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CONTENTS
Volume 10, Number 6, December 2020
 


Abstract
Multiple mathematical modeling for prediction of slump, compressive strength and depth of water penetration at 28 days were performed using statistical analysis for the concrete containing waste limestone powder as partial replacement of sand obtained from experimental program reported in this research. To extract experimental data, 180 concrete cubic samples with 20 different mix designs were investigated. The twenty non-linear regression models were used to predict each of the concrete properties including slump, compressive strength and water depth penetration of concrete with waste limestone powder. Evaluation of the models using numerical methods showed that the majority of models give acceptable prediction with a high accuracy and trivial error rates. The 15-term regression models for predicting the slump, compressive strength and water depth were found to have the best agreement with the tested concrete specimens.

Key Words
concrete; limestone powder; slump; compressive strength; water penetration; prediction

Address
Aryan Bazrafkan: Department of Civil Engineering, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran
Alireza Habibi: Department of Civil Engineering, Shahed University, Tehran, Iran
Arash Sayari: Department of Civil Engineering, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

Abstract
The experimental and numerical works were carried out on high performance fiber reinforced concrete (HPFRC) with w/cm ratios ranging from 0.25 to 0.40, fiber volume fraction (Vf)=0-1.5% and 10% silica fume replacement. Improvements in compressive and flexural strengths obtained for HPFRC are moderate and significant, respectively, Empirical equations developed for the compressive strength and flexural strength of HPFRC as a function of fiber volume fraction. A relation between flexural strength and compressive strength of HPFRC with R=0.78 was developed. Due to the complex mix proportions and non-linear relationship between the mix proportions and properties, models with reliable predictive capabilities are not developed and also research on HPFRC was empirical. In this paper due to the inadequacy of present method, a back propagation-neural network (BP-NN) was employed to estimate the 28-day compressive strength of HPFRC mixes. BP-NN model was built to implement the highly non-linear relationship between the mix proportions and their properties. This paper describes the data sets collected, training of ANNs and comparison of the experimental results obtained for various mixtures. On statistical analyses of collected data, a multiple linear regression (MLR) model with R2=0.78 was developed for the prediction of compressive strength of HPFRC mixes, and average absolute error (AAE) obtained is 6.5%. On validation of the data sets by NNs, the error range was within 2% of the actual values. ANN model has given the significant degree of accuracy and reliability compared to the MLR model. ANN approach can be effectively used to estimate the 28-day compressive strength of fibrous concrete mixes and is practical.

Key Words
high performance steel fiber reinforced concrete; silica fume; compressive strength; flexural strength; statistical model; neural networks; prediction; validation

Address
Ramadoss Perumal: Department of Civil Engineering, Pondicherry Engineering College, Puducherry-605 014, India
V. Prabakaran: Department of Civil Engineering, Pondicherry Engineering College, Puducherry, India

Abstract
This paper investigates mechanical properties of roller compacted concrete (RCC) involving reclaimed asphalt pavement (RAP). In this way, a set of 276 cylindrical RCC specimens were prepared with different RAP sizes (i.e., fine, coarse & total) at various ratios (i.e., 10%, 20%, and 40%). Results reveal that incorporation of RAP decreases unconfined compressive strength (UCS), modulus of elasticity (E), and indirect tensile (IDT) strength of RCC. For each RAP size, a regression model was used to maximize RAP content while satisfying the UCS lower limit (27.6 Mpa) mentioned by ACI as a minimum requirement for RCC used in pavement construction. Moreover, UCS of RAP incorporated mixes, dissimilar to that of control mixes, was found to be sensitive and insensitive to the testing temperature and curing time after 7 days, respectively. The results also demonstrate that the higher amounts of RAP, the more flexibility in RCC is. This issue was also proved by the results of modulus of elasticity test. In addition, the toughness index (TI) shows that increase in RAP content leads to up to 43% increase in energy absorbance capacity of RCC.

Key Words
RCC; RAP; UCS; IDT; modulus of elasticity; toughness index

Address
Amin Ahmadi: Technology and Engineering Department, Shahrekord University, Shahrekord, Iran
Mohammad K. Gogheri: Department of Civil Engineering, Tarbiat Modares University, Tehran, Iran
Mostafa Adresi: Civil Engineering Department, Shahid Rajaee Teacher Training University, Tehran, Iran
Ershad Amoosoltani: School of Civil Engineering, KN Toosi University, Tehran, Iran



Abstract
In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

Key Words
clamped-free; Kelvin's theory; natural frequency; edge condition; functionally graded

Address
Mohamed A. Khadimallah: College of Engineering, Civil Engineering Department, Prince Sattam Bin Abdulaziz University, BP 655, Al-Kharj, 16273, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Imene Harbaoui: Laboratory of Applied Mechanics and Engineering LR-MAI, University Tunis EI Manar-ENIT BP37- Le belvedere, 1002, Tunis

Abstract
In the preliminary design phase of explosion-proof structures, the use of P-I diagram is useful. Based on the fact that the deformation criteria at failure or heavy damage is significantly larger than the yield deformation, a closed form solution of normalized P-I diagram is proposed using the complete plastic resistance curve. When actual sizes and material properties of RC structural component are considered, the complete plasticity assumption shows only a maximum error of 6% in terms of strain energy, and a maximum difference of 9% of the amount of explosives in CWSD. Thru comparison with four field test results, the same damage pattern was predicted in all four specimens.

Key Words
explosion; P-I diagram; closed form solution; support rotation angle

Address
Jung Hun Kee and Jong Yil Park: Department of Safety Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea

Abstract
Cold-mixed asphalt mixture is a widely recommended asphalt pavement materials with potentially economic and environmental benefits. Due to the reduction of natural non-renewable mineral resources, powder minerals with similar properties are considered as new mineral fillers in asphalt mixtures. This study explored the feasibility of using cement to replace natural limestone powder (LP) in emulsified asphalt concrete modified by styrene-butadiene styrene copolymer. The experimental tests, including compressive strength, Marshall stability as well as moisture susceptibility test, were used to investigate the mechanical properties, the Marshall stability, flow value, as well as the moisture damage. In addition, the influence of material composition on the performance of asphalt concrete is explained by the microstructure evolution of the pore structure, the interface transition zone (ITZ), and the micromorphology. Due to mineralogical reactivity of cement, its replacement part of LP improved the mechanical properties, Marshall stability, but it will reduce the moisture susceptibility and flow value. This is because with the increase of the cement substitution rate, the pore structure of the asphalt concrete is refined, the width of ITZ becomes smaller, and the microstructure is more compact. In addition, asphalt concrete with a larger nominal particle size (AC-16) has relatively better performance.

Key Words
asphalt concrete; cement filler; emulsified asphalt; gradation design; microstructure characterization

Address
Baoju Liu, Xiang Wu, Jinyan Shi, Xiaolong Wu, Junyi Jiang and Jiali Qin: School of Civil Engineering, Central South University, Changsha 410075, China

Abstract
In this study, a process is proposed to calculate analytical correction values for the vertical shortening of all columns on all floors in a high-rise building that minimizes the error between the structural analysis predictions and values measured during construction. The weight ratio and the most probable value were accordingly considered based on the properties of the shortening value analyzed at several points in each construction stage and the distance between these measured points and unmeasured points at which the shortening was predicted. The effective range and shortening value normalization were considered using the column grouping concept. These tools were applied to calculate the error ratio between the predicted and measured values on a floor where a measured point exists, and then determine the estimated error ratio and estimated error value for the unmeasured point using this error ratio. At points on a floor where no measured point exists, the estimated error ratio and the estimated error value were calculated by applying the most probable value considering the weight ratio for the nearest floor where measured points exist. In this manner, the error values and estimated error values can be determined at all points in a structure. Then, the analytical correction value, defined as this error or estimated error value, was applied by adding it to the predicted value. Finally, the adequacy of the proposed correction method was verified against measurements by applying the analytical corrections to all unmeasured points based on the points where the measurement exists.

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

Address
Eun-seok Song and Jae-yo Kim: Department of Architectural Engineering, KwangWoon University, 01897, Republic of Korea

Abstract
Exterior walls in buildings are exposed to various forms of thermal loads, which depend on the positions of walls. Therefore, one of the efficient methods for improving the energy competence of buildings is improving the thermal properties of insulation plaster mortar. In this study, lightweight fine aggregate (LWFA) and micro rubber ash (MRA) from recycled tires were used as partial replacements for sand. The flow ability, unit weight, compressive strength, tensile strength, thermal conductivity (K-value), drying shrinkage and microstructure scan of lightweight rubberized mortar (LWRM) were investigated. Ten mixtures of LWRM were prepared as follows: traditional cement mortar (control mixture); three mixes with different percentages of LWFA (25%, 50% and 75%); three mixes with different percentages of MRA (2.5%, 5% and 7.5%); and three mixes consisting both types with determined ratios (25% LWFA+5% MRA, 50% LWFA+5% MRA and 75% LWFA+5% MRA). The flow ability of the mortars was 22+-2 cm, and LWRM contained LWFA and MRA. The compressive and tensile strength decreased by approximately 64% and 57%, respectively, when 75% LWFA was used compared with those when the control mix was used. The compressive and tensile strength decreased when 5% MRA was used. By contrast, mixes with determined ratios of LWFA and MRA affected reduced unit weight, K-value and dry shrinkage.

Key Words
lightweight; rubber; mortar; thermal conductivity; shrinkage

Address
Omar Mohamed Omar Ibrahim: Department of Civil Construction and Architecture, Faculty of Technology and Education, Suez University, Suez, Egypt; Higher Institute for Engineering and Technology At ElManzala, Ad Daqahliyah, Egypt
Bassam A. Tayeh: Civil Engineering Department, Faculty of Engineering, Islamic University of Gaza, Gaza, Palestine

Abstract
This paper presents one of the demonstration projects undertaken during the FP7 EU-funded Anagennisi project (Innovative reuse of all tyre components in concrete-2014-2017) on a full-scale (30 mx40 m, thickness: 0.2 m) Steel Fibre Reinforced Concrete (SFRC) slab-on-grade using a blend of manufactured steel fibres (MSF) and Recycled Tyre Steel Fibres (RTSF). The aim of the project was to assess the use of RTSF in everyday construction practice. The Anagennisi partners, Dulex Ltd in collaboration with Gradmont-Gradacac Ltd and University of Zagreb, designed, cast and monitored the long-term shrinkage deformations of the indoor slab-on-grade slab at Gradmont's precast concrete factory in Gradacac, Bosnia and Herzegovina. A hybrid RTSF mix (20 kg/m3 of MSF+10 kg/m3 of RTSF) was used to comply with the design criteria which included a maximum load capacity of 20 kN/m2. The slab was monitored for one year using surveying equipment and visual inspection of cracks. During the monitoring period, the slab exhibited reasonable deformations (a maximum displacement of 3.3 mm for both, horizontal and vertical displacements) whilst after five years in use, the owners did not report any issues and were satisfied with the construction methodology and materials used. This work confirms that RSTF is a viable and sustainable solution for slab-on-grade applications.

Key Words
slab-on-grade; long-term monitoring; hybrid fibre reinforced concrete

Address
Ana Baricevic, Martina Grubor: Faculty of Civil Engineering, University of Zagreb, Kaciceva 26, Zagreb, Croatia
Rinaldo Paar: Faculty of Geodesy, University of Zagreb, Kaciceva 26, Zagreb, Croatia
Panos Papastergiou, Kypros Pilakoutas, Maurizio Guadagnini: Department of Civil and Structural Engineering, The University of Sheffield, Sir Frederick Mappin Building, Mappin Street, Sheffield, S1 3JD, UK

Abstract
This study aimed to inspect the axial compression mechanical performance of basalt-fiber-reinforced recycled - concrete (BFRRC)-filled square steel tubular stub column. The replacement ratio of recycled coarse aggregate (RCA) and the basalt fiber (BF) dosage were used as variation parameters, and the axial compression performance tests of 15 BFRRC-filled square steel tubular stub column specimens were conducted. The failure mode and the load-displacement/strain curve of the specimen were measured. The working process of the BFRRC-filled square steel tubular stub column was divided into three stages, namely, elastic-elastoplasticity, sudden drawdown, and plasticity. The influence of the design parameters on the peak bearing capacity, energy dissipation performance, and other axial compression performance indexes was discussed. A mathematical model of segmental stiffness degradation was proposed on the basis of the degradation law of combined secantstiffness under axial compression. The full-process curve equation of axial compressive stress-strain was proposed by introducing the influencing factors, including the RCA replacement ratio and the BF dosage, and the calculated curve agreed well with the test-measured curve.

Key Words
basalt fiber-reinforced recycled concrete-filled square steel tube; stub column; recycled coarse aggregate replacement ratio; basalt fiber dosage; axial bearing performance; full-curve of stress-strain

Address
Xianggang Zhang: School of Urban Construction, Wuchang University of Technology, Wuhan 430223, China; School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
Xiang Gao, Xingguo Wang, Fang Wang: School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
Ercong Meng: CET-College of Engineering and Technology, Southwest University, Chongqing, China


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