5332002 - RC Shear Wall Model Implementation and Validation

Sensitivity studies have been conducted to assess the variation in global and local responses to changes in material relations and modeling parameters.

Simulation results for both global and local flexural responses will be obtained using the model and compared with experimental results obtained for moderate-scale shear wall tests, such as those reported by Thomsen and Wallace (1995) and Taylor and Wallace (1995). These studies will be completed and documented.

An important aspect of the project will involve work to address nonlinear shear behavior and the linkage of shear strength degradation with flexural ductility. Experimentally derived load – deformations for shear and flexure published by Massone (2003) will be used to assist the development effort. The model will be implemented into OpenSees and studies will be conducted to validate the results obtained with the model.

Project Title/ID Number	RC Shear Wall Model Implementation and Validation —5332002
Start/End Dates	10/1/02—9/30/03
Project Leader	John Wallace (UCLA/Faculty)
Team Members	Kutay Orakcal (UCLA/Grad Student), Leonardo Massone (UCLA/Grad Student)

Project goals and objectives
The project involves development and calibration of a robust model for reinforced concrete shear walls and implementation of the model into the OpenSees platform. A multiple-component-in-parallel model (or multiple-vertical-line-element model) has been selected for the modeling effort. Cyclic material relations used for reinforcing steel and concrete will be employed, and will address gap opening and closing behavior. Simulation results for both global and local responses obtained using the model will be compared with experimental results obtained for moderate-scale shear wall tests, such as those reported by Thomsen and Wallace (1995) and Taylor and Wallace (1995). An important aspect of the project will involve work to address nonlinear shear behavior and the linkage of shear strength degradation with flexural ductility. The potential to expand the model to address flanged walls by using shape functions to describe nonlinear strain distributions for wall flanges, and sub-elements to model wall openings, will be investigated.
Role of this project in supporting PEER’s vision
Surveys of engineering firms throughout the US have indicated that a very large percentage of buildings contain shear walls (Meigs et al., 1993). To date, the PEER center research program on buildings has focused primarily on advancing our knowledge on the behavior, modeling, and design of older reinforced concrete frames, as well as integrating this work across the research program by using two testbed projects. This project will involve the implementation of a robust, calibrated shear wall model in OpenSees for the use on the testbed projects, as well as other projects.
Methodology employed
A multiple-component-in-parallel model (or multiple-vertical-line-element model) will be used. The model involves use of a plane section assumption and uniaxial springs to model section and wall behavior. To date, the model has been developed and debugged using Matlab. Cyclic material relations used for reinforcing steel and concrete have been developed based on published information. The models address gap opening and closing behavior. Sensitivity studies will be conducted to assess the variation in global and local responses to changes in material relations. Simulation results for both global and local flexural responses obtained using the model will be compared with experimental results obtained for moderate-scale shear wall tests, such as those reported by Thomsen and Wallace (1995) and Taylor and Wallace (1995). An important aspect of the project will involve work to address nonlinear shear behavior and the linkage of shear strength degradation with flexural ductility. Experimentally derived load – deformations for shear and flexure published by Massone (2003) will be used to assist the development effort. The model will be implemented into OpenSees and studies will be conducted to validate the results obtained with the model. Once the model for rectangular walls has been implemented, the potential to expand the model to address flanged walls by using shape functions to describe nonlinear strain distributions for wall flanges, and sub-elements to model wall openings, will be investigated.
Brief description of past year’s accomplishments and more detail on expected Year 6 accomplishments
Sensitivity studies have been conducted to assess the variation in global and local responses to changes in material relations and modeling parameters. Simulation results for both global and local flexural responses will be obtained using the model and compared with experimental results obtained for moderate-scale shear wall tests, such as those reported by Thomsen and Wallace (1995) and Taylor and Wallace (1995). These studies will be completed and documented. An important aspect of the project will involve work to address nonlinear shear behavior and the linkage of shear strength degradation with flexural ductility. Experimentally derived load – deformations for shear and flexure published by Massone (2003) will be used to assist the development effort. The model will be implemented into OpenSees and studies will be conducted to validate the results obtained with the model.		(a) Influence of axial load (b) Model and test results Figure 1. Model sensitivity and comparison with test results Larger View
Other similar work being conducted within and outside PEER and how this project differs
Initial work on shear wall modeling was funded by NSF projects as part of the US-Japan program on hybrid and composite systems (CMS-9632457, CMS-9810012). These projects were completed in August 2001. Since August 2001, additional work has been conducted using funds from UCLA. This project is a natural extension of this work.
Plans for Year 7 if this project is expected to be continued
Once the model for rectangular walls has been developed, calibrated, and implemented into OpenSees, the potential to expand the model to address flanged walls by using shape functions to describe nonlinear strain distributions for wall flanges, and sub-elements to model wall openings, could be investigated.
Describe any instances where you are aware that your results have been used in industry
Since this is a new project, no results are available at this time. However, this project has the potential to provide very valuable information to industry. Current Guidelines and pre-standards do not provide adequate guidance on modeling for reinforced concrete shear walls; therefore, it is expected that the results could see widespread use by industry.
Expected milestones
Implement, debug, and document model and material relations and model sensitivity for flexure in Matlab (nearly complete) Develop C++ code and implement into OpenSees Document OpenSees implementation and conduct validation studies. Interact with Testbed projects to ensure model addresses testbed needs Development and implementation of improved nonlinear shear relations into the model. Linkage of shear strength degradation with nonlinear flexural deformations.
Deliverables
Development of a robust shear wall model for slender walls that incorporates nonlinear shear and flexural behavior. Documentation of the model and model results indicating sensitivity of the results to changes in model parameters and material relations. Calibration of the model with experimental results. Implementation of the model into OpenSees and appropriate user documentation.