36 deflection response from the experimental observation. In general, all five slab specimens that were modeled showed a very strong correlation between the finiteelement model and the experimental results (Figure 2-16). The ascending branch followed a very similar line as the experimental data and then, at the point of punchingshear, the FEA curve experienced a very sharp downward trend. The two experiments (N-GR-C slab and L-SH-C slab) shown in Figure 2-16 have concrete compressive strengths that varies from 34 MPa to 47 MPa and a flexural reinforcement ratio, ρ, which varies from 0.24% to 0.15%. In developing the tension-stiffening curve the author only describes selecting 0.4 for the weakening function (see Equation (2-18)), but neglected to disclose what effect of varying the weakening function would have on the load- deflection results. Even though the concrete strength and flexural reinforcement varied in the specimens, the weakening function remained constant. The constant value of the weakening function appears to suggest that it is independent of the value of 𝑓 𝑐 ′ and ρ. This assertion would be in contrast to the literature data which showed tension-stiffening increases with increases in 𝑓 𝑐 ′ and ρ.
reinforcedconcreteslabs supported on columns with L, T, and cruciform shapes. Reference studies verifying the accuracy of these code provisions are typically not provided. Empirical data of punching failures of slabs supported on columns with L, T, and cruciform shapes are limited due to the cost and time required to test specimens with slab thicknesses and column sizes commonly used in practice. In this paper, the punchingshear behaviour of five interior L-shaped slab-column connections, one without a slab opening and four with slab openings, subjected to static concentric loading are analyzed using a plasticity-based nonlinear finiteelement model (FEM) in ABAQUS. The FEM is similar to models previously calibrated at the University of Waterloo and was calibrated considering nine slabs that were tested to study the impact of column rectangularity on the punchingshear behaviour of reinforcedconcreteslabs. The finiteelementanalysis results indicate that shear stresses primarily concentrate around the ends of the L, and that current code predictions from ACI 318-19 and Eurocode 2 may be unconservative due to the assumed critical perimeters around L-shaped columns.
types of shear reinforcement, because punchingshear failure can happen behind the bent-up bars. Hawkins (1974) reported tests performed with different punchingshear reinforcements and he found that the shear reinforcement increases the punchingshear capacity of the slabs. Broms (2000) combined the bent-up bars in the first two perimeters with closed stirrups and such arrangement was able to avoid any punchingshear failure. Closed stirrups were also used by many researchers, as another type of shear reinforcement; among others Islam and Park (1976), Hanna et al. (1975), Pillai et al. (1982) and Robertson et al. (2002). Slabs with shear heads were tested by Corley and Hawkins (1968) and by Dilger and Ghali (1981). The shear studs that consist of individual vertical bars were used in slabs tested by Seible et al. (1980), Dilger and Ghali (1981), Elgabry and Ghali (1987), Megally and Ghali (2000), Robertson et al. (2002), Kang and Wallace et al. (2005) and Tan and Teng (2005). Shear heads are an expensive type of shear reinforcement, however, it is essential to be used in cases where large openings close to the connection area are needed and thus this demands large adjustments to the flexural reinforcement. The shear studs have been widely used due to the advantages that they provide such as mechanical anchorage and highly quality. Shear studs are difficult in installation, however they are the most popular punchingshear reinforcement. Adetifa and Polak (2005) used a new type of shear reinforcement post-installed in flat slabs, called shear bolts.
2000; Rankin and Long, 1997; Wood, 1961) for RC, SFRC and strengthened fibre-reinforced polymer (FRP) members (Zeng et al., 2016), sector models based on axisymmetric assumptions (Einpaul et al., 2015, 2016) and finite-element methods (Belletti et al., 2016; Soares and Vollum, 2015). Membrane action effects on continuous slabs have been recently analysed using nonlinear finite-elementanalysis (NLFEA) and different modelling approaches, for example using three- dimensional (3D) hexahedral elements (Genikomsou and Polak, 2017) or multi-layered shell elements (Cantone et al., 2016). In this paper, the shrinkage effects on concrete cracking and on the punchingshear resistance are studied. This aspect could be significant for the structural assessment of existing structures carried out using refined numerical tools, such as NLFEA methods, which are able to take into account hidden resistance capacities, but are less conservative than analytical approaches (Belletti et al., 2015a, 2015b).
A combined bending and shearpunching test series, called X, is carried out at VTT. The target structure is a two-way simply supported concrete plate with a span of 2 m and a thickness of 25 cm. The deformable projectile is made of stainless steel tube with a shallow spherical dome nose and its mass is 50 kg. In the first two tests, X1 and X2, the outer diameter of the missile was 253 mm and the wall thickness was 3 mm. The impact velocity was 166 m/s. No clear shearpunching occurred in these tests. In order to achieve shearpunching, the missile was modified for test X3. The diameter of the missile was 219 mm and the wall thickness was 6.35 mm. For test X4 the impact velocity was increased from 144.7 m/s to 168.6 m/s. Capabilities of different calculation methods in assessing both global bending deformation and local shear deformation and possible shearpunching are studied. The models and methods comprise a two-degree-of-freedom (TDOF) model CEB (1989) and two finiteelement (FE) programs, an in-house code and a commercial general purpose code Abaqus (2014). Additionally, some semi-empirical formulae are used for comparisons. Tests X1 and X2 have been analysed in Borgerhoff et al. (2013).
These are straight or deformed pieces of cold-drawn steel wire, straight or deformed cut sheet fibres, melt extracted fibres, shaved cold drawn wire fibres and fibres milled from steel blocks which are suitable to be homogeneously mixed into concrete or mortar. Steel fibres mixed into the concrete can be a substitute to the provision of conventional steel bars or welded fabric in some structural members. The idea has been in existence for many years (Berard, 1874b) and it has been used in a limited range of applications: among the first significant uses was the patching of bomb craters in runways during World War II. The commercial use of this material gathers momentum in the 1970s predominantly in Europe, Japan and the USA. (The Concrete Society TR63, 2007)
reinforcement. Hawkins  published a paper presenting an overview of tests performed with different punchingshear rein- forcement systems such as steel heads, bent-up bars, and stir- rups. He concluded that shear reinforcement increases the punching strength even for small slabs and that the detailing is crucial to increase the strength and to avoid undesired failure modes. Dilger and Ghali  focus on improving existing shear reinforcement systems, which were at this time generally bent- up bars or different types of stirrups. They found that the anchorage conditions of the shear reinforcement are crucial. This research was accompanied by the development of the shear friction model that was ﬁrst developed for shear in beams as illustrated by Loov , Tozser , and later applied for slab– column connections as indicated by Dechka  and Birkle . Shehata , Shehata and Regan , and Shehata  devel- oped a model for slabs without shear reinforcement that was based on the approach of Kinnunen and Nylander. Gomes and Regan [12,13] extended Shehata’s model by implementing the contribution of the shear reinforcement. Further research has been conducted by Regan and Samadian  and Oliveira et al.  who continued their work leading to several recent publications introduced by Trautwein et al.  and Carvalho et al.  about punching tests with shear reinforcement. Chana and Desai  and Chana  performed an extensive experimental campaign of punchingshear tests with shear rein- forcement. Thereby, they tested slabs with conventional shear links and slabs with a special shear reinforcement system con- sisting of links welded together to a cage (known as ‘‘s- hearhoop’’ system). Broms [20,21] presented a further development of the model of Kinnunen and Nylander and introduced a combination of stirrups and bent-up bars as punchingshear reinforcement. In 2005, he summarized a main part of his earlier work in his dissertation treating design meth- ods for punching of ﬂat slabs and footings with and without shear reinforcement; Broms . The research group of Hegger, Hegger et al. , Hegger et al. , Hegger et al. , Hegger et al. , Siburg and Hegger  performed extensive
such as a widening of the slab support with concrete mushrooms or steel heads (Martinez- Cruzado et al. 1994; Hassanzadeh 1996). In addition, the bending resistance of the slab can be increased with an external reinforcement made of steel or new materials like fiber-reinforced polymer (FRP) composites (Harajli and Soudki 2003; Ebead and Marzouk 2004; Chen and Li 2005; Esfahani et al. 2009; El-Enein et al. 2014). For both concepts the behavior of the slab remains brittle however. A third possibility is the installation of additional shear reinforcement, which normally increases ductility; examples are shear studs (Menétrey and Brühwiler 1997; El-Salakawy et al. 2003; Adetifa and Polak 2005; Fernández Ruiz et al. 2010; El-Shafiey and Atta 2011; Feix et al. 2012; Polak and Bu 2013), drop panels (Martinez-Cruzado et al. 1994; Ebead and Marzouk 2002), FRP shear bolts (Lawler and Polak 2011; Meisami et al. 2013) or stirrup solutions with FRP laminates (Binici and Bayrak 2005a; Sissakis and Sheikh 2007). In some cases, the elements are prestressed for immediate unloading of the slab (Menétrey and Brühwiler 1997; El-Shafiey and Atta 2011). However, in the case of prestressed bolts, due to their short length, even small deformations caused by creep for example can substantially decrease the designated prestressing force. Faria et al. (2009, 2011) strengthened square concreteslabs with a side length of 2.3 m and 100- or 120-mm thickness with prestressed steel strands. These were placed above the column on the upper concrete surface and anchored on both sides in the bottom part of the slab, in holes drilled at an inclination of ca. 11°, using an epoxy adhesive. The punching resistance was increased by 34–48% for slabs with two strands in one direction only and by 61% for one slab with strands in both directions. The prestressing method also improved the serviceability limit state and the post-collapse behavior where a second peak load at 78% of the first peak load
A paper presents a numerical analysis using ANSYS finiteelement program to develop a model for expecting the performance of seven lightweight aggregate reinforcedconcrete deep beams with 28 days compressive strength 26MPa and density of 1950Kg/m 3 strengthened in shear by externally bonded CFRP. All beams have same dimensions (150mm width, 400mm depth and 1400mm length), longitudinal steel reinforcement ratio ρ=0.0115 and shearsteel reinforcing 5@100mm. CFRP strips 50mm width are used for strengthening. The effective variable parameters were: a/d ratio, CFRP spacing, orientation and number of layers. The results obtained from the ANSYS finiteelement model got good agreement when compared to the experimental results  which were done for the same deep beams with the same material properties, internal reinforcement and strengthening schemes. The results show that the ultimate load and deflection predicted by numerical analysis is less than experimental results by 9% and 5.7% in average respectively. By using CFRP strips in shear strengthening, the ultimate load has increased by 18%, 13.6%, 32% and 27.3% for vertical, horizontal, inclined and double vertical layers, respectively for a/d=1. For a/d =0.8 the increase is 10% for vertical strips. It is recommended that the CFRP is placed such that the principal fiber orientation is either normal to the longitudinal beams axis or normal to the line joining the applied load and supports (strut path) to resist higher tensile stresses and strains distributed along it.
Abstract. An innovative solution to the corrosion problem is the use of fiber-reinforced polymer (FRP) as an alternative reinforcing material in concrete structures. In addition to the non corrodible nature of FRP materials, they also have a high strength-to-weight ratio that makes them attractive as reinforcement for concrete structures. Extensive research programs have been carried out to investigate the flexural behavior of concrete members reinforced with FRP reinforcement. On the other hand, the shear behavior of concrete members, especially punchingshear of two-way slabs, reinforced with FRP bars has not yet been fully explored. The existing provisions for punching of slabs in most international design standards for reinforcedconcrete are based on tests of steelreinforcedslabs. The elastic stiffness and bonding characteristics of FRP reinforcement are sufficiently different from those of steel to affect punching strength. In the present study, the equations of existing design standards for shear capacity of FRP reinforcedconcrete beams have been evaluated using the large database collected. The experimental punchingshear strengths were compared with the available theoretical predictions, including the CSA S806 (CSA 2012), ACI-440.1R-15 (ACI 2015), BS 8110 (BSI 1997), JSCE (1997) a number of models proposed by some researchers in the literature. The existing design methods for FRP reinforcedconcreteslabs give conservative predictions for the specimens in the database. This paper also presents a simple yet improved model to calculate the punchingshear capacity of FRP- reinforcedconcreteslabs. The proposed model provides the accurate results in calculating the punchingshear strengths of FRP-reinforcedconcrete slender slabs.
The constitutive models from Section 2 were implemented into Abaqus to conduct failure analysis and to obtain the possible maximum ultimate load. Reliable constitutive models applicable to steel rein- forcing bars and concrete are available in the Abaqus material library. For the FRP model, Abaqus has inbuilt failure criteria, such as Tsai-Wu, that has been used in much research [20-22]. However, these failure criteria only include the linear behavior of FRP. Therefore, FORTRAN language was used as a subrou- tine, UMAT, in Abaqus, to code nonlinear constitutive equations for including a nonlinear material library to model FRP. All the validity of the material models for steel, FRP and RC have been veried individually by testing against experimental data [4,10] and were not duplicated here. For rectangular RC slabs with and without FRP, the slabs have been veried against experimental data  , and for square RC slabs with and without FRP, verication and numerical studies have also been performed  and were not duplicated here.
From equation 2, it is obvious that the above ACI 318-95 code equation totally ignores the influence of tension flexural reinforcement when calculating the concreteshear resistance and depends heavily on concrete strength. This is not too unreasonable in the case of steel reinforcement, since with its high modulus of elasticity, the dominant factor determining concreteshear resistance will be the area of concrete in compression, which remains constant as the neutral axis depth does not vary much with normal steel reinforcement ratios. Hence, in case of steel, the ACI 318-95 equation gives good predictions though conservative at low levels of reinforcement. However, when using FRP reinforcement with low modulus of elasticity, the concreteshear resistance becomes more sensitive to the reinforcement stiffness, as the neutral axis depth reduces significantly with low reinforcement ratios. In such cases, the ACI 318-95 prediction becomes too unconservative.
opment in the concrete can be improved. Glass fibers are able to improve the flexural strength due to their high tensile strength of 1.700 - 3.700 N/mm 2 and their good bond with the cement matrix. However, this effect ap- pears only at very high fiber contents from 3% - 5% of concrete volume . In these ratios the fibers cannot anymore mixed in the concrete because of the loss of consistency and bad fiber distribution. Due to their rela- tively low stiffness compared to steel fibers, glass fibers are able to bridge very small cracks and to support the concrete already during setting (flow of hydration heat and shrinkage) and contribute to its impermeability. Con- crete covers as well as minimal cement contents must not be ensured. Therefore GFRC is used for thin elements or for repair of existing components. Examples for usage are prefabricated elements in façade construction, noise barriers, place formwork, fire-resistant panels, design elements in the interior or for the renovation of old floors as glass fiber modified concrete . In Germany there are a few standards dealing with test methods for glass fiberreinforcedconcrete . These standards are used for testing thin panels of traditional glass fiberreinforcedconcrete with high fiberconcrete. For structural use of GFRC no rules exist. At the moment slabs on ground are constructed with reinforcement bars, steelfiberreinforcedconcrete, with combined reinforcement (bars and steel fibers) or are made pre-stressed. If slabs on ground may also be constructed with structural GFRC, has still to be investigated.
ete Glass FiberReinforcedConcrete (GFRC) has been used as an architectural building material in North America since the 1970’s, though its use in Eastern Europe extends back to the 1940’s. It is typically an exterior product, but can also be used for interior applications.
institutes as steel fibres are much costly and their cost is increased as increasing the percentage of steel fibres in the given concrete mix. so the concept is to design a suitable concrete mix and to analyze the various properties of this particular design mix as all know the function of the fibre based concrete is to arrest cracks, fibre composites possess increased extensibility and tensile strength, both at first crack and at ultimate, particular under flexural loading; and the fibres are able to hold the matrix together even after extensive cracking but by using these scrap fibres I wish to maintain the cost of the mix and obtain the improved values of the different properties related to concrete mix. Key Words: Scrap Steel fibres; Design Mix; Compressive strength; splitting tensile strength; Cracking; Workability.
The idea expresses that fiber fortification in concrete encase street base has the ability to expand accomplishment by expanding weariness life base and adjust protection from intelligent breaking black-top. The investigations additionally make that properties of solidified SFRCC, for example, flexural quality, are strikingly superior to those ordinary RCC. In this way, impact of steelfiber for amazing asphalt development can be suggesting very. The proposed SFRC asphalt configuration come up gainful other approach to SFRC for impact in street development industry both in practical and ecological part. Utilize simple plan approach, present laying and material generation gear, SFRC asphalt might be the perfect unique route in street development.
This study is carried out with addition of steel fibres in the concrete specimens and exposed to elevated temperatures and subjected to shear and pull out tests. This study is concluded that the addition of steel fibres resists the brittle failure of the concrete specimen and increases the bond strength. The randomly oriented steel fibres resists the propagation of random shaped cracks and the cracks occurs mostly through the shear planes which is mostly ductile cracks. Therefore the sudden collapse of the structure due to shear during the fire accidents can be avoided. However more detailed studies with various structural members instead of simple cubes. The replacement of copper slag up to 40% as fine aggregate is the environmental and cost effective of concrete preparation.
11 they reached their failure load, on the other hand, FRC beams lost around 40% of their bearing capacity when they reached their failure load initially and the rest was lost gradually. Wang (2005) compared concrete containing polypropylene fibers with plain concrete. At service load; crack widths were less in polypropylene fiberconcrete compared to the crack widths of plain concrete and the ductility of polypropylene fiberconcrete was larger by 40% (Wang, 2005). Also, the FRC is higher in strength than plain concrete (Reddy, 2015). A number of researchers compared FRC beams with different BMF volume fractions. They found that increasing volume fraction of BMF resulted in an increase in concrete cracking resistance, flexural strength and splitting behavior of concrete (Ayub, 2014; Jiang, 2014). Kara (2015) invented a numerical method for estimating the curvature, deflection and moment capacity of hybrid fiberreinforced polymer/steelfiberreinforcedconcrete beams and compared his results with experimental results from previous studies. His numerical technique gives an accurate prediction of moment capacity, curvature and deflection of hybrid fiberreinforced polymer/steelfiberreinforcedconcrete beams. The numerical results also indicate that beam ductility and stiffness are improved when steel reinforcement is added to FRP reinforcedconcrete beams (Kara, 2015). Sahoo (2015) found that cracks in FRC are more than cracks in plain concrete and it was increased with the increase of fiber volume fraction because fibers enhance the distribution of stresses along the concreteelement.
Premature loading of reinforcedconcrete flat slabs in multi storey buildings during construction may occur after shuttering removal and loading slabs earlier than usual to meet project time targets. Some case studies showed failure of flat slabs, which were prematurely loaded during the construction process before it reaches its full characteristic strength (at 28 days), which was used in structural design. This research aims to address this problem through experimental testing and design application according to current building codes. Eight specimens with dimensions of 1100 * 1100 mm and a total thickness of 120 mm were experimentally tested to study the effect of concrete age and actual compressive strength at loading on the punchingshear capacity of reinforcedconcreteslabs. All specimens were supported by a square column with dimensions of 150 ×150 mm and loaded at the four corners with a span of 1050 mm. Accelerating admixture was used in three studied specimens to achieve higher concrete compressive strength at early ages compared to their companions of normal concrete without these admixtures. It was found that increasing concrete compressive strength of slab from 25 𝑁/𝑚𝑚 2 to 35 𝑁𝑙𝑚𝑚 2 (40% increase) for normal concrete, without early admixture, improved punchingshear capacity by 26%, while increasing it to 45 𝑁/𝑚𝑚 2 (80% increase) improved punchingshear capacity by 49% when the