T-head rebars (also known as “headed reinforcing bars”) are reinforcing steel bars for concrete structures, that are equipped with a device for mechanical anchorage in one or both ends. The anchorage device (the “head”) often has the shape of a plate, that makes the end look like the letter “T”. Therefore, the term “T-head rebar” is used.
Headed reinforcing bars are used in the same way as common reinforcing bars, with the “head” providing the anchorage of the bar. This type of anchorage is an alternative to anchorage by rebar bends or hooks.
The anchorage capacity provided by the T-head depends on three factors:
- Bearing area of the head
- Stiffness of the head
- Strength of the head-to-bar connection
History of T-head rebar
Anchor plates have been used for anchorage of rods in structures for centuries. The use of the same principle for rebar is a consequence of the development of reinforced concrete. Early examples of headed bars can be found in publications printed more than 100 years ago.
The newer development of headed bars was triggered by more demanding constructions, as offshore concrete structures and the evolution of earthquake engineering that required high structural performance. The use of headed bars in concrete design has created the need for guidelines in the design codes for structural concrete and standardized specifications of the product.
HRC headed reinforcing bars
HRC (Headed Reinforcement Corporation) Europe was a pioneer in the newer development of headed reinforcing bars and has produced headed rebar since 1985. HRC headed bars are characterized by their high performance and consistent high quality.
HRC100 / HRC200 Series T-head rebars are manufactured, under strict quality control to ensure a zero-slip connection between the head and the rebar, that exceeds the actual tensile strength of 500MPa-reinforcement bar acc. EN 1992-1-1, Annex C.
HRC head sizes are designed to transfer the full rebar force into multi-axial stresses in the concrete beneath the head, without crushing the concrete (strength class C30/37 or higher).
Advantages offered by HRC T-head rebars
The ultimate performance of HRC products should be a standard requirement in your design. HRC products give you advantages in structural performance, installation savings and benefits in construction progress and economy.
The concentrated and stiff anchorage properties of HRC-headed bars are not dependent on a certain bond length to develop the full tensile strength of the reinforcement in concrete; 100 % anchorage by the head alone.
Straight anchorage length
Anchorage by hook
Mechanical anchorage: HRC T-head
Improved robustness at overload and accidental conditions
Pictures of situation after test of CIDH pile Supported Footings (University of California, San Diego).
Conventional stirrups: straightened and pushing out the concrete cover leads to loss of rebar anchorage.
Model of test: Left conventional stirrups and T-headed transverse reinforcement to the right.
T-headed transverse reinforcement: cracking of concrete surface only, while rebar anchorage stay intact.