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Performance Based Engineering Solutions “How will my building perform during the next big one?” WHY USE PERFORMANCED BASED ENGINEERING (PBE)? Equipped with a comprehensive model of the existing building and PBE computer model for the Cathedral Building, Oakland CA

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

BENEFITS Performance Based Engineering provides significant benefits to the seismic evaluation and rehabilitation of existing buildings: •

A better understanding by all stakeholders of expected building

seismic events. Common project design objectives are:

performance and project objectives.

Voluntary seismic strengthening (limited rehabilitation) to

Seismic rehabilitation solutions that are complimentary with the

mitigate critical life safety or collapse hazards.

existing structural systems.

Conformance with the Basic Safety Objective (equivalence with

Solutions that are more compatible with programmatic

building code for new construction).

requirements, architectural intent or historic fabric of the existing

Damage reduction or contents protection under small to

building.

moderate seismic events.

Safer, more resilient and economical retrofits.

possible to target different performance objectives for different level


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

APPROACH

Consider inherent strength of existing, archaic materials

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

No (often)

No

Yes

Yes

PRESCRIPTIVE/TRADITIONAL CODE PERFORMANCE BASED ENGINEERING

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. 1989 Loma Prieta e/q Magnitude 6.9 60 miles away from San Francisco

Seismic strengthening, where required, can be sensitive to the existing building by discovering, analyzing and quantifying the contribution of

SMALL AND FREQUENT

existing seismic load resisting elements. Our philosophy is to augment enhanced life safety or property protection. In addition, we are always

Magnitude 7.2 San Francisco Peninsula Fault,10 miles from downtown San Francisco

conscious of the need to consider the building’s function and historic or architecturally significant fabric when locating and detailing any structural strengthening.

RARE AND LARGE

Our role in the assessment and potential strengthening of existing structures is to obtain and understand input from relevant stakeholders 1906 e/q Magnitude 7.9 as felt in San Francisco

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

VERY RARE AND EXTREME

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. TYPICAL PROJECTS THAT BENEFIT FROM PBE

FIGURE 1 MARINE STRUCTURES; Hysteretic Energy Dampers for Substructure Piers 1.5, 3 & 5, San Francisco, CA

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

EARTHQUAKE INTENSITY

rather than replace if additional capacity is required to provide


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

PERFORMANCE

Immediate Occupancy

ND FREQUENT

Life Safety

Collapse Prevention

EARTHQUAKE INTENSITY

CODE

D LARGE

OLDER, UNSTRENGTHENED BUILDINGS

CODE

RE AND EXTREME

STRENGTHENING OF EXISTING BUILDINGS; Cathedral Building, Oakland, CA

PRESCRIPTIVE DESIGN GOAL

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

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


130 Sutter Street Suite 400 San Francisco, CA 94104 Tel 415 693 1600 Fax 415 693 1760 www.holmesculley.com info@holmesculley.com

What’s Involved ALTERNATIVE TECHNOLOGIES • • • • •

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

MODELLING & ANALYSIS TOOLS • • • • •

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

INDUSTRY STANDARDS • • • •

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


Performance Based Engineering