Par. 38. - Stresses. - The stresses in materials used in the construction of all buildings, produced by their own weight and the loads hereinafter specified, shall not exceed the limits assigned in this section.

Par. 39. - Stresses for Brickwork.

Par. 40. - Stresses for Concrete.

Par. 41. - No plain concrete bearing pier shall have a greater height unsupported laterally than six times, and no brick pier greater than twelve times, its least dimension. No brick or plain concrete bearing wall, unless it is properly braced by cross walls, piers or other means, shall have a greater height unsupported than twelve times its least dimension. When compression is applied to a portion of a surface of concrete of which the area is at least twice that to which the load is applied, a stress of fifty per cent in excess of those allowed by the above table may be used in bearing.

Par. 42. - Stresses for Grout and Stone Masonry.

Par. 43. - Provided, however, that in stone masonry columns or in piers of excessive height, the loads may be modified by the commissioner.

Par. 44. - Stresses for Structural Steel and Iron.

Compression.

2 Tension.

Compression Flange of a Riveted Plate Girder

Par. 45. - The compression flange of a riveted plate girder shall not be of a smaller gross section than the tension flange. When the top flange of the steel plate girder, beam or channel is not stayed laterally at distances of twenty times its breadth the above stress on extreme fibre shall be reduced as follows: -

Where I is length of flange in inches. b is breadth of flange in inches.

Steel Compression Members

Par. 46. - Steel compression members shall not have a greater value of 1-r than one hundred and sixty, nor have metal (except for filling) less than one fourth of an inch for interior columns, nor with metal less than five sixteenths of an inch for exterior columns, nor with metal less than five sixteenths of an inch for exterior columns enclosed in masonry. The stress due to eccentric or transverse combined with direct loading shall not exceed sixteen thousand pounds per square inch. For centrally loaded steel compression members the safe load in pounds per square inch shall be as follows: -

Par. 47. - Steel Compression Members.

Where I is the length of the column in inches r is the radius of gyration in inches taken around the axis about which the column will bend.

Par. 48. - Cast Iron Compression Members. - Cast iron compression members shall not have a greater value of ]-r than seventy nor a smaller outside diameter or side than six inches, nor a greater unsupported length than twenty-four times their least dimension or diameter: provided, however, that columns supporting roof loads only may have a value of 1-r not greater than ninety-six and an unsupported length of not more than thirty times the least lateral dimension or diameter. They shall not have metal less than three fourths of an inch, nor thinner than one twelfth of the greatest lateral dimension or side. The stresses due to eccentric or transverse loading, combined with those due to central loading, shall not exceed nine thousand pounds per square inch.

Par. 49. - Cast iron columns shall not be used where the loading is so eccentric as to cause tension, nor in garages, nor in places where they are likely to receive impact from vehicles.

Par. 50. - Wherever the core of a column has shifted more than one quarter of the thickness of the shell, the strength shall be computed assuming the thickness of metal all around to be equal to the thinnest part.

Par. 51. - For centrally loaded cast iron compression members the safe load in pounds per square inch shall be as follows:

Working Stress

Par. 52. - Stresses of Timber.

Par. 53. - Timber Compression Members. - Timber compression members shall not be used of a greater unstayed length than thirty times their least dimension for isolated columns or forty times their least dimension for columns in partitions or truss members. The stresses due to eccentric or transverse loading combined with those due to central loading shall not exceed the maximum stress allowed in the table below.

For centrally loaded timber compression members the safe load per square inch shall be as follows: -

Par. 45. -

Par. 55. - Other Materials. - Stresses for materials and forms of material, not herein mentioned, shall be determined by the commissioner.

Par. 56. - Wind Bracing. - Provisions for wind bracing shall be made where it is necessary in good practice or as determined by the commissioner.

Par. 57. - Cutting. - No cutting for piping or any other purpose shall be done which would reduce the strength of any part of the structure below what is required by the provisions of this act.

Par. 58. - Methods of Computation. - Methods for reinforced concrete are given in section fifteen. For all other materials, the following methods shall be used: -

Par. 59. - The span of beams, girders, or trusses shall be taken as the distance from centre to centre of the bearings. If connected to the side of a column, the span shall be taken to the centre of the column.

Par. 60. - If a tension piece is loaded eccentrically or transversely the maximum combined fiber stress shall not exceed the allowed stress in tension.

Par. 61. - An eccentric load upon a column shall be taken as affecting eccentrically only the length of column extending to the next point below at which the column is stayed securely in the direction of the eccentricity.

Par. 62. - If a piece is exposed to tension and compression at different times it shall be proportioned and connected to resist the maximum of each kind of stress.

Par. 63. - Base-plates, bearing plates, and grillage beams shall be figured on the assumption that the maximum bending moments are under the centre of bearing. [1918, c. 179, sect. 4, Special Act.]