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Volume 14, Number 6, December 2022

In this study, outdoor exposure tests were performed for fly ash concrete considering long-term marine exposures and mix conditions. Different fly ash substitution ratios, water-binder ratios, regional exposure conditions, and exposure periods were considered. As the exposure period increased, the effect of the water.binder ratio on the apparent chloride diffusion coefficient decreased due to reduced chloride ingress. The increase in the diffusion coefficient with the water.binder ratio in concrete with ordinary portland cement was higher than that in fly ash concrete cement. Relationships between the apparent diffusion coefficient and RCPT (Rapid Chloride Penetration Test: passed ion charge) based on mix proportions were proposed with three regional exposure conditions.

Key Words
apparent chloride diffusion coefficient; chloride ingress; fly ash; marine exposure test

(1) Yong-Sik Yoon, Seung-Jun Kwon:
Department of Civil and Environmental Engineering, Hannam University, 70 Hannam-ro, Daedeok-gu, Daejeon 34430, Republic of Korea;
(2) Jong-Suk Lee, Ji-Young Min:
Department of Structural Engineering Research, Korea Institute of Civil engineering and Building Technology, Goyang 10233, Republic of Korea.

The present functionally graded cylindrical shell problem is shaped by taking into consideration the strain and kinetic energies of a vibrating cylindrical shell and is in the integral form. Calculus of variations is employed to change the integral expressions into the PDEs. This generates three differential equations in three unknown deformation displacement functions. The radial deflection is restrained by ring supports. This factor is expressed by the polynomial functions which carry the degree equal to the number of ring supports. The axial modal dependence is measured by characteristic beam functions which guarantee to fulfill edge conditions fixed both ends of a cylindrical shell. Energy variational approaches are widely exploited to research vibration cylindrical shells of cylindrical shells. The Galerkin technique is chosen to solve the present shell and the vibration shell frequency is attained in the eigenvalue form. The thickness is controlled with trigonometric fraction law. The behavior of various exponent of trigonometric function are observed with ring supports. The programming is performed in MATLAB software to study shell vibration characteristics. Results are shown in tabular forms. Their authenticity is verified by comparing them with other ones found in the literature.

Key Words
bi-layered; functionally graded layers; natural frequencies; ring support; wave equation

(1) Amjad Qazaq, Mohammed Mujalli:
Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia;
(2) Muzamal Hussain:
Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan;
(3) Abdelouahed Tounsi:
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
(4) Abdelouahed Tounsi:
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia.

With the aim to alleviate the influence of mesh grid on numerical results, a coupled 2D RBSM-Voronoi model is proposed in this paper to simulate the fracture process of plain concrete components. In the proposed model, voronoi diagram is introduced to generate random grid, and concrete is partitioned into a series of voronoi cells, which are regarded as rigid blocks. The adjacent cells can separate and intrude at the interface, which make the proposed model a convenient tool to simulate the propagation of cracks. A pair of uniform springs are defined at the interface of adjacent cells, and the constitutive model based on traction-separation criterion is proposed and modified to define the weaken behavior of interface spring. To identify the application and accuracy of the proposed model, numerical studies about concrete components are conducted and compared with experimental results. According to the comparison results, it can be concluded that the coupled RBSM-voronoi model is an efficient and accurate method to analyze the fracture process of concrete components, especially for the components under compression shear loading, and the random voronoi grid can greatly alleviate the sensitivity of mesh grid on numerical results.

Key Words
concrete; cracks; fracture behavior; rigid body spring model; voronoi diagramr

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.

Most failure modes in flat slabs are punch failure. However, in practice, there are many instances where punching failure is preceded by bending failure, or the actual failure mode is bending-punching failure. In order to obtain the reasonable result of bending failure, an accurate method is proposed to estimate the flexural capacity of slab–special-shaped column (cruciform, L-shaped, T-shaped) connections based on the yield-line theory, and the theoretical model is verified by comparing with the collected experimental results. In addition, the influence of column section shape and column limb length to thickness ratio (c2/c1) on the bearing capacity was discussed. The results show that the column section shape has an effect on the bending capacity of slab–column connection, but the effect was not significant. At the same time, the column limb length to thickness ratio (c2/c1) has little effect on the bending capacity, which can be ignored.

Key Words
bending failure; failure load; slab-column connections; special-shaped column; yield-line theory

(1) Wei Zhang, Jianyang Xue, Baoxin Li, Jinghui Wei:
School of Civil Engineering, Xi'an University of Architecture & Technology, Xi*$39;an 710055, China;
(2) Jinjun Xu:
College of Civil Engineering, Nanjing Tech University, Nanjing, 211816, China.

The present study evaluates various techniques for flexural strengthening of slabs by bonding carbon fiberreinforced polymer (CFRP) sheets and then develops a new bonding method called externally bonded reinforcement and mechanically fastened by nailing (EBR-MFN). A total of 18 unreinforced unidirectional concrete slabs with the dimensions of 500

Key Words
Carbon-Fiber Reinforced Polymer (CFRP); concrete slabs; debonding; Externally Bonded Reinforcement (EBR); flexural strengthening; mechanically fastened methods

(1) Mohammad H. Ghadiri Rad, Majid Kazemi:
Civil Engineering Department, Quchan University of Technology, Quchan, Iran;
(2) Mohammad M. Nayeban:
Civil Engineering Department, Atrak University of Technology, Quchan, Iran.

In recent years, the use of various industrial by-products and waste materials in concrete has attracted the attention of researchers around the globe to reduce their impact on the environment and to find sustainable solution to conserve natural resources. The use of end-of- life tires of vehicles in concrete is one such example. This research study investigates fresh and hardened properties, and bond stress-slip behavior of self-compacting rubberized concrete with and without silica fume. RILEM-FIP-CEB beam testing arrangement was employed to perform bond tests. The first part of the study focused on the development of self-compacting rubberized concrete (SCRC) with and without silica fume (SF) and investigating its fresh and hardened properties (compressive and tensile strengths). The second part focused on investigating bond stress-slip behavior of SCRC with different percentages of Crumb Rubber (CR) varying from 5% up to 30% as sand replacement by volume. Total 12 concrete mixes were prepared for this study. The experimental results showed that the replacement of sand with CR has negative effect on the fresh and hardened properties of SCRC. The bond strength was found to be decreased by 38% with 30% replacement of sand with CR. Further, presence of CR in the concrete mix caused detrimental effect on the bond stiffness and toughness. However, SF improved the mechanical properties and bond strength of SCRCs. This study found that replacement of sand with 10% CR by volume and addition of SF in concrete resulted in similar mechanical properties and bond strength as that of normal self-compacting concrete which demonstrates the potential use of SCRC in structural applications.

Key Words
bond stress-slip response; crumb rubber; fresh & hardened properties; SCC; silica fume

(1) Muhammad Usman:
Deputy Secretary Development, Punjab Irrigation Department, Government of the Punjab, Pakistan;
(2) Syed Asad Ali Gillani, Rashid Hameed, Muhammad Rizwan Riaz:
Department of Civil Engineering, University of Engineering and Technology Lahore, Lahore 54890, Pakistan;
(3) Muhammad Ilyas:
Department of Civil Engineering, Lahore Leads University, Lahore, Pakistan;
(4) Ahmed Farouk Deifalla:
Structural Engineering Department, Faculty of Engineering and Technology, Future University in Egypt New Cairo 11835, Egypt.

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