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CONTENTS
Volume 47, Number 1, April10 2023
 

Abstract
This paper deals with the free vibration behavior of rotating composite beams reinforced with carbon nanotubes (CNTs) under uniform thermal loads. The temperature-dependent beam material is assumed to be a mixture of single-walled carbon nanotubes (SWCNTs) in an isotropic matrix and five different functionally graded (FG) distributions of CNTs are considered according to the variation along the thickness, namely the UD-uniform, FG-O, FG-V, FG-Λ and FG-X distributions where FG-V and FG-Λ are unsymmetrical patterns. Considering the Timoshenko beam theory (TBT), a new finite element formulation of functionally graded carbon nanotube reinforced composite (FGCNTRC) beam is created for the first time. And the effects of several essential parameters including rotational speed, hub radius, effective material properties, slenderness ratio, boundary conditions, thermal force and moments due to temperature variation are considered in the formulation. By implementing different boundary conditions, some new results of both symmetric and non-symmetrical distribution patterns are presented in tables and figures to be used as benchmark for further validation. In addition, as an alternative advanced composite application for rotating systems exposed to thermal load, the positive effects of CNT addition in improving the dynamic performance of the system have been observed and the results are presented in several tables and figures.

Key Words
carbon nanotube reinforced composite beam; CNTRC; finite element method; functionally graded material; thermal analysis; vibration analysis

Address
Ozge Ozdemir and Huseyin Ural:Department of Aeronautical Engineering, Istanbul Technical University, Istanbul, Turkey

Ismail Esen:Department of Mechanical Engineering, Karabuk University, Karabuk, Turkey

Abstract
An experimental study of eleven PVC-FRP Confined Concrete (PFCC) column-Reinforced Concrete (RC) beam joints reinforced with Core Steel Tube (CST) under axial compression is carried out. All specimens are designed in accordance with the principle of "weak column and strong joint". The influences of FRP strips spacing, length and steel ratio of CST, height and stirrup ratio of joint on mechanical behavior are investigated. As the design anticipated, all specimens are destroyed by column failure. The failure mode of PFCC column-RC beam joint reinforced with CST is the yielding of longitudinal steel bars, CST and stirrups of column as well as the fracture of FRP strips and PVC tube. The ultimate bearing capacity decreases as FRP strips spacing or joint height increases. The effects of other three studied parameters on ultimate bearing capacity are not obvious. The strain development rules of longitudinal steel bars, PVC tube, FRP strips, column stirrups and CST are revealed. The effects of various studied parameters on stiffness are also examined. Additionally, an influence coefficient of joint height is introduced based on the regression analysis of test data, a theoretical formula for predicting bearing capacity is proposed and it agrees well with test data.

Key Words
bearing capacity; column; confinement; joint; PVC-FRP; stiffness; stirrup ratio

Address
Ping Wu, Dongang Li, Feng Yu, Yuan Fang, Guosheng Xiang and Zilong Li:Department of Civil Engineering and Architecture, Anhui University of Technology, Maxiang Road 5, Maanshan, China

Abstract
This paper presented an investigation into steel tubes encased high-strength concrete (STHC) composite walls, wherein steel tubes were embedded at the boundary elements of high-strength concrete walls. A series of cyclic loading tests was conducted to evaluate the failure pattern, hysteresis characteristics, load-bearing capacity, deformability, and strain distribution of STHC composite walls. The test results demonstrated that the bearing capacity and ductility of the STHC composite walls improved with the embedding of steel tubes at the boundary elements. An analytical method was then established to predict the flexural bearing capacity of the STHC composite walls, and the calculated results agreed well with the experimental values, with errors of less than 10%. Finally, a finite element modeling (FEM) was developed via the OpenSees program to analyze the mechanical performance of the STHC composite wall. The FEM was validated through test results; additionally, the influences of the axial load ratio, steel tube strength, and shear-span ratio on the mechanical properties of STHC composite walls were comprehensively investigated.

Key Words
composite walls; FEM analysis; high-strength concrete; mechanical behavior; steel tube

Address
Liang Bai, Huilin Wei, Bin Wang, Fangfang Liao and Tianhua Zhou:School of Civil Engineering, Chang

Abstract
In tied-arch bridges, a properly designed connection between the arch and the deck may become crucial, since the forces in the structure may be significantly reduced. This implies substantial material savings and, consequently, cheaper constructions. The introduction of the Nielsen cable arrangement (composed of V-shaped inclined hangers) in the last century was a milestone because it was able to reduce deflections and bending moments both in the arch and in the deck. So far, the Nielsen cable arrangement has proven to be successful in traditional vertical arch bridges. However, despite its advantages, it has not been widely applied to spatial arch bridges. Thus, this article analyses the difference between the structural behavior of spatial arch bridges with Nielsen-type cable arrangements with respect to those with classical vertical hanger configurations. The main goal is to verify whether the known effectiveness of the Nielsen cable arrangement for classical arch bridges is still preserved when applied to spatial arch bridges. In order to achieve this objective, and as the first part of our study, a set of different all-steel bridges composed of vertical and inclined arches with straight decks have been compared for both cable arrangements. As a major conclusion, for planar vertical arch bridges, the Nielsen-type cable arrangement is always the most effective. In addition, it also seems that, for spatial arch bridges composed of a straight deck and an inclined arch, it still keeps most of its effectiveness as long as the arch is moderately inclined.

Key Words
arch bridge; cable arrangement; eccentric arch; inclined arch; Nielsen-Lohse; spatial arch bridge; tied-arch bridge

Address
Mirian Canovas-Gonzalez, Juan M. García-Guerrero and Juan J. Jorquera-Lucerga: Civil Engineering Department, Universidad Politécnica de Cartagena (UPCT), Paseo Alfonso XIII, 52, Cartagena 30203, Spain

Abstract
This paper presents a study on the wave propagation of functionally graded material (FGM) sandwich nanoplates with soft core resting on a Winkler foundation. The structure is modelled by classical theory. Motion equations are derived by the assumption of nonlocal Eringen theory and energy method. Then, the equations are solved using an exact method for finding phase velocity responses. The effects of Winkler foundation, nonlocal parameters, thickness and mode number on the dispersion of elastic waves are shown. With the increase of spring constant, the speed of wave propagation increases and reaches a uniform state at a higher wave number.

Key Words
exact solution; nonlocal Eringen theory; sandwich FGM nanoplate; wave propagation; Winkler foundation

Address
Amir Behshad:Faculty of Technology and Mining, Yasouj University, Choram 75761-59836, Iran

Maryam Shokravi:Department of Education, Mehrab High School, Saveh, Iran


Akbar Shafiei Alavijeh and Hamed Karami:Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran

Abstract
Nonlinear forced vibration properties of three-layered plates containing graphene platelets (GPL) filled skins and an auxetic core have been inquired within the present paper. Owning reduced weight as well as reduced stiffness, rectangle-shaped auxetic cores have been frequently made from novel techniques such as additive manufacturing. Here, the rectangle shape core is amplified via the graphene-filled layers knowing that the layers possess uniform and linear graphene gradations. The rectangle shape core has the equivalent material specifications pursuant to relative density value. The sandwich plate is formulated pursuant to Kirchhoff plate theory while a numerical trend has been represented to discretize the plate equations. Next, an analytical trend has been performed to establish the deflection-frequency plots. Large deflections, core density and GPL amplification have showed remarkable impacts on dynamic response of three-layered plates.

Key Words
composites; design; dynamics; forced vibrations; numerical method; sandwich panels

Address
Yong Huang:1)State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University,
Urumqi 830017, Xinjiang, PR China
2)College of Civil Engineering and Architecture, Xinjiang University, Urumqi 830017, Xinjiang, PR China
3)Xinjiang Communication Construction Co.Ltd. (XCCG), Urumqi 830000, Xinjiang, PR China
4)Chengdu University of Technology, Chengdu 610000, Sichuan, PR China
5)Transpotation Industry Highway Maintenance Collaborative Innovation Platform under Complicated Conditions of Western China,
Urumqi 830000, Xinjiang, PR China
6)Western Sub-Alliance of Zhongguancun Zhongke Highway Maintenance Technology Innovation Alliance,
Urumqi 830000, Xinjiang, PR China

Zengshui Liu, Shihan Ma and Sining Li:State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University,
Urumqi 830017, Xinjiang, PR China

Rui Yu:College of Civil Engineering and Architecture, Xinjiang University, Urumqi 830017, Xinjiang, PR China

Abstract
To study the evaluation standard and control limit of mortar filling layer void length, in this paper, the train submodel was developed by MATLAB and the track-bridge sub-model considering the mortar filling layer void was established by ANSYS. The two sub-models were assembled into a train-track-bridge coupling dynamic model through the wheel-rail contact relationship, and the validity was corroborated by the coupling dynamic model with the literature model. Considering the randomness of fastening stiffness, mortar elastic modulus, length of mortar filling layer void, and pier settlement, the test points were designed by the Box-Behnken method based on Design-Expert software. The coupled dynamic model was calculated, and the support vector regression (SVR) nonlinear mapping model of the wheel-rail system was established. The learning, prediction, and verification were carried out. Finally, the reliable probability of the amplification coefficient distribution of the response index of the train and structure in different ranges was obtained based on the SVR nonlinear mapping model and Latin hypercube sampling method. The limit of the length of the mortar filling layer void was, thus, obtained. The results show that the SVR nonlinear mapping model developed in this paper has a high fitting accuracy of 0.993, and the computational efficiency is significantly improved by 99.86%. It can be used to calculate the dynamic response of the wheel-rail system. The length of the mortar filling layer void significantly affects the wheel-rail vertical force, wheel weight load reduction ratio, rail vertical displacement, and track plate vertical displacement. The dynamic response of the track structure has a more significant effect on the limit value of the length of the mortar filling layer void than the dynamic response of the vehicle, and the rail vertical displacement is the most obvious. At 250 km/h – 350 km/h train running speed, the limit values of grade 1,2 and 3 of the lengths of the mortar filling layer void are 3.932 m, 4.337 m, and 4.766 m, respectively. The results can provide some reference for the long-term service performance reliability of the ballastless track-bridge system of HRS.

Key Words
amplification factor; mapping model; reliability theory; support vector machine; vehicle body acceleration

Address
Binbin He and Sheng Wen:1)School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China
2)State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure,Nanchang 330013, China

Yulin Feng:1)School of Civil Engineering and Architecture, East China Jiaotong University, Nanchang 330013, China
2)State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure,Nanchang 330013, China
3)Central South University, National Engineering Research Center of High-speed Railway Construction Technology, Changsha 410075, China

Lizhong Jiang and Wangbao Zhou:Central South University, National Engineering Research Center of High-speed Railway Construction Technology, Changsha 410075, China

Abstract
This paper presents an investigation on the shear resistance of corrugated web steel beams (CWBs) with a circular web opening. A total of five specimens with different diameters of web openings were designed and tested with vertical load applied on the top flange at mid-span. The ultimate strengths, failure modes, and load versus middle displacement curves were obtained from the tests. Following the tests, numerical models of the CWBs were developed and validated against the test results. The influence of the web plate thickness, steel grade, opening diameter, and location on the shear strength of the CWBs was extensively investigated. An XGBoost machine learning model for shear resistance prediction was trained based on 256 CWB samples. The XGBoost model with optimal hyperparameters showed excellent accuracy and exceeded the accuracy of the available design equations. The effects of geometric parameters and material properties on the shear resistance were evaluated using the SHAP method.

Key Words
circular web opening; corrugated web steel beam; experimental study; machine learning; inelastic shear buckling; shear strength

Address
Yan-Wen Li:1)State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
2)Department of Architecture and Architectural Engineering, Kyoto University, Kyoto, Japan

Guo-Qiang Li:State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China

Lei Xiao:1)State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
2)Department of Building & Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China

Michael C.H. Yam:Department of Building & Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China

Jing-Zhou Zhang:1)State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
2)Department of Building & Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China

Abstract
This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

Key Words
composite column; concrete-filled steel tube; damage model; loading system; performance level

Address
Xiaojun Ke:1)College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China
2)Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, Guangxi University, Nanning 530004, China

Haibin Wei, Linjie Yang and Jin An:College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China

Abstract
This study presents a numerical investigation into the hysteretic behavior of cold-formed austenitic stainless steel square hollow section (SHS) brace members using a commercial finite element (FE) analysis software ABAQUS/Standard. The initial/post buckling and fracture life of SHS brace members are comprehensively investigated through parametric studies with FE models incorporating ductile fracture model, which is validated against the existing laboratory test results collected from the literature. It is found that the current predictive models are applicable for the initial buckling strengths of SHS brace members under cyclic loading, while result in significant inaccuracy in predictions for the post-buckling strength and fracture life. The modified predictive model is therefore proposed and the applicability was then confirmed through excellent comparisons with test results for cold-formed austenitic stainless SHS brace members.

Key Words
austenitic stainless steel; brace; buckling; fracture life; hysteretic behavior; seismic design; square hollow section

Address
YongHyun Cho:Sustainable Building Research Center, Hanyang University ERICA, Ansan 15588, Republic of Korea

Fangying Wang:Department of Civil Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom

TaeSoo Kim:School of Architecture and Architectural Engineering, Hanyang University ERICA, Ansan 15588, Republic of Korea

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