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CONTENTS
Volume 50, Number 5, March 10 2024
 

Abstract
A temperature-dependent generalized thermoelasticity is constructed in the context of a new consideration of the multi-phase-lags model. The theory is then adopted to study wave propagation in anisotropic homogenous generalized magnetothermoelastic medium under the influence of gravity whose boundary is subjected to thermal and mechanical loading. The basic equations of the problem are solved by using normal mode analysis. The numerical quantities of physical interest are obtained and depicted graphically. Some comparisons of the results are shown in figures to study the effects of the magnetic field, temperature discrepancy, and the gravity field.

Key Words
magnetic field; microtemperatures; multi-phase-lags theory; temperature-dependent properties

Address
Samia M. Said:Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Abstract
This paper describes the experimental and numerical investigations of octagonal Concrete-Filled Double Skinned Steel Tube (CFDST) short columns under the influence of various internal sizes of the circular and square steel tubes, with constant cross-sectional dimensions of the external octagonal steel tube under concentric loading. The non-linear finite element analysis of octagonal CFDST columns was executed using the ABAQUS to forecast and compare the axial compression behavior influenced by the various sizes of internal circular and square steel tubes. The study shows that the axial compressive strength and ductility of octagonal CFDST columns were significantly influenced by various internal dimensions of the circular and square steel tubes with the strengths of constituent materials.

Key Words
ABAQUS; axial response; composite column; finite element analysis; octagonal CFDST column; sandwiched concrete

Address
Manigandan R:Department of Civil Engineering, Saveetha School of Engineering,
Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, 602 105, India

Abstract
Cold-formed steel (CFS) is a popular choice for construction due to its low cost, durability, sustainability, resistance to high environmental and seismic pressures, and ease of installation. The beam-column connections in residential and mediumrise structures are formed using self-drilling screws that connect two CFS channel sections and a gusset plate. In order to increase the moment capacity of these CFS screwed beam-column connections, stiffeners are often placed on the web area of each single channel. However, there is limited literature on studying the effects of stiffeners on the moment capacity of CFS screwed beam-column connections. Hence, this paper proposes a new test approach for determining the moment capacity of CFS screwed beam-column couplings. This study describes an experimental test programme consisting of eight novel experimental tests. The effect of stiffeners, beam thickness, and gusset plate thickness on the structural behaviour of CFS screwed beam-column connections is investigated. Besides, nonlinear elasto-plastic finite element (FE) models were developed and validated against experimental test data. It found that there was reasonable agreement in terms of moment capacity and failure mode prediction. From the experimental and numerical investigation, it found that the increase in gusset plate or beam thickness and the use of stiffeners have no significant effect on the structural behaviour, moment capacity, or rotational capacity of joints exhibiting the same collapse behaviour; however, the capacity or energy absorption capacities have increased in joints whose failure behaviour varies with increasing thickness or using stiffeners. Besides, the thickness change has little impact on the initial stiffness.

Key Words
complex networks; mathematical simulation; mechanical behavior; nanotechnology

Address
Merve Sagiroglu Maali and Mahyar Maali:1)Civil Engineering Department, Erzurum Technical University, Erzurum, Turkey
2)Maali Çelik Ar-Ge Dan

Abstract
This paper presents an experimental investigation into the progressive collapse behavior of composite steel-concrete frames under various column removal scenarios. This study involves testing two two-bay, two-story composite frames featuring CFST columns and profiled steel decking composite slabs. Two removal scenarios, involving the corner column and middle column, are examined. The paper reports on the overall and local failure modes, vertical force-deformation responses, and strain development observed during testing. Findings indicate that structural failure initiates due to fracture and local buckling of the steel beam. Moreover, the collapse resistance and ductility of the middle column removal scenario surpass those of the corner column removal scenario. Subsequent numerical analysis reveals the significant contribution of the composite slab to collapse resistance and capacity. Additionally, it is found that horizontal boundary conditions notably influence the collapse resistance in the middle column removal scenario only. Finally, the paper proposes a simplified calculation method for collapse resistance, which yields satisfactory predictions.

Key Words
experimental study; mechanism analysis; progressive collapse; simplified calculation; steel-concrete composite substructure

Address
Jing-Xuan Wang and Yong Yang:School of Civil Engineering, Lanzhou University of Technology, Lanzhou 730050, China

Ya-Jun Shen:School of Civil Engineering, Dalian University of Technology, Dalian 116024, China

Kan Zhou:School of Built Environment, Engineering and Computing, Leeds Beckett University, City Campus, Leeds, LS1 3HE, UK

Abstract
In this study a steel moment frame system to be installed on the exterior surface of an existing structure is proposed as a seismic retrofit device. The seismic performance of the retrofit system was investigated by installing it on the exterior of a single story single bay reinforced concrete frame and testing it under cyclic loading. The cyclic loading test results indicated that the steel frame significantly enhanced the strength and ductility of the bare structure. Finite element analysis was carried out to validate the test results, and it was observed that there was good agreement between the two results. An analytical model was developed in order to apply the retrofit system to an example structure subjected to seven mainshock-aftershock sequential earthquake records. It was observed that the model structure was severely damaged due to the mainshock earthquakes, and the seismic response of the model structure increased significantly due to the subsequent aftershock earthquakes. The seismic retrofit of the model structure using the proposed steel frame turned out to be effective in decreasing the seismic response below the given limit state.

Key Words
cyclic test; mainshock-aftershock; non-linear dynamic analysis; seismic retrofit; slit dampers; steel frame

Address
Michael Adane, Seungho Chun and Jinkoo Kim:Department of Global Smart City, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, Korea

Hyungoo Kang: Decomissioning Waste R&D Team, Korea Radioactive Waste Agency (KORAD), 168, Gajeong-ro, Yuseong-gu, Daejeon, Korea 34129

Abstract
This paper presents a novel finite element model for the free vibration analysis of variable-thickness functionally graded porous (FGP) microplates resting on Pasternak's medium in the hygro-thermal environment. The governing equations are established according to refined higher-order shear deformation plate theory (RPT) in construction with the modified couple stress theory. For the first time, three-node triangular elements with twelve degrees of freedom for each node are developed based on Hermitian interpolation functions to describe the in-plane displacements and transverse displacements of microplates. Two laws of variable thickness of FGP microplates, including the linear law and the nonlinear law in the x-direction are investigated. Effects of thermal and moisture changes on microplates are assumed to vary continuously from the bottom surface to the top surface and only cause tension loads in the plane, which does not change the material's mechanical properties. The numerical results of this work are compared with those of published data to verify the accuracy and reliability of the proposed method. In addition, the parameter study is conducted to explore the effects of geometrical and material properties such as the changing law of the thickness, length-scale parameter, and the parameters of the porosity, temperature, and humidity on the free vibration response of variable thickness FGP microplates. These results can be applied to design of microelectromechanical structures in practice.

Key Words
hygro-thermal environment; modified couple stress theory; refined higher-order shear deformation plate theory; triangular element; variable-thickness functionally graded porous microplates

Address
Quoc-Hoa Pham and Phu-Cuong Nguyen:Advanced Structural Engineering Laboratory, Department of Structural Engineering, Faculty of Civil Engineering,
Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam

Van-Ke Tran:Department of Mechanics, Le Quy Don Technical University, Hanoi, Vietnam

Abstract
In this paper, a Guided Simulated Annealing (GSA) algorithm is presented to optimize 2D and 3D steel frames against Progressive Collapse. Considering the nature of structural optimization problems, a number of restrictions and improvements have been applied to the decision mechanisms of the algorithm without harming the randomness. With these improvements, the algorithm aims to focus relatively on the flawed variables of the analyzed frame. Besides that, it is intended to be more rational by instituting structural constraints on the sections to be selected as variables. In addition to the LRFD restrictions, the alternate path method with nonlinear dynamic procedure is used to assess the risk of progressive collapse, as specified in the US Department of Defense United Facilities Criteria (UFC) Design of Buildings to Resist Progressive Collapse. The entire optimization procedure was carried out on a C# software that supports parallel processing developed by the authors, and the frames were analyzed in SAP2000 using OAPI. Time history analyses of the removal scenarios are distributed to the processor cores in order to reduce computational time. The GSA produced 3% lighter structure weights than the SA (Simulated Annealing) and 4% lighter structure weights than the GA (Genetic Algorithm) for the 2D steel frame. For the 3D model, the GSA obtained 3% lighter results than the SA. Furthermore, it is clear that the UFC and LRFD requirements differ when the acceptance criteria are examined. It has been observed that the moment capacity of the entire frame is critical when designing according to UFC.

Key Words
optimization; progressive collapse; simulated annealing; steel structures

Address
Bilal Tayfur:Department of Civil Engineering, Bayburt University, Bayburt, Turkey

Ayse T. Daloglu:Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
In this study, aluminum lathe waste was used by replacing aggregates in certain proportions in order to obtain expansive concrete using recycled materials. For this reason, five different aluminum wastes of 1%, 2%, 3%, 4% and 5% were selected and also reference without aluminum waste was produced. Based on the mechanical tests conducted, which included slump, compression, splitting tensile, and flexural tests, it was evident that the workability of the material declined dramatically once the volume ratio of aluminum exceeded 2%. As determined by the compressive strength test (CST), the CS of concrete (1% aluminum lathe wastes replaced with aggregate) was 11% reducer than that of reference concrete. It was noted that the reference concrete's CS values, which did not include aluminum waste, were greater than those of the concrete that contained 5% aluminum. When comparing for splitting tensile strength (STS), it was observed that the results of STS generally follow the parallel inclination as the CS. The reduction in these strengths when 1% aluminum is utilized is less than 10%. These ratios modified 18% when flexural strength (FS) is considered. Therefore, 1% of aluminum waste is recommended to obtain expansive concrete with recycled materials considering minimum loss of strength. Moreover, Scanning Electron Microscope (SEM) analysis was performed and the results also confirm that there was expansion in the aluminum added concrete. The presence of pores throughout the concrete leads to the formation of gaps, resulting in its expansion. Additionally, for practical applications, basic equations were developed to forecast the CS, STS, and FS of the concrete with aluminum lathe waste using the data already available in the literature and the findings of the current study. In conclusion, this study establishes that aluminum lathe wastes are suitable, readily available in significant quantities, locally sourced eco-materials, cost-effective, and might be selected for construction using concrete, striking a balance among financially and ecological considerations.

Key Words
aluminum lathe waste; compressive strength; flexural strength; scanning electron microscope; splitting tensile strength

Address
Yasin Onuralp Ozkilic: 1)Necmettin Erbakan University, Faculty of Engineering, Department of Civil Engineering, Konya, Turkey 2)Department of Civil Engineering, Lebanese American University, Byblos 1102-2801, Lebanon

Ozer Zeybek: Mugla Sitki Kocman University, Faculty of Engineering, Department of Civil Engineering, Mugla, 48000, Turkey

Ali ihsan Celik: Tomarza Mustafa Akincioglu Vocational School, Department of Construction, Kayseri University, Kayseri, 38940, Turkey

Essam Althaqafi: Civil Engineering Department, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia

Md Azree Othuman Mydin: School of Housing, Building and Planning, Universiti Sains Malaysia, 11800, Penang, Malaysia

Anmar Dulaimi: 1)College of Engineering, University of Kerbala, Karbala, 56001, Iraq 2)College of Engineering, University of Warith Al-Anbiyaa, Karbala 56001, Iraq

Memduh Karalar: Faculty of Engineering, Department of Civil Engineering, Zonguldak Bulent Ecevit University, Zonguldak 67100, Turkey

P. Jagadesh: Department of Civil Engineering, Coimbatore Institute of Technology, Coimbatore, India


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