Performance Based Engineering Solutions

WHY USE PERFORMANCED BASED ENGINEERING (PBE)? Equipped with a comprehensive model of the existing building and

knowledge of the seismic hazard, the PBE approach allows us to

answer some important questions, such as:

• How well does an existing or unstrengthened building perform

(how much damage) in a large earthquake?

• What percentage of the design earthquake or other level of

seismic load can the existing building resist prior to the onset of

significant damage?

• How could a seismic strengthening scheme be most effectively

targeted to reduce damage or mitigate collapse hazards?

By actively engaging key stakeholders such as the client or building

owner, the design team and building officials, performance objectives

are selected for a specific seismic hazard during the evaluation or

rehabilitation phase in order to satisfy the project’s objectives. It is also

possible to target different performance objectives for different level

seismic events. Common project design objectives are:

• Voluntary seismic strengthening (limited rehabilitation) to

mitigate critical life safety or collapse hazards.

• Conformance with the Basic Safety Objective (equivalence with

building code for new construction).

• Damage reduction or contents protection under small to

moderate seismic events.

“How will my building perform during the next big one?”

BENEFITSPerformance Based Engineering provides significant benefits to the

seismic evaluation and rehabilitation of existing buildings:

• A better understanding by all stakeholders of expected building

performance and project objectives.

• Seismic rehabilitation solutions that are complimentary with the

existing structural systems.

• Solutions that are more compatible with programmatic

requirements, architectural intent or historic fabric of the existing

building.

• Safer, more resilient and economical retrofits.

PBE computer model for the Cathedral Building, Oakland CA

SEISMIC REHABILITATION OF EXISTING

& HISTORIC STRUCTURES Holmes Culley has extensive seismic evaluation and strengthening

experience on numerous structures in the San Francisco Bay Area and

beyond. We believe that all existing buildings have inherent value.

Above all, the reuse of existing buildings is one of the most sustainable

practices in the construction industry.

Seismic strengthening, where required, can be sensitive to the existing

building by discovering, analyzing and quantifying the contribution of

existing seismic load resisting elements. Our philosophy is to augment

rather than replace if additional capacity is required to provide

enhanced life safety or property protection. In addition, we are always

conscious of the need to consider the building’s function and historic

or architecturally significant fabric when locating and detailing any

structural strengthening.

Our role in the assessment and potential strengthening of existing

structures is to obtain and understand input from relevant stakeholders

and their intended goals for the project to better guide our approach.

These include the building owner, end users, local community, and

building officials. Our understanding of stakeholder needs and

goals coupled with comprehensive structural analysis enables us to

make thoughtful and pragmatic recommendations to best achieve

the performance objectives and ensures that all stakeholders receive

a successful project. While traditional prescriptive building codes

generally limit or preclude such considerations, Performance Based

Engineering (PBE) provides the framework to implement this approach.

FIGURE 1

TYPICAL PROJECTS THAT BENEFIT FROM PBE

MARINE STRUCTURES; Hysteretic Energy Dampers for SubstructurePiers 1.5, 3 & 5, San Francisco, CA

HISTORIC BUILDING REHABILITATION; Substructure & Superstructure Rehabilitation Piers 1.5, 3 & 5, San Francisco, CA

APPROACH Consider inherent strength of existing, archaic materials

Evaluate performance for different seismic hazards or scenarios (for new, existing or

rehabilitated conditions)

PRESCRIPTIVE/TRADITIONAL CODE No (often) No

PERFORMANCE BASED ENGINEERING Yes Yes

TRADITIONAL CODE BASED APPROACH VS. PERFORMANCE BASED ENGINEERING (PBE)

SMALL AND FREQUENT

1989 Loma Prieta e/qMagnitude 6.9 60 miles away from San Francisco

Magnitude 7.2 San Francisco PeninsulaFault,10 miles from downtown San Francisco

1906 e/q Magnitude 7.9as felt in San Francisco

RARE AND LARGE

VERY RARE AND EXTREME

EART

HQ

UA

KE IN

TEN

SITY

PERFORMANCE

CODE

Immediate Occupancy Life Safety Collapse Prevention

PRESCRIPTIVE DESIGN GOAL

CODE

TYPICAL PROJECTS THAT BENEFIT FROM PBE

STRENGTHENING OF EXISTING BUILDINGS; Cathedral Building, Oakland, CA

IMPROVING RESILIENCE OF NEW & EXISTING CONSTRUCTION; Voluntary seismic strengthening & mitigation for existing apartment tower, Pacific Heights, San Francisco, CA

TRADITIONAL CODE BASED APPROACH VS. PERFORMANCE BASED ENGINEERING (PBE)

SMALL AND FREQUENT

1989 Loma Prieta e/qMagnitude 6.9 60 miles away from San Francisco

Magnitude 7.2 San Francisco PeninsulaFault,10 miles from downtown San Francisco

1906 e/q Magnitude 7.9as felt in San Francisco

RARE AND LARGE

VERY RARE AND EXTREME

EART

HQ

UA

KE IN

TEN

SITY

PERFORMANCE

CODE

Immediate Occupancy Life Safety Collapse Prevention

PRESCRIPTIVE DESIGN GOAL

CODE

OLDER, UNSTRENGTHENED BUILDINGS

Pier 35 marginal wharf retrofit concept with hysteretic dampers, San Francisco, CA

Adopt alternative performance objectives (new or existing buildings)

Utilize alternate non-prescriptive technologies & irregular systems Requires peer review

No No No (usually)

Yes Yes Yes

What’s Involved

• Hysteretic dampers• Viscous damping• Seismic isolation• Rocking & restoring (self- centering) systems - Rocking wall piers & columns - Uplifting foundations• FRP strengthening of URM walls

• Based on ANSR II non-linear analysis program• Developed & maintained in-house• Fully integrated implementation of ASCE 41• Versatile, adaptable & fast• Validated against full-scale building tests

• Alternate means of verifying code-compliance• ASCE 41-06• LA & SF tall building design guidelines• Other next-generation guidelines: ATC-58, PEER Tall Building Initiative

WHO?• Building owner/developer

• Tenants

• Building Official

• Special user groups

• Design Team (Architect, MEP engineer etc)

WHY?• Develop & agree upon performance expectations / objectives for the design.

• Effectively convey structural implications of design decisions, eg. non-structural isolation requirements, damage vulnerability etc.

HOW?• Pro-actively engaging stakeholders from the project’s outset.

• Design review at project milestones, including peer review

ALTERNATIVE TECHNOLOGIES STAKEHOLDER ENGAGEMENT

MODELLING & ANALYSIS TOOLS

INDUSTRY STANDARDS

130 Sutter StreetSuite 400San Francisco, CA94104

Tel 415 693 1600Fax 415 693 1760www.holmesculley.cominfo@holmesculley.com