Oregon DOTTraining MaterialPushover Analysis

Tanarat Potisuk, PhD, PE, SEPrestressed Concrete Standards EngineerBridge Engineering SectionOregon Department of Transportation

Introduction

Pushover Analysis (Nonlinear Static Procedure) required for SDC D

Pushover Analysis StepsStep 1 – Develop Pushover Analysis model

Step 2 – Define expected material properties

Step 3 – Define section properties

Step 4 – Define hinge properties and assign hinges

Step 5 – Run analyses (2)

Step 6 – Post processing

Step 7 – Determine displacement capacity for 1000 year and CSZE

Step 8 – Determine ductility index for each individual hinge

Step 1Use EDA aka. RSA 3D Model – delete superstructure

Step 1 (cont.)Set bent cap, columns, and foundation – consistent with EDA

Apply girder dead load reactions

Step 1 (cont.)Calculate analytical plastic hinge length

Step 2Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Dc = 72 in. Clr. = 2.5 in.Ds = 66.25 in.

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 2 (cont.)Define material properties, i.e. steel rebar, unconfined concrete, confined concrete

Step 3Define section properties

Step 3 (cont.)Define section properties

Step 3 (cont.)Define section properties

Step 3 (cont.)Define section properties

Step 3 (cont.)Define section properties – curvature unit = 1/in

Step 4Define hinge - global control

Step 4 (cont.)Set load cases

Step 4 (cont.)Define hinge properties

Step 4 (cont.)Assign hinges to elements

Step 5Push two perform analysis buttons

Step 6Observe deformed shape, bending moment and shear diagram, reaction

Step 6 (cont.)Observe pushover curve

Step 6 (cont.)Pushover hinge result – total deformation

One hinge and one section of 3

Step 6 (cont.)Pushover hinge result – plastic deformation

Elem 117 yields at Step 10

Step 6 (cont.)Find reaction, when columns all yield

Step 6 (cont.)Obtain Moment – Curvature data with selected column reaction

Step 7Establish strain limits per BDDM 1.17.3.1

1000-Year “Life Safety” – All Bridges in Oregon

CSZE “Operational” – All Bridges on and West of US97

Step 7 (cont.)Obtain section curvature (1/in) at strain limit

CSZE

1000 Year

Select 1st yielding Hinge

Step 7 (cont.)Obtain solution step to determine the corresponding deflection

Step 10 - 11

Step 7 (cont.)Obtain the deflection at the strain limit

~ 12 in

Step 8Determine member ductility index

Step 8 (cont.)Determine member ductility index

Only for 1000-year return period EQ