CHAPTER IV 

 ARCHES 



Arches with open webs and with solid webs will be 

 considered. The three-hinged and the two-hinged arch 

 can be handled with but little labor. The influence diagrams 

 for fixed arches are complicated and are best constructed 

 from computed ordinates. 



Equation (d) is now modified by the moment of the 

 horizontal thrust. If the lever arm of the horizontal thrust, 

 H, is represented by y, then 



(e) 



Diagonals in a Three-hinged Arch with Open Web. The 

 frame diagram of a three-hinged arch is shown in Fig. 36 

 and the influence diagrams for the diagonals C/2^/3 and 

 C7 3 L 4 are outlined in Figs. 36a and 366. 



Since there can be no bending moments at the hinges 

 over the supports, M L and M R in equation (e) are zero, and 



/yy\ 



The influence diagram for is the base diagram con- 



54 



