Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 79, Number 2, July25 2021
 


Abstract
In recent years, with the maximization of control design and efficiency, and the improvement of economy and energy efficiency, building technology and control in the theory have attracted the attention of lots researchers. By trying various control theorems, many numerical methods have been investigated in the literature to achieve this target, but all these numerical methods are difficult to work out the problem correctly. This paper puts forward a potentially feasible evolutionary bat algorithm (EB) method for active control of earthquake-induced vibration in building structures. Based disturbance observer based control and S surface combined with the robust adaptive control scheme for solving optimization problems proposed, an important contribution in the control law is what the configuration control in the present study should not require known uncertainty limits and the disturbance is eliminated. A simulation case study was proposed to illustrate the possibility of implementing an apparent learning method in ANN to effectively control structural vibration under the influence of systematic motion under earthquake citations. The proposed learning numerical methods does not need to develop a mathematical model of structural dynamics or train another neural network to approximate the actual structural response to be performed.

Key Words
artificial intelligent control; evolutionary bat algorithm; fuzzy control; fuzzy systematic design

Address
Z.Y. Chen, Ruei-yuan Wang, Yahui Meng: School of Science, Guangdong University of Petrochem Technology, Maoming 525000, PR China
Qiuli Fu: School of Computer Science, Guangdong University of Petrochem Technology, Maoming 525000, PR China
Timothy Chen: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA

Abstract
One of the main concerns of engineers to design a structural member using structural lightweight concrete is the shear performance of this concrete due to its lower tensile strength. This research presents an experimental investigation on the shear behaviour of reinforced palm-oil by-product lightweight concrete beams without shear links. The used by-products are wastes from oil palm industry i.e., oil palm shell (OPS) and oil-palm-boiler clinker (OPBC). They used as coarse aggregate in the concrete mixture while normal sand was used as fine aggregate. Nine reinforced OPS and OPS-OPBC lightweight concrete beams were prepared and their structural performance in terms of shear behaviour have been investigated. Three sets of the lightweight aggregate concretes with the maximum oven dry density less than 2000 kg/m3 were designed and each set contained three concrete mixes of grades 25, 35, and 45. The results of this study show that the OPS concrete beams have lower ultimate capacity in comparison with blended coarse aggregates (OPS-OPBC) concrete beams. The contribution of OPBC aggregate in the OPS concrete improved the structural performance and the failure nature of the beams, significantly. It was found that from the existing prediction models for estimating shear capacity of concrete beams, the shear capacity can be predicted about 10% underestimate and up to 60% overestimate.

Key Words
by-products; lightweight aggregate concrete; oil-palm-boiler clinker; oil palm shell; shear behaviour

Address
Payam Shafigh: Centre for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia
Muhammad Aslam: Department of Civil Engineering, School of Engineering & Technology, Institute of Southern Punjab, 60000 Multan, Pakistan
Soon Poh Yap: Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

Abstract
In the present paper, the free vibration behavior of functionally graded plates containing straight and curved embedded crack is investigated. A NURBS-based multi-patch isogeometric analysis formulation is utilized based on the firstorder shear deformation plate theory. The Nitsche technique is implemented to meet the inter-patch connection constraints. The crack line is assumed as a narrow cut along a straight or free-shape curve path within the plate. The crack growth phenomena are overlooked. The accuracy and quality of the obtained results are compared to those available in the literature. Subsequently, the effect of various material and geometry parameters on the free vibration characteristics of cracked FG plate including the volume-fraction index, crack shape, crack length, crack orientation and, crack location are examined. It learned that the straight crack inclination angle mainly influences the fifth and fourth natural modes. Moreover, the FGM mixture index doesn't noticeably affect the frequency trends. No considerable impact is noted between the edge constraint setups on the fundamental frequency.

Key Words
curved crack; embedded narrow crack; FGM plate; free vibration; multi-patch isogeometric analysis

Address
Vahid Khalafi: Aerospace Engineering Department, Shahid Sattari Aeronautical University of Science and Technology, Tehran, Iran
Jamshid Fazilati: Department of Aeronautical Science and Technology, Aerospace Research Institute, P.O. Box: 14665-834, Tehran, Iran

Abstract
The purpose of this study is to investigate the size effect, loading rate, and smeared crack models in the nonlinear seismic behavior of concrete arch dams. One of the important parameters in the design of arch concrete dams is the tensile strength of unreinforced mass concrete. Various fracture parameters obtained from experimental results reported for concrete in order to study the size-effect is used in this paper. In the present analysis, the smeared crack method is used in finite element analysis of the Morrow Point arch dam subjected to three components of the TAFT earthquake as a case study. The dependence of fracture, and especially of the size effect, on the loading rate is described. Models incorporating nonlinear analysis in three cases with and without the size effect of dam concrete and fluid-structure interaction are employed to evaluate and compare them. The water is taken as an inviscid, compressible fluid, and the foundation is rigid. From the study, it is concluded that the participation of the size effect leads to higher values of maximum displacements and stresses in benchmark points compared to the model that ignores the size effect. The crack initiation criterion based on the maximum tensile stress according to the size effect of concrete, and also the dynamic loading range should be defined. Results show considering fixed smeared crack models used in the concrete specimen as well as the size effect of concrete materials, will lead to the crack profile is more realistic and will represent near to real behavior of concrete fracture. The results are of significant interest for the concrete fracture of dams; hence the loading rate should be adopted for fracture properties obtained in dams.

Key Words
concrete arch dam; fluid-structure interaction; loading rate; nonlinear fracture models; size effect; smeared crack; three-point bending test

Address
Amir Pirooznia and Amir Javad Moradloo: Department of Civil Engineering, School of Engineering, University of Zanjan, Zanjan, Iran

Abstract
The energy dissipation characteristics of core materials greatly influence the working performance of bucklingrestrained braces (BRBs), so it is a vital work to develop more excellent energy dissipation core materials. In this research, a series of experimental studies are conducted, including the mechanical properties of PM-35 steels and the working performance of PM-35 BRB specimens, which serve to investigate the feasibility of PM-35 steel as core materials of BRBs. In addition, the analysis of variance (ANOVA) has been conducted to study the sensitivity factors of energy dissipation of PM-35 BRB specimens, especially the pre-force applied on the BRB specimens. According to the results of this research, it can be concluded that the energy absorption efficiency of PM-35 BRBs specimens is much higher than that of BRB specimens with ordinary core materials; the internal pores greatly weaken the yield strength of PM-35 steel and obviously improve the plastic deformation capacity, which makes that PM-35 core materials are able to absorb energy in a lower stress level; pre-force applied on core materials is the key factor governing the energy absorption, and can significantly improve the working performance of BRB specimens with PM-35 core materials.

Key Words
buckling-restrained braces; cyclic loading; energy dissipation capacity; PM-35 steel

Address
Chao Zhao, Qianqian Chen, Xingu Zhong, Tianyu Zhang and Zhiwen Chen: Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control & School of Civil Engineering, Hunan University of Science and Technology, Taoyuan Road, Yuhu District, Xiangtan, China

Abstract
A mixed element (3fME) for geometric and material nonlinear finite element analysis of plane skeletal structures is presented, which can reach any predefined accuracy with only one element per structural member. This element is based on the 3-field approach−an application of the Hu-Washizu principle−directly approximating the fields of displacements, strains and stresses. The presented formulation considers both (i) geometrically nonlinear behavior−by including the second-order term in the strain-displacement relations and establishing equilibrium in the deformed configuration−and (ii) materially nonlinear elastoplastic behavior, at the fibre level, automatically handling the axial-bending interaction. The illustrative examples include both compression- and tension-bending interaction, and compare the accuracy of the novel finite element with published results.

Key Words
3-field mixed finite element; beam-column finite element; geometric nonlinearity; modelling of skeletal structures; very coarse meshes

Address
Miguel Ferreira: CERIS, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisboa, Portugal
Paulo Providência: University of Coimbra, INESC Coimbra, DEC, 3030-290 Coimbra, Portugal
Ricardo Costa: Civil Engineering Department, ISISE, University of Coimbra, 3030-788 Coimbra, Portugal
Pedro Gala: DEC ESTG, INESC Coimbra, Polytechnic Institute of Leiria, 2411-901 Leiria, Portugal
João Almeida: DECivil, ICIST, CERIS, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisboa, Portugal

Abstract
The flexural performance of 8 types of prestressed concrete beams with plastic bellows under different grouting compactness is examined in this paper. By applying concentrated load and symmetrical load to 8 types of prestressed concrete test beams with plastic bellows, the flexural performance test of each test beam is carried out, and the mechanical characteristics and failure morphology of each test beam under different grouting compactness are discussed. The influence of duct grouting compactness on the strain of steel bars and concrete, mid-span deflection and stiffness of prestressed concrete beam are analyzed. The results show that the cracking load and ultimate load of the test beam increases constantly with the increase of the duct grouting compactness, and the flexural bearing capacity of prestressed concrete beams has also been significantly improved. After the concrete is cracked, the mid-span deflection of the prestressed concrete beam gradually decreases with the increase of the duct grouting compactness under the same load form and load grade. At the same load grade, the mid-span deflection change of prestressed concrete beams under concentrated load is much larger than that under symmetric load. The ductility coefficient of prestressed concrete beams with plastic bellows decreases as the grouting compactness increases. In engineering practice, the quality of duct grouting compactness about the prestressed concrete beam should be strictly controlled and improved.

Key Words
flexural performance; grouting compactness; plastic bellows; prestressed beams; test

Address
Xuansheng Cheng, Junliang Hong: Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, 730050, PR China
Liang Ma, Guoliang Li: Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, No. 287 Langongping Road, Lanzhou, 730050; PR China

Abstract
There is normally the occurrence of pre-existing cracks and holes in coal mass to influence its mechanical behaviours. And the crack initiation and propagation around the tip of pre-existing cracks can be observed to induce the overall failure of coal mass finally. In this study, two groups of hole with the radius of 10 mm connecting one crack with length and width of 20 mm and 1 mm, respectively, were pre-existed in sample to explore the influence of crack angle (from 0 to 90o) on the unconfined compressive strength (UCS), crack initiation and propagation, and failure modes of coal mass with combined faults by using RFPA2D. The results showed that the stress-strain curves of specimen with double-hole-crack exhibit multiple stress drop compared to that of intact coal sample, especially in the post-peak stage. Moreover, UCS decreased firstly with the crack angle increasing to 30o and then increased until the crack angle reaching to 75o following by decreasing with the continuous increase of crack angle to 90o. In addition, the failure mode of double-hole-crack specimen with the crack angle of 0-30o can be regards as the dominated tensile failure combined with shear failure, which was consist with the failure pattern of intact specimen. On the other hand, the failure mode of double-hole-crack specimen with the crack angle of 45-90o is the dominated shear failure combined with tensile failure. Meanwhile, the distribution characteristics of acoustic emission energy can be used to better reflect the deformation and failure process of coal mass with combined defects.

Key Words
acoustic emission; crack angle; crack initiation and propagation; double-hole-crack coal specimen; failure mode

Address
Huayong Lv: School of Architecture and Engineering, Shangqiu Normal University, Shangqiu, 476000, China; School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454003, China
Zhanbo Cheng: School of Engineering, University of Warwick, Coventry, CV47AL, UK
Yaqing Dong: School of Architecture and Engineering, Shangqiu Normal University, Shangqiu, 476000, China
Jing Zhang: School of Mathematics and Statistics, Shangqiu Normal University, Shangqiu, 476000, China
Yujie Ma: School of Architecture and Engineering, Shangqiu Normal University, Shangqiu, 476000, China

Abstract
The current investigation deals with assessing the search performance of a recently developed, parameter-free, and self-adaptive search algorithm so-called Interactive Fuzzy Search Algorithm (IFSA) in solving weight minimization of the constrained structural optimization problems with discrete variables. The proposed IFSA combines the navigation pattern of the Interactive Search Algorithm (ISA) with the decision-making competence of fuzzy reasoning. The fuzzy module of the proposed IFSA permanently monitors the search process and adjusts each agent's search behavior by considering the governing condition of the current problem. In structural optimization, due to construction limitations, it is more realistic to select the sizing variables from a discrete domain. Thus, in this study, to empirically evaluate the search capability of the IFSA, it is applied to solve a suite of structural optimization problems with the discrete design variables. The attained outcomes are compared with the ISA and some other related methods addressed in the relevant literature. The acquired accuracy level and demanded number of objective function evaluations indicates that the IFSA, comparatively, using lower computational cost could found lighter structural systems. Also, the comparison of the attained standard deviation values shows that the IFSA demonstrates higher stability during the optimization process. These superior outcomes designate that the fuzzy decision-making mechanism of the IFSA could work properly in dynamically adapting the search behavior of the algorithm with the governing condition of the current problem. Consequently, the promising gained results reveal that IFSA can effectively be applied in solving the structural optimization problems with discrete search domains.

Key Words
fuzzy logic; hybrid methods; metaheuristic methods; structural optimization

Address
Ali Mortazavi: Graduate School of Natural and Applied Science, Ege University, Izmir, Turkey

Abstract
The present study addresses the issue of seismic control of active mass damper (AMD) devices in the presence of time-delay for the tall buildings taking into account soil-structure interaction (SSI) effects. Considering the simultaneous effects of the time-delay and SSI, a control scheme of linear quadratic regulator (LQR) controller with a new form of the weighting matrices is proposed. Then, a design procedure based on a particle swarm optimization (PSO) algorithm is proposed to find the optimal weighting matrices of the controller. The numerical studies are conducted on a benchmark tall building. The validity of the proposed LQR controller is demonstrated for the structure subjected to 44 well-known earthquakes. It is concluded that ignoring the SSI and time-delay effects may give an incorrect estimation of the seismic demands of the building. By increasing the soil softness, the structural responses are often increased. Furthermore, it is found that the proposed controller gives a worthy performance in mitigation of maximum top floor displacement for different soil conditions in the presence of time-delays. However, in the presence of long time-delay, a significant increment may achieve for maximum floor acceleration, especially for the soft and medium soils. However, the maximum drifts of the floors remain within the allowed ranges.

Key Words
active mass damper; LQR controller; SSI effects; structural control; tall buildings; time-delay effect

Address
Sadegh Etedali: Department of Civil Engineering, Birjand University of Technology, P.O. Box 97175-569, Birjand, Iran
Mohammad Shahi: Imam Reza Technical and Vocational Scholl, Sarayan, Iran


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2021 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-2-736-6800 (GAE, EAS, WAS, ANR), +82-42-828-7995 (SEM, SCS, SSS) Fax : +82-2-736-6801, Email: info@techno-press.com