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
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
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)
Consider inherent strength of existing, archaic materials
Evaluate performance for different seismic hazards or scenarios (for new, existing or rehabilitated conditions)
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 buildingâ€™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
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
OLDER, UNSTRENGTHENED BUILDINGS
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 firstname.lastname@example.org
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 •
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