STAAD.Pro

STAAD.Pro is a widely used structural analysis and design program. Learn its modelling workflow (nodes, members, properties, supports, loads, combinations), the STAAD input-file syntax, analysis types, design to codes (IS 456/800, AISC, Eurocode) and how to verify results.

Frames, trusses, industrial sheds, towers and building skeletons are routinely analysed in STAAD.Pro. The engineer builds a model of nodes and members, assigns sections, supports and loads, and the program solves the stiffness equations and checks members against design codes.

Its text-based input file (.std) makes models transparent and scriptable — and every command can be read and checked.

An analogy

A STAAD model is a digital meccano set: you place joints, connect them with members, bolt it to the ground, hang loads on it, and ask the computer how every piece is stressed.

Modelling workflow

Define geometry (joints and members) → materials and section properties → supports (fixed, pinned, springs) → load cases (dead, live, wind, seismic) → combinations → analysis → post-processing (diagrams, reactions, displacements) → design/code check.

Loads and combinations

Self-weight, member UDLs and point loads, floor loads distributed to beams, wind and seismic generators, and moving loads. Combinations follow codes (e.g. 1.5(DL + LL), 1.2(DL + LL ± EL)). Always inspect load diagrams before analysing.

Analysis options

Linear static, P-Delta (second-order), buckling, modal/response spectrum, time history, and non-linear cable/tension-only members. Member releases model pinned connections; offsets model rigid zones.

Design and verification

Steel and concrete design modules check members to codes, producing utilisation ratios. Verify: reactions balance loads, deflected shape is sensible, results match hand calculations for simple parts, units are consistent, and releases/supports reflect reality. OpenSTAAD enables automation from Excel/Python.

Formulas

• Stiffness solution: [K]{d} = {F}
• Portal method (lateral, fixed bases): column shear = H/n_cols, M = V h/2
• Equilibrium check: Σ reactions = Σ applied loads (each direction)

Worked example: Checking a portal under wind

Given: Portal 6 m span, 4 m high, fixed bases; 20 kN lateral at top

Find: Approximate column moments (portal method) to compare with STAAD.

• Shear per column = 20/2 = 10 kN
• Inflection at mid-height → M = 10 × 2 = 20 kN·m at top and base
• Column axial from overturning = 20 × 4/6 = ±13.3 kN

Answer: ≈ 20 kN·m moments, ±13.3 kN axial — STAAD should be close (exact depends on beam stiffness)

Worked example: Reaction check

Given: Beam UDL 15 kN/m over 6 m + self-weight ≈ 0.6 kN/m (ISMB400) + columns

Find: Expected total vertical reaction for DL.

• Beam: (15 + 0.6) × 6 = 93.6 kN
• Columns (ISMB300 ≈ 0.44 kN/m × 8 m) ≈ 3.5 kN
• Σ ≈ 97 kN → STAAD's summed vertical reactions should match

Answer: ≈ 97 kN total

Portal frame in STAAD input syntax

STAAD PLANE PORTAL FRAME
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 4 0; 3 6 4 0; 4 6 0 0;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 3 4;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
END DEFINE MATERIAL
MEMBER PROPERTY INDIAN
1 3 TABLE ST ISMB300
2 TABLE ST ISMB400
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 4 FIXED
LOAD 1 LOADTYPE Dead TITLE DL
SELFWEIGHT Y -1
MEMBER LOAD
2 UNI GY -15
LOAD 2 LOADTYPE Wind TITLE WL
JOINT LOAD
2 FX 20
LOAD COMB 3 1.5DL+1.5WL
1 1.5 2 1.5
PERFORM ANALYSIS
PRINT SUPPORT REACTION
PARAMETER 1
CODE IS800 LSD
FYLD 250000 ALL
CHECK CODE ALL
FINISH

Joints, members, properties, supports, loads, combinations, analysis and code check — the whole model in ~35 readable lines.

Common mistakes

• Wrong: Wrong units in the input file. — Right: Declare UNIT consistently (e.g. METER KN) and re-check after edits.
• Wrong: Unintended mechanisms from releases. — Right: Check stability warnings and the deflected shape.

Applications

• Industrial structures: Portal frames, pipe racks, crane gantries and towers.
• Buildings: RC and steel frames with code design.
• Bridges & special: Truss bridges, moving loads and foundations with springs.

Key takeaways

• Geometry → properties → supports → loads → analysis → design.
• The .std file is readable and scriptable.
• Use proper combinations and analysis types.
• Always verify with hand checks.

Going further

• OpenSTAAD: API for parametric model generation and result extraction.
• Response spectrum analysis: Modal combination (SRSS/CQC) for seismic design.
• Interoperability: Exchange with Revit, Tekla and RAM via ISM for BIM workflows.