Hello doctor .
In relation to how to obtain the value of the length of the border area of the shear wall (c) by the etabs program, I did not find any reference or numerical example in the references.
If possible, please advise.
In general, according to ACI318, the design of the boundary element of the shear wall can be done in the following two ways:
In general, there are two methods to determine the need for a boundary element in a shear wall:
1- Based on strain: which in this method is determined based on the displacement of the boundary element wall. The control of this item is found in clause 18.10.6.2 of the ACI318-14 code.
2- Based on stress: In this method, it is determined based on the maximum stress created in the farthest web of the boundary element wall. The control of this item is found in clause 18.10.6.3 of ACI318-14.
ACI318-14
18.10.6.1 The need for special boundary elements at the edges of structural walls shall be evaluated in accordance with 18.10.6.2 or 18.10.6.3. The requirements of 18.10.6.4 and 18.10.6.5 shall also be satisfied.
Necessity of using boundary element based on strain:
If hw/ℓw ≥ 2.0, it needs a boundary element if the following relationship holds.
c>(lw/(600(1.5Du/hw))
where c is the maximum depth of the neutral web for factored loads and anchors. Du/hw value should not be less than 0.005.
Also, if there is a need for a border element according to the above relationship, the transverse reinforcements should be extended at least to the maximum of two values of ℓw and Mu/4Vu along the vertical, top and bottom of the critical section.
The need to use the boundary element based on stress:
In shear walls, where the stress value in the furthest web under factored loads including earthquake force exceeds 0.2fc’, they need a boundary element. This boundary element can be cut in the length of the piece where the compressive stress of concrete is less than 0.15fc’. If the wall has wings, the effective width of the wing should be taken into account.
In the ETABS program, when special wall ductility is considered, the length of the wall boundary element is calculated. According to paragraph 18.10.6.3, the program does not calculate the boundary element if the value of the compressive stress in the farthest webs of the wall is less than 0.15 fc’. This length is different according to each combination of design loads in which there is an earthquake force. Also, the boundary element length control program performs and reports based on the strain and limit mentioned above.
Structure Design Question Group link
(Assembly of Designers of Tabriz)
@Tabrizporsemancivil
This post is written by AminNajafgholizadeh