2020 NEHRP PROVISIONS IT5: NONSTRUCTURAL COMPONENTS. PUC Update April 13, 2017

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1 2020 NEHRP PROVISIONS IT5: NONSTRUCTURAL COMPONENTS PUC Update April 13, 2017

2 Issue team 5 - Scope Address issues that significantly influence the performance of nonstructural components, but are not adequately covered in the current Provisions Develop proposals/issue papers based on findings and recommendations of the ATC-120 project

3 Issue Team 5 John Gillengerten Peter Carrato Travis Churpalo Bill Holmes Bret Lizundia John Silva Greg Soules Chris Tokas Hussain Bhatia Phil Caldwell Meaghan Halligan Matthew Hoehler Maryann Phipps Robert Simmons Siavash Soroushian

4 IT5 Kick-off Meeting Sacramento, 3/23/2017 Reviewed the status of the ATC-120 project Provided feedback to the ATC-120 team Identified and prioritized issues that should be addressed in the 2020 NEHRP Provisions Developed preliminary action plan

5 ATC-120 Organized into 3 working groups WG1 Assessment of current nonstructural design provisions WG2 Performance expectations for nonstructural components WG3 Evaluation of ASCE 7 nonstructural design equations and alternative philosophies for nonstructural design

6 Working Group 1 Holistic evaluation of the seismic provisions for nonstructural Components Three main tasks Nonstructural design exercises to evaluate the existing design provisions and test proposed changes to the design methodology Roadmap of the nonstructural design provisions in ASCE/SEI 7-16 Review the requirements for anchorage to concrete and masonry

7 Design Exercises Working Group 1 Perform seismic designs for components 4 Design Firms 5 Problems Approach the problems as they would in practice with limited time and budget Comments provided on the technical adequacy and ease of use of the current provisions incorporated into the ASCE 7 roadmap

8 Working Group 1 Develop a roadmap for seismic design of nonstructural components Describe administrative and technical requirements and place them in context Describe the interrelationships between the different design requirements Assess the clarity and completeness of those requirements Draft assessment of Chapter 13 is being reviewed by WG1

9 Working Group 1 Preliminary observations and recommendations on Chapter 13 The scope of the nonstructural requirements should be revised to include all components and systems connected to, supported by, or located within a structure The detailed design provisions need to be consistent with the general provisions Terminology needs to be more precise

10 Working Group 1 Preliminary observations and recommendations on Chapter 13 The tables for architectural and MEP components can be greatly simplified Penthouses should be treated be governed by Chapter 15 as a nonbuilding structure, rather than an architectural component URM partitions, chimneys, and parapets should be prohibited

11 Working Group 1 Anchorage to Concrete and Masonry What is the appropriate design force for anchors to concrete and masonry? Review of recent test data that measures demands in fasteners during dynamic testing Develop recommendations to simpliy force determination for anchors, and provide an appropriate margin of safety against brittle failure

12 Working Group 2 - Nonstructural Performance Objectives Create a set of seismic performance objectives for nonstructural components and systems that addresses components in all seismic design categories that has broad acceptance and dovetails with proposed design recommendations.

13 Working Group 2 - Nonstructural Performance Objectives WG2 Outcomes and Deliverables Framework for nonstructural performance objectives Nonstructural objectives vetted with stakeholders and PUC Recommendations for translating objectives into design practice Implementation by IT1

14 Working Group 3 Evaluation of ASCE 7 nonstructural design equations and exploring alternative philosophies for nonstructural design Goals: Understand the response of nonstructural components Evaluate the validity of current code design procedures and recommend improvements Propose a new design philosophy based on the concept of a nonstructural fuse

15 Terminology PFA: Peak floor acceleration T abldg : ASCE 7 fundamental period of the building T 1IDbldg : The fundamental period per system ID of recorded motion T 1modelbldg : The fundamental period per in analytical model T comp : The fundamental period of the component PCA: Peak component acceleration from an oscillator placed on a floor or roof. This is the vertical ordinate of a floor spectrum where the horizontal axis is the component period, T comp. μ bldg : Ductility experienced by the building μ comp : Ductility experienced by the component β bldg : Damping in the building β comp : Damping in the component

16 From Miranda(2017)

17 Design Equations The current primary ASCE 7 equation for nonstructural design is of the form: F p = f(a p, S DS, R p, I p, z/h) This can be rewritten as F p = f(t comp, S DS, μ comp, z/h) since a p is a function of component period and R p is related to component ductility, μ comp. In a more refined approach, the forces experienced by nonstructural components are of the form: F p = f(shaking intensity, building system/building stiffness, T abldg, μ bldg, z/h, T comp, β bldg, μ comp, β comp ).

18 WG3 - Seeking answers to the following questions Which parameters in the general equation are of significance and which can reasonably be ignored? What is the best measure for shaking intensity? Tying it to more easily available code values like S DS or PGA is desirable. Is a measure for structural system stiffness and deflected shape (such as a flexural beam or shear beam) necessary or is ASCE 7 design period sufficient?

19 WG3 - Seeking answers to the following questions If a component remains elastic, what are the anticipated forces it must be designed for? In large ground shaking, how beneficial would component ductility μ comp > 1 be? What nonstructural design equations are supported by the data and what is their level of uncertainty? Should the code maximum and minimum design demands be modified?

20 WG3 - Seeking answers to the following questions Does the concept of a generic floor spectrum appear promising? If so, what form would it take and how would it be used in practice? Simplified Rigid or Low Bound Flexible or High Bound From Bachman (2016)

21 WG3 - Seeking answers to the following questions Is there an opportunity to introduce capacitybased design for nonstructural components

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24 z/h The Cloud of Acceleration Data 1.0 From Fathali and Lizundia (2011) Data Points from Fixed-base CSMIP Building Stations (N=3241) 0.8 CSMIP Data Inc. Height No. = 2224 Increasing Amplification No. = 920 No. = 97 PFA/PGA 151 Fixed-base Building Stations 73 Earthquakes 541 Building-Earthquake Cases

25 Working Group 3 Task assignments as of IT5 meeting on 3/23

26 Representative Issues to be Resolved Tying all the research together Making it practical for engineers Achieving consensus How many options to have Lack of information on component period, damping and ductility

27 Representative Issues to be Resolved Distribution of loads in yielding systems of interconnected elements Construction practicality and cost Qualification testing Situations where providing a fuse is not realistic Product liability and engineering responsibility

28 Discussion Photo from :