAL AND TANGENTIAL SHRINKAGE

_Specimens_

_Preparation_: Two specimens 1 inch thick, 4 inches wide, and 1 inch long will be obtained from near the periphery of each "_d_" bolt. These will be cut from the sector-shaped sections left after securing the material for the mechanical tests or from disks cut from near the end of the bolt. They will be taken from adjoining pieces chosen so that the results will be comparable for use in determining radial and tangential shrinkage. (When a disk is used, care must be taken that it is green and has not been affected by the shrinkage and checking near the end of the bolt.)

One of these specimens will be cut with its width in the radial direction and will be used for the determination of radial shrinkage. The other will have its width in the tangential direction and will be used for tangential shrinkage. These specimens will not be surfaced.

_Marking_: The shrinkage specimens will retain the shipment and piece numbers and marks of the bolts from which they are taken, and will have the additional mark _7_R or _7_T according as their widths are in the radial or tangential direction.

_Shrinkage measurements_: The shrinkage specimens will be carefully weighed and measured soon after cutting. Rings per inch, per cent sap, and per cent summer wood will be measured. They will then be air-dried in the laboratory to constant weight, and afterward oven-dried at 100°C. (212°F.), when they will again be weighed and measured.

VOLUMETRIC SHRINKAGE AND SPECIFIC GRAVITY

_Specimens_

_Selection and preparation_: Four 2" X 2" X 6" specimens will be cut from the mechanical test sticks of each "_d_" bolt; also from each of the composite bolts used in getting a comparison of green and air-dry. One of these specimens will be taken from near the pith and one from near the periphery; the other two will be representative of the average growth of the bolt. The sides of these specimens will be surfaced and the ends smooth sawn.

_Marking_: Each specimen will retain the shipment, piece, and stick numbers and mark of the stick from which it is cut, and will have the additional mark "_S_."

_Manipulation_: Soon after cutting, each specimen will be weighed and its volume will be determined by the method described below. The rings per inch and per cent summer wood, where possible, will be determined, and a carbon impression of the end of the specimen made. It will then be air-dried in the laboratory to a constant weight and afterward oven-dried at 100°C. When dry, the specimen will be taken from the oven, weighed, and a carbon impression of its end made. While still warm the specimen will be dipped in hot paraffine. The volume will then be determined by the following method:

On one pan of a pair of balances is placed a container having in it water enough for the complete submersion of the test specimen. This container and water is balanced by weights placed on the other scale pan. The specimen is then held completely submerged and not touching the container while the scales are again balanced. The weight required to balance is the weight of water displaced by the specimen, and hence if in grams is numerically equal to the volume of the specimen in cubic centimetres. A diagrammatic sketch of the arrangement of this apparatus is shown in Fig. 51.

Air-dry specimens will be dipped in water and then wiped dry after the first weighing and just before being immersed for weighing their displacement. All displacement determinations will be made as quickly as possible in order to minimize the absorption of water by the specimen.

STRENGTH VALUES FOR STRUCTURAL TIMBERS

(From Cir. 189, U.S. Forest Service)

The following tables bring together in condensed form the average strength values resulting from a large number of tests made by the Forest Service on the principal structural timbers of the United States. These results are more completely discussed in other publications of the Service, a list of which is given in BIBLIOGRAPHY, PART III.

The tests were made at the laboratories of the U.S. Forest Service, in cooperation with the following institutions: Yale Forest School, Purdue University, University of California, University of Oregon, University of Washington, University of Colorado, and University of Wisconsin.

Tables XVIII and XIX give the average results obtained from tests on green material, while Tables XX and XXI give average results from tests on air-seasoned material. The small specimens, which were invariably 2" X 2" in cross section, were free from defects such as knots, checks, and cross grain; all other specimens were representative of material secured in the open market. The relation of stresses developed in different structural forms to those developed in the small clear specimens is shown for each factor in the column headed "Ratio to 2" X 2"." Tests to determine the mechanical properties of different species are often confined to small, clear specimens. The ratios included in the tables may be applied to such results in order to approximate the strength of the species in structural sizes, and containing the defects usually encountered, when tests on such forms are not available.

A comparison of the results of tests on seasoned material with those from tests on green material shows that, without exception, the strength of the 2" X 2" specimens is increased by lowering the moisture content, but that increase in strength of other sizes is much more erratic. Some specimens, in fact, show an apparent loss in strength due to seasoning. If structural timbers are seasoned slowly, in order to avoid excessive checking, there should be an increase in their strength. In the light of these facts it is not safe to base working stresses on results secured from any but green material. For a discussion of factors of safety and safe working stresses for structural timbers see the Manual of the American Railway Engineering Association, Chicago, 1911. A table from that publication, giving working unit stresses for structural timber, is reproduced in this book, see Table XXII.

|-----------------------------------------------------------------------------------------------------------------------------------| | TABLE XVIII TABLE XVIII | |-----------------------------------------------------------------------------------------------------------------------------------| | BENDING TESTS ON GREEN MATERIAL | |-----------------------------------------------------------------------------------------------------------------------------------| | | Sizes | | | | F.S. at E.L. | M. of R. | M. of E. | Calculated | | |-----------------| Num- | Per | Rings | | | | shear | | Species | | | ber | cent | per |-----------------+-----------------+-----------------+-----------------| | | Cross | Span | of | mois- | inch | Average | Ratio | Average | Ratio | Average | Ratio | Average | Ratio | | | Section | | tests | ture | | per sq. | to 2" | per sq. | to 2" | per sq. | to 2" | per sq. | to 2" | | | | | | | | inch | by 2" | inch | by 2" | inch | by 2" | inch | by 2" | |-----------------+----------+------+-------+-------+-------+---------+-------+---------+-------+---------+-------+---------+-------| | | | | | | | | | | | 1,000 | | | | | | Inches | Ins. | | | | Lbs. | | Lbs. | | lbs. | | Lbs. | | | | | | | | | | | | | | | | | | Longleaf pine | 12 by 12 | 138 | 4 | 28.6 | 9.7 | 4,029 | 0.83 | 6,710 | 0.74 | 1,523 | 0.99 | 261 | 0.86 | | | 10 by 16 | 168 | 4 | 26.8 | 16.7 | 6,453 | .85 | 6,453 | .71 | 1,626 | 1.05 | 306 | 1.01 | | | 8 by 16 | 156 | 7 | 28.4 | 14.6 | 3,147 | .64 | 5,439 | .60 | 1,368 | .89 | 390 | 1.29 | | | 6 by 16 | 132 | 1 | 40.3 | 21.8 | 4,120 | .83 | 6,460 | .71 | 1,190 | .77 | 378 | 1.25 | | | 6 by 10 | 180 | 1 | 31.0 | 6.2 | 3,580 | .72 | 6,500 | .72 | 1,412 | .92 | 175 | .58 | | | 6 by 8 | 180 | 2 | 27.0 | 8.2 | 3,735 | .75 | 5,745 | .63 | 1,282 | .83 | 121 | .40 | | | 2 by 2 | 30 | 15 | 33.9 | 14.1 | 4,950 | 1.00 | 9,070 | 1.00 | 1,540 | 1:00 | 303 | 1.00 | | Douglas fir | 8 by 16 | 180 | 191 | 31.5 | 11.0 | 3,968 | .76 | 5,983 | .72 | 1,517 | .95 | 269 | .81 | | | 5 by 8 | 180 | 84 | 30.1 | 10.8 | 3,693 | .71 | 5,178 | .63 | 1,533 | .96 | 172 | .52 | | | 2 by 12 | 180 | 27 | 35.7 | 20.3 | 3,721 | .71 | 5,276 | .64 | 1,642 | 1.03 | 256 | .77 | | | 2 by 10 | 180 | 26 | 32.9 | 21.6 | 3,160 | .60 | 4,699 | .57 | 1,593 | 1.00 | 189 | .57 | | | 2 by 8 | 180 | 29 | 33.6 | 17.6 | 3,593 | .69 | 5,352 | .65 | 1,607 | 1.01 | 171 | .51 | | | 2 by 2 | 24 | 568 | 30.4 | 11.6 | 5,227 | 1.00 | 9,070 | 1.00 | 1,540 | 1.00 | 303 | 1.00 | | Douglas fir | | | | | | | | | | | | | | | (fire-killed) | 8 by 16 | 180 | 30 | 36.8 | 10.9 | 3,503 | .80 | 4,994 | .64 | 1,531 | .94 | 330 | 1.19 | | | 2 by 12 | 180 | 32 | 34.2 | 17.7 | 3,489 | .80 | 5,085 | .66 | 1,624 | .99 | 247 | .89 | | | 2 by 10 | 180 | 32 | 38.9 | 18.1 | 3,851 | .88 | 5,359 | .69 | 1,716 | 1.05 | 216 | .78 | | | 2 by 8 | 180 | 31 | 37.0 | 15.7 | 3,403 | .78 | 5,305 | .68 | 1,676 | 1.02 | 169 | .61 | | | 2 by 2 | 30 | 290 | 33.2 | 17.2 | 4,360 | 1.00 | 7,752 | 1.00 | 1,636 | 1.00 | 277 | 1.00 | | Shortleaf pine | 8 by 16 | 180 | 12 | 39.5 | 12.1 | 3,185 | .73 | 5,407 | .70 | 1,438 | 1.03 | 362 | 1.40 | | | 8 by 14 | 180 | 12 | 45.8 | 12.7 | 3,234 | .74 | 5,781 | .75 | 1,494 | 1.07 | 338 | 1.31 | | | 8 by 12 | 180 | 24 | 52.2 | 11.8 | 3,265 | .75 | 5,503 | .71 | 1,480 | 1.06 | 277 | 1.07 | | | 5 by 8 | 180 | 24 | 47.8 | 11.5 | 3,519 | .81 | 5,732 | .74 | 1,485 | 1.06 | 185 | .72 | | | 2 by 2 | 30 | 254 | 51.7 | 13.6 | 4,350 | 1.00 | 7,710 | 1.00 | 1,395 | 1.00 | 258 | 1.00 | | Western larch | 8 by 16 | 180 | 32 | 51.0 | 25.3 | 3,276 | .77 | 4,632 | .64 | 1,272 | .97 | 298 | 1.11 | | | 8 by 12 | 180 | 30 | 50.3 | 23.2 | 3,376 | .79 | 5,286 | .73 | 1,331 | 1.02 | 254 | .94 | | | 5 by 8 | 180 | 14 | 56.0 | 25.6 | 3,528 | .83 | 5,331 | .74 | 1,432 | 1.09 | 169 | .63 | | | 2 by 2 | 28 | 189 | 46.2 | 26.2 | 4,274 | 1.00 | 7,251 | 1.00 | 1,310 | 1.00 | 269 | 1.00 | | Loblolly pine | 8 by 16 | 180 | 17 | 15.8 | 6.1 | 3,094 | .75 | 5,394 | .69 | 1,406 | .98 | 383 | 1.44 | | | 5 by 12 | 180 | 94 | 60.9 | 5.9 | 3,030 | .74 | 5,028 | .64 | 1,383 | .96 | 221 | .83 | | | 2 by 2 | 30 | 44 | 70.9 | 5.4 | 4,100 | 1.00 | 7,870 | 1.00 | 1,440 | 1.00 | 265 | 1.00 | | Tamarack | 6 by 12 | 162 | 15 | 57.6 | 16.6 | 2,914 | .75 | 4,500 | .66 | 1,202 | 1.05 | 255 | 1.11 | | | 4 by 10 | 162 | 15 | 43.5 | 11.4 | 2,712 | .70 | 4,611 | .68 | 1,238 | 1.08 | 209 | .91 | | | 2 by 2 | 30 | 82 | 38.8 | 14.0 | 3,875 | 1.00 | 6,820 | 1.00 | 1,141 | 1.00 | 229 | 1.00 | | Western hemlock | 8 by 16 | 180 | 39 | 42.5 | 15.6 | 3,516 | .80 | 5,296 | .73 | 1,445 | 1.01 | 261 | .92 | | | 2 by 2 | 28 | 52 | 51.8 | 12.1 | 4.406 | 1.00 | 7,294 | 1.00 | 1,428 | 1.00 | 284 | 1.00 | | Redwood | 8 by 16 | 180 | 14 | 86.5 | 19.9 | 3,734 | .79 | 4,492 | .64 | 1,016 | .96 | 300 | 1.21 | | | 6 by 12 | 180 | 14 | 87.3 | 17.8 | 3,787 | .80 | 4,451 | .64 | 1,068 | 1.00 | 224 | .90 | | | 7 by 9 | 180 | 14 | 79.8 | 16.7 | 4,412 | .93 | 5,279 | .76 | 1,324 | 1.25 | 199 | .80 | | | 3 by 14 | 180 | 13 | 86.1 | 23.7 | 3,506 | .74 | 4,364 | .62 | 947 | .89 | 255 | 1.03 | | | 2 by 12 | 180 | 12 | 70.9 | 18.6 | 3,100 | .65 | 3,753 | .54 | 1,052 | .99 | 187 | .75 | | | 2 by 10 | 180 | 13 | 55.8 | 20.0 | 3,285 | .69 | 4,079 | .58 | 1,107 | 1.04 | 169 | .68 | | | 2 by 8 | 180 | 13 | 63.8 | 21.5 | 2,989 | .63 | 4,063 | .58 | 1,141 | 1.08 | 134 | .54 | | | 2 by 2 | 28 | 157 | 75.5 | 19.1 | 4,750 | 1.00 | 6,980 | 1.00 | 1,061 | 1.00 | 248 | 1.00 | | Norway pine | 6 by 12 | 162 | 15 | 50.3 | 12.5 | 2,305 | .82 | 3,572 | .69 | 987 | 1.03 | 201 | 1.17 | | | 4 by 12 | 162 | 18 | 47.9 | 14.7 | 2,648 | .94 | 4,107 | .79 | 1,255 | 1.31 | 238 | 1.38 | | | 4 by 10 | 162 | 16 | 45.7 | 13.3 | 2,674 | .95 | 4,205 | .81 | 1,306 | 1.36 | 198 | 1.15 | | | 2 by 2 | 30 | 133 | 32.3 | 11.4 | 2,808 | 1.00 | 5,173 | 1.00 | 960 | 1.00 | 172 | 1.00 | | Red spruce | 2 by 10 | 144 | 14 | 32.5 | 21.9 | 2,394 | .66 | 3,566 | .60 | 1,180 | 1.02 | 181 | .80 | | | 2 by 2 | 26 | 60 | 37.3 | 21.3 | 3,627 | 1.00 | 5,900 | 1.00 | 1,157 | 1.00 | 227 | 1.00 | | White spruce | 2 by 10 | 144 | 16 | 40.7 | 9.3 | 2,239 | .72 | 3,288 | .63 | 1,081 | 1.08 | 166 | .83 | | | 2 by 2 | 26 | 83 | 58.3 | 10.2 | 3.090 | 1.00 | 5,185 | 1.00 | 998 | 1.00 | 199 | 1.00 | |-----------------------------------------------------------------------------------------------------------------------------------| | _Note.--Following is an explanation of the abbreviations used in the foregoing tables:_ | | F.S. at E.L. = Fiber stress at elastic limit. | | M. of E. = Modulus of elasticity. | | M. of R. = Modulus of rupture. | | Cr. str. at E.L. = Crushing strength at elastic limit. | | Cr. str. at max. ld. = Crushing strength at maximum load. | |-----------------------------------------------------------------------------------------------------------------------------------|

|-----------------------------------------------------------------------------------------------------------------------------------------------| | TABLE XIX TABLE XIX | |-----------------------------------------------------------------------------------------------------------------------------------------------| | COMPRESSION AND SHEAR TESTS ON GREEN MATERIAL | |-----------------------------------------------------------------------------------------------------------------------------------------------| | | Compression | Compression | Shear | | | parallel to grain | perpendicular to grain | | | |------------------------------------------------------+-------------------------------------------+--------------------------| | | | | | Cr. | | Cr. | | | | | Cr. | | | | | Species | | | Per | str. | M. of | str. | | | | Per | str. | | Per | | | | Size of | No. | cent | at | E. | at max. | Stress | | No. | cent | at max. | No. | cent | Shear | | | specimen | of | of | E. L. | per | ld.,. | area | Height | of | of | ld., | of | of | strength | | | | tests | mois- | per | square | per | | | tests | mois- | per | tests | mois- | | | | | | ture | square | inch | square | | | | ture | square | | ture | | | | | | | inch | | inch | | | | | inch | | | | |-----------------+----------+-------+-------+--------+--------+---------+--------+--------+-------+ ------+---------+-------+-------+----------| | | | | | | 1,000 | | | | | | | | | | | | Inches | | | Lbs. | lbs. | Lbs. | Inches | Inches | | | Lbs. | | | Lbs. | | | | | | | | | | | | | | | | | | Longleaf pine | 4 by 4 | 46 | 26.3 | 3,480 | | 4,800 | 4 by 4 | 4 | 22 | 25.3 | 568 | 44 | 21.8 | 973 | | | 2 by 2 | 14 | 34.7 | | | 4,400 | | | | | | | | | | Douglas fir | 6 by 6 | 515 | 30.7 | 2,780 | 1,181 | 3,500 | 4 by 8 | 16 | 259 | 30.3 | 570 | 531 | 29.7 | 765 | | | 5 by 6 | 170 | 30.9 | 2,720 | 2,123 | 3,490 | | | | | | | | | | | 2 by 2 | 902 | 29.8 | 3,500 | 1,925 | 4,030 | | | | | | | | | | Douglas fir | | | | | | | | | | | | | | | | (fire-killed) | 6 by 6 | 108 | 34.8 | 2,620 | 1,801 | 3,290 | 6 by 8 | 16 | 24 | 33.7 | 368 | 77 | 35.8 | 631 | | | 2 by 2 | 204 | 37.9 | | | 3,430 | | | | | | | | | | Shortleaf pine | 6 by 6 | 95 | 41.2 | 2,514 | 1,565 | 3,436 | 5 by 8 | 16 | 12 | 37.7 | 361 | 179 | 47.0 | 704 | | | 5 by 8 | 23 | 43.5 | 2,241 | 1,529 | 3,423 | 5 by 8 | 14 | 12 | 42.8 | 366 | | | | | | 2 by 2 | 281 | 51.4 | | | 3,570 | 5 by 8 | 12 | 24 | 53.0 | 325 | | | | | | | | | | | | 5 by 5 | 8 | 24 | 47.0 | 344 | | | | | | | | | | | | 2 by 2 | 2 | 277 | 48.5 | 400 | | | | | Western larch | 6 by 6 | 107 | 49.1 | 2,675 | 1,575 | 3,510 | 6 by 8 | 16 | 22 | 43.6 | 417 | 179 | 40.7 | 700 | | | 2 by 2 | 491 | 50.6 | 3,026 | 1,545 | 3,696 | 6 by 8 | 12 | 20 | 40.2 | 416 | | | | | | | | | | | | 4 by 6 | 6 | 53 | 52.8 | 478 | | | | | | | | | | | | 4 by 4 | 4 | 30 | 50.4 | 472 | | | | | Loblolly pine | 8 by 8 | 14 | 63.4 | 1,560 | 365 | 2,140 | 8 by 4 | 8 | 16 | 67.2 | 392 | 121 | 83.2 | 630 | | | 4 by 8 | 18 | 60.0 | 2,430 | 691 | 3,560 | 4 by 4 | 8 | 38 | 44.6 | 546 | | | | | | 2 by 2 | 53 | 74.0 | | | 3,240 | | | | | | | | | | Tamarack | 6 by 7 | 4 | 49.9 | 2,332 | 1,432 | 3,032 | | | | | | 24 | 39.2 | 668 | | | 4 by 7 | 6 | 27.7 | 2,444 | 1,334 | 3,360 | | | | | | | | | | | 2 by 2 | 165 | 36.8 | | | 3,190 | | | | | | | | | | Western hemlock | 6 by 6 | 82 | 46.6 | 2,905 | 1,617 | 3,355 | 6 by 4 | 6 | 30 | 48.7 | 434 | 54 | 65.7 | 630 | | | 2 by 2 | 131 | 55.6 | 2,938 | 1,737 | 3,392 | | | | | | | | | | Redwood | 6 by 6 | 34 | 83.6 | 3,194 | 1,240 | 3,882 | 6 by 8 | 16 | 13 | 86.7 | 473 | 148 | 84.2 | 742 | | | 2 by 2 | 143 | 36.8 | 3,490 | 1,222 | 3,980 | 6 by 6 | 12 | 14 | 83.0 | 424 | | | | | | | | | | | | 6 by 7 | 9 | 13 | 74.7 | 477 | | | | | | | | | | | | 6 by 3 | 14 | 13 | 75.6 | 411 | | | | | | | | | | | | 6 by 2 | 12 | 12 | 66.5 | 430 | | | | | | | | | | | | 6 by 2 | 10 | 11 | 55.0 | 423 | | | | | | | | | | | | 6 by 2 | 8 | 12 | 56.7 | 396 | | | | | | | | | | | | 2 by 2 | 2 | 186 | 75.5 | 569 | | | | | Norway pine | 6 by 7 | 5 | 29.0 | 1,928 | 905 | 2,404 | | | | | | 20 | 26.7 | 589 | | | 4 by 7 | 8 | 28.4 | 2,154 | 1,063 | 2,652 | | | | | | | | | | | 2 by 2 | 178 | 26.8 | | | 2,504 | | | | | | | | | | Red spruce | 2 by 2 | 58 | 35.4 | | | 2,750 | 2 by 2 | 2 | 43 | 31.8 | 310 | 30 | 32.0 | 758 | | White spruce | 2 by 2 | 84 | 61.0 | | | 2,370 | 2 by 2 | 2 | 46 | 50.4 | 270 | 40 | 58.0 | 651 | |-----------------------------------------------------------------------------------------------------------------------------------------------| | _Note.--Following is an explanation of the abbreviations used in the foregoing tables:_ | | F.S. at E.L. = Fiber stress at elastic limit. | | M. of E. = Modulus of elasticity. | | M. of R. = Modulus of rupture. | | Cr. str. at E.L. = Crushing strength at elastic limit. | | Cr. str. at max. ld. = Crushing strength at maximum load. | |-----------------------------------------------------------------------------------------------------------------------------------------------|

|-----------------------------------------------------------------------------------------------------------------------------------| | TABLE XX TABLE XX | |-----------------------------------------------------------------------------------------------------------------------------------| | BENDING TESTS ON AIR-SEASONED MATERIAL | |-----------------------------------------------------------------------------------------------------------------------------------| | | Sizes | | | | F.S. at E.L. | M. of R. | M. of E. | Calculated | | |-----------------| Num- | Per | Rings | | | | shear | | Species | | | ber | cent | per |-----------------+-----------------+-----------------+-----------------| | | Cross | Span | of | mois- | inch | Average | Ratio | Average | Ratio | Average | Ratio | Average | Ratio | | | Section | | tests | ture | | per sq. | to 2" | per sq. | to 2" | per sq. | to 2" | per sq. | to 2" | | | | | | | | inch | by 2" | inch | by 2" | inch | by 2" | inch | by 2" | |-----------------+----------+------+-------+-------+-------+---------+-------+---------+-------+---------+-------+---------+-------| | | | | | | | | | | | 1,000 | | | | | | Inches | Ins. | | | | Lbs. | | Lbs. | | lbs. | | Lbs. | | | | | | | | | | | | | | | | | | Longleaf pine | 8 by 16 | 180 | 5 | 22.2 | 16.0 | 3,390 | 0.50 | 4,274 | 0.37 | 1,747 | 1.00 | 288 | 0.75 | | | 6 by 16 | 132 | 1 | 23.4 | 17.1 | 3,470 | .51 | 6,610 | .57 | 1,501 | .86 | 388 | 1.01 | | | 6 by 10 | 177 | 2 | 19.0 | 8.8 | 4,560 | .68 | 7,880 | .68 | 1,722 | .99 | 214 | .56 | | | 4 by 11 | 180 | 1 | 18.4 | 23.9 | 3,078 | .46 | 8,000 | .69 | 1,660 | .95 | 251 | .66 | | | 6 by 8 | 177 | 6 | 20.0 | 13.7 | 4,227 | .63 | 8,196 | .71 | 1,634 | .94 | 177 | .46 | | | 2 by 2 | 30 | 17 | 15.9 | 13.9 | 6,750 | 1.00 | 11,520 | 1.00 | 1,740 | 1.00 | 383 | 1.00 | | Douglas fir | 8 by 16 | 180 | 91 | 20.8 | 13.1 | 4,563 | .68 | 6,372 | .61 | 1,549 | .91 | 269 | .64 | | | 5 by 8 | 180 | 30 | 14.9 | 12.2 | 5,065 | .76 | 6,777 | .65 | 1,853 | 1.09 | 218 | .52 | | | 2 by 2 | 24 | 211 | 19.0 | 16.4 | 6,686 | 1.00 | 10,378 | 1.00 | 1,695 | 1.00 | 419 | 1.00 | | Shortleaf pine | 8 by 16 | 180 | 3 | 17.0 | 12.3 | 4,220 | .54 | 6,030 | .50 | 1,517 | .85 | 398 | .98 | | | 8 by 14 | 180 | 3 | 16.0 | 12.3 | 4,253 | .55 | 5,347 | .44 | 1,757 | .98 | 307 | .76 | | | 8 by 12 | 180 | 7 | 16.0 | 12.4 | 5,051 | .65 | 7,331 | .60 | 1,803 | 1.01 | 361 | .89 | | | 5 by 8 | 180 | 6 | 12.2 | 22.5 | 7,123 | .92 | 9,373 | .77 | 1,985 | 1.11 | 301 | .74 | | | 2 by 2 | 30 | 67 | 14.2 | 13.7 | 7,780 | 1.00 | 12,120 | 1.00 | 1,792 | 1.00 | 404 | 1.00 | | Western larch | 8 by 16 | 180 | 23 | 18.3 | 21.9 | 3,343 | .57 | 5,440 | .53 | 1,409 | .90 | 349 | .96 | | | 8 by 12 | 180 | 29 | 17.8 | 23.4 | 3,631 | .62 | 6,186 | .60 | 1,549 | .99 | 295 | .81 | | | 5 by 8 | 180 | 10 | 13.6 | 27.6 | 4,730 | .80 | 7,258 | .71 | 1,620 | 1.04 | 221 | .61 | | | 2 by 2 | 30 | 240 | 16.1 | 26.8 | 5,880 | 1.00 | 10,254 | 1.00 | 1,564 | 1.00 | 364 | 1.00 | | Loblolly pine | 8 by 16 | 180 | 14 | 20.5 | 7.4 | 4,195 | .81 | 6,734 | .72 | 1,619 | 1.10 | 462 | 1.45 | | | 6 by 16 | 126 | 4 | 20.2 | 5.0 | 2,432 | .47 | 4,295 | .46 | 1,324 | .90 | 266 | .84 | | | 6 by 10 | 174 | 3 | 21.3 | 4.7 | 3,100 | .60 | 6,167 | .66 | 1,449 | .99 | 173 | .54 | | | 4 by 12 | 174 | 4 | 19.8 | 4.7 | 2,713 | .52 | 5,745 | .61 | 1,249 | .85 | 185 | .58 | | | 8 by 8 | 180 | 9 | 22.9 | 4.9 | 2,903 | .56 | 4,557 | .48 | 1,136 | .77 | 93 | .29 | | | 6 by 7 | 144 | 2 | 21.1 | 5.0 | 2,990 | .58 | 4,968 | .53 | 1,286 | .88 | 116 | .36 | | | 4 by 8 | 132 | 8 | 19.5 | 9.1 | 3,384 | .65 | 6,194 | .66 | 1,200 | .82 | 196 | .62 | | | 2 by 2 | 30 | 123 | 17.6 | 6.6 | 5,170 | 1.00 | 9,400 | 1.00 | 1,467 | 1.00 | 318 | 1.00 | | Tamarack | 6 by 12 | 162 | 5 | 23.0 | 15.1 | 3,434 | .45 | 5,640 | .43 | 1,330 | .82 | 318 | .75 | | | 4 by 10 | 162 | 4 | 14.4 | 9.7 | 4,100 | .54 | 5,320 | .41 | 1,386 | .84 | 252 | .59 | | | 2 by 2 | 30 | 47 | 11.3 | 16.2 | 7,630 | 1.00 | 13,080 | 1.00 | 1,620 | 1.00 | 425 | 1.00 | | Western hemlock | 8 by 16 | 180 | 44 | 17.7 | 17.8 | 4,398 | .69 | 6,420 | .62 | 1,737 | 1.04 | 406 | 1.06 | | | 2 by 2 | 28 | 311 | 17.9 | 19.4 | 6,333 | 1.00 | 10,369 | 1.00 | 1,666 | 1.00 | 382 | 1.00 | | Redwood | 8 by 16 | 180 | 6 | 26.3 | 22.4 | 3,797 | .79 | 4,428 | .57 | 1,107 | .96 | 294 | 1.05 | | | 6 by 12 | 180 | 6 | 16.1 | 17.7 | 3,175 | .66 | 3,353 | .43 | 728 | .64 | 167 | .60 | | | 7 by 9 | 180 | 6 | 15.9 | 15.2 | 3,280 | .69 | 4,002 | .51 | 1,104 | .96 | 147 | .53 | | | 3 by 14 | 180 | 6 | 13.1 | 24.4 | | | 5,033 | .64 | | | 291 | 1.04 | | | 2 by 12 | 180 | 5 | 13.8 | 14.4 | 3,928 | .82 | 5,336 | .68 | 1,249 | 1.09 | 260 | .93 | | | 2 by 10 | 180 | 5 | 13.8 | 24.8 | 3,757 | .79 | 4,606 | .59 | 1,198 | 1.05 | 186 | .67 | | | 2 by 8 | 180 | 6 | 13.7 | 20.7 | 4,314 | .90 | 5,050 | .65 | 1,313 | 1.15 | 166 | .60 | | | 2 by 2 | 28 | 122 | 15.2 | 18.8 | 4,777 | 1.00 | 7,798 | 1.00 | 1,146 | 1.00 | 279 | 1.00 | | Norway pine | 6 by 12 | 162 | 5 | 16.7 | 8.1 | 2,968 | .56 | 5,204 | .61 | 1,123 | .97 | 286 | 1.02 | | | 4 by 10 | 162 | 5 | 13.7 | 12.0 | 5,170 | .98 | 6,904 | .82 | 1,712 | 1.48 | 317 | 1.13 | | | 2 by 2 | 30 | 60 | 14.9 | 11.2 | 5,280 | 1.00 | 8,470 | 1.00 | 1,158 | 1.00 | 281 | 1.00 | |-----------------------------------------------------------------------------------------------------------------------------------| | _Note.--Following is an explanation of the abbreviations used in the foregoing tables:_ | | F.S. at E.L. = Fiber stress at elastic limit. | | M. of E. = Modulus of elasticity. | | M. of R. = Modulus of rupture. | | Cr. str. at E.L. = Crushing strength at elastic limit. | | Cr. str. at max. ld. = Crushing strength at maximum load. | |-----------------------------------------------------------------------------------------------------------------------------------|

|-----------------------------------------------------------------------------------------------------------------------------------------------| | TABLE XXI TABLE XXI | |-----------------------------------------------------------------------------------------------------------------------------------------------| | COMPRESSION AND SHEAR TESTS ON AIR-SEASONED MATERIAL | |-----------------------------------------------------------------------------------------------------------------------------------------------| | | Compression | Compression | Shear | | | parallel to grain | perpendicular to grain | | | |------------------------------------------------------+-------------------------------------------+--------------------------| | | | | | Cr. | | Cr. | | | | | Cr. | | | | | Species | | | Per | str. | M. of | str. | | | | Per | str. | | Per | | | | Size of | No. | cent | at | E. | at max. | Stress | | No. | cent | at max. | No. | cent | Shear | | | specimen | of | of | E. L. | per | ld.,. | area | Height | of | of | ld., | of | of | strength | | | | tests | mois- | per | square | per | | | tests | mois- | per | tests | mois- | | | | | | ture | square | inch | square | | | | ture | square | | ture | | | | | | | inch | | inch | | | | | inch | | | | |-----------------+----------+-------+-------+--------+--------+---------+--------+--------+-------+ ------+---------+-------+-------+----------| | | | | | | 1,000 | | | | | | | | | | | | Inches | | | Lbs. | lbs. | Lbs. | Inches | Inches | | | Lbs. | | | Lbs. | | | | | | | | | | | | | | | | | | Longleaf pine | 4 by 5 | 46 | 26.3 | 3,480 | | 4,800 | 4 by 5 | 4 | 22 | 25.1 | 572 | 52 | 20.2 | 984 | | Douglas fir | 6 by 6 | 259 | 20.3 | 3,271 | 1,038 | 4,258 | 4 by 8 | 16 | 44 | 20.8 | 732 | 465 | 22.1 | 822 | | | 2 by 2 | 247 | 18.7 | 3,842 | 1,084 | 5,002 | 4 by 8 | 10 | 32 | 18.1 | 584 | | | | | | | | | | | | 4 by 4 | 8 | 51 | 20.2 | 638 | | | | | | | | | | | | 4 by 4 | 6 | 49 | 24.0 | 613 | | | | | | | | | | | | 4 by 4 | 4 | 29 | 24.8 | 603 | | | | | Shortleaf pine | 6 by 6 | 29 | 15.7 | 4,070 | 1,951 | 6,030 | 8 by 5 | 16 | 4 | 17.8 | 725 | 85 | | 1,135 | | | 2 by 2 | 57 | 14.2 | | | 6,380 | 8 by 5 | 14 | 3 | 16.3 | 757 | | | | | | | | | | | | 8 by 5 | 12 | 5 | 15.1 | 730 | | | | | | | | | | | | 5 by 5 | 8 | 6 | 13.0 | 918 | | | | | | | | | | | | 2 by 2 | 2 | 57 | 13.9 | 926 | | | | | Western larch | 6 by 6 | 112 | 16.0 | | | 5,445 | 8 by 6 | 16 | 17 | 18.8 | 491 | 193 | 15.0 | 905 | | | 4 by 4 | 81 | 14.7 | | | 6,161 | 8 by 6 | 12 | 18 | 17.6 | 526 | | | | | | 2 by 2 | 270 | 14.8 | | | 5,934 | 5 by 4 | 8 | 22 | 13.3 | 735 | | | | | Loblolly pine | 6 by 6 | 23 | | 3,357 | 1,693 | 5,005 | 8 by 5 | 16 | 12 | 19.8 | 602 | 156 | 11.3 | 1,115 | | | 5 by 5 | 10 | 22.4 | 2,217 | 545 | 2,950 | 8 by 5 | 8 | 7 | 22.9 | 679 | | | | | | 4 by 8 | 8 | 19.4 | 3,010 | 633 | 3,920 | 4 by 5 | 8 | 8 | 19.5 | 715 | | | | | | 2 by 2 | 69 | | | | 5,547 | | | | | | | | | | Tamarack | 6 by 7 | 3 | 15.7 | 2,257 | 1,042 | 3,323 | 2 by 2 | 2 | 57 | 16.2 | 697 | 60 | 14.0 | 879 | | | 4 by 7 | 3 | 13.6 | 3,780 | 1,301 | 4,823 | | | | | | | | | | | 4 by 4 | 57 | 14.9 | 3,386 | 1,353 | 4,346 | | | | | | | | | | | 2 by 2 | 66 | 14.6 | | | 4,790 | | | | | | | | | | Western hemlock | 6 by 6 | 102 | 18.6 | 4,840 | 2,140 | 5,814 | 7 by 6 | 15 | 25 | 18.2 | 514 | 131 | 17.7 | 924 | | | 2 by 2 | 463 | 17.0 | 4,560 | 1,923 | 5,403 | 6 by 6 | 6 | 26 | 16.8 | 431 | | | | | | | | | | | | 4 by 4 | 4 | 6 | 15.9 | 488 | | | | | Redwood | 6 by 6 | 18 | 16.9 | | | 4,276 | 8 by 6 | 16 | 5 | 25.4 | 548 | 95 | 12.4 | 671 | | | 2 by 2 | 115 | 14.6 | | | 5,119 | 6 by 6 | 12 | 6 | 14.7 | 610 | | | | | | | | | | | | 7 by 6 | 9 | 5 | 14.8 | 500 | | | | | | | | | | | | 3 by 6 | 14 | 2 | 12.6 | 470 | | | | | | | | | | | | 2 by 6 | 12 | 2 | 16.2 | 498 | | | | | | | | | | | | 2 by 6 | 10 | 4 | 14.3 | 511 | | | | | | | | | | | | 2 by 6 | 8 | 2 | 13.2 | 429 | | | | | | | | | | | | 2 by 2 | 2 | 145 | 13.8 | 564 | | | | | Norway pine | 6 by 7 | 4 | 15.2 | 2,670 | 1,182 | 4,212 | 2 by 2 | 2 | 36 | 10.0 | 924 | 44 | 11.9 | 1,145 | | | 4 by 7 | 2 | 22.2 | 3,275 | 1,724 | 4,575 | | | | | | | | | | | 4 by 4 | 55 | 16.6 | 3,048 | 1,367 | 4,217 | | | | | | | | | | | 2 by 2 | 44 | 11.2 | | | 7,550 | | | | | | | | | |-----------------------------------------------------------------------------------------------------------------------------------------------| | _Note.--Following is an explanation of the abbreviations used in the foregoing tables:_ | | F.S. at E.L. = Fiber stress at elastic limit. | | M. of E. = Modulus of elasticity. | | M. of R. = Modulus of rupture. | | Cr. str. at E.L. = Crushing strength at elastic limit. | | Cr. str. at max. ld. = Crushing strength at maximum load. | |-----------------------------------------------------------------------------------------------------------------------------------------------|

|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | TABLE XXII TABLE XXII | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | [b]WORKING UNIT-STRESSES FOR STRUCTURAL TIMBER[c] | | EXPRESSED IN POUNDS PER SQUARE INCH | | (From Manual of the American Railway Engineering Assn., 1911, p. 153) | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | NOTE.--The working unit-stresses given in the table are intended for railroad bridges and trestles. For highway bridges and trestles the unit-stresses may be increased | | twenty-five (25) per cent. For buildings and similar structures, in which the timber is protected from the weather and practically free from impact, the unit-stresses may be | | increased fifty (50) per cent. To compute the deflection of a beam under long-continued loading instead of that when the load is first applied, only fifty (50) per cent of the | | corresponding modulus of elasticity given in the table is to be employed. | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | | BENDING | SHEARING | COMPRESSION | | | |---------------------------------+-----------------------------------------+-------------------------------------------------------------------------| Ratio | | | Extreme | Modulus of | Parallel to | Longitudinal | Perpendicular | Parallel to | For | Formulæ for | of | | | fibre | elasticity | the grain | shear in | to the grain | the grain | columns | working stress in | length | | KIND OF | stress | | | beams | | | under 15 | long columns over | of | | TIMBER |--------------------+------------+--------------------+--------------------+--------------------+--------------------| diameters | 15 diameters | stringer | | | Average | Working | | Average | Working | Elastic | Working | Elastic | Working | Average | Working | working | | to | | | ultimate | stress | Average | ultimate | stress | limit | stress | limit | stress | ultimate | stress | stress | | depth | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Douglas fir | 6100 | 1200 | 1,510,000 | 690 | 170 | 270 | 110 | 630 | 310 | 3600 | 1200 | 900 | 1200(1-_l_/60_d_) | 10 | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Longleaf pine | 6500 | 1300 | 1,610,000 | 720 | 180 | 300 | 120 | 520 | 260 | 3800 | 1300 | 980 | 1300(1-_l_/60_d_) | 10 | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Shortleaf pine | 5600 | 1100 | 1,480,000 | 710 | 170 | 330 | 130 | 340 | 170 | 3400 | 1100 | 830 | 1100(1-_l_/60_d_) | 10 | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | White pine | 4400 | 900 | 1,130,000 | 400 | 100 | 180 | 70 | 290 | 150 | 3000 | 1000 | 750 | 1000(1-_l_/60_d_) | 10 | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Spruce | 4800 | 1000 | 1,310,000 | 600 | 150 | 170 | 70 | 370 | 180 | 3200 | 1100 | 830 | 1100(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Norway pine | 4200 | 800 | 1,190,000 | 590[d] | 130 | 250 | 100 | | 150 | 2600[d] | 800 | 600 | 800(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Tamarack | 4600 | 900 | 1,220,000 | 670 | 170 | 260 | 100 | | 220 | 3200[d] | 1000 | 750 | 1000(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Western hemlock | 5800 | 1100 | 1,480,000 | 630 | 160 | 270[d] | 100 | 440 | 220 | 3500 | 1200 | 900 | 1200(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Redwood | 5000 | 900 | 800,000 | 300 | 80 | | | 400 | 150 | 3300 | 900 | 680 | 900(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Bald cypress | 4800 | 900 | 1,150,000 | 500 | 120 | | | 340 | 170 | 3900 | 1100 | 830 | 1100(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | Red cedar | 4200 | 800 | 800,000 | | | | | 470 | 230 | 2800 | 900 | 680 | 900(1-_l_/60_d_) | | |-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------| | White oak | 5700 | 1100 | 1,150,000 | 840 | 210 | 270 | 110 | 920 | 450 | 3500 | 1300 | 980 | 1300(1-_l_/60_d_) | 12 | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | These unit-stresses are for a green condition of timber and are _l_ = Length in inches. | | to be used without increasing the live load stresses for impact. _d_ = Least side in inches. | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| |[Footnote b: Adopted, Vol. 1909, pp. 537, 564, 609-611.] | |[Footnote c: Green timber in exposed work.] | |[Footnote d: Partially air-dry] | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

BIBLIOGRAPHY