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CONTENTS
Volume 74, Number 1, April10 2020
 

Abstract
For the large deformation of shear walls under vertical and horizontal loads, there are difficulties in obtaining accurate simulation results using the response analysis method, even with fine mesh elements. Furthermore, concrete material nonlinearity, stiffness degradation, concrete cracking and crushing, and steel bar damage may occur during the large deformation of reinforced concrete (RC) shear walls. Matrix operations that are involved in nonlinear analysis using the traditional finite-element method (FEM) may also result in flaws, and may thus lead to serious errors. To solve these problems, a planar four-node element was developed based on vector mechanics. Owing to particle-based formulation along the path element, the method does not require repeated constructions of a global stiffness matrix for the nonlinear behavior of the structure. The nonlinear concrete constitutive model and bilinear steel material model are integrated with the developed element, to ensure that large deformation and damage behavior can be addressed. For verification, simulation analyses were performed to obtain experimental results on an RC shear wall subjected to a monotonically increasing lateral load with a constant vertical load. To appropriately evaluate the parameters, investigations were conducted on the loading speed, meshing dimension, and the damping factor, because vector mechanics is based on the equation of motion. The static problem was then verified to obtain a stable solution by employing a balanced equation of motion. Using the parameters obtained, the simulated pushover response, including the bearing capacity, deformation ability, curvature development, and energy dissipation, were found to be in accordance with the experimental observation. This study demonstrated the potential of the developed planar element for simulating the entire process of large deformation and damage behavior in RC shear walls.

Key Words
vector mechanics; planar element; large deflection; nonlinear analysis; RC shear walls

Address
Hongmei Zhang, Yuanfeng Duan, Chung Bang Yun: College of Civil Engineering and Architecture, Zhejiang University, 866, Yuhangtang Road, Hangzhou, 310058, China
Yufei Shan, Song LiuDepartment of Disaster Mitigation for Structures, Tongji University, 1239, Siping Road, Shanghai, 200092, China

Abstract
Metallic energy-dissipation dampers are widely used in structures. They are comprised of an added damping and stiffness (ADAS) device with many parallel, diamond-shaped hole plates, the neck width of which is an important parameter. However, no studies have analyzed the neck width's influence on the ADAS device's performance. This study aims to better understand that influence by conducting a pseudo-static test on ADAS, with three different neck widths, and performing finite element analysis (FEA) models. Based on the FEA results and mechanical theory, a design neck width range was proposed. The results showed that when the neck width was within the specified range, the diamond-shaped hole plate achieved an ideal yield state with minimal stress concentration, where the ADAS had an optimal energy dissipation performance and the brittle shear fracture on the neck was avoided. The theoretical values of the ADAS yield loads were in good agreement with the test values. While the theoretical value of the elastic stiffness was lower than the test value, the discrepancy could be reduced with the proposed modified coefficient.

Key Words
ADAS device; diamond-shaped hole plates; neck width; pseudo-static test; metallic energy-dissipation dampers

Address
Yingxiong Wu:College of Civil Engineering, Fuzhou University, No.2 North Avenue of Wulong River, Fuzhou, Fujian, China
Jianfeng Lu: Department of Civil and Environmental Engineering, Harbin Institute of Technology (Shenzhen), Taoyuan Street,
Nanshan District, Shenzhen, Guangdong, China
Yun Chen: Nantong LANKE Damping Technology Co., Ltd. No.1101 Xinkai Street, Chongchuan District, Nantong, Jiangsu, China

Abstract
The aim of this study is to calculate natural frequencies and harmonic responses of cracked frames with general boundary conditions by using transfer matrix method (TMM). The TMM is a straightforward technique to obtain harmonic responses and natural frequencies of frame structures as the method is based on constructing a relationship between state vectors of two ends of structure by a chain multiplication procedure. A single variable shear deformation theory (SVSDT) is applied, as well as, Timoshenko beam theory (TBT) and Euler-Bernoulli beam theory (EBT) for comparison purposes. Firstly, free vibration analysis of intact and cracked frames are performed for different crack ratios using TMM. The crack is modelled by means of a linear rotational spring that divides frame members into segments. The results are verified by experimental data and finite element method (FEM) solutions. The harmonic response curves that represent resonant and anti-resonant frequencies directly are plotted for various crack lengths. It is seen that the TMM can be used effectively for harmonic response analysis of cracked frames as well as natural frequencies calculation. The results imply that the SVSDT is an efficient alternative for investigation of cracked frame vibrations especially with thick frame members. Moreover, EBT results can easily be obtained by ignoring shear deformation related terms from governing equation of motion of SVSDT.

Key Words
cracked frame; free vibration; harmonic response; single variable shear deformation theory; transfer matrix method

Address
Baran Bozyigit and Yusuf Yesilce:Department of Civil Engineering, Dokuz Eylul University, Buca, Izmir, Turkey
Magd Abdel Wahab:
1 Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
2 Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Abstract
The common practice to predict the characteristic structural load effects (LEs) in long reference periods is to employ the extreme value theory (EVT) for building limit distributions. However, most applications ignore that LEs are driven by multiple loading events and thus do not have the identical distribution, a prerequisite for EVT. In this study, we propose the composite extreme value modeling approach using clustering to (a) cluster initial blended samples into finite identical distributed subsamples using the finite mixture model, expectation-maximization algorithm, and the Akaike information criterion; (b) combine limit distributions of subsamples into a composite prediction equation using the generalized Pareto distribution based on a joint threshold. The proposed approach was validated both through numerical examples with known solutions and engineering applications of bridge traffic LEs on a long-span bridge. The results indicate that a joint threshold largely benefits the composite extreme value modeling, many appropriate tail approaching models can be used, and the equation form is simply the sum of the weighted models. In numerical examples, the proposed approach using clustering generated accurate extrema prediction of any reference period compared with the known solutions, whereas the common practice of employing EVT without clustering on the mixture data showed large deviations. Real-world bridge traffic LEs are driven by multi-events and present multipeak distributions, and the proposed approach is more capable of capturing the tendency of tailed LEs than the conventional approach. The proposed approach is expected to have wide applications to general problems such as samples that are driven by multiple events and that do not have the identical distribution.

Key Words
structural load effect; extreme value modeling; clustering; non-identical distribution; peaks over threshold; generalized Pareto distribution

Address
Junyong Zhou, Chudong Pan:Guangzhou University
Xin Ruan, Xuefei Shi:Tongji University

Abstract
A significant defect of space structures is the progressive collapse issue which may restrict their applicability. Force limiting devices (FLDs) have been designed to overcome this deficiency, though they do not operate efficiently in controlling the force displacement characteristics. To overcome this flaw, a new type of FLD is introduced in the present study. The "all steel accordion force limiting device" (AFLD) which consists of three main parts including cylindrical accordion solid core, tubular encasing and joint system is constructed and its behavior has been studied experimentally. To improve AFLD's behavior, Finite element analysis has been carried out by developing models in ABAQUS software. A comprehensive parametric study is done by considering the effective design parameters such as core material, accordion wave length and accordion inner diameter. From the results, it is found that AFLD can obtain a perfect control on the force-displacement characteristics as well as attaining the elastic-perfect plastic behavior. Obtaining higher levels of ultimate load carrying capacity, dissipated energy and ductility ratio can be encountered as the main privileges of this device. Ease of construction and erection are found to be further advantages of AFLD. Based on the obtained results, a procedure for predicting AFLD's behavior is offered.

Key Words
space structure; force limiting device; accordion; progressive collapse; FEA

Address
Maryam Poursharifi, Karim Abedi, Mohammadreza Chenaghlou: Faculty of Civil Engineering, Sahand University of Technology, Tabriz, Iran
Robert B. Fleischman: Department of Civil Engineering and Engineering Mechanics, School of Engineering, University of Arizona,
1209 E. 2nd St., Tucson, AZ 85721, United States

Abstract
Several classical and higher order plate theories were used to study the buckling of functionally graded material (FGM) plates. In the great majority of research, a power function is used to represent metal and ceramic material transverse distribution (P-FGM). Therefore, the effect of having other transverse variation of material properties on the buckling behavior of thick rectangular FGM plates was not properly addressed. In the present work, this effect is investigated using the Third order Shear Deformable Theory (TSDT) for the case of simply supported FGM plate. Both a sigmoid function and an exponential functions are used to represent the transverse gradual property variation. The plate governing equations are combined with a Navier type expanded solution of the unknown displacements to derive the buckling equation in terms of the pre-buckling in-plane loads. Finally, the critical in-plane load is calculated for the different buckling modes. The model is verified by a comparison of the calculated buckling loads with available published results of Al-SiC P-FGM plates. The conducted parametric study shows that manufacturing FGM plates with sigmoid variation of properties in the thickness direction increases the buckling load considerably. This improvement is found to be more significant for the case of thick plates than that of thin plates. Results also show that this stiffening-like effect of the sigmoid function profile is more evident for cases where the in-plane loads are applied along the shorter edge of the plate.

Key Words
functionally graded materials; buckling; thick plates; simply supported; sigmoid function; P-FGM, S-FGM; E-FGM

Address
Department of Aerospace Engineering, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia

Abstract
A mathematical analysis has been carried out for understanding the traversal attributes of torsional waves in a Voigt-type viscoelastic porous layer bounded with corrugated surfaces resting over a heterogeneous transversely isotropic gravitating semi-infinite medium. Both the media are assumed to be under the effect of initial stresses acting along horizontal directions. In the presumed geometry, continuous and periodic type of corrugation has been considered. The condensed form of dispersion relation has been obtained analytically with the aid of the Whittaker's function and suitable boundary conditions. The influence of viscoelasticity, porosity, initial stresses, heterogeneity, gravity, undulation and position parameters on the phase and damped velocities has been illustrated graphically. In addition, relative examination investigating the impact of corrugated and planar bounded surfaces on the dispersion and damping characteristics is one of the important highlights of this study.

Key Words
torsional waves; Voigt-type viscoelastic; porous; Whittaker's function; corrugation; phase velocity; damped velocity

Address
Department of Mathematics and Computing, Indian Institute of Technology (Indian School of Mines) Dhanbad, India

Abstract
In this work, a novel higher-order shear deformation theory (HSDT) for static and free vibration analysis of functionally graded (FG) plates is proposed. Unlike the conventional HSDTs, the proposed theory has a novel displacement field which includes undetermined integral terms and contains fewer unknowns. Equations of motion are obtained by using Hamilton's principle. Analytical solutions for the bending and dynamic investigation are determined for simply supported FG plates. The computed results are compared with 3D and quasi-3D solutions and those provided by other plate theories. Numerical results demonstrate that the proposed HSDT can achieve the same accuracy of the conventional HSDTs which have more number of variables.

Key Words
bending; vibration; functionally graded plate; shear deformation theory

Address
Fatima Zohra Zaoui, Abdelouahed Tounsi, Djamel Ouinas and Jaime A. Viña Olay
et

Abstract
This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included infill walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the infill walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.

Key Words
operational modal analysis; dynamic characteristics; ambient vibration; RC frames

Address
Department of Civil Engineering, Aksaray University, 68100 Merkez, Aksaray, Turkey

Abstract
This study proposes a new shape memory alloy-tuned mass damper (SMA-TMD) and investigates the effectiveness of this damper in reducing and controlling the vibrations of a transmission tower-line system under various seismic excitations. Based on a practical transmission line system and considering the geometric nonlinearity of this system, the finite element (FE) software ANSYS is used to create an FE model of the transmission tower-line system and simulate the proposed SMA-TMD. Additionally, the parameters of the SMA springs are optimized. The effectiveness of a conventional TMD and the proposed SMA-TMD in reducing and controlling the vibrations of the transmission tower-line system under seismic excitations is investigated. Moreover, the effects of the ground motion intensity and frequency ratio on the reduction ratio (η) of the SMA-TMD are studied. The vibration reduction effect of the SMA-TMD under various seismic excitations is superior to that of the conventional TMD. Changes in the ground motion intensity and frequency ratio have a significant impact on the η of the SMA-TMD. As the ground motion intensity and frequency ratio increase, the η values of the SMA-TMD first increase and then decrease. Studying the vibration reduction effects of the SMA-TMD can provide a reference for the practical engineering application of this damper.

Key Words
transmission tower-line system; shape memory alloy; tuned mass damper; vibration reduction and control; seismic excitation

Address
Li Tian, Mengyao Zhou, Canxing Qiu and Kunjie Rong: School of Civil Engineering, Shandong University, Jinan 250061, Shandong, China
Canxing Qiu: Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education,
Beijing University of Technology, Beijing 100124, China

Abstract
There are separate merits and demerits to wood and steel. The combination of wood and steel as a compound section is able to improve the properties of both and ultimately increase their final bearing capacity. The composite cross-section made of steel and wood has higher hardness while showing more ductility and the local buckling of steel is delayed or completely prevented. The purpose of this study is to investigate the behavior of composite columns enclosed in wooden logs and the hollow sections of steel that will be examined in a laboratory environment under the axial load to determine the final bearing capacity and sample deformation. In terms of methodology, steel sheet and carbon fiber reinforced polymer sheet (FRP) are tested to construct hollow rectangular sections and reinforce timber. Besides, the method of connecting hollow sections and timber including glue and screw has been also investigated. As a result, timber lumber enclosed with carbon fiber-reinforced polymer sheets in which fibers are horizontally located at 90º are more resistant with better ductility.

Key Words
composite section; FRP; timber; bearing capacity; steel sheet

Address
Leila Razavian, Morteza Naghipour: Civil Engineering Faculty, Babol Noshirvani University of Technology. Babol, Iran
Mahdi Shariati: Division of Computational Mathematics and Engineering, Institute for Computational Science,
Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
Mahdi Shariati: Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
Maryam Safa: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

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