Every ten years ('97, '07 and '17), the BSSC sets design maps rules to support USGS in developing the next generation of hazard maps.The Project 17 Committee (P17C), through the efforts of five work groups that address acceptable risk, precision and uncertainty, multi-period spectra, deterministic caps, and Seismic design Categories will develop proposals on the rules as a Provisions Update Committee (PUC) IT (Issue Team).

P17C Members

P17C Meetings

P17C Work Groups

Work Scope

The IT1 main scope will be to evaluate the adequacy of the qualitative performance objectives in Section 1.1 of the provisions (not in currently ASCE-7) and determine if they are sufficient for the design of buildings and other structures. Moreover, the IT 1 will look at ASCE-7 Chapter 1 that is not currently in the Provision, and Provision Commentary Chapter 11, 12, 13, and 15 that are currently not in ASCE-7. Since there is a Project 17 task committee looking at the acceptable risk with regard to safety based on collapse of the structure, this issue team will focus on topics such as nonstructural performance, loss of function and potentially the level of damage. The committee will review the Resource Paper on future directions in performance based design from the 2015 Provisions and other applicable research projects related to performance-based design (ATC 58-2, ATC-84, ATC etc.). Other potential topics: non-structural performance, loss of function and potentially the level of damage, and the ATC 120 study funded by NIST. IT1 may look at R factor.

Membership

Work Scope

Consider adjustments to design coefficients and factors, including height limits, for seismic force resisting systems; the relationship between deflection amplification factor, response modification coefficient and drift limits; direction of loading requirements, including additional requirements for short period structures; and additional issues raised by or brought into the PUC. Coordinate with IT 1 on issues affecting Chapter 12, such as seismic design categories and multi-period spectra. The work product will be Part 1 proposals and Part 2 Commentary.

Membership

Work Scope

• Possible adjustment of CS in the short period range by the square root of (2R/?o – 1)
• Reduction by R only in the first mode (assuming higher modes are elastic);
• Consideration (or reconsideration) of the appropriateness of current approaches for scaling to the results of an equivalent lateral force (ELF) analysis. This should include both the value matched (base shear, overturning moment, or other) and the scaling factor to be used for matching
• Application of a multi-degree-of-freedom factor
• Modification of MRSA to better target a probability of collapse of 1% in 50 years
• Revisit triggers for Dynamic RSA in ASCE7 and realign with efforts of ATC 123

Membership

Work Scope

The shear wall IT will consider the effects of external loads (gravity as well as lateral) on shear walls of concrete, steel, masonry, and wood. It will next consider the possible failure modes resulting from those load effects or internal forces. This will lead to a determination of the failure modes that are critical in design, which in turn should lead to possible areas of improvement in current design practice. Two of those areas are anticipated to be the following:

1. Coupled shear wall systems are recognized as distinct from isolated shear wall systems in Canadian and New Zealand codes; they are also accorded higher response modification factors in view of their superior seismic performance. The IT will examine whether ASCE 7 should go in the same direction. (suggested by PUC: different R factor for coupled and isolated,need definition of coupled shear wall, ACI 318 will develop the definition, new items in 12.1. Ron Hamburger suggested P 695 study).

2. Tall buildings in the 400-ft height range are increasingly being built in highly seismic areas, with seismic forces being resisted entirely by cores consisting of reinforced concrete shear walls. (suggested by PUC: cooperate with multi-period spectra team).

The shear design of these shear walls is absolutely crucial to the safety of these structures. However, we have at best an imperfect understanding of the maximum shear that can develop and how it is transferred at the base. It will be very beneficial for the IT to look into this design aspect.

The IT will develop Part 1 proposals and accompanying Part 2 commentary dealing with any topic on which the IT is able to progress to that point. All other findings of the IT and work leading to those findings will be recorded in a Part 3 Resource Paper.

Membership

Work Scope

During the development of the 2015 NEHRP Provisions, there was extensive discussion on establishing performance objectives for nonstructural components. In addition, specific issues have been identified that significantly influence the performance of nonstructural components, but are not adequately covered in the current Provisions. With the exception of a review of Rp factors, all of the nonstructural items listed in the 2015 NEHRP Issues were research needs. NIST is supporting the ATC-120 project that directly addresses a substantial number of the research needs, including the force equations and performance objectives for nonstructural components.

Two of the areas of investigation in the second phase of ATC-120 are a detailed evaluation of the nonstructural design provisions, and development of performance objectives for nonstructural components. The detailed evaluation will include development of a design philosophy for nonstructural components that identifies desirable post-yield and failure mechanisms for components, supports and attachments, and a method for producing generic floor spectra for design of nonstructural components.

IT5 will incorporate information from ATC-120 to develop proposals for updating the force equations and nonstructural anchorage to concrete and masonry provisions to reflect the most current research, and proposals to update the Rp factors. Depending on the outcome of the ATC-120 effort on nonstructural performance objectives, IT5 will produce either a proposal or white paper.

Membership

Work Scope

To identify seismic design issues unique to non-building structures. Specific items currently identified for consideration include:

• Thin walled storage tanks for unique liquids such as wine, or bulk solids such as grain (may cross over with IT5).
• Design of large bore piping systems, where the pipe provides significant stiffness relative to the supporting structure.
• Anchorage to concrete, including resistance mechanisms, and load combinations.
• Seismic classification of unusual structures such as airplane hangers.

Membership

Work Scope

1. Review 2015 Chapter 19 provisions. Consider modifications to limitation on damping and base shear reduction, relationships of foundation damping to superstructure damping, and effects base slab stiffness.
2. Review proposed changes to ASCE 41-17. Bring forward pertinent modifications in the Provisions to accommodate updated approaches, revising wording for improved clarity where appropriate. (Pekelnicky comment: there were changes, but most were minor)
3. Consider development of provisions relating to seismic earth pressure on basement walls
4. Consider development of provisions related to rocking in flexible-base foundation modeling.
5. Look at load factor on soil pressure.

Membership

Work Scope

• Improve coordination and reduce inconsistencies between ASCE 7 Chapters, 16, 17,18 and Chapter 12.
• Review and refine quality assurance procedures.
• Review proposals received

Membership

Work Scope

• Determine next steps required to progress the rigid wall - flexible diaphragm seismic design methodology of the FEMA P-1026 guideline document to a Part 1 proposal ready for incorporation into ASCE 7. This will include consideration of technical gaps as well as mandatory language. If possible with IT resources, begin next steps. (road maps)
• Determine next steps required to fully develop and document the methodology for deriving Rs diaphragm design force reduction factors for the alternative provisions for diaphragm seismic design developed by PUC last cycle. If possible with IT resources, begin next steps. (more likely Part III document)
• Incorporate available steel deck diaphragm information into the two items listed above

Membership

Membership

The role of this nation's model building codes and standards is critical to seismic design and mitigation. Any action that furthers the effectiveness of these codes and how they are used will significantly help meet the goal of reducing this nation's losses from natural disasters.

The BSSC Code Resource Support Committee (CRSC) monitors and contributes to the model codes and standards development process particularly, for the International Building Code (IBC), the International Existing Building Code (IEBC) and the International Residential Code (IRC) to ensure that they remain substantially equivalent to the latest edition of the NEHRP Recommended Provisions as defined by the ICSSC under Executive Order 13747 as well as other FEMA earthquake design guidance publications for new and existing buildings.

The CRSC develops and submits code change proposals that further support the NEHRP Recommended Seismic Provisions in other relevant standards publications. The CRSC works with the representative organizations such as ACSE, IBHS, NAHB, and SEAOC to identify and address these issues.

The CRSC also supports related activities such as outreach and education materials to ensure that seismic hazards continue to be addressed.

Comittee Members