Properties of reinforced concrete, such as crack width, crack spacing, and reinforcement strain, are measured using specific techniques to evaluate performance and structural integrity.
Evaluating the behavior of reinforced concrete elements involves measuring several key properties under load or environmental conditions. These measurements are crucial for understanding structural performance, predicting service life, and validating design models.
Key Reinforced Concrete Measurements and Techniques
Different properties require distinct measurement methods. Based on experimental and analytical studies, common measurements include evaluating cracks and strains within the material.
Measuring Cracks
Crack width and cracks spacing are critical indicators of a concrete structure's serviceability and durability. Excessive crack widths can allow ingress of deleterious substances, leading to reinforcement corrosion.
- Digital Image Correlation (DIC): As highlighted in experimental studies, crack width and cracks spacing are specifically measured using the digital image correlation technique. DIC is an optical method that employs cameras to capture images of the concrete surface before and during loading. By tracking the displacement of speckles or patterns applied to the surface, precise measurements of deformation, including crack opening and propagation, can be determined across a large area.
Measuring Reinforcement Strain
The behavior of the steel reinforcement within the concrete is fundamental to understanding the composite material's performance. Strain in the reinforcement indicates how much the steel is stretching or compressing under load.
- Embedded Electric Strain Gauges: Strain in the main reinforcement is measured using embedded electric strain gauges. These small, sensitive devices are attached directly to the steel bars before casting the concrete. As the steel deforms under load, the electrical resistance of the gauge changes, which is then converted into a strain value. This provides a direct measure of the internal forces and stresses carried by the reinforcement.
Considering Cover
While not a measurement technique explicitly detailed in the provided reference snippet, the cover to the main reinforcement is a crucial design parameter that is also considered and scaled, often measured as a distance. Concrete cover is the depth of concrete between the outer surface of the reinforcement and the concrete surface. Adequate cover protects the steel from corrosion and provides fire resistance. Its measurement typically involves rulers, calipers, or specialized cover meters (pachometers) in existing structures. In experimental setups or construction, it's a specified and controlled dimension.
Here's a summary of the measurement methods based on the reference:
| Property Measured | Measurement Technique Used |
|---|---|
| Crack Width | Digital Image Correlation (DIC) |
| Crack Spacing | Digital Image Correlation (DIC) |
| Strain in Reinforcement | Embedded Electric Strain Gauges |
| Cover to Reinforcement | Scaled/Considered (Measurement method not specified in reference snippet, but it's a measured distance) |
These techniques provide valuable data for researchers and engineers to assess the performance and safety of reinforced concrete structures.
