From the hundreds of shear tests that have been performed in previous studies, few are tests that have been performed on lightweightconcrete. For this analysis two different compiled databases were actually investigated. An older database of concrete girder tests which used many of the papers mentioned previous were of normal weight concrete. However these older papers did also have tests on lightweight girders that weren’t recorded in the database. These values were looked at and chosen based on the accuracy of the tests and failure mode. Another current large database compiled by Reineck, Bentz, Kuchma, and Bayrak is also available to the research committee. This database was a joint effort between European and American researchers. After looking at the ACI published database titled “ACI-DAfStb” most if not all tests were also shear tests on normal weight concrete. This cannot be confirmed because the authors would not respond to communications. Due to these setbacks a database of 95 lightweightconcrete bridge girder tests were compiled separately. Table 2 shows all compiled test data for
Four lightweightreinforcedconcreteshear wall specimens were constructed and tested to investigate the influence of diagonal web reinforcement on the hysteretic response of structural lightweightconcreteshear walls. All walls had a barbell-shaped cross section with a web thickness of 100 mm and 250x250 mm boundary elements. The overall length of the cross section was 1500 mm. Vertical and diagonal reinforcement was anchored in a 600 mm thick base girder that was bolted to the laboratory floor. A 250 mm wide by 500 mm deep beam was cast on top of the wall panel, and a hydraulic actuator was attached to the specimen at mid depth of the top beam. Lateral loads were applied 2150 mm above the base of the wall.
ACI 318-11 7 recommends a modification factor to account for the reduced shear transfer contribution of LWC owing to the softened aggregate interlock at inclined crack interfaces. This modification factor was introduced by Ivey and Buth 8 based on a regression analysis of limited 26 LWC beam specimens. However, the accuracy and reliability of this modification factor remain controversial, and their application can be problematic because of a lack of mathematical consensus on shear transfer mechanism along crack interfaces in LWC elements. Yang et al. 5, 6 showed that the modification factor specified in ACI 318-11 is unconservative for the LWC continuous beams tested and the lack of conservatism increases as the maximum aggregate size increases. Therefore, a more rational analytical model for the modification factor would be welcomed to reasonably explain the reduced friction properties along crack interfaces of LWC beams.
kip. Figure 4-26 indicates that, beam G1-C60 and G1-M100 has a higher V c , compared with G1-M0 due to the higher concrete compressive strength used for these beams. It is observed that the beams reinforced with MMFX stirrups, G1-M80 and G1-M100 display a linear slope up to strain of 0.01 and then follow the non-linear behavior of MMFX steel as shown in Figure 4-3 and Figure 4-4. It can be seen that at any given load, the strains in all the beams are almost the same i.e. even though beams reinforced with MMFX stirrups have lesser transverse reinforcement ratio compared with beams reinforced with Grade 60 steel, they have approximately similar stains at a given load. This is due to constant elastic modulus of MMFX bars. Within the elastic range, the value is same as conventional steel.
Twelve low aspect ratio, rectangular reinforcedconcrete (RC) walls were constructed and tested at the University at Buffalo to characterize their inelastic behaviour under reversed cyclic loading. One of the objectives of the research project was to develop equations for peak shear strength suitable for inclusion in seismic codes and standards. New equations for peak shear strength of rectangular walls, without and with boundary elements, are presented in this paper, based on internal force-resisting mechanisms measured during the experiments.
Discrepancies exist between UK design codes for the prediction of pile cap shear strength. A series of reduced scale pile cap experiments to investigate shear strength have been performed. Results from seven samples are presented. Details of test methodology and procedure are shown. Final crack distributions show that pile caps under wall load behave close to simply supported two- dimensional deep beams, except for hogging cracks over the pile head indicating the existence of moment restraint at the piles. Results for failure load indicate that pile cap shear strength is at least two to three times higher than current code predictions from semi-empirical formulae. The truss method is shown to be more reliable to predict pile cap shear strength than bending theory. Keywords: pile cap; shear; truss method; shear enhancement factor.
Genikomsou and Polak  presented a finite element model for the slab specimen SB1 with the damaged plasticity model parameters of: dilation angle of 38 o , shape factor of 0.67, stress ratio of 1.16, and eccentricity of 0.1. A stress vs crack opening displacement approach was used to simulate the tensile response of the concrete. The fracture energy was calculated as 0.9 N/mm according to the CEB-FIB Model Code 1990 . This model only specified tensile damage parameters. A static analysis approach was used in ABAQUS/Standard with a viscosity, μ taken as 0.000085 and then compared to a quasi-static analysis with the dynamic procedure of ABAQUS/Explicit at a very slow rate of velocity. As shown in Figure 2-18, both analysis procedures compare well with the experimental results. The quasi-static analysis shows a noticeable downward trend which was interpreted by the authors as the point of punching shear failure. The static analysis does not show this same downward trend and thus it is not clear how the authors determined that punching shear had occurred and why the curve was cut-off at a deflection of 15 mm. The authors conducted a parametric study on the sensitivity of the viscosity parameter. Figure 2-19 shows the influence of the viscosity parameter on the load-deflection response. The graph shows that the higher the viscosity parameter the stiffer the load-deflection response. The authors also used the FEA model to show the influence that the flexural
EC 2 also specifies shear provisions for slender and deep beams using empirical equations and strut-and-tie models, respectively. The equations for slender beams without web reinforcement con- sider the influence of concrete strength, dowel action of longitu- dinal reinforcement and size effect, whereas neglect the effect of shear span-to-depth ratio as given by Eq. (10). Unlike Eq. 3 (see Table 3) used by KBCS and ACI318-05, EC2 requires that the shear capacity of slender beams requiring web reinforcement is determined from the shear transfer capacity of only web rein- forcement ignoring the contribution of concrete. The shear trans- fer capacity of vertical web reinforcement is obtained from variable- angle truss model; however, the slope of diagonal cracking planes is limited between 21 o (cot θ = 2.5) and 45 o (cot θ = 1.0).
practical bridges, previous studies have focused on the resistance capacity of the structural elements in shear and bending moments for straight bridges. In particular conditions, the eccentric loading can generate torsional moment, which is sometimes disregarded by engineers. However, for curved bridges, apart from shear and bending moments, the torsional moment should be taken as well in view of its importance in design.
Since the problem is dominated by material properties, most studies related to shear are experimental. However, experimental work is expensive and usually limited by the size of the facilities, the type of member or design parameters investigated in a particular set of experiment. Results from shear tests are notoriously variable and often contradictory; furthermore, most published data do not provide sufficient detail for the in-depth investigation of the shear mechanism. Despite this, all current shear design procedures, such as Eurocode (EC2)  and ACI 318-14  code, are based on statistical best fits of experimental data. The inadequacy of these empirical shear design procedures is more pronounce in non-flexural and shear critical members such as deep beams. Numerous theoretical approaches have been proposed to explain the shear mechanism such as the truss analogy theory [5, 6], the variable angle truss model , the theory of shear resistance of RC beams by Kupfer et al.  the modified compression field theory  and strut-and-tie model [10, 11]. The shear strength predicted according to these theories is in general more reliable than that of empirical procedures but there are still parameters that need to be further investigated such as effectiveness factor of concrete used in strut- and tie model.
Abstract: In this study, we propose a new equation that evaluates the shear strength of beam–column connections in reinforcedconcrete and steel beam (RCS) composite materials. This equation encompasses the effect of shear keys, extended face bearing plates (E-FBP), and transverse beams on connection shear strength, as well as the contribution of cover plates. Mobilization coefﬁcients for beam–column connections in the RCS composite system are suggested. The proposed model, validated by statistical analysis, provided the strongest correlation with test results for connections containing both E-FBP and transverse beams. Additionally, our results indicated that Architectural Institute of Japan (AIJ) and Modiﬁed AIJ (M-AIJ) equations should be used carefully to evaluate the shear strength for connections that do not have E-FBP or transverse beams.
3. 1. General As mentioned in Sec. 1, a macro model of a shear wall contains a wall being linear throughout and a nonlinear rotational spring being concentrated at the base of wall to represent the moment-rotation behavior. Such a model is a simple and fast computational tool for calculation of the general lateral behavior of such a wall with much less effort compared to the micro and meso models discussed. Of course, such a tool cannot be used for calculation of local behavior. In this section, first the macro model of this study, is developed for nonlinear static analysis. Since good accuracy and computation speed of the fiber analysis were established in the previous section, and regarding the large number of shear walls, accuracy of the developed macro model will be shown in comparison with the meso model.
used to strengthen an existing structure. Twelve T-beams, two of which were maintained as a control, were tested. The beams had the following dimensions: 152 mm × 381 mm × 2743 mm. They were retrofitted with U-wrapped continuous FRP fabric in one or two layers with and without anchorage. Of the ten strengthened beams, eight were retrofitted with CFRP and the remainder with aramid composite. For the anchorage, the authors used the technique described by Khalifa et al. (2000). In addition, the small longitudinal steel reinforcement ratio led the authors to strengthen the beams in flexure in order to inhibit any premature failure in flexure. The flexural strengthening was applied to both critical positive and critical negative moment regions. The beams were tested under three-point loads with the load applied at distance 2.4 m from the support. In the beams with no anchorage, failure occurred by premature debonding of the FRP, accompanied by severe delamination. The gain in shear resistance was 11% to 16%, depending on the number of FRP layers. The beams with anchored FRP achieved higher gains, ranging from 35% to 27%, depending on the number of FRP layers. Failure in this case was caused by loss of anchorage. The addition of a second CFRP layer to the specimens with anchorage did not result in a capacity increase. The authors noted that the gains achieved are small compared to those predicted by theory. This behaviour was attributed to deep beam action by the authors, who strongly recommended further investigation into this phenomenon. It must be said that an a/d ratio of 2.4 is at the upper limit of what can be considered as a deep beam. It must also be noted that the resistance of concrete in compression was around 20 MPa. The quality of the concrete substrate could also explain the results obtained. In this context, it would have been interesting to know more details on the state of the concrete substrate and on the surface preparation prior to application of FRP.
mm and a span length of 1770 mm, while the simply supported span was 1470 mm. A shear span to effective depth ratio of 3.5 was used. This study was found to be stimulating, as it fixated on something, which was quite different as compared to all other studies in the same scope. An assessment of the ability of crimped and hooked-end steel fibres to be used as minimum shear reinforcement in RC beams prepared with two different grades of concrete was completed. To accomplish this, the control samples were made from the beams, which were believed to be satisfactory. The fibre-reinforced beams also showed fluctuating degrees of multiple cracking at ultimate loads. The shear strength of the FRC beams was found to be more than a low value endorsed in the literature. The grade of concrete was found to be of little importance in this regard. A comparison of the strength of the two types of deformed fibres revealed that the beams reinforced with the hooked-end fibres were found to have up to 38% higher shear strength than the crimped fibres. A simple model for shear strength was also suggested for the calculation of the behaviour of fibre reinforcedconcrete. The proposed model was tested along with seven other shear strength models. The seven models were selected from the literature. The proposed model predicted fairly good values. However, a model proposed by other researchers from the selected literature was found to be projecting a better approximation. Imam et al. (1995) presented an analytical model for predicting the shear strength of reinforced high-strength concrete beams. The dimensions of all the specimens were constant and valued at 200 mm × 350 mm. All beams had span length of 3600 mm. All specimens were singly reinforced without stirrups. The author classified the beams into four groups based on three factors (a/d, V f , and ) in different levels. These beams
19 aggregate interlock. The effect that course aggregate size has on the shear strength has also been explored in the work of Bazant and Kim (1984) in which fracture mechanics was used to develop a theoretical model that included this parameter. As previously stated, the concrete compressive strength has a significant effect on the mechanism of aggregate interlock, coining the more current term “interface shear transfer”. When high strength concrete is used in the construction of structural members, the strength of the cement matrix may exceed the strength of the course aggregate, resulting in shear cracks that pass through the aggregate. Consequently it is believed that increasing concrete strength causes a reduction in interface shear transfer due to a relatively smooth cracked plane (NCHRP, 2005). The research conducted by Angelakos et al. (2001) confirms this and also suggests that increasing concrete cylinder strength does not necessarily result in increased shear resistance. In fact, for members without transverse shear reinforcement, the margin of safety against shear failure decreases significantly with increased cylinder compressive strength. In addition, the margin will continue to become smaller as the longitudinal reinforcement ratio decreases and member size increases (Angelakos et al., 2001).
A composite beam is composed of a steel beam and a concrete slab. These two members behave monolithically by means of shear connectors welded on the upper flange of the steel beam. Studs are widely used as shear connector. The structural behaviour of the composite beam depends on the degree of composite action developed by the shear connector at the steel-concrete interface. This composite action mainly governed by the type of shear connector and the degree of shear connection plays a decisive role as much as the material properties of the steel beam and concrete slab on the strength and stiffness of the composite beam. The horizontal shear behaviour at the steel-concrete interface of the composite beam that is, the shear strength and stiffness of the stud, is determined experimentally on a simplified push-out test specimen rather than on the composite beam itself (Fig. 1). A survey of previous research results on this topic reveals the difficulty to compare thoroughly the estimated shear behaviours among the push-out test specimens that have been fabricated in partially different shapes. However, the evaluation method is recently and gradually gaining popularity in USA and several European countries owing to the standard push-out test proposed by Eurocode 4.