Series 1: The Basics

Recently a series of video tutorials were created to demonstrate different features of SFA. We will go through each one of those tutorials in details. This following write-up is the precursor of the videos related to global setup.

STAAD Foundation Advanced (SFA) is not like any regular spreadsheet type design utility program. It’s an integrated solution which helps user to design foundations for the entire project. It offers tools such as “General Arrangement” (GA) drawing to decide appropriate foundation types. It can iterate through hundreds of load combinations and design most efficient foundations. Output includes construction ready detailed drawing and detailed calculation sheet which produces step by step calculations with applicable equations, code clauses and intermediate values. The sketches are included to make sure sign conventions are defined and understood properly.

So, to take advantage of the rich features of SFA it is important to setup the foundation model at the beginning. Program is so designed that user should follow some initial steps to setup the project layout to take full advantage of the program and gain maximum efficiency.
Data in SFA can broadly be categorized as global and local data. Data which are related to external source or data which don’t depend on the foundation type are categorized as global data. Global data are grouped in three main categories which are “Foundation Plan”, “Loads and Factors” and “Soil Properties”. All the groups are important but “Foundation Plan” and “Loads and Factors” are essential for setting up the foundation analysis/design environment.

On the other hand, local data are specific to foundation types. For example data needed to design a pile cap would be different than the data needed to design an isolated footing. Pile properties would be unique to pile cap design module and isolated footing module would require soil bearing capacity as the footing will be supported by grade.

In this tutorial we will be discussing how to setup and the importance of global data.

Step 1:

The first step is to setup the proposed foundation positions. As SFA is a 3D modeling environment, foundation positions are defined in Cartesian coordinates (x, y, z) where Y axis is vertically up and axis system follows right hand rule (like in STAAD.Pro).

Foundations can be of various types such as multi column strip (or combined) footing or spread (or pad) footing or a generalized flexible mat foundation. Before design, it is often not known what type of foundation is most suitable, so instead of defining foundations user is asked to start by laying out column positions. For any building, column is supported at ground and needs a foundation. But in SFA column locations can be defined as any point where an external load is acting, it may or may not be a part of the building structure. These points are called “Column Positions”.

So, first layout the physical columns and other load application point coordinates. Program by default assumes columns are of rectangular shape and assigns column length and width. Engineers must review and set proper dimensions as these dimensions will be used for shear and moment checks. But for industrial structures or steel columns such as wide flange, pedestal is used to connect column to the footing. There is a separate page in the program to define pedestal shapes and dimensions. It is important to note if a column is connected to a pedestal, column dimension won’t be used for any design check. So, if there is a pedestal, user can ignore column dimension setup for that particular column.

If a pedestal is associated to a column, program assumes all loads are acting at the top of the pedestal. During design process all the lateral forces will be transferred from the top of the pedestal to the bottom of the foundation by multiplying the lateral forces with the summation of pedestal height and footing thickness.

Step 2:

The next step is setting up the loads. SFA performs serviceability checks like bearing capacity and stability checks such as sliding and overturning for allowable stress load combinations only and concrete design is performed for ultimate load combinations only. If a load combination is defined as “Primary” and used to design, it will be used for both service and ultimate design. But it is highly recommended that only load combinations be used for design. In many cases design for primary loads such as wind or seismic may not converge as there might not be enough dead load to resist the overturning moment.

The very first step of “Load and Factors” is to create “Primary” loads such as “Dead “, Live”, “Wind”, “Seismic” etc. Then create load combinations either by manual definition or by using load combination generation tool. So, it is obvious to select the proper load type while creating a primary load if load combination generation tool to be used.

Step 3:

Data flows between global and local data through a layer called job setup. A job must be set to design any footing. Main navigator leafs will be rearranged based on the job type. “Job” properties include footing type (e.g. isolated, combined, pile cap, mat etc.), design code (e.g. ACI, BS etc.), default unit type (either English or SI) and the supports which will be assigned to that job. So, a job definition is essentially creating a group of footings which will have same types and same design parameters (like concrete grade, cover etc.) but may not have same dimensions.

Once the job is created a new set of commands will be created in main navigator. Each of those commands will need additional data which are called design parameters and the group with new commands is called local setup. Design function uses both global and local data to design each footing.
The most important purpose to separate data in global and local layers is to empower the user with the tools to experiment with different foundation types for the same footing and select the most suitable solution.

Following videos explain how STAAD Foundation Advanced program work and are recommended to watch.