CHAPTER XIV.
EFFECT OF SHOCK ON BUILDINGS—FIFTH MODIFYING CONDITION—EFFECTS OF APERTURES ETC. IN WALLS.
We at length come to the fifth and last head of constructive modification, as affecting and affected by, the shock, viz., the effects of wall apertures, windows, doors, &c. A few words of illustration will be sufficient for this. Assuming the simplest case, as in Fig. 86, of a normal
wave; whenever the wall is pierced by one or several rectangular or other apertures, it may be viewed as divided into different segments such as that , , , each having a separate moment of stress of its own, and giving rise to a separate dynamic couple, the extremity of one arm being in the centre of gravity, , the other at the base and junction with the similar adjoining segments, the ten-
