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Horizontal load resisting system in buildings

Short answer

Horizontal loads are resisted by braced frames (diagonal braces), moment frames (rigid joints), shear walls, or dual systems. Roof and floor diaphragms distribute force to vertical elements. Design follows IS 800 and NBC 105, considering drift and architectural needs.

Describe the horizontal load resisting system in steel structure building.

Horizontal loads on steel buildings (wind and earthquake) are carried to the foundation by a lateral load resisting system. Floors and roofs act as diaphragms that distribute the lateral force to vertical resisting frames.

Main systems

  1. Braced frames (concentric / eccentric): diagonal, X, K or V bracings between columns carry the lateral load by axial force in members. Stiff and economical for low and medium rise buildings.
  2. Moment-resisting (rigid) frames: beam-to-column joints are rigid and resist the lateral load by bending of beams and columns. Gives open bays but larger sections and costly joints.
  3. Shear walls / core: RC or steel plate shear walls in lift and stair cores resist storey shear.
  4. Dual systems: moment frame combined with bracing or shear wall; share the load by relative stiffness.
  5. Tube systems: closely spaced perimeter columns and deep spandrels form a stiff tube for tall buildings.
  6. Roof/floor bracing and diaphragms: horizontal bracing in plan and rigid slabs transmit forces to the vertical frames.
  Braced frame        Moment frame
  |\  /|              |==|==|
  | \/ |              |  |  |
  | /\ |              |==|==|
  |/  \|              |  |  |

Choice depends on height, drift limit, architectural openness and cost. IS 800 and IS 1893 / NBC 105 control the load and detailing.

✓ Answer checked by Claude Opus 5.5 (high effort)

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