CFRP strengthening of steel beam curved in plan

Amir Hamzeh Keykha 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.5

Nowadays, one of the practical, fast and easy ways to strengthen steel elements is the use of Carbon Fiber Reinforced Polymer (CFRP). Most previous research in the CFRP strengthening of steel members has carried out on straight steel members. The main difference between horizontal curved beams and straight beams under vertical load is the presence of torsional moment in the horizontal curved beams. In the other words, the horizontal curved beams are analyzed and designed for simultaneous internal forces included bending moment, torsional moment, and shear force. The horizontal curved steel beams are usually used in buildings, bridges, trusses, and others. This study explored the effect of the CFRP strengthening on the behavior of the horizontal curved square hollow section (SHS) steel beams. Four specimens were analyzed, one non-strengthened curved steel beam as a control column and three horizontal curved steel beams strengthened using CFRP sheets (under concentrated load and uniform distributed load). To analyze the horizontal curved steel beams, three dimensional (3D) modeling and nonlinear static analysis methods using ANSYS software were applied. The results indicated that application of CFRP sheets in some specific locations of the horizontal curved steel beams could increase the ultimate capacity of these beams, significantly. Also, the results indicated when the horizontal curved steel beams were under distributed load, the increase rate in the ultimate capacity was more than in the case when these beams were under concentrated load.

Analysis of restrained heated steel beams during cooling phase

Guo-Qiang Li,Shi-Xiong Guo 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.3

Observations from experiments and real fire indicate that restrained steel beams have better fireresistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. However disgusting damages may occur in the beam-to-column connections, which is considered to be mainly caused by the enormous axial tensile forces in steel beams resulted from temperature decreasing after fire dies out. Over the past ten years, the behaviour of restrained steel beams subjected to fire during heating has been experimentally and theoretically investigated in detail, and some simplified analytical approaches have been proposed. While the performance of restrained steel beams during cooling has not been so deeply studied. For the safety evaluation and repair of steel structures against fire, more detailed investigation on the behaviour of restrained steel beams subjected to fire during cooling is necessary. When the temperature decreases, the elastic modulus and yield strength of steel recover, and the contraction force in restrained steel beams will be produced. In this paper, an incremental method is proposed for analyzing the behaviour of restrained steel beams subjected to cooling. In each temperature decrement, the development of deformation and internal forces of a restrained beam is divided into four steps, in order to consider the effect of the recovery of the elastic modulus and strength of steel and the contraction force generated by temperature decrease in the beam respectively. At last, the proposed approach is validated by FE method.

Yield Resistance and Ultimate Resistance of Steel Beam with Random Corrosion Damage

Zhang Jing-Zhou,He Ying-Hua,Zhang Wen-Jin,Zhang Ping,Wang Yuan-Zuo,LI Guo-qiang 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.3

This paper presents a numerical study on the yield resistance and ultimate resistance of steel beam with random corrosion damage. The corrosion is considered by introducing random cylindrical pits to the intact steel beam, in which the thickness of the beam, both at the section and along the length of the beam is reduced. Altogether 240 corroded beams are numerically studied, wherein the eff ects of corrosion ratio, corrosion diameter, corrosion depth and corrosion location on the yield resistance and ultimate resistance of steel beam are considered. It is found that for global corrosion scenario, when the corrosion ratio is 4.76%, 9.26%, 13.37%, 18.25%, 22.36%, and 25.76%, due to the random nature of corrosion, the reduction factors of ultimate resistance of steel beam range from 0.9–0.92, 0.81–0.86, 0.77–0.8, 0.71–0.76, 0.64–0.67, and 0.58–0.64, respectively. Moreover, when corrosion distributes only at the bottom fl ange or top fl ange of steel beam, the adverse eff ects of bottom fl ange corrosion and top fl ange corrosion on the resistance of steel beam are the same. The corrosion diameter and corrosion depth have limited eff ects on the resistance of steel beam. The relationship between the reduction factors for the yield resistance and ultimate resistance with the corrosion ratio of the beam is proposed. It is found that for the global corrosion case, the reduction factors of the yield resistance and ultimate resistance of the beam are linearly and negatively correlated with the corrosion ratio. For each 10% increase in the corrosion ratio, the reduction factor of yield resistance and ultimate resistance decrease by 18.9% and 15.1%, respectively. The resistances of the corroded beam with random corrosion pits and uniform corrosion are also compared. The results suggest that by using uniform corrosion model, the resistance of the corroded steel beam will be signifi cantly overestimated. When the corrosion ratio is about 14%, the overestimation on the ultimate resistance of steel beam by using uniform corrosion model is more than 10%.

Numerical investigation of SHS steel beam-columns strengthened using CFRP composite

Amir Hamzeh Keykha 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.5

Carbon Fiber Reinforced Polymer (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been done on steel beams and steel columns. No independent study, to the researcher’s knowledge, has studied the effect of CFRP strengthening on steel beam-columns, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel beam-columns. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel beam-columns, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine the ultimate load of SHS steel beam-columns, ten specimens, eight of which were strengthened with the different coverage length and with one and two CFRP layers, with two types of section (Type A and B) were analyzed. ANSYS was used to analyze the SHS steel beam-columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel beam-columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel beam-columns.

Use of steel fibers as transverse reinforcement in diagonally reinforced coupling beams with normal- and high-strength concrete

Jang, Seok-Joon,Jeong, Gwon-Young,Yun, Hyun-Do Elsevier 2018 Construction & building materials Vol.187 No.-

<P><B>Abstract</B></P> <P>This study investigates the effects of using steel fibers as transverse reinforcement on the seismic performance of diagonally reinforced coupling beams that are composed of normal- and high-strength concrete. Four types of coupling beams were fabricated and tested under quasi-static reversed cyclic loading. A normal-strength reinforced concrete (RC) coupling beam with the compressive strength of 40 MPa was designed with the full confinement of a beam section according to ACI 318-14. A second RC coupling beam specimen with the same reinforcement details and concrete with the compressive strength of 80 MPa was fabricated also to evaluate the effects of strength. In addition, steel fiber was used in an attempt to simplify the complex details of transverse reinforcements for diagonally RC coupling beams. To this end, two fiber volume fractions of 1.0% and 1.25% were used for 40 MPa and 80 MPa steel fiber-reinforced concrete (SFRC) coupling beams, respectively. Test results indicated that the shear strength of the coupling beams increased with an increase in compressive strength, whereas the energy dissipation capacity was similar for the normal- and high-strength concrete RC coupling beams. Furthermore, this study found that the inclusion of steel fiber prevented buckling of the diagonal steel rebar as well as provided additional transverse reinforcement. The overall performance, including strength, stiffness degradation, and the energy dissipation capacity, of the SFRC coupling beams was similar to that of the conventional concrete coupling beams. Comparisons of the conventional concrete and SFRC beam specimens indicate that the use of steel fiber allows for the simplification of transverse reinforcement construction details for diagonally reinforced coupling beams.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The inclusion of steel fibers improves flexural behavior and toughness of concrete. </LI> <LI> SFRC significantly contributed to prevent the buckling of the diagonal reinforcement. </LI> <LI> Using fibers as transverse reinforcement improves constructability of coupling beam. </LI> <LI> Shear strength is well predicted considering contribution of diagonal concrete strut. </LI> </UL> </P>

Numerical Analysis and Experimental Investigation on Behavior of Cold-Formed Steel Castellated Beam with Diamond Castellation

S. Prabhakaran,S. A. Maboob 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.3

The main purpose of the current research work is to achieve an economical cold formed steel castellated beam with diamond castellation with limited buckling. In this way, to study the behavior of cold formed steel castellated beam with diamond castellation by the provision of diff erent methods of placing the stiff eners for the sections is an main scope of the work. It can be achieved through this paper, which gives an Numerical, Analytical Study and Experimental investigation on the performance of cold-formed steel Castellated beams with Diamond Castellation shape. Perforations in web has been carried out to know its structural behaviour as simply supported beam under pure bending. The castellated steel beams with perforated web epitomize a new inventive which has occurred in the past span for the short- and medium length of beams. The Cold- Formed Steel provides a substantial weight reduction of these beams with castellation, compared to the hot-rolled beams. The Castellated Beam has made with 2 mm thickness CFS Steel, used all over the Beam. In the study, the Castellated Beam has been performed with three types of Stiff ener Designs at web of the Beam. Beam with intercept Stiff eners plates at web has used. Both stiff ened and unstiff ened Castellated beam (Beam with Parallel, Perpendicular and intercept Stiff eners) were tested for numerical and experimental Testings. Finally, numerical analysis using ABAQUS 6.11 results are evaluated and the experimental results were confi rmed with the results obtained from the fi nite element analysis. Based up on the numerical analysis and experimental investigation the diff erent failure and buckling modes of the proposed beams has been studied and the load carrying capacity of beams has been predicted.

Behavior of steel and concrete composite beams with a newly puzzle shape of crestbond rib shear connector: an experimental study

Van Phuoc Nhan Le,Duc Vinh Bui,Thi Hai Vinh Chu,김인태,안진희,Duy Kien Dao 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.6

The connector is the most important part of a composite beam and promotes a composite action between a steel beam and concrete slab. This paper presents the experiment results for three large-scale beams with a newly puzzle shape of crestbond. The behavior of this connector in a composite beam was investigated, and the results were correlated with those obtained from push-out-test specimens. Four-pointbending load testing was carried out on steel-concrete composite beam models to consider the effects of the concrete strength, number of transverse rebars in the crestbond, and width of the concrete slab. Then, the deflection, ultimate load, and strains of the concrete, steel beam, and crestbond; the relative slip between the steel beam and the concrete slab at the end of the beams; and the failure mechanism were observed. The results showed that the general behavior of a steel-concrete composite beam using the newly puzzle shape of crestbond shear connectors was similar to that of a steel-concrete composite beam using conventional shear connectors. These newly puzzle shape of crestbond shear connectors can be used as shear connectors, and should be considered for application in composite bridges, which have a large number of steel beams.

Experimental Evaluation of Joints Consisting of Parallel Perfobond Ribs in Steel-PSC Hybrid Beams

김상효,이찬구,Ariunzul Davaadorj,윤지현,원정훈 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.4

The objective of this paper is to estimate the structural capacity and application feasibility of joints with parallel perfobond ribs in steel-PSC (prestressed concrete) hybrid beams. In order to investigate the joints, two steel-PSC hybrid beams of 8 m length are fabricated, and experimental tests are performed. The hybrid beams consist of a steel beam in the center, PSC beams at both ends, and joints connecting the steel beam and the PSC beams. In the joints, perfobond ribs are used as shear connectors in place of studs which are generally used. The parallel perfobond ribs are attached to the steel plates horizontally and vertically to assess joint performance under both flexural moments and shear forces. The test results reveal that the failure of hybrid beams occurs at the PSC region near the interface between the PSC component and the joint. No joint failure is observed in the test beams up to the fracture load stage. In addition, the test beams show sufficient ductility by virtue of the arrangement of adequate reinforcements, even though perfobond ribs are considered to be stiff shear connectors. Therefore, it is concluded that the joint with parallel perfobond ribs is an applicable system to utilize in steel-PSC hybrid beams. In addition, the perfobond ribs can be an alternative to stud shear connectors in joints of hybrid beams.

A Numerical Investigation on Restrained High Strength Q460 Steel Beams Including Creep Eff ect

Wei-Yong Wang,Linbo Zhang,Pingzhao He 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5

Most of previous studies on fi re resistance of restrained steel beams neglected creep eff ect due to lack of suitable creep model. This paper presents a fi nite element model (FEM) for accessing the fi re resistance of restrained high strength Q460 steel beams by taking high temperature Norton creep model of steel into consideration. The validation of the established model is verifi ed by comparing the axial force and defl ection of restrained beams obtained by fi nite element analysis with test results. In order to explore the creep eff ect on fi re response of restrained Q460 steel beams, the thermal axial force and defl ection of the beams are also analyzed excluding creep eff ect. Results from comparison infer that creep plays a crucial role in fi re response of restrained steel beam and neglecting the eff ect of creep may lead to unsafe design. A set of parametric studies are accomplished by using the calibrated FEM to evaluate the governed factors infl uencing fi re response of restrained Q460 steel beams. The parametric studies indicate that load level, rotational restraint stiff ness, span–depth ratio, heating rate and temperature distribution pattern are key factors in determining fi re resistance of restrained Q460 steel beam. A simplifi ed design approach to determine the moment capacity of restrained Q460 steel beams is proposed based on the parametric studies by considering creep eff ect.

Flexural behaviour of Steel Timber Composite (STC) beams

Ruyuan Yang,Haitao Li,Rodolfo Lorenzo,Youfu Sun,Mahmud Ashraf 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2

Structural performance of a new type of lightweight steel-timber composite (STC) beam has been investigated by conducting four-point bending tests on 21 specimens. This paper presents key findings on its structural performance parameters such as failure modes, load-deflection response, load-slip response, load-strain response, and the ultimate bending capacity by grouping 21 specimens into 7 subgroups based on various geometric characteristics. In the proposed STC beams, glulam slabs were connected to the steel beams using high-strength bolts, and the effect of different thickness and width of glulam slabs on the structural behaviour of STC beams were carefully investigated. In addition, the effective bending stiffness, deflection, and bending capacity of the STC beams were theoretically calculated based on elastic theory and compared with experimental values. For all considered specimens, timber slabs and steel beams showed good composite action. Increasing the thickness and width of the timber slabs can effectively limit the lateral deformation of the specimens, improve the bending capacity of the specimens, and provides a secant stiffness to the STC beams. It was observed that for the whole cross section of STC beams, the plane section assumption is not applicable, but the strains on timber and steel seemed to satisfy the plane section assumption individually. γ (Gamma) method has been observed to better reflect the deformation capacity of STC beams. Analytical equations were derived to predict the elastic bending capacity of STC beams, and comparison between theoretical and experimental values showed good agreement.