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Reinforced High-Strength Concrete Beams in Flexure
by M. A. Rashid and M. A. MansurM. 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
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; serviceabilityجهت دریافت اصل مقاله از لینک زیر استفاده کنید
ACI Structural Journal, V. 104, No. 1, January-February 2007
Behavior of Reinforced Concrete T-Beams Strengthened in Shear with Carbon Fiber-Reinforced Polymer—A
Behavior of Reinforced Concrete T-Beams Strengthened
in Shear with Carbon Fiber-Reinforced Polymer—An
Experimental Study
by Abdelhak Bousselham and Omar Chaallal
This paper presents results of a wide and extensive experimental investigation on reinforced concrete (RC) T-beams retrofitted in shear with externally bonded carbon fiber-reinforced polymer (CFRP). In total, 22 tests were performed on 4520 mm-long T-beams.
The parameters investigated were as follows: 1) the CFRP ratio (that is, the number of CFRP layers); 2) the internal shear steel reinforcement ratio (that is, spacing); and 3) the shear length to the beam’s depth ratio,
a/d (that is, deep beam effect). The main objective of the study was to analyze the behavior of RC T-beams strengthened in shear with externally applied CFRP by varying the aforementioned parameters. The results showed that the contribution of the CFRP to the shear resistance is not in proportion to the CFRP thickness (that is, the stiffness) provided, and depends onwhether the strengthened beam is reinforced in shear with internal transverse steel reinforcement. Results also confirmed the influence of the ratio a/d on the behavior of RC beams retrofitted in shear with external fiber-reinforced polymer (FRP). Finally, comparison of the shear resistance values predicted by ACI 440.2R-02, CSA S806-02, and fib TG9.3 guidelines, with the test results clearly indicated that the guidelines fail to capture important aspects, such as the presence of the transverse steel and the ratio a/d on the one hand, and overestimates the shear resistance for high FRP thickness (and hence high FRP stiffness), on the other.Keywords: polymer; reinforced concrete; shear; strain; strengthening
جهت دریافت اصل مقاله از لینک زیر استفاده نمایید
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
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