Ensuring Structural Strength of Hollowed-Out Sections in UHPC Openwork Components: Design Optimization and Process Innovation Solutions

UHPC hollow-out components, with their lightweight forms and artistic texture, are increasingly widely used in architectural decoration, while the structural strength of hollow-out areas is the core of ensuring the safe use of components. Qinglong Group has been deeply engaged in the UHPC/GRC/GRG/GRP industry for 28 years. Through design optimization, material upgrades, and process innovation, it has successfully solved the challenge of strength assurance for components with hollow-out rates exceeding 50%, and the related technologies have been validated in projects such as the Ouargla Hotel in Algeria and the Liyuan Hotel in Nanning.

I. Core Design Principles for Strength Assurance of Hollow-Out Areas

The strength design of UHPC hollow-out components must follow three major principles: “clear load paths, dispersed stress concentration, and sufficient structural redundancy”. Qinglong adopts BIM parametric design and finite element analysis to simulate stress in hollow-out areas, optimizing hollow-out shapes and arrangements. Round and oval hollow-outs are preferred (avoiding right angles that cause stress concentration), with spacing between hollow-outs ≥ 1.5 times the component thickness. In the Ouargla Hotel project in Algeria, Qinglong controlled the hollow-out rate of UHPC hollow-out panels at 52%, reducing the maximum stress in hollow-out areas by 30% through a diamond-shaped arrangement design. Meanwhile, stiffening ribs are set along hollow-out edges (width ≥ 20mm, thickness ≥ component thickness) to form a “frame-type” load-bearing structure. For example, the colored hollow-out carved panels of the Liyuan Hotel in Nanning, through edge stiffening rib design, achieved a flexural strength of 32MPa, far exceeding standard requirements.

II. Material Formula Optimization and Reinforcement System Innovation

Material performance is the foundation of hollow-out area strength. Qinglong uses a UHPC formula combining high-grade cement, ultra-fine quartz sand, steel fibers, and reactive powders, with a steel fiber volume content of 2%-3% and fiber length of 12-15mm, which can effectively bridge cracks and transfer stress. For hollow-out areas, Qinglong innovatively adopts a composite reinforcement system of “steel fibers + glass fiber mesh sheets”, with 2-3 layers of glass fiber mesh sheets (mesh size 10mm×10mm) placed along the component thickness direction to enhance the tensile performance of hollow-out edges, increasing the tensile strength of hollow-out areas by 25%. In addition, by optimizing the water-binder ratio (0.18-0.20) and admixture dosage, the fluidity and compactness of UHPC are improved, internal defects in hollow-out areas are reduced, and strength uniformity is ensured.

III. The Role of Production Processes in Ensuring Hollow-Out Area Strength

Refined production processes are the key to avoiding insufficient strength in hollow-out areas. Qinglong adopts a “precise mold positioning + layered pouring” process. For hollow-out areas, special mold cores (made of GRP or polyurethane) are used to ensure precise hollow-out shapes, and release agent is applied to the core surface to prevent demolding damage caused by excessive bonding with UHPC. During pouring, the component frame is poured first, and then the areas around the hollow-outs are filled, with high-frequency vibration (frequency 200-300Hz) applied to ensure compactness and avoid defects such as air holes and honeycombing. In the steam curing stage, a “low-temperature slow curing” scheme is adopted for hollow-out components, with a heating rate ≤ 10°C/h and constant-temperature curing at 50-55°C for 18h, preventing cracking of hollow-out edges caused by thermal stress. In the Shanghai Astronomy Museum public art project, the hollow-out UHPC sculptures produced by Qinglong with this process were tested crack-free, with a 100% strength compliance rate.

IV. Strength Testing and Quality Control System

Qinglong has established a dedicated testing system for hollow-out areas, using load tests to check the overall strength of components. A uniformly distributed load (≥ 2.5kN/m²) is applied to the hollow-out area; no deformation or cracks within 24h constitutes a pass. Meanwhile, ultrasonic testing is used to check the internal compactness of hollow-out areas, with a sound wave velocity ≥ 4500m/s, ensuring no internal defects. During production, 3 components are sampled from each batch for destructive testing of the flexural and tensile strength of hollow-out areas; if the data fail, the entire batch is retested. Relying on strict quality control, Qinglong UHPC hollow-out components have been successfully applied in many major projects at home and abroad, maintaining good structural stability even with hollow-out rates up to 60%.

The strength assurance of UHPC hollow-out components is the result of synergy among design, materials, and processes. As a national Specialized, Refined, Distinctive, and Innovative enterprise and a participant in industry standard formulation, Qinglong Group will continue to deepen its technological R&D, providing customers with UHPC hollow-out component solutions that combine artistic beauty with structural safety through 58 patented technologies and full-chain service capabilities. In the future, Qinglong will continue to break through technical bottlenecks, promote the application of hollow-out components in more high-end architectural projects, and fulfill its vision of “becoming an outstanding world-leading UHPC/GRC/GRG/GRP manufacturing enterprise”.