BALCONY PARAPET WALLS

Entering non-structural walls into the StatiCAD-Yigma program may lead to incorrect analysis results.

Earthquake code Article 5.8 states that walls with a gap of at least 10 mm between the top of the wall and the ceiling slab are considered non-structural.

By default, the program treats all entered walls as structural and calculates wall stiffnesses according to the earthquake code stiffness formula (k*A/h). Since no alternative formula is provided in the earthquake code, the same formula is applied regardless of whether the walls are connected to the slab (rigid diaphragm) or not.

In a building with a storey height of 3 m, parapet walls with a height of 1 m will be three times stiffer than a wall of the same area with no adjacent doors or windows. (Since H appears in the denominator of the stiffness formula.) Because stiffness values are assigned to the walls, results may emerge as if the balcony walls carry a significant portion of the storey seismic load. In this type of modelling, the results will deviate from the calculation principles required by the earthquake code, and a risky building may appear safe, or a safe building may appear risky.

Balcony walls can be entered into the system with the stiffness coefficient set to zero (k=0) by assigning a special value in the wall property modification window. In this case, walls assigned a stiffness coefficient of zero will not be included in the shear force calculation. However, since vertical load transfers in the program are defined independently of wall top elevations, these walls may receive load from the upper storey in vertical stress calculations.

For this reason, we are of the opinion and conviction that balcony parapet walls (if not connected to the upper floor slab) should be entered into the structural model as loads only, and not as walls.

We kindly request that our users and the relevant authorities pay due attention to this matter in order to avoid calculation errors...

ÖZDEMİR YAZILIM