IS 1173 : 1978Hot rolled and slit steel tee bars

IS 1173:1978 specifies the dimensions and properties of hot-rolled and slit steel tee bars (T-sections) — the standard T-section range used as struts, ties, chord members of light trusses, bracing, and fabricated sections. Design is to IS 800; this provides the tee geometry/properties.

It sits in the steel-section stack:

• IS 800 — steel design · IS 808 — rolled section dimensions (beams/columns/angles) · IS 12778 — parallel-flange sections
• IS 2062 — structural steel · IS 1852 — rolling/cutting tolerances · IS 1252 — bulb angles

IS 1173 tabulates standard tee sizes and section properties, with a design subtlety from the section shape:

• A tee is mono-symmetric (symmetric about one axis only), with the shear centre at the flange/stem junction — like channels and angles, this makes it prone to flexural-torsional behaviour and means its compression/bending capacity is not governed by simple doubly-symmetric I-section rules
• Tees are efficient as truss chord/strut/tie members and as structural splits of I-sections (a tee cut from an I-beam)
• Standard sizes/properties for IS 800 checks; quality is IS 2062; allow IS 1852 tolerances on critical members

The engineering point: like other mono-symmetric sections (channels, angles, bulb sections), a tee's asymmetry must be respected in design — particularly flexural-torsional buckling in compression and the eccentric connection at the stem. Used as a truss member with the right capacity checks it is efficient; designed with I-section intuition its true buckling capacity can be over-estimated.

Scenario: a tee used as a compression chord/strut in a light truss designed to IS 800.

Step 1 — section from demand: select the standard IS 1173 tee whose tabulated properties meet the IS 800 member checks.

Step 2 — respect mono-symmetry: check flexural-torsional buckling in compression (not just flexural buckling); account for the shear-centre/connection eccentricity at the stem.

Step 3 — connections: detail the (often eccentric) stem connection; account for the eccentricity in the member/connection design.

Step 4 — tolerances/quality: IS 1852 tolerances on critical members; quality IS 2062; verify designation on delivery.

With flexural-torsional behaviour and connection eccentricity respected, the tee is an efficient truss member; with I-section intuition its compression capacity is over-estimated.

1. Ignoring flexural-torsional buckling. Mono-symmetric tees don't follow doubly-symmetric I-section rules — check FTB in compression.

2. Neglecting connection eccentricity. The stem connection is typically eccentric — account for it in member/connection design.

3. Treating it as a quality spec. Geometry/properties only; quality is IS 2062.

4. Non-standard sizes. Off-standard tees may be unavailable — design to standard designations (or detail as a verified split of an I-section).

5. Ignoring rolling tolerances on critical members. Allow IS 1852.

• IS 800 — steel design (FTB/eccentricity checks) · IS 808 — rolled section dimensions · IS 12778 — parallel-flange sections
• IS 2062 — structural steel · IS 1852 — rolling/cutting tolerances
• IS 1252 — bulb angles · IS 1863 — bulb flats (other asymmetric sections)

IS 1173 is reaffirmed and supplies standard tee-section geometry/properties — efficient for truss chords, struts, ties and as structural splits of I-sections — whose practitioner caveat is the familiar mono-symmetry one shared with channels, angles and bulb sections: the section is symmetric about only one axis, so flexural-torsional buckling in compression and connection eccentricity at the stem must be checked, and doubly-symmetric I-section intuition over-estimates capacity. Use the tabulated properties in the IS 800 checks, design to standard designations (or as a verified split of an I-section), allow IS 1852 tolerances on critical members, and treat quality as IS 2062. Respect the asymmetry and the tee is an efficient, versatile member; ignore it and the compression capacity you relied on isn't there.