Suzhou Tianhuan Phase II C# Cold Storage Project

1. Cumulative vertical load effect: The total vertical load from 12 floors transfers to the ground columns and foundation, resulting in axial forces far exceeding those in low-rise cold storage. Structural design must systematically consider load accumulation while precisely controlling self-weight of each floor slab. The post-tensioned flat slab solution reduces slab thickness and self-weight while meeting load requirements, positively impacting the design of ground columns and foundations. 2. Inter-story drift control: The 68.1-meter height generates significant lateral deformation under wind and seismic loads compared to low-rise buildings. Excessive drift affects the operational precision of high-rise racking systems and the connection details of insulation systems. The floor post-tensioning system must be coordinated with the lateral force-resisting system (core wall or shear wall) to ensure adequate floor stiffness and overall drift control. 3. Long-term post-tensioning performance: All floor slabs must maintain effective prestress levels throughout the service life, requiring accurate estimation of long-term prestress losses and appropriate initial tensioning forces.

1. Global model analysis: A three-dimensional finite element program (imported from the US) combined with proprietary post-tensioning optimization algorithms was used to establish a full-building model. The stress states of each floor slab under combined vertical and lateral loads were systematically analyzed to ensure rational distribution of design margins and optimal overall post-tensioning efficiency. 2. Refined prestress loss calculation: A statistical analysis-based method was adopted to account for long-term loss factors such as concrete creep, shrinkage, and steel relaxation, providing sufficient safety margins for the long-term performance of each floor slab. 3. Structural self-weight control: The post-tensioned flat slab solution controlled slab thickness while meeting load requirements, reducing self-weight per floor and mitigating cumulative vertical load effects, thereby improving the stress conditions of ground columns and foundations. 4. Construction organization: A floor-by-floor staged construction plan was developed to address safety and sequencing challenges of post-tensioning work at height. Post-tensioning was initiated only after concrete reached specified strength, with on-site equipment calibration before each operation. Special safety measures were implemented for high-altitude tensioning, and all tensioning data were recorded per floor to create a fully traceable construction archive. A floor-by-floor handover record system was established, with post-tensioning acceptance synchronized with the main structural acceptance to ensure traceable quality across all floors.

Suzhou Tianhuan Phase II C# Cold Storage Project: Design and Construction Practice of Post-Tensioned Structure for a 12-Story, 68.1m High-Rise Cold Storage

Project Background

After the continuous operation of Phase I cold storage, Suzhou Tianhuan Cold Chain Logistics Co., Ltd. initiated Phase II expansion driven by market demand. The C# cold storage, as the core unit of Phase II, is positioned as a multi-temperature-zone composite high-rise cold storage facility, serving as a cold chain distribution hub for Suzhou and surrounding areas.

The combination of 12 stories, 68.1-meter structural height, and 57,000-square-meter floor area places this project among the highest levels of high-rise cold storage under construction in China. At this scale, the technical requirements for structural design and construction management are significantly higher than those for conventional low-rise cold storage.

BICP undertook the post-tensioned structural technical services for the C# cold storage, implementing a large-span post-tensioned flat slab system across all 12 floors.

Technical Challenges

Cumulative vertical load effect. The total vertical load from 12 floors is ultimately transferred to the ground columns and foundation, resulting in axial forces in ground columns far exceeding those in low-rise cold storage. Structural design must systematically consider the cumulative effect of loads from all floors from a holistic perspective, while precisely controlling self-weight in the load-bearing design of each floor slab to avoid unnecessary load accumulation. The post-tensioned flat slab solution can reduce slab thickness and structural self-weight while meeting load requirements, positively impacting the design of ground columns and foundations.

Inter-story drift control. The 68.1-meter height generates significantly greater lateral deformation under wind and seismic loads compared to low-rise buildings. Excessive drift can affect the operational precision of high-rise racking systems and adversely impact the connection details of insulation systems. The floor post-tensioning system must be coordinated with the lateral force-resisting system (core wall or shear wall) to ensure floor stiffness and overall drift control meet design requirements.

Long-term post-tensioning performance. All floor slabs of the 12-story cold storage must maintain effective prestress levels throughout the service life, requiring high accuracy in estimating long-term prestress losses and reasonable determination of initial tensioning forces.

Solution

Global model analysis: A three-dimensional finite element analysis program (imported from the US) combined with proprietary post-tensioning optimization algorithms was used to establish a full-building model. The stress states of each floor slab under combined vertical and lateral load conditions were systematically analyzed to ensure rational distribution of design margins and optimal overall post-tensioning efficiency.

Refined prestress loss calculation: A statistical analysis-based method for refined prestress loss calculation was adopted, comprehensively considering long-term loss factors such as concrete creep, shrinkage, and steel relaxation, providing sufficient safety margins for the long-term performance of each floor slab.

Structural self-weight control: The post-tensioned flat slab solution controlled slab thickness while meeting load requirements, reducing self-weight per floor and mitigating the cumulative effect of vertical loads, positively influencing the stress conditions of ground columns and foundations.

Construction Organization

Post-tensioning construction for the 12-story high-rise cold storage presented special challenges in terms of high-altitude work safety and process coordination. BICP developed a floor-by-floor staged construction plan for this project:

Post-tensioning of each floor slab was initiated only after the concrete reached the specified strength. Equipment was calibrated on-site before tensioning to ensure accuracy of tensioning forces. Special safety measures were implemented for high-altitude tensioning operations. All tensioning data were recorded per floor, forming a complete and traceable construction archive.

BICP's project team established a floor-by-floor handover record system. The acceptance of post-tensioning works was synchronized with the main structural acceptance, ensuring traceable quality of post-tensioning works across all floors.

Delivered Value

The large-span post-tensioned flat slab system effectively reduced the number of internal columns on each floor, improving rack layout conditions for multiple temperature zones and enhancing warehouse management efficiency. The floor height control advantage of the post-tensioned flat slab system, compounded across 12 stories, positively impacted overall building height and volumetric efficiency.

Project Reference Significance

This project is a representative engineering practice by BICP in the field of high-rise cold chain buildings (12 stories, 68.1m). It validates the engineering applicability of large-span post-tensioned flat slab systems in managing cumulative vertical loads, coordinating inter-story drift, and ensuring long-term prestress performance in high-rise cold storage. It provides an engineering reference for structural system selection in similar high-rise cold chain storage projects.

The large-span post-tensioned flat slab system effectively reduced the number of internal columns on each floor, improving rack layout flexibility for multiple temperature zones and enhancing warehouse management efficiency. The floor height advantage of the post-tensioned flat slab system, compounded across 12 stories, positively impacted overall building height and volumetric efficiency. This project represents a benchmark engineering practice by BICP in high-rise cold chain buildings (12 stories, 68.1 m), validating the applicability of large-span post-tensioned flat slab systems in managing cumulative vertical loads, coordinating inter-story drift, and ensuring long-term prestress performance. It provides a valuable engineering reference for structural system selection in similar high-rise cold chain storage projects.