Bricks and plain concrete can not be used directly as flooring system without proper strengthening. Either reinforcement can be provided or provision can be made so as to develop arch action.
Rolled steel joists (RSJ) are used to build arches so as to form jack arch floorings. The arches have spares varying from 1.25 to 2 m and the rise is 1/12th to 1/16th of the span. In order to accomplish the end thrusts the rods of 2–2.5 cm are run at 2–2.75m apart as shown in Fig. 23.7. The rods are encased in the wall along with a RSJ. The spandulus are filled with concrete.
Brick jack arches are constructed by bringing up the arches by laying the bricks on edges starting from the ends where the bottom of an RSJ is concreted. Lime or cement mortar is used. After laying the brick from ends, the key brick is introduced to set the arch action. Next layer is laid by pushing the centering ahead. This operation is continued till the work is completed.
Figure 23.7 Brick jack arch floor
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