Application of Adaptive Neuro-Fuzzy Inference System in High Strength Concrete

Adaptive Neuro-Fuzzy Inference System is growing to predict nonlinear behaviour of construction materials. However due to wide variety of parameters in this type of artificial intelligent machine, selecting the proper optimization methods together with the best fitting membership functions strongly affect the accuracy of prediction. In this study the nonlinear relation between splitting tensile strength and modulus of elasticity with compressive strength of high strength concrete is modelled and the effect of different effective parameters of Adaptive Neuro-Fuzzy Inference System is investigated on these models. To specify the best arrangements of parameters in the System to utilize in high strength concrete properties, different combinations of optimization methods and membership functions in the Sugeno system have been applied on more than 300 previously conducted experimental datasets. Both the grid partition and sub-clustering methods have been applied to models and compared to get the best combination of parameters

Instantaneous deflection of self-compacting and lightweight concrete slabs at early-age

© 2018 Growing Science Ltd. All rights reserved. This paper describes laboratory tests on twelve simply-supported one-way slabs including four lightweight concrete slabs in this study and previously conducted experiments on eight self-compacting reinforced concrete slabs subjected to loading at the age of 14 days. All slab were identical by dimensions of 3.8 m long supported on 3.5 m span, 400 mm wide, and 161 mm deep with 4N12 bars at an effective depth of 136 mm providing a reinforcement ratio of 0.008. After seven days moist-curing, the specimens were removed from the formworks and subjected to different values of the uniformly distributed loading including the self-weight of slabs. The mid-span deflection of slabs was recorded immediately after putting the loading blocks on the slabs. Despite close values of the compressive strength of the mixtures, the obtained results validate the effect of the concrete type on the instantaneous deflection of slabs. A wide range of existing models of the effective stiffness of reinforced concrete section were investigated to predict the instantaneous deflection of slabs. Majority of the models are developed for conventional concrete. Comparing the predicted and experimental results of mid-span deflection confirmed that the existing models are inadequate for lightly reinforced specimens such as slabs. New models are proposed and verified to predict the effective moment of inertia in the slabs with and without fiber reinforcing concretes

Predicition of Compressive Strength in Light-Weight Self-Compacting Concrete by ANFIS Analytical Model

© 2015 by B. Vakhshouri, S. Nejadi. Light-weight Self-Compacting Concrete (LWSCC) might be the answer to the increasing construction requirements of slenderer and more heavily reinforced structural elements. However there are limited studies to prove its ability in real construction projects. In conjunction with the traditional methods, artificial intelligent based modeling methods have been applied to simulate the non-linear and complex behavior of concrete in the recent years. Twenty one laboratory experimental investigations on the mechanical properties of LWSCC; published in recent 12 years have been analyzed in this study. The collected information is used to investigate the relationship between compressive strength, elasticity modulus and splitting tensile strength in LWSCC. Analytically proposed model in ANFIS is verified by multi factor linear regression analysis. Comparing the estimated results, ANFIS analysis gives more compatible results and is preferred to estimate the properties of LWSCC

Influences of side wall angle on heat transfer of power-law fluids in trapezoidal enclosures

In recent years, there is an important increase in technological applications of non-Newtonian fluids (NNF). NNFs are preferred over Newtonian fluids (NF) because of their superior hydrodynamic and thermal properties. NNFs are particularly used as damping fluid in shock absorbers, raw material for making of armors in defense industry and insulator in thermal systems. The use of NNF has become widespread in thermal systems in order to prevent over-heating problem which affects the efficiency. This study presents a numerical analysis for the natural convection in a two dimensional trapezoidal (isosceles trapezoid) enclosure filled with power-law NNF. The effects of various parameters are investigated on heat transfer on the bottom wall by developing a two dimensional model of such a cell. The bottom edge of the trapezoidal enclosure is considered as hot, top edge as cold while the side walls are considered as adiabatic. The considered parameters are power-law index (n) and Rayleigh number (Ra) and also the trapezoid side wall angle altering in the range of 0≤≤20. The power-law index has been varied in the range of 0.6≤≤1.8 and Rayleigh number in the range of 103≤≤105 while Prandtl number has been kept constant as 1000. The results reveal that the mean Nusselt number (̅̅̅̅ ) on bottom wall of trapezoid increases by increasing trapezoid angle and decreasing power-law index. According to evidences of the study, it may be suggested that the use of power-law NNFs may contribute to increase efficiency by averting the over-heating problems in trapezoidal thermal systems which are regarded as a significant application field in green and renewable energy systems.papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Structural lightweight concrete containing expanded poly-styrene beads; Engineering properties

Light-Weight Concrete containing Expanded Poly-Styrene Beads (EPS-LWC) is an approved structural and nonstructural material characterized by a considerably lower density and higher structural efficiency, compared to concrete containing ordinary aggregates. The experimental campaign carried out in this project provides new information on the mechanical properties of structural EPS-LWC, with reference to the strength and tension (by splitting and in bending), the modulus of elasticity, the stress-strain curve in unconfined compression, the absorbed energy under compression and reinforcement-concrete bond. The properties measured at seven ages since casting, from 3 days to 91 days, in order to investigate their in-time evolution. Mathematical relationships are formulated as well, between the previous properties and time, since casting. The dependence of the compressive strength on the other mechanical properties of EPS-LWC is also described through an empirical relationship, which is shown to fit satisfactorily the experimental results

Time-dependent deflection of conventional, self-compacting and lightweight concrete slabs

© ICE Publishing: All rights reserved. Design codes usually define time-dependent deflection as a multiple of instantaneous deflection. Therefore, the ratio of long-term to instantaneous deflection is crucial in the design of concrete structures. The experimental results of three series of experiments on long-term deflection of conventional, lightweight and self-compacting concrete slabs under sustained loads are compared and discussed in this study. The slabs were subjected to loading at age 14 d after casting. The flexural deflection caused by two distinct levels of applied load, and the effects of the drying shrinkage and creep were monitored for 225 d for three pairs of simply supported one-way slabs. Comparative analysis of the mechanical properties of concrete types at 14 and 28 d is conducted and the creep coefficient and drying shrinkage strain in the mixtures are determined. Furthermore, individual effects of these parameters on the ratio of long-term to instantaneous deflection are discussed. The results obtained confirm that, in the existing time-dependent deflection models, the effects of loading age, load value and the environmental conditions should be included. In addition, the experimental ratio of the long-term to instantaneous deflection in slabs is far from the predictions of ACI 318-14, AS 3600-09, EN 1992.1.1 and CSA-A23-04 codes

Effect of Concrete Strength and Reinforcement on Time-Dependent Deflection of Posttensioned Slabs

© 2017 American Society of Civil Engineers. Posttensioning is an effective construction method for structures with large spans, intensive loadings, and cost-efficiency considerations. The investigation developed a comprehensive understanding of how various reinforcement ratios and compressive strengths of concrete contribute to deflection of posttensioned two-way slabs. Furthermore, the numerical analysis compared the efficiency of various codes of practice to design the required reinforcement ratio in the presence of constant posttensioning tendons ratio and layout to provide the strength and deflection requirement. The interaction between the compressive strength-deflection and reinforcement ratio-deflection to find the optimum values of compressive strength and reinforcement ratio in a posttensioned two-way slab was also investigated. The finite-element model of a posttensioned 10 × 10 × 0.2-m (32.8 × 32.8 × 0.65-ft) two-way slab was analyzed and evaluated. The study confirmed the considerable effect of posttensioning to decrease the reinforcement ratio and deflection in a two-way slab. Also, a wide range of differences in design of a similar section of posttensioned concrete slab was observed by applying different codes of practice. The intensive effect of the concrete strength on the posttensioning design of slabs, especially in the lower ranges of compressive strength, was evident during the numerical analysis. Additionally, the reinforcement ratio shows a minor effect on the deflection of a posttensioned slab

Testing specimen effect on shrinkage of lightweight concrete

© 2018 ICE Publishing. All rights reserved. The shape and size of the testing specimen influence the measured shrinkage strain of concrete at different ages. This study compares the shrinkage strain of lightweight concrete containing treated expanded polystyrene beads measured by prism (285×75×75 mm) and cylindrical (150×300 mm) specimens for 225 d after 7 and 14 d of moistcuring, respectively. The shape of the specimen had a distinct effect on the shrinkage, especially immediately before and after the age of 60 d. The increasing trend of the shrinkage strain in the prism and cylinder specimens was different. Considering the specimen shape, a relationship is proposed and verified by the existing models and experimental data to predict the shrinkage strain of lightweight concrete

Modulus of Elasticity of Concrete in Design Codes and Empirical Models: Analytical Study

© 2018 American Society of Civil Engineers. The modulus of elasticity (MOE) is a key parameter in RC design. It represents the stress-strain relationship in the elastic range and is used in the prediction of deflection. Out-of-range estimations for the MOE in the existing codes of practice profoundly affected the design and performance of the concrete structures. This study included (1) the evaluation and comparison of the existing analytical models to estimate the MOE in normal strength concrete and (2) the proposal and verification of a new model. In addition, a wide range of experimental databases and empirical models, used to estimate the MOE from compressive strength and the density of concrete, were evaluated for verification of the proposed model. The results showed underestimation of the MOE for conventional concrete in the majority of the existing models. Also, considering the consistency between the density and mechanical properties of concrete, the predicted MOE values from the model, including the density effect, were more compatible with the experimental results than those from the other models presented

Experimental and numerical analysis of deflection of posttensioned lightweight concrete slabs

© 2018, © 2018 Taylor & Francis Group, LLC. This study utilizes the RAM Concept program to evaluate the previously conducted experimental results of deflection of three series of unbonded posttensioned lightweight concrete slabs with different mixture design and span length. Effect of provision in different codes of practice to estimate the deflection of posttensioned slabs is compared. Long-term deflection of slabs is analyzed and the effect of span length and mechanical properties of concrete are evaluated. There are considerable differences to estimate the short-term and long-term deflections by different design codes. The span length shows an inevitable effect on accuracy of the estimated deflection by different codes of practice