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CONTENTS
Volume 17, Number 3, March 2016
 

Abstract
An experimental investigation on the behaviour of concrete beams reinforced with various reinforcement, including ordinary steel bars, CFRP bars and CFRP prestressed concrete prisms(PCP). The main variable in the test program was the level of prestress and the cross section of PCP.The modes of failure and the crack width were observed. The results of load-deflection and load-crack width characteristics were discussed. The results showed that the CFRP prestressed concrete prisms as flexural reinforcement of concrete beams could limit deflection and crack width under service load and PCP can overcome the serviceability problems associated with the low elastic modulus/strength ratio of CFRP.

Key Words
flexural behavior; beams; CFRP; deflection; crack width

Address
J.F. Liang: State Key Laboratory Breeding Base of Nuclear Resources and Environment, Fundamental Science on
Radioactive Geology and Exploration Technology Laboratory, Nanchang, P.R. China
Deng Yu: College of Civil and Architecture Engineering, Guangxi University of Science and Technology,Liuzhou, P.R. China
Bai Yu: Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia

Abstract
The work is intended to demonstrate that the loss of bond between concrete and flexural steel which led in recent years a number of flat-slab structures to punching collapse under service loading conditions is also relevant to ultimate limit-state design. It is based on a comparative study of the results obtained from numerical experiments on flat slab-column sub-assemblages. The slabs were designed for punching either in compliance with the EC2 code requirements, which do not allow for such loss of bond, or in accordance with the compressive force-path method which considers the loss of bond between concrete and the flexural reinforcement in tension as the primary cause of punching. The numerical experiments are carried out through the use of a nonlinear finite element analysis package for which, although ample published evidence of its validity exists, additional proof of its suitability for the purposes of the present work is presented.

Key Words
compressive force path method; design of concrete structures; numerical experiments; flat slabs; punching

Address
Gregoria M. Kotsovou: HeriotWatt University, Edinburgh, U.K.
Gerasimos M. Kotsovos: Lithos Consulting Engineers, Vari, Greece
Emmanuel Vougioukas:National Technical University of Athens, Athens, Greece

Abstract
Although the self-compacting concrete (SCC) offers several practical and economic benefits and quality improvement in concrete constructions, in comparison with conventionally vibrated concretes confronts with autogenously chemical and drying shrinkage which causes the formation of different cracks and creates different problems in concrete structures. Using different fibers in the mix design and implementation of fibrous concrete, the problem can be solved by connecting cracks and micro cracks together and postponing the propagation of them. In this study an experimental investigation using response surface methodology (RSM) based on full factorial design has been undertaken in order to model and evaluate the polypropylene fiber effect on the fibrous self-compacting concrete and curing time, fiber percentage and fiber amount have been considered as input variables. Compressive strength has been measured and calculated as the output response to achieve a mathematical relationship between input variables. To evaluate the proposed model analysis of variance at a confidence level of 95% has been applied and finally optimum compressive strength predicted. After analyzing the data, it was found that the presented mathematical model is in very good agreement with experimental results. The overall results of the experiments confirm the validity of the proposed model and this model can be used to predict the compressive strength of fibrous self-compacting concrete.

Key Words
SCC; polypropylene fiber; compressive strength; RSM; modeling

Address
Mehdi Nazarpour and Ali Foroughi Asl: Department of Civil Engineering, Tabriz University, Tabriz, Iran

Abstract
This paper presents the properties of pervious concrete containing high-calcium fly ash. The water to binder ratios of 0.19, 0.22, and 0.25, designed void ratios of 15, 20, and 25%, and fly ash replacements of 10, 20, and 30% were used. The results showed that the use of fly ash as partial replacement of Portland cement enhanced the mixing of paste resulting in a uniform mix and reduced amount of superplasticizer used in the mixture. The compressive strength and flexural strength of pervious concrete were slightly reduced with an increase in fly ash replacement level, while the abrasion resistance increased due mainly to the pozzolanic and filler effects. The compressive strength and flexural strengths at 28 days were still higher than 85% of the control concrete. The aggregate size also had a significant effect on the strength of pervious concrete. The compressive strength and flexural strength of pervious concrete with large aggregate were higher than that with small aggregate.

Key Words
cement paste; pervious concrete; void ratio; fly ash; compressive strength; flexural strength

Address
V. Sata, C. Ngohpok and P. Chindaprasirt: Sustainable Infrastructure Research and Development Center, Department of Civil Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand

Abstract
Realistic assessment of the performance of reinforced concrete structural members like columns is needed for designing new structures or maintenance of the existing structural members. This assessment requires analytical capability of employing proper material models and cyclic rules and considering various load and displacement patterns. A computer application was developed to analyze the non-linear, cyclic flexural performance of reinforced concrete structural members under various types of loading paths including non-sequential variations in axial load and bi-axial cyclic load or displacement. Different monotonic material models as well as hysteresis rules, were implemented in a fiber-based moment-curvature and in turn force-deflection analysis, using proper assumptions on curvature distribution along the member, as in plastic-hinge models. Performance of the program was verified against analytical results by others, and accuracy of the analytical process and the implemented models were evaluated in comparison to the experimental results. The computer application can be used to predict the response of a member with an arbitrary cross section and various type of lateral and longitudinal reinforcement under different combinations of loading patterns in axial and bi-axial directions. On the other hand, the application can be used to examine analytical models and methods using proper experimental data.

Key Words
reinforced concrete; cyclic behavior; force-deflection; moment-curvature; bi-axial; fiber-based, material model; computer application; windows-based

Address
Fatemeh Shirmohammadi: Walter P Moore Associates, Inc., Kansas City, Missouri, USA
Asad Esmaeily:Department of Civil Engineering, Kansas State University, Manhattan, Kansas, USA

Abstract
Confined transverse reinforcement was arranged in a plastic hinge region to resist the lateral load that increased the lateral confinement effect in the bridge substructure. Columns increased the seismic performance through securing stiffness and ductility. The calculation method of transverse reinforcements at plastic hinges is reported in the AASHTO-LRFD specification. This specification was only proposed for solid reinforced concrete (RC) columns. Therefore, if this specification is applied for another column as composite column besides the solid RC column, the column cannot be properly evaluated. The application of this specification is particularly limited for composite hollow RC columns. The composite hollow RC column consists of transverse, longitudinal reinforcements, cover concrete, core concrete, and an inner tube inserted in the hollow face. It increases the ductility, strength, and stiffness in composite hollow RC columns. This paper proposes a modified equation for economics and rational design through investigation of displacement ductility when applying the existing specifications at the composite hollow RC column. Moreover, a parametric study was performed to evaluate the detailed behavior. Using these results, a calculation method of economic transverse reinforcements is proposed.

Key Words
transverse reinforcement;AASHTO; ductility; composite; hollow column

Address
Deok HeeWon, Taek Hee Han and Woo-Sun Park: Coastal Engineering Division, Korea Institute of Ocean Science and Technology,
Ansan 426-744, Republic of Korea
Seungjun Kim: Department of Geotechnical Disaster Prevention, Daejeon University,62 Daehak-ro, Dong-gu, Daejeon 300-716, Republic of Korea
Young Jong Kang: Department of Architectural, Civil and Environmental Engineering, Korea University,145 Anamro Seoul 156-701, Republic of Korea


Abstract
This paper presents numerical modeling of the structural behavior of CFRP (carbon fiber reinforced polymer) strengthened RC (reinforced concrete) beams under four-point bending. Simulation of debonding at the CFRP-concrete interface was focused, as it is the main failure mode of CFRP strengthened RC beams. Here, cohesive layer was employed to model the onset of debonding, which further helps to describe the post debonding behavior of the CFRP strengthened RC beam. In addition, the XFEM approach was applied to investigate the effects of crack localization on strain field on CFRP sheet and rebar. The strains obtained from the XFEM correlate better to the test results than that from CDP (concrete damaged plasticity) model. However, there is a large discrepancy between the experimental and simulated loaddisplacement relationships, which is due to the simplification of concrete constitutive law.

Key Words
ABAQUS; reinforced concrete; CFRP strengthening; debonding; XFEM

Address
Dongliang Zhang, QingyuanWang and Jiangfeng Dong: College of Architecture and Environment, Sichuan University, Chengdu 610065, China

Abstract
After the industrial of steelmaking by-products are processed properly, they can be used in civil engineering, not only as a substitute for natural resources and to reduce costs, but also to provide environmental protection. This study used different amounts (10%, 20%, 30%, 40%,and 50%) of desulphurization slag to replace natural fine aggregates in ready-mixed soil materials, and tested the physical and fresh properties (slump, slump flow, tube flow, initial setting time, and bleeding) and hardened properties (compressive strength, ball drop, ultrasonic pulse velocity) of the materials. The variations between the performances of the materials with different mix proportions were discussed. When desulphurization slag is used in RMSM, the workability can be enhanced obviously significantly. When the replacement of desulphurization slag is 50%, the slump flow is increased by 110mm compared with the control group, and the initial setting time increases as the replacement increases, because of bleeding. When the replacement is 10% and 20%, the compressive strength at various ages is higher than that of the control group. When the replacement is 10%, the compressive strength at 7 days is higher than that of the control group by 60%, and the ultrasonic pulse velocity is proportional to the compressive strength, which increases with age and decrease as the replacement increases. An appropriate replacement can effectively accelerate construction, and allow projects to be finished ahead of schedule; therefore, an appropriate replacement, is applicable for ready-mixed soil materials.

Key Words
industrial by-products; steelmaking slag; desulphurization slag; ready-mixed soil materials (RMSM).

Address
Yi-Fang Shiha, Shih-Shong Tseng, Her-Yung Wang and Chih-Ting Wei:Department of Civil Engineering, National Kaohsiung University of Applied Sciences, 807, Taiwan, R.O.C


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