EARTHQUAKES AND SEAQUAKES 



91 



reenforced concrete is well adapted, for it has in general the same 

 advantages as steel with somewhat reduced elasticity, but with a 

 more effective binding together of the parts. This requirement 

 of thorough bracing and tying together of the several parts of a 

 building causes it to vibrate, not as many pendulums, but as one 

 body. If met, it removes largely the danger from racking strains, 

 and for small structures particularly it is the requirement which 

 is most easily complied with. For such buildings it is therefore 

 necessary that the framework should be built in a close network 



FIG. 86. Building wrecked at San Mateo, California, during the late earth- 

 quake. The heavy roof and upper floor, acting as a unit, have battered down 

 the upper walls (after J. C. Branner). 



with every joint firmly braced and with all parts securely tied to- 

 gether. Especial attention should be given to the fastenings of 

 floor and partition ends. The house shown in Fig. 85 could not 

 have been subjected to heavy shocks, for though the walls are 

 thrown down, the floors and partitions have been left near their 

 original positions. 



This tendency of the walls, floors, partitions, and roof to act 

 as individual units in the vibration, is one that must be reckoned 

 with and be met by specially effective bracing and tying at the 

 junctions. Otherwise these larger parts of the structure may act 

 like battering rams to throw over the walls or portions of them 

 (Fig. 86). 



