Abstract
Retaining walls and cantilever soldier pile walls are both can be used in interchangeable manner so it is so important
to evaluate the relationship between the cost and sizing. In this paper, an investigation of the effect of the design restraints and cost limits of both reinforced concrete retaining walls and cantilever soldier pile walls on optimum design is done. Pure frictional soils are evaluated as the surrounding soil medium of retaining structures and Rankine lateral earth pressure theory is used to derive the lateral thrust effected through the selected retaining systems. Fictionalized different cases are created for all retaining systems to compare optimal dimensions and minimum costs for the same project requirements. Jaya algorithm is used to perform optimization process. Parametrical analyses are conducted according to change of excavation depth, unit weight of soil, and cost of concrete, surcharge load and workmanship multiplier. The results of the parametric analysis has provided to suggest on the design and application differences of both retaining systems having regard to the effects of both cost and sizing simultaneously. As a consequence of the study, some limitations that have to be considered before design are given for the selection of proper retaining structure not to cause overinvestment.
Abstract
The use of displacement-dependent steel curved dampers as fuse or interchangeable element in the beam-to-column connection region is one of the newest methods for improving the seismic performance of semi-rigid moment steel frames (SRMF). In the present study, performance of low-yield strength curved dampers in MRSF has been investigated. These dampers are inactive and install in the beam-to-column connection region. Variable parameters of this study involve the damper width (75, 100 and 125 mm), damper thickness (10, 15, 20, 25 and 30 mm) and the damper steel type (SN400YB and LY160). Evaluation of MRSF models were performed using finite element method by ABAQUS. For validation, a MRSF with curve dampers was modeled that had been experimentally tested and reported in previous experimental research and a good agreement was observed. The results show that the use of low-yield strength steel in curved steel dampers, depending on the damper thickness, can lead to an increase in the hysteresis equivalent damping ratio, ductility parameter and total energy dissipated compared to the steel with higher yield stress.
Key Words
beam-to-column connection; low-yield strength plates; moment resisting steel frames; steel curved dampers
Address
Ali Mohammad Rousta: Department of Civil Engineering, Yasouj University, Yasouj, Iran
Hamid Shojaeifar: Department of Civil Engineering, Faculty of Maragheh, Maragheh Branch, Technical and Vocational University (TUV), Tehran, Iran
Mojtaba Gorji Azandariani: Structural Engineering Division, Faculty of Civil Engineering, Semnan University, Semnan, Iran
Sajad Saberiun: Department of Civil Engineering, Faculty of Hamedan, Hamedan Branch, Technical and Vocational University (TUV), Tehran, Iran
Hamid Abdolmaleki: Department of Civil Engineering, Tuyserkan Branch, Islamic Azad University, Tuyserkan, Iran
Abstract
Load and resistance factor design (LRFD) is a suitable format for the reliability-based limit state design of structures. It has been adopted in many countries, such as the United States, Europe, Canada, and Japan. Usually, the first-order reliability method (FORM) is used to estimate the load and resistance factors, but it requires the determination of design points and complicated double iterative computations. Therefore, FORM is not easy or practical for engineers to use. This paper presents a simple, accurate method to determine the load and resistance factors utilizing the third-moment transformation, which does not require derivative-based iterations and can estimate the load and resistance factors without using the distribution of random variables. In addition, the proposed method provides enough accurate results within a wide range of target reliability indices. Therefore, this method should be effective and convenient for calculating the load and resistance factors in actual practice. Five numerical examples illustrate the proposed method's efficiency and accuracy; FORM provides a benchmark for comparison.
Key Words
FORM; limit state design; LRFD; third-moment transformation
Address
Pei-Pei Li: Department of Architecture, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
Zhao-Hui Lu: Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, No.100 Pingleyuan, Beijing 100124, China; National Engineering Laboratory for High Speed Railway Construction, Central South University, 22 Shaoshannan Road, Changsha 410075, China
Yan-Gang Zhao: Department of Architecture, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
Abstract
A nonlinear gas-spring is integrated into the traditional tuned mass damper (TMD), leading to a novel gas-spring tuned mass damper (GSTMD) system, which can be used to mitigate the structural responses. To better couple the tuned mass damping system, a symmetrical combined gas-spring (SCGS) is presented based on a single gas-spring, and its mechanical properties are investigated through a case study. The design method of the gas-spring TMD is obtained, and its corresponding configuration parameters are calculated. The control performance and damping mechanism of the gas-spring TMD under the random excitation are studied by parameter analysis, and the reliability of the gas-spring TMD's control performance is also discussed. The results show that the gas-spring TMD has a two-stage damping mechanism, and its working stage can change flexibly with the excitation intensity. Furthermore, the gas-spring TMD has excellent "Reconciling Control Performance", which not only has a comparable control performance as the linear TMD, but also has significant advantages in working stroke, more importantly, the control performance and working stroke of the gas-spring TMD can reconcile with each other. Besides, the control performance of the proposed damper is insensitive to unpredictable seismic excitations, indicating that the gas-spring TMD has good reliability.
Key Words
damping mechanism; gas-spring tuned mass damper; nonlinear energy sink; passive control; reliability; working stroke
Address
Kunjie Rong: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China
Zheng Lu: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China
Abstract
Laying ballastless tracks on large-span cable-stayed bridge is a new challenge, and it is particularly important due to the obvious advantages of ballastless track and the high requirements of high-speed railways. Under the complex load conditions in service, cable-stayed bridges have a variety of beam local deformations, and they inevitably affect the performances of the ballastless tracks laid on the bridge. In this work, a series of experimental studies and FEM simulations are carried out based on a large-span cable-stayed bridge and its segmental model. The main conclusions include: Under the most unfavorable reverse bending deformation of the large-span cable-stayed bridge, tensile and compressive deformations occurred at interlayers of the ballastless tracks with different isolation layers. The interlayer deformation variations of the ballastless tracks with EPDM or geotextile isolation layers are the same, and the deformation values of the ballastless tracks with EPDM isolation layers are larger than that of the ballastless tracks with geotextile isolation layers. However, due to the pre-compression of the EPDM isolation layer subjected to its upper structures' deadweight, it can reduce the influences of the reverse bending deformation on the ballastless tracks, and the gaps and voids at ballastless track interlayers can be avoided. Furthermore, the 5.92 m length ballastless tracks with EPDM isolation layer is recommended to apply on the large-span cable-stayed bridge in high-speed railway to ensure the reliability and durability of the ballastless tracks.
Address
Weiqi Zheng: Department of Civil Engineering, Central South University, Changsha, China; National Engineering Laboratory for High Speed Railway Construction, Changsha, China
Xingwang Sheng: Department of Civil Engineering, Central South University, Changsha, China
Zhihui Zhu: Department of Civil Engineering, Central South University, Changsha, China; National Engineering Laboratory for High Speed Railway Construction, Changsha, China
Tao Shi: Department of Civil Engineering, Central South University, Changsha, China
Abstract
Heavyweight geopolymer concrete (HWGC) is a new concrete type that combines the benefits of geopolymer concrete (GC) and heavyweight concrete. HWGC can be used to produce particular properties such as high radiation shielding, and mass concrete elements. HWGC based on fly ash and ground granulated blast furnace slag, using electric arc furnace steel slag (EAFSS), barite and ilmenite coarse aggregates can substantially have higher specific gravities than concrete made with crushed dolomite. In the experimental work carried out on four main groups, 13 GC mixes are prepared by using heavyweight coarse aggregates (HWCAs) at volume ratios of 0%, 25%, 50%, 75% and 100%. Fresh and mechanical properties, compressive and tensile strengths, and influence of high temperature on radiation are investigated for specimens subjected to high temperatures of up to 900oC for 1, 2 and 3 hours. Moreover, the internal structure of geopolymer is analyzed using scanning electron microscope and energy-dispersive X-ray. Results show a good effect of HWCAs on the properties, radiation shielding and unit weight. The density of heavyweight geopolymer mixes ranges between 2,415 and 3,480 kg/m3, and HWCA ratios contribute to an increase in all properties of GC mixtures using up to 75% of NWCAs. Heavier coarse aggregate of ilmenite dampens the effect of higher temperatures on GC strength compared with lighter aggregates. In addition, replacing crushed dolomite with heavyweight aggregates of EAFSS, barite and ilmenite increases the attenuation rate to 27%, 21% and 13%, respectively. This finding confirms that the type of aggregate used in the production of GC is important for reducing the permeability of X-ray.
Key Words
attenuation coefficient; barite; geopolymer concrete; heavyweight aggregates; high temperatures; ilmenite; mechanical properties; microstructure; steel slag
Address
Mohamed Amin: Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt
Abdullah M. Zeyad: Civil Engineering Department, Jazan University, Jazan, Saudi Arabia
Bassam A. Tayeh: Civil Engineering Department, Faculty of Engineering, Islamic University of Gaza, Palestine
Ibrahim Saad Agwa: Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt
Abstract
This paper deals with the secondary vibration problem in the superharmonic case near the harmonic excitation of 1/3w1, arising from the vibration nonlinearity that characterizes the slender and less damping laminated beam with composite material core. For this aim the multiple scale method in conjunction with the higher order zigzag theories are used to obtain the resonance responses. In the present work the nonlinear forced vibration problem of sandwich beams under harmonic excitation is solved by the multiples scales method, based by the introduction of an artificial parameter with higher order expansions, to control the nonlinear analytical solutions. The application of this method demonstrates the sensitivity of the sandwich beams with viscoelastic composite layer to the secondary superharmonic vibrations. Following, parametric study is conducted to demonstrate the vulnerability of the laminated structures to the superharmonic vibrations and to reduce as far as possible the amplitude vibrations achieved by more appropriated structural design. The results reveal the effect of the slenderness of the sandwich beams on the hardening changes. In the other hand the results demonstrate the importance of fibre orientation angle to reduce as far as possible the amplitude responses of the sandwich structures in superharmonic vibration case.
Key Words
composite materials; higher order zig-zag theories; laminated beams; multiple scale method; nonlinear vibration; superharmonic vibrations
Address
Abbache Ali: 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;
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de DjellaliLiabes, Sidi Bel Abbes, Algérie
Hadj Youzera, Moussa Abualnour, Mohammed Sid Ahmed Houari: 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
Sid Ahmed Meftah: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de DjellaliLiabes, Sidi Bel Abbes, Algérie
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Eastern Province, Saudi Arabia
Abstract
Influence lines and internal forces functions are vital tools for designing and monitoring engineering structures. This research explored a static method to derive exact closed-form equations for internal forces functions of bridge-type structures, continuous beams, and bridge frames, considering the bending flexibility. For this aim, first, we achieved member-end moment functions by applying the moment-rotation relationships in conjunction with the rotation propagation method. Then, substituting these functions into the static equilibrium equations provided the desired functions in terms of both the unit load and intended cross-section positions all over the structure, subjected to concentrated loads. Finally, the authors solved three illustrative examples to clarify the dominance of their suggested method for constructing both influence line and internal forces diagrams of statically indeterminate structures.
Abstract
This paper aims to study the fatigue performance of three-tower four-span suspension bridges. For this purpose, the Oujiang River North Estuary Bridge which is a three-tower four-span suspension bridge with two main spans of 800m under construction in China is taken as an example in this study. This will be the first three-tower suspension bridge with steel truss girders in the world. This paper uses a random traffic load model to evaluate the fatigue reliability of the orthotropic steel bridge decks of three-tower four-span suspension bridges. In the study traffic load is simulated by random variables, and Monte Carlo simulation method is used to calculate the fatigue reliability index of the steel bridge deck. The parametric analysis is also carried out to clarify the influence of traffic growth rate, target reliability index and axle lateral distribution coefficient. It is found that the growth of traffic volume has the greatest impact on the evaluation results of the fatigue life, and the growth of traffic volume can result in a decrease of fatigue reliability of orthotropic steel bridge decks. The research results can provide a reference for the fatigue life and reliability assessment of three-tower four-span suspension bridge.
Address
Jin Cheng: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China; Department of Bridge Engineering, Tongji University, Shanghai, China
Cheng Li: Department of Bridge Engineering, Tongji University, Shanghai, China
Abstract
Buckling analysis of porous sandwich nanoplate integrated with two piezoelectric face-sheets is presented based on
shear and normal deformation theory (SNTD). Effect of small scales of the porous core and actuated face-sheets is accounted
based on the nonlocal strain gradient theory (NSGT). Large parametric results are presented to investigate variation of various
critical loads in terms of significant parameters such as porosity volume fraction, strain gradient and nonlocal parameter, and
dimensionless geometric parameters. It is concluded that increase of porosity volume fraction leads to decrease of critical
electric and magnetic potentials and increase of critical temperatures.
Key Words
electro-magneto-thermo-mechanical buckling loads; NSGT; porous core; sandwich nanoplate; shear and
normal deformation theory
Address
Xiaohua Wang: Teaching Affairs Office, Zhejiang Guangsha Vocational and Technical University of Construction,
Dongyang City 322100, Zhejiang Province, P.R. China
Pinyi Wang: Department of Electrical and Computer Engineering, University of Washington Seattle, WA 98195, USA
Wei Jiang: School of Intelligent Manufacturing, Zhejiang Guangsha Vocational and Technical University of Construction. Dongyang City 322100, Zhejiang Province, P.R. China
Fengqin Wu: Basic Department, Zhejiang Guangsha Vocational and Technical University of Construction, Dongyang City 322100, Zhejiang Province, P.R. China
Masoud Kiani, Mohammad Arefi: Department of Solid Mechanic, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran
