H-Beams in Steel Frame Structures
Hot rolled H-beams form the primary skeleton of steel frame buildings: columns carry vertical load, beams carry floor and roof load, and channels and angles complete the frame as purlins, girts and bracing. The H-section's wide flanges give strong resistance to bending and buckling in both directions, which is why it dominates modern frame construction.
Frames can be simple beam-and-column construction with bolted shear connections, or rigid portal frames with moment connections, depending on the building height and loading.
The Five Common Grades Compared
H-beams are rolled in the following grades, which cover most international projects:
Q235B per GB/T 700: yield 235 MPa, the economy grade for light frames.
SS400 per JIS G3101: tensile minimum 400 MPa, the common Asian trade grade.
S275JR per EN 10025-2: yield 275 MPa, the standard European frame grade.
Q345B per GB/T 1591: yield 345 MPa, the traditional Chinese high-strength grade.
S355J2 per EN 10025-2: yield 355 MPa with impact at minus 20 degrees Celsius, for heavy and cold-service frames.
The selection depends on the design code, the loads and the climate. For projects certified to European rules, EN grades are mandatory; for Asian projects, GB or JIS grades are normally specified.
Section Sizes and Series
Frame sections are chosen from the GB/T 11263 series, with HW and HM for columns and HN for beams, or from the European HEA, HEB and IPE series. Typical columns range from 200 x 200 mm to 500 x 500 mm and beams from 300 x 150 mm to 900 x 300 mm. Standard lengths of 6 m, 9 m and 12 m cover most grids.
Frame Connections
Column bases are welded to base plates and anchored to foundations. Beam-to-column joints use end plates, fin plates or seat angles, bolted on site. Stiffeners are added at concentrated load points, and haunches reinforce the eaves of portal frames. All holes are drilled in the workshop to the shop drawing.
Quality and Documentation
Beams are tested for chemical composition and mechanical properties per heat, and certificates are issued to the required standard. Dimensional inspection covers depth, flange width, web thickness, straightness and section squareness. Bundles are protected with timber dunnage and strapped for transport.
Frequently Asked Questions
Q: Which grade is best for a steel frame in a temperate climate?
S275JR or Q235B is normally sufficient for light and medium frames. Use S355J2 or Q355 for heavy loads or where the ambient temperature can fall below 0 degrees Celsius.
Q: What is the role of channels in a steel frame?
Channels are used as purlins, girts, edge beams and secondary members that transfer cladding loads to the main H-beam frame.
Q: Can I mix GB and EN grades in one frame?
Yes, but each member must be designed with the properties of the grade actually supplied, and the grade must be marked on the member.
Q: How are frame members connected on site?
Standard practice is bolted connections with high-strength bolts; welding on site is limited to repairs and special details.
Q: What documentation is delivered with H-beams?
Mill test certificates, dimensional inspection reports and, where required, welding procedure and NDT records for fabricated members.