Viktor Sigrist

Tension chord model for structural concrete

Based on a simple tension chord model, problems of cracking, minimum reinforcement, tension stiffening and deformation capacity of structural concrete members are treated in a unified manner. Key f...

HARMONIZED TEST PROCEDURES FOR STEEL FIBER-REINFORCED CONCRETE

A circular slab test method is described as an alternative to modulus of rupture and square slab tests for steel fiber-reinforced concrete. Results of 20 modulus of rupture, 12 square slab, and 24 circular slab tests are compared based on a general theoretical approach that accounts for the random fiber distribution and the successive softening by fiber pullout. Existing requirements for modulus of rupture and square slab tests are reviewed, and harmonized procedures for these as well as the circular slab tests are proposed. It is suggested that an effective flexural tensile strength and a fracture energy parameter be used to characterize the strength and toughness of steel fiber-reinforced concrete. Furthermore, an acceptance criterion is introduced, aimed at excluding materials with drastic softening.

Generalized Stress Field Approach for Analysis of Beams in Shear

This study seeks to further develop stress field and strut-and-tie approaches for the design of structural concrete members. The generalized stress field approach for the analysis of structural concrete beams in shear represents an equilibrium model. Compatibility can be incorporated by specifically limiting the values of the inclination of the stress bands and considering the strain state in determining the effective concrete compressive strength. A total of 113 experimental results from beam and panel tests were compared with calculated data to confirm the accuracy of this approach. This paper also presents a consistent structured procedure. Limit analysis methods can be used for the conception or design of a new structure. The generalized stress field approach should be applied for a more detailed analysis, and calculations based on the cracked membrane model may be conducted for an assessment of a structure.

Reinforced UHPFRC Tension Chords

Summary Ultra high performance fiber reinforced concrete (UHPFRC) has a compressive strength in the range of 200 MPa as well as improved durability properties compared to normal strength concrete. By the addition of short steel fibers the behavior of UHPFRC in compression and tension is affected in a beneficial way. However, for structural applications conventional reinforcement is still required to obtain ductile failures. Although the mechanical properties of UHPFRC have been widely studied, UHPFRC is quite unexplored in practical applications. Therefore, the deformation behavior of UHPFRC tension chords reinforced with conventional as well as high-strength steel has been experimentally examined. In this paper an analytical model is presented which enables the calculation of the cracking and deformation behavior of reinforced UHPFRC elements in tension.

On the Conception of Reinforced UHPC Structural Elements

In recent years, numerous researchers around the world contributed to the development of ultra high performance concrete (UHPC), and first applications in structural engineering demonstrate the potential of this new building material. Most promising in that respect is the use of ultra high performance fiber reinforced concrete (UHPFRC) in combination with steel reinforcement. For this reason, the deformation behavior of UHPFRC tension chords reinforced with different types of steel has been experimentally investigated. In the present paper an analytical model is presented which enables the calculation of the cracking and deformation behavior of reinforced UHPFRC structural elements. Furthermore, with help of a parametrical study failure modes and minimum reinforcement requirements are studied. The overall aim of this research is to develop reliable procedures for the conception and design of structural members made of UHPFRC.