Connection Verification: Capacity Design
A joint’s capacity design is evaluated as a part of a seismic check, and its results help to determine whether or not the joint has adequate deformation capacity. The purpose of capacity design is to ensure that a structure exhibit controlled ductile behaviour in order to prevent it from collapsing in the event of an earthquake of the level it was designed for. Decisions on which parts of a structural system are elastic and which are ductile are made during a process called Capacity Design.
For e.g. in the Beam column moment connection, the dissipative element is selected as a beam with the factors Ry & Cpr (AISC 341-16 – Table A3.1), strength hardening factor. Plastic hinge is anticipated to show up in the dissipative item, and all non-dissipative items of the joint must have the capability to transfer forces in a safe manner due to the yielding in the dissipative item. For more information on how capacity design is handled in IDEA STATICA, please visit: Capacity design (AISC) | IDEA StatiCa
One solved example given in AISC Design Guide # 4 is selected and analyzed/designed in IDEA STATICA. Connection Verification – DG # 4. Eight-Bolt Extended Stiffened (8ES) End-Plate Connection.
- Beam: W21×55 (ASTM A922 steel)
- Column: W14×109 (ASTM A922 steel)
- Bolts: ASTM A490
- Plates = ASTM A572 Gr. 50
- Vu = is 40 kips.
- Connection Design Moment = Mpe = 7623 k-in
- Location of Plastic Hinge = 10.4 in
Verification/validation has been done for the 8ES (Eight-Bolt Extended Stiffened (8ES) End-Plate Connection) of AISC Design Guide-4. It has been observed that, the connections passed in all respect. The results show intended location of plastic hinge.
Just for Trial purpose, the above connection has been checked using ¾” dia.-A325N bolts. However, the connection has failed showing Plate failure (Top stiffener exceeding 5% strain) and Bolts exceeding capacity to 108% > 100%.
With the above exercise, it can be concluded that, the capacity design is handled by Idea STATICA well.