Pipe Rack Design Guide (Part 2): Connection Detail & Checklist

8. Beam-to-column connections

8.1. Connection philosophy for pipe racks

• Bolted connections preferred — minimise field welding for speed and quality.
• Transverse direction: moment connections (rigid frames).
• Longitudinal direction: shear connections (beams act as struts or are braced).
• All connections must transfer: shear + moment (if rigid) + axial (if strut).

8.2. End-plate moment connection (most common)

• Type: flush or extended end-plate.
• Reference: AISC Design Guide 4 / 39.

Design steps:

• 1. Determine required moment (M_u) and shear (V_u) at the connection.
• 2. Select bolt configuration (4-bolt, 8-bolt).
• 3. Calculate end-plate thickness (yield-line method).
• 4. Check bolt tension (including prying action).
• 5. Check column flange bending / web yielding / web crippling.
• 6. Add stiffeners if the column is inadequate.

Key design checks

8.3. Shear connection (simple connection)

• Used for: non-moment beams, struts, secondary framing.
• Types: single/double angle, shear tab (single plate), end-plate shear.
• Reference: AISC Manual Part 10.
• Design checks: bolt shear, bearing, net section, block shear.

9. Base plate & anchor bolt design

9.1. Base plate design per AISC Design Guide 1

9.2. Fixed base design steps

• 1. Determine loads: P_u (axial), M_u (moment), V_u (shear).
• 2. Base plate size (B × N): must fit within the column footprint + clearance; check concrete bearing f_p ≤ φ(0.85f′_c)√(A₂/A₁).
• 3. Base plate thickness (t_p): based on bending of the plate cantilever (m, n dimensions); simplified t_p = 2.11 × √(M_u,plate / (F_y × B)).
• 4. Anchor bolts: tension T_u = M_u/d − P_u/n_bolts (for small axial); shear transferred by friction, bearing or shear lugs.
• 5. Anchor bolt embedment: per ACI 318 Chapter 17 (anchorage to concrete).

9.3. Anchor bolt checks (ACI 318 Ch.17)

10. Bracing design

10.1. Vertical bracing (longitudinal)

• Purpose: resist longitudinal lateral loads (friction, wind, seismic).
• Types: X-bracing (most common), inverted V (chevron), single diagonal.
• Location: every 3–5 bays. Coordinate with piping expansion loops.

10.2. Design checks for bracing members

Tension member:      Pn = Fy × Ag   (yielding)
                     Pn = Fu × Ae   (rupture)

Compression member:  Pn = Fcr × Ag  (buckling — AISC Ch. E)

Slenderness:         KL/r ≤ 200  (compression)
                     L/r  ≤ 300  (tension — recommended)

10.3. Horizontal struts

• Connect bents at beam level in the longitudinal direction.
• Must resist: friction force, tributary wind, strut force from the bracing.
• Often designed as compression members (they can buckle when the friction load reverses).
• Effective length: typically KL = the full bay length between bents.

10.4. Bracing connection (gusset plate)

• Gusset plates must transfer the brace force to the beam-column joint.
• Whitmore section for tension/compression capacity.
• Thornton method for gusset plate buckling.
• Block shear check at the bolt group.
• Clearance: ensure the 2t linear clearance (AISC requirement).

11. Practical detailing — tips from experience

11.1. Member orientation

• Columns: strong axis (x-x) oriented in the transverse direction — moment frame action is transverse, so maximum bending is about the strong axis.
• Beams: strong axis resists gravity loads (obvious).
• Struts: weak-axis buckling must be checked — it often controls.

11.2. Future expansion

• Design for 10–25% additional pipe load capacity.
• Leave space for future pipe levels.
• Foundation design should account for potential future uplift.
• Bracing locations should allow future piping runs.

11.3. Access & maintenance

• Clear height under the lowest beam ≥ 4.5 m (15 ft) for vehicle access.
• Maintenance platforms at each beam level (if required by operations).
• Ladder and stairway access per OSHA/local codes.
• Avoid placing bracing where it blocks access routes.

11.4. Fireproofing

• Required in some jurisdictions or by project specification.
• Typically intumescent paint or cementitious spray.
• Adds dead load (15–30 kg/m² of member surface area).
• Affects connection details — clearances are needed for fireproofing application.

12. Pipe support interaction

12.1. Support types

12.2. Information required from the piping team

• Pipe sizes, insulation thickness, content density.
• Support locations and types (rest / guide / anchor).
• Anchor loads (F_x, F_y, F_z) from piping stress analysis.
• Thermal expansion ranges and movement directions.
• Hydrotest requirements (which pipes, in what sequence).
• Future piping additions.

13. Deflection limits

14. Design checklist — complete project workflow

Phase 1: Input data collection

• Plot plan and pipe rack routing layout.
• Pipe list with sizes, insulation, content, temperatures.
• Cable tray layouts and weights.
• Geotechnical report (bearing capacity, seismic parameters).
• Project design criteria document.
• Piping stress analysis data (anchor/guide loads).

Phase 2: Configuration design

• Bent spacing determined (matching pipe support spacing).
• Rack width determined (from the pipe routing study).
• Number of beam levels determined.
• Column height determined (clearance requirements).
• Bracing bay locations selected (coordinated with piping).
• Future expansion allowance incorporated.

Phase 3: Structural analysis

• Load calculation complete (D, D_o, D_t, L, F_f, W, E).
• Load combinations per AISC/ASCE 7 established.
• Transverse bent analysis complete.
• Longitudinal braced bay analysis complete.
• Second-order effects (P-Δ) included.
• Member design ratios ≤ 1.0 (target 0.7–0.9).

Phase 4: Connection design

• Beam-to-column moment connections designed.
• Base plate and anchor bolts designed.
• Bracing gusset connections designed.
• Strut connections designed (shear + axial).
• Pipe support attachments detailed.

Phase 5: Foundation design

• Foundation reactions extracted from the structural analysis.
• Pedestal/pier sizing (gravity + moment + shear).
• Anchor bolt embedment per ACI 318 Ch.17.
• Foundation stability (overturning, sliding).
• Hydrotest load case checked on the foundation.

Phase 6: Drawing & documentation

• General arrangement drawings.
• Member schedule with sizes and materials.
• Connection details (standard and special).
• Foundation plan and details.
• Bill of materials.
• Calculation report.

15. Related standards — quick reference

Part 2 summary

Part of the series “Structural design for industrial facilities” — Roberto Structural. The content is technical guidance; the engineer remains responsible for checking and adapting it to the conditions of each project and the requirements of the governing code. © Compiled from AISC 360, ASCE 7, AISC Design Guides, PIP Standards and practical project experience.