Steel Fibre Reinforced Self-compacting Concrete Research Articles

Behavior of Exterior Beam-Column Joints Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) Against Cyclic Lateral Loads

Behavior of Exterior Beam-Column Joints Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) Against Cyclic Lateral Loads

Investigation of optimized machine learning models with PSO for forecasting the shear capacity of steel fiber-reinforced SCC beams with/out stirrups

This article presents a comprehensive investigation of the applicability of optimized machine learning (ML) models with particle swarm optimization (PSO) for forecasting the shear strength of steel fiber-reinforced self-compacting concrete (SFR-SCC) beams with/without stirrups in engineering applications. Firstly, a database containing the results of 101 specimens with nine input features is adopted to train the models. As ML models such as random forest (RF), adaptive boosting regression (AdaBoost), extreme gradient boosting (XGBoost), support vector regression (SVR), and K-nearest neighbors regression (KNN) are considered, whereas the hyper-parameters of these models are set as default by the sklearn module. On the other hand, PSO-ML models (PSO-RF, PSO-AdaBoost, PSO-XGBoost, PSO-SVR, and PSO–KNN) are constructed using particle swarm optimization to find the optimal combination of the hyper-parameters of these default ML models. Afterwards, the forecasting ability of each model is extensively assessed using various performance metrics, error analysis, and score analysis, and the model with the best forecasting ability is determined and compared with existing empirical models. Moreover, Shapley additive explanation (SHAP) analysis is also utilized to ensure the interpretability of the forecasting models and to overcome the “black box” problem of ML methods. Lastly, based on the best forecasting model developed in this study, a graphical user interface (GUI) has been developed to easily forecast the shear strength of SFR-SCC beams in practical applications. The results of the study clearly illustrate that PSO-ML models exhibit better forecasting capabilities than default models. It can be emphasized from here that the PSO algorithm can be an effective tool to improve the performance of ML models. It should also be pointed out that the use of PSO in simpler algorithms instead of tree-based models can further improve forecasting efficiency. On the other hand, the PSO-RF model has the best performance, with a lower error value and a high final score. And this makes it a more reliable option for predicting the shear strength of the SFR-SCC beams compared to empirical equations. In addition, according to the results of SHAP feature importance analysis, the most important input parameters affecting the shear strength of SFR-SCC beams are stirrup rebar ratio (ρv), stirrup yield strength (fyv) and longitudinal rebar ratio (ρt). This information can assist engineers in paying special attention to these features in their design and assessment processes.

Comparative Study on the Mechanical Properties of Steel Fiber Reinforced Self-Compacting Concrete

Self-compacting concrete (SCC) is a flowable concrete which can consolidate under its own weight without the need of external vibration. The highly fluid nature of SCC makes it suitable for placing in difficult environments like congested reinforcement and thinner sections. Use of SCC can also help in decreasing noise pollution at worksites which is caused by vibration of concrete. SCC is used in bridges, buildings, and tunnel construction. The addition of small closely spaced and uniformly dispersed fibres to concrete would act as a crack resistor and would substantially improve its properties. This type of concrete is known as fibre reinforced concrete. In fact, the fibre reinforcement mechanisms can convert the brittle behaviour of this cement-based material into a pseudo-ductile behaviour up to a crack width that is acceptable under the structural design point-of-view. Fibre addition, however, increases the complexity of the mix design process, due to the strong perturbation effect that steel fibres cause on fresh concrete flow. In the present study, the effect of steel fibres on fresh and hardened properties are studied by adding steel fibres of different percentages such as 0%, 1% and 2% for M70 grade of concrete. An experimental investigation has been carried out to determine different properties like workability and strength of Fiber Reinforced Self Compact Concrete and Self- Compacting Concrete (SCC). For testing the properties of SCC and Fiber Reinforced SCC (FRSCC) in fresh state slump-flow, T50 Test, L-box, U-box, and V-funnel tests were conducted. Whereas for testing the properties in hardened state compressive strength, split tensile strength and flexural strengths are carried out. Detailed studies have revealed that the Steel Fiber Reinforced Self Compacting Concrete made with the Steel fibres displays a better performance. The investigations and results are presented from the study. Index Terms: Self compacting concrete, Steel fibre reinforced concrete, Super plasticizer, Silica fume, Fly ash, Steel fibre.

Impact resistance of macro and micro steel fibre reinforced self-compacted concrete (SFRSCC) with modelling and reliability analysis

Adding steel fibres can transform the brittle characteristic of concrete into a ductile state. The objective of the current study is to test the impact resistance of macro and micro steel fibre-reinforced self-compacting concrete (SFRSCC) experimentally by applying a simulated drop-weight impact, as well as statistically and through reliability studies. Cube specimens were used for the experiment. The inclusion of macro and micro steel fibre greatly increased the concrete mixture’s impact resistance. It is observed that the volume fraction of 0.75 and 0.50% of macro and micro steel fibre has improved impact resistance with an increase in the percentage of energy absorption of 216.21 and 240.53%, respectively. All the concrete samples exhibited the same failure pattern. Using Response Surface Methodology, the impact resistance of SFRSCC mixtures can be accurately predicted. The first and failure cracks (N1 and N2) follow a two-parameter Weibull distribution function of drop-weight impact test.

Effect of water re-curing on the physico-mechanical and microstructural properties of self-compacting concrete reinforced with steel fibers after exposure to high temperatures

The present work aims to investigate the influence of water re-curing- on the physico-mechanical properties and the microstructural of heat-damaged steel fiber-reinforced self-compacting concrete. The experimental approach involves subjecting self-compacting concrete specimens, with and without steel fiber reinforcement, to various high temperatures (400, 600, and 800 °C), with a heating rate of 5 °C/minute. After cooling to ambient temperature, these samples were subjected to water re-curing for 30 days. Non-destructive measurement techniques, such as those of the ultrasonic pulse velocity and dynamic modulus of elasticity, and destructive measurement techniques, such as those of the flexural strength and compressive strength, were performed to assess the level of thermal damage caused to specimens as well as the degree of recovery. Moreover, scanning electron microscope (SEM) analyses were also performed to examine the morphological changes that occurred in concrete and at the fiber/concrete interface. The results obtained showed that the water re-curing process has remarkable effects on the recovery of the microstructure of thermally damaged specimens and its physical and mechanical properties as well. The recovery rate was more important for temperatures above 400 °C. Furthermore, it was found that self-compacting concretes reinforced with steel fibers recurred after exposure to 400 °C and 600 °C exhibited better behavior than self-compacting concrete without fibers, particularly in terms of mechanical resistance.

Prediction of the complete flexural load–deflection curve of self-compacting concrete reinforced with hook-end steel fiber

The flexural performance is vital for evaluating the characteristics of steel fiber reinforced self-compacting concrete (SFR-SCC). Although the tested load–deflection curve is commonly used to predict the flexural performance, little research has been done on the tested curve prediction. In this study, the complete flexural load–deflection curves of SFR-SCC beam specimens were obtained by a four-point bending test. The hook-end steel fiber with a length about 25 mm, 30 mm or 35 mm was respectively added for SFR-SCC at volume fraction of 0.4 %, 0.8 %, 1.2 % or 1.4 %. The characteristic points of tested curves are statistically analyzed to build the prediction formulas for the initial cracking strength, the flexural strength, and the first and second residual flexural strengths. The formulas for predicting the complete flexural load–deflection curve of SFR-SCC are proposed, and verified by comparing with the test curves. Meanwhile, the distribution of steel fiber in concrete matrix of beam specimen was measured to explain the mechanisms of flexural performance of SFR-SCC.

Study on the impact resistance of steel fiber-reinforced self-compacting concrete after high temperature

The present study explored the dynamic mechanical properties of steel fiber-reinforced self-compacting concrete (SFRSCC) after a high temperature. The impact test was conducted using a φ80 mm split Hopkinson pressure bar (SHPB) device, with a focus on the factors of influence and the regularity of steel fiber content (0.5 %, 1.0 %, and 1.5 %), impact strain rate (55 s−1, 90 s−1, and 140 s−1), and temperature (20 °C, 300 °C, 600 °C, and 900 °C) on the failure form, dynamic strength, impact toughness, and dynamic increase factor (DIF-σ) of SFRSCC after high-temperature exposure, and the mechanism analysis based on the results of the SEM examination. The impact test results revealed the following: (1) With the increase in the steel fiber (SF) content, the dynamic strength (fp) of the SFRSCC exhibited a further evident growth trend after high temperature compared to that at normal temperature reaching 105 % and the toughness index also increased by more than 20 %. (2) While the effect of SF content on DIF-σ of SFRSCC was not significant under normal temperature conditions after high-temperature exposure, the DIF of SFRSCC can increase by over 40 % with the increase of SF content. In addition, the strain rate effect was also further significant, and the DIF-σ can increased by about 30 % after high-temperature treatment compared to normal temperature. (3) A prediction formula was proposed for DIF-σ of SFRSCC after high temperature, and the results were in good agreement with the results of the impact test. This prediction formula can better provide theoretical data support for disaster prevention and reduction in subsequent projects. The findings of the present study would serve as a valuable reference for subsequent research on the impact resistance of SFRSCC after high-temperature exposure.

Impact resistance of micro and macro crimped steel fibre reinforced self-compacting concrete with SCM

This paper aims to investigate the impact resistance of micro and macro crimped steel fibre-reinforced self-compacting concrete (SFRSCC) with the volume fractions of 0.25%, 0.50%, and 0.75%. A total of seven mixtures were investigated with different volume fractions of steel fibres considering in terms of fresh, mechanical properties and impact resistance. The total binder contains 60% cement and 40% supplementary cementitious materials (SCM) with a combination of 30% fly ash and 10% silica fume. The addition of steel fibre decreases the workability of SCC. However, the inclusion of SCM compensates and increases its workability. Mechanical behaviour of micro and macro steel fibre reinforced SCC outperforms the conventional SCC in terms of compressive strength, split tensile strength and flexural strength. The impact resistance of SFRSCC is determined through a modified testing procedure derived from the guidelines provided by ACI 544.2 R. It is observed that the volume fraction of both 0.75% micro and macro steel fibre has improved impact resistance with increase percentage of energy absorption of 180% and 240%. The relationship between UPV and impact test results found that the number of blows can be predicted using the UPV values from the regression equations. The results of the Weibull distribution (WD) and reliability analysis indicate that 80% (τ = 0.8) of the SFRSCC samples are reliable enough to survive 14 blows at first crack and 20 blows at failure crack. The incorporation of crimped steel fibres into the concrete matrix led to the even distribution of impact loading throughout the concrete specimen with the help of steel fibres, thereby improving the impact resistance of SCC.

Effect of fibre diameter and tensile strength on the mechanical, fracture, and fibre distribution properties of eco-friendly high-strength self-compacting concrete

The development of Steel Fibre-Reinforced Self-Compacting Concrete (SFR-SCC) is a complex task with significant practical implications for the construction industry. However, the absence of established design guidelines and recommendations, and the limited availability of design methodologies, present a significant challenge. Achieving the targeted rheological and mechanical properties while simultaneously minimising production costs requires a comprehensive understanding of the optimal blend of fibre type and quantity and the coarse aggregate content. This paper addresses the impact of steel fibre properties on the rheological and fundamental mechanical properties of eco-friendly high-strength self-compacting concrete (HSSCC), using 40% ground granulated blast furnace slag (GGBS) as a cement replacement. The research focused on 30 mm long hooked-end steel fibres with tensile strengths of 1345 MPa and 3070 MPa, and diameters of 0.55 mm and 0.38 mm, respectively. In addition, the study investigated the combined effect of coarse aggregate content and steel fibre type on the performance of eco-friendly HSSCC. The fresh properties of eco-friendly HSSCC were assessed using the slump flow and J-ring tests. Furthermore, mechanical and fracture properties such as compressive strength, splitting tensile strength, elastic modulus, four-point flexural strength, and three-point flexural strength on notched prisms were also evaluated. The distribution and alignment of steel fibres in the HSSCC were assessed using image analysis techniques, which showed that the steel fibre diameters were a crucial factor in the fibre dispersion. The results demonstrated that using steel fibres with higher tensile strength and smaller diameter significantly enhanced the splitting tensile strength, flexural strength, and fracture energy, compared to steel fibres with larger diameters and lower tensile strengths. Additionally, the study indicated that the elastic modulus and fracture energy of eco-friendly HSSCC reinforced with both types of steel fibre are highly dependent on the content of coarse aggregate used. The study highlighted that the coarse aggregate proportion and the steel fibre characteristics were two vital factors that influenced the rheological and mechanical properties of HSSCC and must be considered during the mix design process to optimise the desired properties while also minimising production costs.

Experimental Study of Dynamic Tensile Strength of Steel-Fiber-Reinforced Self-Compacting Concrete Using Modified Hopkinson Bar.

As a typical brittle material, the tensile strength of concrete is much lower than its compressive strength. The main failure mode of concrete buildings under explosive and impact loading is spalling, so it is crucial to understand the dynamic tensile performance of concrete. This paper presents an experimental study on the dynamic tensile strength of steel-fiber-reinforced self-compacting concrete (SFRSCC). Specimens of two different self-compacting concrete (SCC) mixes (C40 and C60) and four different fiber volume fractions (0.5%, 1.0%, 1.5%, and 2.0%) are fabricated. Dynamic tensile strengths of SFRSCC are obtained using a modified Hopkinson bar system. The relationships between the dynamic tensile strength of the corresponding SCC mix, the quasi-static compressive strength, and the fiber volume fraction are discussed. An empirical equation is proposed. It is shown that SFRSCC with high compressive strength has higher dynamic tensile strength than low-strength SFRSCC for the same fiber content, and the dynamic tensile strength of SFRSCC possesses an approximately linear relation with the fiber volume fraction. The mechanism underlying this fiber-reinforcement effect is investigated.

Retrofitting of post-heated R.C. columns using steel fiber reinforced self-compacting concrete jackets

This work aims to examine the effectiveness of using steel fiber-reinforced self-compacting concrete (SFRSCC) jackets in retrofitting RC columns subjected to high temperatures. In order to do that, eleven RC columns were cast and tested under axial loading. One column served as an unheated control column, and ten columns were heated to 400 °C and 600 °C for two hours. Subsequently, eight columns were retrofitted using SFRSCC jackets. The volume fraction of steel fibers and the thickness of the SFRSCC jackets were the main parameters considered for the retrofitting technique. According to the experimental findings, SFRSCC jackets can significantly enhance the structural performance of post-heated columns as evaluated by failure load, stiffness, and toughness. The percentage increase in the failure load, stiffness, and toughness of retrofitted post-heated columns is greatly impacted by the thickness of the SFRSCC jackets. The retrofitted columns with 25 mm and 50 mm SFRSCC jackets increased their failure load by 63.9% and 211.8%, respectively, relative to that of the heated control column at 600 °C. It is obvious that the failure load of the retrofitted columns was not significantly impacted by increasing the volume fraction of steel fiber in the SFRSCC jackets. Finally, a proposed design equation was suggested to predict the failure load of retrofitted post-heated columns with SFRSCC jackets.

Electrical conductivity and heating performance of hybrid steel fiber-reinforced SCC: The role of high-volume fiber and micro fiber length

Recently, it has become very popular to develop electrically conductive concrete composites for active deicing and snow-melting of transportation infrastructure. These composites should have stable electrical conductivity and a uniform heating performance, as well as high mechanical and durability properties, for a sustainable solution. In this context, the main motivation of this study is to develop an electrically conductive hybrid steel fiber reinforced self-compacting concrete (HSFR-SCC) composite for ice and snow removal applications. The electrical conductivity and heating performance of self-compacting concrete (SCC) mixtures having different fiber volumes (1.00, 1.25, and 1.50%) and the combination of macro steel fiber with micro steel fibers having lengths of 13 and 6 mm as single and hybrid were experimentally investigated for the first time. For this purpose, a total of ten SCC mixtures were designed, one of which was non-fiber Control, the others had steel fiber volumes of 1.00, 1.25, and 1.50% and different fiber combinations. Workability (slump-flow, T500 and J-ring) tests on HSFR-SCC mixtures were performed with reference to EFNARC. Then, mechanical (compressive and flexural strengths), electrical resistivity, and heating performance tests of 90-day HSFR-SCC samples were carried out. Before the electrical resistivity and heating performance tests, HSFR-SCC samples were kept in an oven at 105 ± 5 °C for 24 h to measure their most critical state (dry) performance. Moreover, using multiple linear regression analysis, empirical equations and contour plots were developed to predict the electrical resistivity and temperature increase values of HSFR-SCC samples depending on fiber volumes and combinations. Considering the experimental results, electrically conductive HSFR-SCC mixtures with satisfactory workability and high strength were obtained. The addition of various volumes and combinations of steel fiber to SCC significantly improved the electrical conductivity and heating performance of the concrete, while the mixtures with hybrid fiber were the best for all fiber volumes. As for the different micro fibers added to the HSFR-SCC mixtures, the 13 mm length micro steel fiber was much more effective in improving the electrical resistivity and heating performance of the samples compared to the 6 mm length micro steel fiber. Also, it was found that the fiber-reinforced index of electrically conductive HSFR-SCC samples could be 0.87 for effective and efficient electrical conductivity.

A robust mix design method for steel fiber reinforced self-compacting concrete

The lack of robustness in the production of steel-fiber-reinforced self-compacting concrete (SFRSCC) can lead to unsatisfactory performance. The research aimed to develop an approach for assessing and designing the robustness of SFRSCC proportions. To achieve this, a semi-empirical workability framework was proposed, and slump flow tests were conducted for framework's parameter calibration and accuracy validation. Subsequently, the derived self-compacting zone (SCZ) from the framework was utilized as the robustness indicator, and further investigated its evolution law. The derivation indicated that the framework allowed for the quantification of component proportion based on film thickness and aggregate characteristics, as well as the workability configuration through film thickness and rheology, linking the workability and mix proportions of SFRSCC. Experiments results revealed negative correlations between interparticle and fiber-aggregate contacts with increasing film thickness, while the increasing fiber dosage enlarged inter-contact. The further contact calibration in the framework enabled precise delineation of the self-flow boundary, but the reliability of segregation boundaries decreased due to mortar instability. SCZ's evolution with film thickness and paste flowability demonstrated the inherent conflict between performance and mix proportion robustness, the increasing fiber size also significantly compressed SCZ ranges. The balance of performance and robustness, as well as the fiber size control, were crucial for achieving reliable SFRSCC production. This study provided valuable insights for the industrial prefabrication or on-site application of SFRSCC.

Performance of hybrid steel fiber-reinforced self-compacting concrete RC beam under flexure

Hybrid steel fiber-reinforced self-compacting concrete (HSFRSCC) has desirable properties for improving the performance of structures. But the literature is sparse on the flexural performance of the reinforced concrete (RC) beam reinforced with hybrid fibers. The impact of the combined action of micro- and hooked-end steel fibers on the flexural performance of the SCC beam to which mineral admixtures and superplasticisers have been added to improve their workability is investigated in this study. In the experiment, beam specimens, reinforced with micro-steel and hooked-end fibers, with a compressive strength of 60 and 80 MPa and of size 150×230×3000 mm were prepared. The results clearly demonstrate that the flexural performance of the SCC beam significantly improved with the addition of hybrid steel fibers. The combination of 0.5% of hooked-end steel fibers and 0.25% of micro-steel fibers offers a better flexural performance than the addition of hybrid fibers in other proportions. Adding hybrid steel fibers in RCSCC beam increases the beam’s load- and moment-carrying capacities by 40.64% and 40%, respectively, compared to the RCSCC beam without hybrid steel fibers. The crack spacing and crack width are also reduced by 16–45% and 25–75%.

The Effect of Fiber Volume Fraction on Fiber Distribution in Steel Fiber Reinforced Self-Compacting Concrete

This paper investigates the effect of fiber volume fraction on fiber distribution in steel fiber reinforced self-compacting concrete (SFRSCC) through experiments and numerical simulations. Three types of SFRSCC beam specimens with different fiber volume fractions (0.3%, 0.6%, and 0.9%) were cut to expose the steel fibers. The number and the orientation angle of the steel fibers on the beam sections were determined by image analysis techniques. Fiber density, fiber segregation coefficient, fiber dispersion coefficient and fiber orientation coefficient were applied to evaluate fiber distribution on the beam sections. Based on the experimental data, numerical models simulating the pouring process of fresh SFRSCC were established to analyze the overall fiber distribution in the specimens. The results show that the distribution state of the fibers on the beam sections is not random and uniform, which is correlated to the fiber volume fraction. Due to the variable rheological properties, a greater fiber volume fraction causes better fiber uniformity, lower fiber segregation and worse fiber alignment on the beam sections. Meanwhile, the numerical results show that the distribution law of fibers along the length direction of the specimens is almost independent of the fiber volume fraction. In addition, increasing the fiber volume fraction results in the increase of the average angle of the fiber orientation in the specimens. The results can provide a reference for optimizing the fiber distribution in the concrete matrix.

A Numerical Method to Study the Fiber Orientation and Distribution of Fiber-Reinforced Self-Compacting Concrete

Steel fiber-reinforced self-compacting concrete (SCFRC) has been developed in recent decades to overcome the weak tensile performance of traditional concretes. As the flexural strength of SCFRC is dependent on the distribution of steel fibers, a numerical model based on Jeffery’s equation was developed in this study for investigating the effects of the concrete flow on the fiber orientation and distribution in SCFRC. This numerical method shows higher computational efficiency than available particle-based methods like SPH and LBM. The influence of casting parameters like casting method, formwork size and casting velocity on the fiber orientation is investigated from the perspective of the flow field of fresh concrete during casting. The simulation results show that the fiber orientation is largely dominated by the concrete flow during the casting process. Importantly, during casting SCFRC beam, fibers tend to be oriented in parallel along the longitudinal direction at the middle section, while they stick up at the end of the formwork due to the upward concrete flow. In addition, the results from parametric studies show that the formwork size and casting method could significantly affect the concrete flow during the casting process, ultimately the orientation of fibers in a SCFRC beam. Furthermore, it indicates that the casting speed needs to be carefully chosen in order to achieve the optimal fiber alignment.

Tensile Performance Test Research of Hybrid Steel Fiber-Reinforced Self-Compacting Concrete.

Notched beam specimens were loaded by the three-point bending test device, and the effects of different volume contents and combinations of steel fibers on the tensile properties of hybrid steel fiber-reinforced self-compacting concrete (HSFRSCC) were studied. The failure law and strain field distribution of the specimens were studied by digital image correlation (DIC) technology. Moreover, the curves between the load and crack mouth opening displacement (CMOD) of 18 groups of hybrid steel fiber-reinforced concrete specimens were obtained, and the stress-strain curves of 18 groups of specimens were derived from the load-CMOD curves. The results show that both single and hybrid steel fibers can improve the crack deformation resistance and tensile properties of concrete, but hybrid steel fibers have a more significant improvement effect. Only when the content of steel fiber is more than 0.6% can it have a more obvious postpeak descending section, and hybrid steel fiber has higher postpeak deformation capacity and flexural toughness. The fundamental reason why concrete with hybrid steel fibers has better tensile properties is that micro and macro steel fibers cooperate with each other to resist cracks, improving the toughness of concrete after cracking. Finally, the mechanism of different size and volume content of steel fiber was analyzed from the micro level, which can be used as a reference for the engineering design of HSFRSCC in the future.

Comprehensive experimental and numerical modeling of strength parameters of eco-friendly steel fiber reinforced SCC containing coarse copper slag aggregates

The copper slag waste (CSW) is an industrial by-product, the annual production of which is huge and its disposal and management are a big challenge for environmentalists. This research has comprehensively studied, experimentally and numerically, the possibility of substituting 20–60% copper slag (CS) for natural coarse aggregates in self-compacting concretes (SCCs) reinforced with 0.1, 0.3 and 0.5% hooked-end steel fibers. According to the results, increasing the CS volume improves the characteristics of the fresh concrete, but there is an obvious drop in its flowability, fillability and passability at the highest steel fiber (SF) volume. Although increasing CS reduces the compressive strength of concretes containing low SF volumes, positive CS effects on the concrete strength are evident at the highest SF volume. Based on the scanning electron microscope (SEM) images, in concretes containing 0.1% SF, an increase in CS increases the tensile strength, and increasing this volume up to 30% makes the concrete microstructure homogeneous and integrated. To check the statistical importance of the results of the tensile and compressive strengths, use was made of the analysis of variance (ANOVA) method. To reduce costs (and human errors) and avoid time wastage, artificial neural network (ANN) prediction models and robust multiple regression analyses (MRA) methods were used to predict the compressive and tensile strengths. Results of this research confirm that using CS in producing steel fiber reinforced self-compacting concrete (SFRSCC) has technical, environmental and economic advantages.

Impact Resistance of Micro and Macro Crimped Steel Fibre Reinforced Self-Compacting Concrete with Scm

Impact Resistance of Micro and Macro Crimped Steel Fibre Reinforced Self-Compacting Concrete with Scm

Modal identification and damping performance of a full‐scale GFRP‐SFRSCC hybrid footbridge

Slender footbridges are prone to excessive vibrations due to pedestrian effects, and comfort criteria often govern their design. In this sense, composite materials that combine high damping capacity with relatively high stiffness and low mass can provide functional benefits. This paper presents a study of the dynamic behaviour of an 11 m long hybrid footbridge made of two I-shaped pultruded glass fibre reinforced polymer (GFRP) main girders and a thin steel fibre reinforced self-compacting concrete (SFRSCC) deck, in operation since 2015. The main goals were (i) to improve the knowledge of the dynamic properties of composite footbridges and (ii) to assess the benefits of using a structure made of pultruded GFRP instead of a conventional material (steel), namely, considering its greater ability to dissipate energy. The resonant frequencies, damping ratios, and mode shapes of the footbridge were identified based on experimental testing. A finite element (FE) model of the footbridge was developed and calibrated with test data and used to simulate the effects of pedestrian loads. Simulations of the same type were conducted on an equivalent structural system made of steel profiles. The simulation results of the two short-span footbridges with similar natural frequencies enhance the impact of high-order harmonics of the pedestrian load in the dynamic response. It is also shown that polymer-based components can contribute to limiting vibrations in footbridges or even act as self-dampers.