|
49. Problem 13.52P (HRW) A tunnel 150 m long, 7.2 m high, and 5.8 m
wide ( with a flat roof) is to be constructed 60 m beneath the
ground. The tunnel roof is to be supported entirely by square steel
columns, each with a cross-sectional area of 960 cm2. The density of
the ground material is
|
. (a)
What is the total weight that the column must support? How many columns are
needed to keep the compressive stress on each column at one-half its ultimate
strength?
|
Solution: Click For PDF Version Dimensions of the tunnel are length,
Depth of the tunnel from the ground,
Volume of the ground material above the tunnel,
Density of the ground material,
Weight of the ground material on the tunnel,
It is given that the planned maximum compression stress on
each column is
Therefore, number of concrete columns, N, required in the tunnel is given by the expression
|
,
width,
, and
height,
. 
.
.
of the
ultimate strength of concrete, that is
.
Cross-sectional area of each column is
.
Therefore, maximum force that each column can support will be
