The effects of stiffener configuration on stiffened T-stubs

Yasin Onuralp Özkılıç 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.4

The stiffeners, also known as ribs, are utilized to increase the resistance of T-stubs. The author’s previous studies showed that stiffeners can increase plastic capacity by an average of 1.71 times. A combined experimental and numerical study was undertaken to examine the effects of the stiffener configuration on the behavior of T-stubs. A total of 20 stiffened T-stubs where the shape and angle of stiffeners were considered as the main parameters were tested under monotonic loading. Rectangular, triangular and AISC types of stiffener were tested under monotonic loading. The experimental results indicated that when the height of the stiffener is equal to or higher than the length of the stiffener, the shape of the stiffener does not have an influence on the behavior. A numerical study using the finite element tool ABAQUS was carried out in order to further investigate the effects of the stiffener shapes. In this case, the height is considered less than the length of the stiffener. Moreover, the shape of the stiffeners was investigated with the different thicknesses of the stiffener. The simulation findings revealed that when the height of the stiffener is less than the length of the stiffener, the shape of the stiffener significantly affects the plastic capacity. Based on the numerical and experimental results, it is recommended to use the triangular shape of the stiffener when height is equal to or higher than the length of the stiffener while it is recommended to utilize the rectangular shape of the stiffener when height is less than the length of the stiffener.

Numerical evaluation of effects of shear span, stirrup spacing and angle of stirrup on reinforced concrete beam behaviour

Yasin Onuralp Özkılıç,Ceyhun Aksoylu,Musa Hakan Arslan 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.3

Shear and bending strength of reinforced concrete beams depend on many parameters. It is extremely important to take the necessary precautions in terms of shear in order for the beams to reach their bending capacity. For this reason, it is necessary to determine the effective parameters especially on shear capacity in beams. However, the actual capacity calculation is quite difficult according to regulations that are very conservative in terms of design. Therefore, many experimental studies have been conducted on the shear capacity of the beams. However, this situation is not meaningful in terms of both time and cost, since many experiments will be required to interpret the beam shear behavior, which depends on many parameters. For this reason, the use of advanced software whose verification is performed according to experimental data has become widespread. In this study, a numerical study was carried out on 36 different beam models using the ABAQUS finite element program to examine the effect of the shear span/effective depth (av/d) ratio, stirrup spacing (sw) and the angle of stirrup (α). The results showed that as the av/d increase, the behavior of a shear deficient beam tends to typical bending behavior. Although the effect of stirrup angle on shear capacity is quite high, stirrup angles of 30° and 60° give very similar results. The effect of stirrup spacing is quite limited at relatively high av/d. Stirrups with 90° do not contribute to ductility in beams with high av/d.

Effect of the GFRP wrapping on the shear and bending Behavior of RC beams with GFRP encasement

Yasin Onuralp Özkılıç,Lokman Gemi,Emrah Madenci,Ceyhun Aksoylu,İlker Kalkan 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.2

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

Numerical and analytical investigation of parameters influencing the behavior of shear beams strengthened by CFRP wrapping

Ceyhun Aksoylu,Yasin Onuralp Özkılıç,Şakir Yazman,Mohammed Alsdudi,Lokman Gemi,Musa Hakan Arslan 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.2

In this study, a parametric study was performed considering material properties of concrete, material properties of steel, the number of longitudinal reinforcement (reinforcement ratio), CFRP ply orientations, a number of layers as variables by using ABAQUS. Firstly, the parameters used in the Hashin failure criteria were verified using four coupon tests of CFRP. Secondly, the numerical models of the beams strengthened by CFRP were verified using five experimental data. Finally, eighty numerical models and eighty analytic calculations were developed to investigate the effects of the aforementioned variables. The results revealed that in the case of using fibrous polymer to prevent shear failure, the variables related to reinforced concrete significantly affected the behavior of specimens, whereas the variables related to CFRP composite have a slight effect on the behavior of the specimens. As a result of numerical analysis, while the increase in the longitudinal tensile and compression reinforcement, load bearing capacity increases between 23.6%-70.7% and 5.6%-12.2%, respectively. Increase in compressive strength (29 MPa to 35 MPa) leads to a slight increase in the load-carrying capacity of the specimens between 4.6% and 7.2%. However, the decrease in the compressive strength (29 MPa to 20 MPa) significantly affected (between 6.4% and 8.1% decrease observed) the behavior of the specimens. As the yield strength increases or decreases, the capacity of specimens increase approximately 27.1% or decrease 12.1%. The effects of CFRP ply orientation results have been obtained as a negligible well approximately 3.7% difference. An increasing number of CFRP layers leads to almost no effect (approximately 2.8%) on the behavior of the specimen. Finally, according to the numerical analysis, the ductility values obtained between 4.0 and 6.9 indicate that the beams have sufficient ductility capacity.

Free vibration analysis of open-cell FG porous beams: analytical, numerical and ANN approaches

Emrah Madenci,Yasin Onuralp Özkılıç 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.2

This paper constitutes an attempt to explore the influence of porosity on free vibration analysis of functionally graded (FG) beams with different boundary conditions using different efficient analytical and numerical approaches. The material properties of open-cell FG porous beams are estimated using a modified power-law with two different types of porosity distributions through the thickness direction of the FG beam namely even and non-even distributions. Hamilton’s principle is used to derive the equations of motion of the FG porous beam with high-order shear deformation theory. The state-space approach is utilized to solve the problem in the analytical solution section. In addition to the theoretical solution, a simulation based on a displacement type of finite element method (FEM) was utilized to verify the analytical solution. For this purpose, three-dimensional shell beams were modeled using ABAQUS for the solution of the vibration problem of the FG porous beam. Furthermore, the Artificial Neural Networks (ANNs) technique is used to predict the effects of porosity distributions, porosity coefficient, slenderness ratio and boundary conditions on natural frequency variations of porous FG beam. The ANNs technique allows for an investigation of the effects of various parameters, including beam characteristics, material properties, geometric details and porosity distributions.

Geopolymer concrete with high strength, workability and setting time using recycled steel wires and basalt powder

Ali İhsan Çelik,Yasin Onuralp Özkılıç 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.5

Geopolymer concrete production is interesting as it is an alternative to portland cement concrete. However, workability, setting time and strength expectations limit the sustainable application of geopolymer concrete in practice. This study aims to improve the production of geopolymer concrete to mitigate these drawbacks. The improvement in the workability and setting time were achieved with the additional use of NaOH solution whereas an increase in the strength was gained with the addition of recycled steel fibers from waste tires. In addition, the use of 25% basalt powder instead of fly ash and the addition of recycled steel fibers from waste tires improved its environmental feature. The samples with steel fiber ratios ranging between 0.5% and 5% and basalt powder of 25%, 50% and 75% were tested under both compressive and flexure forces. The compressive and flexural capacities were significantly enhanced by utilizing recycled steel fibers from waste tires. However, decreases in these capacities were detected as the basalt powder ratio increased. In general, as the waste wire ratio increased, the compressive strength gradually increased. While the compressive strength of the reference sample was 26 MPa, when the wire ratio was 5%, the compressive strength increased up to 53 MPa. With the addition of 75% basalt powder, the compressive strength decreases by 60%, but when the 3% wire ratio is reached, the compressive strength is obtained as in the reference sample. In the sample group to which 25% basalt powder was added, the flexural strength increased by 97% when the waste wire addition rate was 5%. In addition, while the energy absorption capacity was 0.66 kN in the reference sample, it increased to 12.33 kN with the addition of 5% wire. The production phase revealed that basalt powder and waste steel wire had a significant impact on the workability and setting time. Furthermore, SEM analyses were performed.

Buckling performance of pultruded glass fiber reinforced polymer profiles infilled with waste steel fiber reinforced concrete under axial compression

Emrah Madenci,Sabry Fayed,Walid Mansour,Yasin Onuralp Özkılıç 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.5

This study reports the results of a series of tests of pultruded glass fiber reinforced polymer (P-GFRP) box section composite profile columns, geometrically similar with/without concrete core, containing 0-1-2-3% steel fiber, with different lengths. The recycled steel wires were obtained from waste tyres. The effects of steel fiber ratio on the collapse and size effect of concrete filled P-GFRP columns under axial pressure were investigated experimentally and analytically. A total of 36 columns were tested under compression. The presence of pultruded profile and steel wire ratio were selected as the primary variable. The capacity of pultruded profiles with infilled concrete are averagely 9.3 times higher than the capacity of concrete without pultruded profile. The capacity of pultruded profiles with infilled concrete are averagely 34% higher than that of the pultruded profiles without infilled concrete. The effects of steel wire ratio are more pronounced in slender columns which exhibit buckling behavior. Moreover, the proposed analytical approach to calculate the capacity of P-GFRP columns successfully predicted the experimental findings in terms of both pure axial and buckling capacity.

Comparison of Turkish Steel Building Specifications, TS 648 and SDCCSS 2018

Mehmet Bakır Bozkurt,Abdulkerim Ergüt,Yasin Onuralp Özkılıç 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.4

This study presents similarities and differences between Turkish Building Code for Steel Structures, which are TS 648 and SDCCSS (Specification for Design, Calculation and Construction of Steel Structures) in terms of the design of the members. Hot-rolled I-shaped steel sections for symmetrical and U-shaped steel sections (i.e., channels) for monosymmetric sections were elaborated in detail. The design strength of tension members under tensile load, compression members under axial load and flexural members under flexure and shear were examined separately. Connection details for tension members, slenderness for compression members and distance between lateral supports for flexural members were considered as prime variables. Analysis results revealed the design strength of the tension members where at least one of the cross-sectional parts is not connected to the connection plates, I-shaped compression members where a slenderness ratio is below 39 (λ<39), U-shaped compression members and flexural members where Lb is between Lp and Lr (Lp<Lb≤Lr) designed based on TS 648 are greater than those designed based on SDCCSS 2018. Strength differences between the specification can reach 79% for tensile members, 13% for compression members and 9% for flexural members.

Lateral torsional buckling of doubly-symmetric steel cellular I-Beams

Mehmet Fethi Ertenli,Erdal Erdal,Alper Buyukkaragoz,Ilker Kalkan,Ceyhun Aksoylu,Yasin Onuralp Özkılıç 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.5

The absence of an important portion of the web plate in steel beams with multiple circular perforations, cellular beams, causes the web plate to undergo distortions prior to and during lateral torsional buckling (LTB). The conventional LTB equations in the codes and literature underestimate the buckling moments of cellular beams due to web distortions. The present study is an attempt to develop analytical methods for estimating the elastic buckling moments of cellular beams. The proposed methods rely on the reductions in the torsional and warping rigidities of the beams due to web distortions and the reductions in the weak-axis bending and torsional rigidities due to the presence of web openings. To test the accuracy of the analytical estimates from proposed solutions, a total of 114 finite element analyses were conducted for six different standard IPEO sections and varying unbraced lengths within the elastic limits. These analyses clearly indicated that the LTB solutions in the AISC 360- 16 and AS4100:2020 codes overestimate the buckling loads of cellular beams within elastic limits, particularly at shorter span lengths. The LDB solutions in the literature and the Eurocode 3 LTB solution, on the other hand, provided conservative buckling moment estimates along the entire range of elastic buckling.

Optimum amount of CFRP for strengthening shear deficient reinforced concrete beams

Lokman Gemi,Mohammed Alsdudi,Ceyhun Aksoylu,Şakir Yazman,Yasin Onuralp Özkılıç,Musa Hakan Arslan 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.6

The behavior of shear deficient under-balanced reinforced concrete beams with rectangular cross-sections, which were externally strengthened with CFRP composite along shear spans, was experimentally investigated under vertical load. One of the specimens represents a reference beam without CFRP strengthening and the other specimens have different width/strip spacing ratios (wf/sf). The optimum strip in terms of wf/sf, which will bring the beam behavior to the ideal level in terms of strength and ductility, was determined according to the regulations. When the wf/sf ratio exceeds 0.55, the behavior of the beam shifted from shear failure to bending failure. However, it has been observed that the wf/sf ratio should be increased up to 0.82 in order for the beam to reach sufficient shear reserve value according to the codes. It is also observed that the direction and weight of the CFRP composite are one of the most critical factors and 240 gr/m2 CFRP strips experienced sudden ruptures in the shear span after the cracking of the concrete. It is considered as a deficiency that the empirical shear capacity formulas given for the beams reinforced with CFRP in the regulations do not take into account both direction and weight of CFRP composites.