
October 26, 2018
What’s New in the NBC 2015?
The 2015 NBC compliant codes have been implemented into RISA-3D v17.0, RISAFloor v13.0 and RISAFoundation V.11.0!
In structural engineering, few design challenges are as rewarding—or as unforgiving—as the tall building. While gravity systems and code checks form the backbone of any structural project, once a structure rises beyond ten or fifteen stories, a shift occurs. Wind and seismic forces begin to dominate. Story drift and torsional irregularities become non-negligible. Load paths grow increasingly indirect. And design decisions, if not carefully made early on, can have exponential consequences higher in the structure. Tall buildings are not simply “bigger” versions of short ones. They behave differently. And understanding those differences is essential for any engineer working in an urban environment where building vertically is often the only viable path forward. Modeling for Reality, Not Just Code The foundation of any successful tall building design lies in the model—its assumptions, resolution, and degree of abstraction. Many engineers begin with simplified representations: rigid diaphragms, idealized connections, and linear material properties. This is practical and often sufficient for early design phases. But as the building increases in height and complexity, those assumptions may start to mask critical behaviors. Semi-rigid diaphragm modeling, for instance, allows engineers to capture in-plane flexibility of floor systems—especially important in buildings with irregular cores, open floor plans,…
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The 2015 NBC compliant codes have been implemented into RISA-3D v17.0, RISAFloor v13.0 and RISAFoundation V.11.0!
The 2016 edition of ASCE Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16) is now available in RISA-3D v17.0, RISAFloor v13.0, and RISAFoundation v11.0!
Eurocode lateral torsional buckling capacity is calculated per equations in Annex F in the ENV 1993-1-1:1992. This calculation uses variables C1, C2 and C3. Since there is no generic formula in the Eurocode to calculate the moment gradient factor, C1, RISA will use the widely accepted López, Yong...
With the initial implementation of wood wall design in RISA-3D, the wall aspect ratio was calculated as the full height of the wall divided by the width of the region.This was intended to accommodate balloon framed multi-story walls that were drawn as one continuous wall stack. With recent...
With the recent release of RISA-3D v17 the program now offers the user the option to use Chord Straps between floors of a wood shear wall building in lieu of using hold downs. Chord Straps are a great option for transferring tension load between floors of a multi-floor building and can be installed...
RISA-3D v17.0 now has the ability to model partial fixity member end releases. Partial fixity end releases can be utilized in RISA to model the behavior of a partially restrained or semi-rigid connection that cannot be idealized as fully fixed or pinned. Partially restrained connections are common...
The new AWC NDS 2018 code has been implemented into RISA-3D v17.0 and RISAFloor v13.0. To select this code for your design, simply choose this code from the Codes tab within Model Settings.
RISA-3D v15 includes "analysis offsets" which moves the centroid of the member for analysis allowing for flexibility in how members are designed. Let's use a WT brace to demonstrate how this feature can be utilized. When you model a WT brace it exists at the member centroid, which means that no...
In a previous article we discussed how the Analysis Offsets feature in RISA-3D works and how it can be used to model members at top of steel. In this article, we will discuss some specific situations and how the results change with the analysis offset set as top of member (local -y axis).
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