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Document Type: FAQ Product(s): LEAP RCPIER Version(s): All Original Author: Bentley Technical Support Group
Document Type: FAQ
Product(s): LEAP RCPIER
Version(s): All
Original Author: Bentley Technical Support Group
ANSWER:
Impact factor, IM = 33% which is applied to Truck only is generally applied to the analysis results (moments and forces) of the load combinations and envelopes.
RCPier while designing the footing does not consider the impact factor (33%) (Please check the user manual).
These are some of the suggestions to reduce the number of Load combinations and eventually Analysis and Design time.
1) Program generally generates the wind load at every 15 degrees , i would recommend the users to delete the wind loads generated at 15 ,45 and 75 degrees as it is not required to generate at every 15 degrees and even at every 30 degrees the program will generate fairly good results. This will help in reducing number of load combinations and eventually Analysis time.
2) If possible try to select only the critical vehicles which will generate worst reactions and this will help the user to reduce the number of LL cases. This will help in reducing number of load combinations and eventually Analysis time.
3) Thirdly user can go to combination and click on parameters and select Dependent load cases instead of cross combination . If incase dependent load case option does not work you can manually go to dependency table separate the load cases or the dependency by selecting None. Cross combination generally generates a lot of load combination which will increase the analysis time.
4) Use only the load groups which are required for that particular project.
5) Do not generate Braking force load cases along with the Live loads. Only one braking force is enough for analysis purpose.
6) Try to save the file on the C: drive (local drive).
7) Close all the other programs while running this particular file .
RCPier does not design the piles , only the pile reactions are reported in the Design Status output report.
RCPier does not handle soil interaction for the piles.
Regarding the Multiple presence factor , if the user is inputting the LL reactions manually then he has to multiply the MPF with the LL reactions and then input the values in RCpier .When the user generates the Live load reaction then the program multiplies the LL reactions with the MPF in the LOADS TAB itself.
RCPier can handle 3 different types of code .
1) US AASHTO code
2) Canadian CHBDC code
3) Indian IRC code.
The program designs the drill shaft based on the values of H and h1 . h1 value is below the ground and H-h1 is the value between the bottom of the column and top of the ground.H-h1 value is used in the frame action to calculate the moment on drill shaft and anything below the ground is designed only for the gravity load. RCpier does not handle soil interaction for Drill shaft.
If the user is expecting the program to use revised effective footing width/length after ignoring the footing portion which is under tension. Program does not handle this. It simply warns the user that footing is under tension. The footing width needs to be changed manually and the design needs to be rerun.
In Structure Model ,
P represents the PLASTIC HINGE LOCATIONS -->
@ COLUMN TOP --> Cap Column joint
@ COLUMN BOTTOM --> Column base.
F represents the Flexural/Shear CAP Design --> @ FACE OF SUPPORT .
One place where the user can modify the curb-curb width manually is in the Geometry Tab where in the user needs to click on the Super Structure button and in the dialog box you can change the curb to curb distance manually.
But the way program analyzes is that it assumes that the width is being placed symmetrically over the pier and ignores any eccentricity due to different curb width that means it assumes same curb width on both sides.
One of the suggestions would be to make the program assume the maximum curb to curb distance so that it covers all the scenarios and gives maximum reactions and also if user wants to add any other additional reactions on the substructure due to the eccentricity (due different curb width) then it can be applied manually . For further information on how RC pier does LL Analysis, user can check the theory section of the manual .
Please refer to the page HC-51 from Tutorials volume of the manual.
The formula used for calculation of pile reactions does not have the pile section properties in it. Pile section is irrelevant when computing reactions. RC-PIER does not design piles.
Some of the pile reactions will be in compression and some in tension, regardless of pile section properties.
Under analysis TAB we cannot see the P-delta effect . P-delta can be seen only on the column design status. In the analysis Tab it will be just first order analysis. If p-delta option is checked, the related effect is handled internally in RC-PIER for pier column design and reported only in column design status. P-delta effect is not shown in the Analysis TAB results.
Yes, the program always runs through the number of iteration the user sets it for .
The auto compute geometry by girders option is used to read girder geometry property from Leap bridge.
This option will help in reading the geometry of girder which will be eventually used to calculate the Dead Load of the Superstructure in the LOADS tab.
This option is not used in the stand alone RCPier program.
This option will be removed in the future version of RCpier .
Moments amplified by P-Δ are used only for column design ,they are not applied to the cap and footing designs.
So only moments amplified due to Moment magnification method will be transferred to cap and footing.
Yes the shaft is treated as part of the column and the p delta effects are applied in the design of shaft as well.
RC-PIER takes the portions of the drilled shaft below fixity point as a member supported laterally. In this case, only the axial load is considered. For the portion of the drilled shaft above fixity point, RC-PIER assumes there are no lateral supports. Therefore, it is designed exactly the same as a reinforced column, taking into consideration of both axial load and moments.
Right now we don’t have additional documents except for the user manual and tutorial regarding the Strut-and-Tie for RC-PIER. The RC-PIER uses standard solver to handle the truss analysis internally. RCP does plane frame analysis; truss is a special case of a plane frame 2 degrees of freedom per node instead of 3.If the user really wants to verify the analytical resultsof the truss, he/she can use general structural analysis programs to do it.However, RC-PIER does both analysis and design.
Tutor 3 example file has information on how to input the Strut and Tie model to Pier cap and footing .
Also the user can check the tutorials which explains the procedure on how to model the Struts in footing.
Rx, Ry, and Rz are rotational stiffness of the spring, and the unit is kip-ft/radian.
User needs to just input the creep and shrinkage value in the program as shown in the screenshot and the program will internally use it in design.
When the slab is poured there is no continuity onlythe load is applied to the deck is treated as continuous model and since the slab concrete is fresh concrete, at this time the DL reactions are calculated and the slab is treated as simple span. This is the reason the program shows same reaction for both simple span as well as continuous span bridges.
In RCpier to transfer the load from superstructure to substructure it is required to provide a minimun of 2 bearings. For integral slab by default the program generates the bearings at every 2ft . If the user has to provide the bearings manually then at every 2ft should be fine.
The Resp. Mod. Factor that needs to be inputted under Auto Load Generate is for the superstructure/Substructure connection .
The Resp. Mod. Factor that needs to be inputted under Analysis TAB / Seismic Design Parameters is for the Substructure (Column/Pier).
DC is basically for Components & Attachments & Self Weight basically Non Composite Dead loads .
DW load is for Wearing surface and utilities which is basically for Composite Dead loads.
DC and DW loads are treated separately.
Dead loads are distributed based on the Effective width between the bearings.
Beff for bearing 1 is calculated from the edge of the box girder to the midpoint of Bearing 1 and bearing 2 .
The Beff for the Bearing 2 is calculated from midpoint of Bearing 1 & 2 and Midpoint of Bearing 2 & 3 . Please see the
attached screenshot.
It’s in Article 3.6.1.3.1 under commentary (page 3-25) AASHTO code .
You have to apply ICE load based on AASHTO article 3.9 and per your local conditions. RCPier does not have any kind of library for different flood levels. You have to apply manually calculated ICE load as point load. Local DOT specifications needs to be checked. Select ICE load from load type and then click on EDIT .In column Loads/Settlement apply the force (Ex: 10 kips at 0.5 y1/L ) at half height.
Certain load cases are internally dependent to each other , for example Braking force and Live Load .
The number of braking force load cases should match the number of live load cases.
To separate the dependency In the Loads TAB the user needs to click on Combination options --> Parameters --> New window Combined parameters --> Click on Dependent Load case combination option--> Dependency Table button .
In the new window Loads Dependency Table --> Select BR Braking force under load case --> Under "Depends On" heading select NONE from the drop down menu .
Please see the attached screenshot for more information.
Currently it is not possible to model a crash wall in RCpier but the user can model a strut as a crash wall and analyze the structure. That is the only workaround solution and in the future versions Crash wall design option will be added in the program.
User needs to click on the Footing TAB --> At the bottom of the screen user needs to check the box which says " Check for cracking and Fatigue " . Please see the attached screenshot for more information.
User needs to go to Loads TAB and at the bottom of the screen the user needs to Check the box which says
" Reset Loads when changes to model are made " . Please see the attached screenshot for more information.
The user needs to click on Help and from the drop down menu he/she needs to select the Contents option and in the new window "RCpier Help " the user should be able to see the user manual in .chm format. Please see the attached screenshot for more information.
User needs to go to Geometry TAB and then click on Structure Model and in the new window under Hinge heading user needs to check the box which says " Local Direction Z ".
User needs to click on the Combination button in the Loads TAB and in the new window "Load Combinations" the user needs to click on ADD button and then he/she can input the custom LC name and the respective load factors .
To Edit an existing load combination the user needs to click on the EDIT button and then he/she can modify the LC factors.
Please see the attached screenshots for more information.
If Ast provided > As_reqd then Mr is based on As_provided if it is less then the program prints Mr based on min reqd and flags at As_provided .
In the current version RCpier program is not capable of applying Response modification factors separately for bending moment ,shear and axial forces.
See Also
Product TechNotes and FAQs
Bentley Technical Support KnowledgeBase
Bentley LEARN Server
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