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CONTENTS
Volume 17, Number 1, January 2024
 

Abstract
Precast deck joints have problems due to the occurrence of additional processes at construction sites, the complexity of construction, and the lack of design and construction standards for precast deck joints. To solve these, this study proposes a new precast deck joint that uses an Ultra-High-Performance Fiber-reinforced Cement Composite (UHPFRCC) filling material containing steel fibers and a straight rebar joint. In addition, the structural performance of the proposed joint, based on various parameters, was compared to that of existing precast deck joints, and the proposed joint showed equivalent strength and ductility. Therefore, the proposed joint can solve construction site problems by replacing the existing ones. The influence of various variables is expected to provide basic data on the design and construction guidelines for the precast deck joints.

Key Words
design and construction guidelines; ductility; precast deck joint methods; strength; structural performance

Address
(1) Woo-Young Go, Myoung-Sung Choi:
Department of Civil and Environmental Engineering, Dankook University, Yongin, Republic of Korea;
(2) Han-Joo Lee, Young-Jin Kim:
Korea Concrete Research Center Institute, Seoul, Republic of Korea.

Abstract
Due to its capacity to address urgent environmental challenges connected to urbanization and stormwater management, pervious concrete, a sustainable and innovative material, has attracted a lot of attention recently. The aim of this study was to find the engineering characteristics of pervious concrete made from recycled aggregate (RA) at various aggregateto-cement ratios (A/C) and the addition of 5% (by weight of total aggregate) of both natural and recycled fine aggregate to produce a very sustainable concrete product for a variety of applications. The three distinct aggregate-to-cement ratios, 6, 5, and 4, were used to produce pervious concrete using recycled aggregate in the research approach. The ratio of water to cement (w/c) was maintained at 0.3. Pervious concrete was created using single-sized recycled aggregate that passed through a 12.5 mm sieve and was held on a 9.5 mm sieve, as well as natural and recycled sand that passed through a 4 mm sieve. The production of twelve distinct concrete mixtures resulted in the testing of each concrete sample for dry density, abrasion resistance, compressive and splitting tensile strengths, porosity, and water permeability. A statistical method called GLM-ANOVA was also used to assess the characteristics of pervious concrete made using recycled aggregate. According to the experimental results, lowering the aggregate-to-cement ratio enhances the pervious concrete's overall performance. Additionally, a modest amount of fine aggregate boosts mechanical strength while lowering void content and water permeability. However, it was noted that such concretes' mechanical qualities were adversely affected to some extent. The results of this study offer insight into the viability of using recycled aggregates in order to achieve both structural integrity and environmental friendliness, which helps to optimize pervious concrete compositions.

Key Words
abrasion resistance; compressive and splitting tensile strength; pervious concrete; porosity; recycled aggregate and sand; water permeability

Address
(1) Briar K. Esmail:
Department of Civil Engineering, Faculty of Engineering, Koya University, Koya, Iraq;
(2) Briar K. Esmail:
ISISE, Department of Civil engineering, University of Minho, Guimarães, Portugal;
(3) Najmadeen M. Saeed, Soran R. Manguri:
Civil Engineering Department, University of Raparin, Ranya, Iraq;
(4) Najmadeen M. Saeed:
Civil Engineering Department, Faculty of Engineering, Tishk International University, Erbil, Iraq;
(5) Mustafa Günal:
Civil Engineering Department, Gaziantep University, Gaziantep, Türkiye.

Abstract
Reinforced concrete (RC) flat slabs should be designed based on punching shear strength. As part of this study, machine learning (ML) algorithms were developed to accurately predict the punching shear strength of RC flat slabs without shear reinforcement. It is based on Bayesian optimization (BO), combined with four standard algorithms (Support vector regression, Decision trees, Random forests, Extreme gradient boosting) on 446 datasets that contain six design parameters. Furthermore, an analysis of feature importance is carried out by Shapley additive explanation (SHAP), in order to quantify the effect of design parameters on punching shear strength. According to the results, the BO method produces high prediction accuracy by selecting the optimal hyperparameters for each model. With R2 = 0.985, MAE = 0.0155 MN, RMSE = 0.0244 MN, the BO-XGBoost model performed better than the original XGBoost prediction, which had R2 = 0.917, MAE = 0.064 MN, RMSE = 0.121 MN in total dataset. Additionally, recommendations are provided on how to select factors that will influence punching shear resistance of RC flat slabs without shear reinforcement.

Key Words
Bayesian optimization; flat slabs; machine learning; punching shear strength

Address
(1) Huajun Yan, Nan Xie:
School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China;
(2) Dandan Shen:
SANY Heavy Industry Co., LTD, Beijing, 100044, China.

Abstract
In this paper, boundary layer flow is observed through stretching cylinder exponentially with non-linear velocity. This cylinder is rested in porous medium. Appropriate similarity transformation is employed for the conversion of governing PDEs into ODEs. To compute the problem and solution series numerical method is applied and evaluated by using finite difference Keller-Box method. The velocity ratio, permeability parameter, Reynold number is figure out to examine the effect of on velocity profile. Fluid velocity and skin friction coefficient goes down with increment of Reynold number and permeability parameter. While reverse behavior is reported for velocity ratio. The results are validated with earlier investigations and found very well.

Key Words
exponential stretching cylinder; Keller-Box Method; numerical analysis; porous medium; shooting technique; viscous fluid

Address
(1) Mohamed Amine Khadimallah, Elimam Ali:
Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia;
(2) Mudassar Jalil:
Department of Mathematics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, 44000 Islamabad, Pakistan;
(3) Muzamal Hussain:
Department of Mathematics, University of Sahiwal, Sahiwal, 57000, Punjab, Pakistan.

Abstract
In this study, the fresh properties of paraffin-mixed concrete, compressive strength, resistance to frost damage, and resistance to composite deterioration under freeze-thaw and salt environment were investigated. The compressive strength of paraffin-mixed concrete was almost the same as that of unmixed concrete, and no decrease in strength was observed, unlike the concrete with entrained air in consideration of freeze-thaw resistance. Concerning the freeze-thaw resistance of paraffin-mixed concrete, the relative dynamic modulus of elasticity (RDME) did not decrease even without entrained air. In addition, no decrease in the RDME was observed in the combined deterioration with salt damage, and it was confirmed that the mass reduction was suppressed compared to the concrete without paraffin. The freeze-thaw resistance of concrete when paraffin is mixed may be improved due to the reduction in the amount of frozen water and the mixed paraffin particles exist in the concrete as pore fillers with a size of 200 μm or less, which act as substitutes for air voids. This resulted in reduction of the apparent air void spacing and thereby relieving the pore pressure.

Key Words
dynamic modulus; freeze-thaw; paraffin; pore structure; salt damage; scaling

Address
Department of Civil Engineering, Fukuoka University, Jonan ku, Nanakuma 8-19-1, Fukuoka 814-0180, Japan.


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