RAM Concept V8i SELECTseries 9 is now available on Bentley SELECTservices Online:
http://selectservices.bentley.com
This article discusses the primary enhancement in this release: user defined transverse reinforcement, including enhanced ISM interoperability.
RAM Concept V8i SELECTseries 9, release 5.2, now allows shear reinforcement to be drawn by the user, and program shear reinforcement to be converted to user reinforcement. In all prior releases, shear reinforcement was provided by the program only when it was deemed necessary during the Calc All process. Further, program shear reinforcement could not be converted to user shear reinforcement. Although the drawing of shear reinforcement in RAM Concept has similarities to the drawing of concentrated reinforcement, there are a few key differences that are important in understanding how to utilize the feature effectively. This subject is now discussed in detail.
User defined shear reinforcing (orange color) in the web of a T-beam.
Drawing Shear Reinforcing
The Transverse Rebar feature is available under the Tools main menu as well as within the Reinforcement toolbar.
Transverse Rebar modeling command under the Tools menu.
As with concentrated reinforcing, shear reinforcing is defined by a user-drawn line segment on a plan within the Reinforcement layer.
User-drawn line segment defining user transverse reinforcing, with resulting individual transverse bars.
RAM Concept uses the parameters provided in the transverse reinforcement properties dialog to generate individual transverse bars from the line segment during Calc All. This dialog is accessed by selecting a transverse reinforcement object and then choosing the Selection Properties command, which is accessible within the Edit menu or by a right click of the mouse.
Transverse reinforcement properties dialog.
The placement of transverse reinforcing can be based on one of two available methods: Length Fixed placement and Spacing Fixed placement. Each of these methods is described below.
Length Fixed
The user may specify a fixed length over which the reinforcing is to be placed by using the Length Fixed spacing control. In this scenario the start and end points of the segment specified by the user do not change when a different bar spacing is specified. Instead, the spacing input by the user will be revised by the program once OK is selected in the dialog and will reflect the actual spacing of the bars over the segment length. In all cases, the new spacing will be less than or equal to the spacing input by the user.
Spacing Fixed
The user may specify a fixed spacing, which will be enforced exactly, by using the Spacing Fixed spacing control. In this case, the length of the segment may be altered automatically by the program in the situation where the specified spacing is not an even multiple of specified segment length. In this case, the program will automatically adjust the end point of the segment (the point selected second when the line was modeled) so that the resulting spacing of the individual bars is equal to the spacing specified by the user.
User transverse reinforcement object and resulting individual bars in perspective view.
Relation to Cross Sections
User defined shear reinforcing differs from user defined concentrated reinforcing in that the line segment entity drawn to define shear reinforcing (and its associated properties) does not govern the orientation and transverse extent (horizontal direction parallel to the plane of an individual shear bar) of the individual shear reinforcing objects that are generated. The resulting configuration of the shear reinforcing is a function of the cross sections that intersect the user drawn shear reinforcing line segment. This is done to control the complexity and ambiguity that would arise from allowing unrestricted placement of shear reinforcement in the slab without consideration for spans and design strips. There are two important rules that are applied by the software in converting the line segment to individual transverse bars:
- All individual transverse bars generated from the user drawn segment will lie in a plane parallel to the cross sections that the segment intersects. This is true regardless of the direction of the segment. In other words, the segment determines the location of the first and last shear bar, but not the orientation.
- The lateral extents of the individual transverse bars are governed by the shear core of the cross sections that they intersect.
These concepts are illustrated in the three images below.
Two scenarios of transverse shear reinforcement, both resulting in individual bars that are coplanar to the cross sections that the line segment intersects.
Resulting individual transverse bars when shear core setting for design span is Beam Rectangle.
Resulting individual transverse bars when shear core setting for design span is Slab Rectangle.
While important to visualization and interoperability with ISM, individual transverse bars generated by the software are not utilized in the design calculation process. In calculating the shear and torsion strength at a given cross section, the design engine uses the reinforcing properties assigned to the shear segment that intersects the cross section, with no consideration for the locations of individual bars. Only one transverse shear reinforcing segment may intersect a given cross section. If more than one segment intersects a cross section, an error will be delivered during the design process. When more than two legs are specified for transverse reinforcement, only two legs are utilized for torsion-related calculations. The remaining legs are used for shear calculations only.
Considerations for Interoperability and Detailing
The method of creating user defined transverse reinforcement employed in RAM Concept gives priority to fulfilling structural design code provisions, rather than to placing reinforcing at a detailed, to-be-constructed level of refinement. In most scenarios the individual bars placed by the software provide a sufficiently accurate three-dimensional representation, requiring only nominal revision for use of the data in construction applications. In other situations however, it may not be practical to use RAM Concept as a method of specifying the final configuration. The reinforcing produced by the software reflects what RAM Concept uses as the basis of the structural design calculations. Although the transverse bar configurations are not always reflective of the final detailed bar layout, they provide a starting point for the detailing work to be done downstream of the structural design. As with other types of user reinforcing, user defined transverse reinforcement is compatible with the Integrated Structural Modeling (ISM) framework. Transverse reinforcement can be transferred into and out of RAM Concept via the ISM link.
Questions or comments on this article may be sent to Josh Taylor at Josh.Taylor@bentley.com.