BURBANK REGIONAL INTERMODAL Base-Isolated BRITC …BURBANK REGIONAL INTERMODAL TRANSPORTATION CENTER...

BURBANK REGIONAL INTERMODAL

TRANSPORTATION CENTER (BRITC) Owner: Glendale-Burbank-Pasadena Airport Authority

Design Build Team: McCarthy Building Companies / Saiful Bouquet Architect: PGAL

SEAOSC / SEAOC 2017 EXCELLENCE IN STRUCTURAL ENGINEERING AWARDS

PROJECT DESCRIPTION

� BRITC is the most advanced, high-tech transportation hub built in

California

� 300,000 sf Consolidated Rental Car Facility & Customer Service

Building

� Designed to withstand an earthquake larger than any California had

ever experienced

� Provided FEMA and the State of California a new Disaster

Command Center location to mobilize in the event of a major

earthquake or other disaster

SAP2000 Analysis

Computer Model

� Nonlinear Static Analysis with isolators

� Equivalent temperature loading calculated to represent creep, shrinkage and elastic shortening

� Two-Stage Analysis

� Stage 1: Creep, Shrinkage and Shortening from t = 0 to 4 months (Delay Strip Open)

� Stage 2: Creep & Shrinkage from t = 4 months to 5 years (Delay Strip Closed)

� Thermal Analysis: 50 deg. F Temperature Change

STRUCTURAL SYSTEM

� Gravity System

� Post-Tensioned Reinforced Concrete One-Way Floor structure w/

65’ x 65’ column bays and 19’ Story Height

� Steel Open Web Roof structure with capacity to support solar

arrays

� Lateral Force Resisting System

� Base-Isolation (82 Triple Friction Pendulum Isolator Bearings)

� Above Isolators: Special Concrete Moment Frames

� Below Isolators: Octagonal Cantilever Concrete Columns

� Roof: Special Concentric Braced Frames

� Foundations: Pile Caps with Driven Steel H-Piles

Base-Isolated BRITC Serves Dual Purpose asEmergency Response Nerve Center

“BRITC is essentially

the safest place to be

during an earthquake”

DESIGN CHALLENGES

� Ultra fast-tracked project. The entire design and peer review process

including nonlinear response history analysis completed in 4 months.

� Immediate Occupancy (IO) after a Maximum Considered Earthquake (MCE)

� Due to possible shrinkage, the project was built with a Delay Strip and

connected 4 months after completion

� Long Span Frame Structures

CREEP, SHRINKAGE & THERMAL ANALYSIS

Post-Tensioned Concrete BeamsIsolator Installation Isolator & Connector PlatesConcrete Columns Below Isolators

SEISMIC DESIGN CRITERIA (SET BY AIRPORT AUTHORITY)

� Creep, Shrinkage and Elastic Shortening per ACI 209R

SEISMIC PERFORMANCE OBJECTIVES

Building Performance Level

Ea

rth

qu

ak

e H

aza

rd L

eve

l

Collapse

PreventionLife SafetyImmediate

Occupancy

Frequent(43-yr EQ or

50% / 30yrs)

Rare(475-yr EQ or

10% / 50yrs)

Very Rare (2,475-yr EQ or

2% / 50yrs) Burbank RITC

Immediate Occupancy for a Maximum Considered Earthquake (MCE)

Inner Pendulum Motion(Frequent – 43-yr Earthquakes)

Lower Pendulum Motion(Rare – 475-yr Earthquakes)

Upper Pendulum Motion(Very Rare – 2,475-yr Earthquakes)

Main Concave

Cross Section of Triple

PendulumTM Bearing

Slider Concave

COMPONENT

ACTIONMATERIAL STRENGTHS RESISTANCE FACTOR (φ)

Concrete Beam Flexurefy = 1.1 fy,specified

f’c = 1.1 f’c,specified

φ = 1.0

Concrete Beam Shearfy = 1.0 fy,specified

f’c = 1.0 f’c,specified

φ = 1.0

Strong Column / Weak Beam

Evaluation

fy = 1.1 fy,specified

f’c = 1.1 f’c,specified

φ = 1.0

Structural Steel MembersFy = 1.1 Fy,specified

Fu = 1.1 Fu,specified

φ = 1.0

Elements Below

Isolation PlaneSpecified Material Strengths φ per code

STRUCTURAL ELEMENTS SEISMIC FORCES INTERSTORY DRIFT

Structural Elements Above

Isolation System

Essentially Elastic Response

based on MCE demands (R=1.0)2% of Story Height

Isolation System and

Structural Elements Below

Isolation System

Elastic Response based on MCE

demands divided by 0.8 (R=0.8)1.5% of Story Height

Delay Strip

N-S Moment Frames

E-W Moment Frames

Level 2 Floor Plan

SEISMIC ANALYSISA three-dimensional commercial nonlinear analysis software package, SAP2000, was used to investigate the

nonlinear seismic response of the RITC structure utilizing base isolation. The base isolators were modeled

using friction pendulum link elements available in the SAP2000 software package. Since SAP2000 does not

include a specific element that can consider the complex behavior of the triple friction pendulum isolators, a

two-component parallel model based on the work by Sarlis and Constantinou (2010) was used with properties

derived from the actual physical properties of the isolator units from the isolator manufacturer.