This document describes new or enhanced features of STAAD Foundation Advanced (SFA) since the CONNECT Edition V9.3 (Release 9.3.0.14).

__Wind load generation for vertical vessels per PIP STC01015 2017 / ASCE 7-2010__

For vertical vessels, wind load generation is now available per the April 2017 edition of the PIP STC01015 code which in turn directs the user to the Wind load generation chapters of the ASCE 7-2010 code as mentioned in section 4.1.4.1 of the PIP document.

The salient aspects of the implementation of the code are:

__Step 1: Computation of the wind pressure from equation 29.3-1 of ASCE 7-10. __

The equations mentioned in that section of the code, for the English unit system (foot, pound),

qz= 0.00256*Kz*Kzt*Kd*V^2 lb/ ft2

as well as the SI unit system (meter, kNs),

qz= 0.00613*Kz*Kzt*Kd*V^2 N/m2

have been implemented.

The input that the engineer needs to provide are:

V - Basic Wind Speed in mph or meter per second (Section 26.5 has guidelines for this)

Kd = wind directionality factor defined in Section 26.6 of ASCE 7-2010

Exposure category – B, C or D – as per Section 26.7.3 of ASCE 7-2010

Kz = Based on the exposure category, program selects the value of velocity pressure exposure coefficient evaluated at height “z” from the table provided in Section 29.3.1

Note:

SFA does not take the values from the table directly. Instead, it calculates Kz from the formulae provided at the bottom of Table 29.3-1. An extract from the code is shown below.

Kzt = Topographic factor defined in Section 26.8.2.

Note: If site conditions and locations of structures do not meet all the conditions specified in section 26.8.1 of the code, one is allowed to set Kzt to 1.0. Since there are no provisions in SFA to specify site conditions (ridge, escarpment or hills), a value of 1.0 is used for Kzt.

G = gust-effect factor from Section 26.9

Cf = Net force coefficient from Fig 29.4-1

__Step 2: Computation of the force at various heights above the ground, and the resulting shear and moment at the top of pedestal__

The force due to wind acting at various levels along the height of the pedestal and vessel is calculated using the guidelines provided in Chapter 29 of ASCE 7-2010. Specifically, equation 29.5-1 is used to determine the force at various heights “z” above the ground.

F = qz * G * Cf * Af [Af= Height segment x Width or diameter]

Table 29.3-1 on page 310 of ASCE 7-10 is used to find the exposure coefficient Kz and the height ranges for which it is applicable.

The region spanning the distance between the ground level upto the top of the vessel is divided into various height segments as explained in Table 29.3-1 and the wind force is calculated for each segment. The force is considered to act at the mid-height of the respective segments, which provides the level arm for calculating the moment at the bottom of the pedestal.

Below are the screens from the program’s user interface where the wind load data is provided.

The output produced by the program is as shown below.

__Generation of Load Combinations per PIP STC01015 for Vertical Vessel foundations__

For vertical vessels in the PLANT mode of SFA, load combinations can now be generated for vertical vessel foundations per the Process Industry Practices standard titled

**PIP STC01015 Structural Design Criteria – April 2017 Revision**

Section 4.2.1 of that standard states that load combinations need to be generated per the ASCE standard

**ASCE/SEI 7-10 - Minimum Design Loads for Buildings and Other Structures**

Hence, users will be able to find this code in SFA under the name

**PIP STC01015-April 2017/ASCE 7-10**

as shown in the next figure.

The combined set of rules of these two codes is illustrated in Tables 6 and 7 of the PIP document under section 4.2.2.3, and those are the ones implemented in SFA too.

An inspection of the load combinations listed in these tables will reveal that certain basic load data needs to be specified before the combinations can be generated, such as,

- Operating Dead Load (Do)
- Empty Dead Load (De)
- Test Dead Load (Dt)
- Temporary Thermal (Tt)
- Sustained Thermal (Ts)

etc., as mentioned in section 4.1 of the PIP STC01015-April 2017 document. In SFA, these can be specified in the primary load cases page as shown below.

Load combinations per Table 6 are generated under the heading Service Load Combinations, and, load combinations per Table 7 are generated under the heading Ultimate Load Combinations.

__Grouping of isolated footings has been re-instated__

For isolated footings, older versions of SFA (the version 8 series or older) had an option called Create Group. This option was used to obtain a single footing size that can be applied to all the support nodes that are included in the current isolated footing job. In other words, all the support nodes in that job would be assigned the same footing size. However, this feature had been disabled during the past few versions of SFA for various reasons.

This has now been re-instated.

This option can be found under the Tools menu.

In order for the program to successfully determine a single size, the conditions that must be satisfied are:

- The isolated footing job must contain more than support
- The footing design type (in the Footing Geometry page) must be “Calculate Dimension”
- The maximum size limits for length, width and thickness must be large enough that the program should be able to successfully find a size for all the footings before it begins the grouping operation.

To execute this operation,

- create an isolated footing job that satisfies the aforementioned requirements
- select the footings for which you would like the program to determine a common size

Select the “Create Group” option as shown in the figure above, and, specify a job name when prompted for that.

The calculations will begin soon after that. Note that the process will involve more time than what is required for a “Set Dimension” or a “Calculate Dimension” operation.

Typically, the result of this operation would be that all the footings will receive the same size as the largest one obtained from a Calculate Dimension operation. However, if for any reason, any of the footings are found to fail with that size, the program will iterate again until a single successful size is obtained for all of them. In certain instances, a smaller plan size (than the largest size described above) too may be found to be suitable.

Note that the grouping exercise is performed only for the “dimensions” of the footing. It does not apply to the reinforcement provided within the individual footings and hence that may be different between the footings.

Calculation reports are created for each footing providing the details of the analysis and design performed, based on the final size that is assigned to them.

The summary table may be used to examine the size and reinforcement details for all the footings in a compact page.

This feature has been restored for all design codes available in the program’s General mode.

__Miscellaneous enhancements and correction of defects__

- Design of pedestals per the Eurocode has been implemented for combined footings in the General mode.
- An error in the development length calculations for isolated, combined footings and pilecaps per the Australian code has been corrected.
- Results of oneway shear design in the local XY plane for combined footings, which were omitted from the calculation sheet by oversight, are now available. Also available now for the same module and code is oneway shear design results for the longitudinal plane.
- An error in the effective depth calculation for pilecaps for corner pile punching has been corrected for various codes.
- Arrangement of longitudinal bars for pedestal design is presented in a more informative manner for all codes and all modules that have this feature.
- An error in the oneway shear calculation for octagonal footings per the Australian code has been corrected. Additionally, an error that was present in the punching shear perimeter calculations when the shape of the pedestal is circular has also been corrected.
- An error that caused the program to report a highly inefficient size for an octagonal footing for vertical vessels per the Indian code has been corrected. Also corrected were some errors in the calculation of the wind force per this code for vertical vessel foundations.
- An error in the calculation of reinforcement spacing as well as the number of bars for isolated footings per various codes has been corrected. This change will also allow for more economical arrangements to be determined.
- Punching shear check for isolated footings per Eurocode is now performed at two locations – at the face of the column/pedestal, and, at 2d away from the face. In past versions, this check was performed only at the “2d” distance.
- For combined footings, the calculation sheet now contains a table of corner pressures for ultimate load cases for combined footings. This is done to facilitate manual checking of the pressures, shear and moment values used in the concrete design.
- Some errors that caused a failure in the analysis of design of strap footings has been corrected.
- Better checking for input errors has been implemented for various modules including tank foundations and vertical vessel foundations.
- Some errors in the calculation of ring wall reinforcement arrangement for tank foundations has been corrected.
- An error in the calculation of wind loads for the tank foundation module per the Indian code (IS875) has been corrected.
- The process involved in finding an optimum size for combined footings has been improved.
- Concrete and steel quantities (MTO table) are now reported for more foundation types.
- Miscellaneous errors in the analysis and design of foundations for horizontal and vertical vessels have been corrected. One such error caused the program to report a highly inefficient footing size for vertical vessels per the Indian code.
- Miscellaneous errors in the input handling, analysis, and output presentation for drilled piers have been corrected based on user feedback. Also corrected is an error that prevented users from specifying a steel section of their choice.
- An error that caused the overturning check results to be erroneous in some cases for isolated footings has been corrected.
- Some errors in the bar arrangement determination as well as moment capacity calculation for mat foundations for various codes has been corrected. Also corrected was an error that caused the graphical display of some of those results to differ from the information presented in the calculation report.
- The analysis and design of combined footings has been enhanced to check the actual soil pressure against an allowable soil pressure for ultimate load cases. The permissible soil pressure for ultimate load cases is based on a principle that is similar to what has been implemented for isolated footings.
- An error in the time period calculation for vertical vessels per the Indian code has been corrected.
- The error was found in the computation of gross bearing capacity from net bearing capacity in cases where load factors are involved for the dead load case, and has been corrected.
- A unit-related error in reporting the soil density and soil height values for mat foundations has been corrected.
- For pedestal design per the ACI metric code, the metric bar database has now been implemented along with facilities for specifying the minimum and maximum bar size limits desired by the user.
- A defect that caused the overturning stability check for mat foundations for load combination cases to be erroneous has been corrected.
- The weight of soil on mats is now treated as an element pressure load instead of an equivalent slab selfweight. This will allow the analysis to be performed without a superfluous warning from the STAAD engine for excess selfweight.
- For isolated footings, an error in the punching shear calculation per the Indian code has been corrected.