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CONTENTS
Volume 51, Number 3, May 10 2024
 

Abstract
For several reasons, cold-formed steel (CFS) beams are often manufactured with holes. Nevertheless, because of holes, the reduction in the web area causes a decrease in the bending strength. Edge stiffeners are presently added around the holes to improve the bending strength of flexural members. Therefore, this research studies CFSZ-beams with stiffened holes and investigates how edge stiffener affects bending strength and failure modes. Nonlinear analysis was carried out using ABAQUS software and the developed finite element (FE) model was verified against tests from previous studies. Using the verified FE model, a parametric study of 104 FE models was conducted to investigate the influence of key parameters on bending strength of Z- sections. The results indicated that the effect of holes is less noticeable in very thin Z-sections. Moreover, adding edge stiffeners around the holes improves the flexural capacity of Z-beams and sometimes restores the original bending capacity. Because the computational techniques used to solve the CFS buckling mode with stiffened holes are still unclear, a numerical method using constrained and unconstrained finite strip method (CUFSM) software was proposed to predict the elastic distortional buckling moment for a wide variety of CFSZ-sections with stiffened holes. A numerical method with two procedures was applied and validated. Upon comparison, the numerical method accurately predicted the distortional buckling moment of CFS Z-sections with stiffened holes.

Key Words
Cold-Formed Steel (CFS); Direct Strength Method (DSM); distortional buckling; flexural strength; stiffened holes

Address
Nasam S. Khater, Mahmoud H. El-Boghdadi and Nashwa M. Yossef:Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt

Abstract
For several reasons, cold-formed steel (CFS) beams are often manufactured with holes. Nevertheless, because of holes, the reduction in the web area causes a decrease in the bending strength. Edge stiffeners are presently added around the holes to improve the bending strength of flexural members. Therefore, this research studies CFSZ-beams with stiffened holes and investigates how edge stiffener affects bending strength and failure modes. Nonlinear analysis was carried out using ABAQUS software and the developed finite element (FE) model was verified against tests from previous studies. Using the verified FE model, a parametric study of 104 FE models was conducted to investigate the influence of key parameters on bending strength of Z- sections. The results indicated that the effect of holes is less noticeable in very thin Z-sections. Moreover, adding edge stiffeners around the holes improves the flexural capacity of Z-beams and sometimes restores the original bending capacity. Because the computational techniques used to solve the CFS buckling mode with stiffened holes are still unclear, a numerical method using constrained and unconstrained finite strip method (CUFSM) software was proposed to predict the elastic distortional buckling moment for a wide variety of CFSZ-sections with stiffened holes. A numerical method with two procedures was applied and validated. Upon comparison, the numerical method accurately predicted the distortional buckling moment of CFS Z-sections with stiffened holes.

Key Words
Cold-Formed Steel (CFS); Direct Strength Method (DSM); distortional buckling; flexural strength; stiffened holes

Address
Nasam S. Khater, Mahmoud H. El-Boghdadi and Nashwa M. Yossef:Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt

Abstract
Thirteen self-compacting recycled concrete filled aluminium tubular (SCRCFAT) columns were tested under concentric compression loads. The effects of the replacement ratio of the recycled concrete aggregate (RCA) and steel fibre (SF) reinforcement on the structural performance of the SCRCFAT columns were studied. A control specimen (C000) was cast with normal concrete without SF to be reference for comparison. Twelve columns were cast using RCA, six columns were cast using concrete incorporating 2% SF while the rest of columns were cast without SF. Failure mode, ductility, ultimate load capacity, axial deformation, ultimate strains, stress-strain response, and stiffness of the SCRCFAT columns were studied. The results showed that, the peak load of tested SCRCFAT columns incorporating 5-100 % RCA without SF reduced by 2.33-11.28 % compared to that of C000. Conversely, the peak load of tested SCRCFAT columns incorporating 5-100% RCA in addition to 2% SF increased by 21.1-40.25%, compared to C000. Consequently, the ultimate axial deformation (∆) of column C100 (RCA= 100% and SF 0%) increased by about 118.9 % compared to C000. The addition of 2% SF to the concrete mix decreased the axial deformation of SCRCFAT columns compared to those cast with 0% SF. Moreover, the stiffness of the columns cast without SF decreased as the RCA % increased. In contrast, the columns stiffness cast with 2% SF increased by 26.28-89.7 % over that of C000. Finally, a theoretical model was proposed to predict the ultimate loads tested SCRCFAT columns and the obtained theoretical results agreed well with the experimental results.

Key Words
axial deformation; concrete-filled aluminum tubular columns; failure modes; recycled concrete; selfcompacting; steel fiber; stiffness

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

Emrah Madenci:Necmettin Erbakan University, Faculty of Engineering, Department of Civil Engineering, Konya, Turkey

Walid Mansour:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh, Egypt

I.A. Sharaky:Department of Materials Engineering, Faculty of Engineering, Zagazig University, Zagazig, 44519, Egypt

Sabry Fayed:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh, Egypt

Abstract
This paper proposes an effective method for optimizing the structure of functionally graded isotropic and incompressible linear elastic materials. The main emphasis is on utilizing a specialized polytopal composite finite element (PCE) technique capable of handling a broad range of materials, addressing common volumetric locking issues found in nearly incompressible substances. Additionally, it employs a continuum model for bi-directional functionally graded (BFG) material properties, amalgamating these aspects into a unified property function. This study thus provides an innovative approach that tackles diverse material challenges, accommodating various elemental shapes like triangles, quadrilaterals, and polygons across compressible and nearly incompressible material properties. The paper thoroughly details the mathematical formulations for optimizing the topology of BFG structures with various materials. Finally, it showcases the effectiveness and efficiency of the proposed method through numerous numerical examples.

Key Words
functionally graded materials; incompressible materials; multi-material problems; polygonal discretization; topology optimization

Address
Thanh T. Banh:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea

Joowon Kang:Department of Architecture, Yeungnam University, Gyeongsan 38541, Korea

Soomi Shin:Research Institute of Industrial Technology, Pusan National University, Busan 46241, Korea

Dongkyu Lee:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea

Abstract
The primary objective of this study is to investigate the production and performance characteristics of structural concrete incorporating varying proportions (0%, 25%, and 50% by volume) of pumice stone, as well as aluminum lathe as an additive at 0%, 1%, 2%, and 3%, under fire conditions. The experiment will be conducted over a period of up to 1 hour, at temperatures ranging from 24°C, 200°C, 400°C and 600°C. For the purpose of this, a total of twelve test samples were manufactured, and then tests of compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS) were performed on these samples.Next, a comparison was made between the obtained values and the influence of temperature. To achieve this objective, the manufactured samples were placed at temperatures of 200°C, 400°C, and 600°C for a duration of 1 hour, and were subjected to the influence of temperature.These values at 24 °C were then contrasted with the CS results obtained from test samples that were subjected to the temperature effect for an hour at 200 °C, 400 °C, and 600 °C. A comprehensive analysis of the test outcomes reveals that the incorporation of aluminum lathe wastes into a mixture results in a significant reduction in the compressive strength of the concrete. As a result of this adjustment, the CS values dropped by 32.93%, 45.70%, and 52.07%, respectively. Furthermore, It was shown that testing the ratios of pumice stone alone resulted in a decrease in CS outcomes. Additionally, it was found that the presence of higher temperatures is clearly the primary factor contributing to the decrease in the strength of concrete. Due to elevated temperatures, the CS values decreased by 19.88%, 28.27%, and 38.61% respectively.After this investigation, an equation that explains the connection between CS and STS was provided through the utilization of the data of the experiments that were carried out.

Key Words
aluminum lathe; compressive strength; flexural strength; pumice; splitting tensile strength

Address
Mohammad Alharthai:Department of Civil Engineering, College of Engineering, Najran University, Najran 66462, Saudi Arabia

Yasin Onuralp OzkiliC:Necmettin Erbakan University, Faculty of Engineering, Department of Civil Engineering, Konya, Turkey

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

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

Mebi Ozdoner:Necmettin Erbakan University, Faculty of Engineering, Department of Civil Engineering, Konya, Turkey

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


Abstract
The seismic performance of traditional steel frame-shear wall structures was significantly improved by the application of self-centering steel-reinforced concrete (SRC) wall-panel structures in the steel frames. This novel resilience functionality can rapidly restore the structure after an earthquake. The presented steel frame with steel-reinforced concrete selfcentering wall-panel structures (SF-SCW) was validated, indicating its excellent seismic performance. The seismic design method based on bear capacity cannot correctly predict the elastic-plastic performance of the structure, especially certain weak floors that might be caused by a major fracture. A four-level seismic performance index, including intact function, continued utilization, life safety, and near-collapse, was established to achieve the ideal failure mode. The seismic design method, based on structural displacement, was proposed by considering performance objectives of the different seismic action levels. The pushover analysis of a six-floor SF-SCW structure was carried out under the proposed design method and the results showed that this six-floor structure could achieve the predicted failure mode.

Key Words
fracture mode; performance index; seismic design; self-centering wall panel; steel frame

Address
Sisi Chao, Hua Huang, Huiping Liu and Chenghua Li:School of Civil & Architecture Engineering, Xi'an Technological University, Xi'an 710021, China

Guanqi Lan:1)School of Civil Engineering, Xi'an Shiyou University, Xi'an 710065, China
2)Key Laboratory of Low-carbon Urban Construction of Xi'an, Chang' an University, Xi'an 710061, China

Abstract
Previous experimental studies have effectively demonstrated the remarkable efficiency of the stiffened channel link in connecting circular columns and I-shaped beams. This research aims to present design criteria and assess the seismic properties of this specific connection type through numerical modeling. Various parameters, including stiffener type and geometric properties of the stiffened channel element, were duly taken into account. The findings from over 136 nonlinear finite element analyses (FEAs) reveal that the recommended detailing scheme reliably satisfies all the regulations specified for rigid beam-to-column connections in special moment frames.

Key Words
cyclic loading; moment resisting frame; non-linear FEA; rigid connection; tubular column

Address
Shohreh Sohaei:Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Mehrzad TahamouliRoudsari:Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

Parham Memarzadeh:Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Abstract
Yielding dampers exhibit varying cyclic behavior based on their geometry. These dampers not only increase the energy dissipation of the structure but also increase the strength and stiffness of the structure. In this study, parametric investigations were carried out to explore the impact of angled U-shape damper (AUSD) dimensions on its cyclic behavior. Initially, the numerical model was calibrated using the experimental specimen. Subsequently, analytical equations were presented to calculate the yield strength and elastic stiffness, which agreed with the experimental results. The outcomes of the parametric studies encompassed ultimate strength, effective stiffness, energy dissipation, and equivalent viscous damper ratio (EVDR). These output parameters were compared with similar dampers. Also, the magnitude of the effect of damper dimensions on the results was investigated. The results of parametric studies showed that the yield strength is independent of the damper width. The length and thickness of the damper have the greatest effect on the elastic stiffness. Reducing length and width resulted in increased energy dissipation, effective stiffness, and ultimate strength. Damper width had a more significant effect on EVDR than its length. On average, every 5 mm increase in damper thickness resulted in a 3.6 times increase in energy dissipation, 3 times the effective stiffness, and 3 times the ultimate strength of the model. Every 15 mm reduction in damper width and length increased energy dissipation by 14% and 24%, respectively.

Key Words
angled U-shape damper; cyclic behavior; energy dissipation; numerical analysis; plastic analysis

Address
Kambiz Cheraghi:Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran

Mehrzad TahamouliRoudsari:Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

Abstract
The growing quantity of tires and building trash piling up in landfills poses a serious threat to the stability of the ecosystem. Researchers are exploring ways to reduce and use such byproducts of the construction industry in an effort to promote greener building practices. Thus, using recycled crumb rubber from scrap tires in concrete manufacturing is important for the industry's long-term viability. This study examines the proportion of waste rubber in fiber form, specifically at weight percentages of 5%, 10%, and 15%. Moreover, the study examines the shear behavior of reinforced concrete beams. A total of twelve RC beam specimens, each sized 100 mm by 150 mm by 1000 mm (w x d x L), were constructed and positioned to the test. Various mixtures were designed with different levels of scrap tire rubber content (0%, 5%, 10%, and 15%) and Stirrup Vol. Ratio (2.10, 2.80, and 3.53) in reinforced concrete beams. The findings indicate that the inclusion of scrap rubber in concrete leads to a decrease in both the mechanical characteristics and weight of the material. This is mostly attributed to the lower strength and stiffness of the rubberized concrete. Furthermore, estimations generated by a variety of design codes were examined alongside the obtained data. In order to make a comparison between the estimates provided by the different codes such as ACI 318-14, CEB-FIB and Iranian national building codes, a calculation was done to determine the ratio of the experimental shear strength to the anticipated shear strength for each code.

Key Words
concrete; beam; national building codes; scrap tires; shear; waste

Address
Ali Serdar Ecemis and Emrah Madenci:Department of Civil Engineering, Necmettin Erbakan University, Konya, Turkey

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

Sabry Fayed:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh, Egypt

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

Yasin Onuralp OzkillC:1)Department of Civil Engineering, Necmettin Erbakan University, Konya, Turkey2)Department of Civil Engineering, Lebanese American University, Byblos, Lebanon


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