Materials and Stresses. - Materials, stresses and methods of computation shall be as provided in section fourteen.

Par. 1. - General Requirements. - No metal thinner than one fourth of an inch shall be used except for fillers or beams and channel webs: provided, however, that sheet metal may be used in such buildings and under such restrictions as the commissioner may allow. Connections shall be designed to develop the full strength of the member under the conditions of loading even though the computed stress is less.

Rivets

Par. 2. - Rivets shall be placed in accordance with good engineering practice. The diameter of rivet holes in tension members shall be assumed as one eighth of an inch larger than the rivet. Net sections shall be used in proportioning tension members.

Par. 3. - Beams and Girders. - Every beam, channel, lintel or girder supported by a wall shall be properly anchored thereto, and shall have bearing plates if necessary to distribute the load properly at the stresses required by this act.

Beams and Channels

Par. 4. - Beams and channels acting as skew-backs for arches shall be designed to resist the lateral thrusts in addition to their vertical loads, and the tie rods, not less than three fourths of an inch in diameter, shall be placed as near the line of thrust as practicable, and in any event shall be spaced not more than eight times the depth of the beams, and not more than eight feet.

Par. 5. - Where beams or channels are used in pairs they shall be connected with steel or iron separators near each end and at each concentrated load and not more than five feet apart elsewhere, and beams twelve inches or more in depth, if connected by bolted separators, shall have two bolts for each separator.

Par. 6. - Steel Columns. - Steel column ends shall either be machine faced and brought into actual contact or full riveted connections shall be provided to develop the strength of columns. Latticing and tie plates shall be provided in accordance with good engineering practice.

Par. 7. - Plate Girders. - In proportioning the flanges of plate girders one eighth of the web may be considered as available in each flange. When the top flange is not stayed laterally at distances of twenty times its breadth the stresses shall be reduced as required in section fourteen. Stiffeners, properly fitted at ends, shall be provided over supports and under concentrated loads with sufficient area in the outstanding legs to transmit the stresses in bearing at twenty thousand pounds per square inch, and with sufficient rivets to transmit the stresses to the web. Intermediate stiffeners shall be so spaced that the clear distance between the stiffeners, or the clear distance between flange angles, shall not exceed that given by formula

d= - t/40(12,000 - s) '

where d is the clear distance between stiffeners or flange angles t is the thickness of web s is the shear per square inch.

Par. 8. - Trusses. - Trusses shall be designed so that the stresses in each member can be calculated with reasonable accuracy by statical methods. The centre of gravity lines of members meeting at a joint shall, if possible, intersect at a point. Eccentricity due to a non-fulfillment of this rule shall be allowed for in the computations. The centre of gravity of a group of rivets connecting one member to another shall, in general, lie as nearly as practicable in the centre of gravity line of the member. Trusses shall be properly braced.

Par. 9. - Riveting. - In skeleton construction, all splices in columns, all connections of girders or beams to columns, and all connections subject to a reversal of stress shall be made by means of rivets. In all types of construction, splices in girders and chords of trusses and connections carrying heavy stresses shall be riveted. Minor connections such as floor stringers to girders, carrying moderate stresses, may be either riveted or bolted.

[1918, c. 179, sect. 6, Special Act.]