This mode enables to perform a check of a given structure of a rectangular area of a solid slab. Depending on the ratio of the lengths of their sides slabs can be classified into those bent in one direction and those that can be bent in two directions.
The area of a slab can be either a separate structural member of a building or a structure (e.g. a floor panel over a rectangular opening) or a part of a ribbed slab. The load-bearing capacity of the slab is determined from the limit equilibrium conditions according to a procedure given in the Guide to SNiP 2.08.01-85 and the Instruction manual for the analysis of statically indeterminate reinforced concrete structures with the consideration of the redistribution of forces.
To perform the check of a slab, a limit value of the uniformly distributed load is compared with the total load from the specified load cases.
The application performs the check of:
Boundary conditions of the slabs:
(a) for slabs bent in one direction, the boundary conditions are specified only on two sides. At least one side of the slab should be clamped. The other side of the slab can be clamped, simply supported, or free from support. This combination of the boundary conditions enables to model end and middle spans of continuous "beam-like" slabs. The second and the next spans of the continuous slab are not distinguished between one another. In all cases, the distribution of internal forces is assumed to be the same as that for the second span from the slab edge. Moreover, these boundary conditions enable to analyze the slab as a separate structural member in all practically important cases:
(b) for slabs bent in two directions, the sides can be either clamped or simply supported. One of the shorter sides of the slab can be free from supports.
In all cases, the loads are assumed to be uniformly distributed over the area of the slab.
The slabs are checked for strength and crack resistance in compliance with the regulations of SNiP 2.03.01-84* (KMK 2.03.01-96, SP 52-101-03, SP 63.13330).
Data are prepared in the following tabs: General, Loads, Concrete, and Crack Resistance.
This tab is used to enter the data which describe the structure of the slab, the diameter, class, and spacing of rebars, and the diameter of anchor bars (for slabs bent in two directions), the thickness of lower and upper concrete covers, service factor for reinforcement, and the allowable deflection value. Anchor bars can be installed only on the clamped sides of the slab. The reinforcement class for the anchor bars is assumed to be the same as that for the primary reinforcement. It is assumed that the anchors are made of single rebars installed in one row.
In order to select a structure of the slab, you have to use the respective radio button to indicate the type of its behavior (bent in one or two directions), specify the thickness of the slab, and its sizes along axes X (Lx) and Y (Ly). If the ratio of the lengths of the sides is less than or equal to 3 (i.e., \( \frac{L_{x} }{L_{y} }\le 3 \) or \( \frac{L_{y} }{L_{x} }\le 3 \)), the slab should be considered as bent in two directions. For a slab with one free edge, bent in two directions, the ratio of the length of the clamped edge to the length of the free edge must not exceed 1.5.
Boundaryconditions for every face of the slab are specified by selecting the respective radio buttons: Free (edge), Hinged (edge), or Clamped (edge), which indicate the way the slab bears on its supporting structures or the way the slab area bears on the supporting ribs. For clamped faces, the Anchorage group of checkboxes is used to indicate the presence of anchors.
Active columns and rows in the slab reinforcement table depend on the specified design.
The Areas button enables to obtain the reference information about the areas of reinforcement per running meter of the slab.
The slab is checked for the action of only uniformly distributed loads over its whole area. The user has to reduce the loads to the uniformly distributed ones. This tab is used to specify the uniformly distributed loads. The slab is analyzed only for one combination of loads.
The tab contains a checkbox, Add the self-weight of slab. If the checkbox is checked, the application will automatically add the load from the self-weight to the list of loads.
When specifying the loads their simplified classification is used (permanent, long-term, short-term). It is assumed that permanent and long-term loads do not have a short-term part, and the short-term load does not have the sustained one.
Properties of concrete are specified in the Concrete tab in the standard way.
Data on crack resistance are specified in the Crack Resistance tab according to the standard rules.
The result of the check is a value of Kmax (the maximal factor) which is displayed at the bottom of the dialog box. A complete list of all factors (checks) can be obtained by clicking the Factors button. This will open a standard dialog with a list of all checks.
A report can be generated on the basis of the results of the calculation (the Report button).