1 - Overview

Performing the analysis on a stack of vertical members can be performed two different ways using the Eriksson Commercial Suite, either by using the Column / Panel Stack or by using reinforcement interrupts. Descriptions of each method can be found below.

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1 - Column / Panel Stack

The design file contains the design information for a single precast element and thus only a single elements results are reported.

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1.1 - Methodology

The addition of a member stack to a design is handled by converting the additional members and loads into loads that act on the top of the design file. This is done by performing an analysis on the entire system in order to determine what forces and moments are being transferred from the above system into the design file. Once this is found, those loads are added to the currently design file and the procedure continues the same as it would if it were not a stack.

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1.2 - Assumptions

The analysis on the full stack is performed using an elastic first order analysis. Since we do not have reinforcement of the other members in the stack, cracked section properties cannot be calculated and hence are neglected. The full second order analysis is performed on the individual precast element at which point cracking is considered. The panel to panel connections are ignored when performing the analysis on the individual design panel.

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1.3 - Use Cases

2.4 - Limitations

3 - Reinforcement Interrupts

3.1 - Methodology

3.2 - Assumptions

3.3 - Use Cases

3.4 - Limitations

4 - Example Problems

4.1 - Eriksson Wall

4.2 - Eriksson Column

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This approach is commonly used for preliminary designs where exact information is not known. The user desires a stripping and handling analysis be performed (since with the other method we are not modeling individual elements) and when the above elements are not precast concrete pieces. Since the analysis is using just base section properties for this analysis it also works for mixed structure types.

1.4 - Limitations

This method does have a few limitations. The first is for problems with large P-Delta effects, the loads being transferred into the top of your design element may be lower than what the member would typically see. This is because the P-Delta effects will increase the internal forces that need to be transferred. It also does not model any joint connectivity when designing the individual piece. Because of this it is going to allow the top of the design member to deflect freely although the member is partially restrained.

2 - Reinforcement Interrupts

The design file contains the design information for each precast element in the stack and thus the results for all members are reported.

2.1 - Methodology

When using reinforcement interrupts the user models the concrete for the entire system. They than can input any hinges at any location they want to release moments (note: reinforcement is automatically cut and redeveloped at a hinge). To model fixity, the user can choose not to put in a hinge but instead put reinforcement interrupts at the joint location. An interrupt gives the user control over what type of reinforcement is cut at this location giving the user the ability to cut strand but leave mild reinforcement (or dowels) crossing the joint. The full second order analysis is then performed on the entire stack.

2.2 - Assumptions

The only assumption that is made is on the joint connectivity. The assumption of either full moment or no moment transfer.

2.3 - Use Cases

If you do not need a stripping and handling analysis and the entire system is precast concrete this methodology will be more accurate. It will be a more accurate second order analysis and makes it easier to check the reinforcement on the entire system at a time.

2.4 - Limitations

The joint connectivity does not allow partial fixity which is probably closer to what is seen in the field. It is up to the engineer if they want to transfer the moment or not. The reinforcement across the joint need also be accurately accounted for. If you are releasing the moment at the joint but still want reinforcement about the joint this will require the user input a bar in both the top and bottom half of the joint that is set to anchored for its end condition.

Note: Eriksson Column does allow partial fixity between Columns but it is up to the user to determine the stiffness of the joint.

3 - Example Problems

3.1 - Eriksson Wall

3.2 - Eriksson Column

4 - Related Pages