October 29, 2020

Interaction of Shear Forces Acting Along Orthogonal Axes in Concrete

Recent tests and analytical results for concrete columns have indicated that considering shear along each centroidal axis independently can be unconservative. Therefore current versions of RISA-3D, RISAFloor and RISAFoundation have included the consideration for the interaction of shear forces acting along orthogonal axes per ACI 318-19 equation 22.5.1.11.

When Vu/ΦVn > 0.5 in both orthogonal directions, a new expandable section of the Detail Report will appear for the interaction equation.

RISA-3D

RISAFoundation

Tags: RISA-3D, RISAFloor, Concrete, RISAFoundation, New, v15, v19, v13

October 29, 2020 | RISA-3D, RISAFloor, Concrete, RISAFoundation, New, v15, v19, RISAFloorES, v13

Updated Shear Contribution for Concrete (Vc) per ACI 318-19

The new ACI 318-19 code has been implemented into RISA-3D v19, RISAFloor v15, and RISAFoundation v13. One of the biggest changes between the ACI 318-14 code and the ACI 318-19 code is the shear contribution provided by the concrete, Vc. ACI 318-14 In ACI 318-14, a simplified equation for the calculation of Vc could be used unless there is axial force present in the member. The area of shear and flexural reinforcement in the cross section was not a consideration when determining the shear strength contribution of concrete using the simplified equation. ACI 318-19 Now, in ACI-318-19, the calculation of Vc is dependent on whether the area of shear reinforcement provided, Av, is lesser or greater than the minimum area of shear reinforcement required, Av,min. When Av > Av,min, the axial load and the flexural reinforcement ratio are included in the calculation of Vc. ACI allows us to use the larger of the results from equation (a) and (b) in the table. In RISA-3D detail report, this calculation will be presented in the shear design tab: When Av < Av,min, ACI 318-19 introduces a new variable, the size effect modification factor, λs. Experimental tests have indicated that the shear strength…

October 30, 2020 | RISA-3D, Results, New, v19

Improvements to Solid Elements in RISA-3D

A number of improvements have been made to solid elements in RISA-3D v19 allowing users enhanced flexibility in viewing input data as well as evaluating results associated with solid elements. Solid Primary Data Spreadsheet Once solid elements have been drawn, you now have the option to view their properties in the Solids spreadsheet. From within the spreadsheet, the material type and the activation of solids may be modified. Internal Force Summation Tool The Internal Force Summation Tool (IFST) is now available to be used on solid elements. Similar to plates, you will select the IFST from the ‘Selection Toolbar’ on the left side of the 3D window. To define the cutting plane, select two nodes. This will define the start and end of the cutting plane as well as lock the cutting plane to that exact location. The Internal Force Summation Tool uses a new axis so it's important to view your model in the Plan or Elevation View to get accurate results. Clicking a third time will initiate the Internal Force Summation results dialog. The axes shown in the dialog correspond to the direction in which the cutting plan was selected with the "1" direction running along the line…

April 7, 2020 | RISA-3D, Concrete, New, Shear Walls

Understanding Out-of-Plane Shear Capacity of Concrete Wall Panels

When designing concrete shear walls for lateral loading, RISA-3D includes design checks for both in-plane and out-of-plane shear. In the condition where a concrete wall is under both axial tension and out-of-plane shear, the out-of-plane shear limit state for a specific region within the concrete wall detailed report includes the details shown below: This limit state may cause users to ask the question: “why is the a phi*Vns term listed when no out-of-plane shear reinforcement is present?” The answer is that when calculating the out-of-plane shear capacity of the concrete wall, RISA-3D considers Shear Friction developed at the crack interface. ACI 318 code defines shear friction as the shear transfer across any given plane, such as an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times. In this case, the existing/potential cracks condition applies. When axial tension and out-of-plane shear are applied to the concrete wall, cracks will form across the wall thickness as explained by the simplified force diagram shown below: The shear sliding at the crack generates tensile forces Fs in rebar. In return, these tensile forces, Fs cause compression forces, Fc at the concrete crack interface. The…