Abstract
This study focused on the effectiveness of seismic isolation technique in case of a reinforced concrete structure with soft story defined as the stiffness irregularity between adjacent stories. In this context, a seismically isolated 3-story reinforced concrete structure was analyzed by gradually increasing the first story height (3.0, 4.5, and 6.0 m). The seismic isolation system of the structure is assumed to be composed of lead rubber bearings (LRB). In the analyses, isolators were modeled by both deteriorating (temperature-dependent analyses) and non-deteriorating (bounding analyses) hysteretic representations. The deterioration in strength of isolator is due to temperature rise in the lead core during cyclic motion. The ground motion pairs used in bi-directional nonlinear dynamic analyses were selected and scaled according to codified procedures. In the analyses, different isolation periods (Tiso) and characteristic strength to weight ratios (Q/W) were considered in order to determine the sensitivity of structural response to the isolator properties. Response quantities under consideration are floor accelerations, and interstory drift ratios. Analyses results are compared for both hysteretic representations of LRBs. Results are also used to assess the significance of the ratio between the horizontal stiffnesses of soft story and isolation system. It is revealed that seismic isolation is a viable method to reduce structural damage in structures with soft story.
Key Words
lead rubber bearing; nonlinear response history analysis; reinforced concrete structure; seismic isolation; soft story
Address
Hakan Öztürk: Department of Civil Engineering, Engineering Faculty, Sakarya University, 54050 Sakarya, Turkey
Esengül Çavdar, Gökhan Özdemir: Department of Civil Engineering, ESQUAKE, Seismic Isolator Test Laboratory, Eskisehir Technical University, Iki Eylul Campus,
Eskisehir, Turkey
Abstract
This study conducts numerical analyses of a thin-walled composite cylinder under axial compression and internal
pressure of 10 kPa. Numerical vibration correlation technique and nonlinear postbuckling analyses are conducted using the nonlinear finite element analysis program, ABAQUS. The single perturbation load approach and measured imperfection data are used to represent the geometric initial imperfection of thin-walled composite cylinder. The buckling knockdown factors are derived using present initial imperfection and analysis methods under axial compression without and with the internal pressure. Furthermore, the buckling knockdown factors are compared with the buckling test and computation time are calculated. In this study, derived buckling knockdown factors in present study have difference within 10% as compared with the buckling test. It is shown that nonlinear postbuckling analysis can derive relatively accurate buckling knockdown factor of present thin-walled cylinders, however, numerical vibration correlation technique derives reasonable buckling knockdown factors compared with buckling test. Therefore, this study shows that numerical vibration correlation technique can also be considered as an effective numerical method with 21~91% reduced computation time than nonlinear postbuckling analysis for the derivation of buckling knockdown factors of present composite cylinders.
Address
Do-Young Kim: Rotorcraft Structural Design Team, Korea Aerospace Industries, Sacheon, 52529, Republic of Korea
Chang-Hoon Sim, Jae-Sang Park: Department of Aerospace Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
Joon-Tae Yoo, Young-Ha Yoon: Launcher Structures and Materials Team, Korea Aerospace Research Institute, Daejeon, 34133, Republic of Korea
Keejoo Lee: Small Launch Vehicle Research Division, Korea Aerospace Research Institute, Daejeon, 34133, Republic of Korea
Abstract
In this study, it is intended to perform nonlinear time-history analyses of nuclear power plant structures (NPP) under near-fault earthquakes showing directivity pulse and fling-step characteristics. Simulation procedures based on cycloidal pulse and far-fault ground motions are also used to simulate near-fault motions showing forward-directivity and fling-step characteristics and the structural responses are compared with those of the recorded near-fault ground motions. Because it is aimed to determine specifically the pulse type characteristics of near-fault ground motions on NPPs, all the ground motions are normalized to have a PGA of 0.3 g. Depending on the obtained results it can be underlined that although near-fault ground motion has the potential to cause damage mostly on structural systems having larger periods, it may also have noticeable effects on the responses of rigid structures, like NPP containment buildings. On the other hand, simulated near-fault motions can help us to get an insight into the near-fault mechanism as well as an approximate visualization of the structural responses under nearfault earthquakes.
Key Words
fling-step characteristics; forward-directivity characteristics; near-fault ground motion simulation; near-fault ground motion; nuclear power plant containment building
Address
Kurtulus Soyluk: Department of Civil Engineering, Faculty of Engineering, Gazi University, Maltepe, Ankara, Turkey
Hamid Sadegh-Azar: Institute of Structural Analysis and Dynamics, Department of Civil Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany
Dersu Yilmaz: Pohlcon GmbH, 12057 Berlin, Germany
Abstract
Recently, the use of smartphones for structural health monitoring in civil engineering has drawn increasing attention due to their rapid development and popularization. In this study, the structural responses and dynamic characteristics of a 421-mtall skyscraper during the landfall of Typhoon Muifa are monitored using an iPhone 13. The measured building acceleration responses are first corrected by the resampling technique since the sampling rate of smartphone-based measurement is unstable. Then, based on the corrected building acceleration, the wind-induced responses (i.e., along-wind and across-wind responses) are investigated and the serviceability performance of the skyscraper is assessed. Next, the amplitude-dependency and time-varying structural dynamic characteristics of the monitored supertall building during Typhoon Muifa are investigated by employing the random decrement technique and Bayesian spectral density approach. Moreover, the estimated results during Muifa are further compared with those of previous studies on the monitored building to discuss its long-term time-varying structural dynamic characteristics. The paper aims to demonstrate the applicability and effectiveness of smartphones for structural health monitoring of high-rise buildings.
Key Words
smartphone; structural dynamic characteristics; structural health monitoring; super-tall buildings; typhoon
Address
Kang Zhou: College of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Anhui Civil Engineering Structures and Materials Laboratory, Hefei 230009, China
Sha Bao: Shanghai Branch, China Construction Eighth Engineering Division Co., Ltd., Shanghai 200001, China
Lun-Hai Zhi: College of Civil Engineering, Hefei University of Technology, Hefei 230009, China; Anhui Civil Engineering Structures and Materials Laboratory, Hefei 230009, China
Feng Hu: College of Civil Engineering, Hefei University of Technology, Hefei 230009, China
Kang Xu, Zhen-Ru Shu: School of Civil Engineering, Central South University, Changsha 410083, China
Abstract
This study aims to solve for nonlinear cylindrical shell systems with a semi-analytical and numerical approach implementing the P-T method. The procedures and conditions for such a study are presented in practically solving and analyzing the cylindrical shell systems. An analytical model for a nonlinear thick cylindrical shell (TCS) is established on the basis of the stress function and Reddy's higher-order shear deformation theory (HSDT). According to Reddy's HSDT, Hooke's law in three dimensions, and the von-Kármán equation, the stress-strain relations are developed for the thick cylindrical shell systems, and the three coupled nonlinear governing equations are thus established and discretized as per the Galerkin method, for implementing the P-T method. The solution generated with the approach is continuous everywhere in the entire time domain considered. The approach proposed can also be used to numerically solve and analyze the nonlinear shell systems. The procedures and recurrence relations for numerical solutions of shell systems are presented. To demonstrate the application of the approach in numerically solving for nonlinear cylindrical shell systems, a specific nonlinear cylindrical shell system subjected to an external excitation is solved numerically. In numerically solving for the system, the present approach shows higher efficiency, accuracy, and reliability in comparison with that of the Runge-Kutta method. The approach with the P-T method presented is practically sound especially when continuous and high-quality numerical solutions for the shell systems are considered.
Key Words
3D nonlinear vibration; cylindrical shells; P-T method; Reddy's HSDT; reliability and accuracy; Runge-Kutta method
Address
Liming Dai and Kamran Foroutan: Sino-Canada Research Centre of Computation and Mathematics, Qinghai Normal University and the University of Regina, Qinghai Normal University, China; Industrial Systems Engineering, University of Regina, Regina, SK, S4S 0A2, Canada
Abstract
The present study deals with wave propagation in a modified couple-stress generalized thermoelastic solid under the
effect of gravity and magnetic field. The problem is solved by a refined microtemperatures multi-phase-lags thermoelastic theory. The Fourier series and Laplace transforms will be used to obtain the general solution for any set of boundary conditions. Some comparisons have been shown in figures to estimate the effects of the gravity field, the magnetic field, and different theories of thermoelasticity in the presence of the hall current effect on all the physical quantities. Some particular cases of
special interest have been deduced from the present investigation.
Key Words
hall current; microtemperatures; modified couple stress; multi-phase-lags theory; thermoelastic
Address
Samia M. Said: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Elsayed M. Abd-Elaziz: Ministry of Higher Education, Zagazig Higher Institute of Engineering and Technology, Zagazig, Egypt
Mohamed I.A. Othman: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Abstract
Unreinforced masonry (URM) buildings are extensively adopted in many of the growing nations, particularly in India. Window or door openings are required for architectural or functional reasons, which pose a threat to the building's safety. The past earthquakes have shown that the seismic capability of these structures was very weak. Strengthening these unreinforced masonry walls using welded wire mesh (WWM) is one of the most commonly and economical methods. The present experimental study investigates the impact of openings on the shear behaviour of URM walls and the effectiveness of WWM in enhancing the shear performance of masonry wall. In the experimental program 16 specimens were cast, 8 unstrengthen and 8 strengthened specimens, under 8 unstrengthen and strengthened specimens, every 2 specimens had 0%, 5%, 10%, and 15% openings and all these walls were tested under diagonal compression. The results show that the shear carrying capacity reduces as the opening percentage increases. However, strengthening the URM specimens using WWM significantly improves the peak load, shear strength, ductility, stiffness, and energy dissipation. Furthermore, the strengthening of the URM walls using WWM compensated the loss of wall capacity caused by the presence of the openings.
Address
Wanraplang Warlarpih and Comingstarful Marthong: Department of Civil Engineering, National Institute of Technology Meghalaya, Shillong 793003, India
Abstract
To defend against harmful gamma radiation, new types of materials for use in the construction of heavyweight
concrete (HWC) are still needed to be developed. This research introduces new materials to be employed as a partial replacement for fine aggregate (FA) to manufacture high-performance heavyweight concrete (HPHWC). These materials include hematite, black sand, ilmenite, and magnetite, with substitution ratios of 50% and 100% of FA. In this research, the hardening and fresh characteristics of HPHWC were obtained. Concrete samples' Gamma-ray linear attenuation coefficient was evaluated utilizing a gamma source of Co-60 through the thicknesses of 2.5, 5, 7.5, 10, 12.5, and 15 cm. High temperatures were studied for HPHWC samples, which were exposed to up to 700oC for two hours. Energy-dispersive x-rays and a scanning electron microscope carried out microstructure analyses. Magnetite as an FA attained the lowest compressive strength of 87.1 MPa, but the best radiation protection characteristics and the highest density of 3100 kg/m3 were achieved. After 28 days, the attenuation efficiency of concrete mixtures was increased by 6.5% when fine sand was replaced with black sand at a ratio of 50%. HPHWC, which contains hematite, black sand, ilmenite, and magnetite, is designed to reduce environmental and health dangers and be used in medicinal, military, and civil applications.
Key Words
black sand; hematite; high temperatures; ilmenite; magnetite; mechanical properties; microstructure; radiation
shielding
Address
Ashraf M. Heniegal: Civil Engineering Department, Faculty of Engineering, Suez University, Egypt
Mohamed Amin: Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt
S.H. Nagib: Ionizing Radiation Met. Lab., National Institute of Standards, Giza, Egypt
Hassan Youssef: Civil Constructions Department, Faculty of Technology and Education, Beni-Suef University, Egypt
Ibrahim Saad Agwa: Civil Engineering Department, Faculty of Engineering, Suez University, Egypt
