[PDF] Effect Of Fiber Reinforcement On Bond Strength Of Lap Splices In Normal And High Strength Concrete Under Cyclic Seismic Loading eBook

Author : Omar Samir Gharzuddine
Publisher :
Page : 200 pages
File Size : 16,43 MB
Release : 2005
Category :
ISBN :

GET BOOK

With the more frequent use of FRC in earthquake resistant structures as a means for improving energy absorption and dissipation capacity, understanding the infl uence of steel fiber reinforcement on the bond strength between steel bars and c oncrete becomes of particular interest. While several experimental and analytical studies have concentrated on the bond characteristics under static load conditions, data on the bond stress characteri stics of steel bars in plain concrete or concrete applied with steel fiber reinf orcement is still very limited, particularly when the mode of bond failure is by splitting. This shortage of data makes it difficult at present to establish gen eral recommendations for computing the minimum volume of steel-fiber reinforceme nt needed to improve the seismic performance of reinforced beams, taking into ac count the bond parameters of the beam spliced reinforcement and the distribution of this reinforcement in the section. Experimentally investigating the bond cha racteristics of reinforcing steel bars embedded in FRC under seismic loading for better understanding of the mechanism by which fiber reinforcement improves the bond strength and seismic performance of spliced bars in tension constitutes th e primary objective of this proposed investigation. Also based on the results of this investigation, the main parameters that influence the response will be eva luated and discussed, and existing models for predicting the bond strength will be further validated or refined. To meet the objectives, 12 full-scale normal and high strength concrete beam spe cimens were tested. Each beam was designed with bar splices (20db) placed in a c onstant moment region at midspan. No transverse reinforcement will used in the s plice region. The design variables were the bar size (20 and 25 mm), ratio of co ncrete cover to bar diameter (c/db of 2.0 and 1.4), and the volume of fraction o f fibers (Vf = 0.0%, 0.5%, 1.0%, 1.5%). The test results indicated that the use of steel fibers in the splice region inc reased the ultimate load capacity, bond strength, reduced bond deterioration, im proved ductility, increased energy absorption capacity and also verified in part the equation proposed by Harajli and Mabsout2000 that accounts for the increase in bond strength of beams due to the presence of fibers.

Author : Ghaida' Khaled Joumaa
Publisher :
Page : 330 pages
File Size : 29,63 MB
Release : 2000
Category :
ISBN :

GET BOOK

To meet the objectives, 12 full-scale high strength concrete beam specimens were tested Each beam was designed with bars spliced in a constant moment region at midspan. The variables were bar size 20, 25, or 32 mm, and the amount of steel fiber reinforcement added in the splice region during casting: Vf = 0 5, 0 5, 1.0, or 2 0 %--The test results indicated that the use of steel fibers in the splice region increased the bond strength and the ductility of the mode of failure of the beam--specimens The increase in bond strength with high fiber content exceeded 3 square root fc, the maximum increase in bond strength of a reinforced concrete beam that could be achieved by using transverse reinforcement in the splice region.

Author : fib Fédération internationale du béton
Publisher : fib Fédération internationale du béton
Page : 448 pages
File Size : 11,83 MB
Release : 2000-01-01
Category : Technology & Engineering
ISBN : 9782883940505

GET BOOK

"In 1993, the CEB Commission 2 Material and Behavior Modelling established the Task Group 2.5 Bond Models. It's terms of reference were ... to write a state-of-art report concerning bond of reinforcement in concrete and later recommend how the knowledge could be applied in practice (Model Code like text proposal)... {This work} covers the first part ... the state-of-art report."--Pref.

Author : Ahmad Ali Rteil
Publisher :
Page : 306 pages
File Size : 47,87 MB
Release : 2002
Category :
ISBN :

GET BOOK

The deterioration of reinforced concrete structures is increasingly becoming a serious problem facing the infrastructure worldwide. To prolong the service life of existing structures, fiber reinforced polymer (FRP) sheets are being used. On the other hand, research reported in the literature indicates that a mechanism should exists which would confine the tension lap splices in high strength concrete (HSC) in order to have a more ductile failure and to increase the capacity of the lap splice. The main objective of this research is to assess the effect of FRP wraps in improving the serviceability and ultimate response of bond-critical regions in reinforced concrete members. The lack of research reported in the literature on the effect of the FRP wraps on bond strength makes this study significant. Moreover, the research will provide important design information that facilitates the introduction of FRP into design codes and encourage the use of this new technology. To meet the objective, 10 full-scale high strength concrete beam specimen were tested. Each beam was designed with 20-mm bars spliced in a constant moment region at midspan. The variables were: FRP type (glass or carbon), number of layers of FRP (1 or 2), and the configuration of FRP wraps placed in the splice region. Results of the study indicated that FRP wraps have similar effects to those of steel fibers and transverse steel reinforcement in confining the splices in HSC beam specimen. The brittle mode of failure is modified to a more ductile one. More bar lugs along the spliced bars are allowed to participate in the stress transfer between steel and concrete, and the average splitting bond strength is increased. Finally, a new index, Ktr, f, accounting for the presence and amount of FRP confining tension lap splices in HSC beams was proposed.

Author : Matthew J. Bandelt
Publisher :
Page : pages
File Size : 31,21 MB
Release : 2015
Category :
ISBN :

GET BOOK

High-performance fiber-reinforced cement-based composites (HPFRCCs) are a class of cement-based materials that exhibit a psuedo strain-hardening behavior in uniaxial tension after first cracking, and retain residual strength in compression after crushing. The unique mechanical properties of HPFRCCs have led researchers to investigate their use in structural applications where damage tolerance and energy dissipation is needed. Research on structural applications of steel reinforced HPFRCCs members has shown enhanced damage tolerance, shear capacity, flexural strength, inelastic deformation capacity, and life cycle performance. Recent research has focused on the interaction between mild steel reinforcement and HPFRCCs for modeling and design purposes. When reinforced HPFRCCs have been subjected to direct tension, early strain hardening and reinforcement strain localization have been observed caused by short debonded lengths, as opposed to long debonded lengths in traditional reinforced concrete. Short debonded lengths caused the HPFRCC reinforcement to fracture at lower levels of specimen deformation compared to reinforced concrete. This recent research indicates that bond strength between reinforcement and HPFRCCs may be higher than that of traditional reinforced concrete. Additionally, reinforcement tensile strains may be an important consideration for design and modeling of reinforced HPFRCC structural components. In this dissertation, the bond behavior between steel reinforcement and HPFRCCs is presented through experimental testing and numerical simulations. Bond experiments were conducted under monotonic and cyclic loading conditions where the HPFRCC material surrounding the reinforcement was in a flexural tension stress state. Monotonic test results show that bond strengths are 37% higher, on average, in reinforced HPFRCCs than in reinforced concrete. Additionally, bond-slip toughness (i.e., the area under the bond stress versus reinforcement slip curve) is higher in reinforced HPFRCCs than in reinforced concrete. Cyclic bond-slip experiments were performed for two types of HPFRCCs and compared to monotonic behavior using beam-end specimens. Results show that bond deterioration occurs in HPFRCCs after the maximum bond stress is reached, causing bond stress to reduce by 60%, on average. The loss of bond capacity and bond-slip toughness is due to combined crushing and splitting of the interface. The effects of bond on structural performance are examined through a study on monotonic and cyclic performance of reinforced HPFRCC beam specimens with varying reinforcement ratios. It is shown that cyclic deformation histories can decrease deformation capacity by up to 67%. Unlike traditional reinforced concrete, deformation capacity of reinforced HPFRCCs is shown to increase with increasing longitudinal reinforcement ratio. Results show that the difference between monotonic and cyclic deformation capacity becomes smaller as reinforcement ratio increases. Suggestions are made for providing a moderate amount of reinforcement to take full of advantage of the HPFRCC material toughness and improve structural performance and deformation capacity. An interface bond-slip material model is proposed based on the experimental results to model the interaction between steel reinforcement and HPFRCC materials. Simulations with the proposed interface model are compared with perfect bond models in finite element simulations by comparing numerical and experimental responses of reinforced HPFRCC structural members. Simulations are conducted on reinforced HPFRCC components under monotonic and cyclic deformation histories, and on members with varying reinforcement ratios. Including the proposed interface material model reduces variability in simulated deformation capacity, and leads to a consistent response in terms of cracking patterns and deformation capacity. A methodology is proposed to predict reinforced HPFRCC deformation capacity by examining reinforcement strains, modeling the interface conditions, and implementing a cyclic fracture energy material parameter from test data. The dissertation concludes with suggestions for future research that can extend the work presented herein. Suggestions for future work include additional experimental, numerical, and design-related research.

Author : Shadi Sam Najjar
Publisher :
Page : 372 pages
File Size : 40,42 MB
Release : 2001
Category :
ISBN :

GET BOOK

Several studies are reported in the literature on the effect of transverse reinforcement on bond and anchorage characteristics of reinforcing bars in normal and high strength concrete specimens. Transverse reinforcement provides concrete with confinement and increases its tensile resistance against splitting. When used to confine splices, transverse reinforcement leads to an increase in the bond capacity and to a more ductile and gradual mode of failure.--In 2000, a research program was carried out by Joumaa to study the effect of fiber reinforcement on bond strength and mode of failure of tension lap splices in high strength concrete. In this research, the effect of transverse reinforcement on bond strength and mode of failure of tension lap splices in beam specimens similar to those tested by Joumaa, will be investigated.