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Volume 14, Number 4, October 2022

Thermally caused stress in silos have the potential to become critical in some cases. Therefore, most codes and standards require that silos are designed to resist thermal stress due to thermal differentials between stored material and the silo structure. However, very few of them include explicit requirements concerning the design of the silos in effectively combatting thermal effects. The research presented here disseminates thermal effects on reinforced concrete ground-supported cylindrical silos, which has received little attention to date. A three-dimensional numerical model, taking into account bulk material-silo wall interaction, was performed with the ANSYS commercial program, which is based on the finite element method, to evaluate the distribution and the magnitudes of bulk material pressure in the silos under thermal effects. The results of a parametric study, which examines the effects of varying aspect ratios, wall thicknesses and wall friction angles on the thermal response of reinforced-concrete cylindrical silos, is presented and the results from the numerical method are compared with the findings obtained via EN 1991-4. The finite element analysis revealed that the computed thermal material pressure is smaller than the design pressure obtained via EN1991-4 over a wide range of aspect ratios, suggesting that the design process is particularly conservative. Additionally, results reveal that in contrast to both wall thickness and wall friction angle, the aspect ratio may significantly affect the magnitudes of the responses of the reinforced concrete cylindrical silos under thermal effects.

Key Words
EN1991-4; numerical analysis; reinforced concrete silos; thermal response

Department of Civil Engineering, Karadeniz Technical University,61080, Trabzon, Turkey.

This study investigates the performance of unperforated cenosphere (CS) as internal curing (IC) agent without removing the glass-crystalline film from the CS surface. In this study, fly ash-based cement mortars were prepared by incorporating 0-20% CS as cement replacement. To evaluate the efficiency of CS as an IC agent, various properties of CS and CS-incorporated mortars were studied. These properties include mercury intrusion porosimetry, absorption/desorption capacity, compressive strength, microstructural analysis, and X-ray diffraction analysis. The results revealed that unperforated CS can also be used as an IC agent without further processing (i.e., removal of the glass-crystalline film).

Key Words
cenosphere; chemical etching; fly ash-cement mortars; internal curing agent; unperforated

(1) Aamar Danish:
Ingram School of Engineering, Texas State University, San Marcos, TX-78666, USA;
(2) Mohammad Ali Mosaberpanah:
Civil Engineering Department, Cyprus International University, North Cyprus, Turkey.

Accurately reflecting the construction process at the site in the construction sequence analysis for predicting the amount of vertical shortening is difficult. To increase the prediction accuracy, a method of calculating rational analytical correction values for all floors and column lines with limited measurement data was proposed. In this study, the analytical correction method based on measurement results for column shortening was verified by the measurement data in the actual building, and the effect of analytical correction was analyzed. While analyzing the effect of the analytical correction of the actual measurement model, it was confirmed that the prediction can be improved by comparing the error reduction in the completion stage and applying the measurement data in the intermediate stage of the construction sequence analysis. In addition, it was judged that the effect of the correction increases as it approaches the completion stage.

Key Words
analytical correction; column shortening; construction sequence analysis; high-rise building; measurement

Department of Architectural Engineering, KwangWoon University, 01897, Republic of Korea.

Lightweight aggregate concrete is a highly durable material that enables cost savings via weight reduction. This material has been continuously improved by researchers and engineers, leading to a high demand for research on lightweight aggregate concrete's basic properties. This study conducts three-point bending tests and analyzes the tensile properties of lightweight aggregate concrete load—crack mouth opening displacement and load.deflection curves. A trilinear tensile softening curve was used to identify the tensile properties of material. The necessary parameters are derived by conducting inverse analysis through the ant colony optimization (ACO) method. The intraclass correlation coefficient of less than 0.01 sufficiently confirmed the reliability of inverse analysis, allowing us to obtain the fracture energy. It was proposed both physical properties of lightweight aggregate concrete and a fracture energy prediction equation that uses the ligament depth and width of the specimen as parameters. In this prediction equation, the experimental results are well predicted with a standard deviation of 0.107 and a coefficient of variation of 0.105 by determining the experimental constants using the existing 85 experimental data of lightweight aggregate concrete.

Key Words
ACO; fracture energy; inverse analysis; lightweight aggregate concrete; optimization

(1) Jinsup Kim, Minho Kwon:
Department of Civil Engineering, Gyeongsang National University, Jinju, 52828, South Korea;
(2) Hyunsu Seo:
Institute of Technology Team, Daon Co., LTD, 20, Nodae-gil, Hwasun-eup, Hwasun-gun, 58125, South Korea;
(3) Suchart Limkatanyu:
Department of Civil Engineering, Prince of Songkla University, Songkla, Thailand.

In this study, seventeen PVC-FRP confined Concrete (PFCC) column-beam joints including eight PFCC column - enlarged ring beam (ERB) joints and nine PFCC column-beam joints strengthened with Core Steel Tube (CST) are designed and tested. The failure modes, ultimate load capacity, deformation capacity of two different types of joints is compared and analyzed. The test results demonstrate that the failure processes of two different types of joints are basically similar, experiencing the elastic, crack development, yield and failure phases. Comparatively, the PFCC column-ERB joints enter the yield phase relatively earlier than the joints strengthened with CST. Both of the connection configurations can effectively constraint the concrete at the joints and significantly improve load capacity, showing their respective advantages. From the point of view of improving the connection efficiency of the joints, increasing ring beam width has the most obvious effect on the PFCC column-ERB joints, while reasonably reducing the height of joint has the greatest influence on the joints strengthened with CST. The axial equivalent ultimate strains of these two different types of joints are much higher than the ultimate compressive strains of ordinary concrete, indicating that both of the connection configurations can remarkably enhance the deformation capacity of the joints. By comparison, the deformation resistances of the PFCC column-ERB joints are greater than those of the joints strengthened with CST. In addition, taking into account the scale effect, a comprehensive influence coefficient of the joints is introduced, and a unified formula for estimating the axial load capacities of the two different joints is proposed based on a modified superposition approach and validates the test data of this paper and other references with good agreement.

Key Words
beam-column joint; failure mode; load capacity; PVC-FRP confined concrete; unified formula

(1) Yuan Fang, Feng Yu, Yuandi Qian, Zekang Song, Defeng Zhu, Dongang Li:
Department of Civil Engineering and Architecture, Anhui University of Technology, Ma' anshan 243032, Anhui Province, China;
(2) Yuandi Qian:
Technology Center, China MCC17 Group Co. Ltd., Ma' anshan 243000, Anhui Province, China;
(3) Rui Bai:
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 999077, China.

In this paper, the frequency behavior of armchair single walled carbon nanotubes is explored for the influence of length-radius ratio based on Euler beam theory. This continuum model is used to determine the frequencies under clampedclamped and clamped-free edge conditions. It is investigated that the frequency pattern is higher for higher indices of armchair single walled carbon nanotubes. For these two boundary conditions, the frequencies of clamped boundary condition are almost higher than the other condition. As frequencies deceases fastly for initial values of length-to-radius ratio. After that the frequency decreases and behaves moderately and linearly. The frequencies are shown in GHz throughout the study. The outcomes of results from computer software MATLAB are tested with other computational techniques and found valid.

Key Words
clamped-free; GHz frequencies; natural frequency; single walled carbon nanotubes

(1) Muzamal Hussain:
Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan;
(2) Ahmed Obaid M. Alzahrani:
Physics Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia;
(3) Ahmed Obaid M. Alzahrani:
Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia;
(4) Mohamed A. Khadimallah:
Prince Sattam Bin Abdulaziz University, College of Engineering, Civil Engineering Department, BP 655, Al-Kharj, 11942, Saudi Arabia;
(5) Sami Alghamdi:
Electrical and Computer Engineering Department King Abdulaziz University, Jeddah, Saudi Arabia;
(6) Alireza Fatahi-Vajari:
Department of Mechanical Engineering, Shahryar Branch, Islamic Azad University, Shahryar, Iran;
(7) Abdelouahed Tounsi:
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
(8) Abdelouahed Tounsi:
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia.

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