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CONTENTS
Volume 42, Number 2, January25 2022
 

Abstract
This study discusses a hypothetical method for tracking the propagation damage of Carbon Reinforced Fiber Plastic (CRFP) components underneath vibration fatigue. The High Cycle Fatigue (HCF) behavior of composite materials was generally not as severe as this of admixture alloys. Each fissure initiation in metal alloys may quickly lead to the opposite. The HCF behavior of composite materials is usually an extended state of continuous degradation between resin and fibers. The increase is that any layer-to-layer contact conditions during delamination opening will cause a dynamic complex response, which may be non-linear and dependent on temperature. Usually resulted from major deformations, it could be properly surveyed by a non-contact investigation system. Here, this article discusses the scanning laser application of that vibrometer to track the propagation damage of CRFP components underneath fatigue vibration loading. Thus, the study purpose is to demonstrate that the investigation method can implement systematically a series of hypothetical means and dynamic characteristics. The application of the relaxation method based on numerical simulation in the Artificial Intelligence (AI) Evolved Bat (EB) strategy to reduce the dynamic response is proved by numerical simulation. Thermal imaging cameras are also measurement parts of the chain and provide information in qualitative about the temperature location of the evolution and hot spots of damage.

Key Words
artificial intelligence; CRFP components; evolved bat; propagation damage; scanning LDV

Address
Z.Y. Chen: Guangdong University of Petrochem Technol, Sch Sci, Maoming 525000, China

Sheng-Hsiang Peng: Department of Civil and Environmental Engineering, University of California, Irvine, CA, 92697, U.S.A.

Yahui Meng: Guangdong University of Petrochem Technol, Sch Sci, Maoming 525000, China

Ruei-Yuan Wang: Guangdong University of Petrochem Technol, Sch Sci, Maoming 525000, China

Qiuli Fu: School of Computer Sci, Guangdong University of Petrochem Technol, Maoming 525000, China

Timothy Chen: 4Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, U.S.A.



Abstract
In this paper, four specimens of CFST column joints with endplates and long bolts are tested in the scenario of progressive collapse. Flush endplate and extended endplate are both adopted in this study. The experimental results show that increasing the thickness of the endplate could improve the behavior of the joint, but delay the mobilization of catenary action. The thickness of the endplate should not be relatively thick in comparison to the diameter of the bolts, otherwise catenary action would not be mobilized or work effectively. Effective bending deformation of the endplate could help the formation and development of catenary action in the joints. The performance of flexural action in the joint would affect the formation of catenary action in the joint. Extra middle-row bolts set at the endplates and structural components set below the bottom beam flange should be used to enhance the robustness of joints. A special weld access hole between beam and endplate should be adopted to mitigate the chain damage potential of welds. It is suggested that the structural components of joints should be independent of each other to enhance the robustness of joints. Based on the component method, a formula calculating the stiffness coefficient of preloaded long bolts was proposed whose results matched well with the experimental results.

Key Words
catenary action; CFST; component method; endplate; long bolts; progressive collapse

Address
Shan Gao:1)Shaanxi Key Laboratory of safety and durability of concrete structures, Xijing University, Xi'an University
2) School of Civil Engineering, Harbin Institute of Technology, Harbin, China
3)School of Civil Engineering, Chongqing University, Chongqing, China

Bo Yang: School of Civil Engineering, Chongqing University, Chongqing, China

Lanhui Guo: School of Civil Engineering, Harbin Institute of Technology, Harbin, China

Feng Fu: School of Mathematics, Computer Science & Engineering, University of London, London, U.K.

Abstract
With the development of spatial structures, the joints are becoming more and more complex to connect tubular members of spatial structures. In this study, an approach is proposed to establish high-efficiency finite element model of multiplanar KTX-joint with the weld geometries accurately simulated. Ultimate bearing capacity the KTX-joint is determined by the criterion of deformation limit and failure mechanism of chord wall buckling is studied. Size effect of fillet weld on the joint ultimate bearing capacity is preliminarily investigated. Based on the validated finite element model, a parametric study is performed to investigate the effects of geometric and loading parameters of KT-plane brace members on ultimate bearing capacity of the KTX-joint. The effect mechanism is revealed and several design suggestions are proposed. Several simple reinforcement methods are adopted to constrain the chord wall buckling. It is concluded that the finite element model established by proposed approach is capable of simulating static behaviors of multiplanar KTX-joint; chord wall buckling with large indentation is the typical failure mode of multiplanar KTX-joint, which also increases chord wall displacements in the axis directions of brace members in orthogonal plane; ultimate bearing capacity of the KTX-joint increases approximately linearly with the increase of fillet weld size within the allowed range; the effect mechanism of geometric and loading parameters are revealed by the assumption of restraint region and interaction between adjacent KT-plane brace members; relatively large diameter ratio, small overlapping ratio and small included angle are suggested for the KTX-joint to achieve larger ultimate bearing capacity; the adopted simple reinforcement methods can effectively constrain the chord wall buckling with the design of KTX-joint converted into design of uniplanar KT-joint.

Key Words
failure mechanism; geometric and loading effects; multiplanar KTX-joint; parametric study; preliminary reinforcement; ultimate bearing capacity

Address
Chenhui Zhang: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Bo Zou: College of Civil Engineering, Tongji University, Shanghai 200092, China


Guotao Yang: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Abstract
Undoubtedly, the employment of direct bond interaction between steel and concrete is preceding the other mechanisms because of its ease of construction. However, the large scatter in the experimental data about the issue has hindered the efforts to characterize bond strength. In the following research, the direct bond interaction and bond-slip behavior of CFTs with circular cross-section were examined through repeated load-reversed push-out tests until four cycles of loading. The influence of different parameters including the diameter of the tube and the use of shear tabs were assessed. Moreover, the utilization of expansive concrete and external spirals was proposed and tested as ways of improving bond strength. According to the results section dimensions, tube slenderness, shrinkage potential of concrete, interface roughness and confinement are key factors in a natural bond. Larger diameters will lead to a considerable drop in bond strength. The use of shear tabs by their associated bending moments increases the bond stress up to eight times. Furthermore, employment of external spirals and expansive concrete have a sensible effect on enhancing bonds. Macro-locking was also found to be the main component in achieving bond strength.

Key Words
concrete-filled steel tube (CFT); load transfer; bond strength; push-out test; macro-locking

Address
Morteza Naghipour: Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran

Aidin Khalili: Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran

Seyed Mohammad Reza Hasani: Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran

Mahdi Nematzadeh: Department of Civil Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran



Abstract
Offshore platforms in seismically active areas must be designed to survive in the face of intense earthquakes without a global structural collapse. This paper scrutinizes the seismic performance of a newly designed and established jacket type offshore platform situated in the entrance of the Gulf of Suez region based on the API-RP2A normalized response spectra during seismic events. A nonlinear finite element model of a typical jacket type offshore platform is constructed taking into consideration the effect of structure-soil-interaction. Soil properties at the site were manipulated to generate the pile lateral soil properties in the form of load deflection curves, based on API-RP2A recommendations. Dynamic characteristics of the offshore platform, the response function, output power spectral density and transfer functions for different elements of the platform are discussed. The joints deflection and acceleration responses demands are presented. It is generally concluded that consideration of the interaction between structure, piles and soil leads to higher deflections and less stresses in platform elements due to soil elasticity, nonlinearity, and damping and leads to a more realistic platform design. The earthquake-based analysis for offshore platform structure is essential for the safe design and operation of offshore platforms.

Key Words
offshore platform; random vibration; response function; response spectrum analysis; seismic performance

Address
Shehata E. Abdel Raheem: Civil Engineering Dept., Faculty of Engineering, Assuit University, Assiut71516, Egypt

Elsayed M. Abdel Aal: Offshore Projects Engineer, Egypt Gas Company, Egypt

Aly G.A. AbdelShafy: Civil Engineering Dept., Faculty of Engineering, Assuit University, Assiut71516, Egypt

Mohamed F.M. Fahmy: Civil Engineering Dept., Faculty of Engineering, Assuit University, Assiut71516, Egypt


Abstract
Perfobond rib connectors are widely used in composite structures to achieve the composite action between the steel and the concrete, and empirical expressions for their strength and secant stiffness have been obtained by numerical simulations or push-out tests. Since perfobond connections are generally in an elastic state in the service process and the structural analysis are always based on the elastic properties of the members, the secant stiffness is not applicable for the normal structural analysis. However, the tangent stiffness of perfobond connections has not been introduced in previous studies. Moreover, the perfobond connections are bearing tension and shear force simultaneously when the composite beams subjected to torque or local loads, but the current studies fail to arrive at the elastic stiffness considering the combined effects. To resolve these discrepancies, this paper investigates the initial elastic stiffness of perfobond connections under combined forces. The calculation method for the elastic stiffness of perfobond connections is analyzed, and the contributions of the perfobond rib, the perforating rebar and the concrete dowel are investigated. A finite element method was verified with a high value of correlation for the test results. Afterwards, parametric studies are carried out using the reliable finite element analysis to explore the trends of several factors. Empirical equations for predicting the initial elastic stiffness of perfobond connections are proposed by the numerical regression of the data extracted by parametric studies. The equations agree well with finite element analysis and test results, which indicates that the proposed empirical equations reflect a high accuracy for predicting the initial elastic stiffness of perfobond connections.

Key Words
composite structure; design equation; finite element analysis; initial elastic stiffness; perfobond connector

Address
Xi Qin: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Guotao Yang: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Abstract
A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1−continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

Key Words
boundary finite element (BEM); finite element method (FEM); functionally graded carbon nanotubereinforced composite (FG-CNTRC); hydroelastic analysis; moving loads

Address
Vu X. Nguyen:1) Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet
Street, Ward 14, District 10, Ho Chi Minh City, Vietnam
2) Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Qui X. Lieu: 1) Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet
Street, Ward 14, District 10, Ho Chi Minh City, Vietnam
2) Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Tuan A. Le: 1) Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet
Street, Ward 14, District 10, Ho Chi Minh City, Vietnam
2) Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Thao D. Nguyen: 1) Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet
Street, Ward 14, District 10, Ho Chi Minh City, Vietnam
2) Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Takayuki Suzuki: Department of Civil Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogayaku, Yokohama 240-8501, Japan

Van Hai Luong: 1) Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet
Street, Ward 14, District 10, Ho Chi Minh City, Vietnam
2) Vietnam National University Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Abstract
The analysis of the progressive collapse resistance of structures is a well-known issue among structural engineers. Large-span reticulated dome structures are commonly utilized in large public buildings, necessitating research into their progressive collapse resistance to assure user safety. The most significant part of improving the structural resilience of reticulated domes is to evaluate their key elements. Based on a stiffness-based evaluation approach, this work offers a calculating procedure for element importance coefficient. For both original and damaged structures, evaluations are carried out using the global stiffness matrix and the determinant. The Kiewitt, Schwedler, and Sunflower reticulated domes are investigated to explore the distribution characteristic of element importance coefficients in the single-layer dome structures. Moreover, the influence of the load levels, load distributions, geometric parameters and topological features are also discussed. The results can be regarded as the initial concept design reference for single-layer reticulated domes.

Key Words
importance coefficient; single-layer domes; stiffness; geometry; topology

Address
Qian Zhang:1) National Prestress Engineering Research Center, Key Laboratory of C & PC Structures of Ministry of Education Southeast University,
Nanjing 210096, China 2) Department of Structural Engineering and Building Materials, Faculty of Engineering and Architecture, Ghent University,
Valentin Vaerwyckweg 1, 9000 Ghent, Belgium

Wenxing Huang: School of Aerospace, The University of Nottingham Ningbo China. No.199 Taikang East Road, Ningbo, 315100, China

Yixiang Xu: School of Aerospace, The University of Nottingham Ningbo China. No.199 Taikang East Road, Ningbo, 315100, China

Jianguo Cai: National Prestress Engineering Research Center, Key Laboratory of C & PC Structures of Ministry of Education Southeast University,
Nanjing 210096, China

Fang Wang: National Prestress Engineering Research Center, Key Laboratory of C & PC Structures of Ministry of Education Southeast University,
Nanjing 210096, China

Jian Feng: National Prestress Engineering Research Center, Key Laboratory of C & PC Structures of Ministry of Education Southeast University,
Nanjing 210096, China


Abstract
A new type of precast steel reinforced concrete (PSRC) column was put forward in this paper. In order to study the static performance of PSRC column and hollow precast steel reinforced concrete (HPSRC) column subjected to combined compression and shear loading, a parametric test was carried out and effects of axial compression ratio, concrete strength and shear ratio on the mechanical behavior of composite PSRC column and HPSRC column were explored. In addition, the cracks development, load-span displacement relationship, strain distribution and shear bearing strength of column specimens were emphatically focused. Test results implied that shear failure of all specimens occurred during the test, and higher strength of castin-place concrete, smaller shear ratio and larger axial compression ratio could lead to greater shear resistance, but when the axial compression ratio was larger than 0.36, the shear capacity began to decrease gradually. Furthermore, truss-arch model for determining the shear strength of PSRC column and HPSRC column was proposed and the calculated results obtained from proposed method were verified to be valid.

Key Words
compression and shear test; mechanical behavior; precast SRC column; shear capacity

Address
Yang Chen: 1) Department of Civil Engineering, Shanghai University, Shanghai, 200444, China
2) State Key Laboratory of Green Building in Western China, Xi

Abstract
A novel flat steel plate-concrete-corrugated steel plate (FS-C-CS) sandwich panel was proposed for resisting impact load. The failure mode, impact force and displacement response of the FS-C-CS panel under impact loading were studied via drop-weight impact tests. The combined global flexure and local indentation deformation mode of the FS-C-CS panel was observed, and three stages of impact process were identified. Moreover, the effects of corrugated plate height and steel plate thickness on the impact responses of the FS-C-CS panels were quantitatively analysed, and the impact resistant performance of the FS-C-CS panel was found to be generally improved on increasing corrugated plate height and thickness in terms of smaller deformation as well as larger impact force and post-peak mean force. The Finite Element (FE) model of the FS-C-CS panel under impact loading was established to predict its dynamic response and further reveal its failure mode and impact energy dissipation mechanism. The numerical results indicated that the concrete core and corrugated steel plate dissipated the majority of impact energy. In addition, employing end plates and high strength bolts as shear connectors could prevent the slip between steel plates and concrete core and assure the full composite action of the FS-C-CS panel.

Key Words
drop-weight impact test; failure mode; finite element simulation; impact response; steel-concrete-steel panel

Address
Jingyi Lu:1) Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
2) Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology,
Harbin Institute of Technology, Harbin 150090, China

Yonghui Wang:1) Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
2) Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology,
Harbin Institute of Technology, Harbin 150090, China

Ximei Zhai: 1) Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
2) Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology,
Harbin Institute of Technology, Harbin 150090, China

Hongyuan Zhou: Key Lab of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China




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