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CONTENTS
Volume 50, Number 3, February 10 2024
 

Abstract
This article presents a comparative analysis of seismic behavior in steel-beam reinforced concrete column (RCS) frames versus steel and reinforced concrete frames. The study evaluates the seismic response and collapse behavior of RCS frames of varying heights through nonlinear modeling. RCS, steel, and reinforced concrete special moment frames are considered in three height categories: 5, 10, and 20 stories. Two-dimensional frames are extracted from the three-dimensional structures, and nonlinear static analyses are conducted in the OpenSEES software to evaluate seismic response in post-yield regions. Incremental dynamic analysis is then performed on models, and collapse conditions are compared using fragility curves. Research findings indicate that the seismic intensity index in steel frames is 1.35 times greater than in RCS frames and 1.14 times greater than in reinforced concrete frames. As the number of stories increases, RCS frames exhibit more favorable collapse behavior compared to reinforced concrete frames. RCS frames demonstrate stable behavior and maintain capacity at high displacement levels, with uniform drift curves and lower damage levels compared to steel and reinforced concrete frames. Steel frames show superior strength and ductility, particularly in taller structures. RCS frames outperform reinforced concrete frames, displaying improved collapse behavior and higher capacity. Incremental Dynamic Analysis results confirm satisfactory collapse capacity for RCS frames. Steel frames collapse at higher intensity levels but perform better overall. RCS frames have a higher collapse capacity than reinforced concrete frames. Fragility curves show a lower likelihood of collapse for steel structures, while RCS frames perform better with an increase in the number of stories.

Key Words
fragility curves; incremental dynamic analysis; probability of collapse; Reinforced Concrete-Steel (RCS) frame; seismic intensity index

Address
Jalal Ghezeljeh, Seyed Rasoul Mirghaderi:Department of Civil Engineering, Tehran University, Tehran, Iran

Sina Kavei:Department of Civil Engineering, Sharif University of Technology, Tehran, Iran


Abstract
The collapse behavior observed in single-story beam-column assembly (SSBCA) do not accurately represent the actual overall stress characteristic of multi-story frame structure (MSFS) under column loss scenario owing to ignoring the interaction action among different stories, leading to a disconnection between the anti-collapse behaviors of "components" and "overall structures", that is, the anti-collapse performance of frame structures with two different structural scales has not yet formed a combined force. This paper conducts a numerical and theoretical study to explore the difference of the collapse behaviors of the SSBCA and MSFS, and further to reveal the internal force relationships and boundary constraints at beam ends of models SSBCA and MSFS. Based on the previous experimental tests, the corresponding refined numerical simulation models were established and verified, and comparative analysis on the resistant-collapse performance was carried out, based on the validated modeling methods with considering the actual boundary constraints, and the results illustrates that the collapse behaviors of the SSBCA and MSFS is not a simple multiple relationship. Through numerical simulation and theoretical analysis, the development laws of internal force in each story beam under different boundary constraints was clarified, and the coupling relationship between the bending moment at the most unfavorable section and axial force in the composite beam of different stories of multi story frames with weld cover-plated flange connections was obtained. In addition, considering the effect of the yield performance of adjacent columns on the anti-collapse bearing capacities of the SSBCA and MSFS during the large deformation stages, the calculation formula for the equivalent axial stiffness at the beam ends of each story were provided.

Key Words
collapse performance; difference analysis; equivalent axial stiffness; internal force relationship

Address
Zheng Tan:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Wei-Hui Zhong: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)Department of Civil and Environmental Engineering, National University of Singapore, 119077, Singapore

Xing-You Yao:Jiangxi Province Key Laboratory of Hydraulic and Civil Engineering Infrastructure Security,
Nanchang Institute of Technology, Nanchang, 330000, China

Yu-Hui Zheng:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Yao Gao:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Shi-Chao Duan:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Abstract
Stainless steel bolts (SSB) are increasingly utilized in bolted steel connections due to their good mechanical performance and excellent corrosion resistance. Fire accidents, which commonly occur in engineering scenarios, pose a significant threat to the safety of steel frames. The post-fire behavior of SSB has a significant influence on the structural integrity of steel frames, and neglecting the effect of temperature can lead to serious accidents in engineering. Therefore, it is important to evaluate the performance of SSB at elevated temperatures and their residual strength after a fire incident. To investigate the mechanical behavior of SSB after fire, 114 bolts with grades A4-70 and A4-80, manufactured from 316L austenitic stainless steel, were subjected to elevated temperatures ranging from 20°C to 1200°C. Two different cooling methods commonly employed in engineering, namely cooling at ambient temperatures (air cooling) and cooling in water (water cooling), were used to cool the bolts. Tensile tests were performed to examine the influence of elevated temperatures and cooling methods on the mechanical behavior of SSB. The results indicate that the temperature does not significantly affect the Young's modulus and the ultimate strength of SSB. Up to 500°C, the yield strength increases with temperature, but this trend reverses when the temperature exceeds 500°C. In contrast, the ultimate strain shows the opposite trend. The strain hardening exponent is not significantly influenced by the temperature until it reaches 500°C. The cooling methods employed have an insignificant impact on the performance of SSB. When compared to high-strength bolts, 316L austenitic SSB demonstrate superior fire resistance. Design models for the post-fire mechanical behavior of 316L austenitic SSB, encompassing parameters such as the elasticity modulus, yield strength, ultimate strength, ultimate strain, and strain hardening exponent, are proposed, and a more precise stress-strain model is recommended to predict the mechanical behavior of 316L austenitic SSB after a fire incident.

Key Words
degradation model; elevated temperature; post-fire behavior; stainless steel bolts; stress-strain curve

Address
Zhengyi Kong:Department of Civil Engineering, Anhui University of Technology, China; Institute for Sustainable Built Environment, Heriot-Watt University, United Kingdom

Bo Yang:Department of Civil Engineering, Anhui University of Technology, China

Cuiqiang Shi:Department of Civil Engineering, Anhui University of Technology, China

Xinjie Huang:Department of Civil Engineering, Anhui University of Technology, China

George Vasdravellis:Institute for Sustainable Built Environment, Heriot-Watt University, United Kingdom

Quang-Viet Vu:Laboratory for Computational Civil Engineering, Institute for Computational Science and Artificial Intelligence, Van Lang University,
Ho Chi Minh City, Vietnam; Faculty of Civil Engineering, School of Technology, Van Lang University, Ho Chi Minh City, Vietnam

Seung-Eock Kim:Department of Civil and Environmental Engineering, Sejong University, South Korea

Abstract
The main objective of this paper is to compute the far-field acoustic radiation (sound radiation) of functionally graded plates (FGM) loaded by sinusoidally varying point load subjected to the arbitrary boundary condition is carried out. The governing differential equations for thin functionally graded plates (FGM) are derived using classical plate theory (CPT) and Rayleigh integral using the elemental radiator approach. Four cases, segregated on power-law index k=0,1,5,10, are studied. A novel approach is illustrated to compute sound fields of vibrating FGM plates using the physical neutral surface with an elemental radiator approach. The material properties of the FGM plate for all cases are calculated considering the power law indexes. An in-house MATLAB code is written to compute the natural frequencies, normal surface velocities, and sound radiation fields are analytically calculated using semi-analytical formulation. Ansys is used to validate the computed sound power level. The parametric effects of the power law index, modulus ratios, different constituent of FGM plates, boundary conditions, damping loss factor on the sound power level, and radiation efficiency is illustrated. This work is the benchmark approach that clearly explains how to calculate acoustic fields using a solid layered FGM model in ANSYS ACT. It shows that it is possible to asymptotically stabilize the structure by controlling the intermittent layers' stiffness. It is found that sound fields radiated by the elemental radiators approach in MATLAB, ANSYS and literatures are in good agreement. The main novelty of this research is that the FGM plate is analyzed in the low-frequency range, where the stiffness-controlled region governs the whole analysis. It is concluded that a clamped mono-ceramic FGM plate radiates a lesser sound power level and higher radiation efficiency than a mono-metallic or metal-rich FGM plate due to higher stiffness. It is found that change in damping loss factor does not affect the same constituents of FGM plates but has significant effects on the different constituents of FGM plates.

Key Words
elemental radiators; functionally graded plates; physical neutral surface; power law index; Rayleigh integral; sound radiation

Address
Baij Nath Singh:1)Department of Mechanical Engineering, Indian Institute of Technology, Dhanbad-826004, India
2)Department of Mechanical Engineering, Bennett University, Greater Noida-201310, India

Vinayak Ranjan:2)Department of Mechanical Engineering, Bennett University, Greater Noida-201310, India
3)Department of Mechanical Engineering, Rowan University, New Jersey, U.S.A.

R.N. Hota:Department of Mechanical Engineering, Indian Institute of Technology, Dhanbad-826004, India

Abstract
Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel–concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel–UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load–slip relationship of SENBs in PSUCBs.

Key Words
bolted shear connector; push-out test; shear performance; steel–UHPC composite beam; Ultra-HighPerformance Concrete (UHPC)

Address
Zhuangcheng Fang:1)Earthquake Engineering Research & Test Center, Guangzhou University, Guangzhou, 510006, China
2)Guangdong Key Laboratory of Earthquake Engineering & Applied Technique, Guangzhou 510006, China
3)School of Civil and Transportation Engineering, Guangdong Univ. of Technology, Guangzhou, 510006, China

Jinpeng Wu:School of Civil and Transportation Engineering, Guangdong Univ. of Technology, Guangzhou, 510006, China

Bingxiong Xian:School of Civil and Transportation Engineering, Guangdong Univ. of Technology, Guangzhou, 510006, China

Guifeng Zhao:School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China

Shu Fang:Guangdong Key Laboratory of Earthquake Engineering & Applied Technique, Guangzhou 510006, China

Yuhong Ma:1)Earthquake Engineering Research & Test Center, Guangzhou University, Guangzhou, 510006, China
2)Guangdong Key Laboratory of Earthquake Engineering & Applied Technique, Guangzhou 510006, China

Haibo Jiang:School of Civil and Transportation Engineering, Guangdong Univ. of Technology, Guangzhou, 510006, China

Abstract
This research proposed a particle swarm optimization (PSO) based seismic retrofit design of moment frame structures using a steel frame assembly. Two full scale specimens of the steel frame assembly with different corner details were attached to one-story RC frames for seismic retrofit, and the lateral load resisting capacities of the retrofitted frames subjected to cyclic loads were compared with those of a bare RC frame. The open source software framework Opensees was used to develop an analytical model for validating the experimental results. The developed analytical model and the optimization scheme were applied to a case study structure for economic seismic retrofit design, and its seismic performance was assessed before and after the retrofit. The results show that the developed steel frame assembly was effective in increasing seismic load resisting capability of the structure, and the PSO algorithm could be applied as convenient optimization tool for seismic retrofit design of structures.

Key Words
Particle Swarm Optimization (PSO); seismic performance; seismic retrofit; steel frame

Address
Michael Adane, Seungho Chun and Jinkoo Kim:Department of Global Smart City, Sungkyunkwan University, Suwon Korea

Abstract
Controlling vibrations and noise in steel box girders is important for reducing noise pollution and avoiding discomfort to residents of dwellings along bridges. The fundamental approach to solving this problem involves first identifying the main path of transmission of the vibration energy and then cutting it off by using targeted measures. However, this requires an investigation of the characteristics of flow of vibration energy in the steel box girder, whereas most studies in the area have focused on analyzing its single-point frequency response and overall vibrations. To solve this problem, this study examines the transmission of vibrations through the segments of a steel box girder when it is subjected to harmonic loads through structural intensity analysis based on standard finite element software and a post-processing code created by the authors. We identified several frequencies that dominated the vibrations of the steel box girder as well as the factors that influenced their emergence. We also assessed the contributions of a variety of vibrational waves to power flow, and the results showed that bending waves were dominant in the top plate and in-plane waves in the vertical plate of the girder. Finally, we analyzed the effects of commonly used stiffened structures and steel–concrete composite structures on the flow of vibration energy in the girder, and verified their positive impacts on energy regionalization. In addition to providing an efficient tool for the relevant analyses, the work here informs research on optimizing steel box girders to reduce vibrations and noise in them.

Key Words
composite girder; steel bridge; structural intensity; vibration reduction; vibration transmission

Address
Derui Kong, Cong Li and Keer Cui:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China

Xun Zhang:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
2)State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu 610031, China

Abstract
The fatigue life of steel wire is affected not only by fatigue load, but also by corrosion environment in service period. Specially, the corrosion pit will lead to stress concentration on the surface of steel wire inducing the formation of fatigue cracks, and the fatigue cracks will accelerate the corrosion process. Therefore, the corrosion fatigue of steel wire is a coupling effect. In this study, the corrosion-fatigue coupling life curve is derived with considering corrosion-fatigue pitting stage, corrosion-fatigue short crack stage and corrosion-fatigue long crack stage. In addition, the stress concentration factors of different corrosion pits are calculated by COMSOL software. Furthermore, the effect of corrosion environment factors, that is, corrosion rate, corrosion pit morphology, frequency and action factor of fatigue load, on fatigue life of steel wire is analyzed. And then, the corrosion-fatigue coupling life curve is compared with the fatigue life curve and fatigue life curve with precorrosion. The result showed that the anti-fatigue performance of the steel wire with considering corrosion-fatigue coupling is 68.08% and 41.79% lower than fatigue life curve and fatigue life curve with pre-corrosion. Therefore, the corrosion-fatigue coupling effect should be considered in the design of steel wire.

Key Words
corrosion-fatigue coupling life curve; fatigue life curve with pre-corrosion; fatigue life curve; steel wire

Address
Yang Ding:1)Zhejiang Engineering Research Center of Intelligent Urban Infrastructure, Hangzhou City University, Hangzhou, 310015, China
2)Key Laboratory of Safe Construction and Intelligent Maintenance for Urban Shield Tunnels of Zhejiang Province,
Hangzhou City University, Hangzhou, 310015, China
3)Department of Civil Engineering, Hangzhou City University, Hangzhou 310015, China
4)State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing 400074, China

Xiao-Wei Ye:Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China

Hong Zhang and Xue-Song Zhang:State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing 400074, China


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