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CONTENTS
Volume 74, Number 6, June25 2020
 

Abstract
This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

Key Words
adhesion; delamination; failure index; SERR; T-joint; Tsai-Wu criterion; VCCT principle

Address
Subhransu K Panda, Pradeep K Mishra: Department of Mechanical Engineering, Centre for Advanced Post Graduate Studies, BPUT-769004, Rourkela, Odisha, India
Subrata K Panda: Department of Mechanical Engineering, NIT Rourkela, Rourkela-769008, Odisha, India

Abstract
Nowadays, composite plates are widely used as high-strength structures to fabricate a dynamic loading-resistant armours. In this study, the shock load is applied by an explosion of spherical TNT charge at a specified distance from the circular composite plate. The composite plate contains a two-layer ceramic-metal armour and a poly-methyl methacrylate (PMMA) target layer. The dynamic behavior of the composite armour has been investigated by measuring the transferred effective stress and maximum deflection into the target layer. For this purpose, the simulation of the blast loading upon the composite structure was performed by using the load-blast enhanced (LBE) procedure in Ls-Dyna software. The effect of main process parameters such as the thickness of layers, and scaled distance has been examined on the specific stiffness of the structure using response surface method. After validating the results by comparing with the experimental results, the optimal values for these parameters along with the regression equations for transferred effective stress and displacement to the target have been obtained. Finally, the optimal values of input parameters have been specified to achieve minimum transferred stress and displacement, simultaneously with reducing the weight of the structure.

Key Words
shock wave; composite armour; ceramic-metal; optimization; response surface method

Address
Mohammad Javad Rezaei, Mahdi Gerdooei: Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
Hasan Ghaforian Nosrati: Department of Mechanical Engineering, Esfarayen University of Technology, Esfarayen, North Khorasan, Iran

Abstract
High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 ✕ 600 ✕ 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.

Key Words
high-strength concrete; silica fume; fly ash; temperature development; cracking

Address
Chung-Hao Wu: Department of Civil Engineering, Chung Yuan Christian University, No. 200 Chung Pei Road, Chung Li Dist., Taoyuan City 320, Taiwan
Yu-Feng Lin: Department of Civil Engineering, Chienkuo Technology University, No.1, Chiehshou North Road, Changhua City 500, Taiwan
Shu-Ken Lin: Department of Civil Engineering, National Chung Hsing University, No. 145 Xingda Rd., South Dist., Taichung City 402, Taiwan
Chung-Ho Huang: Department of Civil Engineering, National Taipei University of Technology, No.1, Sec. 3, Zhongxiao E. Rd., Da\'an Dist.,Taipei City 106, Taiwan

Abstract
Granite is commonly used in the construction of the ancient stone pagodas of Korea. The material has excellent weathering resistance and durability, as well as high compressive strength. Most of the stone-made state-designated architectural heritage of Korea is made of granite. Therefore, the understanding of the structural feasibility of stone-made architectural heritage is crucial. Even though, until now, experimental studies for the reinforced stone have been rarely performed. This study intends to suggest a new methodology for the reinforcement of granite using a threaded titanium bar. Through the experimental study, the flexural behavior of the reinforced granite depending on the reinforcement ratio is investigated. Based on the test results, a moment–displacement relationship for the design of reinforced granite is suggested.

Key Words
restoration; ancient stone pagoda; granite; titanium bar; flexural behavior; reinforcement ratio;

Address
Department of Architectural Engineering, Wonkwang University, 460 Iksandae-ro, Iksan 54538, South Korea

Abstract
The paper provides an inside look into experimental measurements, followed by numerical simulations and their related uncertainties. The goal of the paper is to present findings related to blast loading and the handling of defects that are inherent in experiments. Very often it might seem that experiments are simplified reflections of real-life conditions. In most cases this is true, but there is a good reason for that. The more complex an experiment is, the larger the amount of uncertainties that can be expected. This especially applies when the blast loading of concrete is the subject of research. When simulations fail to reproduce the results of experimental measurements, it does not necessarily mean there is something wrong with the numerical model. The problem could be missing information. Put differently, the numerical simulation may lack information that seemed irrelevant with regard to the experiment. In the presented case, a reference simulation with a proven material model unexpectedly failed to replicate the results of an experiment where concrete slabs were exposed to blast loading. This resulted in a search for possible unknowns. When all of the uncertainties were examined, the missing information turned out to be the orientation of the charge to the concrete slab. Since the experiment was burdened with error, a sensitivity study had to take place so the influence of this factor could be better understood. The findings point to the fact that even the smallest defect during experiments must somehow be taken into account when designing numerical simulations. Otherwise, the simulations are not correlated to the experiments, but merely to some expectations.

Key Words
blast loading; metamodels; sensitivity study; Smoothed Particle Hydrodynamics; uncertainties

Address
Institute of Structural Mechanics, Faculty of Civil Engineering, Brno University of Technology, Veveri 331/95, 602 00 Brno, Czech Republic

Abstract
Multiple earthquakes that occur during short seismic intervals affect the inelastic behavior of the structures. Sequential ground motions against the single earthquake event cause the building structure to face loss in stiffness and its strength. Although, numerous research studies had been conducted in this research area but still significant limitations exist such as: 1) use of traditional design procedure which usually considers single seismic excitation; 2) selecting a seismic excitation data based on earthquake events occurred at another place and time. Therefore, it is important to study the effects of successive ground motions on the framed structures. The objective of this study is to overcome the aforementioned limitations through testing a two storey RC building structural model scaled down to 1/10 ratio through a similitude relation. The scaled model is examined using a shaking table. Thereafter, the experimental model results are validated with simulated results using ETABS software. The test framed specimen is subjected to sequential five artificial and four real-time earthquake motions. Dynamic response history analysis has been conducted to investigate the i) observed response and crack pattern; ii) maximum displacement; iii) residual displacement; iv) Interstorey drift ratio and damage limitation. The results of the study conclude that the low-rise building model has ability to resist successive artificial ground motion from its strength. Sequential artificial ground motions cause the framed structure to displace each storey twice in correlation with vary first artificial seismic vibration. The displacement parameters showed that real-time successive ground motions have a limited impact on the low-rise reinforced concrete model. The finding shows that traditional seismic design EC8 requires to reconsider the traditional design procedure.

Key Words
time history analysis; reinforced concrete framed structure; sequential ground motions; shaking table; ETABS; Buckingham π theorem

Address
Syed Muhammad Bilal Haider, Zafarullah Nizamani: Department of Environmental Engineering, Universiti Tunku Abdul Rahman, 31900 Kampar, Malaysia
Chun Chieh Yip: Department of Civil Engineering, Universiti Tunku Abdul Rahman, 43000 Kajang, Malaysia

Abstract
For the first time, the influence of in-plane magnetic field on wave propagation of Graphene Nano-Platelets (GNPs) polymer composite nanoplates is investigated here. The impact of three- parameter Kerr foundation is also considered. There are two different reinforcement distribution patterns (i.e. uniformly and non-uniformly) while the material properties of the nanoplate are estimated through the Halpin-Tsai model and a rule of mixture. To consider the size-dependent behavior of the structure, Eringen Nonlocal Differential Model (ENDM) is utilized. The equations of wave motion derived based on a higher-order shear deformation refined theory through Hamilton's principle and an analytical technique depending on Taylor series utilized to find the wave frequency as well as phase velocity of the GNPs reinforced nanoplates. A parametric investigation is performed to determine the influence of essential phenomena, such as the nonlocality, GNPs conditions, Kerr foundation parameters, and wave number on the both longitudinal and flexural wave characteristics of GNPs reinforced nanoplates.

Key Words
wave propagation; nanocomposite plate; graphene nanoplatlets; magnetic field; Kerr foundation

Address
Behrouz Karami, Davood Shahsavari: Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran
Parastoo Gheisari: School of Mechanical Engineering, Shiraz University, Shiraz, Iran
Seyed Mohammad Reza Nazemosadat: Sama Technical and Vocational Training College, Islamic Azad University, Shiraz Branch, Shiraz, Iran
Payam Akbari: Department of Civil Engineering, Tehran South Branch, Islamic Azad University, Tehran, Iran
Matin Naghizadeh: Department of Chemistry, Shahid Bahonar University of Kerman, Kerman, Iran

Abstract
The fundamental period is an important parameter for seismic design and seismic risk assessment of building structures. In this paper, a simplified theoretical method to predict the fundamental period of masonry infilled reinforced concrete (RC) frame is developed based on the basic theory of engineering mechanics. The different configurations of the RC frame as well as masonry walls were taken into account in the developed method. The fundamental period of the infilled structure is calculated according to the integration of the lateral stiffness of the RC frame and masonry walls along the height. A correction coefficient is considered to control the error for the period estimation, and it is determined according to the multiple linear regression analysis. The corrected formula is verified by shaking table tests on two masonry infilled RC frame models, and the errors between the estimated and test period are 2.3% and 23.2%. Finally, a probability-based method is proposed for the corrected formula, and it allows the structural engineers to select an appropriate fundamental period with a certain safety redundancy. The proposed method can be quickly and flexibly used for prediction, and it can be hand-calculated and easily understood. Thus it would be a good choice in determining the fundamental period of RC frames infilled with masonry wall structures in engineering practice instead of the existing methods.

Key Words
fundamental period; masonry wall; infilled RC frame; theoretical method; hand-calculated; probability

Address
Rui Jiang and Lingyu Zhou: School of Civil Engineering, Central South University, Changsha 410075, China
School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510641, China
Liqiang Jiang: School of Civil Engineering, Central South University, Changsha 410075, China
Yi Hu School of Civil Engineering, Chang


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