# Comparative Assessment of Shear Demand for RC Beam-Column Joints under Earthquake Loading
## 5 Conclusions  
A numerical study was presented considering a notorious benchmark in the context of RC structures against earthquake loading, i.e., the SPEAR frame. This paper focused on shear demand at beam-column joints. Results were obtained using a three-dimensional numerical model validated against past studies addressing the same structure. Beam-column joints were modeled with rigid offsets. Flexural type plastic hinges were assumed to be inelastic sources for both beams and columns. Different methods for structural analysis were employed such as MRSA, NLSA and NLTH, assuming a comparable seismic demand. The obtained shear demands at joints were compared to shear strengths evaluated according to building codes targeted to existing structures. The following conclusions can be drawn:  
1. The shear demand at a beam-column joint being a non-conventional output, a post-process based on nodal moments is needed. Two major hypotheses were made: (i) the internal lever arm at the column face cross section, of the beam, was assumed constant and (ii) the contribution to the horizontal equilibrium of the column's shear was neglected. The last assumption's results are conservative;
2. Shear strength evaluation should be extended to all the beam-column joints in a three-dimensional frame, distinguishing two flexural planes. Significant strength differences might be influenced by (i) the joint type attribute in each flexural plane and (ii) the use of different building codes;
3. The larger safety margin was recognized for corner joints by assigning to them the exterior joint type in both the flexural planes. Larger strength should be expected as a result of the confinement offered by the beams in both directions. Besides, elliptical strength interaction domain results were conservative when compared with NLTH shear demand orbits;
4. Among the reviewed building codes, EC8 produced larger strength predictions than ASCE41-17 and NZSEE2017. The latter produced the lowest ones. Discussion about the strength accuracy was not intended because the compared shear demands represent a condition far from failure;
5. NLSA was proven to estimate the larger shear demand with respect to MRSA and NLTH. Differences were explained as a consequence of the possible inaccuracy of NLSA, using modal combination, in the evaluation of elements' forces. Such evidence needs to be investigated further since NLSA is frequently adopted in the assessment of existing RC structures as a compromise between MRSA and NLTH.  
Conceptualization, A.M.; Methodology, A.M./G.M.; Software, A.M.; Validation, A.M.; Data Curation, A.M.; Writing--Original Draft and Reviews, A.M.; Writing--Reviews, G.M.; Supervision, G.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Data Availability Statement: Data are available upon request.  
Open access publication was financially supported by the Board of the PhD Programme of Structural, Seismic and Geotechnical Engineering at Politecnico di Milano.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
CQC Complete Quadratic Combination  
dofs degrees-of-freedom  
MPA Modal-pushover-Analysis  
MRSA Modal Response Spectrum  
NLSA Non-Linear Static Analysis