THE PROPER DIMENSIONS FOR BRICK PIERS IN BUILDINGS. 125 



THE PROPER DIMENSIONS FOR BRICK PIERS IN BUILDINGS. 



The committee of architects appointed by Kraft, Holmes & Co. to inves- 

 tigate the fall of the building lately occupied by them, in St, Louis, have made 

 their report. It is made on calculations based on standard authorities, and reads 

 as follows : 



1. A floor, such as the floor of the building now under consideration, com- 

 posed of 3xi6-inch joists, nineteen feet long, and placed twelve inches from cen- 

 tre, will carry 1,914 pounds per square foot as a breaking load; and if we take 

 one-sixth of this as a safe load we will have 319 pounds per square foot as a safe 

 load to place upon these floors. In order to be within the most reasonable 

 bounds we will throw off the nineteen pounds and call the load 300 pounds per 

 square foot, and base the following calculations on that amount : The joists be- 

 ing nineteen feet long and the space between the posts being thirteen feet, as 

 they are in this building, there will be supported by each post and the correspond- 

 ing girder 19x13 equal to 247 square feet of floor surface, which, if loaded as per 

 above calculations, will give a probable load of 247x300, equal to 74,100 pounds 

 on each floor space throughout the building. 



2. The girders, which are made of two pieces of 5xi6-inch white pine tim- 

 ber and one piece of wrought iron ^xi 6-inch, will carry 200 pounds, 860 pounds 

 as a breaking load, and taking one-sixth of this, as above, we will have as a safe 

 load 33,476 pounds. If this is compared with the load found above as the amount 

 the joists were reasonably calculated to carry, which is 74,100 pounds, it will be 

 seen that the girders were not proportioned to the same load as the joists, and 

 would carry only about one-half as much. 



3. The load imposed on one of the 12x12 oak posts in the second story, 

 which are loxii feet long, will be the same as on the girder multiplied by three. 

 There are being that many floors above it, also the roof, the weight of which 

 must be added to it, which gives 74,100x3, equal 222,300 pounds, the roof-space, 

 247x30, equals 7,410 pounds; these amounts added will give 229,710 pounds, 

 which will be about 114 tons. The crushing load of an oak post of this size is 

 432 tons, and taking one-sixth of this as the safe load we will have 72 tons. This 

 will be seen by comparing it with the above load to be but little over one-half 

 what the post might have imposed upon it. 



4. The iron posts having shown no defects, we omitted to compute their 

 strength. 



5. The brick piers in the basement will have to carry the load of all the 

 floors and roof added. This will be 74,100x5, equal to 370,500, to which add 

 7,410, and will have 377,910 pounds, which is 189 tons. 



The dimension of the brick piers being one foot ten inches by two feet five 

 inches, will give four and one-half square feet as the area of each pier. The 

 average crushing load of first-class hard brick work laid in cement mortar is about 



