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Volume 41, Number 4, November25 2021

The ability to estimate the probability a building population under seismic events will be sustainable is timely, useful in appropriately allocating earthquake mitigation funds earmarked for repair, rehabilitation, and replacement. A building population is considered sustainable if actual cost incurred is less than a target cost at a given ground motion intensity level such as a certain level of spectral accelerations. The purpose of this study is to construct a mathematical framework coupled with Gompertz and power functions to determine the probability of sustainability of building population subjected to seismic events as a function of target repair-cost ratios. The framework accounts for the exceedence probability of certain earthquake occurrence in 50 years and the fragility data created by joint response surface metamodels (RSMs) and Monte Carlo Simulation (MCS). The fragility data for a population of L-shaped Steel Moment-Frame (LSMF) buildings located in the Central United States and the probability of spectral acceleration exceedence for the target region are used for this study. The probability of sustainability of the LSMF buildings built from pre-1970, between 1970 and 1990, and post-1990 are determined through the developed framework. The mathematical and graphical relationship between the probability of sustainability of the building population under a broad range of spectral accelerations and its target repair-cost ratio are determined. Key findings show that the buildings built in the post-1990 are more sustainable than those built from the pre-1970.

Key Words
mathematical functions; repair-cost ratio; response surface metamodels; seismic fragility curve; steel moment-frame building population; sustainability assessment

Junwon Seo: Department of Civil and Environmental Engineering, South Dakota State University, Brookings, SD 57007, United States
Alan J. Hatlestad: University of Wyoming, Laramie, WY, 82071, United States
Jung-Han Kimn: Department of Mathematics and Statistics, South Dakota State University, Brookings, SD 57007, United States
Jong Wan Hu: Department of Civil and Environmental Engineering, Incheon National University, Incheon, 22012, Republic of Korea;
Incheon Disaster Prevention Research Center, Incheon National University, Incheon, 22012, Republic of Korea

In this investigation, a novel analytical model based on combined (cubic, sinusoidal and exponential) higher order quasi-3D formulation is developed to examine flexural and free vibrational response on the various FG-plate resting on elastic foundation. The presented model is simple and contains a variable number less than others quasi-three dimensional theories. The effective properties of the structure are computed using linear, cubic, quadratic and inverse quadratic formulations which represent the volume fraction of the ceramic. The elastic foundation is structured by the constant parameter of Winkler which represents the reaction of the elastic springs and Pasternak one's in the form of a shear layer of subgrade. The analytical solution of the problem is obtained on the basis of the both Hamilton's principle and Navier's technique. The exactness of the current combined quasi-3D HSDT which takes into account the thickness stretching effect are checked and compared with others existing analytical models. Parametric studies are performed to shows the effects of the material distribution, inhomogeneity index, elastic foundation parameters, geometry and dimension ratios on displacements, stresses and naturel frequencies of the simply supported FG-plates.

Key Words
flexural analysis; functionally graded plate; Quasi 3D HSDT; vibrational analysis

Khadidja Bouafia, Mohamed Bourada, Abdeldjebbar Tounsi and E.A. Adda Bedia: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department,
University of Sidi Bel Abbes, Algeria
Mahmoud M. Selim: Department of Mathematics, Al-Aflaj College of Science and Humanities, Prince Sattam bin Abdulaziz University,
Al-Aflaj 710-11912 Saudi Arabia
Fouad Bourada: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department,
University of Sidi Bel Abbes, Algeria;
Département des Sciences et de la Technologie, université de Tissemsilt, BP 38004 Ben Hamouda, Algérie
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department,
University of Sidi Bel Abbes, Algeria;
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia;
Interdisciplinary Research Center for Construction and Building Materials, KFUPM, Dhahran, Saudi Arabia

This paper presents a computational finite element model to study and analyze vibrations and stresses of regularly perforated rotated beams considering different perforation configurations, for the first time. Both regular circular and squared perforation configurations are considered. The geometry of the perforated beam is modelled using shell finite elements. The finite elements equations of motion are derived for a straight perforated cantilevered beam with a symmetrical cross section. The proposed computational procedure is checked by comparing the obtained results with the available results in the literature and an excellent agreement is observed. The free vibration response, as well as stress distributions throughout the beam, are investigated. The obtained results reveal that the perforation configuration, as well as the rotating speed, have remarkable effects on the dynamics and stress distributions of the rotating perforated beams.

Key Words
finite element method; perforation configurations; perforated rotating beams; stress distribution; vibration behavior

M.A. Eltaher: Department of Mechanical Engineering, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia;
Department of Mechanical Design & Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Hanaa E. Abdelmoteleb: Department of Structural Engineering, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Ahmed Amin Daikh: Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des
Sciences et de la Technologie, Université Mustapha Stambouli B.P. 305, R.P. 29000 Mascara, Algérie
Alaa. A. Abdelrahman: Department of Mechanical Design & Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

This paper presents a dynamic analysis of a prestressed stiffened circular cylindrical shell subjected to external distributed pressure using the dynamic stiffness method. This approach is based on the first order shear deformation theory founded on love's first approximation theory. Natural frequencies are easily processed. The dynamic stiffness matrix has been built. The formulation of this element requires coupling pre-stressed shell and circumferential stiffener. The vibration analysis is performed with numerical examples to determine the performance of this model and the effect of presetress and stiffener on the frequency spectrum. The response of the system is determined with applied equivalent loads on element boundaries. Compared to the finite element method, the proposed element has many advantages such as the model size, the computing time, the accuracy and the higher precision.

Key Words
circumferential stiffener; dynamic stiffness matrix; prestressed; the vibration analysis

Imene Harbaoui: Laboratory of Applied Mechanics and Engineering LR-MAI, University Tunis El Manar- -ENIT BP37- Le belvédère, 1002, Tunis
Mohamed Amine Khadimallah: Prince Sattam Bin Abdulaziz University, College of Engineering, Al-Kharj, Saudi Arabia;Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Abdelhakim Benslimane: Laboratoire de Mécanique Matériaux et Énergétique (L2ME), Faculté de Technologie, Université de Bejaia, 06000 Bejaia, Algeria
Guoyong Jin: College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, PR China
Omer Civalek: China Medial University, Taichung-Taiwan

The aim of this study is to present a new and suitable connection for I-shaped beams and box columns that is both constructionally convenient to implement and reliable in terms of its performance. Six full-scale experimental samples were constructed and subjected to cyclic Quasi-static loading. The first sample included an I-shaped beam which was directly connected to a box column, the second sample incorporated a channel link, and stiffened channel links were used in the remaining four samples. The results show that compared to the direct connection, using the stiffened channel link significantly improves the performance of the connection and increases its ultimate strength and ductility by 58% and 70%, respectively. Also, these connections satisfy the code-specified criteria for special moment resisting frames. They are therefore a suitable detail for rigid I-shaped-beam-to-box-column connections in seismically active regions.

Key Words
cyclic loading; full-scale test; rigid I-shaped beam-to-box column connection; special steel moment resisting frame; stiffened channel link

Allah Reza Moradi Garoosi: Department of Civil Engineering, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Mehrzad Tahamouli Roudsari, Morteza Torkaman,
Shahab Bonyadirad, Ali Saeedmanesh, Khalil soleimani,
Hosein Reza Lotfi, Roya Jowkar and Ali Alipour: Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

This paper presents a series of eight fire tests conducted on circular tubed steel-reinforced concrete columns subjected to eccentric loads. The cross-sectional temperature, axial displacements, fire resistance, and failure modes were recorded and discussed. The influence of key parameters-load ratio, load eccentricity, and wall thickness of the steel tube—on the deformation and fire resistance of the circular tubed steel-reinforced concrete columns were also investigated. Subsequently, the coupled thermal–stress model was developed using the ABAQUS program to investigate the effects of key parameters on both thermal distribution and fire resistance. For the thermal analysis, the considered parameters comprised the cross-section dimensions, the thickness of the steel tube, and types of concrete, and for the fire resistance analysis, they were the load ratio, load eccentricity, thickness of the steel tube, and concrete and H steel strengths. The results showed that the cross-section dimensions have a relatively larger influence than the thickness of the steel tube and the types of concrete on the temperature distribution of the columns. Regarding the fire resistance of the columns, the effects of the load ratio and thickness of the steel tube are remarkable, whereas the concrete and H steel strengths and the load eccentricity have a minor influence. The calculation methods were simplified to determine the steel temperature of a column in a fire, and the N–M curves of the eccentric members subjected to ISO 834 standard temperature are presented. Using the simplified methods, the steel temperature, and the N–M curves of the eccentric circular tubed steel-reinforced concrete columns can be evaluated for any value of the significant parameters, such as the thickness of the steel tube, load ratio, and concrete strength.

Key Words
circular tubed steel-reinforced concrete columns; experimental study; fire resistance; simplified method

Jiepeng Liu and Weiyong Wang: School of Civil Engineering, Chongqing University, Chongqing 400045, China;
Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University),
Ministry of Education, Chongqing 400045, China
Yonghui Xing and Keyan Song: School of Civil Engineering, Chongqing University, Chongqing 400045, China

A new type of composite shear wall with concrete-filled steel tubular frames, column-form reinforcement, and diagonal bars (CFST-CFR-DBSW) was proposed to develop high-efficiency lateral force resistance components for high-rise buildings. In order to study the seismic performance of the new shear wall, four specimens were designed: the new shear wall (CFST-CFR-DBSW), a shear wall with column-form reinforcement and diagonal bars (CFR-DBSW), an ordinary reinforced concrete shear wall (RCSW), and an ordinary reinforced concrete shear wall with concrete-filled steel tubular frames (CFST-RCSW). These specimens were constructed, and then tested under low-cycle loading. Using the experimental results, the anti-seismic behavior indexes of the four specimens were analyzed, including failure mode, bearing capacity, ductility, energy dissipation, stiffness degradation, and damage. A finite-element model of the new shear wall was established with ABAQUS to investigate the influence of the thickness of the steel tube, concrete strength, diameter of the column-reinforcement, and diameter of the diagonal bars on the seismic performance of the shear wall specimen. The research results showed that, compared with other specimens, CFST-CFR-DBSW was significantly strengthened with respect to bearing capacity, deformation, energy dissipation, stiffness, and damage. In addition, the results calculated by the ABAQUS finite-element model was in good agreement with the experimental results, and the influence rules of relevant parameters on the seismic performance of CFST-CFR-DBSW were obtained.

Key Words
column-form reinforcement; concrete-filled steel tubular frames; damage model; diagonal bars; finite-element analysis; seismic behavior

Hao Su: School of Civil Engineering, Xi'an University of Architecture and Technology, No.13, Yanta Road, Xi'an, Shaanxi, China
Hao Su and Lihua Zhu: School of Civil Engineering, Xi'an University of Architecture and Technology, No.13, Yanta Road, Xi'an, Shaanxi, China;
Key Lab of Structural Engineering and Earthquake Resistance, Ministry of Education (Xi'an University of Architecture and Technology), No.13, Yanta Road, Xi'an, Shaanxi, China
Yaohong Wang: School of Civil Engineering, Inner Mongolia University of Technology, No.49, Aimin Street, Hohhot, Inner Mongolia, China

Many studies have proved that structural fuses could improve the seismic performance of structures efficiently. A structural fuse named the miniature bar-typed structural fuse (MBSF) has been proposed and investigated by the authors, which consists of a central core bar, a confining tube. To further improve the mechanic performances of the MBSFs under compressive loadings, Teflon pads are introduced to adjust the contact and friction status between the core bar and the confining tube. Three groups of specimens were discussed including the specimen with a single cutting line (SC), the specimen with double cutting lines (DC), and the specimen with triple cutting lines (TC). The results show that the hysteretic performances of the fuses are improved with the help of Teflon pads. The compression strength adjustment factor declines when Teflon pads are appended. Numerical and theoretical analyses are also conducted which expounded the effect of the Teflon pads. Different plastic buckling deformation principles of the core bars are compared by the theoretical analysis. It is shown that Shanley's theory fits the numerical results well, which is recommended for the theoretical calculation of the proposed MBSFs.

Key Words
cyclic loading; frictional effect; structural fuse; steel; Teflon pads

Sen Yang and Wenguang Liu: School of Civil Engineering, Shanghai University, Shanghai 200444, People's Republic of China
Yan Liu and Hanbin Ge: Department of Civil Engineering, Meijo University, Nagoya 468-8502, Japan
Yu Lin: College of Civil Engineering, Nanjing Forestry University, Nanjing 210037, Jiangsu Province, People's Republic of China
Zhengxing Guo: School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu Province, People's Republic of China

In this study, the active control and vibration analysis of a micro sandwich beam based on modified couple stress theory (MCST) are investigated. The core of sandwich structure is porous and the face sheets are made from piezoelectric material and reinforced by carbon nanotubes. The generalized rule of mixture is employed to predict the mechanical and electrical properties of a micro sandwich composite beam. Based on Hamilton's principle, the governing equations of motion for a micro Reddy beam are derived and active control is considered by the state space representation of the system. The results of this research show that the porosity coefficient, porosity distributions, carbon nanotubes (CNTs) volume fraction, CNTs distributions, the material length scale parameter and different face sheet and core thicknesses effect on the natural frequencies, the resonance phenomenon, settling time and deflection response of system. This research can provide a valuable background for further experimental studies as a basic investigation for applications of a micro sandwich beams in the field of micro robots. Also the results are potentially useful for active control, preventing the resonance phenomenon, design and optimization of micro sandwich beams.

Key Words
active control; micro structures; nanocomposite; piezoelectric; smart materials; vibration

S.M. Akhavan Alavi and M. Mohammadimehr: Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, P.O. Box: 87317-53153, Kashan, Iran
S.H. Ejtahed: Department of Control, Faculty of Computer and Electrical Engineering, University of Kashan, P.O. Box: 87317-53153, Kashan, Iran

In this study, single-step branched polyethyleneimine (PEI)-assisted exfoliation of molybdenum sulfide nanosheets (MoS2-PEI) was carried out. These functionalized MoS2-PEI nanosheets were employed as toughening agents for epoxy composites. The loadings of nanosheets were kept lower than 1 wt.%. The mechanical and thermal properties, and interfacial interactions of epoxy composites were investigated. The epoxy composites have shown ~67% and ~101% enhancements in fracture toughness (KIC) in fracture energy (GIC), respectively, at nanosheets loadings as small as 0.09 wt.% (EP/MoS2-PEI-0.09), KIC has shown a direct linear relationship with the surface free energy and is highest at 52 mJ.m−2 for the EP/MoS2-PEI-0.09 composite. However, the surface free energy values of EP/MoS2-PEI-0.16 and EP/MoS2-PEI-1 composites decreased to 48 mJ.m-2 and 45 mJ.m−2. The overall flexural modulus (E) and strength (O) were not highly responsive to the addition of the MoS2-PEI nanosheets. Furthermore, the thermal stability and thermomechanical properties of the epoxy composites improved significantly. The optimum MoS2-PEI nanosheet loading was observed to be 0.09 wt.%, beyond this a gradual decrease in thermal stability and mechanical properties was observed. The significant improvement in thermal and mechanical properties of the epoxy composites could be accredited to the good interfacial interaction between the MoS2-PEI nanosheets and epoxy matrix at the interface and the inherent strength, high aspect ratio, and excellent barrier effect of PEI molecules.

Key Words
fracture toughness; polymer matrix composites; surface free energy; thermomechanical properties

Shahina Riaz and Soo-Jin Park: Department of Chemistry, Inha University, 100 Inharo, Incheon 22212, Korea
Kyong Y. Rhee: Department of Mechanical Engineering, College of Engineering, Kyung Hee University, Yongin, 17104, South Korea

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