This article outlines the general workflow for the PT Design Optimization feature in RAM Concept.
Step 1 – Model design strips and punching shear checks
This step is required to produce designs in any RAM Concept model and is not unique to the PT Design Optimization workflow.
Step 2 – Model tendon layout using tendon parameter objects
This step is also required when designing PT floors in RAM Concept and is not unique to the PT Design Optimization workflow.
The tendon layout (locations of the tendons in plan) needs to be defined by the user before starting the optimization, because the optimization only investigates changes to strand count or profile elevations but not the horizontal placement of the tendons within the floor. In general, the optimization will not produce an optimal PT design from a poor tendon layout.
In RAM Concept, tendons can be modeled using two different approaches (or a combination of the two):
When using the PT Design Optimization feature, preference should be given to the automated tendon generation workflow, because only the properties of Tendon Parameter objects are changed during the optimization calculations.
In previous versions, jacks and PT loss calculations were available for manual tendons only. In version 6.5.0, jack regions were added to the tendon parameter layer and allow for PT loss calculation of generated tendons.
If you are not familiar with tendon parameters, a quick reference is available at the link below:
Automated Tendon Generation in RAM Concept
When models with manual tendons are optimized, the user is prompted to either keep the manual tendons in the model or delete all of them automatically. Manual tendons that are kept are considered in the optimization calculations and can affect the properties of the optimized tendons that are changed during the search.
Step 3 - Define optimizable objects and set max/min search values
Before an optimization is started, the user must select the objects that are to be modified during the optimization with a range of property values to be considered in the search. These objects are referred to as optimizable objects in the PT Design Optimization workflow.
The following Tendon Parameter objects in RAM Concept can be defined as optimizable objects:
Tendon objects and profile polylines that are designated as optimizable objects are displayed on screen with a different pen color than non-optimizable objects. This allows users to easily distinguish objects that are defined as optimizable from those that are not.
To designate tendon objects as optimizable, view the properties of the banded tendon polyline or distributed tendon quadrilateral, click on the Optimization tab, check the Optimize box, and set the range and increment values (see image below). Non-integer values are permitted for the specified strand number. The minimum value should be calculated based on code required minimum precompression. The maximum value can be based on practical maximum precompression limits.
To designate a profile polyline as an optimizable, view the properties of the polyline, click on the Optimization tab, check the Optimize box, and enter values for the elevation range and elevation increment (see image below). Typically, support profile polylines (high points) will be set to the highest possible elevation respecting cover requirements and defined with the Optimize box unchecked. An exception is the high point at a cantilever, which may need to be reduced from the maximum value so the cantilever is not overbalanced. The span profile polylines (low points) will typically be defined as optimizable.
Note that the elevation values set in the optimization tab refer to the “Elevation Reference” set in the general tab. For example, if “Elevation Reference” is set to “Above Soffit” for a support polyline, then the values will be measured from the bottom of the slab. We recommend using a wide range for the profile elevations, as counterintuitive values may be associated with the optimal design.
Eliminating profile polylines that you do not need is a good idea as it can reduce the number of optimizable objects and decrease optimization time. The Adjust Profile Polylines tool () on the Tendon Parameters Layers was added in v6.5.0 to automatically manipulate polylines and prepare them for optimization. This tool can automatically extend profile polylines to the slab edge, trim profile polylines to the slab edge, delete short polylines, and connect nearby endpoints for polylines with like properties (which merges them into a single polyline).
Step 4 - Define optimization regions (if needed)
In RAM Concept, Optimization regions are used exclusively for PT Design Optimization and serve the following purposes:
Optimization regions are required when there are more than 75 optimizable objects within the floor. If an optimization region has more than 75 optimizable properties, you will need to either adjust the optimization regions or make a change to the optimizable objects. If the whole model has 75 optimizable properties or less, then no optimization regions need to be defined. The number of optimizable objects that are associated with an optimization region can be displayed using the Optimization tab in the Visible Objects. The number of objects is also displayed in the Start Optimization dialog that appears on screen when an optimization is started.
For best performance, we recommend limiting the number of optimizable properties in any one optimization region to 50.
Since optimizable objects are automatically split at the borders of optimization regions, it is best to use as few optimization regions as possible when optimizing an entire floor. When regions are required, a good rule of thumb is to define the optimization regions to match expected slab pours. This has the added benefit that tendon quantities can change at region boundaries (due to object splitting), which is also normally possible at pour breaks.
Step 5 - Review material and labor costs for PT, rebar, and SSR defined in the Estimate window
The optimal design is the design that minimizes the total material and labor cost of PT, rebar, and stud rails and has no design code failures. To calculate the material and labor costs, the program multiplies the PT, rebar, and SSR quantities by the cost factors that are defined in the Estimate window accessed from Reports > Estimate (see image below).
In general, the default cost factors will work well for most optimizations. However, the material and/or labor costs of any one of the reinforcement components can be changed for a given project to account for regional cost differences or favor certain design alternatives (for example, those not requiring SSR). When modifying the default cost factors, the relative cost among the PT, rebar, and SSR is more important than entering the actual material or labor cost for the job and location being designed.
Step 6 - Start the Optimization
A new optimization can be started by selecting the Optimize Tendons tool () or clicking Optimization > Optimize Tendons. This kicks off a preprocess that performs a series of checks and splits optimizable objects at the boundaries of optimization regions, as needed.
During the preprocess, RAM Concept automatically saves a Scenario Model, which is a copy of the base .cpt file that includes any changes made to the optimizable objects made during the preprocess. The Scenario Model ensures consistency between the model data and the optimization data that is stored with it.
After the preprocess, the Start Optimization dialog appears (see image below). To start the optimization, enter a Scenario name, review the Stopping Criteria settings, and then click OK. In general, the default settings in the Start Optimization dialog produces good results in nearly all models.
Step 7 - Monitor the optimization
The PT Design Optimization feature is designed so that it runs in the background without the need for watching or monitoring the optimization. This allows the user to focus on other engineering tasks or start work on another RAM Concept model while the optimization calculations are completed.
During the optimization process, the Optimization Manager window (see image below) may be used to periodically monitor convergence or verify that valid solutions have been found. The Optimization Manager is launched by selecting by selecting the Optimization Manager tool () or clicking Optimization > Optimization Manager.
The Optimization Manager window shows the status of the optimization (running, stopped, run failure), the number of iterations completed, % improvement, and details of the total cost of each trial completed during the process.
The Stop button can be used to stop the optimization process at any time. You may want to stop an optimization if you see most of the trials have failures or if the optimization process seems too slow to converge to a solution. The Resume button can be used to continue trials that were stopped.
The Convergence Chart tabulates the Total Cost (y-axis) versus completed Iterations (x-axis) for the selected scenario. Three lines are plotted: Best Overall Design (with failure penalty), Best Overall Design (without failure penalty), and Best Valid Design (no failures).
The Trials Table at the bottom of the Optimization Manager displays the cost information and failures for each trial analyzed during the optimization. The values in the tables can be sorted by clicking on the column headers. For example, click once on one of the Cost column headers to sort the trials from ascending or descending values. If you click on the Failures column first and then Total Cost, the trials will be sorted by number of failures from least to greatest and also sorted cost by total cost. So, all trials with 0 Failures will be listed at the top of the dialog and all trials with 0 failures will also be sorted from least to greatest cost.
Scenarios and trials are saved with the .cpt file as long as the Scenario files created by the program have not been deleted. After a file is closed and reopened, you can launch the Optimization Manager to review information from previously created scenarios and load trials.
Step 8 - Load Results
During the optimization or after the optimization completes, any of the design alternatives can be loaded into the model using the Load Best or Load Selected buttons in the Optimization Manager. After loading a trial, the tendon profiles and the reinforcement design can be reviewed after running the calculations.
In some cases, the analyzed trial may yield an unexpected result or design failures. When this occurs, the loaded trial can be re-run after making small adjustments to the tendon objects and/or profile polylines to produce a final valid design.
Scenarios and trials are saved with the .cpt file as long as the PTOpt folder, which is stored in the same directory, has not been deleted. After a file is closed and reopened, the information from previously created scenarios is read back into model file and can be reviewed using the Optimization Manager.