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CONTENTS
Volume 9, Number 5, May 2020
 

Abstract
In high rise buildings that utilize precast large panel system for construction, the shear wall provides strength and stiffness during earthquakes. The performance of a wall panel system depends mainly on the type of connection used to transfer the forces from one wall element to another wall element. This paper presents an experimental investigation on different types of construction detailing of the precast wall to wall vertical connections under reverse cyclic loading. One of the commonly used connections in India to connect wall to wall panel is the loop bar connection. Hence for this study, three types of wet connections and one type of dry connection namely: Staggered loop bar connection, Equally spaced loop bar connection, U-Hook connection, and Channel connection respectively were used to connect the precast walls. One third scale model of the wall was used for this study. The main objective of the experimental work is to evaluate the performance of the wall to wall connections in terms of hysteretic behaviour, ultimate load carrying capacity, energy dissipation capacity, stiffness degradation, ductility, viscous damping ratio, and crack pattern. All the connections exhibited similar load carrying capacity. The U-Hook connection exhibited higher ductility and energy dissipation when compared to the other three connections.

Key Words
precast concrete; wall to wall; wet connections; dry connections; reverse cyclic loading

Address
S. Hemamalini and R. Vidjeapriya: College of Engineering, Guindy, Anna University, Chennai, India

Abstract
The influence of subsequent curing on the performance of fly ash contained mortar under steam curing was studied. Mortar samples incorporated with different content (0%, 20%, 50% and 70%) of Class F fly ash under five typical subsequent curing conditions, including standard curing (ZS), water curing(ZW) under 25oC, oven-dry curing (ZD) under 60oC, frozen curing (ZF) under -10oC, and nature curing (ZN) exposed to outdoor environment were implemented. The unsteady chloride diffusion coefficient was measured by rapid chloride migration test (RCM) to analyze the influence of subsequent curing condition on the resistance to chloride penetration of fly ash contained mortar under steam curing. The compressive strength was measured to analyze the mechanical properties. Furthermore, the open porosity, mercury intrusion porosimetry (MIP), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) were examined to investigate the pore characteristics and phase composition of mortar. The results indicate that the resistance to chloride ingress and compressive strength of steam-cured mortar decline with the increase of fly ash incorporated, regardless of the subsequent curing condition. Compared to ZS, ZD and ZF lead to poor resistance to chloride penetration, while ZW and ZN show better performance. Interestingly, under different fly ash contents, the declining order of compressive strength remains ZS>ZW>ZN>ZD>ZF. When the fly ash content is blow 50%, the open porosity grows with increase of fly ash, regardless of the curing conditions are diverse. However, if the replacement amount of fly ash exceeds a certain high proportion (70%), the value of open porosity tends to decrease. Moreover, the main phase composition of the mortar hydration products is similar under different curing conditions, but the declining order of the CS-H gels and ettringite content is ZS>ZD>ZF. The addition of fly ash could increase the amount of harmless pores at early age.

Key Words
steam-cured mortar; subsequent curing condition; fly ash; chloride resistance; microstructure

Address
Yuquan Hu: College of Civil and Transportation Engineering, Hohai University, 1 Xikang Road, Nanjing, China
Shaowei Hu: School of Civil Engineering, Chongqing University, 174 Shazheng Road, Chongqing, China
Bokai Yang: The College of Mechanics and Materials, Hohai University, 8 Fucheng West Road, Nanjing, China
Siyao Wang: School of Water Resources and Hydropower Engineering, Wuhan University,8 Donghu South Road, Wuhan, China

Abstract
Mechanical and thermal properties of composite sandwich wall panels are affected by changes in their external environment. Humidity and temperature changes induce stress on wall panels and their core connectors. Under the action of ambient temperature, temperature on the outer layer of the wall panel changes greatly, while that on the inner layer only changes slightly. As a result, stress concentration exists at the intersection of the connector and the wall blade. In this paper, temperature field and stress field distribution of UHPC-RW-RC (Ultra-High Performance Concrete - Rock Wool - Reinforced Concrete) wall panel under high temperature-sprinkling and heating-freezing conditions were investigated by using the general finite element software ABAQUS. Additionally, design of the connection between the wall panel and the main structure is proposed. Findings may serve as a scientific reference for design of high performance composite sandwich wall panels.

Key Words
finite element analysis; modeling; simulation; ultra-high performance concrete; rock wool; sandwich wall panel; temperature; humidity

Address
Xiangguo Wu: College of Civil Engineering, Fuzhou University, Fuzhou, 350108, China; Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of the Industry and Information Technology, Harbin Institute of Technology, Harbin, 150090, China
Shiyuan Yu: Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of the Industry and Information Technology, Harbin Institute of Technology, Harbin, 150090, China
Xiaokun Tao: Hebei Construction Material Vocational & Technical College, Qinhuangdao, Heibei, 066004, China
Baochun Chen: College of Civil Engineering, Fuzhou University, Fuzhou, 350108, China
Hui Liu: Qinhuangdao Municipal Building Material Group Co., Ltd., Qinhuangdao, Heibei, 066000, China
Ming Yang: Hebei Construction Material Vocational & Technical College, Qinhuangdao, Heibei, 066004, China
Thomas H.-K. Kang: Department of Architecture & Architectural Engineering and Engineering Research Institute, Seoul National University, Seoul, 08826, Republic of Korea

Abstract
This study aims to establish a new methodological framework for the evaluation of the evolution of the reliability of plain concrete for pavement vs number of cycles under flexural fatigue loading. According to the framework, a new method calculating the reliability was proposed through probability simulation in order to describe a random accumulation of fatigue damage, which combines reliability theory, one-to-one probability density functions transformation technique, cumulative fatigue damage theory and Weibull distribution theory. Then the statistical analysis of flexural fatigue performance of cement concrete tested was carried out utilizing Weibull distribution. Ultimately, the reliability for the tested cement concrete was obtained by the proposed method. Results indicate that the stochastic evolution behavior of concrete materials under fatigue loading can be captured by the established framework. The flexural fatigue life data of concrete at different stress levels is well described utilizing the two-parameter Weibull distribution. The evolution of reliability for concrete materials tested in this study develops by three stages and may corresponds to develop stages of cracking. The proposed method may also be available for the analysis of degradation behaviors under non-fatigue conditions.

Key Words
pavement; cement concrete; fatigue damage; degradation reliability; Monte Carlo; Weibull distribution

Address
Yanshun Jia, Guoqiang Liu, Ying Gao, Tao Yang, Fanlong Tang: School of Transportation, Southeast University, Nanjing 211189, China
Yunmeng Yang: Richangsheng Design & Research Institute of Building New Materials Co., Ltd., Hangzhou 310002, China

Abstract
Studies have proved that the mechanical properties of concrete, suddenly is dropped off with employing waste materials as replacements. The effectiveness of fibre addition on the structural stability of concrete has been indicated in recent investigations. There are different waste aggregates and fibres as plastic, rubber tire, coconut, and other natural wastes, which have been evaluated throughout the last decades. The fibres incorporation has a substantial effect on the properties of concrete mix subjected to different loading scenarios. This paper has reviewed different types of wastes and the effect of typical fibres including Poly Ethylene Terephthalate (PET), rubber tire, and waste glass. Furthermore, waste plastic and waste rubber has been especially studied in this review. Although concretes containing PET fibre revealed a reduction in compressive strength at low fibre fractions, using PET is resulted to micro-cracking decrement and increasing flexibility and flexural strength. Finally, according to the reviews, the conventional waste fibres are well-suited to mitigated time-induced damages of concrete and waste fibres and aggregates could be a reliable replacement for concrete.

Key Words
recycled waste materials; rubber tire; waste plastic; waste rubber; Poly Ethylene Terephthalate

Address
Seyed Azim Hosseini: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran

Abstract
Microtubules buckle under bending and torsion and this property has been studied for free microtubules before using orthotropic elastic shell model. But as microtubules are embedded in other elastic filaments and it is experimentally showed that these elastic filaments affect the critical buckling moment and critical buckling torque of the microtubules. To prove that, we developed orthotropic Winkler like model and demonstrated that the critical buckling moment and critical buckling torque of the microtubules are orders of higher magnitude than those found for free microtubules. Our results show that Critical buckling moment is about 6.04 nNnm for which the corresponding curvature is about o=1.33 rad /um for embedded MTs, and critical buckling torque is 0.9 nNnm for the angle of 1.33 rad/um. Our results well proved the experimental findings.

Key Words
microtubule; orthotropic material; buckling; bending; torsion; winkler like model; orthotropic elastic shell model; wave propagation approach

Address
Muhammad Taj, Muhammad A. Afsar, Muhammad Safeer, Manzoor Ahmad: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Muzamal Hussain, Muhammad N. Naeem: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Noor Badshah: Department of Basic Science, University of Engineering and Technology, Peshawer
Arshad Khan: Institute of Computer Science and Information Technology, The University of Agriculture, Peshawar
Abdelouahed Tounsi: Materials and Hydrology Laboratory, Algeria Faculty of Technology Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleumand Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
Concrete dams are important structures due to retaining amount of water on their reservoir. So such kind of structures have to be designed against static and dynamic loads. Especially considering on critical importance against blasting threats and environmental safety, dams have to be examined according to the blast loads. This paper aims to investigate structural response of concrete gravity dams under blast loads. For the purpose Sar

Key Words
blast load; concrete gravity dam; explicit analysis; structural response; TNT explosive

Address
Baris Sevim and Ahmet Tugrul Toy: Department of Civil Engineering, Yildiz Technical University, Istanbul, Turkey

Abstract
The main aim of the current research is to investigate the flexural behavior of the reinforced concrete (RC) slabs strengthened with strain hardening cementitious composites (SHCC) experimentally and numerically. Seven RC slabs were prepared and tested under four-points loading test. One un-strengthened slab considered as control specimen while six RC slabs were strengthened with reinforced SHCC layers. The SHCC layers had different reinforcement ratios and different thicknesses. The results showed that the proposed strengthening techniques significantly increased the ultimate failure load and the ductility index up to 25% and 22%, respectively, compared to the control RC slab. Moreover, a three dimensional (3D) finite element model was proposed to analyze the strengthened RC slabs. It was found that the results of the proposed numerical model well agreed with the experimental responses. The validated numerical model used to study many parameters of the SHCC layer such as the reinforcement ratios and the different thicknesses. In addition, steel connectors were suggested to adjoin the concrete/SHCC interface to enhance the flexural performance of the strengthened RC slabs. It was noticed that using the SHCC layer with thickness over 40 mm changed the failure mode from the concrete cover separation to the SHCC layer debonding. Also, the steel connectors prevented the debonding failure pattern and enhanced both the ultimate failure load and the ductility index. Furthermore, a theoretical equation was proposed to predict the ultimate load of the tested RC slabs. The theoretical and experimental ultimate loads are seen to be in fairly good agreement.

Key Words
reinforced concrete; one way slab; strengthening; SHCC; ductility; finite element analysis; theoretical analysis

Address
Ali Basha, Sabry Fayed and Walid Mansour: Civil Engineering Department, Faculty of Engineering, Kafrelsheikh University, Box 33511, Kafrelsheikh, Egypt


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