Abstract
A component-based method for the estimation of the posttensioned (PT) steel frame against progressive collapse is proposed and presented in the current paper. A mechanical model of PT steel connections is developed and benchmarked with experimental data of a PT beam-column substructure from literature. The developd mechanical models of four PT connections are able to capture the initial elastic stiffness, decompression load, and residual stiffness under lateral loading. Then, analysis of a reduced-scale three-storey two-bay PT steel frame is carried out with sufficient accuracy by incorporating the proposed joint model into the frame analysis. The proposed method is then applied to assessing progressive collapse of a one-storey two-bay PT frame under middle column removal scenario, and is verified against existing experimental and ANSYS finite element results. Three resistance mechanism for progressive collapse of the PT frame are evaluated, which consists of angle flexural mechanism, beam compression arching action and strand tensile catenary action. Finally, parameter analyses of the PT frames are conducted to investigate the effects of the connection details on the behavior and resistance of progressive collapse. The proposed model can be used to predict the quasi-static behavior of PT frames under monotonic vertical loading conditions with satisfactory accuracy.
Address
Yan Fei Zhu,Ying Huang and Zhaohui Huang: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
Chang Hong Chen: School of Mechanics and Civil Engineering, Northwestern Polytechnical University, Xi'an, 710129, China
Yao Yao: School of Civil Engineering, Xi;an University of Architecture and Technology, Xi'an, 710055, China;
School of Mechanics and Civil Engineering, Northwestern Polytechnical University, Xi'an, 710129, China
Leon M. Keer: Civil and Environmental Engineering, Northwestern University, Evanston, IL, 60286, USA
Abstract
In this research, the seismic performance of a steel column damper is evaluated using cyclic loading tests of two one-story one-bay reinforced concrete (RC) frames before and after retrofit. The theoretical formulation and design procedure of the damper are explained first and then the details of the tests are described. The seismic performances of the test frames are evaluated in terms of hysteretic behavior, energy dissipation, crack pattern, failure mechanism, and damper behavior. The analytical model of the damper is established and verified using the experimental data. In order to further investigate the applicability of the developed damper for seismic retrofit, a case-study structure is chosen and retrofitted using the proposed damper. The seismic performance of the structure is evaluated and compared before and after retrofit in detail using pushover, nonlinear time-history, and fragility analyses. The results show that the presented damper can efficiently reduce inter-story drifts and damage of the structure. The details of modeling techniques and simulations given in this study can provide guidelines and insight into nonlinear analysis and retrofit of RC structures.
Key Words
fragility analysis; energy dissipation devices; hysteretic dampers; seismic performance; seismic retrofit; pushover analysis
Address
Mohammad Mahdi Javidan, Seungho Chun and Jinkoo Kim: Department of Civil & Architectural Engineering, Sungkyunkwan University, Suwon, Republic of Korea
Abstract
In this paper, mathematical bioheat transfer model in skin tissues in the bounded domain due to moving heat source are considered. The thermal damage to the tissues is totally evaluated by the denatured protein ranges by the Arrhenius formulation. The temporal complete solutions in Laplace time domain obtained by using the inversion scheme of the Laplace transform, to obtain the general solution (exact solution) for the increment of temperature. The numerical result of temperature and the thermal injurie are graphically demonstrated. In conclusions, parametric analysis are devoted to the identifications of appropriates procedures for choosing serious designs variables to reach the effectives thermal in hyperthermias treatments.
Key Words
bioheat transfer without energy dissipations; laplace transforms; skin tissues; thermal damages
Address
Aatef D. Hobiny: Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Mathematics Department,
King Abdulaziz University, Jeddah, Saudi Arabia
Ibrahim A. Abbas: Nonlinear Analysis and Applied Mathematics Research Group (NAAM), Mathematics Department,
King Abdulaziz University, Jeddah, Saudi Arabia;
Department of Mathematics, Faculty of Science, Sohag University, Sohag, Egypt
Abstract
The major sources of damping in steel structures are within the joints and the structural material. For welded large-scale single-layer lattice domes subjected to earthquake ground motions, the stick-slip phenomenon at the bearings is an important source of the energy dissipation. However, it has not been extensively investigated. In this study, the equivalent friction damping ratio (EFDR) at the bearings of a welded large-scale single-layer lattice dome subjected to earthquake ground motions is quantified using an approximate method based on the energy balance concept. The complex friction behavior and energy dissipation between contact surfaces are investigated by employing an equivalent modeling method. The proposed method uses the stick-slip-hook components with a pair of circular isotropic friction surfaces having a variable friction coefficient to model the energy loss at the bearings, and the effect of the normal force on the friction force is also considered. The results show that the EFDR is amplitude-dependent and is related to the intensity of the ground motions; it exhibits complex characteristics that cannot be described by the conventional models for damping ratios. A parametric analysis is performed to investigate in detail the effects of important factors on the EFDR. Finally, the friction damping mechanism at bearings is discussed. This study enables researchers and engineers to have a better understanding of the essential characteristics of friction damping under earthquake ground motions.
Address
Huidong Zhang and Shu Yao: School of Civil Engineering, Tianjin Chengjian University, Tianjin 300384, China;
Tianjin Key Laboratory of Civil Buildings Protection and Reinforcement, Tianjin 300384, China
Xinqun Zhu: School of Civil and Environmental Engineering, University of Technology Sydney, NSW 2007, Australia
Yuanfeng Wang: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
Abstract
This paper study the seismic performance of modular prefabricated SRC column to steel beam composite joint (MPCJ) under static loading. Numerical modeling of MPCJs with three different beam-end connections was carried out in ABAQUS. Results of the numerical calculation were compared with existing quasi-static test results to verify the feasibility of the numerical model. The model was then used to analyze changes in the moment-rotation relation, failure mode, ductility, stiffness, and bolt stress in the joint between the column and joint module. Besides, stress distributions in the joints were analyzed along different stress paths. Under monotonic loading, the mechanical performance of the MPCJ is significantly affected by the beam end connection mode. Failure of the MPCJ mainly occurs at the beam end connection, thus, the aim of keeping the plastic hinge away from the joint core and preventing shear failure is achieved. Furthermore, the maximum story drift ratio is 3.9–5 times greater than the recommended limit, which indicates good ductility and deformation performance. The MPCJ of the three-beam end connection methods is all semi-rigid connections. The beam end structure will have a large influence on the bolt tension and stress distribution. According to the test research results, a nonlinear model with three parameters including joint cover plate cantilever section length, flange connecting plate thickness and flange connecting plate weld length was established. The theoretical calculation results was consistent with the results of the numerical simulation. MPCJs can be designed based on the proposed theoretical calculation formula.
Key Words
composite joints; finite element analysis; hysteric curves; mechanical properties; prefabricated; seismic loads
Address
Wu Cheng Long, Kan Jian Cheng, Liu Ji Ming and Mou Ben: Department of Civil Engineering, Qingdao University of Technology, Qingdao, Shandong 266033, China
Abstract
In this study, an analytical method is presented to investigate the nonlinear buckling analysis of functionally graded porous (FGP) shallow spherical shells exposed to external excitation in a thermal environment resting on elastic foundations. The elastic foundations of the FGP shell are consist of a two-term Winkler-Pasternak's model. Using the classical theory of shells and considering nonlinear von Karman-Donnell relations and Hook law, the governing equations of thin FG porous spherical shells are extracted. Galerkin's method is utilized to discretize the governing equation of shallow spherical shell. Regarding the discretized equations of motion, the explicit expressions for dynamic and static critical buckling loading are determined under thermomechanical effect. Two types of distributions for FG porous, including the uniform and symmetric porosity, are considered. To investigate the dynamic buckling exposed to external pressure and thermal effect, the equations of motion of FGP shallow spherical shells are examined via a numerical method named Runge-Kutta approach, and then with a procedure presented by Budiansky-Roth, the critical load for the nonlinear dynamic buckling is obtained. The influence of thermal environment changes, porosity coefficients, various porosity distributions, elastic foundations, and geometrical characteristics on the nonlinear static and dynamic buckling response of FGP shallow spherical shell is examined.
Key Words
elastic foundations; FG porous material; nonlinear static and dynamic buckling; shallow spherical shell; thermal environment
Address
Habib Ahmadi and Kamran Foroutan: Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
Abstract
This paper have the objective of investigating forced vibration behaviour of axially functionally graded cylindrical helices with variable cross-section. An algorithm is developed in order to solve corresponding problems. The ordinary differential equations governing the dynamic behaviour of cylindrical helices are determined in Laplace domain by using Timoshenko beam theory. Then transfer matrix method is implemented for the solution, including shear and axial deformation effects. Obtained results are transferred to time domain using Durbin's modified numerical inverse algorithm for Laplace transform. A benchmark problem has been solved to check the accuracy of developed algorithm then a parametric study is conducted considering the effects of material gradient index (b_mat), section variation parameter (b-sec) and number of active turns (n). Results are compared with solutions attained from ANSYS for verification.
Abstract
The purpose of this research is to identify more efficient and reliable connection methods to design a composite steel/concrete structural system with a focus on sustainability. While using innovative blind bolt shear connectors into substitute for the welded stud brings several benefits regarding constructability and sustainability, research contributions on the high strength blind bolt shear connector are very limited. Therefore, in this study, several push-out test specimens were carried out, in accordance with the Eurocode 4 standards, for both the traditional welded stud and the blind bolt shear connector, to determine the ultimate capacity, ductility, stiffness, stress-strain and load versus slip performance. In addition, finite element analysis has been done on the two types of shear connectors to determine the factors influencing static strength of shear connectors. The feasibility and accuracy of the 3-D finite element model developed in this work was validated by comparing with experimental results obtained from push-out tests. Experimental and finite element modelling results revealed that the blind bolt shear connectors would be an appropriate alternative to the traditional welded stud for sustainable purposes under static loading conditions.
Key Words
bolted shear connector; composite beam; finite element model; headed studs; push out tests
Address
Seyedeh Maryam Hosseini, Fidelis Mashiri, Olivia Mirza and Brendan Hart: School of Engineering, Second Ave, Kingswood NSW 2747, Western Sydney University, Sydney, Australia
Abstract
In this article bending response of multi-phase nanocomposite (MPC) filled by circular plates (MPCCP) in the
framework of the three-dimensional elasticity model under bi-directional initially stressed (BDIS) resting on non-polynomial elastic foundation for a broad range of boundary conditions is presented. The discrete singular convolution (SS-DSC) based on state-space is provided to evaluate the bending characteristics of MPCCP by considering various boundary conditions. Halpin–Tsai model and micro-scaled fibers have been applied in the hierarchy to anticipate the properties of bulk material of the multiscaled
composites. In order to model a disk, singular point has been analyzed. The graphene platelets (GPLs) are assumed to be oriented in random directions and distributed in uniform pattern in the epoxy resin matrix. Then, to provide the influences of primary stressed, elastic substrate and a range of pressure types on the bending behavior of the MPCCP, a parametric analysis has been conducted. Computational outcomes disclose that sinusoidal load is the best pressure for improving the deformation resistances and stress of the nanocomposite circular/annular plates.
Key Words
BDIS; bending; 3D-elasticity theory; MPCCP; singular point; SS-DSC
Address
Feng Shao: College of Architecture and Urban Planning, Qingdao University of Technology, Qingdao 266033, Shandong, China
Yanshang Wang: Qingdao Fire Rescue Detachment, Qingdao 266000, Shandong, China
Abdel Kareem Alzo'ubi: A.K. Alzo'ubi, Civil Engineering Department, Abu Dhabi University, UAE
Mamdooh Alwetaishi: Department of Civil Engineering, College of Engineering, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia
Mohamed Amine Khadimallah: Prince Sattam bin Abdulaziz University, College of Engineering, Department of Civil Engineering, Alkharj, 16273, Saudi Arabia;
Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Abstract
Variable stiffness composite plate can adjust the stiffness properties of the plate in order to satisfy the design requirements of studied problem. In this paper, the effects of different types of boundary conditions, lay-ups, sizes and shapes of geometric initial imperfection on the nonlinear behavior of VAT plates are investigated; these conditions influence the behavior of the plate completely. Moreover, the first-order shear deformation plate theory and Von-Karman assumptions are applied to analyze the effects of fiber lay-up sequences of VAT-laminate under different boundary conditions. Ritz method is also exploited by using Legendre polynomials to approximate the unknown displacement fields of the problem. To yield more accurate results, potential energy integrals are numerically calculated by employing Gauss-Lobatto formulas. Lastly, the system of nonlinear equations is solved by the well-known Newton-Raphson technique. In order to validate the results, finite element analysis is also implemented by the commercial finite element package ABAQUS.
Key Words
composite plates; FSDT; imperfection; nonlinear response; post-buckling; Ritz method; variable angle tow
Address
S. Amir M. Ghannadpour and Fatemeh Rashidi: Faculty of New Technologies Engineering, Shahid Beheshti University, Tehran, Iran
