January 1, 2021

Consideration of Openings for Punching Shear of Two-Way Slabs in…

Punching shear of two-way reinforced concrete and post-tensioned slabs is a critical design consideration. The presence of openings near a support can complicate the calculation of shear capacity at the location. ADAPT-Builder v20 now includes enhancements in how openings are treated near columns and walls that are checked for punching shear in the software.

In previous versions of ADAPT-Builder, an opening in the vicinity of a column was treated the same as slab edge regardless of its size. For example, when a small opening is close to a column, the whole side of a column is disregarded from the punching shear check, which is conservative in many cases.

For ADAPT-Builder 2020 the check for punching shear has been improved in the detection and handling of openings as per ACI code requirements. This new method for handling of openings is enabled when an ACI code version is selected. Two new input parameters are shown in the Punching Shear input dialogue. These include:

Radius of detection – This setting is used to determine at what distance from the face of support will openings be detected and deducted from the critical sections that fall within the opening. The input is based on a multiple of slab thickness. Any opening that is within or intersected by this imaginary boundary will be considered in the reduction of the critical perimeter.
Max. reduction per face of support – If the opening projection lines that intersect the column face are more than 90% (or other user-defined input) of the column face dimension that side will be considered as free edge. As an example, in the image below the lengths of the opening projection are shown in 4 different colors: Purple (-R side), Blue (+S side), Yellow (+R side), and Red (-S side). The opening projection rays are taken from the center of the column to the extreme outer corners of the opening. The lengths of intersection between the rays and column sides are compared. If the total sum of projection ray lengths exceeds 90% of the column side dimension, the side is ignored in the punching shear check.

In the case where openings overlap with the projection ray region, the total region is combined as is shown in the image below. In this case, that portion of critical sections at layers moving away from the column face are deducted from the total critical section length.

To learn more about the improvements to the punching shear calculation in ADAPT-Builder, view the video below:

Tags: ADAPT-Builder, ADAPT, New, Punching Shear

November 21, 2022 | ADAPT-Builder, ADAPT, Slab, New, Punching Shear, Popular

Consideration of Drop Caps and Drop Panels for Punching Shear Design

ADAPT-Builder v22 now includes the ability to model a Drop Cap and a Drop Panel at the same support. The Punching Shear check considers both Drop Caps and Drop Panels when creating critical sections for the Two-Way Shear Design. Whether modeling a Drop Cap, a Drop Panel, or a Drop Cap within a Drop Panel, the critical sections will be considered at the support, at the Drop Cap, and at the Drop Panel, when performing a punching shearcheck. To place a Drop Cap and a Drop Panel at the same support, first place the Drop Cap and define the properties. Then, to model the Drop Panel, select the Drop Panel icon, and before placing the Drop Panel, change the Type in the Properties Grid from Drop Cap to Drop Panel. Once the drop panels and drop caps are modeled, you can perform a Two-Way (Punching) Shear Check as well as view Two-Way (Punching) Shear Check Results. For more information about this feature and the use of drop caps and drop panels within slabs in ADAPT-Builder, please visit our Help file by clicking the link below: ADAPT-Builder Help File…

November 21, 2022 | Tendons, ADAPT-Builder, Design, ADAPT, Post-Tensioned

Efficient Design of Tendons with the Support Line Span Optimizer

ADAPT-Builder includes a Support Line Span Optimizer that allows the user to optimize tendons within a support line span based on stress, pre-compression, and balanced loading percentages. The Support Line Span Optimizer will optimize tendons based on the FEM results from the envelope of service combinations analyzed. This tool gives users more detailed information about the tendon optimization occurring within ADAPT-Builder and allows for an efficient design in reference to both time and material. When using the Support Line Span Optimizer, the initial combination is not included in the optimization as the program will add reinforcement per code when tension stresses are exceeded for the initial combination. Once the tendons have been optimized the user has the choice to Update the Service Solution to see what effect the change has on the FEM analysis and design, or continue to optimize tendons in other support line spans whose tendons have not been modified by the optimizer. To learn more about how efficient tendon design can be using ADAPT-Builder and the Support Line Span Optimizer, check out the video below: For additional information, please visit the ADAPT-Builder Online Help file:…

October 21, 2014 | RISAFloor ES, Concrete, New

How are Cantilevered Slabs designed?

Concrete buildings often have large cantilevers. In RISAFloor ES, the Support lines can be drawn to support points but also they can be drawn as cantilevers (shown below). The reinforcement design for the cantilevered section assumes that there will be a positive moment along the distance of the cantilever. This assumption forces the top rebar to be continuous for the entire cantilever span. Deflection Another big consideration for cantilevered slabs is the deflection. The deflection can be checked a few different ways. The easiest way to interpret the deflection is the Contours shown on the slab. This will help you easily visualize the deflection at the edges. Just click on the Contours display icon and select Displacement. If you don’t have this icon showing, click on the following link for instructions on how to add it to your toolbar. Viewing the Deflected shape of the slab is also a quick and easy way to visualize the behavior of the slab. These methods above are showing the overall deflection, however the codes references deflection based on the type of loading and span or distance from support. So it’s important to review the deflection results based on the Design Strips which can…