Shear design of ultra-high-performance fiber-reinforced concrete girders

In [1], an approach for verifying the shear resistance of ultra-high-performance concrete (UHPC) girders is presented. This approach follows Eurocode 2 and the German DAfStb Guideline on „Steel Fiber Reinforced Concrete“. It superimposes the shear resistance of a member without shear reinforcement, the shear resistance provided by stirrups, and the contribution of the fibers in the shear crack. Regarding the latter, the approach differentiates between members with I-shaped and compact cross-section because crack formation and failure mode differ significantly for the two types of cross-section. Consequently, the efficiency of the fibers in terms of shear resistance is mathematically doubled for members with I-shaped cross-section compared to the current approach described in the DAfStb Guideline on „Steel Fiber Reinforced Concrete“. This allows for a more economical design of such members. In contrast, a further reduction of the efficiency of the fibers is required for members with compact cross-section.

In [2], the proposed design approach is validated by means of a shear database. When compiling the database, the compressive strengths and post-cracking tensile strengths from the literature had to be critically reviewed and converted with respect to the specimen size and test method. The model reliability was statistically analyzed for various specimen configurations and model parameters. It was found that shear slenderness and post-cracking tensile strength influence the model safety the most, while the other parameters showed only a minor effect. For 133 tests on beams with I-shaped cross-section, the mean value of the model safety is X̅ = 1.48 and the 5 % quantile is Q0.05 = 0.94. For 75 tests on beams with compact cross-section, the results are X̅ = 1.59 and Q0.05 = 0.94. For all 208 tests included in the database, X̅ = 1.52 and Q0,05 = 0.94 are obtained.

[1] Metje, K.; Leutbecher, T., 2022. Zur Querkraftbemessung von Biegeträgern aus stahlfaserverstärktem ultrahochfesten Beton – Teil 1: Bemessungsansatz und Datenbank. Bauingenieur 97(3): 83-90.
[2] Metje, K.; Leutbecher, T., 2023. Verification of the shear resistance of UHPFRC beams – Design method for the German DAfStb Guideline and database evaluation. Engineering Structures 277:115439.

Related articles:

Issue 05/2024

Flexural design of ultra-high-performance fiber-reinforced concrete girders

In [1], an approach for determining the moment resistance of ultra-high-performance concrete (UHPC) girders with mixed reinforcement is presented. This approach considers the contribution of the steel...

Issue 09/2010 Overview of the Test Results

Innovative Precast Girders of Fiber and High-Performance Concretes

The stationary production processes offer precast construction optimal possibilities for applying high-performance concretes, for which remarkable developments have taken place (Fig. 1)....

Issue 02/2021

Punching shear behavior of steel fiber reinforced flat slabs in combination with punching shear reinforcement

The guideline “Steel Fibre Reinforced Concrete” published by the German Committee for Reinforced Concrete (DAfStb) in 2012 regulates the punching shear design of steel fiber reinforced flat slabs...

Issue 02/2014 Increasing the bearing capacity in the vicinity of integrated service lines

Effectiveness of lattice girders –

Use of lattice girders in reinforced-concrete floor plates is a widely practiced method of construction for conventional high-rise building structures. An estimated 70?% of all floors in these...

Issue 02/2015 Market potential in bridge infrastructure

Use of carbon-reinforced shotcrete to increase the shear resistance of prestressed-concrete girders

The German highway network includes over 39,000 bridges with a total length of almost 2,100 km. Most of these bridges were built from prestressed concrete in the period from 1965 to 1985 (Fig. 1)....