# Discovering OpenSees -- Modeling SCB frames using beam-column elements

### From OpenSeesWiki

**This seminar will occur on January 30 & 31**

Register for the seminar:

- January 30 at 10:00 am Pacific Time registration link

- January 31 at 4:00 pm Pacific Time registration link

Special Concentrically Braced Frames (SCBF) are commonly used as the seismic resisting system in buildings. During large seismic events they may experience buckling of the braces. These inelastic deformation of the braces place inelastic deformation demands on beams, columns and connections. Although the most accurate way to analytically capture the response of such systems is by using continuum models (based on shell or brick elements) it is time consuming and computationally expensive. Simplified but relatively accurate nonlinear model of a SCBF can be developed in OpenSees using beam-column (line-frame) elements. Such model can provide accurate simulation of global behavior, while retaining simplicity and providing reasonable predictions for many local behaviors. Force-based beamâ€“column elements can be used to model the braces, beams and columns. Simulation of brace-buckling behavior can be achieved by using several nonlinear elements along the length of the brace that include nonlinear geometric effects and have perturbed geometry to simulate imperfection of the brace. Generation of such a model with three models of gusset plate connection will be demonstrated in this webinar. These include modeling of gusset plate using: (i) nonlinear elements, (ii) rotational springs, (iii) pins. While the first two models of the gusset plate connections can provide accurate responses of the system, the pinned gusset plate connection results in significant loss in accuracy.

This web-learning series covers:

- Description of different modeling approaches of SCBFs
- Generation of modeling SCBF using beam-column elements considering 3 different models of gusset plate connections (demonstrated on an example)
- Comparison of seismic responses of a SCBF considering different gusset plate modeling approaches (demonstrated on an example)
- Consideration of further simplifications of the model (demonstrated on an example)
- Conclusions and summary

**PPT presentation of the seminar can be found here:**

**Video of the seminar can be found here:**

**Example: one story one bay SCBF with chevron configuration of braces:**

- SCBF-2Dmodel.zip (2D model of a braced frame with in-plane geometric imperfection)
- SCBF-3Dmodel.zip (3D model of a braced frame with out-of-plane geometric imperfection)