Several significant enhancements and features have been implemented in RAM Structural System V8i SELECTseries 7 Release 14.07. This version is scheduled for release Q1 2015.
Manage License Restrictions
Bentley’s Open Access licensing scheme does not prevent the use of any program modules for which a license has not been purchased. Use of such modules is permitted, but will result in a quarterly usage fee. To prevent the inadvertent use of such modules a Tools – Manage License Restrictions command has been added in the RAM Manager that allows the user to specify which modules are to be accessible and which modules are not. Only those modules that are selected in that dialog can be accessed.
Bentley Communities is a community website with blogs and wikis rich in technical content. This includes technical discussions on a variety of topics as well has answers to questions from clients on specific features of specific programs. This is a much underutilized resource that users and others are invited to peruse. To make this material more accessible, and to make it more immediate and relevant, a new Communities button has been incorporated in several of the commands in the RAM Structural System.
Invoking this button brings up a browser, with content relevant to the particular feature from which the command was invoked. The author, creation date and revision date are listed, to assist in determining the timeliness of the information. A list of articles is created, from which a desired article can be selected for reading. A Search feature is included to enable searches for articles on any keyword entered. This feature will expand to more commands as additional relevant content is created.
Composite Beam Design Improvements
In the selection and investigation of studs for composite beam design the program comprehensively investigates the conditions that affect the placement of the studs, including the effects of the deck rib spacing, orientation and location along the beam and the likely location of the studs relative to points of zero and maximum moments. Several refinements have been made in the calculation of the required studs and in the analysis of composite beams with user-specified stud quantities. This includes, for example, better consideration of the likely number of ribs crossing the beam when the deck is perpendicular (or at an angle), and the likely placement of the studs along the member. As a result of these changes you may see slight differences in some of the beams designs as pertaining to the quantity of studs. A discussion of these changes and their effects is given here. Note that for the vast majority of beams there will be no changes in the number of studs specified by the program, and where there are differences they will almost always be a slight reduction in the number of studs required.
Some design warning messages have been enhanced and additional design warning messages have been implemented, making it clearer as to the reasons for beam failures.
Studs for Concentrated Loads:
In addition to the requirements for the number of studs required to satisfy the capacity at the point of maximum moment the Specifications have requirements for the number of studs required to satisfy the capacity at the points of concentrated loads. When optimizing the studs on beams the program conforms to these requirements to ensure that there are sufficient studs along the various beam segments to satisfy the capacity demands at these locations. However, when checking a user-specified size, including ‘frozen’ sizes, the program did not give any warnings of the user-specified studs did not satisfy these requirements. The design error was apparent in the View/Update command even without the warnings because in that dialog the number of studs required is listed under “Partial”; if the number of studs specified by the user, as listed under “Actual”, is less than the number listed under “Partial”, the user-specified studs are inadequate, and in the absence of any other design error messages the most likely problem was insufficient studs to satisfy the requirements at the points of concentrated loads. To resolve the design deficiency the user should always specify at least as many studs as are listed as required for “Partial”. Checking each beam that has a user-specified size individually in the View/Update is inconvenient, however, so in this version the program explicitly tests the beam capacity at the points of concentrated loads using the user-specified studs and gives design error messages if the capacity at those points is insufficient. Again, it is emphasized that in the optimization of studs and beam sizes the program always checked and designed for the requirements at the points of concentrated loads, but in the analysis of user-specified beams and stud it did not check and give design error messages for the requirements at the points of concentrated loads.
Furthermore, if the demand/capacity ratio at a point of concentrated load is the controlling ratio for the beam, the Beam Design report will list the moment, capacity and location as the Controlling condition. Also, this value will be used in the display of the Controlling Interaction values in the Process – Design Colors command. Previously the demand/capacity displayed in that command did not consider that the demand/capacity ratio a point of concentrated load may be greater.
Note: For the ASD 9th Ed. requirements the stress ratio at the point of concentrated loads is not considered in the Controlling Interaction values, since the Specification requirements for satisfying the stud requirements at those points does not include the calculation of the stresses.
Determining Number of Deck Ribs Crossing Beam:
The program considers the number of deck ribs that cross the beam when the deck is not parallel. This impacts the placement of the studs and the number of studs that can fit on the beam. Note that for a given length of beam the number of ribs that cross that beam varies depending on how the deck is laid out. For example, a 27.5’ beam with deck with 12” rib spacing may support either 27 or 28 ribs, depending on where the first rib occurs along the beam. In some cases the program was not consistent in the value that it used; now it always uses the smaller value. This is reasonable since the beam’s actual length is something less than the center-to-center length used in these calculations, so it is highly unlikely that the larger number of ribs will actually cross the beam.
Note that for determining the available ribs for placing studs for the strength calculations, using the smaller value is conservative (which is what the program does), but for determining the compliance with the maximum stud spacing requirement using the larger number is conservative (which is what the program was doing). The impact of this discrepancy was most notably seen when the user specified a maximum stud spacing that was the same as the rib spacing (for example, 12”) and the final design only required a small beam whose flange width was only wide enough to accommodate a single row of studs. To satisfy the maximum stud spacing the program would specify the number of studs to satisfy the larger number of ribs but then when doing the final verification of the capacity of the studs using the smaller number of ribs the program would give a design warning message that those studs didn’t fit in a single row (there was one more stud than the number of ribs it was then considering). This conflict has now been eliminated by consistently using the same value for the number of ribs crossing the beam for all checks. This change may result in fewer studs on the beam than was erroneously specified previously.
Studs at Point of Maximum Moment:
If a stud is placed at the point of maximum moment it does not contribute to the strength of the composite beam because at the point of maximum moment there is no horizontal shear between the concrete and the steel beam and therefore that stud is not resisting any shear. The program ignores any stud that occurs at the point of maximum moment, and furthermore when optimizing the quantity of studs may add an additional stud if necessary to force a placement of studs such that none of the studs occur at the point of maximum moment (for example, for a beam with the point of maximum moment at midspan, 9 studs uniformly spaced on the beam would place one stud at midspan which would not contribute to the strength of the composite beam, but 10 studs uniformly spaced would result in 5 studs each side of the point of maximum moment, each contributing to the strength of the composite beam). Furthermore, depending on the way the deck is laid out any stud near the point of maximum moment may occur on one side or the other of the point of maximum moment and therefore cannot be counted on to contribute to the strength on a given side; the program ignores studs too close to the point of maximum moment. When the point of maximum moment occurred at midspan this all worked well, but when the point of maximum moment was offset from midspan the program may have done a poor job of recognizing whether it was appropriate or not to ignore a stud near that point or to add an additional stud to move the studs away from that point (the distance considered too close to the point of maximum moment was too conservative). As a result the program may have added one more stud than was necessary, or may have rejected a user-specified quantity of studs that may have been reasonable but determined to include a stud unacceptably near the point of maximum moment by the program. This change may result in fewer studs on the beam than was erroneously specified previously.
User-Specified Minimum Percent Composite:
The program allows the user to specify a minimum percent composite that is more stringent than the applicable Code. When selecting the studs the program increases the number of studs if necessary to meet this criteria. However, there was one condition where the program failed to enforce the user-specified minimum and did not warn the user: if the distance between the beginning of the segment and the point of maximum moment was short such that it was possible to place enough studs to satisfy the Code-required minimum percent composite but not possible to place enough studs to satisfy the more stringent User-specified minimum percent composite, the program would select the studs that satisfied the Code requirement but not those that satisfied the user-specified minimum, and gave no warning of the condition. Note that this meant the beam satisfied the Code, so it was not a dangerous design, it merely failed to meet the more stringent user-specified requirement. Now for this condition the program will still revert to the quantity of studs that satisfy the Code-required minimum percent composite but will give a warning indicating that the user-specified minimum percent composite was not satisfied. The user then has the option of either ignoring the warning or modifying the design as desired.
Also, previously when analyzing a beam with a user-specified quantity of studs the program did not check or warn when those user-specified studs did not satisfy the user-specified minimum percent composite; it was assumed that since the user had specified the number of studs that the user didn’t intend to comply with that user-specified minimum percent. However, a check has now been implemented, and if the user-specified studs do not satisfy the user-specified minimum percent composite a design warning is given. The user can then decide whether to ignore the warning or to add more studs.
Tolerance on Minimum Percent Composite:
To avoid potential problems caused by round-off differences between the functions of the program that calculate the number of studs required to meet minimum percent composite and those that calculate the actual percent composite for a given number of studs, a tolerance is applied to the test to determine if a design meets the minimum percent composite requirements. That tolerance was 0.1%, which meant, for example, that a beam designed using AISC 360 was considered to meet the 25% minimum requirement even if it was actually only 24.9% composite. The algorithms have been improved and the 0.1% tolerance is considered excessive so it has been reduced to 0.01% (which means, for example, that a beam now needs to be at least 24.99% composite to be considered as meeting the 25% minimum requirement). It is highly unlikely now that a beam for which the percent composite falls within that tolerance will ever be encountered, and almost certainly not by an optimized design.
Maximum Stud Spacing:
When determining the number of studs the program considers both the Code and user-specified requirements for maximum stud spacing. When the deck ribs are at an angle to the beam the program considers how the studs need to be spaced, accounting for the spacing of the ribs in relation to the maximum stud spacing. For example, if the maximum stud spacing is 30” and the rib spacing is 12” the studs need to be spaced at 24” maximum (every other rib) in order to satisfy the 30” required maximum. The program handles this condition correctly. However, when the deck is parallel to the girder or when the slab is a flat slab there was a potential error in the number of studs specified by the program when the quantity of studs was controlled by maximum spacing. The spacing within any girder segment correctly satisfied the maximum spacing requirements but potentially the maximum spacing requirement was exceeded between the last stud in one segment and the first stud in the adjacent segment. As a result of this correction segments controlled by maximum stud spacing may have one additional stud more than was given in the previous design. For existing models with frozen or user-specified beam sizes and stud quantities a design warning may now be given indicating that there are insufficient studs to satisfy the maximum stud spacing requirements. Note that despite the message this doesn’t necessarily mean that there is an error, it depends on how the studs are laid out in the adjacent bay; if the two adjacent bays were not both controlled by maximum stud spacing it is possible that the studs required in one bay will result in a stud placed sufficiently close to the end of the segment such that the distance from that stud to the first stud in the next bay actually satisfies the requirement. So for those frozen designs the message may or may not be correct, depending on the stud distribution within the segments. For optimized designs the program will now consistently call for studs such that the potential problem no longer exists. This change may result in one more stud within segments of the girder than was specified previously (but only if maximum spacing, not strength, controlled the number of studs).
Beams With Cantilevers:
When a beam has a cantilever, any studs placed within the length of the beam where the moment is negative (the concrete is in tension) cannot be considered to contribute to the composite capacity of the beam. When calculating the beam capacity the program correctly ignores those studs, but when trying to select the optimum beams size and stud quantity the program may have failed to try enough studs before failing that size and going to the next larger trial size. As a result, the program may have selected as the optimum size a beam that was larger than necessary.
The program allows the user to specify on a beam-by-beam basis that the rib spacing is to be ignored when determining the number and placement of the studs. This is useful in the case of a beam that is highly skewed with respect to the deck, resulting in a very limited number of ribs actually crossing the beam. When the user specifies this it is then assumed that the beam is going to be detailed such that the deck is split and separated along the beam length or that the ribs are going to be flattened as necessary along the beam length so that the studs can be placed anywhere along the beam regardless of the rib locations. Internally, some of the calculations of capacity and spacing where erroneously ignoring this assignment, so in rare cases the program may have required more studs than were actually necessary for the beams for which the Ignore Ribs command had been assigned.
The program allows the user to specify that the concrete slab supported by the beams is a formed flat slab, rather than concrete on metal deck. This affects stud capacity and placement, as the studs can be placed anywhere along the beam without regard to any rib locations. Internally, some of the calculations of capacity and spacing where erroneously ignoring this condition, so in rare cases the program may have required more studs than were actually necessary for the beams supporting formed flat slabs.
Canada Concrete CAN/CSA A23.3-04 (R2010)
The concrete design requirements of CAN/CSA A23.3-04 (R2010) have been implemented for beam and column design in the RAM Concrete module. Comprehensive design includes bar selection, not just a listing of required steel area. Extensive criteria and design options allow the design to be highly customized, and reinforcement can be optimized or user-assigned and analyzed. Designs can be copied from one member to another.
Reports include individual member designs, design summaries, and takeoffs. Floor plans, base plans with column marks, column schedules, and beam schedules and elevations can be created for CAD. The model, including reinforcement bars, can be exported to BIM, such as Bentley’s AECOsim Building Designer and Autodesk Revit
NBC of Canada 2010
The pertinent requirements of NBC of Canada 2010 have been implemented. These include:
NBC of Canada Importance Category – Important Changes
Previously when NBC of Canada was selected, the Importance Category needed to be specified. This was used to decrease the Live, Roof and Snow loads if the Importance was Low, and to increase the Snow load if the Importance was High or Post-disaster. This was done correctly for steel columns in RAM Steel Column, but the Snow loads were not increased in RAM Steel Beam when required. Furthermore, since the definition of the Snow load explicitly includes the Importance Category factor it created the potential that the user would specify the Snow loads in the Modeler already modified by the factor, and that the program would then again apply that factor. To eliminate this possible confusion and the incorrect application of the factors the option to specify the Importance Category has been removed. It is expected that the user will apply the Importance Category factors as appropriate to the Live, Roof and Snow load values entered in the Modeler. The program will not apply any factors based on the Importance Category to these loads.
In RAM Frame Steel Design module the load combination templates for S16-01 and S16-09 included options to specify Importance Category factors for Live, Roof, Snow, Wind and Seismic. Since the equations for the calculation of Snow, Wind and Seismic loads explicitly include the Importance Category factors (and the automatic load generators for Wind and Seismic include them), the factors were possibly getting applied to those loads twice – once when the load was defined/generated and again in the Load Combinations. The options for specifying the Importance Category factors have been removed from the S16-01 and S16-09 load combination templates since they are redundant and unnecessary. The error, if it occurred, was conservative unless the Importance Category was Low.
Note that if the Importance Category was Normal, no errors occurred.
FloorVibe and FloorVibeUK
For vibration analysis of steel floor framing systems the RAM Steel Beam module has the ability to launch special versions of FloorVibe, based on AISC/CISC Design Guide 11, and FloorVibeUK, based on SCI Publication P354. These programs were developed by renowned vibration expert Thomas Murray and are a product of Structural Engineers, Inc. They have previously been distributed with the RAM Structural System on a limited basis, and had to be installed separately. These programs are now part of the RAM Structural System installation, making them both available to all RAM Structural System clients. These special versions can only be launched from the RAM Structural System. For stand-alone versions go to the Structural Engineer, Inc., website at www.floorvibe.com for more information.
CoreBrace Buckling Restrained Braces
In RAM Frame, the implementation of CoreBrace Buckling Restrained Braces (BRB) has been significantly enhanced. They are now recognized as a distinct shape and can be assigned, analyzed and designed. Criteria for CoreBrace BRB’s can be set which is used globally for those braces, or can be assigned to individual braces. The Stiffness Modifier is automatically calculated, but can be over-ridden by the user if desired. Beta and Omega factors are automatically calculated, but can be over-ridden by the user if desired. The braces are checked per the requirements of the AISC 360 Specifications and the AISC 341 Seismic Provisions.
Beta and Omega factors are calculated both at 2x Design Story Drift and at 2% Design Story Drift.
Welded, Bolted, Pinned and Splice Plate connect types – including the corresponding specified Minimum connection clearances – are considered in the calculation of the Stiffness Modifiers. Additionally, if necessary for a particular project, tables with Custom connections can be obtained from CoreBrace. The assigned connection types are displayed with a unique icon on each buckling restrained brace.
Columns are designed based on the adjusted brace strength.
Star Seismic Buckling Restrained Braces
The Star Seismic Buckling Restrained Braces feature has been enhanced:
Brace size labels now include text indicating the brace type, "(P)" for Powercat and "(W)" for Wildcat.
For the Seismic Provisions check per AISC 341-10 the program is now calculating the b and w factors both at 2 times the Design Story Drift and at 2% Story Drift.
The program has been modified so that the user inputs the value for Cd/Ie rather than simply Cd. Previously the program pulled the Ie value from the load case generator information, but that information wasn’t always available, so the program was simplified to require the user to specify Cd/Ie directly.
In the selection of Tables in RAM Manager there is a new tab for BRB which allows the user to select the table to be used, rather than always using the ramstarseismic table. This is useful in the event that a project-specific table is supplied by Star Seismic.
Buckling Restrained Braced Frames and Special Concentric Braced Frames
For AISC 341 an option has been added allowing the user to specify whether the Required Strength of columns is based on the Adjusted Brace Strength (as per the Specification), based on the Amplified Seismic Forces using W0 (generally a more conservative approach), or based on the larger of those two values.
Previously when testing for the Width-To-Thickness ratios for webs in Table D1.1 the program conservatively assumed Ca = 1.0. If the size conformed the program reported that the size passed the test, but if it didn’t conform it indicated that the beam Failed. Because of the conservative assumption that Ca = 1.0, this wasn’t necessarily true. Now the program performs the test with that conservative assumption but rather than Failing sizes that don’t conform it indicates Additional Check Required. The additional check that must be performed is to determine the actual Pu in the beam from an analysis that considers the brace overstrength factors (which is not performed by the program), determine the limiting width-to-thickness ratios given in Table D1.1, and compare with the beam’s h/tw ratio.
Braces in Gravity Load Cases Analysis
An option has been added to the RAM Frame Analysis criteria allowing the user to specify that braces in braced frames be excluded from the frame model in the analysis of the Gravity load cases. This ensures that no gravity loads are distributed to the braces by the analysis, and that all gravity loads are carried by the columns.
Analysis Results Export
In RAM Frame a command has been added allowing the user to export analysis results to a text file, in .csv format. Available files include:
nodal reactions for each load case for each foundation node.
nodal displacements for each load case for each foundation node.
member forces for each load case for every member.
In the future this feature will be expanded to include more results and data.
ASCE 7-10 / IBC 2012 ASD Combinations
The Errata to ASCE 7-10, posted on January 11, 2011, modified Equation #6 under Basic Combinations for Allowable Stress Design in Section 126.96.36.199. With the revision it is not necessary to include Roof Loads in combinations with Seismic Loads. The combination template RamSteelIBC2012_ASD.cmb has been modified to conform to the Errata revision. This template is used in the RAM Frame – Steel Standard Provisions module.
ASCE 7-10 Seismic Load Report
The Loads and Applied Forces report has been enhanced for the ASCE 7-10 Seismic load cases to more clearly list the calculated values for Cs, including the values from the minimum and maximum equations, and the value used in the determination of the base shear and story forces.
BS 4449-05 and BS 8666-05 Reinforcement Designation
In the RAMUKType2M.ren table of reinforcement, the reinforcement designation has been changed from T to H in accordance with BS 4449-05 and BS 8666-05.
EN 1991-1-1:2002 Storage Live Load Reduction
The March 2009 Corrigendum eliminated the reduction of Storage Live Loads for Eurocode EN 1991-1-1:2002 Clause 188.8.131.52(10) and (11). When Eurocode is selected as the design code, Storage Live Loads are no longer reduced.
Steel Beam View/Update
The Steel Beam View/Update dialog has been enhanced to show the Demand/Capacity ratios, for both Strength and Deflection.
Steel Column Unbraced Length
Previously, if a steel column was supported by a concrete column at a level where the concrete column was not laterally restrained by beams, the program would conservatively combine the steel column height and the concrete column height between braced levels when determining the unbraced length to use for the design of the steel column. The program now assumes that the concrete column below has been designed sufficiently stiff to act as a cantilevering column, and hence the unbraced length of the steel column only includes the length of the steel column, from where it sits on the concrete column up to the level where it is laterally braced (by beams and/or deck).
Gravity Column Design Report
The Column Number has been added to the Gravity Column Design report. Previously only the column grids were listed.
Hanger Error Message
If a hanger is modeled such that it has no supporting member, the program gives an error message and exits the Framing Tables phase of the analysis (rather than merely crashing the program).
Verco N3 Formlok Deck
The Verco N3 Formlok deck profile has been added to the ramdecks.dck file, for use with composite beam design in the United States.