STAAD Foundation Advanced CONNECT Edition V9 Update 3

Generation of Load Combinations per ASCE 7-2016

In the General and Toolkit modes of SFA, load combinations can now be generated per the ASCE standard titled

ASCE 7-16 - Minimum Design Loads and Associated Criteria for Buildings and Other Structures

In order to generate combinations using this code, the basic load cases need to be assigned one of the following types in SFA.

- Dead
- Live
- Wind Along X
- Wind Along Z
- Seismic Along X
- Seismic Along Y
- Seismic Along Z
- Fluid Load
- Snow Load
- Dead Weight of Ice
- Flood
- Active Earth Pressure
- Rain
- Self Straining (Loads due to Temperature & Shrinkage are included in this type)
- Wind on Ice Along X
- Wind on Ice Along Z
- Roof Live

The combination cases generated by SFA are in accordance with Section 2.3 of the ASCE 7-16 document for Strength Design, and, Section 2.4 of that document for Allowable Stress Design. Recall that for foundation designs based on the ACI 318 code, the concrete design of foundations must be based on combination cases for strength design, while soil pressure and stability checks should be done using combination cases for allowable stress design. (Strength cases are also referred to by the name Ultimate cases in SFA.)

In SFA, a facility for generating these combinations is available in the General mode and in the Toolkit mode, with separate buttons for service and strength. Each mode of the program contains a table that comes populated with the factors for the respective load types. The following figure shows the facility that is available in the General mode.


In those instances where a certain load type is a candidate for both signs (positive as well as negative), multiple load combination cases, that account for all combinations of the sign, will be generated. Wind, Seismic, Wind on Ice, etc. are the basic cases that fall in this category. For example, a combination of Dead load with 0.6*Wind Load will produce the following combinations

D + 0.6Wx
D + 0.6Wz
D - 0.6Wx
D - 0.6Wz
where D is Dead, Wx is Wind Along X, and Wz is Wind along Z.

Notice in the above figure that there is a check box in the second column, which if unchecked, instructs SFA that the combination case defined by that row should not be generated.

Notes:

- If the SFA model is created by importing the support reactions from the analysis of a superstructure model, such as from STAAD.Pro or an ISM repository, and if load combinations have already been specified in that superstructure model, the user can directly import the reactions for those combination cases which would eliminate the need to create the combinations inside SFA.
- SFA allows the user to assign a few more types to the basic load cases than the ones listed earlier in this document. See the following figure.


Some examples are Wind on Ice (without any direction), Ash Mass, Crane, etc. However, these types are not mentioned in the ASCE 7-16 document, and consequently, there are no load factors available in the load combination table in SFA for that code. As a result, if we assign those types to any of the basic load cases, they will be excluded from the generated combinations. Users can avoid this by setting their type to the ones named User1, User2, etc. and providing a factor in the table under those headings. A warning to alert the user to this possibility is reported by the program if such a situation is encountered.

Combined Footing Design

STAAD Foundation Advanced now supports the standards for foundation design for China GB 50007-2011 Code for design of building foundation for the analysis and design of combined footings.


This feature is available through the General mode of the program. In the Toolkit mode and PLANT mode, the Chinese code is currently not available for these or other types of foundations.

How does one create a combined footing job?

In the section titled What’s New in CONNECT edition V9.1, the procedure used for creating an isolated footing job to the Chinese code was described.


The same procedure can be used to create a combined footing job.


The rules for performing the concrete design of the footing are similar to those for other codes. Users are urged to go through the various sections of the Technical manual for information on this topic.

The sections of the GB 50007 code that are used in performing the various checks for combined footings are similar to those for isolated footings, and those are available as shown in the topic highlighted in the next figure.


Calculation report

If the design of the footing is successful, a calculation sheet is displayed containing the details for the checks mentioned above, and the governing load case for each check. For a failed design, the cause of the failure has to be interpreted by reading the messages displayed in the Output Pane, which is the panel below the drawing area.

The report can be obtained in either Chinese or English


Drawings

Drawings of the foundation plan and layout are also produced.


Solved examples

Two solved examples that illustrate the procedure used for designing these footings is available in the verification manual of this program.


The SFA models for these examples are available in the Examples folder.


Implementation of the ACI Metric Bar database

For all the foundation types in SFA for which design can be performed per the metric editions of the ACI 318 code, the reinforcing bar database that is used henceforth is per the specifications of that edition. Most of these editions have an Appendix where the bar details are listed. Shown here is the one for the 2011 edition.



Implementation of the Australian reinforcing bar database

For all the foundation types in SFA for which design can be performed per the Australian code AS3600-2018, the reinforcing bar database per the Australian standards is now available. The source of this information is the Australian standard AS/NZS 4671:2001 with Amendment No.1


Pilecap module – identifying the individual piles with a number

For the pilecap module, in the various places where the pile arrangement is available in pictorial form, each pile is now annotated with a number for quick identification. This enables easier correlation between the pile and the forces in the pile as reported in the tables for oneway shear, punching shear, etc., in the calc report.



Viewing the pile reactions for a mat foundation on piles

For mat foundations on piles, a table that shows the pile reactions for all the piles of the current mat job for the selected load case is now available for viewing from a table named Pile Reactions in the output pane. Please note that the selected load case should be part of the current mat job if its reactions are to be displayed. This is because, the reactions are calculated only for those load cases which are included in the job and analyzed. Hence, if the selected load case it is not included in the job, the table will be blank for that case.


Miscellaneous enhancements

1. For combined footings, a table of soil pressures for ultimate load cases is now provided in the calculation sheet. This is to assist users who are interested in validating the shear force and bending moment values used in the various concrete design checks.


2. The name of the code used in the load combination generation is now mentioned in the calculation report.


3. Octagonal footings can now be designed per the Australian code AS3600-2018


4. For pilecap jobs, the loads applied at the top of the pilecap are now presented in separate tables - one for service cases, the other for strength cases. In past versions, this segregation was not available.


5. Pedestal design to various codes such as ACI, Australian, etc., is now available for many more foundation types.


6. For a mat foundation on piles, the pile reaction summary presented in the calculation sheet is now reported in two separate tables – one for service cases, the other for ultimate cases.


7. For pilecaps, the pile reactions are forcibly calculated as soon as the analysis is launched. This has been done because there are numerous ways in which data that affects the pile reactions can be altered. To avoid the possibility of an accidental omission in keeping track of those changes, as well as to avoid forcing the user to calculate the reactions manually each time such a change is made, the process of calculating the reactions has been automated so that the design of the pilecap reflects the most up-to-date changes in the input data.
8. For pedestal design per the various editions of the ACI 318 code, the value of Pn,max is now annotated on the P-M curve.


9. For a mat foundation job, if there are pedestals beneath the columns, the program was failing to consider the pedestal weight for the analysis of the mat. This has been rectified.
10. An error in the location of the column design load on the P-M curve for the Australian code has been corrected. This affects isolated footings and combined footings which have pedestals.
11. An error in the calculation of reinforcement bar spacing for isolated footings designed to the ACI 318 codes has been corrected.
12. The global setting for the value of the height of the pedestal for design for axial load + biaxial bending was not being honored for the Australian code. This has been corrected.
13. Miscellaneous improvements have been made in identifying errors in input. For example, for vessel foundations, if time period is specified as 0.0, the user is notified of this through a warning message. Identification of empty load cases is another – these are load cases which have only a title but contain no load items.
14. An error in calculating the bending moments in pilecaps under buoyant conditions has been corrected.
15. For pedestal design to the Australian code, in version 9.2.0.34 of SFA, a check described in Clause 10.6.3 which says that columns can be designed to that clause only if their L/B ratio does not exceed 3.0, had been implemented, where L and B are the longer and shorter of the cross section dimensions of the column. However, the pedestal design implementation in SFA is not based on this clause. Instead, it is based on Clause 10.6.4. Hence, the above check is not applicable, and has been removed.
16. For mat foundations designed to the ACI 318 codes, various numerical errors in the values shown in the plot of the moment capacity diagram and in the details presented in the calculation sheet for reinforcing zoning reports have been corrected. Also corrected was an error in the calculation of effective depth used in these computations.
17. In past versions, soil pressure diagrams were being displayed for mats supported only on piles (meaning, no soil supports are present). This has been corrected. These diagrams will henceforth appear only if soil supports are present.
18. An error in identifying corner piles for a vertical vessel on a square footing on piles has been corrected.
19. Minimum steel calculation per the Eurocode was based on the full depth of the footing. This has been changed to effective depth as required by section 9.2.1.1 of Eurocode 2.
20. An error that caused a failure to consider the column reaction loads for a mat foundation in some instances has been corrected.

System Requirements

- The following hardware requirements are suggested minimums. Systems with increased capacity provide enhanced performance.
- PC with Intel-Pentium or equivalent.
- Graphics card and monitor with 1280x1024 resolution, 256 color display (16 bit high color recommended).
- System memory: Minimum of 1 GB is required and suitable for small to medium problems; 2GB is recommended. However, for large, complex problems up to 8 GB may be needed.
- Windows 8.1 (64 bit) or Windows 10 (64 bit) operating system.

Note: Windows XP, Windows NT, Windows 2000, and Microsoft® Vista, Windows 7, and 32-bit versions of Windows are no longer supported.
- Sufficient free space on the hard disk to hold the program and data files. The disk space requirement will vary depending on the modules you are installing. A typical minimum is 500MB free space.
- A multimedia ready system with sound card and speakers is needed to run the tutorial movies and slide shows.

Additional RAM, disk space, and video memory will enhance the performance of STAAD Foundation Advanced.

You should have a basic familiarity with Microsoft Windows operating systems in order to use the software