http://cfrp.blogfa.com/post-32.aspx
NONLINEAR FINITE ELEMENT ANALYSIS OF MODELS FOR

UNCONFINED AND FRP-CONFINED COLUMNS



A. Parvin, Associate Professor, aparvin@eng.utoledo.edu

and W. Wang, Former Graduate Student

Department of Civil Engineering, The University of Toledo, Toledo, Ohio USA



Abstract

This paper describes nonlinear finite element analysis of concrete columns upgraded by an innovative scheme such as the fiber-reinforced polymer (FRP) wrapping technique, which is used as a confinement. Behaviors of axially loaded unconfined and FRP-confined concrete columns were investigated and compared. Proposed finite element models were validated through experimental studies on similar columns reported in literature.

Numerical analysis results for small-scale columns showed that confinement increased the ductility and strength of the concrete columns loaded axially.

Keywords: Fiber composites, Concrete, Jacketed-columns, Finite element analysis.
http://www.4shared.com/file/15940928/2edb8b7b/parvin.html

http://cfrp.blogfa.com/post-35.aspx
Correlations between Mechanical Properties

of High-Strength Concrete

M. A. Rashid; M. A. Mansur, M.ASCE; and P. Paramasivam

Abstract: This paper discusses some important engineering properties of plain concrete for a wide range of compressive strength. A large volume of selected experimental data has been collected from existing literature and then analyzed. Particular emphasis has been given to studying the effects of concrete strength on the modulus of elasticity, tensile strength , flexural and splitting tensile, and Poisson’s ratio of concrete. Study on the effect of the size of specimens on the compressive strength and modulus of elasticity of concrete has also been included. The adequacy of some of the familiar relationships for predicting the modulus of elasticity and tensile strengths of concrete has been critically examined, and suitable expressions are suggested to cover concrete strength up to 120 MPa.

keywords: Mechanical properties; High-strength concretes; Aggregates; Size effect.

جهت مطالعه متن کامل مقاله از لینک زیر استفاده نمایید

متن کامل مقاله

http://www.4shared.com/file/16030007/274458a2/high_strength_concrete_paper.html

http://cfrp.blogfa.com/post-36.aspx

Determination of rectangular stress block parameters

for high performance concrete



Ertekin Oztekin, Selim Pul, Metin Husem

Black Sea Technical, University Dept. of Civil Engineering, 61080 Trabzon, Turkey

Abstract

Despite so much research on high performance concrete, the properties of this concrete are not known as well as those of ordinary concrete. There have been a lot of equations, rules and suggestions in the codes which are used in the design of reinforced concrete and prestressed concrete structures. They are obtained from experimental studies made on concrete that have compressive strength of less than about 40 MPa. It is not exactly known whether they could be used in the design of structures constructed by using high performance concrete. Therefore in this study, stress-strain and equivalent block parameters were obtained from experimental stress-strain diagrams for calculation of high performance reinforced concrete beams in flexure. The conclusions obtained from this study showed that determined rectangular stress block parameters can be used in the design of high performance reinforced concrete members in flexure.

Keywords: High performance concrete; Ordinary concrete; Stress-strain model; Hognestad’s model; Modified Hognestad’s model; Compressive strength; Rectangular stress block parameters and models

جهت دریافت اصل مقاله از لینک زیر استفاده نمایید

اصل مقاله

http://www.4shared.com/file/16039569/ed655f42/Determination_of_rectangular_stress_block_parameters_for_high.html

http://cfrp.blogfa.com/post-37.aspx
Behavior of Reinforced Concrete Beams

Strengthened with Externally Bonded Hybrid

Carbon Fiber–Glass Fiber Sheets



G. J. Xiong1; J. Z. Yang2; and Z. B. Ji3

1 Professor, Dept. of Civil Engineering, Shantou Univ., Shantou 515063, P.R. China. E-mail: gjxiong@stu.edu.cn

2 Postgraduate Student, Dept. of Civil Engineering, Shantou Univ., Shantou 515063, P.R. China. E-mail: gIjzyang@stu.edu.cn

3 Postgraduate Student, Dept. of Civil Engineering, Shantou Univ., Shantou 515063, P.R. China. E-mail: gIzbji@stu.edu.cn



Abstract:

A comparative test program including six beams was carried out. Two strengthening systems, namely hybrid carbon fiber glass fiber-reinforced polymer (H-CF/GF-RP) strengthening and CF-reinforced polymer strengthening were used. The test results showed that the H-CF/GF-RP strengthening led to a significant increase of ductility with a slight influence on stiffness of strengthened beams.

Keywords: Retrofitting; Fiber reinforced plastics; Hybrid methods; Ductility; Concrete, reinforced; Beams; Bonding; Fiberglass; Sheets.

جهت دریافت اصل مقاله از لینک زیر استفاده کنید

متن کامل مقاله



http://www.4shared.com/file/16039924/fea21f9f/BehaviorofReinforcedConcreteBeamsStrengthenedwith.html

http://cfrp.blogfa.com/post-44.aspx
Finite Element and Experimental Serviceability



Analysis of HSC Beams Strengthened with FRP Sheets





1Seyed Hamid Hashemi, 2Reza Rahgozar, 3Ali Akbar Maghsoudi



1PhD. Candidate and 2, 3 Assist. Professor, Department of Civil



Engineering, University of Kerman, PO Box 76169-14111, Kerman, Iran



E-mail: hamidhashemi55@yahoo.com



Abstract:



The use of externally bonded composite sheets or laminates is by now a diffuse technique to strengthen existing RC structures. However, some aspects of flexural condition still need experimental and numerical analysis; furthermore, especially for serviceability checks, there is a lack of code provisions. In this paper six reinforced high strength concrete (HSC) beams strengthened with FRP sheets were fabricated and tested, the finite element (FE) models adopted by ANSYS was performed to examine the structural behavior of tested beams was performed. A comparison between the finite element analysis results and the experimental data available on the specimens is made and by using trial and error method, the finite element model was calibrated. Six under-reinforced concrete beams were fabricated and tested to failure. With the exception of the control beam, one or four layers of CFRP were applied to the specimens. The structural response throughout the loading regime was primarily captured in terms of the load deflection behavior. The load deflection plots obtained from numerical study show good agreement with the experimental results. The serviceability characteristics of the test beams were evaluated in terms of the crack width, deflection and stress in steel and concrete. The crack patterns in the beams are also presented.



Keywords: Finite Element Model, FRP, HSC, Serviceability



American Journal of Applied Sciences 4(9):725-735, 2007

ISSN 1546-9239

Science Publications 2007


http://www.scipub.org/fulltext/ajas/ajas49725-735.pdf

http://cfrp.blogfa.com/post-46.aspx
Evaluation of Ratio between Splitting Tensile Strength and Compressive Strength for Concretes up to 120 MPa and its Application in Strength Criterion

by Nihal Arιoglu, Z. Canan Girgin, and Ergin Arιoglu



A large-scale regression analysis was carried out using experimental data gathered from various sources to evaluate the ratio of splitting tensile strength to cylinder compressive strength as a function of compressive strength of concrete. The reliability of the roposed equation based on experimental data for compressive strength ranging between 4 and 120 MPa (580 to 17,400 psi) was assessed by means of the integral absolute error (IAE). It is also shown that, by only knowing compressive strength and the ratio of tensile to compressive strength, the failure envelope for very highstrength concrete can be established using Johnston’s strength criterion without performing triaxial compression tests. A numerical example demonstrates the application of Johnston’s strength criterion.

Keywords: compressive strength; confinement; high-strength concrete; splitting tensile strength; stress.

جهت دریافت اصل مقاله از طریق لینک زیر اقدام نمایید

ACI Materials Journal, V. 103, No. 1, January-February 2006
http://www.4shared.com/file/16836216/83e450aa/Evaluation_of_Ratio_between_Splitting_Tensile_Strength_and.html

http://cfrp.blogfa.com/post-48.aspx
Deflection Control of Concrete Members

Based on Utility Theory

by Young Hak Lee, Andrew Scanlon, and Heecheul Kim

Design provisions for deflection control of concrete structures are generally empirical in nature and based on previous experience. Due to the increasing use of high strength materials, longer spans, and as a result more flexible members, a more rational approach is desirable. This paper explores the applicability of the utility theory as a basis for developing deflection control criteria. The approach considers uncertainties in member behavior and loading as well as lack of well-defined discrete serviceability limits. Monte Carlo simulation is used to develop histograms of selected deflection parameters. A serviceability loss function is then specified to define the onset of serviceability failure and an upper limit representing complete serviceability failure with associated costs. Optimum structural parameter (member depth) is obtained by minimizing total cost consisting of initial construction cost and probabilistic cost of failure. Results for one-way slabs are developed and compared with current ACI code provisions for minimum thickness.

Keywords: deflection; reinforced concrete; serviceability

جهت دریافت اصل مقاله از لینک زیر استفاده کنید

ACI Structural Journal, V. 104, No. 1, January-February 2007

http://www.4shared.com/file/16837264/9a17c024/Deflection_Control_of_Concrete_Members.html

http://cfrp.blogfa.com/post-52.aspx
Reinforced High-Strength Concrete Beams in Flexure

by M. A. Rashid and M. A. Mansur

M. A. Rashid is an associate professor in the Department of Civil Engineering and Director of Planning and Development at Dhaka University of Engineering & Technology, Gazipur, Bangladesh.

M. A. Mansur is a visiting scholar in the Department of Civil and Environmental Engineering at the University of Michigan, Ann Arbor, Mich.



ABSTRACT

Flexural test results generated on 16 reinforced concrete beams to evaluate the implications of using high-strength concrete (HSC) are reported. Test parameters considered include concrete compressive strength, ratios of tensile and compressive reinforcements, and spacing of lateral ties. It is found that the current code provisions for serviceability requirements of maximum crack width and ultimate strength are adequate up to a concrete strength of approximately 130 MPa. Concerns, however, are expressed regarding the adequacy of those for cracking moment and service load deflection. It is shown that stresses generated by shrinkage of concrete and the creep associated with it can significantly affect the cracking moment and service load deflection of reinforced HSC beams. Also, some detailing requirements for compression reinforcement need to be reassessed so as to utilize its full strength potential and ensure adequate ductile response of the beam when HSC is nvolved.

Keywords: beam; crack; deflection; ductility; flexural strength; highstrength concrete; reinforced concrete.

جهت دریافت اصل مقاله روی لینک زیر کلیک کنید

ACI Structural Journal, V. 102, No. 3, May-June 2005

http://www.4shared.com/file/17855655/420a3d32/Reinforced_High-Strength_Concrete_Beams_in_Flexure.html