Figure - available from: SN Applied Sciences
This content is subject to copyright. Terms and conditions apply.
a Layout of the hollow-core concrete beams. b Cross-sections of the solid beam (B1) and hollow-core concrete beams (B2 to B6). c Side-view in one of the hollow-core beams
Source publication
This paper presents an experimental investigation on the structural performance of hollow-core reinforced self-compacting concrete beams and performs an optimization analysis to select the optimum hollow-core beam section, as well as perform a sustainability analysis. The experimental program includes constructing and testing five beams with differ...
Citations
... The flexural strength of hollow, traditionally reinforced concrete elements can be equal to the flexural strength of solid elements while having significantly lower weight [6][7][8][9]. The main limitations of the weakened hollow cross-section are lower shear strength which has to be considered in the design of the shear reinforcement, and also the compression zone, which will restrict the dimensions and position of the hollow core. ...
... Along with the proposed woven FRP tubular mesh, the 3D printing of FRP reinforcement can supply other more advanced reinforcement structures [15]. The hollow core can be made either using removable formwork [6,7] or lost formwork, in which case the lost formwork can also be used for force transfer and complement the standard reinforcement [3,9]. However, it is not used as a sole reinforcement for load-bearing elements. ...
This article presents woven carbon-fiber-reinforced polymer (CFRP) tubular mesh used as a reinforcement on the inner surface of hollow beams made of high-performance concrete (HPC). The tubular mesh was designed to serve as both the tensile and shear reinforcement of hollow beams intended for the construction of small self-supporting structures that could be assembled without mechanization. The reinforcement was prepared with a tri-axial weaving machine from carbon filament yarn and was homogenized using epoxy resin. The interaction of the composite reinforcement with the cementitious matrix was investigated, and the surface of the reinforcement was modified using silica sand and polyvinyl alcohol (PVA) fibers to improve cohesion. The sand coating enhanced bond strength, resulting in the significantly higher flexural strength of the hollow beam of 128%. The PVA fibers had a lower positive effect of 64% on the flexural strength but improved the ductility of the beam. Individual beams were connected by gluing steel parts directly inside the hollow core of the HPC beam. This procedure provides good interaction between the CFRP reinforcement and the glued steel insert and allows for the fast and simple assembly of structures. The weaving of additional layers of the CFRP reinforcement around HPC beams was also explored. A small structure made of the hollow HPC beams with inner composite reinforcement was constructed to demonstrate the possibilities of the presented technology.
... In recent years, several studies have been carried out to reduce the use of concrete in construction, especially for beam sections [4], reporting a reduction in concrete in tension zones of up to 25%, and making hollow beams using GI pipes would be economical. The flexural strength of the RC hollow beam is almost the same as that of the RC control beam [5][6][7]; in another study, regarding the optimization of structural materials, Manikandan et al. [8] introduced hollow-core to the use of Expanded Polystyrene Foam in the zone tensile strength in RC beams, Patel [9] using hollow balls in reinforced concrete beams, obtained a weight reduction of about 12% and 33% of the crack and rupture index which is higher than that of control beam beams; furthermore, several studies on hybrid beams, layer on the tensile zone uses lower quality than concrete in the compression zone, by Ataria and Wang [10], Syahrul et al. [11], Fakhruddin et al. [12] and Hussein et al. [13] the results show the same thing, namely the hybrid beam has decreased flexural capacity. ...
This study aims to analyze the flexural capacity of RC without concrete in a tension cross-section using an experimental method. The number of specimens is three pieces, namely a spiral reinforced concrete beam (SBC) and a vertical reinforced concrete beam (CBN); both of these blocks are without concrete in the cross-section of the reinforcement and 60D tensile steel reinforcement in the support area, where D is the primary diameter, and a conventional concrete beam as the control beam (CB). The beam size is 3100×150×200 mm. The beams are supported by simple supports with a span of 3000 mm. The concrete in the structural beam elements, which work optimally to withstand the load, is the outermost fibre part of the side, while the concrete on the tension side does not have a direct role in determining the magnitude of the resisting moment. Therefore, the quality of the concrete in the concrete beam section must be optimized, while the concrete in the tension section must be minimized. Eliminating concrete in tension areas reduces the construction's self-weight and use of concrete-making materials. The main variables in this research are bending behaviour and crack pattern. The beam specimens were tested with two-point loading monotonically. By observing the crack pattern and failure mode, the results showed an increase in the capacity load of SBC by 21.58% CBN but a decrease of 27.57% compared to the CB control beam. Flexural cracks and beam failures resembled under-reinforcing. The flexural capacity was analyzed based on static analysis and then validated by calculating the ratio between the theoretical nominal moment and the experimental moment. This finding shows that changing the conventional shear reinforcement model to spiral can increase the flexural of the beam without concrete in the tension cross-section. Doi: 10.28991/CEJ-2022-08-11-014 Full Text: PDF
... [13][14][15][16]. Recently, there have been efforts to study the behavior of concrete beams with longitudinal openings as follows Murtada and Yahyia [17] investigated the structural behavior of shallow self-compacting beams when the diameter of the holes was changed, and it was found that the ultimate load decreases with the increase in the diameter of the holes. Muhanad and Saad [18] Hadi et al. [19] They found that circular holes are better than rectangular when used in deep beams to make longitudinal holes. ...
The loads in the deep beams are transmitted diagonally from the load area to the support area by means of the strut and the tie. It is characterized by having a small span to depth ratio. which causes the distribution of stresses to be non-linear within the beam, which motivates researchers to study the effect of the placing of longitudinal hollows and the extent to which these holes affect the behavior and distribution of stresses for these types of beams. In addition to the advantages added by longitudinal hollow to the beam such as reducing weight and passing various electrical and mechanical services...etc. This study investigated the effect of making longitudinal circular holes (with a diameter of 50mm) with a slope on the structural behavior of three deep beams with a solid sample as a reference where the slope used was 0%, 4.3%, and 7.8%. The results showed that making holes reduces the load capacity of the deep beam, a decrease in the failure load was observed by 7.56%, 8.96%, and 11.2% for hollow beams with a slope of 0%, 4.3%, and 7.8%, respectively. Also, the appearance of flexural cracking increased by 2.66%, 2.66%, and 6.66%.and 2.14%, 3.52%, and 7.14%, respectively, for shear cracks. While the effect was small for the neutral axis location as well as for the vertical deflection.
... In their results the torsional capacity was improved when the steel fiber ratio increased. [6] were introduced an alkali -activity concrete beams with fibers or conventionally reinforced. The fibers increase the cracking load of the beams by 20% in comparison with conventional reinforcement. ...
Many factors affect the torsional behavior of reinforced concrete beams, such as concrete strength, section dimensions, aspect ratio and concrete cover. Improvements in the torsional behavior of RC members had led researchers to investigate the effect of additional factors such as steel fibers, torsional reinforcement ratio and reinforcement arrangement. Based on the above, there is a gap in previous studies in taking effect of the distribution of stirrups with longitudinal reinforcement steel with steel fibers. Twenty-six reinforced concrete beams 250 mm wide, 250 mm high, and 1150 mm long are investigated under pure torsion. Consider the effect of the steel fiber ratio, stirrup ratio, and longitudinal reinforcement ratio of high-strength concrete. The results show the behavior of the concrete changing from brittle to ductile when increasing the ratio of the steel fiber registering the maximum torsional ductility index (3.98). The increase in the percentage of steel fiber to 6% caused a 105% increase in torque, but it was a slight increase in torque with respect to the percentage of steel fibers at 2%. The optimum ratio of the steel fiber is 2% in terms of increased torque and workability, as it gave an increase in torque which reached 98.8%. Increasing the percentage of the stirrups to 2.5%, while the percentage of longitudinal reinforcement and the percentage of steel fiber was fixed, which led to an increase in torque which reached 130.4%. Increasing the percentage of the longitudinal reinforcement to 50%, while the percentage of stirrups and the percentage of steel fiber was fixed, which led to an increase in torque which reached 66.9%.
Compaction generally becomes challenging, time-consuming, and requires more labour during casting, and this can be effectively handled using the self-consolidating concrete (SCC). In this study, fibre-reinforced self-consolidating concretes were developed with metallic fibres, polymeric synthetic fibres, or a combination of both for enhancing concrete's mechanical properties. However, the properties of concrete are only slightly enhanced by using a single type of fibre for reinforcement. On the contrary, hybrid fibre-reinforced concretes, which are strengthened with a number of distinct kinds of specifically selected fibres, offer superior characteristics. The incorporation of the hybrid fibres into brittle self-consolidating concrete (SCC) helps to strengthen the concrete and overcome this problem. For this purpose, hybrid fibre-reinforced self-consolidating concrete (HFSCC) specimens with 0.75%, 0.80%, 0.85%, and 0.90% steel and 0.15% polypropylene fibres were tested. The workability properties of the SCC as a result of the addition of hybrid fibres were also investigated by performing fresh concrete tests such as the slump flow, V-funnel, and the L-box test to assess compactibility such as filling ability and passing ability. Additionally, cylinders and cubes were casted to determine the splitting tensile strength and compressive strength. As a result, the hybrid fibres improved the compressive and split tensile strengths. Thus, incorporating hybrid fibres into the mix revealed that increasing the fibre content of the concretes reduced their workability slightly.
This study investigated the flexural behavior of hollow concrete beams reinforced with GFRP bars with longitudinal openings of different sizes and shapes. A total of seven beams were tested, including two solid GFRP-RC beams, four hollow GFRP-RC beams with longitudinal holes accounting for between 6 and 15% of the total cross-sectional area, and one hollow conventional steel-RC beam with a longitudinal hole of 9% of the total area. The beams were tested in flexure, and the results in terms of cracking and the ultimate loads, strains in steel and concrete, and failure modes were reported. The circular cavity performed slightly better than the square cavity, with a 3.8% higher cracking load and 4.5% higher ultimate load for the same area and location. In addition, an analytical study of the flexural capacity of the hollow beams was developed. It was found that the proposed analytical model predicted the cracking and ultimate load of the tested hollow GFRP-RC beams with good agreement. Finally, a detailed parametric study was conducted to investigate the effects of several key factors, including the size and location of the holes, as well as the concrete grade and the reinforcement ratio. The results indicated that the position of the holes had a significant effect on the behavior of the hollow GFRP-RC beams. The parametric study showed that the compressive strength of the concrete was the most influential factor on the flexural capacity of the beams, while the GFRP reinforcement ratio had a minor effect on the cracking load.
