Incorrect Building Story Shear and Frame Story Shear Results for Dynamic Load Cases
[[Incorrect foundation loads under multi-story braces]]
Incorrect Building Story Shear and Frame Story Shear Results for Dynamic Load Cases
[[Incorrect foundation loads under multi-story braces]]
Applies To | |||
Product: | RAM Steel | ||
First Affected Version: | 15.03.00.00 | ||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 564955 |
Designs and reports for built-up box shapes with slender webs were allowed when they should not have been permitted.
Built-up box shapes with slender webs were not permitted for design in the program. The program should have indicated a slenderness warning message to the user in lieu of the incorrect designs displayed..
The issue will be resolved in the release after v15.03.00. In the meantime, the user should use caution designing slender web built up shapes in the Ram Steel beam module.
Applies To | |||
Product: | RAM Steel | ||
First Affected Version: | |||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 540806 / 562996 |
The compression flange yielding capacity determined in AISC 360-05 or 10, Section F4 for qualifying sections was incorrectly determined.
Where the governing capacity for sections evaluated under Section F4 "Other I-Shaped Members with Compact or Noncompact Webs Bent about their Major Axis" was the Compression Flange Yielding limit, the reported capacity was incorrectly determined as Fy * Zx rather than Rpc * Fy * Sxc per Equation F4-1.
The issue will be resolved in the release after v15.03.00.
Applies To | |||
Product: | RAM Steel | ||
First Affected Version: | |||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 568865 |
Wide flange (W) and Channel (C) shapes subjected to minor axis bending were not correctly designed according to the provisions in AISC 360 Chapter F6 when the governing limit state was Flange Local Buckling.
For Wide flange and Channel shapes with minor axis bending, the reported bending capacities were incorrect when Flange Local Buckling governed the design.
The issue will be resolved in the release after v15.03.00.
Applies To | |||
Product: | RAM Steel | ||
First Affected Version: | |||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 540806 / 562996 |
Round HSS with slender webs exceeding the limit set in Section F8 were unintentionally designed and wrong capacities indicated in the report.
Round HSS with slender webs exceeding the limit in F8 were incorrectly designed and reports showed incorrect results. The program should have indicated a warning message to the user and shown no design.
The issue will be resolved in the release after v15.03.00.
Microstran Excel Addin coming soon (landing page)
Product(s): | RAM Structural System; Ram Frame | ||
Version(s): | V8i | ||
Environment: | N/A | ||
Area: | Analysis | ||
Original Author: | Bentley Technical Support Group |
The diaphragm options in RAM Frame include: Rigid, Flexible/None, Pseudo-Flexible, and Semirigid. Technical notes on the diaphragm types can be found in Section 6.12 of the RAM Frame Manual.
All nodes connected to the diaphragm are assumed to translate and rotate as a rigid membrane. Diaphragm forces for lateral load cases are applied as a nodal load at one point on the diaphragm. These lateral forces are directed into the frames based on relative stiffness: the stiffer the frame or wall, the larger the force directed into the frame. If the load is not applied through the center of rigidity, then there will be a torsional moment on the diaphragm.
Most frame beams have only two nodes and both nodes are connected to the diaphragm by default. The rigid diaphragm in this case will prevent any axial strain in the beam and no beam axial force will occur. Some users will disconnect one node or the other from the diaphragm to force lateral loads through the beam before reaching the braces or columns below, but the selection of which node to disconnect can impact the amount of load, or even the sign of the force, so it is often preferred to check frame beams in rigid diaphragms manually for the axial compression they might realistically take. The frame story shear report gives the total forces transferred form the diaphragm to the frames to help.
Nodes within the diaphragm are assumed to displace independently. Program generated story forces are not calculated. Nodal lateral loads acting on the frames should be calculated outside the program and modeled as nodal loads in Elevation mode of RAM Modeler. Flexible/None diaphragms are assumed to have no stiffness and cannot transfer torsional moment.
Behavior is similar to Flexible/None diaphragms. Unlike Flexible/None diaphragms, a story force is calculated at each level. Based on frame numbers and percentages entered by the user, this story force is divided into nodal loads on each frame. Like Flexible/None diaphragms, Pseudo/Flexible diaphragms do not transfer torsional moment.
The diaphragm is included in the model as meshed shells, using the effective thickness, Elastic Modulus, and Poisson’s Ratio defined with the deck properties in RAM Modeler. For wind load cases, the loads are placed as a series of nodal loads on the windward and leeward edges of the diaphragm. For seismic load cases, the loads are placed as point loads at all finite element nodes. An infinitely stiff semirigid diaphragm will behave like a rigid diaphragm. As the stiffness of the semirigid diaphragm approaches zero, the behavior will approach the behavior of a flexible diaphragm.
ASCE 7-10 Section 12.3 discusses diaphragm flexibility. Section 12.3.1 states that diaphragms should be analyzed as semirigid unless they can be idealized as flexible or rigid. The sections that follow list the requirements for idealizing the diaphragm as flexible or rigid. User Note: The ASCE requirements are modified slightly in IBC (see IBC 2012 Section 202, for example).
ASCE 7-05 Section 12.3.1.1 states that untopped metal decks and wood diaphragms should be considered flexible unless you have moment frames. For moment frames, Section 12.3.1.3 permits a flexible diaphragm if the maximum in-plane deflection of the diaphragm is more than 2x the average story drift.
ASCE 7-10 12.3.1.2 states that concrete slabs and concrete topped metal decks can be considered rigid if the span-to-depth ratio is less than 3 and there are no horizontal irregularities (see ASCE 7-10 Table 12.3-1).
RAM Frame does not automatically determine if the in-plane deflection exceeds 2x the average story drift or if a horizontal irregularity exists. Displacements at any location can be reviewed using RAM Frame Analysis - Process - Results - Drift at a Point (or Drift at Control Points) can be used to look at rigid diaphragm displacements at locations other than the center of mass. The displacements at the center of mass are shown in the RAM Frame Analysis - Reports - Story Displacements.
Since nodal loads for Flexible/None diaphragms need to be calculated outside the program and placed at the appropriate locations by the user, it is generally easier to use Pseudo-Flexible diaphragms for untopped metal decks and wood diaphragms. Pseudo-Flexible diaphragms are also useful for checking that moment frames in dual systems are capable of resisting 25% of the design seismic force (see ASCE7-10 12.2.5.1).
Flexible/None diaphragms are useful for small diaphragms that do not have are connected to few or no frame members. The mass of these diaphragms can be combined to diaphragm at other levels in RAM Frame Analysis – Loads – Masses and the exposure of these diaphragms can be set to None in RAM Frame Analysis – Loads – Exposure, so the seismic and wind forces associated with these diaphragms are collected into the adjacent diaphragms and not ignored in the analysis.
Semirigid diaphragms are useful for models with several or large slab openings, large overhangs, and structures with horizontal irregularities.
Two-way decks are included in the RAM Frame analysis as meshed shell elements for all diaphragm types.
Under gravity load, out-of-plane stiffness of the two-way deck is always included. Since two-way decks are supported by both gravity and lateral members for gravity load cases, it is not appropriate to exclude gravity members as is done when analyzing one-way decks in RAM Frame. There are two options for including gravity members supporting two-way deck in RAM Frame: as vertical springs and as framing members. When vertical springs are used, the program places a spring with a stiffness of AE/L at the support. Note that the spring has axial stiffness only and no flexural stiffness. When gravity members are included, the member is included in the analysis and axial and flexural stiffness of the member is included. Note that fixity of columns is assumed fixed and fixity cannot be assigned to gravity members in RAM Modeler.
In v14.06.02 and earlier, the out-of-plane stiffness of two-way decks defined as rigid diaphragms is always included in the analysis when analyzing lateral load cases. Including the out-of-plane stiffness of the slab can have a significant and often unintended effect on the lateral force resisting system, especially for thick two-way slabs that are meshed with walls.
In v14.07 and later, the out-of-plane stiffness of two-way decks defined as rigid diaphragms is ignored for lateral load cases. This is accomplished by setting both the in-plane and out-of-plane stiffness of the shell to a very small number. Stiffness of the two-way deck can be considered by defining the diaphragm as semirigid.
Out-of-plane stiffness of two-way decks is ignored for lateral load cases when the diaphragm is Flexible/None and Pseudo-Flexible in all versions.
Any of the 4 diaphragm types can be sloped by raising and lowering the columns and walls of the model. Below is a summary of the common side effects that might happen as a result.
A rigid diaphragm constrains the plan (X, Y) coordinates of the frame nodes, but it does not limit relative vertical (Z direction) displacement. For flat slabs, this means that beams under gravity load can bend without the diaphragm taking any of the force. In sloped, rigid diaphragms, however the rigid diaphragm might absorb some axial thrust and limit the forces in the beams. We do not recommend rigid diaphragms when the sloped level includes trusses, bent frames, etc.
It's also worth mentioning that the story height used in calculating wind loads or seismic loads is based on the original story datum. Furthermore, the applied load elevation is also at this datum which determines the net overturning moments on the structure. For this reason, it is generally recommended to model the story heights near the mean height of sloped levels.
In order for a semirigid diaphragm to properly mesh, the deck polygons of any sloped level need to fall in a single plane. If the column and wall elevations lead to a warped surface, then the mesh will not be properly connected to the frame members. See RAM Frame Meshing and Segmentation for details.
If wind or seismic loads are applied to a sloped, semi rigid diaphragm, then some component of those loads will be out-of-plane relative to the slab elements and will therefore cause out of plane bending. If there is not enough stiffness in the elements or the supporting lateral framing, then out of plane deflections will be large and instabilities are likely to occur, or there will be problems solving the eigensolution or using P-Delta.
Since the diaphragm here has no stiffness, the only significance of sloped framing is that it might cause a thrust that will topple frames over if there are no braces or column fixity to prevent it.
Program generated loads will still be based on the original story height as noted above.
When the diaphragm is Flexible or Pseudo Flexible then the various lateral frames and walls move independently and there is no accurate story drift to report. It is best to review nodal displacements to evaluate code compliance for drift in these cases.
RAM Frame - Pseudo Flexible Diaphragms
RAM Frame - Semirigid Diaphragms
RAM Frame - Building and Frame Story Shear
Product(s): | RAM Steel | ||
Version(s): | 15.01.00.00 | ||
Environment: | N\A | ||
Area: | Design | ||
Subarea: | N\A | ||
Defect Number: | 437586 |
AS 4100-98: The controlling interaction reported in the View Update dialog box for columns under compression and weak axis bending was not consistent with the governing interaction shown in the detailed column report.
While columns subjected to axial and weak axis bending were correctly designed and the governing interaction shown in the column design report was also correct, the controlling interaction displayed in the View Update dialog was incorrect. Also the reference for the controlling interaction shown in the Summary Report was incorrect and also ontrolling clause in the summary report is incorrect (shows 8.4.5.1 instead of 8.4.2.2).
AS4100-98 Steel Column design with compression and weak-axis shear.
Problem corrected in version 15.04.00.00. In earlier versions use the detailed design report.
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Original Author: | Seth Guthrie |
Product(s): | RAM Steel | ||
First Affected Version: | |||
Found in Version: | 15.01.00.00 | ||
Fixed in Version | 15.04.00.00 | ||
Environment: | N/A | ||
Area: | Design | ||
Subarea: | N/A | ||
Defect Number: | 434357 |
When checking the member design capacity, the design bending moments were not necessarily the maximum moments along the entirety of the member.
Effect: When checking the member capacity, Section 8.2 required that design moments in the primary axes were the maximum along the entirety of the member. Where the maximum moments were not at the same location, the design used the moments at one of the maximum locations in the design rather than combining the max moments at the different locations together with the axial load. The Section Capacity check was correctly performed.
AS4100-98 Steel Frame design with multi-story column.
Problem corrected in version 15.04.00.00.
[[AS 4100-98 Uniaxial Weak Axis Tabulated Column Results]]
Product(s): | RAM Concrete Column | ||
First Affected Version: | |||
Found in Version: | 15.01.00.00 | ||
Fixed in Version | 15.04.00.00 | ||
Environment: | N/A | ||
Area: | Design | ||
Subarea: | N/A | ||
Defect Number: | 389767 |
As per the requirements of 21.3.3.2(a), the shear demand for an IMF column depends on the value of Mn for the column.
The calculated value of Mn (reported in the IMF section of the design report) was slightly underestimated which could have lead to an unconservative value of Vu.
This affected columns of IMF frames design to any ACI code.
ACI 318 Concrete Moment frame structure with Intermediate Moment Frames (IMF).
Problem corrected in version 15.04.00.00.
[[ACI 318 Column Shear Capacity]]
Product(s): | RAM Concrete Column | ||
First Affected Version: | |||
Found in Version: | 14.07.01.01 | ||
Fixed in Version | 15.04.00.00 | ||
Environment: | N/A | ||
Area: | Design | ||
Subarea: | N/A | ||
Defect Number: | 205403 |
The calculation procedure to calculate the reinforcement shear capacity (Vs) considered only the clear bar cover and the column width or depth, now it is considering also the reinforcement diameters like the rest of the shear reinforcement calculation. The incorrect d value lead to a slight variation in the program calulted shear capacity and a hand calculation.
ACI 318 Concrete column with Vu large enough to require shear reinforcement.
Problem corrected in version 15.04.00.00.
[[ACI 318 Column Shear Capacity]]
Product(s): | RAM Concrete Column | ||
First Affected Version: | |||
Found in Version: | 15.03.00.00 | ||
Fixed in Version | 15.04.00.00 | ||
Environment: | N/A | ||
Area: | Report | ||
Subarea: | N/A | ||
Defect Number: | 489648 |
The Controlling Load Combination for Transverse Reinforcement reported by Ram Concrete Column used to be according to the largest Vu and not according to the largest Ld/Cap ratio. The Vu shown at major and minor axis used the be the greatest in both cases and not the Vu according to the appropriate controlling load combination.
ACI 318 Concrete column.
Problem corrected in version 15.04.00.00.
[[ACI 318 Column Shear Capacity]]
Applies To | |||
Product: | RAM Foundation | ||
First Affected Version: | 15.03.00.00 | ||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 558738 |
Forces for dynamic load cases are 0 in RAM Foundation for foundations that support a brace member and are lowered. The dynamic load case forces are not used in the foundation designs.
The issue will be resolved in the release after v15.03.00. In the meantime, either revert to the prior version 15.02.00.00 or modify the braces so that they intersect a few inches above the base. This can be accomplished by re-modeling the braces using the "knee brace" standard configuration or by adding an extra short story at the base with only columns (and foundations) modeled.
Applies To | |||
Product: | RAM Foundation | ||
First Affected Version: | 15.03.00.00 | ||
Found in Version: | 15.03.00.00 | ||
Fixed in Version: | 15.04.00.00 | ||
Area: | Design | ||
Issue #: | 541339 |
When a foundation supports a braced frame and the brace is one that spans across intermediate stories (modeled using Layout - Brace - Add Special) then the resultant reaction from the brace is absent in the foundation loads giving an unconservative design.
The program is not seeing the brace when determining the foundation loads.
The issue will be resolved in the release after v15.03.00. In the meantime, either revert to the prior version 15.02.00.00, or modify the braces so that they intersect a few inches above the base. This can be accomplished by re-modeling the braces using the "knee brace" standard configuration or by adding an extra short story at the base with only columns (and foundations) modeled.
Applies To | |||
Product: | Ram Steel Column | ||
First Affected Version: | 15.00.00.00 | ||
Found in Version: | 15.00.00.00 | ||
Fixed in Version: | 15.02.00.00 | ||
Area: | Design | ||
Issue #: | 352693 |
Using View/Update on aingle story steel columns supported by Concrete or Other material columns causes the error message "Fy must be greater than zero".
While the designs for single story steel columns supported by Concrete or Other material columns were correctly designed, an investigation of the steel columns through the View Update process resulted in an erroneous error message: Fy must be greater than zero. Reports for the steel columns correctly indicated a non-zero Fy value.
Problem solved in version 15.02.00.00. Ignore the warning on older versions.
Applies To | |||
Product: | Ram Structural System; ISM | ||
First Affected Version: | 15.00.00.00 | ||
Found in Version: | 15.00.00.00 | ||
Fixed in Version: | 15.02.00.00 | ||
Area: | Import/Export | ||
Issue #: | 336010 |
The reaction from the "Left" end in Ram Steel is incorrectly being applied to the "End" reaction of the member in ISM (Structural Synchronizer) and the "Right" reaction incorrectly applied to the "Start" end in ISM. These should be reversed.
Furthermore, the magnitude of the end reaction exported is slightly larger than what is shown in Ram Steel due to the duplicate application of the beam self-weight reaction.
The problem does not affect Ram Steel or Ram Connection, only the exported reactions sent to ISM. When those reactions are used in detailing applications like AECOsim Building Designer or Revit for general assembly drawings, the automated annotation of beam reactions are reversed.
Fixed in version 15.02.00.00.
Applies To | |||
Product: | Ram Manager | ||
First Affected Version: | 15.00.00.00 | ||
Found in Version: | 15.01.00.00 | ||
Fixed in Version: | 15.02.00.00 | ||
Area: | File | ||
Issue #: | 366561 |
Model notes (file.txt) deleted when files are converted up to version 15.00 format from a prior version. Furthermore, notes are not saved when closing and reoping files.
An unintended side-effect of an enhancement to the model notes file to update the file name and job name.
Problem fixed in version 15.02.00.00. Use a separate notes file in version 15.00.00.00 - 15.01.00.00.
Applies To | |||
Product: | RAM Structural System; Ram Modeler | ||
First Affected Version: | 15.00.00.00 | ||
Found in Version: | 15.00.00.00 | ||
Fixed in Version: | 15.01.00.00 | ||
Environment: | All | ||
Area: | Modeling; Licensing | ||
Subarea: | N/A | ||
Issue #: | 328300 |
Ram Modeler crashes, presenting an MFC application error at various times, particularly when saving.
The problem is limited to users who have actively checked-out a license for Ram Modeler (or other specific Ram Modules).
Update to RAM Structural System 15.01.00.00.
Software Download Instructions
Alternatively, in the License Management Tool, check in any licenses that are checked-out and work normally. The program will function and record usage without a checked out license for all SELECT users, though this work-around is not valid for node-locked users who must check-out licenses in advance of using the software.
Applies To | |||
Product: | RAM Concrete Column | ||
First Affected Version: | 15.02.00.00 | ||
Found in Version: | 15.02.00.00 | ||
Fixed in Version: | 15.03.00.00 | ||
Area: | Design | ||
Issue #: | 475167 |
The program hangs and then crashes producing a MFC Application Error when attempting to design concrete columns using either Process - Design All or Process - View/Update.
In affected models, the columns can be designed once successfully. The problem occurs when attempting to design the columns or view/update after the initial design.
The program is checking that a valid set of bar patterns is assigned and is caught in an infinite loop.
Fixed in version 15.03.00.00 (August 2016)
For users who cannot update the version for some reason, the following file, RamConcreteColumn.dll can be used on machines running version 15.02.00.00 x64 only (32 users should submit a service request to get a 32 bit version). To use the file download it to the hard drive and replace the file in the Ram Structural System program directory, normally located here:
C:\Program Files\Bentley\Engineering\RAM Structural System\Prog
There is no need to register the file, but we do recommend making a backup copy of the original file first.
The following process may also be used as a work-around:
The problem will occur again after the columns are re-designed, however.