Question

Homework Problem H 7.E Consider the truss shown below with the loading on joints D, K, S and U. Given: Find: For this problem: a) Determine the external reactions acting on the truss at supports A and H b) Identify all zero-force members in the truss. c) Determine the load carried by members BC, CJ and MN. Identify each member as either being in tension, in compression or carrying zero load. For this problem, use the following parameters: h 30 kips and Q-25 kips. 12 ft, b 16 ft, F-20 kips, P 0

Answer 1

a) The FBD of the truss is as shown below:

Q-25 Hx Hy F-20 P 30

for equilbrium, $\Sigma M_H=0$

-Ay x 16 x 5 + 20 x 16 x 3 + 30 x 16 x 2 -25 x 12 x 2 = 0

Ay = 16.5 kips

Also, $\Sigma F_x=0$

Hx = 25 kips

and $\Sigma F_y=0$

16.5 - 20 -30 + Hy = 0

Hy = 33.5 kips

b) On an unloaded and unsupported joint where 3 members meet, the 2 collinear members are equal and the third member is a zero force member

The zero force members are identified by a 0 mark in the figure below

0 0 0 0 0

c) Consider a section cutting through members MN, CN, CD as shown

Fun Áy F-20

Taking moment about C,

-16.5 x (16 x 2) - Fmn x 12 x 2 = 0

FMN22 kips (Compression)

C 3 1 、las 3(87 As