The long-term creep performance differences between punch-free threaded rods and chemical anchors primarily manifest in three aspects: material properties, anchoring mechanism, and environmental adaptability. Quantifying these differences requires standardized experimental design and parameter analysis. Punch-free threaded rods are typically made of high-strength alloy steel or stainless steel, and their creep performance is significantly influenced by the metal's crystal structure. Under sustained load, the creep process is dominated by internal dislocation motion and grain boundary sliding within the metal. Initially, creep decelerates, then enters a steady-state phase, and ultimately, microcrack propagation may lead to accelerated creep. The creep behavior of chemical anchors, on the other hand, is closely related to the viscoelasticity of the anchoring adhesive. Under long-term stress, polymer-based colloids undergo molecular chain slippage and crosslink reorganization, resulting in a gradual increase in creep rate over time.
Experimental design is crucial for quantifying these differences. For punch-free threaded rods, full-scale specimens are used to simulate actual installation conditions, and constant tensile load tests are performed to record the deformation over time. The test environment must be strictly controlled for temperature and humidity to eliminate the effects of environmental factors on metal creep. For chemical anchors, holes are drilled into the concrete matrix and the adhesive is injected. After curing, an axial load is applied while the strain distribution at the interface between the adhesive and the matrix is monitored. The loading stress for both specimens is typically set at a specific ratio of the design bearing capacity to ensure the experimental results are relevant for engineering purposes.
Data collection and analysis must combine macroscopic deformation and microstructural observations. The creep curve of punch-free threaded rods can be accurately measured using laser extensometers or strain gauges, focusing on the steady-state creep rate and time to rupture. For chemical anchors, the volumetric shrinkage of the adhesive and crack propagation in the matrix must be monitored simultaneously, and the interfacial bond quality must be analyzed using ultrasonic testing or electron microscopy. Comparing the creep curves of the two anchoring methods reveals that punch-free threaded rods exhibit a lower initial deformation rate, but after long-term service, metal fatigue may lead to abrupt changes. Chemical anchors, on the other hand, exhibit a smoother creep process, but aging of the adhesive may cause a gradual decrease in bearing capacity.
The impact of environmental factors on creep performance needs to be quantified separately. Under low-temperature conditions, the metal lattice mobility of punch-free threaded rods decreases, significantly slowing the creep rate. However, thermal expansion and contraction may lead to a loss of preload. In low-temperature environments, the glass transition temperature of the anchoring adhesive may approach the service temperature, posing a risk of brittle fracture. In high-temperature environments, the opposite occurs: creep of the metal accelerates, and the anchoring adhesive may soften, leading to a decrease in bond strength. Temperature-dependent creep testing can be used to develop a three-dimensional model of temperature, stress, and creep rate, providing a basis for selecting materials for different climates.
Prediction of long-term service performance requires the use of accelerated aging testing. For punch-free threaded rods, accelerated creep testing under high-temperature and high-stress conditions can be used to estimate creep life at room temperature using the time-temperature equivalence principle. For chemical anchors, environmental factors such as UV exposure and moisture cycling must be simulated to assess the durability of the anchoring adhesive. Experimental results show that high-quality chemical anchors exhibit superior long-term load stability compared to standard metal anchors in humid environments. However, under extreme loads, the adhesive creep may cause anchoring force to degrade.
Material optimization is crucial for narrowing performance differences. Surface treatment can be used to reduce the creep rate of punch-free threaded rods. Chemical anchors, on the other hand, require the development of low-creep, highly elastic anchoring adhesive formulations. In practical engineering, punch-free threaded rods are more suitable for high-stress, short-cycle temporary structures, while chemical anchors perform better in permanent structures subject to long-term loads.
Quantifying the differences in the long-term creep performance of punch-free threaded rods and chemical anchors requires a comprehensive understanding of materials science, experimental mechanics, and engineering applications. Through standardized experimental design, coupled analysis of multiple environmental factors, and the accumulation of long-term service data, a scientific selection system can be established, providing a reliable basis for structural safety design.
