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CONTENTS
Volume 50, Number 6, March 25 2024
 

Abstract
This paper presents an in-depth analysis of the nonlinear vibration of microbeams, with a particular emphasis on their application in sports monitoring systems. The research utilizes classical beam theory, modified couple stress theory, and von-Kármán nonlinear parameters to explore the behavior of microbeams. These microbeams are characterized by a nonuniform geometry, with materials that continuously change along the beam radius and a thickness that varies along the beam length. The main contribution lies in its exploration of the stability of smart sensors in sports structures, particularly those with non-uniform geometries. The research findings indicate that these non-uniform microbeams, when used in smart systems made of functionally graded temperature-dependent materials, can operate effectively in thermal environments. The smart system developed in this study demonstrates significant potential for use in sports applications, particularly in monitoring and gathering information. The insights gained from this research contribute to the understanding of the performance and optimization of microbeams in sports applications, particularly in the context of non-uniform geometries. This research, therefore, provides a foundation for the development of advanced, reliable, and efficient monitoring systems in sports applications.

Key Words
nonlinear vibration; numerical analysis; sport application; sport monitoring; thermal sensor

Address
Yi Zhang:Jieyang polytechnic, Department of Art and Sports, Jieyang 522000, Guangdong, China

Maryam Bagheri:Hoonam Sanat Farnak, Engineering and technology company, Ilam, Iran

Abstract
This paper presents an experimental and numerical study to investigate the behavior of the precast segmental concrete beams (PSCBs) utilizing high-strength concrete (HSC) connected in the zone of the maximum bending moment using steel extended endplate connections (EECs). The experimental study consisted of five beams as follows: The first beam was the control beam for comparison, which was an unconnected one-piece beam made of HSC. The other four other beams consisted of two identical pieces of precast concrete. An important point to be noted is that at the end of each piece, a steel plate was used with a thickness of 10 mm. Moreover, this steel plate was welded to the lower and upper reinforcing bars of the beam. Furthermore, the steel plate was made to connect the two pieces using the technique of EECs. Several variables were taken in these four beams, whether from the shape of the connection or enhancing the behavior of the connection using the posttensioning technique. EECs without stiffeners were used for some of the tested beams. The behavior of these connections was improved using stiffeners and shear bolts. To get accurate results, a comparison was made between the behaviors of the five beams. Another important point to be noted is that Abaqus and SAP2000 programs were used to investigate the behavior of PSCBs and to ensure the accuracy of the modeling process which showed a good agreement with the experimental results. Additionally, the simplified modeling using SAP2000 was able to model the nonlinear behavior of PSCBs connected using steel EECs. It was found that the steel pre-tensioned bolted EECs, reinforced with steel stiffeners and shear anchors, could be used to connect the precast HSC segmental beams via the internal pre-stressing technique.

Key Words
extended endplate connections; finite element analysis; high-strength concrete; internal pre-stressing; moment connections; precast segmental beams

Address
Magdy I. Salama:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh 33511, Egypt

Jong Wan Hu:1)Department of Civil and Environmental Engineering, Incheon National University, Incheon 22012, South Korea 2)Incheon Disaster Prevention Research Center, Incheon National University, Incheon 22012, South Korea

Ahmed Almaadawy:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh 33511, Egypt

Ahmed Hamoda:Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh 33511, Egypt

Basem O. Rageh:Civil Engineering Department., Delta Higher Institute for Engineering and Technology, Mansoura 35511, Egypt

Galal Elsamak:1)Department of Civil Engineering, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh 33511, Egypt
2)Civil Engineering Department., Delta Higher Institute for Engineering and Technology, Mansoura 35511, Egypt

Abstract
The main aim of this study is to quantify the code seismic design coefficients of the RCS system, which consisted of reinforced concrete columns and steel beams, based on the FEMA P-695 methodology. The underlying intention is to evaluate the seismic performance of the RCS system at the system level rather than the connection level. A set of 24 archetype buildings with a various number of stories, beam span lengths, gravity load levels, and seismic load levels are selected and designed based on the prevailing code requirements. Nonlinear analytical models are developed and validated by experimental tests. The pushover and response history dynamic analyses are conducted to evaluate the required data in the performance quantification process. The results show that the design coefficients suggested by the code are acceptable. However, the level of conservatism is very high. Thus, it is possible to use a larger R-factor in the design process or make some relaxations in the design requirements related to this structural system.

Key Words
composite structure; earthquake engineering; moment-resisting frame system; nonlinear modeling; seismic design coefficients

Address
Elmira Tavasoli Yousef Abadi and Mohammad T. Kazemi:Department of Civil Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran


Abstract
Casting Ultra High-Performance Concrete (UHPC) on an orthotropic steel deck and forming a composite action by connectors could improve the steel deck fatigue performance. This study presents the mechanical performance of a proposed post-combination connection between UHPC and steel, which had a low constraint effect on UHPC shrinkage. A total of 10 push-out tests were conducted for static and fatigue performance investigations. And the test results were compared with evaluation methods in codes to verify the latter's applicability. Meanwhile, nonlinear simulation and parametric works with material damage plasticity models were also conducted for the static and fatigue failure mechanism understanding. The static and fatigue test results both showed that fractures at stud roots and surrounding local UHPC crushes were the main failure appearances. Compared with normally arranged studs, group arrangement could result in reductions of static stud shear stiffness, strength, and fatigue lives, which were about 18%, 12%, and 27%, respectively. Compared with the test results, stud shear capacity and fatigue lives evaluations based on the codes of AASHTO, Eurocode 4, JSCE and JTG D64 could be applicable in general while the safety redundancies tended to be smaller or even insufficient for group studs. The analysis results showed that arranging studs in groups caused obviously uneven strain distributions. The severer stress concentration and larger strain ranges caused the static and fatigue performance degradations of group studs. The research outcome provides a very important basis for establishing a design method of connections in the novel post-combination steel-UHPC composite deck.

Key Words
failure development; group studs; numerical analysis; push-out test; steel-UHPC composite bridge deck

Address
Han Xiao: Department of Bridge Engineering, Tongji University, Shanghai 200092, China

Wei Wang:Shanghai Municipal Engineering Design Institute (Group) Co. Ltd., Shanghai 200092, China

Chen Xu:Department of Bridge Engineering, Tongji University, Shanghai 200092, China

Sheraz Abbas:Department of Bridge Engineering, Tongji University, Shanghai 200092, China

Zhiping Lin:Fujian Expressway Group Co. Ltd, Fujian, China


Abstract
Cold-formed steel (CFS) is prone to buckling failure under loading. Lightweight concrete (LC) made of lightweight aggregate has light weight and excellent thermal insulation performance. However, concrete is brittle in nature which is why different materials have been used to improve this inherent behavior of concrete. The distortional buckling (DB) performance of cold-formed steel-lightweight concrete (CFS-LC) composite columns was investigated in this paper. Firstly, the compressive strength test of foam concrete (FC) and ceramsite concrete (CC) was carried out. The performance of the CFS-LC members was investigated. The test results indicated that the concrete-filled can effectively control the DB of the members. Secondly, finite element (FE) models of each test specimen were developed and validated with the experimental tests followed by extensive parametric studies using numerical analysis based on the validated FE models. The results show that the thickness of the steel and the strength of the concrete-filled were the main factors on the DB and bearing capacity of the members. Finally, the bearing capacity of the test specimens was calculated by using current codes. The results showed that the design results of the AIJ-1997 specification were closer to the experimental and FE values, while other results of specifications were conservative.

Key Words
bearing capacity; cold-formed steel lightweight-concrete composite column; distortional buckling; experiment; numerical simulation

Address
Yanchun Li, Aihong Han, , Jihao Chen, Yanfen Xie and Jiaojiao Chen:School of Civil Engineering and Communication, North China University of Water Resources and Electric Power, Zhengzhou 450045, China

Ruibo Li:Yuxing Construction Company, Zhengzhou 450011, China

Abstract
Construction of high-rise structures, formwork systems that can be installed quickly, resistant to external loads, can be used more than once, have become a necessity. Timber and composite timber materials are preferred in the formation of such formwork systems due to their durability, ease of assembly, light weight and easy to use more than one time. Formwork beams are the most commonly used structural component in the formation of such formwork systems, and these beams can be damaged for different reasons during their lifetime. In this study, H20 top P type timber formwork beams with 1800 and 2450 mm length which is among the products of DOKA(c) company is damaged under the effect of static loading up to a high load level of 85% of the maximum ultimate capacity and after being retrofitted using anchored CFRP strips, performance and behavior of the beams under the influence of various loading types such as static, fatigue and impact are investigated experimentally. Two different lengths of retrofitted timber formwork beams were tested by applying monotonic static, fatigue and impact loading and comments were made about the effects of the retrofit method on performance under different loading types.

Key Words
carbon fibers; fatigue; Finite element analysis (FEA); impact load; wood fibers

Address
Abdullah TURER:Civil Eng. Dept., Ankara Yildirim Beyazit University, Ankara, Turkiye

Ozgur ANIL:Civil Eng. Dept., Gazi University, Ankara, Turkiye

Abdulkadir CEViK:Civil Eng. Dept., Gaziantep University, Gaziantep, Turkiye

R. Tugrul Erdem:Civil Eng. Dept., Manisa Celal Bayar University, Manisa, Turkiye

Abstract
Analyzing the collapse behavior of thin-walled steel structures holds significant importance in ensuring their safety and longevity. Geometric imperfections present on the surface of metal materials can diminish both the durability and mechanical integrity of steel shells. These imperfections, encompassing local geometric irregularities and deformations such as holes, cavities, notches, and cracks localized in specific regions of the shell surface, play a pivotal role in the assessment. They can induce stress concentration within the structure, thereby influencing its susceptibility to buckling. The intricate relationship between the buckling behavior of these structures and such imperfections is multifaceted, contingent upon a variety of factors. The buckling analysis of thin-walled steel shell structures, similar to other steel structures, commonly involves the determination of crucial material properties, including elastic modulus, shear modulus, tensile strength, and fracture toughness. An established method involves the emulation of distributed geometric imperfections, utilizing real test specimen data as a basis. This approach allows for the accurate representation and assessment of the diversity and distribution of imperfections encountered in real-world scenarios. Utilizing defect data obtained from actual test samples enhances the model's realism and applicability. The sizes and configurations of these defects are employed as inputs in the modeling process, aiding in the prediction of structural behavior. It's worth noting that there is a dearth of experimental studies addressing the influence of geometric defects on the buckling behavior of cylindrical steel shells. In this particular study, samples featuring geometric imperfections were subjected to experimental buckling tests. These same samples were also modeled using Finite Element Analysis (FEM), with results corroborating the experimental findings. Furthermore, the initial geometrical imperfections were measured using digital image correlation (DIC) techniques. In this way, the response of the test specimens can be estimated accurately by applying the initial imperfections to FE models. After validation of the test results with FEA, a numerical parametric study was conducted to develop more generalized design recommendations for the stainless-steel shell structures with the initial geometric imperfection. While the load-carrying capacity of samples with perfect surfaces was up to 140 kN, the load-carrying capacity of samples with 4 mm defects was around 130 kN. Likewise, while the load carrying capacity of samples with 10 mm defects was around 125 kN, the load carrying capacity of samples with 14 mm defects was measured around 120 kN.

Key Words
cylindrical shell; DIC; dimple-shaped; FEA; initial imperfection; stainless steel

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

Ozer Zeybek:Department of Civil Engineering, Faculty of Engineering, Mugla Sitki Kocman University, Mugla, 48000, Turkey

Yasin Onuralp Ozkilic:1)Department of Civil Engineering, Faculty of Engineering, Necmettin Erbakan University, Konya 42000, Turkey
2)Department of Civil Engineering, Lebanese American University, Byblos, Lebanon
5World-Class Research Center "Advanced Digital Technologies", State Marine Technical University,
Saint Petersburg, 190121, Russian Federation

Abstract
In this research, the efficiency of a metallic energy dissipation device for seismic retrofit of an existing structure is evaluated by cyclic loading test. The proposed device, which is called multi-slit damper, is made of weak and strong slit dampers connected in series. Its energy dissipation mechanism consists of two stages: (i) yielding of the weak-slit damper under minor earthquakes; (ii) restraint of further deformations of the weak slit damper and activation of the strong slit damper under major earthquakes using a gap mechanism. A reinforced concrete (RC) frame with characteristics similar to soft-first-story structures is tested under cyclic loading before and after retrofit using the proposed device. The details of the experimental study are described and the test is simulated in an available commercial software to validate the analytical model of the damper. To further verify the applicability of the damper, it is applied to an analysis model of a 4-story structure with soft first story and its seismic performance is evaluated before and after retrofit. The experimental and analysis results show that the multi-slit damper is effective in controlling seismic response of structures.

Key Words
nonlinear analysis; reinforced concrete; seismic performance; seismic retrofit; slit damper

Address
Mohammad Mahdi Javidan:Department of Global Smart City, Sungkyunkwan University, Suwon, Republic of Korea

Jinkoo Kim:Department of Global Smart City, Sungkyunkwan University, Suwon, Republic of Korea

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