Guide to Coordinated Design of Racking and Cold Storage Structure: Adapting AS/RS Automated High-Bay Racking with Large Column Spacing

Guide to Coordinated Design of Racking and Cold Storage Structure: Adapting AS/RS Automated High-Bay Racking with Large Column Spacing

1. Why Structural and Racking Design Must Be Coordinated

A common pitfall in cold storage design is treating structural design and racking design as independent tasks: structural engineers complete the building and structure first, then racking suppliers install the racking system within the finished cold storage. This sequential approach may be acceptable for traditional small cold storages, but for modern cold storages incorporating AS/RS automated high-bay racking, the cost of misalignment can be significant.

The core issue is that AS/RS racking systems (including stacker cranes, shuttles, and automated conveyors) have strict geometric constraints with the structural column grid. If the two designs are not coordinated, the consequences range from local compromises in rack layout (reducing storage density) to costly structural modifications, or in extreme cases, the racking system cannot be implemented as intended.

BIM collaborative design is the tool to address this challenge. BICP's Taiku system design services have integrated racking-structure coordination analysis into the standard workflow.

---

2. Core Constraints of AS/RS Racking on Column Grid

Integer Multiple Relationship Between Rack Bay Spacing and Column Spacing

AS/RS racking is arranged in rows, each row consisting of storage cells. Between rows are aisles for stacker cranes. The rack bay spacing (distance between centerlines of adjacent stacker aisles) is determined by rack depth and aisle width, typically ranging from 2.5 to 4.5 m, depending on rack model and stored goods dimensions.

Structural columns can only be located between rack rows, not within a rack row or in a stacker aisle. Therefore, the structural column spacing must be an integer multiple of the rack bay spacing (or satisfy a specific integer relationship) to ensure columns align precisely with the separation points between rack rows.

Example: If the rack system requires a bay spacing of 3.6 m, the structural column spacing should be an integer multiple of 3.6 m: 7.2 m (2×), 10.8 m (3×), 14.4 m (4×). Choosing a 12 m column spacing would not satisfy the integer multiple relationship, causing misalignment and difficulties in rack layout.

Coordination of Rack Height and Floor-to-Floor Height

AS/RS rack height is constrained by two factors: the clear height of each cold storage floor (from floor slab underside to floor surface) and the required clearance between the top of the rack and the slab underside (typically at least 300–500 mm for installation, maintenance, and emergency egress).

Greater clear height allows more rack levels, increasing storage density per unit area. Therefore, floor-to-floor height planning should start from rack height requirements, not from industry conventions. The advantage of post-tensioned flat slabs—saving 800 mm per floor—is particularly valuable in AS/RS cold storages: the saved height can be used for additional rack levels, directly increasing storage capacity.

Matching of Point Loads and Slab Force Distribution

AS/RS racking loads are transmitted to the floor (or slab) through rack column feet, creating concentrated point loads. The location of these column feet must align with the slab's structural zones: ideally, column feet should be placed over slab supports (near column heads) rather than in the mid-span region, to avoid unfavorable additional bending moments.

In BIM collaborative analysis, overlaying rack column foot locations on the slab reinforcement drawing and verifying each load point is a key step.

---

3. Standard Collaborative Design Workflow

BICP provides the following collaborative design support to owners as part of Taiku structural technical services:

Phase 1: Racking Parameter Collection (Before Structural Design Initiation)
Collect key parameters from the racking supplier:

• Rack bay spacing (including aisle width and rack depth)
• Rack height and column foot layout
• Maximum load per column foot
• Installation tolerance requirements for stacker crane rails

Phase 2: BIM Coordination Analysis
Import the rack layout into the structural BIM model and perform:

• Geometric clash detection between structural columns and rack row separation points
• Verification of rack column foot loads against slab force distribution zones
• Deflection control checks for slab areas under stacker crane rails

Phase 3: Iterative Optimization
Based on coordination analysis results, adjust column spacing, rack bay spacing, or column positions in coordination with structural designers and racking suppliers until a match is achieved. Output the final coordinated design deliverables.

---

4. Case Study: Xinrongmao Cold Chain Project

In the Xinrongmao cold chain project, which features a fully automated fruit and vegetable high-bay racking system, BICP conducted coordination analysis with the racking supplier during the planning and design phase. Based on the rack system's bay spacing parameters, a post-tensioned wide-beam flat slab structural scheme was selected, and the column grid was specially matched to ensure precise alignment between structural columns and rack rows, enabling the successful implementation of the automated intelligent cold storage.

---

5. Recommendation: Earlier Coordination, Lower Cost

The ideal time to initiate racking-structure coordination is during the schematic design phase, when the cost of adjusting column spacing is nearly zero. If conflicts are discovered after construction documents are complete or construction has started, the cost of adjustments increases significantly.

Owners are advised to initiate structural design consultation and racking system selection simultaneously at the start of a cold storage project, with BICP facilitating collaborative design to resolve potential conflicts at the drawing stage, contributing to smooth project execution.