RAM | STAAD | ADINA - RAM Concrete Analysis Tutorial

RAM Concrete is completely integrated into the RAM Structural System. It uses the same model and database as RAM Frame and RAM Steel. While most of the information needed for concrete gravity analysis and design is taken from the database, some data does need to be entered in the Concrete program itself. This is largely information specific to reinforced concrete design such as concrete design code settings, reinforcing preferences, slenderness parameters, and frame type.

You must have a license to RAM Concrete to perform this part of the tutorial. If no license is available, skip to the next section, RAM Foundation. This tutorial demonstrates the US design codes, although a range of international standards are implemented in the RAM Concrete. SI units will not be presented in this section, but an SI units model can still be used.

To invoke RAM Concrete from the RAM Manager:

Select Design – RAM Concrete or select the 5th square button depicting a concrete beam and column.

In order for the program to design the concrete members correctly, a separate gravity analysis needs to be performed. The lateral force results from RAM Frame are added to these gravity results automatically. For this reason you should always perform a RAM Frame analysis prior to running RAM Concrete.

Concrete Program Organization

The RAM Concrete program is comprised of four modes: the Concrete Gravity Analysis module, the Concrete Beam Design module, the Concrete Column Design module, and the Concrete Shear Wall Design module. When you enter RAM Concrete you will always be placed in the Concrete Gravity Analysis Module. These modules function as follows:

Concrete Gravity Analysis Module

When you select Design – RAM Concrete you will be placed in the Concrete Gravity Analysis Mode. The mode drop-down on the upper left toolbar will indicate you are in this mode.

In this mode a finite element analysis of each story is performed. This analysis determines the gravity forces for both concrete column and beam design. In this module you have some control over the finite element analysis which will be discussed. You also assign beam lines which affects how the beams are detailed.

It’s important to note that the concrete analysis requires all members, even steel members, to have an assigned size. If a model includes optimized members (those to which a size has not been assigned by the user), then the RAM Steel Beam and Column design modules must be run prior to analyzing the model in RAM Concrete.

Concrete Beam Design Module

In this module the design of all concrete beams is performed. The gravity analysis forces are automatically combined with the lateral forces (from RAM Frame) to obtain design beam forces. The program automatically designs reinforcement considering user preferences and code requirements. An interactive view/update command provides a means of modifying the program design. Concrete Gravity Analysis must be run prior to performing the design in Concrete Beam. RAM Frame must be run prior to performing the design in Concrete Beam in order for lateral forces to be considered in the design. Otherwise the program will consider only the gravity forces calculated in Concrete Gravity Analysis.

Concrete Column Design Module

In this module the design of all concrete columns is performed. The gravity analysis forces are automatically combined with the lateral forces (from RAM Frame) to obtain design column forces. Column forces from the external program RAM Concept can also be utilized. A comprehensive moment interaction surface is calculated for the design of each column. Multiple reinforcement patterns can be considered for each column line, and the program automatically selects the optimal pattern and reinforcement size. An interactive view/update dialog provides a means of altering the programs designs. Concrete Gravity Analysis must be run prior to performing the design in Concrete Beam. RAM Frame must be run prior to performing the design in Concrete Beam in order for lateral forces to be considered in the design. Otherwise the program will consider only the gravity forces calculated in Concrete Gravity Analysis.

Concrete Shear Wall Design Module

In this module the design of concrete shear walls is performed. Concrete Shear Wall Design performs the design of walls assigned as lateral elements and utilizes only the forces from RAM Frame in designing the walls. As such, Concrete Gravity Analysis does not need to be run prior to designing shear walls. Concrete Shear Wall Design module discretizes walls into wall panels and section cuts. At each section cut the axial-flexural and shear design is performed and a reinforcing pattern for each wall panel is selected. The user may override the program selected panel reinforcing at any time and even place unlimited zones of different reinforcing patterns along the length of a wall panel.

Assign Beam Line Numbers

In order to establish which beams will be skip loaded, and which gravity concrete beams should be considered continuous for analysis, you must first assign beam line numbers to the beams. A beam line number defines which beams will be designed as a single continuous beam in the beam program. Beams in a contiguous line are typically assigned the same beam line number, but you can manually assign almost any continuous line of beams to the same beam line as described below.

Select Assign – Beam Line – Automatic from the menu bar to display the dialog box.

Our model should not have any skewed beams but the beams on either side of a girder might be slightly off center.

Set the Beam offset to accept as continuous to 2.
In the Gravity Beam Fixity box, check the box to Automatically Assign Fixity and Fix all beams.
Click [OK].
Select View – Plan and select the Second story.

The second story (the story with concrete beams) will have the following beam lines automatically generated. Notice that the only concrete beams are assigned beam line numbers.

Generated Concrete Beam Lines

We will now the end segments of beam line eleven and assign it to be a separate line manually. Zoom into the area if you cannot easily see the beam line numbers using View – Zoom Fence.

Select Assign – Beam Line – Manual from the menu bar.

If you are not already in plan mode you will be asked to select a floor plan,

Select the 3rd floor and click [OK].

The Assign Beam Line manual dialog will open. It may be helpful to turn off the decks display at this point by selecting View-Members, Then selecting Decks/Slabs (Last icon).

Select the option to Remove from Beam Line.
Click [Single].
Click on the beam between Grids A and B and E and F on Grid 4.

Hint: Beams in a single beam line must be must be continuous. If you select two beams, that are not continuous, to be in the same beam line you will be issued an error message.

Right click to return to the previous window
Set the Assign Mode to Add to New Beam Line.
Click [Single] and pick one of the beams again.
Repeat for the other beam

This span will now be detailed separately from the beams in the moment frame. To clear up the display:

Select View – Reset Model.

Analysis Criteria

Before the analysis is performed make sure the analysis criteria are appropriate.

Select Criteria – Analysis. The analysis criteria dialog will appear.

Set the various analysis criteria as follows:

Minimum number of stations per beam: 10.
Maximum spacing between stations: 12in (250mm).
Rigid End Zones: Include Effects.
Reduction %: 50
Check: Skip-Load the Live Load on Beam Line Beams
Check: Skip-Load the Live Load on Non-Beam Line Beams
Check: Consider Live Load Reduction
Concrete Beam Torsional Constant Reduction: Use Torsional Cracked Factor from Section Property

This prevents girders with unbalanced loads from taking too much torsion. It accounts for the additional cracking in the concrete.

Check: Consider Column Slenderness
No checks in the Analysis Constraints section.
Accept the defaults for Mesh Controls.
Check: Save Results for Display Purposes (slower analysis).
Use the In-Core Sparse Solver (Speeds up analysis slightly for complex models).
Click [OK].

NOTE: Many of the settings in this dialog can have a significant effect on the speed of the analysis and design. In particular the greater the number of stations per beam and the larger the number of load cases to be analyzed the longer the analysis and design. If you are only interested in performing a quick preliminary design, increase the maximum space between stations and switch off skip loading. You can also turn off the option to Save results for display purposes – this won’t prevent you from designing the members.

Other Criteria

The other criteria should also be set before running the analysis. Start with the design code.

Select Criteria – Code.
Select ACI 318-08 (BS 8110-97) for the code.
Click [OK].

The criteria for column Design Forces allows you to choose whether to use the forces from the RAM Concrete analysis or to use the column design forces from one or more RAM Concept models instead.

Select Criteria – Column Forces.

Click [OK].

The sidesway criteria establishes whether the column should be considered Braced or Unbraced.

Select Criteria – Sidesway.
Select the option for Partially Braced.
Check the second box for Global Y axis.

This means that our moment frames will be unbraced in the X axis and braced in the Y where there are shear walls.

Click [OK].
Select Criteria – K Factor.
Select to use the Nomograph Values in both axes.
Click [OK].

Gravity Analysis

Now that the various criteria are set it time to perform the analysis. To perform the analysis:

Select Process – Analyze.

The analysis progress window will appear:

This window shows the progress of the analysis and the number of load cases that were automatically generated for each story. The two progress bars at the top of the window show the progress of the analysis.

It is required that all members have an assigned size to complete the concrete analysis. In order to assure that all the steel members have an assigned size, be sure to run the steel beam and columns modules first.

In the RAM Concrete analysis, a finite element model is generated for each story and skip load patterns are automatically generated for the live loads. For each story a full finite element analysis is performed and the reactions carried down to be applied to the analysis of the story below. For this reason mainly, the results obtained from RAM Concrete may differ from the results for the gravity loads in RAM Frame or in RAM Steel for that matter.

When the analysis is complete click [Close] to close the window.

On-Screen Results

Once the analysis is complete you can display several different analysis results on the screen. Depending on the current view and the model size the screen could be extremely cluttered when results are displayed. It may be desirable to view the results in elevation or plan view and/or with the extruded shape setting removed (i.e. in stick drawing mode).

To ready the model view for best display of results on the entire structure:

Select View – 3D.
Select View – Zoom – Full.
Select View – Resolution – Low.

Results – Finite Element Model information

To view the finite element model for a particular story:

Select Process – Results – FE Model.

The FE Model Information dialog will open. To view the finite element model that was created and analyzed for the second story:

Select 3rd from the Story drop down box.
Keep all the display options selected.
Click [Apply].

The display will change to show only those members that were considered in the analysis of the 3rd floor. The member fixity conditions (released, fixed) are displayed, as are the finite elements, node numbers and restraint conditions. Note that nodes are restrained, at the levels above and below the current story, where they are braced according to the column bracing criteria.

You can zoom, rotate and print the screen display while the FE Model Info window is displayed. Closing the window will reset the model and remove all the finite element settings.

If there is an error during the analysis it is possible that a node number (or location) will be provided in the error message. The analysis will terminate, but the Finite Element Model of the story under analysis should be available so that you can identify the location (node) of the problem and perform corrective action.

Results – Vertical Reactions

To view the vertical reactions for each load case on a particular story:

Select Process – Results – Vertical Reactions.

The Vertical Reactions dialog will open. To view the vertical reactions from each load case in the analysis of the second story:

Select 2nd from the Story drop down box.
Select DL1 from the Load Case drop down box.
Click [Apply].

The display will change to show only the members used in the selected stories analysis, and the vertical reactions from the selected load case. The reactions displayed represent the reactions for the current story and load case analysis. However, one or more of the load cases will include the reactions from all the upper stories analyses. For dead load the loads from the previous stories analysis will have been transferred into the analysis for the current story. The reactions for the DL1 case therefore include the loads that are transferred from the upper stories.

Notice that the Live Loads have been separated into several load cases to account for load patterns. The total live load reaction can be obtained more easily through a report.

Results – Member Forces

To view the beam and column forces for each load case on a particular story:

Select Process – Results – Member Forces.

The Member Forces dialog will open. To view the member forces from each load case in the analysis of the second story:

Select 3rd from the Story drop down box.
Select DL1 from the Load Case drop down box.
Check Beam Force Major Moments (1/4 pts).
Uncheck Column Force and Wall Force.
Click [Apply].
Select View – Plan or zoom in if the text is difficult to read.

Only significant member forces are shown for each load case selected. If beams are skip-loaded then each type (reducible, unreducible, roof or storage) of live load on a single span will be considered its own load case. The loads on one member will affect other members due to the continuity, but the forces are not displayed when the values are insignificant.

Results – Displacements

To view the displacements of members and decks on a particular story:

Select Process – Results – Displacements.

The Displacements dialog will open with some options and controls.
Select 2nd in the Story drop down
Select DL1 from the Load Type drop down.
Leave all the checkboxes checked
Click [Apply].

The graphics screen will now display the members and meshed surface of the two-way flat slab of the 2nd story (Decks/Slabs must be turned on in the view menu to display). The Displacements dialog will remain on the screen. By selecting and dragging the small triangles (sliders) at each end of the legend the engineer can set the limit at which all displacements larger than will be colored in the extreme color (red or blue). This way an engineer can easily identify locations where the slab deformation exceeds a specific user defined limit. Also, the transparency of the meshed surface can be controlled by the Transparency slider. Take this opportunity to use the various controls and familiarize yourself with the dialog.

Click [Close] to leave the dialog and return to the normal view.

View Options

In the concrete gravity analysis mode there are several other useful display options under the view menu. Take the time to select the various menu options to view different model data or adjust your view of the model. Two menu options are particularly relevant to the Concrete Gravity Analysis mode, namely the command for viewing Beam Lines and for viewing Gravity Loads.

View Beam Lines

To view the currently assigned Beam Line Numbers:

Select View – Beam Lines.

The View Beam Line window will be displayed.

Select 3rd from the Story drop down box.
Select the beam line numbers whose beams you want to highlight.

If the Show Beam Line Numbers check box is checked, the beam line number will also be displayed on screen for the selected beam line/s.

Click [Apply].

View Gravity Loads

To view all the member line and point loads that were applied by the user and also calculated by the program:

Select View – Gravity Loads.
Select one of the gravity load types that you would like to view.
Click [Apply].

NOTE: Depending on the current view and the selected load to display the screen could be extremely cluttered. It may be desirable to view the gravity loads in elevation view and/or with the extruded shape setting removed (i.e. in low resolution drawing mode).

More complete gravity load information can be obtained in report form. Select the Reports – Load Diagram command to obtain beam gravity loads.

Reports

Reports can be generated from the Concrete Analysis just like the other modes. The printed output is generated using the Reports menu. There are several important and useful reports generated in the Concrete Gravity Analysis Mode, some of which are discussed below.

To view the analytical member properties used in the finite element analysis (this includes the calculation of effective flange width for concrete T beams and consideration of cracked section factors):

Select Reports – Member Analysis Properties.
After a few seconds the Analysis Member Properties report will open. Hit the Page Down Key to see the rest of the report.
Click to exit the report.

For column design the program considers the worst skip loaded condition for live loads about each axis of the column, both top and bottom. To view the gravity column forces that will be used in the column design mode:

Select Reports – Column Design Forces – Single.
Click on one of the concrete columns below the Third floor.

For beam design, the program also considers an envelope of results. To view the gravity beam envelope forces that will be considered in the beam design mode:

Select Reports – Beam Line Force Envelope – Single.
Click on one of the concrete columns below the second floor

NOTE: For lateral beams and columns the gravity forces shown in these reports will normally be combined in the Design Modes with lateral forces from the analysis performed in RAM Frame.

Take the time now to review the various other reports available in the Reports menu.

Continue to RAM Concrete Beam Tutorial
Go back to RAM Frame - Drift Control Tutorial
Up to the RAM Structural System Tutorial