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This study includes a series of pullout tests which contain fifty four specimens with short bonded length (5db) to study the effect of many variables on bond strength for normal and high strength concrete. The variables are: (bar diameter, concrete compressive strength and cover). The study also studies the effect of each variable on bond strength,...
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... a result, an increase in concrete compressive strength will make it possible to decrease the concrete cover or the increases in the bar diameter will be required to increase the concrete cover. This is shown clearly in Fig.(9) which illustrates the relationship between bond strength and the rate (C/d b ) for compressive strength varying from (20 to 75) MPa. ...
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Citations
... It is a generally accepted result that the decrease in bond strength at room temperature with increasing rebar diameter [17][18][19][20][21][22]. Soroushian and Choi [17] used experiments to research the influence of steel bar diameter on local bond performance and proposed a method for calculating ultimate bond strength. ...
... Abtahi and Li [20] quantified the effect of steel bar diameter on bonding behavior and proposed a method for calculating the bond-slip curve. Kheder et al. [21] explored the effect of steel bar diameter on ultimate bond strength through experiments. Based on the test results, a calculation formula was developed to predict the ultimate bond strength by coupling the steel bar diameter, the strength and the concrete cover thickness of the concrete. ...
... Compared with the test results of concrete cover thickness, the test of the influence of steel bar diameter on the ultimate bond strength was carried out more widely, as depicted in Fig. 16(b). Both the experimental [17,18,[20][21][22]24,25] and simulation results show that the ultimate bond strength decreases with increasing bar diameter. Increasing the bar diameter from 16 mm to 25 mm reduces the simulated ultimate bond strength at elevated temperatures and after cooling by 14% and 12%, respectively. ...
The refined numerical simulation method was used to study the influences of the concrete cover and the diameter of the rebar on the bond-slip properties of deformed reinforced concrete under two fire scenarios. The feasibility and rationality of the refined simulation method were verified by comparison with the experimental results. Subsequently, the influences of the concrete protective layer thickness and the diameter of the rebar on specimen failure pattern, bond failure mechanism, bond-slip curve, and the distribution of the stress and strain for the steel were investigated. The effects of parameters on ultimate, residual bond strength and ultimate slip were mainly discussed. The results show that the failure pattern of the specimen exposure to heat conditions changes from concrete splitting to steel bar pull-out as the concrete cover thickness increases; the shape of the bond-slip curve was affected by the concrete cover thickness, regardless of the fire scenario, rebar diameter and the target temperature. As the rebar diameter increased, the bond strength at high temperatures and after cooling down decreased when the specimen experienced the same temperature. Finally, the formulation for the bond strength and slip at high temperatures and after cooling down was suggested by comparing with the experimental and calculated results, which can take into account the thickness of the concrete protection layer, the diameter of the reinforcement bar, the fire scenario and the temperature.
... Studies on the bonding mechanism between normal concrete and ordinary reinforcement, the calculation method of bonding capacity, and design anchorage length are numerous and relatively mature, and the achievements of these studies have been included in relevant concrete design specifcations. Currently, examination of the bonding properties between diferent kinds of concrete and reinforcement has become a hot spot: for example, the bonding properties between recycled coarse aggregate concrete and reinforcement [5], between steel fber reinforced concrete and reinforcement [6], between alkaliactivated slag concrete and reinforcement [7], between geopolymer concrete and reinforcement [8], and between high-strength concrete and reinforcement [9] have been examined. Experiments were mainly conducted to analyze the efects of parameters such as the replacement rate of recycled concrete, steel fber content, reinforcement cover, and concrete splitting tensile strength on the bond strength between concrete and reinforcement. ...
In bearing capacity testing of prestressed concrete pipe piles, grouting material is filled up to the bottom of the pipe pile, which is equipped with a finishing rolled rebar. The reaction force of the reaction beam is transferred to the anchor pile through the bonding force between the finishing rolled rebar and grouting material. Therefore, investigating the bonding properties between the finishing rolled rebar and grouting material is essential to remove barriers to the application of the anchor pile method in bearing capacity testing of the prestressed concrete pipe pile. In this study, the bonding properties of 11 groups of specimens were studied through pull-out tests, and the effects of the cover thickness, diameter, and anchorage length of reinforcement on the bond strength between finishing rolled rebar and grouting material as well as on the bond stress-slip curve were explored. The test results showed that the bond stress-slip curve between finishing rolled rebar and grouting material can be divided into two stages, i.e., slip stage and splitting failure stage. In the slip stage, a linear relationship exists between bond stress and slip amount, and microcracks appear in the grouting material around the finishing rolled rebar. In the splitting failure stage, the slip amount increases rapidly under uplift load. Finally, the grouting material around the finishing rolled rebar forms a failure zone, and splitting failure occurs. The bonding capacity and bond strength between finishing rolled rebar and grouting material increase with the increasing cover thickness of the rebar. The bond strength is the maximum for a relative cover thickness of 3.0, and the difference between the maximum and minimum values is more than 9%. The bonding capacity between rebar and grouting material increases slightly with the increasing rebar diameter, but the bond strength decreases with the diameter, and the difference between the maximum and minimum bond strengths is more than 21%. As the contact area between finishing rolled rebar and grouting material increases, the bonding capacity between them increases with the increasing anchorage length of the rebar. However, the bond strength first increases, then decreases, and finally stabilizes with the increasing anchorage length, and the difference between the maximum and minimum bond strengths exceeds 14.64%.
... Table 2 shows quantities for used materials by weight for production of one cubic meter of concrete. These quantities were taken from some previous works [Kheder et al. 2005] with slight modifications. Vol.9, No.12, 2017 77 longitudinal reinforcement in compression side (top side) without stirrups except two of 3 mm plain bar stirrups at each side used for fixing the bars and the pipes in their positions during the casting as shown in Figure 2. The laboratory tensile tests on bars showed that the average yield stress for 5 mm diameter was 607 MPa while for 8 mm diameter was 588 MPa. ...
This work involves experimental study for the effect of longitudinal hollows on behavior of HSC one way slabs. Six slabs of 1000×450×70 mm were tested. The parameters of the study are number, diameter and volume of the hollows and flexural reinforcement ratio (ρ). The hollows were made by embedding PVC pipes. Presence of hollows reduces cracking and ultimate capacities of the slab. The reductions are larger with increasing number, diameter and volume of hollows. Maximum reduction in cracking capacity is 26.9 % when 32 % hollows are used with ρ = 0.45 %. Using 32 % hollows reduces the ultimate capacity by 12.9 % when ρ = 0.45 % and by 20.3 for ρ = 1.2 %. Using 32 % hollows with ρ = 1.2 % prevents the flexural failure to finally take place due to the bearing failure at supporting region. Increasing (ρ) has significant effect on ultimate capacity and this effect is smaller in hollowed slab than in solid slab. Presence of hollows increases deflection values and makes load-deflection response softer especially in advanced loading stages. Also, crack width values at service stage increases with increasing volume of the hollows. Longitudinal hollows have convergent effects in reduction of the ultimate capacity and ultimate loads that result to very small effect on slab adequacy for carrying the applied loads. This makes it is useful using the hollows in construction of one way slabs especially when HSC is used.
... Table 2 shows quantities for used materials by weight for production of one cubic meter of concrete. These quantities were taken from some previous works [Kheder et al. 2005] with slight modifications. ...
This work involves experimental study for the effect of longitudinal hollows on behavior of HSC one way slabs. Six slabs of 1000×450×70 mm were tested. The parameters of the study are number, diameter and volume of the hollows and flexural reinforcement ratio (ρ). The hollows were made by embedding PVC pipes. Presence of hollows reduces cracking and ultimate capacities of the slab. The reductions are larger with increasing number, diameter and volume of hollows. Maximum reduction in cracking capacity is 26.9 % when 32 % hollows are used with ρ = 0.45 %. Using 32 % hollows reduces the ultimate capacity by 12.9 % when ρ = 0.45 % and by 20.3 for ρ = 1.2 %. Using 32 % hollows with ρ = 1.2 % prevents the flexural failure to finally take place due to the bearing failure at supporting region. Increasing (ρ) has significant effect on ultimate capacity and this effect is smaller in hollowed slab than in solid slab. Presence of hollows increases deflection values and makes load-deflection response softer especially in advanced loading stages. Also, crack width values at service stage increases with increasing volume of the hollows. Longitudinal hollows have convergent effects in reduction of the ultimate capacity and ultimate loads that result to very small effect on slab adequacy for carrying the applied loads. This makes it is useful using the hollows in construction of one way slabs especially when HSC is used.
... Table 2 shows quantities for used materials by weight for production of one cubic meter of concrete. These quantities were taken from some previous works [Kheder et al. 2005] with slight modifications. Vol.9, No.12, 2017 77 longitudinal reinforcement in compression side (top side) without stirrups except two of 3 mm plain bar stirrups at each side used for fixing the bars and the pipes in their positions during the casting as shown in Figure 2. The laboratory tensile tests on bars showed that the average yield stress for 5 mm diameter was 607 MPa while for 8 mm diameter was 588 MPa. ...
Studying the behavior and capacity of reinforced concrete one way slabs with openings.
... Al-Aukaily, 2005 [16] used a series of pull-out tests for prismatic specimens shown in Figure (2.24) with short bonded length (5d b ) to study the effect of (bar diameter, concrete compressive strength and cover) on bond strength for normal and high strength, and suggests two equations to link bond strength with these variables . ...
... .24) Testing specimen details, after Al-Aukaily, 2005[16] ...
The reinforcement of concrete with steel results in stress transfer from steel to concrete and hence it becomes essential to understand the bond and anchorage behaviour of concrete. A strong bond between the steel reinforcement and concrete is a major contributing factor to the durability of reinforced concrete structures. This article focusses on reviewing the bond strength of concrete with steel rebars considering various parameters such as compressive strength, diameter of the bar, concrete cover, bar geometry and anchorage length using pull-out and beam bond tests. The role of artificial neural networks (ANN) in predicting the bond strength of concrete using these parameters is also discussed. Various international codes and literature discussing the pull-out and beam bond tests have provided a better understanding of the bond properties of concrete.
This paper discuses experimentally the effect of steel bar diameter and embedment length on the bond stresses, bond stress versus slip relation, failure pattern and load versus deflection response of high strength reinforced concrete beams with dimensions (100 mm width x200 mm height x1100 length). Four beams specimens were provided with three embedment lengths (80 mm), (100 mm) and (120 mm) in addition to two different bar diameters (10mm) and (16mm). The test results concluded that the bond stresses and the relative displacement decrease with increasing the embedment length and bar diameter.
The present experimental study are carried out to have a clear understanding of the bond strength between high performance steel fiber concrete HPSFC with three selected shapes of fibers, which were straight steel fiber SS , hooked end steel fiber HS and waved steel fiber WS and steel reinforcing bars. Six groups which consisted from thirty-three pullout cubic specimens of size 100 mm were fabricated to study the effect of some selected parameters such as, shapes of fiber SS ,HS and WS, reinforcing bar diameter 10 mm ,12 mm and 16 mm , volume fraction of steel fibers V f 0% , 1% and 2% and aspect ratio of steel fibers l/d 30 , 65 and 90. In addition, twenty seven cubes having the same size of the pullout specimens with average three concrete cubes from each concrete mix (nine mixing) were tested in compression to find their compressive strength. It was found that the addition of HS fiber has much effect in enhancing bond strength than that enhancement accrued by addition of SS or WS fibers. On the other hand, the bond strength increases as bar diameter decreases. The addition of steel fibers to concrete strengthens the bond between the reinforcing bar and the concrete.
