A refined component model is proposed to predict the inelastic monotonic response of exterior and interior beam-to-column joints for partial-strength composite steel-concrete moment-resisting frames. The joint typology is designed to exhibit ductile seismic response through plastic deformation developing simultaneously in the column web panel in shear, the bolted end-plate connection, the column flanges in bending and the steel reinforcing bars in tension. The model can handle the large inelastic deformations consistent with high ductility moment-resisting frames. Slip response between the concrete slab and the beams was taken into account. A fibre representation was adopted for the concrete slab to accurately capture the non-uniform stress distribution and progressive crushing of the concrete at the interface between the concrete slab and the column flange. The model is validated against results from full-scale subassemblages monotonic physical tests performed at the University of Pisa, Italy. A parametric study is presented to illustrate the capabilities of the model and the behaviour of the joints examined. Concrete crushing Re-bars yielding Shear yielding Flexural yielding Flexural yielding Gap opening Figure 1. Partial strength beam-column joint studied: (a) configuration; and (b) deformed configuration.structures typically exhibit relatively higher lateral stiffness which permits to more easily satisfy code specified drift limits. Compared to traditional steel structures, more effective beam-to-column joints can also be obtained by making use of the contribution of the concrete slab for resisting bending moments due to gravity and lateral loads [1]. Furthermore, these structures can be built with partial-strength partially restrained beam-to-column joints designed with ductile components that can deform in a ductile manner in case of a strong earthquake. In the common case where beam sizes are governed by drift or alike design criteria, rather than flexural strength requirements, ductile partial strength connections allow the formation of a desirable beam hinging global frame mechanism, with large hysteretic energy dissipation capacity and reduced force demand on the columns [2]. The possibility of using partial strength connections as the main energy dissipative mechanism for the seismic resistance of frames has now been recognized in modern design codes [3][4][5].The behaviour of this type of structures heavily depends on the connection response and a significant portion of the research effort on steel-concrete composite frames with partial-strength beam-to-column joint has been devoted to the development of connection systems and the study of their behaviour under seismic and cyclic loading [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In the framework of two jointed European research projects [20][21][22], a partial-strength beam-to-column joint was proposed for moment resisting frames with partially encased composite columns in which energy dissipation is provided by both the column web panel z...

SUMMARYA multi-level pseudo-dynamic (PSD) seismic test programme was performed on a full-scale three-bay twostorey steel-concrete composite moment-resisting frame built with partially encased composite columns and partial-strength connections. The system was designed to provide strength and ductility for earthquake resistance with energy dissipation located in ductile components of beam-to-column joints including flexural yielding of beam end-plates and shear yielding of the column web panel zone. In addition, the response of the frame depending on the column base yielding was analysed. Firstly, the design of the test structure is presented in the paper, with particular emphasis on the ductile detailing of beam-to-column joints. Details of the construction of the test structure and the test set-up are also given. The paper then provides a description of the non-linear static and dynamic analytical studies that were carried out to preliminary assess the seismic performance of the test structure and establish a comprehensive multi-level PSD seismic test programme. The resulting test protocol included the application of a spectrum-compatible earthquake ground motion scaled to four different peak ground acceleration levels to reproduce an elastic response as well as serviceability, ultimate, and collapse limit state conditions, respectively. Severe damage to the building was finally induced by a cyclic test with stepwise increasing displacement amplitudes.

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SUMMARYThis paper presents the results of a multi-level pseudo-dynamic seismic test program that was performed to assess the performance of a full-scale three-bay, two-storey steel-concrete composite moment-resisting frame built with partially encased composite columns and partial-strength beam-to-column joints. The system was designed to develop a ductile response in the joint components of beam-to-column joints including flexural yielding of beam end plates and shear yielding of the column web panel zone. The ground motion producing the damageability limit state interstorey drift caused minor damage while the ultimate limit state ground motion level entailed column web panel yielding, connection yielding and plastic hinging at the column base connections. The earthquake level chosen to approach the collapse limit state induced more damage and was accompanied by further column web panel yielding, connection yielding and inelastic phenomena at column base connections without local buckling. During the final quasi-static cyclic test with stepwise increasing displacement-amplitudes up to an interstorey drift angle of 4.6%, the behaviour was ductile although cracking of beam-to-end-plate welds was observed. Correlations with numerical simulations taking into account the inelastic cyclic response of beam-to-column and column base joints are also presented in the paper together. Inelastic static pushover and time history analysis

Modern design standards for reinforced concrete (r.c.) buildings allow the achievement of ductile structures, able to globally dissipate seismic energy through the development of plastic deformations located in the dissipative regions (i.e. plastic hinges). The hysteretic capacity of r.c. structures is related to the ability of reinforcing steel bars to sustain many cycles of high plastic deformations without the exhibition significant decrease of strength and stiffness; this condition, typically due to cyclic/seismic action, shall be widely investigated in order to obtain a full and detailed knowledge of the structural behaviour of modern r.c. buildings. In the present paper, elaborated inside the European research project “Rusteel”, the evaluation of the seismic ductile demand on steel reinforcing bars due to real earthquake events was carried out. Representative r.c. case study buildings were designed following the actual European and Italian prescriptions and analyzed using the Incremental Dynamic Analysis technique for the assessment of the behaviour under real seismic events. The elaboration of a simplified mechanical model for the steel reinforcing bars, calibrated on the basis of experimental monotonic and cyclic tests, allowed the evaluation of the effective level of deformation and energy dissipation required by earthquakes and the assessment of the ability of the actual European production to satisfy the effective seismic ductile requirements