Simply supported

To be continued >

Behaviour and reinforcement of one-way staircase

The deformation and the cracking due to flexure (which at this figure are presented magnified), are similar to those met in the horizontal one-way slab, and therefore the necessary reinforcement is also similar.

Behaviour and reinforcement of one-way staircase connected to slabs

Due to the continuation of the staircase to slabs at its base and top, negative bending moments are formed at the supports (upper fibers tension) and therefore rebars are required at the upper fibers at both ends.

Staircase starter rebars

In order to achieve a connection with the subjacent floor there must be properly placed starter bars. Moreover, starter bars must be positioned and at the superjacent floor for the staircase of the next level.

Placement of staircase starter rebars

Before the positioning of the staircase’s formwork (planking), the starter bars are properly bent at the necessary height (of course they could be placed already bend-up, however, this entails accuracy difficulties).

Staircase formwork and reinforcement at the starter bars

During the final phase of the positioning of the staircase’s reinforcement, the lower rebars (in red color) are tied to the distribution bars to their proper position. The next phase includes the positioning of any necessary additional upper rebars followed by the placement of their distribution bars. The stringers and the risers are placed last.

Starter bars at the top of the staircase

Starter bars at the top of the staircase (the lower rebars of the staircase are not continued into the staircase slab and therefore, they are not presented).

Staircase construction in a following phase

The staircase that will be constructed in a following phase will be supported on those starter bars and the starter bars of the lower floor.

Reinforcement of staircase with landings

The flights of the orthogonal staircases are not always straight. On the contrary, most of the times they are polygonal chains with successive sloped and horizontal segments.
When the staircase contributes to the seismic diaphragmatic behavior of the floors (as is the rule), it is recommended to use negative rebars as well [dashed bar (7)].
The negative rebars, apart from everything else, help in the proper concreting of the staircase’s sloped flights because they retain the wet concrete in a satisfactory degree.