March 25, 2020

Seismic Design of Steel Structures in RISA-3D

RISA-3D includes the ability to design steel structures for seismic provisions found in AISC 341 and AISC 358 including moment frames and braced frames. For more information, review the video below.

Tags: Seismic, RISA-3D, New, Steel

March 30, 2011 | Seismic, RISA-3D, New

How to Apply the Seismic Provisions in RISA-3D

The Seismic Provisions in RISA-3D will check various design and code check requirements according to the AISC design provisions (AISC 360-2005, AISC 341-2005, AISC 358-2009). Seismic Design Rules can be applied to any member in the model, just follow the steps listed below. Step 1: Define the Seismic Design Rules. The Seismic Design Rules spreadsheet can be found on your Data Entry Toolbar or in the Spreadsheet menu. To learn more about seismic design rules, read What Are the Seismic Design Rules in RISA-3D. Link: What are the Seismic Design Rules in RISA-3D? Step 2: Assign the Seismic Design Rules to your member by going to the Properties panel and expanding the Design Properties menu. Step 3: Set the Seismic Overstrength (W) factors in Settings on the Seismic tab. Step 4: Create the Overstrength Load Combinations Now you are ready to run your model and review your results…

February 28, 2011 | Seismic, RISA-3D, Loads, New

How To Generate Seismic Loads Automatically in RISA-3D

Applying seismic loads to structures with rigid diaphragms can be done automatically in RISA-3D. In the image below we have a structure that has rigid diaphragms and the seismic load has already been applied at each diaphragm level. To do this, go to Advanced > Seismic Loads and input the code and the necessary parameters to calculate the seismic force in the structure. Note that we also need the Seismic Weight defined in a load combination that we choose here. Once we hit the Calc Loads button the program calculates the forces at each diaphragm level in each orthogonal direction and gives the parameters used to calculate these forces. For the ASCE 7-05 code the program uses the Equivalent Lateral Force Procedure. If we then hit Generate, these loads are added to your Basic Load Cases automatically. RISA-3D also automatically provides accidental eccentricity Basic Load Cases prescribed for rigid diaphragms…

November 2, 2016 | Seismic, RISA-3D, New, Loading

Basic Code Terms for Seismic Behavior and Why We Use Them

Seismic Forces are generated automatically using seismic parameters R, SD1, and SDS in the Seismic Load Generator when using the Director to go from RISAFloor to RISA-3D or when inserting Seismic Loads on a rigid diaphragm in RISA-3D. Additionally, Seismic Load Combinations can be generated using the seismic parameters ρ, Ωo, and SDS and applied to the structure. These seismic parameters are used to approximate the inelastic response of the structure subjected to seismic design lateral forces. Figure 1 shows a simplified example of what some of the seismic parameters represent when looking at force versus drift for a lateral system. In RISA-3D, the seismic load generator is accessed by selecting the Advanced tab and then clicking on Seismic. When the load generator opens and the loads are calculated the dialogue looks like the image below. R is the Response Modification Factor as defined in Table 12.2-1 of ASCE 7-16. It provides a reduction for the design seismic force based on the ductility of the system. The program offers a single user-input R value in each Global direction. R is used in the calculation of the Seismic Response Coefficient, Cs, which determines the Seismic Base Shear, V, and these values…