lightweight concrete (LWC) is commonly lower than that of normal-weight concrete (NWC) having the same compressive strength (Sagaseta and Vollum, 2011; Yang et al.,2012). The shear transfer capacity of reinforcing bars crossing the interfaces is also influenced by the frictional resistance of concrete as because tensile stresses in the reinforcement depends on the relative slip along the interface (Ali and White, 1999). This signifies that rupture of aggregate particles owing to crack propagation results in reducing the coefficient of friction of concrete and tensile stresses generated in the transverse reinforcement. Overall, the shearfriction resistance at interfacial cracks needs to be determined considering the variation of the coefficient of friction of concrete according to the unit weight and compressive strength of concrete. However, the mechanical diversity of shearfriction of different concrete types is undervalued in most of the previous models (Loov and Patnaik, 1994; Mattock, 2001; Shaikh, 1978; Walraven et al., 1987) as they are empirically formulated using limited test data with a narrow range of unit weight or compressive strength of concrete.
Based on the kinematics of the shearfriction behavior shown in Figure 1.3, crack width, w, is related to the shear displacement, Δ, and the surface roughness of the interface. Due to the kinematic nature of the Δ-w relationship, it should not be expected that the amount of clamping force will significantly affect this relationship. Walraven and Reinhardt (1981) demonstrated very little effect on the Δ-w relationship for monolithically cast concrete despite varying the interface reinforcing ratio, ρv = A vf /A cv , from 0.56% to 2.23% as can be seen in Figure 1.5. From Figure 1.5 it can also be seen that the concretestrength, f’c, has some effect on the Δ-w relationship since a small increase in crack width, w, is noted as the concretestrength is increased. This observation reinforces the behavior represented in Figure 1.3.b, where the stronger concrete matrix will allow the aggregate to “slide up” over the matrix rather than “crush into” it as may be the case with the weaker matrix. Walraven and Reinhardt (1981) also showed that an increase in surface roughness resulted in an increase in crack width. In this study the variation in roughness was modest and was affected by aggregate grading in the concrete mix design for these monolithically cast specimens.
Fig. 1(a)shows the arrangement of the push tests specimen used to model FE model to determine the shear resistances and the load-slip behavior of HSFGB shear connectors in composite beam with precastconcrete slabs. The model consist of an IS WB 350 steel beam and two concrete slabs that are 450-mm long, 500-mm wide and 100-mm thick attached to the flanges of the steel beam and reinforcement mesh having 10 mm diameter wire and 200 mm pitch were cast in the concrete slabs in two layers to limit the splitting of the slabs. M22 8.8 high strengthfriction grip bolt was used. The unit weight of steel is 7850 Kg/m 3 , modulus of elasticity is 2.0 x 10 5 N/mm 2 and the poison’s ratio is 0.3. 390 Mpa, 500 Mpa and 830 Mpa are tensile strength of I section, reinforcement bar and the high strength bolt respectively. The density of concrete is taken as 2400kg/m 3 . The short-term modulus of elasticity of concrete is taken as 31622.78 Mpa.
ABSTRACT: The main goal of this experimental and analytical study is to investigate the behavior and shearstrength of steel fiber reinforced concrete corbels. . An experimental results and predicted values by truss analogy method, ACI Building Code (ACI 381-83) provisions for corbels, and shearfriction equation is investigated. Test were carried out on twenty-seven samples of size 150 x 150 x 200- mm were shear span was varied as shown in table (E) and concrete corbels reinforced with steel fiber. M-60 grade of concrete is used in corbels. The different properties of corbels varied and fiber content and span to depth ratio also varied. The different percentage of fiber content of 0.5 percent intervals was used ranging from 0.5 to 4 percent .For all the reinforced concrete corbels vertical loading was used. It was observed that the ultimate strength of reinforced concrete corbels along with fibers can be predicted by adding the fibers contribution to strength using the shearfriction equation to the ACI Building Code provisions. It is found that considerable improvement in ultimate shearstrength, toughness and first crack in the corbels.
In order for the composite slab to behave monolithically, the bond at the interface between the precast slab and concrete topping must remain intact. The interface shear stress must be sufficiently transferred along the interface of the two concretes. However, when load is applied on the weaker interface bond, it may cause interface failure due to slippage of the concrete topping. If this slip occurred and the composite action is lost, only friction force is acted between the precast slab and concrete topping. Therefore, each concrete layers will deform separately due to the vertical forces which causes tension at the bottom of the two concretes. Figure 1.4 and 1.5 show the stress distributions for the weak interface bond (non-composite section) and the strong interface bond (composite section) of the composite slab.
design codes. However, most of the equations specified in the codes have been derived from the tests of normal strengthconcrete. Therefore, this study verifies whether the existing equations can also be extended to the range of ultra-high strength of UHPC. The equations largely consist of two types of resistance: friction and cohesion. However, in many equations, the effect of shear keys is not directly accounted for (AASHTO 2017; CEN 2004; fib 2013), and the shear key geometry can only be reflected as the coefficients of friction or cohesion correspond- ing to a very rough surface or an indented surface in an indirect way. On the other hand, in a few design equa- tions, the shape of the shear keys is reflected as a separate term in a more detailed manner (AASHTO 2003; JSCE 2004, 2010). Because the effect of shear key geometry, including the number of shear keys, on the shearstrength is one of the main concerns in this study, the equations presented in the AASHTO guide specifications (2003) and JSCE recommendations (2004, 2010) were analyzed in detail and compared with the test results to verify the applicability of these equations to UHPC.
planes to slip along shear cracks is less than that of normal weight concrete, as the crack face of lightweight concrete is smoother than that of normal weight concrete. Other experimental data  also showed that shear cracks in normal strength, normal weight aggregates concrete propagate through cement matrix around aggregate particles, while these in lightweight aggregate concrete mainly penetrate through coarse aggregate particles. As a result, Sherwood et al.  pointed out that shear transferred by aggregate interlock would be negligible in lightweight concrete. However, experimental investigations to evaluate the reduced shear capacity of lightweight concrete joints are very scarce.
Most of the research work on soil-interface shear behaviour reported in the literature has been done on sands. Previous studies dealing with the shear resistance of sand sliding on an interface is dependent on the roughness of the contact surface with respect to the size of the sand, sand type, normal stress, density of the sand and rate of displacement. Sand grains tend to slide on very smooth surfaces, giving skin friction angles as low as 10 ο Yoshimi and Kishida, Uesugi et al. . Most of these investigations were carried out with different experimental apparatus such as: direct shear tests have been used to study the behaviour of soil-structure interfaces. Several factors such as structural material, soil properties, and surface roughness have been investigated to better understand their effects on the interface characteristics (Kulhaway and Peterson ). Yoshimi and Kishida  utilized a ring torsion apparatus for interface testing and observed sand deformation by using x-ray photography. Yin et al. conducted a large shear test to observe the distribution of relative displacement along the interface. Frost et al. studied the evolution of the structure of sand adjacent to the geomembrane, and found that it was directly influenced by the surface roughness.
NWs and the gold substrate as the strength of metallic bonding is typically on the order of GPa . This is due to the presence of a thin layer of silver oxide, as shown in the high-resolution TEM images (Figure 1). Second, it is not appropriate to treat the ZnO NWs as the molecular junc- tions where the contact areas remain constant (in our case the NW cross-sections) , otherwise the interfacial shearstrength would be too small. This is reasonable because it is very likely that the NW is not perfectly perpendicular to the substrate. Edge of the NW tip could be in contact with the substrate, and the contact area can then be approxi- mately fitted with a sphere. Third, previous experiments showed that electron beam increases adhesion force between semiconductors and metals [34, 35]. For contacts between ZnO NW tips and a gold substrate, we found the adhesion force did not show noticeable change when the contact area was exposed to electron beam only for a short time (e.g., less than 10 s) . Last, although our experi- mental method gave rise to the first measurement of the friction data between NW tips and a substrate, we are aware that it cannot measure the friction as a function of the progressively applied normal force. MEMS devices with simultaneous normal and lateral force measurement capability are under development to address this issue.
researchers have shown somewhat conﬂicting results. Das et al. (2005) found that SCC beams had higher shearstrength compared to conventional concrete (CC). Wilson and Ki- ousis (2005) reported, however, that shear provisions within the American Concrete Institute (ACI 318) did not always yield conservative results for SCC beams. Test results from Burguen˜o and Till (2005), Bendert and Burguen˜o (2006a, b) showed that the shear behavior of both SCC and CC beams are very similar to each other. In addition, the ultimate shearstrength of SCC and CC beams were almost the same. Hassan et al. (2008, 2010) and also Choulli and Mari (2005) reported there was no signiﬁcant difference between the shear behavior of SCC and CC beams, and that the ultimate shearstrength of SCC beams was only slightly lower than CC beams. Dymond et al. (2007, 2009, 2010) tested a single, precast bulb-tee bridge girder and concluded that the theo- retical prediction of the simpliﬁed method was conservative compared with experimental test results of the beam. These conﬂicting results may be attributed to the speciﬁc SCC mix designs for each study; limited information was provided on each researcher’s SCC mix design. With aggregate interlock playing such a critical role in shear behavior (Taylor 1970, 1972, 1974), SCC mixes that rely on material-based chan- ges—higher paste contents and smaller rounded aggre- gates—may result in substantially reduced shearstrength.
Friction surfacing is an advanced technology that can effectively deposit a metal on another metal. In this process, the consumable rod is rotated and forced against the substrate in the axial direction. A large quantity of hotness is produced due to the friction among the consumable rod and the friction contact surface between the substrates, and the contact end of the metal consumption rod is plasticized after a certain period of time. The substrate is then horizontally moved to a vertically consumable rod, so that a layer of mechanical material is deposited on the substrate. Friction surface treatment has been used for a variety of hard surface metal coatings, such as mild steel or stainless steel coating on the tool steel coating. In this process, the strong adhesion between the coating and the substrate can only be achieved by applying a high contact pressure, but this requires expensive machinery [1,2].
The Natural Coarse Aggregate (NCA) was replaced with Recycled Coarse Aggregate in various percentages ranging from 0%, 20%, 40%, 60%, 80% and 100%. The mix with 0% replacement contains pure NCA while the mix with 100% replacement is with pure RCA.M50 grade concrete was designed by IS code method to have a mix proportion of 1:1.75:3.02 with a water-cement ratio of 0.38. For preparing fibre reinforced concrete, steel fibres of 1% volume fraction were added to the concrete. All the ingredients such as fiber, cement, sand, aggregate, super plasticizer and water were put in a pan mixer and thoroughly mixed for uniformity. The uniformly mixed concrete was then used to find out the workability through compaction factor and V-B time tests. The concrete mix is then poured in Double –L (push-off) moulds to find out shearstrength. Vibration was effected by table vibrator after filling up the moulds. For each mix three specimens were cast. The specimens were de-molded after 28 hours and then cured in curing pond for 28 days. After 28 days, the specimens were removed from curing pond and allowed to surface dry. Then they were tested in compression testing machine to record the failure shear load. The special „Z‟ type specimen is so designed that it fails in shear under compressive load in compression testing machine. The shearstrength is calculated as ratio of failure shear load and shear area. For every mix, the shearstrength is recorded as average of three test results.
Since the previous strength prediction models for the perfobond rib connector were proposed based upon the results of push-out tests conducted on concretes with compressive strength below 50 MPa, push-out test is performed on perfobond shear connectors applying ultra high perfor- mance concretes with compressive strength higher than 80 MPa to evaluate their shear resistance. The test variables are chosen to be the diameter and number of dowel holes and, the change in the shearstrength of the perfobond rib connector is examined with respect to the strength of two types of UHPC: steel fiber-reinforced concrete with compressive strength of 180 MPa and concrete without steel fiber with compressive strength of 80 MPa. The test results reveal that higher con- crete strength and larger number of holes increased the shearstrength, and that higher increase rate in the shearstrength was achieved by the dowel action. The comparison with the predictions obtained by the previous models shows that the experimental results are close to the values given by the model proposed by Oguejiofor and Hosain .
beam size should lead to decrease of the aggregate interlock contribution. According to Taylor’s analysis, the size effect would be impossible to occur in light- weight concrete and high-strengthconcrete beams. This is because in these beams the cracks go through the aggregates instead of going around them. His size effect theory, however, was unconfirmed by the later tests. In 1978, Walraven  tested two series of three beams each, in which the size effect in lightweight and normal weigh concrete specimens were compared. The results showed a very pronounced size effect occurred in lightweight concrete beams. Bazant and Kim  and Bazant and Sun  then applied fracture mechanics principles to analyze the test data existing in literature. The cracking produced by shear was assumed to propagate with a dispersed zone of microcracks at the fracture front. To take the dispersed and progressive nature of cracking at the fracture front into account, some assumptions have been introduced: the total po- tential energy release caused by fracture in a given structure is a function of both the length of the fracture and the area of the cracked zone. Dimensional analysis of the energy release rate then showed that the nominal shear stress at failure should not be a constant but should vary as 0.5
ABSTRACT: Polymer concrete is a type of concrete which has polymer in it and similar ingredients of concrete. During mixing process polymers are added to the concrete, in turn they increase the binding properties and adhesion with the aggregates. Here we used the natural rubber latex as a polymer and metakaolin as additive which increases the compressive and flexural strength and reduces the permeability. Total 12 numbers of high strengthconcrete beams of M70 grade were casted in the laboratory out of which 6 are controlled beams and 6 are strengthened by adding rubber latex. The strengthened beams of M70 grade showed 2 to 20% of increase in shear capacity with respect to the controlled beams of same grade.
Injured buildings because of happening earthquake and /or buildings which are recognized weak in the manner that their first strengthening must be recovered and /or even their strengthening becomes more they are repaired and strengthened until endure the next earthquakes .The repaired buildings must supply the obligation of regulations .Anyway repairingand strengthening vibratory of a building may be more expensive The end decision about that whether repaired and making resistant are done ,or if do how is ,need to assess economical multilateral .Nowadays application of advanced composite materials is increasing in civil engineering for reinforcing and making resistant of structures.Composite materials are made from combination of two materials fiber and matrix that fibers are usually from carbon ,glass and aramid and matrix is from family of polymer matrixes like Apoksi. Composite materials will be had an assigned role for reinforcing of strategic structures specially marine structures and making resistant of executed reinforced concrete structures in earthquake area because of having variety and good benefits in near future .As yet performed examinations all were confirmatory to increase axial ,shear and bending strength of strengthened samples by composite fiber .Strengthened beams by CFRP and GFRP from bearing capacity (end strength ) show more suitable condition than beams without strengthening and also decreasing of changing the vertical figure while servicing and limiting width and spreading cracks in concrete is expected to more endurance
aggregate and concluded that the maximum strength was attained by replacing fine aggregate upto 40% by copper slag. Alnuaimi (2012) carried out studies on use of copper slag as a replacement for fine aggregate in RC slender columns. The percentage of copper slag as a replacement for fine aggregate varied from 0 to 100%. The increase in copper slag also led to higher slump and the mixture reached collapse in the 80 and 100% levels of copper slag. This is because of glassy surface of copper slag that absorbs less water than sand. Brindha et al., (2010) carried out experiments to assess the corrosion and durability characteristics of copper slag admixed concrete and reported that copper slag concrete exhibits good durability characteristics and can be used as an alternative to fine aggregate.
Instrumental to the understanding of lightweight concrete behavior is the concrete‟s defining characteristics and the process of creating it. The definition of lightweight concrete varies depending on the source, but is generally any concrete with a density around 115 to 125 pounds per cubit feet (pcf) in comparison to normal weight concrete, which is about 150 pcf. Typically this represents about a twenty percent reduction in mass, which is desirable for the design of buildings in seismic areas. A reduction in mass leads to a reduction in lateral forces, so the required sizes of members and foundations are smaller, thus reducing cost as well as construction time.