November 13, 2019

Upgraded Solution Speed using Multi-Core Processing

Tags: RISA-3D, v18, New, Solution, Multi-Core

April 6, 2011 | Seismic, RISA-3D, Loads, RISAFloor, New

What are the Unbalanced Forces on Beams?

V-Brace frames in RISA-3D seismic design have unbalanced forces shown on both the beams and braces. As brace frames displace under lateral loads, one brace will buckle and its force decreases while the other brace in tension will have an increase of force until it reaches yield. The beam and connections must have enough strength to resist this unbalanced vertical force. The brace forces are shown in the beam and brace detail report as well as the resultant unbalanced force per AISC 341-10 Section 13.4. RISA-3D does not automatically apply these forces to the beams. To account for the unbalanced vertical force in your model, you can apply these vertical point loads in RISAFloor without the braces present…

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

How to Use Seismic Factors in Load Combinations in RISA-3D

RISA-3D now has the ability to define the seismic parameters Rho, Omega and SDS directly into load combinations. If you open the Basic Load Cases spreadsheet and click into the BLC column, the dialog offers the ability to add these values in to factor the load. Here we will see that Rho and Omega can only be used if the Load Category Code is set to a seismic option. Sds can only be used if Dead Load is selected. Once you apply this factor it is automatically taken into account without the use of the Factor column in the Load Combinations spreadsheet. The actual values for these factors are defined in the Seismic tab of Global Parameters. Rho is specified in section 12.3.4 of the ASCE 7-16. Omega is specified in Table 12.2-1. SDS is used for the vertical portion of seismic load and is typically multiplied by 0.2*DL in Section 12.4 combinations…

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…