Influence of fiber orientation and structural-integrity reinforcement on the flexural behavior of elevated slabs

Hybrid reinforced technology (combination of steel reinforcing bars and fibers) can be considered as a competitive alternative to the already existing solutions for the construction of column-supported flat slabs. Constructed hybridreinforced buildings prove that hybrid solutions have sufficient bearing capacity to maintain structural integrity despite being exposed to high stress levels, thereby providing a beneficial solution in terms of toughness, ductility, and sustainability performance. However, the lack of design-oriented recommendations based on the accepted limit state format for dealing with both serviceability and ultimate limit states slows down the wider implementation of this technology. Considering the above-mentioned, this article presents a simplified design-oriented method that covers the evaluation of the structural response of hybrid reinforced concrete column-supported flat slabs in terms of flexural strength, cracking, and instantaneous deformations. Two hybrid reinforced alternatives for a given flat slab are studied by means of the proposed approach. Furthermore, a nonlinear finite element analysis is carried out in order to evaluate the effectiveness of the developed simplified method. Based on the achieved results, its suitable accuracy and precision can be pointed out. This outcome may motivate current practitioners to consider hybrid reinforced concrete solutions as a possible alternative during the design of residential and office buildings.

Section: Flexural Strength Of Hrc: Sectional Modelmentioning

confidence: 99%

A limit state design approach for hybrid reinforced concrete column‐supported flat slabs

Aidarov

Tošić

Antequera

2022

“…[22][23][24] However, several studies evidenced that the use of the constitutive models obtained from small-scale characterization beams might have led to inaccurate and unsafe design for SFRC slabs. 1,7,25,26 One of the main reasons behind this phenomenon is a more favorable fiber orientation along the main (longitudinal) direction of the small-scale beams in comparison with large-scale structures. [26][27][28][29][30] In this regard, the fib Model Code 2010 22 and Annex L to the new Eurocode 2 31 propose an orientation factor (K, in accordance with Clause 5.6.7 of the fib Model Code 2010 22 ) that reduces/ increases the serviceability and ultimate residual tensile strength of the FRC element once unfavorable/favorable fiber orientation is experimentally verified.…”

Section: Introductionmentioning

confidence: 99%

Influence of fiber orientation on flexural‐based design of steel fiber‐reinforced concrete slabs: Experimental and numerical program

Aidarov,

Nogales,

Tošić

et al. 2024

Steel fiber‐reinforced concrete (SFRC) has proven to be a suitable structural material for constructing elevated flat slabs, and several existing office and residential buildings, in which SFRC was used for these components, highlighted the positive outcomes from both technical and sustainability perspectives. However, research on the influence of fiber orientation on the flexural performance of SFRC slabs is relatively scarce despite the fact that a number of studies revealed that the use of constitutive models derived from three‐point bending tests on notched beams leads to overestimations of the bearing capacity of statically indeterminate slabs. In this context, this study aims at presenting an extensive experimental program that consisted of testing three SFRC slabs (3.0 × 3.0 × 0.1 m3) subjected to point load under a statically indeterminate test configuration. The testing procedure was followed by the extraction of 88 cores in order to analyze both fiber distribution and orientation by means of a non‐destructive inductive method. The results indicate that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the 150 × 150 × 600 mm3 notched reference beams tested to characterize the pre‐ and post‐cracking flexural performance of the SFRC produced. Based on these results, a straightforward design‐oriented approach to compute an orientation factor was proposed and considered to develop the constitutive law used to simulate the structural response of SFRC slabs by means of nonlinear finite element model. The numerical simulation results showed a good agreement with the experimental response, this evidencing that the orientation factor may permit to account for the differences caused by geometric and statistical scale‐induced factors between both the beams used for the SFRC flexural properties characterization and slabs produced with the same SFRC.

“…This approach has been suggested also in the new generation of Eurocodes, which includes a new annex (Annex L) explicitly devoted to the design of SFRC structural elements. 4 Although some studies are available in the literature on the constitutive relationship of the material, [5][6][7][8][9][10] on the structural behavior of elevated slabs and beams, [11][12][13][14][15][16] and on their design approach, [17][18][19] the present work aims to shed some new lights through a comprehensive experimental campaign on SFRC beams and slabs, with or without ordinary reinforcement. Special attention is devoted to the reliability of building codes requirements to predict both the load-bearing capacity and the behavior in service conditions, with the aim of comparing the ductility supplied by high dosages of steel fibers, or low dosages used in combination with conventional reinforcement.…”

Section: Introductionmentioning

confidence: 99%

The basis for ductility evaluation in SFRC structures in MC2020: An investigation on slabs and shallow beams

Colombo

Conforti

Prisco

et al. 2023

Self Cite

The paper presents a synthesis of an extensive experimental campaign on linear and two‐dimensional steel fiber reinforced concrete (SFRC) structural elements carried out to check the ductility requirements aimed at guaranteeing limit analysis approaches for the computation of ultimate load‐bearing capacity of SFRC structures; special attention is devoted to the role of the degree of redundancy of the structure. In particular, full‐scale shallow beams and slabs reinforced with steel fibers (with or without conventional longitudinal reinforcement) were tested in two different laboratories: the Politecnico di Milano (PoliMI) and the University of Brescia (UniBS). In this experimental campaign, two different fiber contents and fiber types were considered. The experimental investigation, carried out within the activities to support Annex L of Eurocode 2, was fundamental also for developing the design rules included in the fib Model Code 2020 and allowed to formulate conclusions regarding optimization of the mix design, ductility, and design prediction at the ultimate capacity.