Columns had 8 bars 14 at each corner and middle point of the four faces and were transversally **reinforced** with Ø8 **stirrups** posed at 100mm. All connections were uniformly supported on rubber bearings along the four sides at an average distance of 30 mm from the edges. This study presents a failure analysis upon four **shear** **reinforced** **flat** slab column connections with thin **plates**. tension **reinforcement** ratio was 0.5%. Five perimeters of **shear** **reinforcement**, 10@100mm, under star direction were fitted in the critical perimeter. Average effective depth of the slab was 155 mm and designed concrete **strength** was C20/25. The results showed that the concrete uniaxial compressive **strength** does not influence the final failure values. Load- deflection behavior was mainly influenced by the type of **shear** **reinforcement** than the concrete **strength**. Bond conditions and anchorage length highly influence the effectiveness of double headed stud-rails **reinforcement**. Specimens **reinforced** with stirrup beams showed rotations 50% smaller that the compared ones, stud-rails showing better ductility behavior.

Show more
19 Read more

become ܨ ൌ 1.17 MN and ܨ ௦ ൌ 1.01 MN, respectively, and the **shear** capacity of the plate is 1.58 MN. The averaged force ܨ in case X4 is 1.63 MN. In previous **tests** X1 and X2 the cubic compression **strength** values of concrete were 41.6 MPa and 46 MPa, respectively. The **reinforcement** in slab X1 was similar to the **reinforcement** used in slabs X3 and X4. The **shear** **reinforcement** was reduced for test X2 and the **shear** capacity due to **stirrups** is 0.24 MN. **Punching** capacities predicted by formula (1) for **tests** X1, X2, X3 and X4 are compiled in Table 1. These results are in agreement with the **experimental** observations. Except case X4 the **shear** **punching** **strength** of the slab has not yet been exceeded. According to these calculations, scabbing capacity was exceeded in **tests** X3 and X4. The observed scabbing area was about 0.7 m 2 after the test X3. No scabbing was observed in test slabs X1 and X2 and this is also in agreement with the calculation results shown in Table 1. Only in the case X4 the average value of time dependent force resultant exceeds the total **punching** capacity of the wall.

Show more
10 Read more

Abstract **Punching** **shear** **reinforcement** systems such as studs and **stirrups** are used to improve the **punching** **shear** **strength** of ﬂat slabs. A three dimensional ﬁnite element model (FEM) is developed through Ansys 10 computer software, to carry out the nonlinear analysis of 16 ﬂat-slab models with and without **punching** **shear** **reinforcement**. Several important parameters are incorporated in the analysis, namely the column size, the slab thickness and the **punching** **shear** **reinforcement** system in order to study their effects on the ﬂat slab behavior. A parametric study was carried out to look at the variables that can mainly affect the mechanical behaviors of the model such as the change of loading types and positions and slab with openings. Good correlation is observed between the results of the proposed model and other **experimental** one, resulting in its capability of capturing the fracture of ﬂat slab under **punching** **shear** behavior to an acceptable accuracy.

Show more
20 Read more

the finite element method had been carried out in order to investigate the effect of this additional **reinforcement** for both normal **strength** and high **strength** concrete. The computer program ANSYS-V12.0 has been utilized in the finite element analysis. The obtained results indicate that, the proposed **shear** **reinforcement** system has a positive effect in the enhancement of both the **punching** **shear** capacity and the strain energy of interior slab-column connection of both normal and high **strength** concrete. The general finite element software ANSYS can be used successfully to simulate the **punching** **shear** behaviour of **reinforced** concrete **flat** **plates**. Joaquim A.O. Barros et.al, (2015) presented a new type of carbon-fibre-**reinforced**-polymer (CFRP) laminate of U-shape is used by adopting a novel hybrid technique for the simultaneous flexural and **punching** strengthening of existing RC slabs. Besides, this hybrid technique aims to provide a better bond performance for the embedded-through- section (ETS) and near-surface mounted (NSM) CFRPs by improving the anchorage conditions.Moreover,a higher resistance to the susceptibility of occurrence of other premature failure modes, like concrete cover delamination, is offered by using this hybrid technique. A 3D nonlinear finite-element (FR) model is developed to simulate the **experimental** **tests** by considering the nonlinear behaviour of the constituent materials. The **experimental** program and numerical model are described, and the relevant results are analysed. Francisco Natario et.al, (2015) investigated the behaviour of cantilever bridge deck slabs under fatigue loads. A specific **experimental** programme consisting on eleven **tests** under concentrated fatigue loads and four static **tests** (reference specimens) is presented. The results show that cantilever bridge deck slabs are significantly less sensitive to **shear** –fatigue failures than beams without **shear** **reinforcement**. Some slabs failed due to rebar fractures. They presented significant remaining life after first rebar failure occurred and eventually failed due to **shear**. The test results are finally compared to the **shear**-fatigue provisions for the fib-Model Code 2010 and the critical **shear** crack theory to discuss their suitability.

Show more
25 Read more

20 Read more

The **punching** **shear** resistance of **reinforced** concrete ground supported slab represents a wide category of concrete structure and subsoil interaction problems. The spatial fracture mechanism itself is inﬂuenced by various input parameters. The most important ones include geometrical dimensions of the structure, properties of the selected con- crete materials, load or properties and characters of soil underneath. The importance of this research area is testiﬁed by the extensive research underway—see Kueres et al. (2017), Hoang and Pop (2016), Alani and Beckett (2013), Halvonik and Fillo (2013), Siburg et al. (2012), Siburg and Hegger (2014), Song et al. (2012), and Husain et al. (2017). General evaluation of **tests** of typical slabs is provided in Alani and Beckett (2013) and Ricker and Siburg (2016). An interesting comparison and critical review of the **punching** **shear** **strength** of ﬂat slabs can be found in Bogda´ndy and Hegedus (2016) or Zabulionis et al. (2006). Important overall results from the ﬁeld of behaviour of **reinforced** concrete footings are presented also in Siburg and Hegger (2014), Hegger et al. (2006, 2007), Aboutalebi et al. (2014) and Siburg et al. (2014). The approaches to calculation, modelling and computer programs are focused on in

Show more
14 Read more

An **experimental** program was carried out by Rizk et al. (2011) to investigate the influence of the slab size on the **punching** **shear** resistance. Five thick square slabs were tested. The slabs were 300 mm and 400 mm thick with side dimension of 2650 mm. The slabs were loaded through a small column stub 400 × 400 mm. Four slabs were cast using high **strength** concrete and one using normal concrete. **Shear** **reinforcement** was used in one of the high **strength** concrete slab. The results of the **punching** **shear** **strength** showed good agreement with the values predicted using the CEB-FIP Model Code (1990). The ACI 318-11 code was found to underestimate the **punching** **shear** **strength** for all slabs by an average of 17% except for one high **strength** concrete slab. This high **strength** slab had the lowest **reinforcement** ratio and the predicted value was overestimated by 19%. It was highlighted by the authors that the **experimental** **shear** **strength** was different in two slabs. The slabs had different concrete **strength**, similar slab thickness and **reinforcement** ratio. Both slabs were designed to fail under **punching** **shear** stresses. This finding showed that having a constant number for the size effect factor depending on the slab depth only, as used in major design codes, may not account for the size effect and it should also include the concrete compressive **strength**.

Show more
122 Read more

Concrete is an isotropic heterogeneous composite material made by cement, water and aggregates, however, macroscopically, it is considered as homogeneous. The compressive **strength** of concrete is much higher than its tensile **strength** and its complex behaviour requires the development of appropriate constitutive models for its simulation and analysis. All of the proposed constitutive models, e.g. (Willam and Warnke 1975, Simo and Ju 1987, Mazars and Pijaudier-Cabot 1989, Yazdani and Schreyer 1990, Feenstra and de Borst 1995, Lee and Fenves 1998, Imran and Pantazopoulou 2001, Grassl et al. 2002, Addessi et al. 2002, Jirasek et al. 2004, Salari et al. 2004); may show limitations and they are not suitable for all types of analysis. In continuum mechanics, the macroscopic response of concrete can be characterized through its evolution law of the failure envelope in multi-axial loading. A brief description on the mechanical behaviour of concrete and then an overview on its non-linear modelling with respect on cracking models, plasticity theory, continuum damage mechanics and damage coupled with plasticity, are presented in this chapter.

Show more
257 Read more

The force time function due to a deformable missile impact was calculated with the Riera method and by using a FE model. Also a more accurate folding model in which the actual formation of folds is taken into consideration was used. Two finite element codes, Abaqus and a special purpose finite element program, are used in calculating the responses of the present test **plates**. Additionally a TDOF model is used for structural response studies. Displacements calculated with three different methods applying two different loading functions were compared with the **experimental** recordings. The shape of the loading function did not significantly affect the results in the considered cases. Maximum deflections obtained by Abaqus and TDOF model were somewhat underestimated. Bending vibration behavior of the slab could not be properly calculated with the solid model. A 3D solid FE model is needed in studying local **shear** **punching** behavior of test plate in detail.

Show more
10 Read more

36 deflection response from the **experimental** observation. In general, all five slab specimens that were modeled showed a very strong correlation between the finite element 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 **punching** **shear**, 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.

Show more
159 Read more

Much research has been dedicated to the study of the **punching** **shear** behaviour of rein- forced concrete **flat** slabs due to the brittleness of the failure. The majority of this past research has been **experimental**, and has involved the testing of isolated slab-column connections, where the portion of the slab included in the test approximates the negative moment area around the column. Even though the existing **experimental** **punching** **shear** database is extensive [1], [2], not all parameters have been sufficiently studied. For example, the **punching** **shear** behaviour of **reinforced** concrete slabs supported on L, T, and cruciform-shaped columns has received limited attention [3], [4] even though most current worldwide design codes include provisions for these column shapes [5], [6]. The derivation and reasoning behind these code provisions are unclear.

Show more
12 Read more

The first set of inclined **shear** cracks appears to have started from near the top **reinforcement** and ended near the column. Even though at the end of testing, it was noticed that the column penetrated into the slab, the first two legs of **shear** **reinforcement** were actually avoided by the first inclined **shear** cracks, which propagated inside the cover. These cracks were more inclined away from the column and appeared to span at least two legs of **shear** **reinforcement**. It can be concluded that substantial yielding and rigid body rotations must be responsible for the apparent penetration of the column into the slab, which explains why the load was maintained during this process. Because there was **shear** failure surface through the concrete in compression, the **shear** resistance of concrete along that surface can be considered to have been adversely affected by **shear** cracking. This assumption appears to be supported by the ACI code of practice, which adopts a reduced concrete **shear** contribution when the slab requires **shear** **reinforcement** (V c in

Show more
48 Read more

For specimen JD9B-E, the cracking pattern occurring between 365 and 600 kN shown in Fig. 10(b) reveals the occurrence of inclined cracks propagating from the slab section to the top and numerous **punching** **shear** cracks developing concentrically around the loading point. Compressive cracks appeared at 648 kN and propagated gradually over the whole width of one deck. However, these compressive cracks did not occur in the deck that was not directly subject to the load. At 676 kN and 733 kN, sudden loss of the load occurred due to **punching** **shear** and, beyond 733 kN, the load experienced small increase [7]. Compared to specimen JD9B-C, the **punching** **shear** cracks show U-shapes rather than closed polygons around the loading plate, and **punching** failure occurred earlier in the case of eccentric loading.

Show more
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 **punching** **shear** 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 **reinforced** concrete are based on **tests** of steel **reinforced** slabs. 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 **reinforced** concrete beams have been evaluated using the large database collected. The **experimental** **punching** **shear** 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 **reinforced** concrete slabs give conservative predictions for the specimens in the database. This paper also presents a simple yet improved model to calculate the **punching** **shear** capacity of FRP- **reinforced** concrete slabs. The proposed model provides the accurate results in calculating the **punching** **shear** strengths of FRP-**reinforced** concrete slender slabs.

Show more
The deflection profiles at the time of reaching the maximum central displacement are shown in Figure 11. Both solutions are computed by the Reissner-Mindlin theory FE method. In case labelled by FE-MR the transverse **shear** **strength** is infinitely large. In both cases elastic transverse **shear** deformations are taken into account. Figure 11 indicates the formation (at an early stage of loading) of **punching** cone. Similarly, the TDOF solutions predict **shear** **punching** under the adopted heavier impact load.

10 Read more

Gross, S. P., Yost, J . R., Dinehart, D. W., Svensen, E. & Liu. N. (2003). **Shear** **Strength** of Normal and High **Strength** Concrete Beams **Reinforced** with GFRP Bars. High performance materials in bridges, Proceedings of the International Conference, ASCE, Kona, Hawaii, pp. 426-437.

47 Read more

the model for PG1 is presented in Fig. 3 ). Eight node multi-layered shell elements ( 34mm 34mm in average) accounting **shear** deformation with reduced integration were adopted for the rein- forced concrete [15] . The slab thickness was subdivided into seven layers according to rebar setup. Three Simpson integration points were used for each layer, yielding a total of twenty-one integration points in total over the slab thickness. The vertical support pro- vided by the columns in the centre of the slabs were modelled using nonlinear non-tension spring elements providing stiffness in compression only as described in the following section. On the symmetry faces, all displacements perpendicular to the cross- sections and rotations were fixed. The column was fixed in the ver- tical direction.

Show more
17 Read more