Xinrongmao Cold Chain Project

Structural safety under backfill loads: Flat slabs are widely used in cold storage for their simplicity and headroom efficiency, but they are vulnerable to punching shear at column heads under heavy loads (backfill, stacked goods), which can cause sudden and dangerous failure. Chinese review agencies strictly scrutinize flat slab punching shear under backfill, limiting design options. Special requirements of AS/RS: Tall racks with concentrated loads require precise column grid alignment and rack rail matching; structural design must be coordinated with rack layout. Headroom control: Minimizing beam depth to preserve internal clear height is essential for AS/RS operation.

Post-tensioned wide shallow beam solution: Wide shallow beams are embedded in the slab to transfer column loads through beam bending, avoiding the punching shear failure mode of flat slabs and facilitating engineering review. The 'shallow' aspect controls beam depth to save headroom, while the 'wide' aspect provides sufficient flexural capacity. Post-tensioning is applied to the beams, actively counteracting load moments, increasing load capacity without increasing beam depth, and improving crack resistance. Compared to conventional frame beam-slab structures, floor-to-floor height is reduced by approximately 500 mm, decreasing excavation depth and backfill thickness, and lowering overall earthwork and anti-flotation costs. BIM-based rack system coordination: During structural design, technical coordination with the rack supplier was conducted using BIM to ensure precise alignment of column grids with rack layouts and load concentration points with beam positions, avoiding rework and design changes during rack installation. Post-tensioning construction followed a specialized plan, with stressing initiated after concrete reached specified strength and data recorded per span to match design values.

Xinrongmao Cold Chain Project: Engineering Practice of Post-Tensioned Wide Shallow Beam Solution in Fully Automated Fruit and Vegetable Cold Storage

Project Background

Xinrongmao Group is a major importer of fresh fruit in China, with a supply chain covering global fruit-producing regions. As the imported fruit market expands, the company requires enhanced cold chain storage capacity and automation to support fully automated storage and retrieval systems (AS/RS) for fruit and vegetable cold storage. The project is a cold storage facility converted from an underground garage roof slab with backfill soil, imposing dual constraints: the punching shear risk of flat slabs under backfill loads often fails engineering review, and the AS/RS demands precise column grid alignment, slab load capacity, and deformation control. BICP was engaged to provide post-tensioned structural design and technical services, proposing a post-tensioned wide shallow beam solution with BIM-based rack system coordination.

Technical Challenges

Structural safety under backfill loads: Flat slabs are widely used in cold storage for their simplicity and headroom efficiency, but they are vulnerable to punching shear at column heads under heavy loads (backfill, stacked goods), which can cause sudden and dangerous failure. Chinese review agencies strictly scrutinize flat slab punching shear under backfill, limiting design options. Special requirements of AS/RS: Tall racks with concentrated loads require precise column grid alignment and rack rail matching; structural design must be coordinated with rack layout. Headroom control: Minimizing beam depth to preserve internal clear height is essential for AS/RS operation.

Solution

Post-tensioned wide shallow beam solution: Wide shallow beams are embedded in the slab to transfer column loads through beam bending, avoiding the punching shear failure mode of flat slabs and facilitating engineering review. The 'shallow' aspect controls beam depth to save headroom, while the 'wide' aspect provides sufficient flexural capacity. Post-tensioning is applied to the beams, actively counteracting load moments, increasing load capacity without increasing beam depth, and improving crack resistance. Compared to conventional frame beam-slab structures, floor-to-floor height is reduced by approximately 500 mm, decreasing excavation depth and backfill thickness, and lowering overall earthwork and anti-flotation costs. BIM-based rack system coordination: During structural design, technical coordination with the rack supplier was conducted using BIM to ensure precise alignment of column grids with rack layouts and load concentration points with beam positions, avoiding rework and design changes during rack installation.

Implementation

Post-tensioning construction followed a specialized plan, with stressing initiated after concrete reached specified strength and data recorded per span to match design values. BIM models were updated in real time, ensuring precise alignment of column grids, beam positions, and rack layouts at the construction drawing level, effectively controlling design changes during installation.

Delivered Value

Upon project completion, the post-tensioned wide shallow beam solution met backfill load safety requirements while providing the structural space needed for the AS/RS. Rack installation proceeded smoothly without conflicts between structure and rack layout. Compared to conventional frame beam-slab structures, floor-to-floor height was reduced by approximately 500 mm, lowering excavation and backfill costs. Compared to flat slabs, structural safety was enhanced, passing engineering review and alleviating the owner's safety concerns. This project demonstrates BICP's '3D BIM collaborative analysis and design of building and rack systems at the planning and design stage' in a high-end intelligent cold storage facility, validating the applicability of the post-tensioned wide shallow beam solution under complex loading conditions (backfill + heavy AS/RS).

Reference Value

This project provides a reference for cold storage facilities converted from underground garage roofs with heavy backfill, where flat slab punching shear limits are exceeded and high headroom is required, as well as for intelligent cold storage projects needing precise AS/RS adaptation.

Upon project completion, the post-tensioned wide shallow beam solution met backfill load safety requirements while providing the structural space needed for the AS/RS. Rack installation proceeded smoothly without conflicts between structure and rack layout. Compared to conventional frame beam-slab structures, floor-to-floor height was reduced by approximately 500 mm, lowering excavation and backfill costs. Compared to flat slabs, structural safety was enhanced, passing engineering review and alleviating the owner's safety concerns. This project demonstrates BICP's '3D BIM collaborative analysis and design of building and rack systems at the planning and design stage' in a high-end intelligent cold storage facility, validating the applicability of the post-tensioned wide shallow beam solution under complex loading conditions (backfill + heavy AS/RS). The project provides a reference for cold storage facilities converted from underground garage roofs with heavy backfill, where flat slab punching shear limits are exceeded and high headroom is required, as well as for intelligent cold storage projects needing precise AS/RS adaptation.