
July 14, 2011
Varying Soil Properties in RISAFoundation
While RISAFoundation has a Default soil properties (Subgrade Modulus and Allowable Bearing), it is possible to create regions of varying soil properties.
With the adoption of ASCE 7-22, the concept of a multi-period response spectrum has been added to seismic design requirements. While this provides more accurate hazard representation, it also means engineers need to generate and input additional site-specific data. This quick workflow shows how to gather that data from the ASCE Hazard Tool and use it in RISA’s site parameters table for seismic load generation. Why This Matters for Engineers? Multi-period response spectra reflect more realistic ground motion characteristics and will increasingly be required as jurisdictions adopt ASCE 7-22. By pulling site-specific values directly from the ASCE Hazard Tool, engineers can ensure compliance and avoid unnecessary assumptions. The multi-period approach can result in higher or lower design forces depending on the building’s period and site class, but it always provides more accurate seismic representation than the traditional two-point method. Download the latest versions of RISA that supports ASCE 7-22 below. Step 1: Generate Multi-Period Spectrum Data Go to the ASCE Hazard Tool. Enter your project location (address, coordinates, or site description). Select ASCE 7-22 as the building code. Navigate to the seismic hazard results and download/export the Multi-Period Response Spectrum data. Step 2: Copy Data Points into RISA Open RISA…
Read More
While RISAFoundation has a Default soil properties (Subgrade Modulus and Allowable Bearing), it is possible to create regions of varying soil properties.
Modeling built-up or composite sections can easily be done in RISASection. Because the properties of such a section are computed using a weighted summation of the transformed shape properties, RISASection uses a Property Multiplier to specify the relative weight of a single shape in a built up...
In order to model built-up or composite sections, RISASection includes the Property Multiplier, an input value which specifies the relative weight of the shape’s modulus of elasticity to that of the overall section. This value can also be used to model a void or a hole in the shape.
RISAFoundation has the capability to report soil bearing pressures, and check them against allowable pressures.
While RISA-3D (or RISA-2D) does not have an explicit tool to punch a hole in a plate, you can use the following steps to manually model them:
Have you ever received an instability warning when running a three dimensional RISA-3D model? This is because RISA-3D cannot build the stiffness matrix with the configuration you have modeled. In some cases, your model is truly unstable and in others it’s a matter of correctly modeling your...
In RISAFloor on the roof level, you layout only the top chords of the truss and create your slope. These top chords by themselves probably won’t be sufficient enough to get designed in RISAFloor, but, don’t worry, we’ll take care of that in RISA-3D when we model the rest of truss.
In RISAFloor, the beams are susceptible to two forms of buckling; Euler buckling and lateral-torsional buckling. The unbraced length is determined in RISAFloor using the deck properties and framing.
Using this method in RISAFloor, we are not actually designing the trusses, but just adding “dummy” bottom and top chords to correctly calculate the loading and help distribute the loads to the walls.
Our monthly "Structural Moment" newsletter is the best way to keep up with RISA’s product updates, new releases, new features, training events, webinars and more...