Technology status - Shear Reinforcement

i)Bending-anchorage type shear reinforcement (Stirrup) constructed for shear reinforcement in plate-type concrete members (underground structures such as slabs, foundations, walls, etc.) those have to be satisfied the anchorage requirements presented in KDS 14 20 52 (4.4). This is a typical process that takes a relatively large amount of time and manpower at the construction site as an installation rule that requires to surround the longitudinal bending rebar (for shear reinforcement).

Meanwhile, other shear reinforcement methods that replace Stirrups include ⅱ)Shear-head type , which arranges steel-beams in a grid form, and ⅲ)Enlarged-head type which was newly introduced in Korean Concrete Institute's 2012 revised domestic structural standards.

Bending-anchorage type ‘Stirrup’ ⇛ Enlarged-head type ‘SRD’

As a technology to improve the construction method of shear reinforcement, SRD (Shear Reinforcement of Dual anchorage) shear reinforcement of the enlarged head type that replaces bending-anchorage shear reinforcement (Stirrup) equivalently: Technology certification by the Korea Concrete Institute (2020)

SRD is used for shear reinforcement of plate-type members such as concrete slabs, foundations, and walls, and the shear performance of reinforced concrete members follows the following general formula according to the concrete design code- compressive strength 압축강도 shear reinforcement amount 전단보강량 and placement interval s .


SRD Standards ver 2022
SRD Standards
  SRD13 SRD16 SRD19 note
area (m㎡)
185 290 418 SS275
144 225 324 SM355A
height(max)    · member size − concrete cover(min)
notation    · [ex] SRD13, SRD13@100, 3-SRD13@100
other specifications    · SRDs of different sizes or strengths are specified separately


Bending-anchorage type Stirrup

Bending-anchorage type Stirrup

In order to secure the shear reinforcement performance, Stirrup must firmly surround the upper and lower bending rebar at the same time according to design codes.
However, such reinforcing requirements are by no means a simple task in the construction of plate-type members (slabs, foundations, walls). In addition, this often leads to friction between contractors, supervisors, and design managers in the field on the method of reinforcement work.

Enlarged-head type SRD

Enlarged-head type SRD

The shear reinforcement method using SRD has the advantage of easily installing the SRD through post-installation (or sequential construction) after completing the construction of the upper and lower bending rebars. In addition, SRD has another very advantageous feature in the construction method that, unlike Stirrup, there is no need to surround the upper and lower bending rebars.Due to these characteristics, unlike when constructing Stirrup, shear reinforcing work using SRD greatly shortens the on-site placement process of rebar.

“Shortening process, Reducing costs”

In the reinforced concrete structure process, there is often a need to shorten the work time due to delays in the previous steps. In addition, in the recently changed environment, on-site work processes such as rebar assembly are facing increasing pressure on labor costs.
Therefore, such a solution to reduce labor and construction costs by shortening the work time has become a very important technical interest in design-construction VE.


Comparison of direct construction costs

Based on the standard market price “rebar processing and assembly” steps, the direct construction costs when using co-working Stirrup and when doing post-construction SRD are as follows. According to the existing ‘rebar processing and assembly’ unit-price standard, bending and shear rebar are compared per unit weight (ton). (In this case, shear reinforcement is usually about 10%)

Material cost comparison

In general, when Stirrup is replaced equally with SRD, material costs increase partially. ([ex] Material cost increases by about 12% compared to the existing direct construction cost)

Labor cost comparison

In the case of post-construction with SRD instead of Stirrup, the labor cost of ‘rebar processing and assembly’ is lowered by 1-level from the existing ‘Type-Ⅱ’ to ‘Type-Ⅰ’, and the labor cost is partially reduced. ([ex] Labor costs for the ‘rebar processing and assembly’ process using SRD are reduced by approximately 10% compared to conventional costs)

Process Shortening Effect

In the "rebar processing and assembly" steps, Stirrup (B) must surround the bending rebars (A), so there is an inconvenience in the arrangement that requires two tasks to be constructed simultaneously. This is a typical cause of consuming a lot of field work-time in the rebar assembly.
In contrast, in the' steps using SRD(C), the bending rebar (A) is first placed independently, and then in the subsequent process, the SRD(C) is installed between the placed bending rebars. And then tied, the rebar assembly process is completed.
From the aspect of shortening the construction period, this makes it possible to separate the shear reinforcement process (B) from the main (critical path) and construct it in a subsequent process. Accordingly, the main process work time can be significantly shortened, and a distinct construction period reduction effect can be expected.

공기단축 도표

Performance and Durability

Performance of shear reinforcement : Anchorage Features

The performance of shear reinforcement is ultimately determined by anchorage features. (The examples below show the characteristics of each anchorage type compared through analysis data to evaluate the performance of various types of shear reinforcement.)
Conventional bending anchorage methods such as ‘Stirrup’ correspond to ‘B’, and enlarged head methods such as ‘SRD’ correspond to ‘H’.As shown in the figure, it can be seen that the enlarged head method (H) not only has the best anchorage performance (=tensile force) but also has the smallest slip (=minimizing crack width) compared to the bending anchorage method (B)

성능 내구성

Quotations : R. Beutel, J. Hegger / Germany / Cement & Composiete 24 (2002) 539-549

Durability of structures : Cracks and peeling

『Concrete Structure Standard Design Commentary KDS 14 20 22, 4.11.5 (1)』

~ According to the results of an experimental study (Joint ACI-ASCE Committee 421 1999), the studs with mechanical anchorage that are as close as possible to the top and bottom of the slab effectively resist punching shear. Compared to shear reinforcing bars with hooks at the ends, the enlarged heads of shear studs have less slip, so the shear crack width is relatively small.
The enlarged head method has the advantage of stably maintaining the performance of the structure even after cracking or peeling of the structure due to the characteristic of stably maintaining anchoring performance with little deformation (slip) of the anchoring part.

Main fields of application

· Plate-type concrete members such as flat plate slab, foundation, walls

· Shear reinforcement of concrete structures such as underpasses, subways, and tunnels (entrances and exits)

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