Cracked and uncracked concrete – basic information

In a nutshell, idea of reinforced concrete structure relies on cooperation of two materials – concrete and steel (reinforcement). Building elements are designed in order to utilise the best properties of mentioned materials. It allows to identify following areas:

• tension zone (cracked concrete – utilisation of tensile strength of reinforcement);
• compression zone (uncracked concrete – utilisation of compressive strength of concrete).

Tension zone (cracked concrete) should not be equate with structural damage. The occurrence of this area is intended and intentional. Quantity and layout of reinforcement are designed in order to strict control of cracks width (usually at the level of w_max = 0,3 mm).

Typical elements of reinforced concrete structures are shown below, with cracked concrete zone marked, as well as simplified static scheme and bending moment diagram.

Figure 1. Simply supported beam e.g. ceiling element

Figure 2. Cantilever e.g. balcony slab

Figure 3. Continuous beam e.g. bridge structure element

Figure 4. Closed frame e.g. tunnel construction

In practice, the issue can be more complicated. Complex structural systems with different load variants creates stress map for whole building. Analysis of this topic is a duty and responsibility of structural designer. He should define what type of concrete should be considered in fastenings calculations for selected area.

Concrete module of EasyFix software allows to take into account type of concrete. In general, cracked concrete area is more demanding, so the performance data of fasteners are reduced accordingly. User decides if counting process would be performed for cracked or uncracked concrete. The option can be found in Substrate tab. Depend on the choice, different range of the products is available.

Figure 5. Concrete type selection in EasyFix, Concrete module

In cracked concrete zone, following anchors can be successfully used: throughbolts R-HPTII-ZF/A4, R-HPTIII-ZP/A4, concrete screws R-HLX or bonded anchors: epoxy resin R-KEXII or hybrid resin R-KERII. Additionally, for uncracked concrete zone reliable will be throughbolts R-XPT, R-XPT-II-A4, R-XPTIII-HD as well as bonded anchor polyester resin R-KEMII.

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