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CONTENTS
Volume 45, Number 1, October10 2022
 

Abstract
In the structural analysis of steel frames, joints are generally considered as rigid or hinged considering their moment transfer ability. However, the first studies conducted with the beginning of the 20th century showed that the joints do not actually fit these two definitions. In reality, a joint behaves between these two extreme points and is called semi-rigid. Including the actual state of the joint in the structural analysis provides significant economic advantages, so the subject is an intense field of study today. However, it does not find enough application area in practice. For this reason, a large-scale literature published from the first studies on the subject to the present has been examined within the scope of the study. Three important points have been identified in order to examine a joint realistically; modelling the load-displacement relationship, performing the structural analysis and how to design. Joint modelling methods were grouped under 7 main headings as analytical, empirical, mechanical, numerical, informational, hybrid and experimental. In addition to the moment-rotation, other important external load effects like axial force, shear and torsion were considered. Various evaluations were made to expand the practical application area of semirigid connections by examining analysis methods and design approaches. Dynamic behaviour was also included in the study, and besides column-beam connections, other important connection types such as beam-beam, column-beam-cross, base connection were also examined in this paper.

Key Words
semi-rigid; steel connection; moment-rotation; frame analysis; steel design; joint modelling

Address
Huseyin Kursat Celik:Department of Civil Engineering, the Graduate School of Natural and Applied Sciences, Dokuz Eylul University,
Tinaztepe Campus, Izmir, Turkey

Gokhan Sakar:Department of Civil Engineering, Faculty of Engineering, Dokuz Eylul University, Tinaztepe Campus, Izmir, Turkey

Abstract
This paper presents experimental and analytical studies of eccentrically loaded concrete-filled double steel (CFDST) and concrete-filled double skin tube (DCFST) columns having outer stainless steel tube. Eighteen CFDST and DCFST column specimens were manufactured and tested to examine the strength and load-deflection responses. In the study, the main parameters were concrete strength, load eccentricity, cross section and slenderness. The strengths, load-deflection diagrams and failure patterns of the columns were observed. In addition, the tested CFDST and DCFST columns were analyzed to attain the capacity and load versus lateral deflection responses. The obtained theoretical results were compared with the test results. A parametric study was also performed to research the effects of the ratio of eccentricity (e/Ho) slenderness ratio (L/r), Ho/to ratio, Hi/ti ratio and the concrete compressive strength on the behavior of columns. In this work, the obtained results indicated that the ductility and capacity of columns were affected by cross section, concrete strength, steel strength, loading eccentricity and slenderness.

Key Words
carbon steel tube; concrete-filled steel tube; double skin; double steel; stainless steel tube

Address
Serkan Tokgoz and Sedat Karaahmetli:1Department of Civil Engineering, Adana Alparslan Turkes Science and Technology University, Adana 01250, Turkey

Cengiz Dundar:Department of Civil Engineering, Toros University, Mersin 33340, Turkey

Abstract
This research investigates a rotary disk with variable cross-section and incompressible hyperelastic material with functionally graded properties in large hyperelastic deformations. For this purpose, a power relation has been used to express the changes in cross-section and properties of hyperelastic material. So that (m) represents the changes in cross-section and (n) represents the manner of changes in material properties. The constants used for hyperelastic material have been obtained from experimental data. The obtained equations have been solved for different m, n, and (angular velocity) values, and the values of radial stresses, tangential stresses, and elongation have been compared. The results show that m and n have a significant impact on disk behavior, so the expected behavior of the disk can be obtained by an optimal selection of these two parameters.

Key Words
deformation demand; earthquake resistant design philosophy; limit states; structural damage states; levels of earthquake shaking

Address
Ahmad Soleimani:Department of Mechanical Engineering, University of Jiroft, Jiroft, Iran

Mohsen Mahdavi Adeli:Department of Mechanical Engineering, Sousangerd Branch, Islamic Azad University, Sousangerd, Iran

Farshad Zamani:Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

Hamid Haghshenas Gorgan:4Engineering Graphics Center, Sharif University of Technology, Tehran, Iran

Abstract
This paper presents the axial compression behavior of partially encased composite (PEC) columns using H-shaped structural steel. In the experimental program, a total of eight PEC columns with H-shaped steel sections of different flange and web slenderness ratios were tested to investigate the interactive mechanism between steel and concrete. The test results showed that the PEC columns could sustain the load well beyond the peak load provided that the flange slenderness ratio was not greater than five. In addition, the previous analytical model was extended to predict the axial load-strain relationships of the PEC columns with H-shaped steel sections. A good agreement between the predicted load-strain relationships and test data was observed. Using the analytical model, the effects of compressive strength of concrete (21 to 69 MPa), yield strength of steel (245 to 525 MPa), slenderness ratio of flange (4 to 10), and slenderness ratio of web (10 to 25) on the interactive mechanism (Kh = confinement factor for highly confined concrete and Kw = reduction factor for steel web) and ductility index (DI = ratio between strain at peak load and strain at proportional load) were assessed. The numerical results showed that the slenderness of steel flange and yield strength of steel significantly influenced the compression behavior of the PEC columns.

Key Words
analytical model; composite column; compressive strength; confined concrete; partial encasement

Address
Papan Bangprasit, Worakarn Anuntasena and Akhrawat Lenwari:Composite Structures Research Unit, Department of Civil Engineering, Faculty of Engineering,
Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok, Thailand 10330

Abstract
In this paper, buckling and free vibration of imperfect, functionally graded beams, including porosities, are investigated, using a higher order shear strain theory. Due to defects during the manufacturing process, micro porosities may appear in the material, hence the appearance of this imperfection in the structure. The material properties of the beams are assumed to vary regularly, with power and sigmoid law, in the direction of thickness. A novel porosity distribution affecting the functionally graded volume fraction is presented. For the compact formulation used for cementite-based materials and already used in P-FGM, we have adapted it for the distribution of S-FGM. The equations of motion in the FG beam are derived using Hamilton's principle. The boundary conditions for beam FG are assumed to be simply supported. Navier's solution is used to obtain the closed form solutions of the FG beam. The numerical results of this work are compared with those of other published research to verify accuracy and reliability. The comparisons of different shear shape functions, the influence of porosity, thickness and inhomogeneity parameters on buckling and free vibration of the FG beam are all discussed. It is established that the present work is more precise than certain theories developed previously.

Key Words
buckling; free vibration; functionally graded beams; high order shear deformation theory; porosity coefficient; porosity

Address
Riadh Bennai:1)Department of Civil Engineering, Faculty of Civil Engineering and Architecture, University Hassiba Benbouali of Chlef, Algeria
2)Laboratory of Structures, Geotechnics and Risks, Department of Civil Engineering, Hassiba Benbouali University of Chlef, Algeria

Redhwane Ait Atmane:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Fabrice Bernard:LGCGM, IINSA RENNES France

Mokhtar Nebab:1)Laboratory of Structures, Geotechnics and Risks, Department of Civil Engineering, Hassiba Benbouali University of Chlef, Algeria
2)Department of Civil Engineering, Faculty of Sciences, University of M'Hamed BOUGARA Boumerdes, Algeria

Noureddine Mahmoudi:Department of mechanical engineering, university of Saida, Algeria

Hassen Ait Atmane:1)Department of Civil Engineering, Faculty of Civil Engineering and Architecture, University Hassiba Benbouali of Chlef, Algeria
2)Laboratory of Structures, Geotechnics and Risks, Department of Civil Engineering, Hassiba Benbouali University of Chlef, Algeria

Salem Mohammed Aldosari:1)Enhanced Composite and Structures Centre, School of Aerospace, Transport, and Manufacturing, Cranfield University,
Cranfield MK43 0AL, UK
2)National Center for Aviation Technology, King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia

Abdelouahed Tounsi:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2)YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea


Abstract
Timber is one of the few natural, renewable building materials and glulam is a type of engineering wood product. In the present work, timber-based braces are applied for retrofitting midrise Special Moment Resisting Frame (SMRF) using two types of timber base braces (Timber base glulam, and hybrid Timber-Steel-BRB) as alternatives for retrofitting by traditional steel bracings. The improving effects of adding the bracings to the SMRF on seismic characteristics of the frame are evaluated using load-bearing capacity, energy dissipation, and story drifts of the frame. For evaluating the retrofitting effects on the seismic performance of SMRF, a five-story SMRF is considered unretofitted and retrofitted with steel-hollow structural section (HSS) brace, Glued Laminated Timber (Glulam) brace, and hybrid Timber-Steel BRB. Using OpenSees structural analyzer, the performance are investigated under pushover, cyclic, and incremental loading. Results showed that steel-HSS, timber base Glulam, and hybrid timber-steel BRB braces have more significant roles in energy dissipation, increasing stiffness, changing capacity curves, reducing inter-story drifts, and reducing the weight of the frames, compared by steel bracing. Results showed that Hybrid BRB counteract the negative post-yield stiffness, so their use is more beneficial on buildings where P-Delta effects are more critical. It is found that the repair costs of the buildings with hybrid BRB will be less due to lower residual drifts. As a result, timber steel-BRB has the best energy dissipation and seismic performance due to symmetrical and stable hysteresis curves of buckling restrained braces that can experience the same capacities in tension and compression.

Key Words
cyclic analysis; incremental dynamic analysis; OpenSees; pushover analysis; steel moment frame; Timber Base Bracing Alternatives

Address
Ainullah-Mirzazadah and Saeed-Reza Sabbagh-Yazdi:Civil Engineering Department, K. N. Toosi University of Technology, No.1346, Vali Asr Street, Mirdamad Intersection, Tehran, Iran

Abstract
The seismic performance of the reinforced concrete (RC) special-shaped column to steel beam connections with steel jacket used in the RC column to steel beam fabricated frame structures was investigated in this study. The three full-scale specimens were subjected to cyclic loading. The failure mode, ultimate bearing capacity, shear strength capacity, stiffness degradation, energy dissipation capacity, and strain distribution of the specimens were studied by varying the steel jacket thickness parameters. Test results indicate that the RC special-shaped column to steel beam connection with steel jacket is reliable and has excellent seismic performance. The hysteresis curve is full and has excellent energy dissipation capacity. The thickness of the steel jacket is an important parameter affecting the seismic performance of the proposed connections, and the shear strength capacity, ductility, and initial stiffness of the specimens improve with the increase in the thickness of the steel jacket. The calculation formula for the shear strength capacity of RC special-shaped column to steel beam connections with steel jacket is proposed on the basis of the experimental results an

Key Words
numerical simulation; precast RC special-shaped column; prefabricated joint; RCS fabricated frame structure; seismic behavior; shear capacity; steel jacket

Address
Jiashu Hao and Xingqian Li:School of Civil Engineering, Tianjin University, Tianjin, China

Qingying Ren:China Architecture Design & Res Grp, Beijing, China

Xizhi Zhang:1)Tianjin University Research Institute of Architectural Design & Urban planning, Tianjin, China
2)Key Laboratory of Civil Engineering Structures and New Materials Laboratory, Tianjin University, Tianjin, China

Yongjun Ding and Shaohua Zhang:Tianjin University Research Institute of Architectural Design & Urban planning, Tianjin, China

Abstract
Due to the complexity of the structure and the limits of classical SEA, a combined SEA approach is employed, with angle-dependent SEA in the low- and mid-frequency ranges and advanced SEA (ASEA) considering indirect coupling in the high-frequency range. As an important component of the steel box girder, the dynamic response of an L-junction periodic ribbed plate is calculated first by the combined SEA and validated by the impact hammer test and finite element method (FEM). Results show that the indirect coupling due to the periodicity of stiffened plate is significant at high frequencies and may cause the error to reach 38.4 dB. Hence, the incident bending wave angle cannot be ignored in comparison to classical SEA. The combined SEA is then extended to investigate the vibration properties of the steel box girder. The bending wave transmission study is likewise carried out to gain further physical insight into indirect coupling. By comparison with FEM and classical SEA, this approach yields good accuracy for calculating the dynamic responses of the steel box girder made of periodic ribbed plates in a wide frequency range. Furthermore, the influences of some important parameters are discussed, and suggestions for vibration and noise control are provided.

Key Words
bending wave; periodic ribbed plate; SEA; steel box girder; vibration

Address
Hao Luo, Zhiyang Cao:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China

Xun Zhang:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
2)MOE Key Laboratory of High-Speed Railway Engineering, Southwest Jiaotong University, Chengdu 610031, China

Cong Li:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China

Derui Kong:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China

Abstract
Steel fiber composite bar (SFCB) is a novel type of reinforcement, which has good ductility and durability performance. Due to the unique pseudo strain hardening tensile behavior of SFCB, different flexural behavior is expected of SFCB reinforced concrete (SFCB-RC) beams from traditional steel bar reinforced concrete (S-RC) beams and FRP bar reinforced concrete (F-RC) beams. To investigate the flexural behavior of SFCB-RC beam, four points bending tests were carried out and different flexural behaviors between S/F/SFCB-RC beams were discussed. An flexural analytical model of SFCB-RC beams is proposed and proved by the current and existing experimental results. Based on the proposed model, the influence of the fiber volume ratio R of the SFCB on the flexural behavior of SFCB-RC beams is discussed. The results show that the proposed model is effective for all S/F/SFCB-RC flexural members. Fiber volume ratio R is a key parameter affecting the flexural behavior of SFCB-RC. By controlling the fiber volume ratio of SFCB reinforcements, the flexural behavior of the SFCB-RC flexural members such as bearing capacity, bending stiffness, ductility and repairability of SFCB-RC structures can be designed.

Key Words
concrete flexural member; fiber volume ratios; flexural behavior; GFRP; steel fiber composite bar

Address
Jia-Xiang Lin, Yong-Jian Cai, Ze-Ming Yang, Shu-Hua Xiao, Zhan-Biao Chen, Li-Juan Li,
Yong-Chang Guo and Fei-Fei Wei:School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, China

Abstract
This study assessed the compressive and tensile strengths and modulus of elasticity of waste polyethylene terephthalate (PET) using the ASTM standard tests. In addition, short carbon and glass fibers were mixed with waste PET to examine the improvements in ductility and strength during compression. The bonding was examined via field-emission scanning electron microscopy. The strength degradation of the waste PET tested under UV was 40–50%. However, it had a compressive strength of 32.37 MPa (equivalent to that of concrete), tensile strength of 31.83 MPa (approximately ten times that of concrete), and a unit weight of 12–13 kN/m3 (approximately half that of concrete). A finite element analysis showed that, compared with concrete, a waste PET pile foundation can support approximately 1.3 times greater loads. Mixing reinforcing fibers with waste PET further mitigated this, thereby extending ductility. Waste PET holds excellent potential for use in foundation piles, especially while mitigating brittleness using short reinforcing fibers and avoiding UV degradation.

Key Words
finite element analysis; recycled thermoplastics; short fiber; waste polyethylene terephthalate

Address
Hongseok Jang:Department of Architectural Engineering, Innovative research and education center for integrated bioactive materials-BK21 FOUR,
Jeonbuk National University, 567 Baekje-daero, deokjin-gu, Jeonju 54896, Republic of Korea

Segwan Seo and Daesung Cho:Department of Research institution, ZIAN Co. Ltd., Wanju 55338, Republic of Korea

Abstract
This study assessed the compressive and tensile strengths and modulus of elasticity of waste polyethylene terephthalate (PET) using the ASTM standard tests. In addition, short carbon and glass fibers were mixed with waste PET to examine the improvements in ductility and strength during compression. The bonding was examined via field-emission scanning electron microscopy. The strength degradation of the waste PET tested under UV was 40–50%. However, it had a compressive strength of 32.37 MPa (equivalent to that of concrete), tensile strength of 31.83 MPa (approximately ten times that of concrete), and a unit weight of 12–13 kN/m3 (approximately half that of concrete). A finite element analysis showed that, compared with concrete, a waste PET pile foundation can support approximately 1.3 times greater loads. Mixing reinforcing fibers with waste PET further mitigated this, thereby extending ductility. Waste PET holds excellent potential for use in foundation piles, especially while mitigating brittleness using short reinforcing fibers and avoiding UV degradation.

Key Words
finite element analysis; recycled thermoplastics; short fiber; waste polyethylene terephthalate

Address
Hongseok Jang:Department of Architectural Engineering, Innovative research and education center for integrated bioactive materials-BK21 FOUR,
Jeonbuk National University, 567 Baekje-daero, deokjin-gu, Jeonju 54896, Republic of Korea

Segwan Seo and Daesung Cho:Department of Research institution, ZIAN Co. Ltd., Wanju 55338, Republic of Korea

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