In recent years, the use of natural flax fibres as a reinforcement in composite building structures has witnessed a growing interest amongst research communities due to their green, economical, and capable mechanical properties. Most of the previous investigations on the load-bearing behaviour of concrete components reinforced with natural flax fibres include inorganic impregnations (or even no impregnation) and exclude the use of textile fabrics. Also, the mechanical behaviour of textiles made of natural flax fibres produced as leno fabrics remains to be investigated. In this paper, the results of tensile tests on concrete components reinforced with bio-based impregnated leno fabrics are presented. For comparison, multilayer non-impregnated and impregnated textiles were considered. The results demonstrated that reinforced textiles yielded an increase in the failure loads compared to the concrete cross-sections without reinforcement. The stress-strain diagrams showed that the curves can be divided into three sections, which are typical for reinforced tensile test specimens. For the impregnated textiles, a narrowly distributed crack pattern was observed. The results showed that impregnated textiles tend to support higher failure stresses with less strains than non-impregnated textiles. Moreover, an increase in the reinforcement ratio alongside larger opening widths of the warp yarns enables higher failure loads.

Punching shear-reinforced flat slabs can fail in three modes: (1) inside the shear-reinforced zone, (2) outside the shear-reinforced zone, or (3) at the maximum punching shear capacity. By using the theory of structural systems reliability, this study investigates how these failure modes combined affect the safety level of reinforced concrete flat slabs with punching shear reinforcement, and ultimately, the variation of partial factors. Based on DIN EN 1992-1-1 together with the German National Annex DIN EN 1992-1-1+NA(D), and by using distinct reliability-based methods (i.e., levels II and III), the variation in the system failure probabilities and, consequently, partial factors were analysed. The results indicated that partial factors can fluctuate significantly depending on the governing ultimate limit state function and the scatter of basic variables. Furthermore, they indicated that the chosen reliability-based method had a significant influence on the resulting safety level. The sensitivity analysis confirmed the premise that partial factors can be reduced without compromising socially accepted safety levels (e.g., recommended in DIN EN 1990). Ultimate benefits include material and cost savings and CO₂ emission reductions. Finally, the approach addressed in this paper offers a new perspective on the derivation of partial factors that can be considered by engineering practitioners.

Textile-reinforced concrete has emerged in recent years as a new and valuable construction material. The design of textile-reinforced concrete requires knowledge on the mechanical properties of different textile types as well as their reinforcing behaviour under different loading conditions. Conventional load-bearing tests tend to be complex, time-consuming, costly and can even lack consistent specifications. To mitigate such drawbacks, a standardised tensile test for fibre strands was used to characterise the material properties needed for the design of a textile-reinforced concrete member. The standardised tensile test uses a fibre strand with 160 mm length, which is cut out of a textile grid. For the sake of this study, an epoxy resin-soaked AR-glass reinforcement was considered. The results show that the textile reinforcement has a linear-elastic behaviour, and the ultimate tensile strength can be statistically modelled by a Gumbel distribution. Furthermore, the results indicate that the modulus of elasticity is not influenced by the length or the number of fibre strands. Therefore, the mean value attained from the standardised test can be used for design purposes. These findings are essential to derive an appropriate partial safety factor for the calculation of the design values of the tensile strength and can be used to determine the failure probability of textile-reinforced concrete members.

To tackle the emergencies of climate change, Germany has pledged to become greenhouse gas neutral by 2045. In the context of such commitment, the German Committee for Structural Concrete (DAfStb) – a German expert body for structural concrete – has been developing a technical guideline, which proposes a set of annual reduction targets (by means of reduction classes) for limiting the embodied greenhouse gas emissions of structural systems. Previous research work suggests that opportunities for the mitigation of greenhouse gas emissions are higher during early design stages. However, the complexity that is typically involved in early decisions means that designing for reduced, or even minimal, emissions without loss of structural performance remains challenging for design practices. While the introduction of emission reduction targets for structural systems is a positive initiative for the promotion of more sustainable concrete construction, it might bring new and unexpected impacts for design practices. In this paper, the introduction of the emission reduction targets proposed in the new DAfStb guideline are investigated and their implications to practitioners are discussed. To this, two commonly-designed floor slab systems are evaluated in the context of a typical office/ residential multi-storey building by varying the design approach as well as the span width, loading conditions, concrete strength classes and cement compositions. The findings suggest that the combination of CO₂-efficient cements with optimised design approaches offers the largest potential for emissions savings and enables longer target-compliant spans widths. Nonetheless, from 2030 onwards, the use of more conventional slab systems, as cast-in-situ slabs, for long span widths might become challenging. While reframing conventional practices might be required, opportunities for the introduction of innovative materials and solutions might emerge.