How Does Strength Testing of Double-Curved GRC Panels Differ from Flat Panels? Analysis of Testing Differences and Standard Specifications

Due to complex biaxial curved-surface loading and uneven stress distribution, double-curved GRC panels differ significantly from flat panels in strength testing methods, indicator requirements, and equipment selection. Drawing on national and industry standards as well as testing experience from double-curved projects, Qinglong explains the core differences in strength testing and practical specifications.

1. Different Requirements for Test Specimen Preparation

Test specimens must accurately replicate the loading state and curved-surface characteristics of double-curved components. Specimen shape and dimensions: double-curved GRC panels require curved specimens with the same curvature as the actual components; specimen dimensions must include a complete curved-surface unit, with recommended dimensions of 1000mm×500mm (arc length × width) to ensure test results reflect actual conditions; flat panel specimens are standard rectangles (1000mm×500mm×thickness) with no need to consider curvature effects. Specimen quantity: due to the high complexity of curved surfaces, the number of double-curved GRC panel specimens must be increased to 6 per group, while 3 per group is sufficient for flat panels; in the Guangxi New Media Center project, Qinglong ensured result reliability through testing multiple specimen groups. Preparation process: double-curved specimens must be prepared using the same molds and production processes as the actual components, ensuring consistent fiberglass mesh distribution and slurry compaction with the actual components; flat panel specimens can be batch-produced using standard molds.

2. Core Differences in Testing Methods and Equipment

Testing methods and specialized equipment adapted to double-curved surfaces must be adopted. Flexural strength testing: flat panels use the four-point bending test method with linear support points; double-curved GRC panels require the arc-supported four-point bending method, where support points fit closely against the specimen's curved surface to avoid localized stress concentration during testing—Qinglong uses custom arc support devices to ensure testing accuracy. Testing equipment: double-curved testing requires a universal testing machine with adjustable support spacing and angles to accommodate specimens of different curvatures; a conventional universal testing machine is sufficient for flat panel testing. Additional test items: double-curved GRC panels require additional curved-surface compressive strength testing and shear strength testing to simulate surface compression and shear loading at joint areas in actual use; flat panels mainly test flexural strength and tensile strength, with no need for additional curved-surface-specific tests.

3. Differences in Test Indicators and Evaluation Criteria

Double-curved GRC panel test indicators are stricter, taking into account the effects of uneven stress distribution on curved surfaces. Strength indicator requirements: the pass standard for flexural strength of double-curved GRC panels is ≥18MPa, 20% higher than that of flat panels (≥15MPa); shear strength must be ≥2.5MPa, while flat panels have no mandatory shear strength requirement. Stress distribution evaluation: double-curved specimen testing requires recording stress values at different locations, ensuring the difference between maximum stress and average stress is ≤15% to avoid localized strength deficiency; flat panels only require evaluation of the average strength value. Failure determination: if one double-curved specimen fails, sampling must be doubled for retesting, while flat panels allow one failure, with a retest pass being sufficient—Qinglong strictly follows this standard to ensure the overall strength of double-curved components meets requirements.

4. Application of Test Results and Practical Significance

Differentiated testing ensures the safe use of double-curved GRC panels and guides production optimization. Application of results: double-curved test results are directly used to adjust production processes, such as optimizing joint node design through shear strength testing and adjusting the number of fiberglass mesh layers through flexural strength testing; flat panel test results are mainly used for material performance verification. Practical case: in the Hainan Poly Peninsula No. 1 double-curved project, Qinglong's specialized strength testing identified a batch of specimens with substandard flexural strength, prompting timely adjustment of the slurry formula and fiberglass mesh laying process to ensure the final components' strength met design requirements. Industry significance: strict implementation of differentiated testing standards can effectively prevent insufficient strength in double-curved components caused by testing against flat panel standards, reducing the risk of cracking and deformation during use and safeguarding building structural safety.