1. Project Goals/Objectives:

Develop improved models for the interaction of axial force, shear and bending moment in metallic members for eccentrically braced frames and energy dissipaters and reinforced concrete members such as columns and bridge piers under cyclic loading conditions.

2. Role of this project in supporting PEER’s mission (vision):

Improve simulation capabilities for seismic condition assessment of existing reinforced concrete buildings; improved performance-based seismic assessment capabilities.

3. Methodology Employed:

Structural members yielding in shear are used in earthquake resistant systems, such as eccentrically braced steel frames and systems with passive energy dissipation devices, in a conscious effort to concentrate the energy dissipation capacity of the structure in components that can be repaired or replaced after a major earthquake. The simulation of the energy dissipation capacity of these components is important in the evaluation of the seismic response of these structural systems. This paper presents a new beam element for the simulation of the hysteretic behavior of shear-yielding members. The element is based on a three-field variational formulation with independent force, displacement and deformation fields. The displacement field is based on Timoshenko's shear beam theory. The nonlinear response of the element arises from the integration of biaxial stress-strain relations over several control sections along the element length. The biaxial material model accounts for the interaction between normal and shear stress. While previous concentrated plasticity models involve parameter tuning for different loading and support conditions, the proposed model is general in its derivation of the axial force-shear-flexure interaction from the material response. The proposed model shows the characteristic advantages of force-based beam elements and is capable of simulating the inelastic response of short beams with a single element without suffering from shear locking. The effect of shear is significant in these members during the elastic and inelastic response. The ability of the model to accurately represent the hysteretic behavior of short shear-yielding members is ascertained with correlation studies of analytical results with available experimental data from shear-link experiments. One such correlation is shown in the following figure.

The model is presently being extended to reinforced concrete members starting with monotonic response. Some preliminary results from the classic beam tests by Bresler-Scordelis are shown in the following figures.

4. Brief Description of past year’s accomplishments (Year 6) & more detail on expected Year 7 accomplishments:

5. Other Similar Work Being Conducted Within and Outside PEER and How This Project Differs:

6. Plans for Year 8 if project is expected to be continued:

Cyclic loading extension.

7. Describe any actual instances where you are aware your results have been used in industry:

OpenSees application of reinforced concrete beam-column element in current evaluation studies.

8. Expected Milestones & Deliverables:

RC Beam-column element with shear interaction capability.