Civil Engineering Reference
In-Depth Information
17
Two-Way Slabs, Equivalent
Frame Method
17.1
MOMENT DISTRIBUTION FOR NONPRISMATIC MEMBERS
Most of the moment distribution problems the student has previously faced have dealt
with prismatic members for which carryover factors of
1
2
,
fixed-end moments for uniform
loads of
w
u
2
/8, stiffness factors of
I
/
, and so on were used. Should nonprismatic mem-
bers be encountered, such as the continuous beam of Figure 17.1, none of the preceding
values apply.
Carryover factors, fixed-end moments, and so forth can be laboriously obtained by
various methods such as the moment-area and column-analogy methods.
1
There are vari-
ous tables available however, from which many of these values can be obtained. The ta-
bles numbered A.16 through A.20 of Appendix A cover most situations encountered with
the equivalent frame method.
Before the equivalent frame method is discussed, an assumed set of fixed-end
moments are balanced in Example 17.1 for the nonprismatic beam of Figure 17.1.
The authors' purpose in presenting this example is to show the reader how moment
distribution can be applied to the analysis of structures consisting of nonprismatic
members.
Figure 17.1
1
McCormac, J. C., 1984,
Structural Analysis
, 4th ed. (New York: Harper & Row), pp. 333-334, 567-582.
539
