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Before going in depth into the subject of this article we think it would be convenient to remember what CEDRUS options are necessary to, on the one hand, develop full building models and, on the other, subject horizontal loads on them:

**Option G:**With the help of this option it is possible to**generate geometric 3D models of buildings**by simply overlapping 2D slabs at the right heights. This option also allows the generation of a**calculation model for overlapped slabs**to directly lower the loads to the foundations.**Option H:**The models generated with option G constitute the base to use option H for**horizontal loads,**giving access to more advanced calculation models. With it, it is possible to consider the horizontal actions when lowering the loads (wind, earthquake, etc) and**it automatically generates framework models**for an advanced analysis in STATIK.

When the geometry of a building is entered completely in CEDRUS, the introduction of horizontal loads is carried out using the corresponding tab, ‘Horizontal loads’:

When we want to add a new load using the button The following dialog box appears:

In it we can select the name of the load hypothesis, the type (wind, earthquake, ground pressure or others) and the point of application (origin, centre of mass or centre of stiffness). Additionally we have another 3 options:

The third of them (used for the slab dimensioning) being the one of interest for this subject.

With CEDRUS’ building modules it is possible to see a very clear graphic representation of the geometry of the different slabs that are entered with the program and to carry out various models for their analysis. The simplest and most used one is the so called ‘**model of overlapped slabs**’ with which one can lower the vertical loads to the foundations. On the other hand, is one has the horizontal loads module, ona may have easily entered wind loads, ground pressures, etc.

The horizontal loads will be taken into account in the load lowering so that, once the geometric model has been generated, if we click on the lightning icon to solve the overlapped slabs model, each storey will export a series of loads to the storey below it, which will do the same to the one on top.

Let’s see an example to better understand how the program works with horizontal loads:

**- FULL BUILDING MODEL**

**- LOWERING LOADS CAUSED BY PERMANENT LOADS ‘G’**

**- IMPORTING THE PERMANENT LOADS ‘G’ FROM SLAB 3 TO SLAB 2**

The third option shown above, ‘Use for slab dimensioning’ will allow (if activated), when analysing of one of the floor slabs separately, seeing, in the loads tab, a hypothesis corresponding to the horizontal load which it is desired to consider.

We are going to create firstly a horizontal load that we will call ‘WIND’ which is equivalent to a 100 kN point force on each of the storeys (except for the lower level L0).

**- IMPORTED LOADS FROM SLAB 3 TO SLAB 2 IF THE OPTION IS NOT SELECTED**

The hypotheses with the name starting with ‘!Imp-’ are the ones imported from the top slab. In this case we see that none of them corresponds to ‘WIND’ (because we decided not to include it).

**- IMPORTED LOADS IF THE OPTION IS SELECTED**

We see that among the hypotheses that have been imported from the storey on top, the ones corresponding to ‘WIND’ is there. Its loads distribution over the storey would be:

And in the opposite sense:

These loads will generate a series of forces on the slab that, depending on the magnitude they could even affect its reinforcement. Generally, the magnitude of the forces that the horizontal loads generate on the slab are going to be way lower than the ones due to gravity loads but being strict, this is the way of including them.

Let’s see, for example, the bending moments ‘mx’ resulting from the load: ‘WIND’

**- MOMENTS ENTERED IN THE SLAB DUE TO THE ‘WIND’ LOAD (+ve SENSE)**

**- MOMENTS ENTERED IN THE SLAB DUE TO THE ‘WIND’ LOAD (+ve SENSE)**

In conclusion, it is important to have in mind that, if the horizontal loads are not regarded for the slab dimensioning, the vertical elements of the building will have to be dimensioned to support 100% of them. If, on the contrary, they are taken into account and it is considered that the floor slabs collaborate to resist those loads, the slabs will have to be designed accordingly.

It is recommended for the reader to check the article that explains the types of framework models that we can generate from the full model of a building using option H and its implications in STATIK.

## Comments

1 comment

why does wind load have no effect on the top slab of building (slab 5)?

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