June 7, 2012

How to Apply Hydrostatic Loads to Circular Tanks in RISA-3D

RISA-3D v10 now has the ability to quickly and easily apply hydrostatic loads to circular tanks using the Cylinder Generator. This generator can be found by clicking the Templates button and choosing the Cylinder - Plates/Members option.

This generator provides a quick and easy method of modeling an entire structure, or just giving a starting point on a more complicated model. As you can see when you generate the structure, the program automatically steps your hydrostatic loads to form a triangular distribution over the height.

Tags: RISA-3D, Loads, New

March 28, 2019 | Seismic, RISA-3D, New

Assigning Seismic Loads in RISA-3D

RISA-3D has two ways of automatically generating seismic-related Basic Load Categories (BLCs) which can be later referenced in the Load Combinations (LCs): 1. Creating seismic BLCs (ELX, ELZ, etc) from the Seismic Load Generator 2. Creating seismic BLCs (SX, SZ, etc) from Response Spectra Analysis In addition to the automatic generated seismic loads, users can always draw any loads and add them to seismic load consideration. How to generate seismic loads from the seismic load generators are further discussed here: How to create seismic loads from response spectra analysis is further discussed here: Once the seismic-related Basic Load Categories (BLCs) are created, they can be used in analysis by referencing them in the Load Combinations (LCs). RISA-3D also has Load Combination (LC) Generators that will generator seismic-related combinations based on selected codes. How to use the LC generator is further discussed here: The seismic load categories (ELX, ELZ, etc.) generated from the Seismic Load Generator can also be viewed visually from the load display. The seismic load categories (SX, SZ, etc.) generated from Response Spectra Analysis cannot be viewed visually, but users can check the total base reactions from the joint reaction spreadsheet as a reflection for the applied lateral…

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…

June 17, 2016 | Seismic, New, RISAConnection

Why Do Seismic Brace Story Forces Change My Existing Code Checks?

It is possible for seismic (OCBF or SCBF) vertical braced connections to have some limit state code checks lower than those for the same non-seismic connection. This is due to the assumptions that RISAConnection makes when calculating the axial load in the beam. Non-seismic vertical brace connections only have a single beam axial load input value. Because seismic vertical brace connections require separate frame analyses of the various possible load directions, it is not appropriate to use a single input brace axial load for all load direction cases. Doing so could cause un-conservative results. Therefore, RISAConnection calculates the beam axial load for each loading direction case. Story Force and Beam Axial Force Calculation The beam axial load calculation is done for each applicable loading direction case. To see the details of these calculations, please see the Seismic Load Distribution on the new Seismic tab of the results report. The procedure is based on that used in example 5.3.5 of the AISC Seismic Design Manual. It is determined using simple statics and the following assumption: The input connection is mirrored on the other side of the bay with an equal and opposite braced connection. Assuming this assumption, the story force and…