ACI KUET Student Chapter | CSI SAFE Master Roadmap

CSI SAFE Foundation Design Course: Isolated & Combined Footing Modeling

               720K+ Views • Curated for Undergrads
            

Video Overview: Step-by-step tutorial on importing column base reactions from ETABS, assigning subgrade soil modulus, and verifying punching shear ratios.

Foundation Engineering: Getting Started with CSI SAFE

Every superstructure load ultimately transfers to the supporting geotechnical soil strata. If soil bearing capacity or settlement tolerances are breached, severe structural tilting or failure can occur. Follow these verified foundation design steps:

Step 01 • Data Integration

Exporting Column Reactions from ETABS (.F2K Text File)

Rather than manually typing dozens of column axial forces and moments, export base reactions directly from ETABS in one unified step:

In ETABS, go to File > Export > Story as SAFE .F2k Text File
Select the Base story and check "Export Floor Loads and Loads from Above"
Launch CSI SAFE and navigate to File > Import > .F2k to populate all column locations and reaction load combinations

Step 02 • Geotechnical Springs

Soil Subgrade Modulus & Allowable Bearing Pressure

Soil is not an infinitely rigid table; it behaves like an elastic spring bed under foundation footings. Compute subgrade modulus from geotechnical soil reports:

Subgrade Modulus Formula: ks = 40 × Factor of Safety × q_all (kN/m³) per Bowles standard recommendations
Under Define > Soil Subgrade Properties, input calculated subgrade modulus (Compression Only)
Draw footing geometry, assign soil support, and verify that contact pressure does not exceed allowable bearing capacity (q ≤ q_all)

KUET Geotechnical Tip: Soils in the Khulna region commonly contain soft cohesive silts and organic clays. Always confirm settlement limits (maximum total settlement ≤ 25 mm for isolated footings, ≤ 50 mm for rafts per BNBC 2020).

Step 03 • Punching Shear

Two-Way Punching Shear Capacity Ratio Audit (Ratio < 1.0)

To ensure columns do not punch through the foundation slab, verify two-way shear capacity along critical perimeters at distance d/2 from column faces:

Select Design > Show Punching Shear Design after analysis
Confirm that every column punching shear stress ratio remains strictly < 1.0
If the ratio exceeds 1.0, increase footing thickness (effective depth d) or provide a pedestal / drop panel

Master-Level Foundation Design

Mat/Raft Foundation & Pile Cap Finite Element Design in CSI SAFE

               High-Rise Mat & Piled Raft
            

Lecture Overview: Advanced finite element modeling of raft foundations, non-linear tension-free soil springs, and structural pile group caps.

Pro Step 01 • Raft Modeling

Mat / Raft Foundation Modeling & Non-Linear Soil Spring Analysis

When individual isolated footing areas exceed 50% of the total building footprint, a unified mat/raft foundation is the most economical and rigid solution:

Assign mat slab thickness (typically 20 to 36 inches / 500 to 900 mm for 6-10 storey structures)
Setup non-linear soil support cases (Tension-free springs; soil carries zero tension)
Check differential settlement between adjacent columns remains within permissible limits (δ < 1/500)

Pro Step 02 • Design Strips

Column & Middle Design Strips (Layer A & Layer B)

To extract exact rebar areas along orthogonal directions across raft panels, define structural design strips:

Draw Column Strips and Middle Strips along the X-Direction (Layer A)
Draw Column Strips and Middle Strips along the Y-Direction (Layer B)
Execute finite element slab design to extract required top and bottom steel areas (mm²/m)

CSI SAFE 20: Foundation & Slab Design Mastery

Select Your Current Expertise Level