Project Title/ID Number Evaluation and Application of Concrete Tilt-up Assessment Methodologies—509
Start/End Dates 4/1/03 – 3/31/04
Project Leader James Malley (Degenkolb/I)
Team Members Tim Graf (Degenkolb/I), Jack Hseuh (Degenkolb/I)

F=faculty; GS=graduate student; US=undergraduate student; PD=post-doc; I=industrial collaborator; O=other

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1. Project Goals/Objectives:

Task 1
The goal of Task 1 is to provide input to existing codes (e.g. International Building Code) and guidelines (e.g. FEMA 356) that will improve the seismic assessment methodologies of concrete tilt-up and other low-rise, rigid-wall, flexible diaphragm buildings. The input will be based on research findings and results of previous (PEER) research projects on concrete tilt-up buildings.
These research projects are:

  1. Seismic Response of Tilt-up Buildings by John F. Hall;
  2. Modeling and Evaluation of Tilt-up and Steel Reinforced Concrete Buildings by John W. Wallace;
  3. Stiffness of Timber Diaphragms and Strength of Timber Connections by Gerard C. Pardoen; and
  4. Improved Methodology for Evaluating the Seismic Resistance of Low Rise Buildings with Flexible Diaphragms by Jim Anderson.

Task 2
As practicing structural engineers, we will apply the building assessment methodology developed in PEER Task 507, Advanced Seismic Assessment Guidelines by C. Allin Cornell, Paolo Bazzurro, Charles Menun, Maziar Motahari, to a concrete tilt-up building in the Pacific Gas & Electric (PG&E) building inventory. The selected building is the PG&E Fremont Materials Distribution Center, which Degenkolb Engineers has previously performed both seismic and nonstructural upgrades for.

Predicting the post-earthquake functionality of utility structures is a crucial step in evaluating the likelihood that the PG&E power distribution network will not be able to provide power to customers. The final product of the guidelines is a set of fragility curves for structural limit states directly related to post-earthquake building occupancy status; namely green, yellow, or red tags.

The objectives are to:

  1. Identify potential difficulties that Structural Engineers would encounter in using the procedure described in the Advanced Seismic Assessment Guidelines;
  2. Recommend possible revisions to the procedure to address any identified difficulties; and
  3. Identify and make recommendations on other issues related to assessing the seismic reliability of utility structures and systems.

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

The project is a key step in investigating the practical application and potential of performance-based seismic assessment methods. As such, the project will lead to the wider application of seismic and structural engineering procedures that use these state-of-the-art techniques.

3. Methodology Employed:

The Nonlinear Static Procedure (NSP) is performed on the structure using SAP 2000, commercially available software frequently used by practicing structural engineers.

Incremental Dynamic Analysis (IDA) is performed using the SPO2IDA spreadsheet tool developed by Vamvatsikos and Cornell.

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

Task 1
Each of the four reports was reviewed and summarized. The data from the reports was evaluated to test the validity of design procedures and see what changes, if any, could be made to current design methodologies. Each report raised questions regarding assumptions and procedures in the research process, and the questions are presented for the authors. The reports also illuminated ideas for further research in the area of tilt-up building construction. From the four report evaluated, some suggestions are presented for changes in design. However, no major changes to the current codes and guidelines were recommended due to this study. The Task 1 draft report is being reviewed.

Task 2
A 2D Static Pushover Analysis was performed on the roof diaphragm of the selected building for the intact structure and several damage states. The development of the IDA curves and subsequently, the fragility curves, based on these results are underway. At the same time, difficulties associated with using the Guidelines and possible revisions are being identified. Eventually, recommendations on other issues related to assessing the seismic reliability of utility structures and systems will be made.

figure 1
Figure 1: 2D Model of Roof Diaphragm with Diaphragm Represented by
Axial Elements with Nonlinear Hinges

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

Within PEER, this project is integrally related to Task 507, the development of the Advanced Seismic Assessment Guidelines. Task 508 is similar to Task 2 of this project in its investigation of the use of the Guidelines, in which a steel moment frame building was studied. This project applies the Guidelines to a different type of construction, a concrete tilt-up building with a flexible diaphragm.

The reports reviewed in Task 1 were PEER projects concerned with experimental and analytical studies of concrete tilt-up buildings. This project seeks to summarize these studies and to make further recommendations for research as well as practice.

Outside PEER, two other related documents include:

  1. Guidelines for Seismic Evaluation and Rehabilitation of Tilt-up Buildings and other Rigid Wall/Flexible Diaphragm Structures by the Structural Engineers Association of Northern California; and
  2. FEMA 356, Prestandard and Commentary for the Seismic Rehabilitation of Buildings. These documents have not fully incorporated all of the findings from the previous PEER studies. Also, the application of the Guidelines offers an advanced tool for the post-earthquake assessment of tilt-up buildings that has never been used in practice.

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


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

None to date.

8. Expected Milestones & Deliverables:


Task 1: Prepare a report summarizing the findings from previous research with the objective of providing recommendations on code and guideline changes.

Task 2: Prepare a report describing the test application and its results, other applicable comments and recommendations, and possible recommendations on assessing seismic reliability of utility structures.


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