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CONTENTS
Volume 38, Number 4, February25 2021
 


Abstract
The present paper attempts to investigate the propagation of plane waves in an isotropic elastic medium under the effect of initial stress and temperature-dependent properties. The modulus of elasticity is taken as a linear function of the reference temperature. The formulation is applied under the thermoelasticity theory with dual-phase-lag; the normal mode analysis is used to obtain the expressions for the displacement components, the temperature, the stress, and the strain components. Numerical results for the field quantities are given in the physical domain and illustrated graphically. Comparisons are made with the results predicted by different theories (Lord–Shulman theory, the classical coupled theory of thermoelasticity and the dual-phase-lag model) in the absence and presence of the initial stress as well as the case where the modulus of elasticity is independent of temperature.

Key Words
thermoelasticity; initial stress; microstretch; dual-phase-lag; normal mode analysis; temperature-dependent

Address
Mohamed I.A. Othman, Magda E.M. Zidan and Ibrahim E.A. Mohamed: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Abstract
Although traditional steel-concrete composite beams have excellent structural characteristics, it cannot meet the requirement of quick assembly and repair in the engineering. This paper presents a study on static behavior of bolt connected steel-concrete composite beam without post-cast zone. A three-dimensional finite element model was developed with its accuracy and reliability validated by available experimental results. The analysis results show that in the normal service stage, the bolt is basically in the state of unidirectional stress with the loss of pretightening can be ignored. Parametric studies are presented to quantify the effects of the post-cast zone, size and position of splicing gap on the behavior of the beam. Based on the studies, suggested size of gap and installation order were proposed. It is also confirmed that optimized concrete slab in mid-span can reduce the requirement of construction accuracy.

Key Words
high-strength frictional bolt; steel-concrete composite beam; post-cast zone; prefabricated construction

Address
Ying Xing: College of Civil Engineering, Taiyuan University of Technology, Taiyuan 030024, China;
College of Civil Engineering, Hunan University, Changsha 410082, China
Yun Zhao, Qi Guo and Jin-feng Jiao: College of Civil Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Qing-wei Chen: Economic & Technology Research Institute of State Grid Shandong Electric Power Company, Jinan 250021, China
Ben-zhao Fu: State GRID Fujian Economic Research Institute, Fuzhou 350000, China


Abstract
Based on the spatial substructure hybrid simulation test (SHST) method, the seismic performance of a high-strength steel composite K-eccentrically braced frame (K-HSS-EBF) structure system is studied. First, on the basis of the existing pseudostatic experiments, a numerical model corresponding to the experimental model was established using OpenSees, which mainly simulated the shear effect of the shear links. A three-story and five-span spatial K-HSS-EBF was taken as the prototype, and SHST was performed with a half-scale SHST model. According to the test results, the validity of the SHST model was verified, and the main seismic performance indexes of the experimental substructure under different seismic waves were studied. The results show that the hybrid simulation results are basically consistent with the numerical simulation results of the global structure. The deformation of each story is mainly concentrated in the web of the shear link owing to shear deformation. The maximum interstory drifts of the model structure during Strength Level Earthquake (SLE) and Maximum Considered Earthquake (MCE) meet the demands of interstory limitations in the Chinese seismic design code of buildings. In conclusion, the seismic response characteristics of the K-HSS-EBFs are successfully simulated using the spatial SHST, which shows that the K-HSS-EBFs have good seismic performance.

Key Words
hybrid simulation; spatial substructure; high-strength steel; eccentrically braced frames; shear link

Address
Tengfei Li and Jiangran Guo: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, P.R. China
Mingzhou Su:School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, P.R. China;
Key Lab of Structural Engineering and Earthquake Resistance, Ministry of Education (XAUAT), Xi'an 710055, P.R. China


Abstract
This paper aims to verify the feasibility of rubber rings to mitigate the shear concentration in perfobond connector (PBL) groups. Firstly, modified push-out tests for five specimens with four holes were conducted to investigate the effects of rubber rings on the shear mechanism of PBL groups. The test results showed that by employing rubber rings on partial holes, more shear forces were distributed to the holes without rubber rings. The rubber rings significantly improved the slip ability of the specimens, and the ductility of PBL groups is dependent on the number and thickness of rubber rings. Subsequently, three-dimensional numerical models were established and validated by the experimental results. According to the plastic strain distribution in concrete dowels, the action principle of rubber rings in PBL groups was explained. Furthermore, the parametric study was conducted to investigate the influential factors on shear distributions, including the width of steel plates, the hole spacing, the number of holes, the rubber ring thickness, and the positions of rubber rings. The parametric analysis results showed that the redistribution of shear forces is significantly affected by the rubber rings with the smallest thickness. By properly employing rubber rings in PBL groups, the shear forces of holes are more even. Finally, an analytical model for PBL groups with rubber rings was proposed to predict the shear distribution at the serviceability stage.

Key Words
composite bridges; perfobond connector; rubber ring; modified push-out test; shear distribution

Address
Yangqing Liu and Yuqing Liu: Department of Bridge Engineering, Tongji University, Shanghai, China
Haohui Xin: Department of Bridge Engineering, Tongji University, Shanghai, China;
Faculty of Civil Engineering and Geosciences, Delft University of Technology, Netherlands


Abstract
The effective flange width was usually introduced into elementary beam theory to consider the shear lag effect in steel-concrete composite beams. Previous studies have primarily focused on the effective width under positive moments and elastic loading, whereas it is still not clear for negative moment cases in the normal service stages. To account for this problem, this paper proposed simplified formulas for the effective flange width and reinforcement stress of composite beams under negative moments in service stages. First, a 10-degree-of-freedom (DOF) fiber beam element considering the shear lag effect and interfacial slip effect was proposed, and a computational procedure was developed in the OpenSees software. The accuracy and applicability of the proposed model were verified through comparisons with experimental results. Second, a method was proposed for determining the effective width of composite beams under negative moments based on reinforcement stress. Employing the proposed model, the simplified formulas were proposed via numerical fitting for cases under uniform loading and centralized loading at the mid-span. Finally, based on the proposed formulas, a simplified calculation method for the reinforcement stress in service stages was established. Comparisons were made between the proposed formulas and design code. The results showed that the design code method greatly underestimated the contribution of concrete under negative moments, leading to notable overestimations in the reinforcement stress and crack width.

Key Words
effective flange width; composite beams; negative moments; fiber beam element

Address
Li Zhu, Bing Han and Wei Liu: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, PR China
Qi Ma: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, PR China
Wu-Tong Yan: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, PR China;
China Railway Economic and Planning Research Institute, Beijing 100038, PR China

Abstract
This paper presents experiments and theoretical analysis on shear behavior of eight concrete-encased square concrete-filled steel tube (CECFST) specimens and three traditional reinforced concrete (RC) specimens. A total of 11 specimens with the test parameters including the shear span-to-depth ratio, steel tube size and studs arrangement were tested to explore the shear performance of CECFST specimens. The failure mode, shear capacity and displacement ductility were thoroughly evaluated. The test results indicated that all the test specimens failed in shear, and the CECFST specimens enhanced by the interior CFST core exhibited higher shear capacity and better ductility performance than that of the RC specimens. When the other parameters were the same, the larger steel tube size, the smaller shear span-to-depth ratio and the existence of studs could lead to the more satisfactory shear behavior. Then, based on the compatible truss-arch model, a set of formulas were developed to analytically predict the shear strength of the CECFST members by considering the compatibility of deformation between the truss part, arch part and the steel tube. Compared with the calculated results based on several current design specifications, the proposed formulas could get more accurate prediction.

Key Words
concrete-encased square concrete-filled steel tube members (CECFST); shear capacity; experimental study; compatible truss-arch model; calculation method

Address
Yong Yang and Yunlong Yu: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi 710055, P.R. China;
Key Lab of Structural Engineering and Earthquake Resistance of the Ministry of Education,
Xi'an University of Architecture and Technology, Xi'an, Shaanxi, P.R. China
Xin Chen, Yicong Xue and Chaorui Zhang: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi 710055, P.R. China


Abstract
In this work, we consider a problem in the context of thermoelectric materials with memory-dependent derivative for a half space which is assumed to have variable thermal conductivity depending on the temperature. The Lame's modulii of the half space material is taken as a function of the vertical distance from the surface of the medium. The surface is traction free and subjected to a time dependent thermal shock. The problem was solved by using the Laplace transform method together with the perturbation technique. The obtained results are discussed and compared with the solution when Lame's modulii are constants. Numerical results are computed and represented graphically for the temperature, displacement and stress distributions. Affectability investigation is performed to explore the thermal impacts of a kernel function and a time-delay parameter that are characteristic of memory dependent derivative heat transfer in the behavior of tissue temperature. The correlations are made with the results obtained in the case of the absence of memory-dependent derivative parameters.

Key Words
thermoelectric materials; fractional order theory; variable of thermal conductivity; variable Lame's moduli; perturbation method; numerical results

Address
Magdy A. Ezzat: Department of Mathematics, College of Science and Arts, Qassim University, Al Bukairiyah, Saudi Arabia;
Department of Mathematics, Faculty of Education, Alexandria University, Alexandria, Egypt


Abstract
The concept of using Steel-concrete (SC) composite walls as retaining walls has recently been introduced by the authors and their effectiveness of resisting out-of-plane loads has also been demonstrated. In this paper, an improved analytical formulation based on partial interaction theory, which has previously been developed by the authors, is presented. The improved formulation considers a new loading condition and also accounts for cracking in concrete to simulate the real conditions. Due to a limited number of test specimens, further finite element (FE)simulations are performed in order to verify the analytical procedure in more detail. It is observed that the results from the improved analytical procedure are in excellent agreement with both experimental and numerical results. Moreover, a detailed parametric study is conducted using the developed FE model to investigate effects of different parameters, such as distance between shear connectors, shear connector length, concrete strength, steel plate thickness, concrete cover thickness, wall's width to thickness ratio, and wall' s height to thickness ratio, on the behavior of SC composite walls subjected to out-of-plane loads.

Key Words
SC composite wall; out-of-plane loads; partial interaction theory; finite element analysis; experimental test; retaining wall

Address
Saeid Sabouri-Ghomi and Arman Nasri: Civil Engineering Department, K.N. Toosi University of Technology, Tehran, Iran
Younes Jahani: Analysis and Advanced Materials for Structural Design (AMADE), Polytechnic School, University of Girona, Girona, Spain
Anjan K. Bhowmick: Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Canada


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