nees facilities used: university of nevada, reno university of illinois, champaign-urbana...

NEES Facilities Used:

University of Nevada, Reno

University of Illinois, Champaign-Urbana

INTRODUCTION

Bridge columns are subjected to combinations of

actions and deformations, caused by spatially-complex

earthquake ground motions, features of structural

configurations and the interaction between input and

response characteristics. Combined actions/loadings

can have significant effects on the force and

deformation capacity of reinforced concrete columns,

resulting in unexpected large deformations and

extensive damage that in turn influences the

performance of bridges as vital components of

transportation systems. Current analysis methods,

behavior theories and design practices do not take into

consideration the full range of interactions, due to the

scarcity of experimental data and a lack of behavioral

understanding.

OBJECTIVES

Therefore, the objectives of the project are to develop

a fundamental knowledge of the impact of combined

actions on column performance and system response

and to establish analysis and design procedures that

include the impact. The objectives will be realized by

integrating analytical and experimental research where

physical tests are driven by analyses and simulations

that examine the system response of various bridge

types under different loading conditions, and analytical

models are calibrated by experimental data.

ANALYSIS AND DESIGN PROGRAM

The analysis and design program has the following

outcomes.

Comprehensive analyses of bridge configurations

resulting in guidelines on configurations and input

conditions that increase the likelihood of significant

complex-combined column loading.

Analysis tools for use by researchers and designers

to represent combination loading behaviors. These

will include new rigorous frame elements that account

for the complex three-dimensional behavior of

reinforced concrete (RC) columns under combined

loading and new constitutive models for combined

axial/bending/torsional actions to be used in

conjunction with the new inelastic frame elements.

Behavioral models, simplified analysis and design

tools to be used by engineers. Model and design

methodologies will be developed that address

(i) when engineers must include combination

load effects and

(ii) when they can be neglected.

Tools will include methods for estimating strength and

deformation capacity.

Drive files for the pseudo-dynamic and dynamic

experimental programs at University of Nevada, Reno

(UNR) and University of Illinois at Urbana-Champaign

(UIUC). The analytical work will serve as the driving

tool for conducting and linking the experimental

components of the project.

The outcomes will be realized through the following:

Task 1: Preliminary Analysis of Bridges under

Combined Loadings (UCLA, UIUC)

A preliminary analysis of a series of bridge structures

subject to different levels of earthquake excitations

using existing finite element software packages will be

performed at the first stage of the project.

Figure 1: UMR Experimental Setup

Figure 2: UIUC Experimental Setup

Figure 3: UNR Experimental Setup

Figure 4: V-M-T Interaction Diagram

EDUCATION AND OUTREACH

An integrated education, training and outreach

program has been developed for the project that spans

from 4th graders to practicing engineers. The

education component is being guided by University of

Washington, St. Louis. Modules will be developed for

teachers and professors that can be inserted in their

courses. Modules will be used by the research team

in summer camps, visits to local elementary, middle

and high schools, undergraduate and graduate

courses and in continuing education courses. Specific

programs are targeted towards underrepresented

groups. Summer camps are planned for the summer

2006 at both UNR and UMR.

Seismic Simulation and Design of Bridge Columns under Combined Seismic Simulation and Design of Bridge Columns under Combined Actions, and Implications on System ResponseActions, and Implications on System ResponseInvestigators:

David H. Sanders, University of Nevada, Reno (Principal Investigator)

Abdeldjelil “DJ” Belarbi, University of Missouri, Rolla (co-PI)

Pedro Silva , University of Missouri, Rolla (Investigator)

Ashraf Ayoub , University of Missouri, Rolla (Investigator)

Shirley Dyke, Washington University St. Louis (co-PI)

Amr Elnashai, University of Illinois, Champaign-Urbana (co-PI)

Jian Zhang, University of California, Los Angeles (co-PI)

Sergio Alcocer, University of Mexico, Mexico City (Investigator)

The bridges analyzed in the study will be selected to

represent conditions resulting in high levels of

combined loadings on the piers. The goal of the

analytical study is to study the seismic response of

these bridge systems, including foundations and

surrounding soils, so that the appropriate multi-

directional loading and boundary conditions for

columns can be obtained. The study is therefore

essential for determining the appropriate input

loadings for the specimens tested in the subsequent

phases of the project.

Task 2: Development of Inelastic Models for RC

Sections under Combined Loading (UMR)

This task will focus on developing new constitutive

models for RC under combined axial/bending/torsional

loads in conjunction with available inelastic frame-type

elements. The NEES-supported finite element open

source software OpenSees will be used as the

computational platform and the newly developed

constitutive models will be added to its material library.

The newly developed models will be used for pseudo-

dynamic testing, predicting dynamic columns

performance and for conducting fragility studies

Task 3: Modeling of Specimens under Pseudo-

Dynamic and Dynamic Conditions (UCLA, UMR,

UIUC, UNR)

The newly developed frame elements with calibrated

constitutive models for RC sections will be used to

model and provide input to the pseudo-dynamic

system simulation conducted at UIUC and the dynamic

tests at UNR.

Task 4: Correlation with System Bridge Test (Sanders)

A ¼-scale two-span bridge test was conducted at UNR

as part of NEES Collaborative Research: A

Demonstration of the NEES System for Studying Soil-

Foundation-Structure Interaction will enable both

elastic and inelastic calibration of specific models

developed.

Task 5: Fragility Analysis of Bridge Structures &

Impact of Dynamic Loads (UIUC, UMR, UNR)

The newly developed and calibrated frame elements

will be used to conduct extensive statistical studies

with the purpose of deriving probabilistic fragility

relationships for RC bridges including axial-shear-

flexure-torsion interaction.

EXPERIMENTAL PROGRAM

The experimental program includes quasi-static testing

of twenty-four large columns providing fundamental

behavior including the impact of torsional moments at

University of Missouri, Rolla (UMR) (see Fig. 1),

pseudo-dynamic testing of three large and four small

scale columns with variable axial load, within a bridge

system simulation, at the University of Illinois at

Urbana-Champaign (UIUC) (see Fig. 2), real-time

dynamic testing of eight large scale columns with

bidirectional, torsional and variable axial load inputs at

University of Nevada, Reno (UNR) (see Fig. 3), plus

an integrated experiment with three columns linked

through simulation, conducted at UIUC by UMR. The

tests will work to define the failure surface as seen in

Figure 4. The experimental program is fully integrated

with the analytical program.

Loading Frames

Load Stub

(2) Vertical Actuators

Unit Tie Downs

(2) Horizontal Actuators

Test Unit

Unit Base

Strong Floor/Wall

Test Unit

Tie Downs for (1) Horizontal Actuator

(1) Horizontal Actuator

Loading Frames

Load Stub

(2) Vertical Actuators

Unit Tie Downs

(2) Horizontal Actuators

Test Unit

Unit Base

Strong Floor/Wall

Test Unit

Tie Downs for (1) Horizontal Actuator

(1) Horizontal Actuator