Torsional Reinforcement Research Articles

Biomimetic Bouligand chiral fibers array enables strong and superelastic ceramic aerogels

Ceramic aerogels are often used when thermal insulation materials are desired; however, they are still plagued by poor mechanical stability under thermal shock. Here, inspired by the dactyl clubs of mantis shrimp found in nature, which form by directed assembly into hierarchical, chiral and Bouligand (twisted plywood) structure exhibiting superior mechanical properties, we present a compositional and structural engineering strategy to develop strong, superelastic and fatigue resistance ceramic aerogels with chiral fibers array resembling Bouligand architecture. Benefiting from the stress dissipation, crack torsion and mechanical reinforcement of micro-/nano-scale Bouligand array, the tensile strength of these aerogels (170.38 MPa) is between one and two orders of magnitude greater than that of state-of-the-art nanofibrous aerogels. In addition, the developed aerogels feature low density and thermal conductivity, good compressive properties with rapid recovery from 80 % strain, and thermal stability up to 1200 °C, making them ideal for thermal insulation applications.

Torsion Improvement of Reinforced Self-Compacting Concrete Beams Using Epoxy Injection and CFRP

Few researchers have investigated the internal torsional reinforcement of box timbers, so little research has been conducted on this particular fortification method. The primary objective is to find out the possibility of adding a certain percentage of RCA to the NC mixtures, as well as verifying the success achieved in repairing the cracks that occurred as a result of torsion with CFRP or injecting with epoxy, which has not been addressed in previous research and literature reviews. This study reinforces reinforced SCC box columns subjected to complete torsion with CFRP sheets and epoxy resin injections. Four reinforced SCC specimens (the first beam with 0%, the second beam with 33.3%, the third beam with 67.7%, and the fourth beam with 100% RCA by weight) were subjected to pure torsion until failure. The dimensions and reinforcement of every specimen are identical. In addition, the applied torque-twist angle relationship at the midspan and end span was investigated. Bending experiments were performed to establish load-deflection curves and assess failure modes. After structural rehabilitation, all beams exhibited increased rigidity values, according to the results. Epoxy resin and CFRP sheet contributed to the specimens' increased ultimate load. The ultimate strength of RCA beams strengthened with CFRP and injected with epoxy increased. The specimens' flexural strength was considerably enhanced by the combination of surface roughness and fracture injection, and the effectiveness of using RCA was very good; it could be replaced with NCA in concrete mixtures, according to the ratio and need. Doi: 10.28991/CEJ-2023-09-11-05 Full Text: PDF

Novel Torsional Reinforcement of Concrete Beams Utilizing Cross-Rod Steel Reinforcement

External strengthening of reinforced-concrete beams is challenging because of the building system complexity or the beam geometry. The major challenge is choosing an appropriate strengthening method to overcome its low torsion strength. Therefore, the main objective of this research is to ascertain how likely it is to suggest or adopt a particular internal in-plane approach to increase the torsional strength. In the present paper, the concept (technique) of adding internal concrete cross-rods (CR) in a transverse direction is adopted. Five concrete beam specimens with 200-, 200-, and 1500-mm dimensions for width, depth, and length, respectively, were poured and tested. One was a reference beam(B-R) without enhancement, while the other four (B-3CR, B-5CR, B-7CR, and B-9CR) were enhanced with three, five, seven, and nine internal cross-rod, respectively. The compressive strength of the concrete was (35MPa) at (28) days (normal strength concrete). This research intends to show how internal cross-rods (CR) and their number affect torsional capability. The experimental findings revealed significant improvements in the ultimate torsion strength capability by about 11.65%, 18.95%, 21.24%, and 27.77%, respectively, compared to the reference beam. The ultimate twisting angle and reinforced beams’ toughness increased by (4.25%-28.36%) and (24.12%-94.48%), respectively, due to the increase in the number of internal cross-rods compared to the reference beam. It was concluded that interior cross-rods would enhance the torsional strength capacity of the reinforced concrete beams. The extent of enhancement depended mainly on the number of internal cross-rods (CR) deployed.

Experimental and Numerical Investigation for Torsional Behavior of UHPFRC Shallow and Deep Beams

AbstractWith increasing the use of ultra-high performance fiber reinforced concrete (UHPFRC) in recent years, torsional design of UHPFRC beams has become of great importance. This paper presents an experimental and numerical study to investigate the torsional behavior of UHPFRC shallow and deep beams with fcu equal to 190.2 MPa. Ten UHPFRC beams with steel fibers volume fraction of 1.5% subjected to pure torsion were investigated. The provided torsional web reinforcement ratio, the area of longitudinal bars and the tested span to total height ratio (L/h = 6.0, 4.0, 2.0 and 1.0) were the studied parameters. A numerical model has been proposed to predict the torsional response of tested beams. Experimental results showed that increasing stirrups’ spacing for the beams of the same L/h ratio (to be 235% of the maximum given by ACI 318-2019 code), reduced the experimental ultimate torsional strength by only 6.7%. The torsional web reinforcement ratio of UHPFRC shallow and deep beams can be safely taken to be 40% of the minimum required by ACI 318-2019. The maximum stirrups spacing can be safely taken the lesser of twice the beam width or 300 mm. The equation used by ACI 318-2019 and ECP-203-2020 for calculating the cracking strength in torsion has been modified to be suitable for UHPFRC beams by taking into consideration the L/h ratio and steel fibers percent. The proposed 3-D numerical model showed good predictions for the torsional strength of tested UHPFRC shallow and deep beams.

Torsional strength limitation of reinforced concrete beams

In order to promote stirrup yielding prior to concrete crushing and avoid over-reinforcement failure modes in reinforced concrete (RC) members, current design codes stipulate limits on the maximum amount of shear and torsional reinforcement. Studies have shown that the shear strength limits introduced based on the plane-truss approach estimate the maximum shear strength and shear failure mode with reasonable accuracy. However, the torsional strength limits derived based on the space-truss analogy and thin-walled tube theory generally overestimate the maximum torsional strength. In this study, the difference between the limiting values introduced in current design codes on the maximum shear and torsional strengths was evaluated by analysing the test results of 406 shear and 153 torsional members. Additionally, experimental tests were conducted on 22 RC beams subjected to torsional moments in order to measure the strain rate of the web concrete directly and investigate the torsional strength limits. The torsional strength limits derived based on the space-truss model overestimated the actual maximum torsional strength. Based on these observations, a lower limit for the maximum torsional strength is proposed in order to avoid over-reinforced torsional failure.

Numerical Analysis of Torsional Reinforcement of Concrete Beams in Unconventional by ANSYS Software

In this study, a finite element analysis is conducted to study the behaviour of RC beams with different configurations of transverse reinforcement under torsion. These configurations of stirrups are traditional closed stirrups, circular spiral stirrups, and inclined rectangular spiral stirrups. The numerical torsional load values are compared with the experimental torsional load values from previous research. The numerical analysis determined by the ANSYS software shows a reasonable agreement with the experimental torsional load values. The numerical results demonstrate that the use of continuous rectangular spiral stirrups improved the torsional response compared to using another type of beam stirrup. Thus, numerical results show that continuous spiral stirrups are effective at increasing torsional capacity. It is also noted that the behaviour of these beams with continuous spiral stirrups is better than the behaviour of the beams with traditional stirrups. The beams with helical reinforcement, which are TB2, TB3, and TB4 spiral reinforcements, greatly enhanced the toughness. The equivalent stresses are 13.709, 13.728, 14.72, and 15.894 MPa, while the equivalent elastic strains are 0.00421, 0.00377, 0.00347, and 0.00539 mm/mm for the beams TB2, TB3, and TB4, respectively. The beam TB4 had the highest stress and strain value, so its strength improved its ductility properties. As a result, the stirrups' configurations enabled the detection of beam failure mechanisms by improving torsional behaviour when compared to the beam's traditional stirrups. As a result, this research adds more knowledge to the literature on the most effective spiral stirrups for transverse reinforcement to improve the torsional behaviour of beams. Doi: 10.28991/CEJ-2023-09-01-04 Full Text: PDF

Development of Prediction Models for the Torsion Capacity of Reinforced Concrete Beams Using M5P and Nonlinear Regression Models

Torsional strength is related with one of the most critical failure types for the design and assessment of reinforced concrete (RC) members due to the complexity of the associated stress state and low ductility. Previous studies have shown that reliable methods to predict the torsional strength of RC beams are still needed, namely for over-reinforced and high-strength RC beams. This research aims to offer a novel set of models to predict the torsional strength of RC beams with a wide range of design attributes and geometries by using advanced M5P tree and nonlinear regression models. For this, a broad database with 202 experimental tests is used to generate highly reliable and resilient models. To build the models, three independent variables related with the properties of the RC beams are considered: concrete cross-section area (area enclosed within the outer perimeter of the cross-section), concrete compressive strength, and torsional reinforcement factor (which accounts for the type—longitudinal or transverse—amount, and yielding strength of the torsional reinforcement). In contrast to multiple nonlinear regression approaches, the findings show that the M5P tree approach has the best estimation in terms of both accuracy and safety. Furthermore, M5P model predictions are far more accurate and safer than the most prevalent design equations. Finally, sensitivity and parametric studies are used to confirm the robustness of the presented models.

Effect of stirrup, longitudinal reinforcement and steel fibers ratios on the torsional behavior of high strength concrete beams

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 the 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 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%.

A Flexure-Based Linear Guide With Torsion Reinforcement Structures

Abstract In this study, a flexure-based (compliant) linear guide with a motion range comparable to its footprint is presented. The design consists of two-folded leaf springs on which torsion reinforcement structures are added. Due to these structures, only two-folded leaf springs are needed instead of a minimum of five as in preexisting designs. The new design is compared to such a preexisting design, after optimizing both on a support stiffness metric. The new design scores over twice as high on the support stiffness metric, while occupying a smaller (−33%) and a less obstructive build volume. Stress, build volume, and manufacturing limitations are taken into account. In addition, a variation on the new design using three torsion reinforced folded leaf springs is presented and optimized. This design occupies a build volume similar to the preexisting design, but scores four times higher on the support stiffness metric. A prototype of the new design is built and its parasitic eigenfrequencies are measured, validating the theoretical models (normalized mean absolute error of 4.3%).

Structural behavior of reinforced concrete beams with out of plane part

This research aims to investigate and compare the experimental structural behavior of reinforced concrete straight beam and other beams which made with one out of plane part. The study focuses on the influence of the out plane part on the mid span deflection, angle of twist, ultimate load, and failure mode. Also, study the improvement of the structural behavior by using concrete with higher compressive strength and increase the ratio of the longitudinal reinforcement. A total of four beams, the first one was normal strength concrete NSC straight beam were instrumented used as a control beam, three of which were with one out of plane part and fabricated from NSC and high strength concrete HSC. One of them is HSC with torsional longitudinal reinforcement at out of plane part. All beam specimens were clamped by steel fixed ends and subjected to the two-point loads up to their collapse. The results presented that the ratio of the ultimate load of normal strength concrete straight beam to the ultimate load of normal strength, high strength, and high strength concrete with the addition torsional reinforcement of beams with one out of plane part was 35.95%, 33.33%, and 20.16% respectively and the deflection at mid span decreased at the ultimate load. Also, the obtained results showed that the angle of twist decreased when increasing the concrete compressive strength, but increased at the ultimate load when using additional longitudinal torsional reinforcement.

REINFORCED CONCRETE BEAM AND COLUMN PROGRAMMING BASED ON SNI:2847-2019 ON SMARTPHONE USING TEXAS INSTRUMENTS

<p class="Isiabstract">The development of technology in the last few years can not be denied that it has developed very rapidly. In building construction, reinforced concrete beam and columns calculations also utilizing that technology development. Input data used to calculate reinforcement of beam and column are material property, section property and internal forces. Calculation of reinforcement beam using quadratic equation method and reinforcement column using Newton-Raphson method and divided-by-two method.Calculation results are flexural reinforcement As (longitudinal compression area) and As' (longitudinal tension area), shear reinforcement Av (transversal area) and S (distance of Av), torsional reinforcement Avt (transversal area due to torsional and/or shear), S (distance of Avt), Along (longitudinal area due to torsional buckling), column circular reinforcement Atot (total of longitudinal area), column rectangular two faces reinforcement Atot (total of longitudinal area), column rectangular four faces reinforcement Atot (total of longitudinal area), column biaxial reinforcement Atot (total of longitudinal area). The program determines As, As’ and Atotal, the code is written using the Texas Instruments programming language, so that it can be applied to smartphones. Smartphone and manual calculation, for all cases not more than 5%, the calculation using Texas Instrument is accurate.</p>

Pure torsional behavior of RC beams in relation to the amount of torsional reinforcement and cross-sectional properties

According to the current ACI318-19 building code, torsional strength is calculated by reflecting the effective area of concrete and the properties of torsional reinforcement, regardless of the cross-sectional properties of the reinforced concrete members. Past research has revealed that the torsional failure mode of RC members subjected to torsional strength is influenced by the contribution of the concrete and the amount of torsional reinforcement. In this study, 11 experiments were conducted to examine the pure torsional behavior of RC members in relation to their cross-sectional properties, and the amount of torsional reinforcement. The experimental variables were (1) the properties of the solid and hollow cross-sections, (2) the amount of arranged torsional reinforcement compared to that of the ACI 318-19 building code, (3) the yield strength of the torsional reinforcement, and (4) the spacing of the torsional reinforcement. The results showed that solid cross-sections and hollow cross-sections had similar levels of torsional strength. In addition, the specimens with a smaller amount of arranged torsional reinforcement were engaged in ductile behavior when compared with the ACI 318-19 building code, regardless of their cross-sectional properties.

Maximum torsional reinforcement ratio of reinforced concrete beams

The amount of maximum torsional reinforcement is specified to prevent the failure of concrete compressive struts before the reinforcement yielding in reinforced concrete members subjected to torsion. The maximum torsional reinforcement presented in the design codes, however, differs by up to more than three times. This study therefore aimed to theoretically derive the maximum torsional reinforcement ratio. The proposed ratio was derived based on the equilibrium and compatibility conditions. The parametric study results of the torsional behavior analysis were also used to reflect key variables, such as tensile resistance of concrete, the cross-sectional area surrounded by shear flow, the concrete softening factor, and the average stress factor, in a simple form. In addition, the maximum reinforcement was presented not only in transverse direction but also in longitudinal direction to predict the failure modes of torsional members according to the yielding of reinforcements. The validation was performed by comparison with the experimental results of 98 beams under pure torsion collected from the literature, and the maximum torsional reinforcement ratio proposed in this study was found to reflect the failure modes of reinforced concrete beams subjected to pure torsion better than those suggested by other researchers and the design codes.

Estimation of Minimum Torsional Reinforcement of Reinforced Concrete and Steel Fiber-Reinforced Concrete Members

The current code specifies a minimum torsional reinforcement ratio to prevent possible brittle failure after torsional cracking in concrete members. However, since there are many researches, in which even the concrete members with the minimum torsional reinforcement fail to secure sufficient reserved strength after torsional cracking, continuous research needs to be carried out. Accordingly, in the authors’ previous research, a minimum torsional reinforcement ratio was proposed based on the reserved strength concept and was extended to the steel fiber-reinforced concrete members in order to suggest the minimum fiber factor as the minimum torsional reinforcement ratio. In the present study, a pure torsion test was carried out on reinforced concrete and steel fiber-reinforced concrete members after a brief introduction on the above, and the proposed model was verified based on the test results. The test results of six torsional specimens were compared with those of the proposed model, and it was found that the proposed model provides a reasonable evaluation on the torsional failure mode of the specimen according to the reserved strength ratio.

Torsional Behavior of High‐Strength Concrete Beams with Minimum Reinforcement Ratio

Although there is a growing trend to use higher strength for concrete and steel in reinforced concrete structures due to the lightness and slenderness of these members together with the simplified arrangement of their reinforcement, there is still the necessity to inspect the reduction of ductility resulting from the gain in strength. Taking into account that this also concerns the design for torsion, this study intends to investigate the regulations related to the torsional minimum reinforcement ratio in view of the minimum ductility requirement with focus on Eurocode 2. To that goal, the relation between the torsional cracking moment and the ductile behavior is discussed for the beam reinforced with the minimum torsional reinforcement ratio to examine the eventual properness of the minimum torsional reinforcement ratio recommended by Eurocode 2. Moreover, a pure torsion test is performed on 18 beams made of 80 MPa concrete reinforced by high‐strength bars with rectangular section and various test variables involving the minimum torsional reinforcement ratio, the transverse‐to‐longitudinal reinforcement ratio, and the total reinforcement ratio. As a result, for the high‐strength concrete beams, the minimum torsional reinforcement ratio recommended by Eurocode 2 was insufficient to prevent the sudden loss of strength after the initiation of the torsional cracking. But with regard to the compatibility torsion of statically indeterminate structure, the adoption of the minimum torsional reinforcement ratio recommended by Eurocode 2 might secure enough deformability under displacement‐controlled mode to allow the redistribution of the torsional moment.

Study of torsional behavior of reinforced concrete beams strengthened with aramid fiber strips

This paper investigates the strengthening of reinforced concrete (RC) beams for its torsional behavior using aramid fiber strips. Most of the time aramid fiber is used as an externally bonded reinforcement to increase flexural and shear strength of RC beams. An attempt is made to use it for improving torsional moment carrying capacity of RC beam. Torsional failure mostly occurs in earthquake prone areas subjected to rapid failure. Brittle failure of structures occurs due to torsional moment. Different patterns of aramid fiber strips are selected to wrap around RC beams and torsional behavior of these strengthened beams is studied. RC beam of M30 grade of concrete is strengthened with aramid fiber strips and tested for torsional failure using lever arms subjected to torque. The beam size is 150 mm × 300 mm and of 1.3 m in length, designed as per IS456-2000. A total of 21 numbers of reinforced concrete rectangular beams were cast for the experimental study. Three are taken as controlled beams with normal reinforcement, 3 beams are designed with torsional reinforcement and other 15 beams with normal reinforcement have grouped in five sets. These five sets are strengthened using aramid fiber strips of 150 mm width with variable spacing of 100, 125, 150, 175 and 200 mm, respectively. The effect of different configuration of aramid fiber on torsional moment carrying capacity, angle of twist and failure mode of the beams is studied.

Minimum torsional reinforcement ratio for reinforced concrete members with steel fibers

The current design codes for concrete structures suggest the minimum torsional reinforcement ratio to induce minimum ductile failure after cracking in reinforced concrete (RC) members subjected to torsional moment. However, as the member strengths are quite often lower than the torsional cracking moment strengths even when satisfying minimum torsional reinforcement ratio specified in the current codes, it may not serve the original purpose of preventing brittle failure immediately after cracking. In this study, a rational equation is thus presented for calculating the minimum torsional reinforcement ratio that could provide a sufficient margin of safety in design. The minimum fiber factor to be applied in steel fiber reinforced concrete (SFRC) members is also proposed. The proposed model was found to reflect the effects of torsional cracking strength, longitudinal and transverse reinforcement ratio, and the presence of torsional reinforcement in concrete members. It was also found that as the reserved strength included in the proposed equation is determined based on the test results of the RC members, it contains an appropriate factor of safety for the RC members. In addition, it was confirmed that the minimum fiber factor is conservative compared with the collected test results of the SFRC specimens.

Ductility of RC beams under torsion

In this article, the torsional ductility of reinforced concrete (RC) beams with rectangular cross section is studied. For this, the experimental results of several RC beams found in the literature were compiled and analyzed. A torsional ductility index was used to characterize the torsional ductility of the studied beams. The following variables study were considered: compressive concrete strength, torsional reinforcement ratio and cross section type (plain or hollow). The influence of each variable study on the torsional ductility is studied and important findings are pointed out which could help for the design of RC beams under torsion. An additional comparative analysis with the rules from some codes of practice in use is also performed. It is shown that, in general, the codes are too much restrictive as far as the maximum torsional reinforcement is concerned. As a consequence, this can leads to the unacceptance of several beams with ductile behavior.

Maximum Torsional Reinforcement of Reinforced Concrete Beams Subjected to Pure Torsion

Maximum Torsional Reinforcement of Reinforced Concrete Beams Subjected to Pure Torsion

Torsional behaviour of reinforced concrete beam wrapped with aramid fiber

Present study gives the torsional behaviour of Reinforced Concrete (RC) beam of M30 grade of concrete strengthened with aramid fiber. The aramid fiber as an externally bonded reinforcement used for increasing flexural strength, an attempt is made to use it for improving torsional behaviour of RC beam. Torsional failure mostly occurs in seismic affected areas subjected to sudden failure. Torsional failure is brittle type failure occurs due to undesirable loading.RC beam strengthened with aramid fiber tested for torsional moment using lever arms subjected to equal static loading which transfer equal torsional moment to the beam. The cross section of beam is 150 mm × 300 mm and of 1 m in length. In that three beams were designed for torsional reinforcement and nine as conventional beams. Beam is designed for torsion as per IS456-2000. Building designed earlier using the codes were insufficient to cater for torsional reinforcement. This research investigates behaviour of such conventional beams for torsion when wrapped with aramid fiber. Torsional moments of such strengthened beams are compared with torsionally designed beams which are designed as per new design codes. The study is restricted to aramid fiber fully wrapped and wrapped in strips at width 100 mm of U shape on three faces of beam by using epoxy resin.Experimental result includes ultimate loads & first cracking loads, angle of twist and twisted shape of the beam. Result shows that fully wrapped RC beam gives more torsional strength as compared to controlled beam and there is significant improvement in torsional strength of beams wrapped in strips. After first crack, beam shows tendency to carry load with increase in angle of twist. Thus it is easy method for strengthening of RC beams.