EXTERNAL FORCES 53 



The reaction from a continuous slab is carried by the beam and 

 constitutes the uniform load on the beam, plus the weight of the 

 beam. This in turn is carried by the girder and, together with 

 the weight of the girder, constitutes the uniform load on the girder. 

 The girder, if continuous, transmits to the columns the effect of 

 the unbalanced moments over supports, of slab, beam, and girder. 

 Columns must be proportioned to carry this load made up of the 

 direct weights plus the unbalanced moments in the system of 

 framing. 



Building ordinances require that the effects of unbalanced 

 moments must be considered in design. The author in his own 

 practice designs in this manner. It is the practice of all reputable 

 designers. The majority of reinforced concrete buildings in the 

 past have been designed by firms engaged in the business of sell- 

 ing steel. A large part of the work of the author for several years 

 consisted in checking these " free " (so-called) designs and he has 

 not found one in which anything more than the direct load was 

 considered. The practice being somewhat common and struc- 

 tural engineers in building departments having passed designs so 

 prepared, he has had no other alternative, for it was what is termed 

 " common practice." After the date on which the present book 

 is placed on the market he will approve no more designs following 

 the old " common practice " and will force designers to fully 

 recognize the effect of unbalanced moments. 



The " free design " is usually given in the following way. An 

 architect is employed by an owner to prepare plans for a rein- 

 forced concrete structure. The architect not being an engineer 

 specialist has a choice of either employing a reputable engineer 

 to prepare the engineering design, for which he must pay a con- 

 siderable part of his own fee if he has no engineer employed on 

 salary, or he merely prepares general drawings and in his speci- 

 fications states that competitive engineering plans will be accepted. 

 Sometimes he fixes the stresses and other necessary designing speci- 

 fications, but more commonly omits to do so. Many architects 

 believe that reinforced concrete design is as standard as steel 

 design, which ig not the case. 



Contractors who bid on the work apply to steel selling con- 

 cerns for designs. These are prepared and the contractor is given 

 a lump sum price for the steel, which includes the cost of making 

 the design. Frequently the amount of concrete is guaranteed by 



