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CONTENTS
Volume 41, Number 3, November10 2021
 

Abstract
This study compares between the mechanical properties of concrete either reinforced with recycled plastic (RP) or end-hooked steel (EHS) fibers with volume fractions of 1, 2 and 3%. Also, the effects of the fiber type and volume fraction on flexural responses were investigated using experimental program composed of seven reinforced concrete (RC) beams. Generally, results showed that the RP and EHS fibers remarkably enhanced both the mechanical characteristics of concrete and the flexural capacity of RC beams. Specifically, concrete matrix that reinforced with 2% volume fraction of RP or EHS fibers exhibited the highest capacities among all tested specimens. On the other hand, the compressive and the tensile strengths of the fibrous concrete which strengthened with 3% volume fraction (either RP or EHS fibers) were lower than their counterparts that reinforced with lower volume fraction (2%). As the fiber volume fraction increased up to 2%, the peak load of the RC beams increased followed by a reduction for higher fiber volumes. The peak load of the RC beam specimens reinforced with 2% of RP and EHS fibers were 57.1 kN and 60.7 kN, respectively compared to 39.6 kN for the control RC beam. Both RP and EHS fibers had a positive effect on the (effective/gross) flexural rigidity ratio, especially when used with volume fraction lower than 3%. RC beams reinforced with 1% of RP and EHS fibers yielded higher ductility in comparison with 2 and 3%. An analytical model constructed based on the distribution of stress-strains along the height of the RC beam was used to estimate the bending moments at different stages. Results well agreed with the experimental records.

Key Words
analytical model; ductility index; end-hooked steel fiber; flexural rigidity; recycled plastic fiber; stiffness

Address
Walid Mansour and Sabry Fayed: Civil Engineering Department, Faculty of Engineering, Kafrelsheikh University, Box 33511, Kafrelsheikh, Egypt

Abstract
The present research aims to analyze the response of viscoelastic laminated composite microplate under microparticle low-velocity impact. Hertz contact law is used to model the impact phenomenon between the microparticle and the microplate. According to Kelvin-Voigt theory, the realistic behavior of the structure is considered by considering the viscoelastic properties. The governing equations of the system are derived based on the first-order shear deformation plate theory (FSDT) and the nonlocal strain gradient theory (NSGT) by employing Hamilton's principle. Galerkin's method is employed to solve differential equations of microplate with different boundary conditions. Afterward, the system of time-dependent equations by applying the Newmark' s method is solved. The parametric study is presented to examine the effect of particle radius, particle initial velocity, nonlocal parameter, length scale parameter, viscoelastic modulus, fiber orientation, and different boundary conditions on the impact response of microplate.

Key Words
hertz contact law; laminated micro composite; low-velocity impact; nonlocal strain gradient theory; viscoelastic

Address
Peyman Rashidpour, Majid Ghadiri and Asghar Zajkani: Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

Abstract
Shape memory alloy (SMA) is a relatively new material used in structural engineering. In this paper, responses of braced frames with buckling restrained braces (BRBs) and short-segment SMA braces are investigated. Frame, a six-story structure, is designed according to valid prescriptive codes and then the appropriate nonlinear model is created. Three approaches are examined: The first one is using only BRB in all the stories (BRBF system). The second is using only short-segment SMA braces in all the stories (SMA system). The third approach is combining the BRB and short-segment SMA braces in all stories (COMBINED system). Nonlinear time history analysis (NLTHA) is performed subjected to near field (NF) and far field (FF) record sets at maximum considered earthquake (MCE) and design base earthquake (DBE) levels, and responses of the considered systems are investigated and compared. Results show that none of the three systems is recommended in NF site construction because they exceed the allowable limit state. While, subjected to FF records COMBINED system is a good idea as its responses like maximum inter-story drift ratio, residual drift and brace ductility demand are in an allowable range.

Key Words
buckling restrained brace; drift; earthquakes; frame; near field; shape memory alloy brace

Address
Hamid Beiraghi and Homa Freidoni: Department of Civil Engineering, Mahdishahr Branch, Islamic Azad University, Mahdishahr, Iran

Abstract
Light Steel Frame (LSF) systems are increasingly used as sustainable design solutions in modern construction. Using light weight concrete as infill material in LSF systems offers several advantages such as increased integrity, strength, ductility and fire resistance, while it also prevents premature local buckling failure modes. This research investigates the application of Styrene Concrete (SC) as light weight infill materials in LSF panels. Five full-scale LSF walls are examined to study the efficiency of using SC light weight infill material in improving the cyclic behavior of LSF panels. The specimens are designed to assess the effects of infill material as well as using strap bracing, hobnail and hole on the studs. The key seismic performance parameters including failure mode, load-bearing capacity, lateral stiffness, ductility, stiffness deterioration and energy dissipation capacity are obtained for each case. The experimental results demonstrate that the application of non-structural lightweight concrete as infill material in LSF shear walls has significant positive effects on their seismic performance by postponing the buckling of the steel frame members and changing the dominant brittle failure to a ductile failure mode. The interaction between LSF members and SC infill material could also considerably improve the lateral performance of the frame system. It is shown that adding the hobnails to the vertical studs increased the lateral stiffness and resistance of the frames by 45% and 28%, respectively. While the presence of a hole in the studs had little effect on the lateral resistance of the wall, it increased the energy dissipation capacity and ductility of the system by up to 18% and 6%, respectively.

Key Words
Cold Formed Steel Frame (CFS); cyclic behavior; lightweight concrete; seismic performance; shear wall styrene concrete

Address
Mohammad Rezaeian Pakizeh and Hossein Parastesh: Department of Civil Engineering, University of Science and Culture, Tehran, Iran
Farhang Farahbod: Building and Housing Research Center (BHRC), Tehran, Iran
Iman Hajirasouliha: Department of Civil and Structural Engineering, The University of Sheffield, Sheffield, UK

Abstract
This article aims to introduce a multigrid preconditioned conjugate gradient (MPCG)-oriented topology optimization (TO) methodology using multiple bi-directional functionally graded (BFG) models for the first time. For that purpose, the MPCG paradigm is integrated into the TO procedure to more effectively and quickly resolve linear algebraic systems arising from the differential equations' discretization. In addition, a refined BFG material interpolation in Solid Isotropic Material with Penalization (SIMP), which is based on an alternating active-phase algorithm, is produced. In which continuously altered macroscopic material properties are represented by an explicit exponential function. This paper describes the well-founded mathematical formulations for multi-material topology optimization of BFG structures in great detail. Finally, several numerical examples are tested to demonstrate the proposed approach's capability and efficiency.

Key Words
bi-directional functionally graded materials (BFGMs); multigrid preconditioned conjugate gradient (MPCG); multiple materials; topology optimization

Address
Thanh T. Banh, Nam G, Jaehong Lee and Dongkyu Lee: Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea
Qui X. Lieu: Faculty of Civil Engineering, Ho Chi Minh City University of Technology, (HCMUT) 268 Ly Thuong Kiet Street, District 10,
Ho Chi Minh City, Viet Nam;
Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Viet Nam
Joowon Kang: Department of Architecture, Yeungnam University, Gyeongsan 38541, Korea

Abstract
The eight-bolt stiffened extended end plate (8ES) connection is one of the connections prequalified for use in special and intermediate moment frames in ANSI/AISC 358. Simulated seismic testing of 8ES connections has generally shown sound performance with ductile failure modes. However, fast fracture of the beam flange at the stiffener toe has been observed in a recent study and was attributed to the high stress concentration in this region. To address this problem, an unstiffened eight-bolt extended end plate connection in which the stress concentration is eliminated by removing the stiffener, and the bolts are rearranged into an octagonal pattern to ensure uniform distribution of bolt forces, has been recently proposed. The study herein performed detailed finite element analyses with octagonal bolt arrangement to demonstrate that despite the improvements, high strain demands at the beam flange to end plate CJP welds may develop when the proposed unstiffened connection is used in conjunction with deep wide flange beam sections (e.g., W-sections of 900 mm nominal depth). Hence, an extended shear tab is used and analytically evaluated for unreinforced eight-bolt extended end plate connections. The extended heavy shear tab relocates the plastic hinge away from flange weld and slightly delays the onset of strength degradation. Systematic analysis results are developed and presented to demonstrate the enhanced seismic performance of the modified EEP connections and to plan future experimentations and design development.

Key Words
extended end plate connection; extended end plate stiffener; extended shear tab; octagonal bolt arrangement; seismic performance enhancement

Address
Shahriar Quayyumand Timothy R. Kohany: Department of Civil & Environmental Engineering, Manhattan College, Riverdale, NY 10471, USA

Abstract
In this paper, a composite beam element has been developed in this study, the composite steel-concrete beam strengthened with CFRP plate element can be used to model the nonlinear behavior of composite beams. The problem of slip and interfacial stresses in composite steel-concrete beam strengthened with CFRP plate is analyzed using linear elastic theory. The analysis is based on the deformation compatibility approach, where both the shear and normal stresses are assumed to be invariant across the adhesive layer thickness. The adopted model takes into account the adherend shear deformations by assuming a linear shear stress through the depth of the composite steel-concrete beam. This solution is intended for application to beams made of all kinds of materials bonded with a thin composite plate. For composite steel-concrete beam section, a geometrical coefficient is determined to show the effect of the adherend shear deformations. The theoretical predictions are compared with other existing solutions analytical and experimental which demonstrates the accuracy of the used element. Finally, numerical comparisons between the existing solutions and the present new solution enable a clear appreciation of the effects of various parameters. This research is helpful for the understanding on mechanical behaviour of the interface and design of such structures.

Key Words
adhesive bonding; CFRP plate; interfacial stresses; I-Steel-concrete composite beam; strengthening

Address
Bensatallah Tayeb, Tahar Hassaine Daouadji and Rabahi Abderezak: Laboratory of Geomatics and sustainable development, University of Tiaret, Algeria;
Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, Eastern Province, Saudi Arabia;
University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abstract
This study aimed to develop an elastoplastic homogenization model to accurately predict the elastoplastic static behavior of a corrugated-core sandwich structure. A panel composed of two planar layers and one corrugated layer is modeled by a homogeneous orthotropic single-layer plate. A plane stress elastoplastic model is adopted to describe the behavior of each layer. Homogenization is achieved by local integration across the thickness of each layer. The proposed homogenization model is implemented in the ABAQUS finite element software using UGENS user subroutine. The results obtained by our model are compared to those obtained by full 3D simulations under different loading conditions. The comparisons show the efficiency and the accuracy of the proposed elastoplastic homogenization model.

Key Words
composite structure; corrugated cardboard; elastoplastic behavior; FEM simulation; homogenization

Address
Viet D. Luong: MATIM, University of Reims Champagne-Ardenne, UFR SEN, Campus Moulin de la Housse, 51100 Reims, France;
Thai Nguyen University of Technology, Thai Nguyen, Vietnam
Fazilay Abbès and Boussad Abbès: MATIM, University of Reims Champagne-Ardenne, UFR SEN, Campus Moulin de la Housse, 51100 Reims, France
Minh P. Hoang and Pham T.M. Duong: Thai Nguyen University of Technology, Thai Nguyen, Vietnam

Abstract
Track defects can change the interaction between layers and affect the nonlinear contact between the beam and base slab, causing deformations in the rail. This study proposes a theoretical model to clarify the influence mechanism of track defects on the track irregularity of high-speed railway bridges under pier settlement. The investigated track defects include the void under slab, interlayer debonding, and fastener fracture. The elongation coefficient of track deformation is used to describe the mapping characteristics of the interlayer parameters to track geometric under the additional bridge deformation. The geometric characteristics and changing trend of the rail surface are quantified under the influence of the failure position and critical length. Finally, the fundamental mechanisms of track deformation are elucidated, which lays a theoretical basis for further study of the long-term evolution of infrastructure.

Key Words
interface damage; long-term evolution; mapping characteristics; track deformation; track irregula

Address
Hongye Gou: Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
Key Laboratory of High-Speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
Rui Xie and Chang Liu: Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Wei Guo: School of Civil Engineering, Central South University, Changsha 410075, P.R. China;
National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, P.R. China
Bing Han: Southern Sichuan Intercity Railway CO., LTD, Chengdu, Sichuan 610031, China
Yi Bao: Department of Civil, Environmental & Ocean Engineering, Stevens Institute of Technology,
1 Castle Point Terrace, Hoboken, NJ 07030, USA

Abstract
This paper focuses on the seismic performance of typical pre-engineered steel buildings (PSB) on the west coast of Canada. PSB are widely adopted for commercial and industrial long span low-rise constructions. Their structural system consists of a moment resisting frame made of built-up tapered I-beam elements, which often have slender and/or non-compact sections to minimize steel consumption. Typical seismic design of PSB consists of elastic analysis with force reduction factors (FRF) that assume some ductility. However, failure mechanisms in PSB are usually governed by flange local buckling and lateral torsional buckling, which might not provide the expected ductility. This paper presents an extensive series of numerical analyses to evaluate the seismic performance of four PSB prototypes designed for the city of Victoria on the west coast of Canada. Prototypes have similar general dimensions, while members

Key Words
buckling; built-up steel sections; dynamic analysis; seismic design; steel structure

Address
Fabrício Bagatini-Cachuco and T.Y. Yang: Department of Civil Engineering, The University of British Columbia, 6250 Applied Science Ln, Vancouver, Canada

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