Flexural response of hollow high strength concrete beams considering different size reductions

In this study, an experimental work was directed toward comparing the flexural behavior of solid and hollow steel fiber-reinforced concrete beams. For this purpose, eight square cross-sectional beam specimens, four solid and four hollow, were prepared. One concrete mixture with four different steel fiber contents of 0, 0.5, 1.0, and 1.5% were used. The side length of the central square hole was 80 mm, whereas the cross-sectional side length was 150 mm. All beams were tested under four-point monotonic loading until failure. In addition to the solid and hollow beams, cylinders were cast to evaluate the compressive strength, splitting tensile strength, and modulus of elasticity, whereas prisms were used to conduct the fracture test. The test results showed that all fibrous beams failed in flexure, whereas those without fiber exhibited flexural-shear failure. In general, the flexural behavior of fibrous-beams was superior to that of beams without fiber. The hollow beams with fiber contents of 0, 0.5, and 1.0% were observed to withstand lower loads at cracking, yielding, and peak stages compared with their corresponding solid beams; this was not the case for the 1.5% fiber hollow beam, which exhibited a higher peak load than its corresponding solid beam. Although all eight beams exhibited ductility indices higher than 3.7, hollow beams exhibited better ductility than solid beams, showing higher ductility index values.

https://downloads.hindawi.com/journals/ace/2019/8390345.pdf

Experimental Investigation on the Effect of Steel Fibers on the Flexural Behavior and Ductility of High-Strength Concrete Hollow Beams

Purpose: This research paper adopts the fundamental tenets of advanced technologies in industry 4.0 to monitor the structural health of concrete beam members using cost effective non-destructive technologies. In so doing, the work illustrates how a coalescence of low-cost digital technologies can seamlessly integrate to solve practical construction problems.

Methodology: A mixed philosophies epistemological design is adopted to implement the empirical quantitative analysis of ‘real-time’ data collected via sensor-based technologies streamed through a Raspberry Pi and uploaded onto a cloud-based system. Data was analysed using a hybrid approach that combined both vibration characteristic based method and linear variable differential transducers (LVDT). 

Findings: The research utilises a novel digital research approach for accurately detecting and recording the localisation of structural cracks in concrete beams. This nondestructive low-cost approach was shown to perform with a high degree of accuracy and precision, as verified by the LVDT measurements. This research is testament to the fact that as technological advancements progress at an exponential rate, the cost of implementation continues to reduce to produce higher accuracy ‘mass-market’ solutions for industry practitioners. 

Originality: Accurate structural health monitoring of concrete structures necessitates expensive equipment, complex signal processing and skilled operator. The concrete industry is in dire need of a simple but reliable technique that can reduce the testing time, cost and complexity of maintenance of structures. This was the first experiment of its kind that seeks to develop an unconventional approach to solve the maintenance problem associated with concrete structures. This study merges industry 4.0 digital technologies with a novel low-cost and automated hybrid analysis for real-time structural health monitoring of concrete beams by fusing several multidisciplinary approaches in one integral technological configuration.

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Real-time structural health monitoring for concrete beams: a cost-effective ‘Industry 4.0’ solution using piezo sensors

Deflection of Reinforced Concrete Beams with Longitudinal Circular Hole

Twelve ECC beams with three different fiber types, along with four normal concrete beams, were tested in this study to evaluate the influence of cross-sectional hollowing on their flexural performance. The fiber types used were nylon monofilament (NM), low-cost untreated polyvinyl alcohol (PVA), and polypropylene (PP). Three different square hole sizes of 60, 80, and 100 mm with cross-sectional hollowing ratios of 0.16, 0.28, and 0.44, respectively, were adopted for each group of beams in addition to a solid beam. All beams were tested under four-point loading using a displacement-controlled testing machine. The test results showed that ECC beams can mostly withstand higher cracking and ultimate loads compared to their corresponding normal concrete versions. The results also showed that both the ductility and toughness of the ECC beams are higher than those of the normal concrete beams and that the ductility values of the hollow beams with a hole size of 60 mm are higher than those of the corresponding solid beams. Moreover, hollow ECC beams with hole sizes of 60 and 80 mm exhibited a higher ductility than a solid normal concrete beam.

Flexural behavior of ECC hollow beams incorporating different synthetic fibers

The main aim of this investigation was to study the flexural strength of simply supported rectangular RC hollow beams (with a longitudinal circular hole) subjected to gradually increased and symmetrically applied two-point loads. Each hollow beam had a 25-, 40-, or 50-mm-diameter hole, and the position of the center of the hole also varied from 45 to 180 mm from the top. The cross section of the beam, the amount of longitudinal steel, and the transverse steel of the beam were kept constant. The same M20 grade of concrete was adopted for all of the beams. The shear span-to-effective depth ratio (av/d) of 2.69 was kept constant. Theoretical equations are developed, or existing equations are modified, to determine the first cracking load and the ultimate load of the beams. The influence of the hole on the strength of the beams is studied by taking into account the area and position of the hole. To examine the validity of the developed theoretical equation, 12 hollow RC beams and one solid RC beam wer...

Influence of a Longitudinal Circular Hole on Flexural Strength of Reinforced Concrete Beams

Horizontal Thrust in Vertically Curved Reinforced Concrete Beams

Desert cotton and areca nut husk fibre reinforced hybridized bio-benzoxazine/epoxy bio-composites: Thermal, electrical and acoustic insulation applications

Arun Murugesan

Papers

Influence of a Longitudinal Circular Hole on Flexural Strength of Reinforced Concrete Beams

Deflection of Reinforced Concrete Beams with Longitudinal Circular Hole

Horizontal Thrust in Vertically Curved Reinforced Concrete Beams

Desert cotton and areca nut husk fibre reinforced hybridized bio-benzoxazine/epoxy bio-composites: Thermal, electrical and acoustic insulation applications

Studies on nano-hybrid biopolymer composite coating on corroded steel to improve the corrosion resistance and hydrophobicity of the surface