Ceiling System Performance One Manufacturer s Perspective. Paul Hough Armstrong World Industries, Inc.

Transcription

1 Ceiling System Performance One Manufacturer s Perspective Paul Hough Armstrong World Industries, Inc.

2 Why Would a Manufacturer Want to Not sure of performance Test (Initially)? Get a competitive advantage Level the playing field

3 Once You Have Some Testing Completed Gain a little understanding of performance Feel good about your products performance Get new products approved

4 Once You Become Obsessed Gain an understanding of potential failures Improve the performance of the systems Start to drive code changes

5 Current Code Requirements for Ceilings Current requirements are spread throughout six or seven different documents. ASTM C 635 ASTM C 636 CISCA Zone 0-2 CISCA Zone 3-4 ASCE7 IBC (ASTM E 580) Based on Tee-bar suspension systems only Based on minimal testing done in 1980 s and previous earthquake damage reconnaissance Prescriptive set of installation procedures

6 Basic Requirements For Ceiling Systems Strength of grid & connections Perimeter Support Width of closure Clearance to wall Hanger wires Lateral restraint (areas exceeding 1000 ft 2 ) Splay bracing Changes in elevation Rigid bracing Cable trays Separation Joints (areas exceeding 2500 ft 2 ) Penetration Clearances (1 minimum) Special Inspections

7 Unanswered Questions With The Current Code Is keeping ceiling panels in the suspension system important? When is lateral restraint needed or effective? Are compression struts effective? Does the floating ceiling concept for SDC C really work? What is the interaction between ceiling systems, lights, HVAC, sprinklers, partitions, others?

8 Why Have a Testing or Qualification Protocol? Performance of structures is most often dependent on the performance of nonstructural components & contents. Nonstructural systems are very complex & in some cases impossible to model. Some nonstructural components have undisclosed structural composition & cannot be modeled. Nonstructural components are responsible for the functionality of structures & must be characterized in some fashion. Reinhorn et al

9 Other Considerations California SB 1953 for Hospitals requires pre-1973 acute care hospital buildings and facilities be retrofitted to meet non-structural seismic performance requirements by January 1, 2002 meet intermediate structural standards (collapse prevention) by 2008 be in full compliance with contemporary seismic structural standards by 2030 How do we determine if there is any improvement in the performance of an existing ceiling after modification or retrofit?

10 Other Options per the Codes ASCE7(05) Testing Alternative for Seismic Capacity Determination. As an alternative to the analytical requirements of Sections 13.2 through 13.6, testing shall be deemed as an acceptable method to determine the seismic capacity of components and their supports and attachments. Seismic qualification by testing based upon a nationally recognized testing standard procedure, such as ICC-ES AC 156, acceptable to the authority having jurisdiction shall be deemed to satisfy the design and evaluation requirements provided that the substantiated seismic capacities equal or exceed the seismic demands determined in accordance with Sections and IBC Seismic qualification of mechanical and electrical equipment. Qualification shall be by an actual test on a shake table, by three-dimensional shock tests, by an analytical method using dynamic characteristics and forces, by the use of experience data (i.e., historical data demonstrating acceptable seismic performance) or by a more rigorous analysis providing for equivalent safety.

11 AC 156 Tells you how to run the shake table & develop a qualification plan but not how to deal with a total system such as ceilings. This led to development of a test frame and procedures specifically for ceilings.

12 Frame Details Designed to simulate a story in building Flexible roof / floor Rigid walls or cladding Designed to be compatible with construction needs Allow for suspension of ceilings Allow for connection or isolation of grid to walls Allow for 12 x12 x12 grid with post Frame is 16 X 16 X 6

13 Test Protocol Test No. Test name S s (g) Description 1 WHX -- Triaxial white noise excitation in the horizontal (N-S & E-W) and vertical directions 2 25X X X X X X X X 2, X X X X 3.00

14 System Test at 25X Play

15 Modified System at 150X Play

16 Modified System at 175X Play

17 Outcomes This has lead to development of draft ASTM Test Standard, Test Method to Predict Seismic Performance of Suspended Ceiling Systems by Full-Scale Dynamic Testing New ICC-ES Acceptance Criteria, AC368 Acceptance Criteria for Suspended Ceiling Framing Systems (possible inclusion of testing protocol in future) A line in the sand for acceptance & qualification.

18 Acceptance??? Ceiling Industry has been reluctant. Want the ideal method that is not too restrictive. Everyone wants to see their own data. Everyone wants to make sure their products are okay before accepting. Code Officials are excited but reluctant. Deer in the headlights. I m not an earthquake engineer! I don t want to be the first to accept this. What does ICC say? Do you have ICC-ES Approval yet? ICC-ES is excited but reluctant.

19 Acceptance Overall acceptance has been slow but steady. If you have tested the proper system to prove your point, look for formal approval / acceptance to take 1 to 2 years. Local approval by AHJ could be quicker. (maybe?)

20 Results of This Effort Has led or will lead to changes in: ASTM C 635 ASTM C 636 ASTM E 580 CISCA 0-2 CISCA 3 4 ASCE7 IBC ICC-ES AC368

21 Next Steps Changes to the building code System improvements based on performance Reduced installation hassles (in the hope that the code will actually be followed) Bigger frame (25 X 50 X 10 ) Deeper plenums (4 to 6 ) Safer buildings Full functionality after earthquakes???

22 Incremental Improvements Positive effects on California SB 1954 Building code Improved ceiling system performance Continued innovations Improved installation techniques

23 Parting Thought However in the nonstructural world having it installed properly is even more important than the design itself. R. E. Bachman ASTM October 23, 2006