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CONTENTS
Volume 50, Number 1, January 10 2024
 

Abstract
The objective of this research is to study experimentally and numerically the behavior of steel beam columns with openings. Although the presence of openings in the beam columns is inevitable, finding ways to maintain strength is crucial. The studied parameters are opening shape, the ratio between opening height to specimen height, the percentage of opening location from support to beam column length, and web slenderness. Experimental tests are conducted including twelve specimens to study the effect of these parameters and record failure load, load deflection curve, and stress strain curve. Two failure modes are observed: local and flexural buckling. Interaction curves plotted from finite element model analysis are also used to expand the parametric study. Changing the location of the opening can decrease failure load by up to 7% and 60% in both normal and moment ratios respectively. Increasing the opening dimension can lead to a drop in the axial ratio by up to 29% and in the moment ratio by up to 74%. The weakest beam column behavior is noticed in specimens with rectangular openings which results from uneven and concentrated stresses around the opening. The main results of this research illustrate that the best location for opening is at 40% - 50% from beam column support. Also, it is advisable to use circular openings instead of rectangular openings in specimens having slender webs because moment ratios are raised by 85% accompanied by a rise in normal ratios by 9%.

Key Words
beam columns; experimental study; local buckling; web opening

Address
Mona M. Fawzy:Civil Engineering Program, The Higher Institute of Engineering, El-Shorouk Academy, Nakheel district 11837, Cairo, Egypt

Fattouh M. F. Shaker, Alia M. Ayyash and Mohamed M. Salem:Department of Structural Engineering, Faculty of Engineering, Helwan University Ain Helwan 11795, Cairo, Egypt

Abstract
This research presents dynamical reaction investigation of pore-dependent and nano-thickness beams having functional gradation (FG) constituents exposed to a movable particle. The nano-thickness beam formulation has been appointed with the benefits of refined high orders beam paradigm and nonlocal strain gradient theory (NSGT) comprising two scale moduli entitled nonlocality and strains gradient modulus. The graded pore-dependent constituents have been designed through pore factor based power-law relations comprising pore volumes pursuant to even or uneven pore scattering. Therewith, variable scale modulus has been thought-out until process a more accurate designing of scale effects on graded nano-thickness beams. The motion equations have been appointed to be solved via Ritz method with the benefits of Chebyshev polynomials in cosine form. Also, Laplace transform techniques help Ritz-Chebyshev method to obtain the dynamical response in time domain. All factors such as particle speed, pores and variable scale modulus affect the dynamical response.

Key Words
design; dynamic response; moving load; nonlocal strain gradient theory; pores

Address
Abdulaziz Saud Khider, Ali Aalsaud, Nadhim M. Faleh,Mamoon A.A. Al-Jaafari and Raad M. Fenjan:Mustansiriyah University, Collage of Engineering, Mechanical Engineering Department, Baghdad, Iraq

Abeer K. Abd:Ministry of Transportation, Iraq

Abstract
In this article, a mathematical model is developed to predict the dynamic behavior of bio-inspired composite beam with helicoidal orientation scheme under variable axial load using a unified higher order shear deformation beam theory. The geometrical kinematic relations of displacements are portrayed with higher parabolic shear deformation beam theory. Constitutive equation of composite beam is proposed based on plane stress problem. The variable axial load is distributed through the axial direction by constant, linear, and parabolic functions. The equations of motion and associated boundary conditions are derived in detail by Hamilton's principle. Using the differential quadrature method (DQM), the governing equations, which are integro-differential equations are discretized in spatial direction, then they are transformed into linear eigenvalue problems. The proposed model is verified with previous works available in literatures. Parametric analyses are developed to present the influence of axial load type, orthotropic ratio, slenderness ratio, lamination scheme, and boundary conditions on the natural frequencies of composite beam structures. The present enhanced model can be used especially in designing spacecrafts, naval, automotive, helicopter, the wind turbine, musical instruments, and civil structures subjected to the variable axial loads.

Key Words
bio-inspired composite beams; Differential Quadrature Method (DQM); helicoidal orientation; parabolic shear beam theory; variable axial in-plane load; Vibration Analysis

Address
Tharwat Osman, Salwa A. Mohamed and Nazira Mohamed:Department of Engineering Mathematics, Faculty of Engineering, P.O. Box 44519, Zagazig, Egypt

Mohamed A. Eltaher:1)Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia
2)Mechanical Design & Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Mashhour A. Alazwari:Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia

Abstract
This research explores the domain of organic solar cells, a photovoltaic technology employing organic electronics, which encompasses small organic molecules and conductive polymers for efficient light absorption and charge transport, leading to electricity generation from sunlight. A computer simulation is employed to scrutinize resonance and dynamic stability in OSCs, with a focus on size effects introduced by nonlocal strain gradient theory, incorporating additional terms in the governing equations related to displacement and time. Initially, the Navier method serves as an analytical solver to delve into the dynamics of design points. The accuracy of this initial step is verified through a meticulous comparison with high-quality literature. The findings underscore the substantial impact of viscoelastic foundations, size-dependent parameters, and geometric factors on the stability and dynamic deflection of OSCs, with a noteworthy emphasis on the amplified influence of size-dependent parameters in higher values of the different layers' thicknesses.

Key Words
Hamilton's principle; Naiver type method; OSC; stability; Vibrational analysis

Address
Jing Pan and Yi Hu:Department of Materials and Chemical Engineering, Taiyuan University, Taiyuan 030000, Shanxi, China

Guanghua Zhang:Department of Intelligence and Automation, Taiyuan University, Taiyuan 030000, Shanxi, China

Abstract
In this paper, the modified couple stress theory (MCST) and first order shear deformation theory (FSDT) are employed to investigate the free vibration and bending analyses of a three-layered micro-shell sandwiched by piezoelectric layers subjected to an applied voltage and reinforced graphene nanoplatelets (GPLs) under external and internal pressure. The micro-shell is resting on an elastic foundation modeled as Pasternak model. The mixture's rule and Halpin-Tsai model are utilized to compute the effective mechanical properties. By applying Hamilton's principle, the motion equations and associated boundary conditions are derived. Static/ dynamic results are obtained using Navier's method. The results are validated with the previously published works. The numerical results are presented to study and discuss the influences of various parameters on the natural frequencies and deflection of the micro-shell, such as applied voltage, thickness of the piezoelectric layer to radius, length to radius ratio, volume fraction and various distribution pattern of the GPLs, thickness-to-length scale parameter, and foundation coefficients for the both external and internal pressure. The main novelty of this work is simultaneous effect of graphene nanoplatelets as reinforcement and piezoelectric layers on the bending and vibration characteristics of the sandwich micro shell.

Key Words
applied voltage; FSDT; graphene nanoplatelet; MCST; micro-shell; Piezoelectric

Address
Khashayar Arshadi and Mohammad Arefi:Faculty of Mechanical Engineering, Department of Solid Mechanics, University of Kashan, Kashan 87317-51167, Iran

Abstract
In this study, the two-dimensional crack problem was investigated by using the finite element method (FEM)- based ANSYS package program and the artificial neural network (ANN)-based multilayer perceptron (MLP) method. For this purpose, a half-infinite functionally graded (FG) layer with a crack pressed through two rigid blocks was analyzed using FEM and ANN. Mass forces and friction were neglected in the solution. To control the validity of the crack problem model exercised, the acquired results were compared with a study in the literature. In addition, FEM and ANN results were checked using Root Mean Square Error (RMSE) and coefficient of determination (R2 ), and a well agreement was found. Numerical solutions were made considering different geometric parameters and material properties. The stress intensity factor (SIF) was examined for these values, and the results were presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the SIF. Also FEM and ANN can be logical alternative methods to time-consuming analytical solutions if used correctly.

Key Words
artificial neural network; finite element method; fracture mechanics; functionally graded layer; stress intensity factor

Address
Murat Yaylacl and Şevval Ozturk:Department of Civil Engineering, Recep Tayyip Erdogan University, 53100, Rize, Turkey

Ecren Uzun Yaylacl:Faculty of Engineering and Architecture, Recep Tayyip Erdogan University, 53100, Rize, Turkey

Muhittin Turan:Department of Civil Engineering, Bayburt University, 69010, Bayburt, Turkey

Mehmet Emin Ozdemir:Department of Civil Engineering, Cankiri Karatekin University, 18100, Çanklrl, Turkey

Sevil Ay:Department of Civil Engineering, Artvin Coruh University, 08100, Artvin, Turkey

Abstract
Multichannel analysis of surface waves (MASW) method has exhibited broad application prospects in the nondestructive detection of interfacial debonding in steel-concrete composite structures (SCCS). However, due to the structural diversity of SCCS and the high stealthiness of interfacial debonding defects, the feasibility of MASW method needs to be investigated in depth. In this study, synthetic parametric study on MASW nondestructive debonding detection for SCCSs is performed. The aim is to quantitatively analyze influential factors with respect to structural composition of SCCS and MASW measurement mode. First, stress wave composition and propagation process in SCCS are studied utilizing 2D numerical simulation. For structural composition in SCCS, the thickness variation of steel plate, concrete core, and debonding defects are discussed. To determine the most appropriate sensor arrangement for MASW measurement, the effects of spacing and number of observation points, along with distances between excitation points, nearest boundary, as well as the first observation point, are analyzed individually. The influence of signal type and frequency of transient excitation on dispersion figures from forwarding analysis is studied to determine the most suitable excitation signal. The findings from this study can provide important theoretical guidance for MASW-based interfacial debonding detection for SCCS. Furthermore, they can be instrumental in optimizing both the sensor layout design and signal choice for experimental validation.

Key Words
steel-concrete composite structures (SCCS); interface debonding detection; multichannel analysis of surface waves (MASW); parametric study; numerical simulation

Address
Hongbing Chen and Jiajin Zeng:School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing, China

Shiyu Gan and Xin Nie:Department of Civil Engineering, Tsinghua University, Beijing, China

Yuanyuan Li:Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian, China

Abstract
Following an internal column failure, adjacent double-span beams above the failed column will play a critical role in the load transfer and internal force redistribution within the remaining structure, and the span-to-depth ratios of double-span beams significantly influence the structural resistance capacity against progressive collapse. Most existing studies have focused on the collapse-resistant performances of single-story symmetric structures, whereas limited published works are available on the collapse resistances of multi-story steel frames with unequal spans. To this end, in this study, numerical models based on shell elements were employed to investigate the structural behavior of multi-story steel frames with unequal spans. The simulation models were validated using the previous experimental results obtained for single- and two-story steel frames, and the load–displacement responses and internal force development of unequal-span three-story steel frames under three cases were comprehensively analyzed. In addition, the specific contributions of the different mechanism resistances of unequal-span, double-span beams of each story were separated quantitatively using the energy equilibrium theory, with an aim to gain a deeper level of understanding of the load-resistance mechanisms in the unequal-span steel frames. The results showed that the axial and flexural mechanism resistances were determined by the span ratio and linear stiffness ratio of double-span beams, respectively.

Key Words
cooperative working; multi-story steel frame; progressive collapse; resistance contribution; unequal spa

Address
Zheng Tan, Li-min Tian, Yao Gao, Yu-hui Zheng:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Wei-hui Zhong:1)School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
2)Key Laboratory of Structural Engineering and Earthquake Resistance, Ministry of Education,
Xi'an University of Architecture and Technology, Xi'an 710055, China

Bao Meng:1)School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
2)Key Laboratory of Structural Engineering and Earthquake Resistance, Ministry of Education,
Xi'an University of Architecture and Technology, Xi'an 710055, China
3)Department of Civil and Environmental Engineering, National University of Singapore, 119077, Singapore

Hong-Chen Wang:China Northwest Architecture Design and Research Institute Co., Ltd, Xi'an 710018, China

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