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CONTENTS
Volume 47, Number 3, May10 2023
 

Abstract
The steel structure is an assembly of individual structural members joined together by connections. The connections are the focal point to transfer the forces which is susceptible to damage easily. It is challenging to replace the affected connection parts after an earthquake. Hence, steel plates are utilised as a structural fuse that absorbs connection forces and fails first. The objective of the present research is to develop a beam-column end plate connection with single and dual fuse and study the effect of single fuse, dual fuse and combined action of fuse and damper. In this research, seismic resilient beam-column end plate connection is developed in the form of structural fuse. The novel connection consists of one main fuse was placed horizontally and secondary fuse was placed vertically over main fuse. The specimens are fabricated with the variation in number of fuse (single and dual) and position of fuse (beam flange top and bottom). From the fabricated ten specimens five specimens were loaded monotonically and five cyclically. The experimental results are compared with Finite Element Analysis results of Arunkumar and Umamaheswari (2022). The results are critically assessed in the aspect of moment-rotation behaviour, strain in connection components, connection stiffness, energy dissipation characteristics and ductility. While comparing the performance of total five specimens, the connection with fuse exhibited superior performance than the conventional connection. An equation is proposed for the moment of resistance of end-plate connection without and with structural fuse.

Key Words
damper; dual fuse; end-plate connection; seismic resilient; single fuse; structural fuse

Address
Arunkumar Chandrasekaran and Umamaheswari Nambiappan:Department of Civil Engineering, SRM Institute of Science and Technology, Kattankulathur, Chennai- 603203, India

Abstract
The primary objective of the current study is to optimize and evaluate the seismic performance of steel momentresisting frame (MRF) structures considering soil-structure interaction (SSI) effects. The structural optimization is implemented in the context of performance-based design in accordance with FEMA-350 at different confidence levels from 50% to 90% by taking into account fixed- and flexible-base conditions using an efficient metaheuristic algorithm. Nonlinear response-history analysis (NRHA) is conducted to evaluate the seismic response of structures, and the beam-on-nonlinear Winkler foundation (BNWF) model is used to simulate the soil-foundation interaction under the MRFs. The seismic performance of optimally designed fixed- and flexible-base steel MRFs are compared in terms of overall damage index, seismic collapse safety, and interstory drift ratios at different performance levels. Two illustrative examples of 6- and 12-story steel MRFs are presented. The results show that the consideration of SSI in the optimization process of 6- and 12-story steel MRFs results in an increase of 1.0 to 9.0 % and 0.5 to 5.0 % in structural weight and a slight decrease in structural seismic safety at different confidence levels.

Key Words
confidence level; performance-based design; soil-structure interaction; steel special moment frame; structural optimization

Address
Saeed Gholizadeh and Arman Milany:Department of Civil Engineering, Urmia University, Urmia, Iran

Oguzhan Hasançebi:Department of Civil Engineering, Middle East Technical University, Ankara, Turkey

Abstract
The main purpose of this study is to characterize the size-dependent strain rate sensitivity in structural steel using the continue stiffness measurement (CSM) indentation. A series of experiments, such as CSM indentation and optical microscope examination, has been performed at the room temperature at different rate conditions. The results indicated that indentation hardness, strain rate, and flow stress showed size-dependent behavior. The dependency of indentation hardness, strain rate, and flow stress on the indentation size was attributed to the transition of the dislocation nucleation rate and the dislocation behaviors during the indentation process. Since both hardness and strain rate showed the size-dependent behavior, SRS tended to depend on the indentation depth. The results indicated that the SRS was quite high over 2.0 at the indentation depth of 240 nm and quickly dropping to 0.08, finally around 0.046 at large indents. The SRS values at large indentations strongly agree with the general range reported for several types of low-carbon steel in the literature (Chatfield and Rote 1974, Nguyen et al. 2018b, Luecke et al. 2005). The results from the present study can be used in both static and dynamic analyses of structures as well as to assess and understand the deformation mechanism and the stress-state of material underneath the indenter tip during the process of the indentation testing.

Key Words
dislocation; microstructure; nanoindentation; size effect; strain rate sensitivity

Address
Ngoc-Vinh Nguyen:1)Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea
2)Department. of Civil Engineering, VNU Vietnam Japan University, My Dinh 129140, Tu Liem, Hanoi, Vietnam

Chao Chang:Department of Mechanics, School of Applied Science, Taiyuan University of Science and Technology, Taiyuan 030024, China

Seung-Eock Kim:Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea

Abstract
This paper presents a new scheme for constructing locking-free finite elements in thick and thin plates, called Discrete Shear Gap element (DSG), using multiphase material topology optimization for triangular elements of ReissnerMindlin plates. Besides, common methods are also presented in this article, such as quadrilateral element (Q4) and reduced integration method. Moreover, when the plate gets too thin, the transverse shear-locking problem arises. To avoid that phenomenon, the stabilized discrete shear gap technique is utilized in the DSG3 system stiffness matrix formulation. The accuracy and efficiency of DSG are demonstrated by the numerical examples, and many superior properties are presented, such as being a strong competitor to the common kind of Q4 elements in the static topology optimization and its computed results are confirmed against those derived from the three-node triangular element, and other existing solutions.

Key Words
discrete shear gap method; multi-material; reduced integration method; Reissner-Mindlin plate; shear locking; topology optimization

Address
Minh-Ngoc Nguyen and Wonsik Jung:Department of Architectural Engineering, Sejong University, Seoul, 05006, Republic of Korea

Soomi Shin and Dongkyu Lee:Research Institute of Industrial Technology, Pusan National University, Busan, 46241, Republic of Korea

Joowon Kang:School of Architecture, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Republicof Korea

Abstract
The H-shaped steel beam is popular due to its ease of manufacturing and connection to the column. This profile, which is used as a shallow beam, needs the high weak-axis bending stiffness and torsional stiffness to meet the overall stability. Achieving the local beam flange stability, bearing capacity, bending stiffness, and torsional requirements need a great thickness and width of the beam flange, which causes, which will cause more uneconomical structural design. So, the box-section beam is the ideal alternative. However, the current design specifications do not have design rules for the bolt-and-welded connection of the box-section beam and box-section column. The paper proposes a novel bolt-and-welded connection of the box-section beams and box-section columns based on a high-rise structural design scheme. Three connection models, BASE, WBF, and RBS, are analyzed under cyclic loading in ABAQUS software. The failure modes, hysteresis response, bearing capacity, ductility, plastic rotation angle, energy dissipation, and stiffness degradation of all models are determined and compared. Compared with the other two models, the model WBF exhibited excellent seismic performance, ductility, and plastic rotation ability. Finally, model WBF was chosen as the connection scheme used in the project design.

Key Words
box-section beam; box-section column; connection; H-shaped beam; panel zone

Address
Linfeng Lu, Songlin Ding, Yuzhou Liu and Zhaojia Chen:School of civil engineering, Chang'an University, 75 Chang'an Middle Rd, Xi'an, PR China

Zhongpeng Li:China Construction Third Bureau Group Co., Ltd., Mai Hua Rd, Nan Jing, PR China

Abstract
Conventional reinforced concrete design codes assume ideal strain evolution in semi-deep beams with externally bonded fiber-reinforced polymer (EB-FRP) web strips. However, there is a strain interaction between internal stirrups and web strips, leading to a notable difference between code-based and experimental shear strengths. Current study provides an experiment-verified detailed numerical framework to assess the potential strain interaction under quasi-static monotonic load. Based on the observations, steel stirrups are effective only for low EB-FRP amounts and the over-strengthening of semi-deep beams prevents the stirrups from yielding, reducing its shear strength contribution. A notable difference is detected between the code-based and the study-based EB-FRP strain values, which is a function of the normalized FRP stress parameter. Semianalytical relations are proposed to estimate the effective strain and stress of the components considering the potential strain interaction. For the sake of simplification, a linearized correction factor is proposed for the EB-FRP web strip strain, assuming its restraining effect as constant for all steel stirrup amounts.

Key Words
xternally bonded fiber reinforced polymer; reinforced concrete; semi-deep beam; strain interaction; shear strength

Address
Javad Mokari Rahmdel and Erfan Shafei:Faculty of Civil Engineering, Urmia University of Technology, Urmia, Iran

Abstract
The main objective of this article is to investigate the response of different fiber metal laminates subjected to low velocity impact experimentally and numerically via finite element method (FEM). Hence, two different fiber metal laminate (FML) samples (GLARE/CARALL) are made of 7075-T6 aluminum sheets and polymeric composites reinforced by Eglass/carbon fibers. In order to study the responses to the low velocity impacts, samples are tested by drop weight machine. The projectiles are released from 1- and 1.5-meters height were the speed reaches to 4.42 and5.42 meter per second and the impact energies are measured as 6.7 and 10 Joules. In addition to experimental study, finite element simulation is done and results are compared. Finally, a detailed study on the maximum deflection, delamination and damages in laminates and geometry's effect of projectiles on the laminate response is done. Results show that maximum deflection caused by spherical projectile for GLARE samples is more apparent in comparison with the CARALL samples. Moreover, the maximum deflection of GLARE samples subjected to spherical projectile with 6.7 Joules impact energy, 127% increases in comparison with the CARALL samples in spite of different total thickness.

Key Words
CARALL; drop weight test; fiber metal laminates; GLARE; low velocity impact

Address
Meisam Mohammadi:Department of Mechanical Engineering, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran

Mohammad Javad Ramezani:Department of Mechanical Engineering, Zanjan University, Zanjan, Iran

Abstract
An experimental study on six axially-loaded composite short columns with different thicknesses of steel tube and that of the concrete plate was carried out. Compared to the mechanical behavior of component specimens under axially compressed, the failure modes, compression deformation, and strain process were obtained. The two main parameters that have a significant enhancement to cross-sectional strength were also analyzed. The failure of an axially loaded UHPC-CFST short column is due to the crushing of the UHPC plate, while the CFST member does reach its maximum resistance. A reduction coefficient K'c, related to the confinement coefficient, is introduced to account for the contribution of CFST members to the ultimate load-carrying capacity of the UHPC-CFST composite short columns. Based on the regression analysis of the relationship between the confinement index ξ and the value of fcc/fc, a unified formula for estimating the axial compressive strength of CFST short columns was proposed, combined with the experimental results in this research, and an equation for reliably predicting the strength of UHPC-CFST composite short columns under axial compression were also proposed.

Key Words
axial compression; bearing capacity; composite column; Concrete-Filled Steel Tube (CFST); Ultra High Performance Concrete (UHPC)

Address
Jiangang Wei and Baochun Chen:1)College of Civil Engineering, Fuzhou Univ., Fuzhou, Fujian 350116, China
2)College of Civil Engineering, Fujian Univ. of Technology, Fuzhou, Fujian 350118, China

Zhitao Xie:College of Civil Engineering, Fuzhou Univ., Fuzhou, Fujian 350116, China

Wei Zhang:1)College of Civil Engineering, Fujian Univ. of Technology, Fuzhou, Fujian 350118, China
2)Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Prague 190 00, Czech Republic

Yan Yang:College of Civil Engineering, Fuzhou Univ., Fuzhou, Fujian 350116, China

Xia Luo:College of Civil Engineering, Fujian Univ. of Technology, Fuzhou, Fujian 350118, China

Abstract
In this research, we tested 10 simply supported concrete-encased composite columns under monotonic eccentric loads and investigated their shear behaviour. The specimens tested were two reinforced concrete specimens, three steelreinforced concrete (SRC) specimens with an H-shaped steel section (also called a beam section), and five SRC specimens with a cruciform-shaped steel section (also called a column section). The experimental variables included the transverse steel shape's depth and the longitudinal steel flange's width. Experimental observations indicated the following. (1) The ultimate loadcarrying capacity was controlled by web compression failure, defined as a situation where the concrete within the diagonal strut's upper end was crushed. (2) The composite effect was strong before the crushing of the concrete outside the steel shape. (3) We adjusted the softened strut-and-tie SRC (SST-SRC) model to yield more accurate strength predictions than those obtained using the strength superposition method. (4) The MSST-SRC model can more reasonably predict shear strength at an initial concrete softening load point. The rationality of the MSST-SRC model was inferred by experimentally observing shear behaviour, including concrete crushing and the point of sharp variation in the shear strain.

Key Words
composite column; concrete-encased; shear strength; steel-reinforced concrete

Address
Keng-Ta Lin:Department of Civil and Environmental Engineering, National University of Kaohsiung,
No.700, Kaohsiung University Rd., 811, Kaohsiung, Taiwan, R.O.C.

Cheng-Cheng Chen:Department of Construction Engineering, National Taiwan University of Science and Technology,
No. 43, Sec. 4, Keelung Rd, 106, Taipei, Taiwan, R.O.C.

Abstract
A half open cross section built-up column, namely cold-formed thin-walled steel built-up column with 12-limbsection (CTSBC-12) is put forward. To deeply reveal the mechanical behaviors of CTSBC-12 under axial compression and put forward its calculation formula of axial bearing capacity, based on the previous axial compression experimental research, the finite element analysis (FEA) is conducted on 9 CTSBC-12 specimens, and then the variable parameter analysis is carried out. The results show the FEA is in good agreement with the experimental research, the ultimate bearing capacity error is within 10%. When the slenderness ratio is more than 96.54, the ultimate bearing capacity of CTSBC-12 decreases rapidly, and the failure mode changes from local buckling to global buckling. With the local buckling failure mode unchanged, the ultimate bearing capacity decreases gradually as the ratio of web height to thickness increases. Three methods are used for calculating the ultimate bearing capacity, the direct strength method of AISI S100-2007 gives result of ultimate axial load which is closest to the test and FEA results. But for simplicity and practicality, a simplified axial bearing capacity formula is proposed, which has better calculation accuracy with the slenderness ratio changing from 30 to 100.

Key Words
axial bearing capacity; built-up column; calculation formula; cold-formed thin-walled steel; slenderness ratio

Address
Wentao Qiao:1)School of Civil Engineering, ShiJiazhuang Tiedao University, Shi Jiazhuang, China
2)Key Laboratory of Roads and Railway Engineering Safety Control (Shijiazhuang Tiedao University),
Ministry of Education, Shijiazhuang, Hebei Province, 050043, China

Yuhuan Wang:China Design Group Co. Ltd., NO.9, Ziyun Road, Nanjing 210001, China

Ruifeng Li:School of Civil Engineering, ShiJiazhuang Tiedao University, Shi Jiazhuang, China

Dong Wang:TRC Companies, Baton Rouge, United States of America

Haiying Zhang:School of Civil Engineering, Southeast University, Nanjing, China

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