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This paper focuses on the evaluation of bi-axial shear demand for reinforced concrete (RC) beam–column joints assuming: (i) the SPEAR frame as a benchmark; and (ii) different structural analysis methods which share the same seismic input. A numerical model was implemented using lumped plasticity. The joints were modeled as rigid offsets of beams and columns. The shear demand at a joint is evaluated as a post-process of the beam’s nodal moment. The discussion focuses on the differences between the estimated shear demand considering modal-response-spectrum analysis (MRSA), non-linear static analysis (NLSA) and non-linear time history (NLTH). Strength assessment of joints is discussed as well. Significant strength differences were recognized by using different building codes targeted to existing structures which, in general, behaved on the safe side. The elliptical shear strength domain resulted in being conservative when compared to NLTH shear demand orbits. NLSA, using modal combination, proved to estimate the larger shear demand with respect to MRSA and NLTH.

The effect of bearing pressure on the behavior of cast-in anchors is addressed presenting the results of an experimental campaign on cast-in anchors with different head type and same embedment depth. In particular, three cast-in anchor solutions were tested with the anchor-head ranging from relatively small head (high bearing pressure) to very large head-size (low bearing pressure). For the small head-size only, the anchor is installed using high strength grouting mortar after the hardening of the base concrete material. The concrete base member was lightly reinforced. Anchors were tested under axial force and different mechanical response (load-displacement) are observed. Failure modes change depending on the anchor's type. The force transfer mechanism might migrate from pure concrete cone formation to structural collapse of the concrete base member. In some cases, the cone surfaces can be clearly recognized despite of the presence of a splitting crack. In other tests a plate failure was obtained, characterized by the presence large triangular segments between cracks radially arranged. This aspect is strictly related to the bearing pressure at the anchor-head location. Indeed, a hydrostatic stress-strain field is developed with different gradients according to the head-size. Small head-size leads to an increasing of the bearing pressure with severe crushing of concrete and consequent reduction of the expected load capacity. Furthermore, the observed failure mechanism suggests that the crack pattern propagation is unaffected by the presence of grouting mortar.

It is generally acknowledged that one of the most critical tests to capture the behavior of a post-installed fastener under seismic action is the so-called “seismic crack movement test,” which consists in applying a constant load to a single fastener installed in a crack subjected to opening and full closing cycles. This article presents experimental results of crack movement tests on large size post-installed anchors that show a strong influence of the geometry of the concrete specimen in which the anchor is installed. To improve the regularity of the crack plane, a feedback control using the crack opening signal is applied to the servo-hydraulic actuators. Results of seismic crack movement tests using two different test setups were compared. The major aspects are as follows: (i) splitting force generated by the anchor affects the restoring of the zero crack opening when increasing the number of cycles, and (ii) increasing the size of concrete element limits the effects of bending induced in the concrete specimen. The issue of residual crack opening at the zero actuator’s load is observed experimentally and is further approached both analytically and numerically. The parameters that mostly affect the crack closure phase, i.e., steel ratio, transfer length, and de-bonding length, are finally discussed.

This paper addresses the stress field of reinforced concrete (RC) beam–column joints retrofitted with haunches. Design of such solution currently assumes internal forces evaluated by the so called β‐factor approach, which was originally conceived targeting the enhancement of steel moment‐resisting frames. Extension to RC is subsequent as it emerges from the literature survey. The analytical model is first critically rediscussed. Inconsistencies of the adopted structural scheme, with respect to the actual mechanical behavior, may lie on the compatibility conditions which are imposed between the haunch and concrete beam (or column). In this regard, two‐dimensional finite element models (FEM), using linear‐elastic materials, are employed to study the stress field of two benchmark specimens derived from literature. A partial validation is carried out against experimentally derived internal forces. Results show that, for haunches with extended flat plates and stiff diagonals, compressive diffusion affects the entire haunch region. Consequently, beam's kinematic hypothesis of linear strains is no longer valid. The predicted joint shear demand resulted underestimated by β‐factor approach by 50%. Since 2D FEM may be not efficient for many practical circumstances, an application of Strut‐and‐Tie is alternatively proposed. Finally, both the limitations and possible extensions of the proposed approaches are stated transparently.