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This paper reports results from four large-scale interior beam column connections without transverse beams or slabs tested under reversed cyclic displacements. The specimens, which included the first of interior beam-column connections constructed with Grade 100 (690) reinforcement with bar deformations similar to those available in U.S. practice, had Grade 60 or 100 (420 or 690) bars, 4 or 10 ksi (28 or 69 MPa) concrete, and varied column depthto-beam bar diameter ratios. The specimens all exhibited strengths greater than the nominal strength, retained at least 80% of their strength to drift ratios exceeding 5%, and exceeded ACI 374 acceptance criteria at a 3% drift ratio for components of special moment frames, demonstrating that well-detailed joints constructed with high-strength materials behave satisfactorily. The data add evidence that joints constructed with high-strength concrete exhibit less bond decay, and recommendations are made for accounting for this effect in design. Results from the specimen constructed with normal-strength materials, considered in the context of prior tests, suggest a need to increase the minimum joint depth for special moment frames. Considerable improvement in behavior associated with reduced bond damage within the joint is obtained from a 20% increase in the minimum column depth-to-beam bar diameter ratio required in ACI 318-19.

One-story concrete moment frame buildings present critical joints because free horizontal faces reduce their confinement in the core, affecting the anchorage of the top beam reinforcement and producing joint distress. In addition, precast concrete processes that involve prestressed beams with different shapes, precast concrete columns, construction of joints on the jobsite, and special construction details such as a reinforced topping on top of the beam joints could affect the seismic performance of one-story precast moment frames for industrial buildings. Due to the lack of experimental testing, six full-scale critical connections were cyclically tested to allow understanding of their seismic performance. Test specimens include one precast reinforced column, three knee joints, and two interior joint sub-assemblages that were designed based on ACI 318. All connections sustained at least a 3.5% drift ratio with no beam longitudinal reinforcement bar rupture or buckling and very low or no observed damage of the column and minimal joint distress, which is consistent with the strong-column/weak-beam design philosophy. The performance acceptance criteria of ACI 374.1 was satisfied by all test specimens in terms of stiffness, strength, and energy dissipation. Nonetheless, the presence of the reinforced topping slab on the top of the joint plays a role in achieving slightly better strength, ductility, and hysteretic performance response.

The effect of various factors on the contribution of slabs to the seismic performance of beam-column joints in steel-reinforced concrete (RC) frames has been extensively investigated. However, no research data is available on the behavior of beam-column slabs reinforced with alternative materials such as glass fiber-reinforced polymers (GFRPs). To fill this gap, two full-scale GFRP-RC exterior beam-column slabs were tested under reversal loading to investigate their seismic performance with a focus on the effect of lateral beams on the effective slab width. The results were compared with two previously tested beam-column specimens. Moreover, a series of finite element models were generated to determine the influence of lateral beams’ size and slab thickness on the contribution of slabs. The results indicated that the contribution of cast-in-place slabs in the bending moment capacity of the main beams when the top fiber of the slab is in compression is insignificant.

The joint performance of concrete slabs has a significant role in the development of faulting and fatigue cracks in full-depth concrete pavements and overlays. The joint performance refers to the load-related responses of a concrete pavement slab relative to its adjacent slabs. The higher the joint performance, the longer the life of the concrete pavement. The joint performance between the concrete slabs of undoweled joints or across cracks is achieved through aggregate interlock, which largely depends on the concrete strength, crack width, and crack surface texture. The use of structural fibers also influences the crack width, aggregate interlock, and, overall, the joint performance. The objective of this study is to develop an affordable small-scale joint performance test method so that the contribution of the concrete constituents and fibers, if used toward, can be quantified during the concrete mixture design stage. This will enable a better prediction of the life the concrete pavement. The proposed method uses 152 x 152 x 610 mm (6 x 6 x 24 in.) beams to characterize the joint performance of the concrete.

Six one-way reinforced concrete slabs, simply supported along the short sides by means of corbels (dapped ends), were recently tested for bending and shear behavior in Milan under two different crosswise load distributions and with three partially different reinforcement layouts in the supporting corbels and in the main body (size 2200 x 1300 mm [7.22 x 4.27 ft]; thickness/length ratio close to 1/14; corbel depth and overhang/length ratio close to 1/23). The tests in bending under the service loads and in shear up to and beyond the peak load show that load crosswise-distribution plays a minor role. In shear, the quite complex crack patterns in the D-regions close to the dapped ends clearly indicate the formation of very effective strut-and-tie systems if the bottom bars of the main body are bent up, and of shallow arch-and-tie systems if the same bars are straight. In the former case, a proper introduction of the bond along the tension bars of the corbels is a must to define the position of bond-related joints and to make strut-and-tie models more reliable in predicting the bearing capacity, while in the latter case, the design equations provided by the codes for constant-section shear-unreinforced beams (ACI 318, EC2, and fib Model Code 2010) prove to be adequate also in the case of corbels.