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CONTENTS
Volume 11, Number 5, May 2021
 


Abstract
High deformable concrete (HDC) elements have compressive strength rates equal to conventional concrete and have got a high compressive strain at about 20% to 50%. These types of concrete elements as prefabricated parts have an abundance of applications in the construction industry which is the most used in the construction of tunnels in squeezing grounds, tunnel passwords from fault zones or swelling soils as soft supports. HDC elements after reaching to compressive yield stress, in nonlinear behavior have hardening combined with increasing strain and compressive strength. The main aim of this laboratory and numerical research is to construct concrete elements with the above properties so the compressive stress-strain behavior of different concrete elements with four categories of mix designs have been discussed and finally one of them has been defined as HDC element mix design. Furthermore, two columns with and without implementing of HDC elements have been made and stress-strain curves of them have been investigated experimentally. An analysis model is presented for columns using finite element method adopted by ABAQUS. The results obtained from the ABAQUS finite element method are compared with experimental data. The main comparison is made for stress-strain curve. The stress-strain curves from the finite element method agree well with experimental results. The results show that the dimension of the HDC samples is significant in the stress-strain behavior. The use of the element greatly increases energy absorption and ductility.

Key Words
high deformable concrete element; stress-strain behavior; finite element modeling

Address
Yasser Alilou Kesejini, Amir Bahramifar, Hassan Afshin and Mehrdad Emami Tabrizi: Faculty of Civil Engineering, Sahand University of Technology, New Sahand Town, Tabriz, P.B. 51335/1996, Iran

Abstract
The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO2 uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO2 uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO2 for the fabrication of precast concrete members has the potential to make precast concrete greener and more costeffective.

Key Words
Portland cement; carbonation; characterization; steam curing

Address
Seonhyeok Kim: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea
Issam T. Amr, Bandar A. Fadhel, Rami A. Bamagain, Ali S. Hunaidy: Carbon Management Division, Research & Development Center, Saudi Aramco, Dhahran 31311, Saudi Arabia
Solmoi Park: Department of Civil Engineering, Pukyong National University,45 Yongso-ro, Nam-gu, Busan 48513, South Korea
Joonho Seog, H.K. Lee: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea

Abstract
In this paper, a study of stability and health of a newly-built railway tunnel is presented. The field test was implemented to monitor the secondary lining due to the significant cracking behaviors influenced the stability and health of the tunnel structure. Surface strain gauges were installed for monitoring the status of crack openings, and the monitoring outputs demonstrated that the cracks were still in the developing stage. Additionally, adjacent tunnel and poor condition of surrounding rock were identified as the causes of the lining cracking by systematically characterizing the crack spatial distribution, tunnel site and surrounding rock conditions. Reconstruction of partial lining and reconstruction of the whole secondary lining were designed as the maintenance projects for different cracking regions based on the construction feasibility. For assessing the health conditions of the reinforced lining, embedded strain gauges were set up to continuously measure the strain and the internal force of the reconstructed structures. For the partially reconstructed lining, the outputs show the maximum tensile elongation is 0.018 mm during 227 days, which means the structure has no obvious deformation after maintenance. The one-year monitoring of fullsection was implemented in the other two completely reconstructed cross-sections by embedded strain gauge. The outputs show the reconstructed secondary lining has undertaken the pressure of surrounding rock with the time passing. According to the calculated compressive and tensile safety factors, the completely reconstructed lining has been in reliable and safe condition during the past year after reinforcement. It can conclude that the aforementioned maintenance projects can effectively ensure the stability and health of this tunnel.

Key Words
field test; secondary lining; cracks; maintenance; monitoring

Address
Yiding Zhao: College of Civil Engineering, Yancheng Institute of Technology, Xiwangdadaozhonglu 1, Yancheng 224051, China
Junsheng Yang: School of Civil Engineering, Central South University, Lushan South Road 932, Changsha 410075, China
Yongxing Zhang: National-Local Joint Laboratory of Engineering Technology for Long-term Performance enhancement of Bridges in Southern District, Changsha University of Science & Technology, Changsha 410114, Hunan, China; School of Civil Engineering, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, China
Zhou Yi: School of Civil Engineering, Southwest Jiaotong University, Xian Road 999, Chengdu 611756, China

Abstract
The behavior of headed bars in concrete is investigated through 108 pullout tests having an embedment depth of eight times the bar diameter in the M20 concrete mix. Headed bars are designed based on ASTM A970-16 and ACI 318-19 recommendations. The primary parameters used in this study are the steel bar diameter, the steel fibers percentage, and the head shapes. Three failure modes namely, Steel, Concrete-Blowout & Pull-Through failure have been observed. Based on loaddeflection curves which are plotted to investigate the bond capacity of headed bars, it is observed that the circular-headed bars have displayed the highest peak load. The comparative analysis shows the smaller differences in the ultimate bond strength between MC2010 (0.89-2.26 MPa) and EN 1992-1-1 (2.32 MPa) as compared to ACI-318-19 (11-22 MPa) which is due to the absence of embedment depth and peak load factor in MC2010 and EN 1992-1-1 respectively.

Key Words
bond; bond strength; headed bar; load-deflection curves; pull-out test; steel fibers

Address
Payal Sachdeva, A.B. Danie Roy and Naveen Kwatra: Department of Civil Engineering, Thapar Institute of Engineering and Technology (Deemed to be University), Patiala, India

Abstract
This paper investigates the optimal sensor placements and capabilities of this procedure for dynamic characteristics identification of arch dams. For this purpose, a prototype arch dam is constructed in laboratory conditions. Berke arch dam located on the Ceyhan River in city of Osmaniye is one of the highest arch dam constructed in Turkey is selected for field verification. The ambient vibration tests are conducted using initial candidate sensor locations at the beginning of the study. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to extract experimental dynamic characteristics. Then, measurements are repeated according to optimal sensor locations of the dams. These locations are specified using the Effective Independence Method. To determine the optimal sensor locations, the target mode shape matrices which are obtained from ambient vibration tests of the selected dam with a large number of accelerometers are used. The dynamic characteristics obtained from each ambient vibrations tests are compared with each other. It is concluded that the dynamic characteristics obtained from initial measurements and those obtained from a limited number of sensors are compatible with each other. This situation indicates that optimal sensor placements determined by the Effective Independence Method are useful for dynamic characteristics identification of arch dams.

Key Words
arch dams; dynamic characteristics; effective independence method; modal testing; optimal sensor placement

Address
Ahmet Can Altunisik: Karadeniz Technical University, Faculty of Engineering, Department of Civil Engineering, 61080, Trabzon, Turkey
Baris Sevim: Yildiz Technical University, Faculty of Civil Engineering, Department of Civil Engineering, 34220, İstanbul, Turkey
Fezayil Sunca and Fatih Yesevi Okur: Karadeniz Technical University, Faculty of Engineering, Department of Civil Engineering, 61080, Trabzon, Turkey

Abstract
The incorporation of non-biodegradable tyre waste in cement-based material has gained more interest towards sustainable construction these days. Crumb rubber (CR) from waste tyre is an alternative for sand replacement in low strength applications. Many researchers have studied CR cement-based materials produced by normal mixing (NM) method and reported a significant decrease in compressive strength due to CR. To compensate this strength loss, this research aims to study the innovative incorporation of CR in cement composite via the preplaced mixing (PM) method. In this investigation, cement composite was produced with NM and PM methods by replacing sand with 0%, 50%, and 100% CR by volume. The test results showed no significant difference in terms of densities of cement composite prepared with both mixing methods. However, cement composite prepared with PM method had lower strength reduction (about 10%) and lowered drying shrinkage (about 20%). In addition, the sound absorption coefficient and noise reduction coefficient of CR cement composite prepared by PM method were in similar range as those prepared with NM method. Overall, the results demonstrate that the PM method is promising, and the maximum replacement level of 50% is recommended for CR in the cement composite.

Key Words
crumb rubber; sustainability; cement composite; preplaced aggregate; mechanical properties; sound absorption

Address
Syed Nasir Shah:Centre for Innovative Construction Technology, Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Department of Civil Engineering, Faculty of Engineering, Balochistan University of Information Technology, Engineering, and Management Sciences, 87300 Quetta, Pakistan
Kim Hung Mo, Soon Poh Yap: Centre for Innovative Construction Technology, Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
Azma Putra, Muhammad Nur Othman: Centre for Advanced Research on Energy, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Malacca, Malaysia

Abstract
The pH of cement-based materials (CBMs) is an important factor for their durability, sustainability, and long service life. Currently, the use of supplementary cementitious materials (SCMs) is becoming mandatory due to economic, environmental, and sustainable issues. There is a decreasing trend in pH of CBMs due to incorporation of SCMs. The determination of numerical values of pH is very important for various low and high volume SCMs blended cement mortars for the better understanding of different defects and durability issues during their service life. In addition, the effect of cement hydration and pozzolanic reaction of SCMs on the pH should be determined at initial and later ages. In this study, the effect of low and high-volume fly ash (FA) and ground granulated ballast furnace slag (GGBFS) cement mortars in different curing conditions on their pH values has been determined. Thermal gravimetric analysis (TGA) was carried out to support the findings from pH measurements. In addition, thermal conductivity (k-value) and strength activity indices of these cement mortars were discussed. The results showed that pH values of all blended cement mortars were less than ordinary Portland cement (OPC) mortar in all curing conditions used. There was a decreasing tendency in pH of all mortars with passage of time. In addition, the pH of cement mortars was not only dependent on the quantity of Ca(OH)2. The effect of adding SCMs on the pH value of cement mortar should be monitored and measured for both short and long terms.

Key Words
Ca(OH)2 content; curing condition; durability; fly ash; GGBFS; k-value; pH; supplementary cementitious materials

Address
Payam Shafigh: Centre for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia
Sumra Yousuf: Department of Civil Engineering, Faculty of Engineering, Universiti of Malaya, 50603 Kuala Lumpur, Malaysia; Department of Building and Architectural Engineering, Faculty of Engineering & Technology, Bahauddin Zakariya University, 60000 Multan, Pakistan
Zainah Ibrahim: Department of Civil Engineering, Faculty of Engineering, Universiti of Malaya, 50603 Kuala Lumpur, Malaysia
Belal Alsubari: Department of Civil Engineering, Faculty of Engineering, Miami College of Henan University, Kaifeng, Henan, China
Iman Asadi: Centre for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia

Abstract
With regard to economic efficiency, composite fix beams are widely used to pass longitudinal shear forces across the interface. The current knowledge of the composite beam load-slip activity and shear capability are restricted to data from measurements of push-off. Modelling and analysis of the composite beams based on Euro-code 4 regarding to shear, bending, and deflection under differing loads were carried out using Finite Element through an efficient computer simulation and the final loading and sections capacity based on the failure modes was analysed. In bending, the section potential was increased by an improvement of the strength in both steel and concrete, but the flexural and compressive resistance growth is very weak (3.2% 3.1% and 3.0%), while the strength of the concrete has increased respectively from 25 N/mm2 to 30, 35, and 40 N/mm2 compared to the increment of steel strength by 27% and 21% when it was raised from 275 to 355 and 460 N/mm2, respectively. It was found that the final flexural load capacity of fix beams was declined with increase in the fix beam span for both three steel strength. The shear capacity of sections was remained unchanged at constant steel strength and different length, but raised with final yield strength increment of steel sections by 29%, and 67% when it was raised from 275 N/mm2 to 355 N/mm2 and 460 N/mm2, respectively.

Key Words
cold-formed steel; shear connector; composite slab; composite beam; bending fesistance

Address
Jinzhao Yin: Zhejiang Tongji Vocational College of Science and Technology, Hangzhou, 310000, China
Huizhi Tong: Zhejiang Tongji Vocational College of Science and Technology, Hangzhou, 310000, China
Morteza Gholizadeh: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Yousef Zandi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Abdellatif Selmi: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia; Ecole Nationale d'Ingenieurs deTunis (ENIT), Civil Engineering Laboratory, B.P. 37, Le belvedere1002, Tunis, Tunisia
Angel Roco-Videla: Programa Magister en Ciencias Químico-biológicas, Facultad de Ciencias de la Salud, Universidad Bernardo O'Higgins, Santiago, Chile; Departamento de Ingeniería Civil, Facultad de Ingeniería, Universidad Catolica de la Santisima Concepcion, Concepcion, Chile
Alibek Issakhov: Al-Farabi Kazakh National University, Almaty, Kazakhstan; Kazakh-British Technical University, Almaty, Kazakhstan


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