Structured Lumber and Fire Safety

Transcription

1 Structural Stability of Engineered Lumber in Fire Conditions Results of research study by Bob Backstrom and Mahmood Tabaddor, Ph.D. In 2008, Underwriters Laboratories conducted a fire research study sponsored by the Federal Emergency Management Agency s Assistance to Firefighters Fire Prevention and Safety Grant Program in partnership with the Chicago Fire Department, International Association of Fire Chiefs and Michigan State University. The research was conducted to enhance understanding of hazards to firefighters posed by use of lightweight wood trusses and engineered lumber in roof and floor designs that are increasingly replacing conventional solid joist construction in residential structures. The project investigated and compared the fire performance of conventional solid joist lumber and lightweight lumber used in floor and roof construction when subjected to fire tests. The fire performance data allow fire professionals to better understand fire hazards and assess safety risk to building occupants and firefighters. And, this information provides substantiation for code requirements for fire ratings of lightweight (continued on page 4) In this issue: 2 What s Hot 7 Questions & Answers 3 Canadian Corner: New Residential Detector Regulations in Canada 8 Calender of Events

2 02 What s Hot -sponsored symposium to focus on residential fire safety is committed to life safety and public education that make the world a safer place to live and work. In support of this goal, and the Phoenix Fire Department are co-sponsoring a two-day educational symposium focused on sharing ideas and fostering discussion among attendees about fire safety in North American residential buildings. Participants will learn how they can support fire safety initiatives in residential home construction by designing, specifying and building lowcost fire safety building components into residential buildings. The symposium will be held December 2-3 in Phoenix, AZ. To learn more and to register, please go to select Fire Safety and the Designing Fire Safety into Residential Construction: Perspectives, Ideas and Trends course. Fire & Building Materials Conference is pleased to announce it will be playing a major role in Principia Partners Fire 2009: Flammability and Combustibility in Building Materials Conference. The conference will be at the Chicago Marriott Downtown, Chicago, IL on November 16 & 17. Chris Hasbrook, s Vice President and General Manager, and Robert Backstrom, Senior Staff Engineer, will be speaking. is also the full program sponsor for the event and will be hosting a tour of its facilities with a live fire test during the afternoon of November 17. This is a unique conference that specifically focuses on the latest developments in building materials and their performance in the fire environment, including how current and future trends in fire codes, building design, raw material technologies, and building materials will affect the building products industry. The entire program is on Principia s website at Principia is also offering a special 40% discount off of the registration fee for all clients and safety stakeholders, simply write the code -special adjacent to your name on the on-line registration form. If you are interested in the tour, please call Principia to reserve your space as seating is limited. For more information, please contact Robert Tockarshewsky with at or at Robert.Tockarshewsky@us.ul.com; or Steve Van Kouteren, with Principia Partners at or at SteveVK@PrincipiaConsulting.com. Questions & Answers Does offer any training or education courses for fire safety professionals or building code officials? For over 100 years has provided technical expertise to manufacturers and safety stakeholders. Through a combination of online training, books, safety videos, live Web-delivered programs and facilitated workshops, University offers training solutions customized to fit your needs. Below are two of s featured courses for the fire and regulatory community. Structural Stability of Engineer Lumbered in Fire Conditions is a complimentary two-hour presentation that summarizes a research study on the hazards posed to fire fighters by the use of lightweight construction and engineered lumber in floor and roof designs. For more information and to register for this course at no cost, please visit us/catalog/display.resource. aspx?resourceid= Performance of Special Extinguishing Agents for Firefighter Use is a complimentary one-hour presentation based on a research study evaluating the performance and effectiveness of special extinguishment agents in residential firefighting. This presentation examines the fire performance of various special agents including wetting agents and Class A foams and compares their performance to that of a baseline, traditional water application. For more information and to register for this course at no cost, please visit us/catalog/display.resource. aspx?resourceid= For information about the rest of s training catalog, please visit for a complete list of courses.

3 03 Canadian Corner New Residential Detector Regulations in Canada In 2007, Health Canada (HC) launched a consultation process to provide the public with an opportunity to review a proposal to, among other things, update the health and safety requirements for residential detectors covered under the Hazardous Products Act (HPA). The HPA grants the authority to HC to prohibit or restrict the advertisement, sale or import of products that are or are likely to be hazardous to the public. Underwriters Laboratories of Canada actively participated in this process. And, as a result of the public consultation process, several significant changes were made to the HC regulations relating to smoke detectors, smoke alarms, audible signaling devices and control units. Consultation process As explained in HC s consultation process, the requirements for residential detectors under the HPA are intended to ensure that the products available to the Canadian market facilitate and complement the National Building Code (NBC) and National Fire Code (NFC). However, the consultation process revealed an important gap: the NBC and NFC can only regulate products used in buildings. These codes cannot regulate the import, advertising and sales of these same products. Regulating these products under the HPA minimizes the potential for buying and installing sub-standard products as it is illegal to import, advertise or sell such noncompliant products in Canada. Only those products that meet the CAN/ C or C Standards will be available to consumers. The impact extends beyond building construction that would be normally be inspected to determine detectors are in compliance with the standards referenced in the NBC and NFC. In many cases, consumers simply buy individual detectors to replace or supplement the ones already installed in their homes. With the products regulated under the HPA at the consumer level, they too would be assured that the products available in Canada also meet the current CAN/C or C Standards. By regulating residential detectors under the HPA, HC provides the legal basis to close this gap and ensure that Canadians enjoy the benefits of the latest in alarm and detector technology. (continued on page 7)

4 04 Engineered Lumber in Fire Conditions (continued from cover) construction in residential structures to further enhance firefighter safety. The tests were conducted at s Northbrook, Ill., fire test laboratory during Background on the research project For more than 35 years, the fire service community has repeatedly expressed concern regarding the structural performance of wood I beams and wood trusses commonly known as lightweight wood construction during a fire. In October 1992, the National Fire Protection Research Foundation published a report titled, National Engineered Lightweight Construction Fire Research Project Technical Report: Literature Search & Technical Analysis. The report cited 60 articles published between 1970 and 1990 related to the fire performance of lightweight wood construction. The report identified the need for fire performance data and training focusing upon the fire performance of lightweight wood construction. These needs remain today and have been amplified by incident reports collected by the National Fire Fighter Near-Miss Reporting System and National Institute for Occupational Health (NIOSH) Fire Fighter Fatality Investigation and Prevention Program. Because of concern for fire fighter safety and misinformation out in the field, approached the Federal Emergency Management Agency to offer assistance. Because no standardized tests had been conducted to compare traditional to modern assemblies, considered it important to develop a comprehensive test plan to research the fire performance of assemblies representative of typical residential construction, the different materials within floor assemblies and various other factors. In addition, the result from such research was to be developed into a fire fighter training program. test plan The test plan called for nine fire tests: seven floor-ceiling assemblies and two roof-ceiling assemblies. A goal of the project was to develop comparable fire performance data among assemblies. All assemblies were intended to represent typical residential construction, with some assemblies representing legacy construction methods and materials and others representing modern methods and Photograph of mannequins representing standing and crawling fire fighters materials including lighter weight wood structural members. Two of the assemblies did not include a ceiling; six of the assemblies included a ceiling consisting of ½ inch regular gypsum board; and one assembly included a ¾ inch plaster ceiling. Standard ASTM E119, Fire Tests of Building and Construction Materials, describes a fire test method that establishes benchmark fire resistance performance between different types Table 1 Description of Test Samples Test Assembly Supports Ceiling Floor or Roof 1 2 inch x 10 inch with 16-inch centers None 1 inch x 6 inch subfloor and 1 inch by 4 inch finish floor 2 12 inch deep I joist with 24-inch centers None 23/32 inch OSB subfloor, carpet padding and carpet 3 2 inch x 10 inch with 16-inch centers ½ inch regular gypsum wallboard 1 inch x 6 inch subfloor and 1 inch x 4 inch finish floor 4 12 inch deep I joist with 24-inch centers ½ inch regular gypsum wallboard 23/32 inch OSB subfloor, carpet padding and carpet 5 14-inch parallel chord truss with steel gusset plate connections with 24-inch centers 6 14-inch parallel chord truss with glued connections with 24-inch centers ½ inch regular gypsum wallboard ½ inch regular gypsum wallboard 23/32 inch OSB subfloor, carpet padding and carpet 23/32 inch OSB subfloor, carpet padding and carpet 7 2 inch x 6 inch with 16-inch centers and 2/12 pitch ½ inch regular gypsum wallboard 1 inch by 6 inch roof deck covered with asphalt shingles 8 2 inch x 10 inch with 16-inch centers ¾ inch plaster 1 inch by 6 subfloor inch and 1 inch by 4 inch finish floor 9 Roof truss with steel gusset plate connections with 24-inch centers and 2/12 pitch ½ inch regular gypsum wallboard 7/16 inch OSB covered with asphalt shingles

5 05 Images from video recordings of each experiment of building assemblies. For floor-ceiling and roof-ceiling assemblies exposed to a standardized fire, the standard requires that a minimum 180 square foot sample prohibit the passage of flame and limit the temperature rise at specific locations while supporting a load. The standardized fire represents a fully developed fire within a residential or commercial structure with temperatures reaching 1,000ºF at five minutes and 1,700ºF at 60 minutes. The nine fire tests conducted by complied with the requirements of ASTM E119, but the applied structural load was nontraditional. Typically, a uniform load is applied on a floor or roof to fully stress supporting structural members. This load is generally higher than the minimum design load of 40 pounds per square foot (psf), as specified by the building code for residential construction. For the fire tests, the sample load was intended to represent typical conditions during a fire. A load of 40 psf was placed along two of the four edges of the floor-ceiling assemblies to represent loads on the perimeter of a room. On each sample, two 300-pound mannequins simulating fire service personnel were placed near the center of the sample. For the two samples that represented roof-ceiling assemblies, the two mannequins were the only live load applied on the test sample. Table 1 summarizes the construction details of each test sample. Test results The results of the ASTM E119 fire tests are expressed in terms of hours such as ½ hour-, 1 hour- or 2 hour-rated assemblies. Because all fires are different with respect to room size, combustible content and ventilation, these time ratings are not intended to convey the actual time a specific structure will withstand a fire. Instead, the ASTM E119 test method provides a benchmark that enables a comparison of fire performance between test samples. For unrestrained floor-ceiling assemblies and unrestrained roof-ceiling assemblies such as the tested samples, ASTM E119 includes the following conditions of acceptance: The sample shall support the applied load without developing conditions that would result in flaming of cotton waste place on the floor or roof surface Any temperature measured on the surface of the floor or roof shall not increase more than 325ºF and the average temperature measured on the surface of the floor or roof shall not increase more than 250ºF (continued on page 6) Table 2 Summary of Test Results to ASTM E119 Test Assembly Time of 250ºF average temperature rise on surface of floor/roof (in minutes) Time of 325ºF maximum temperature rise on surface of floor/roof (in minutes) Flame passage through floor/roof (in minutes) Collapse (in minutes) 1 * * 18:30 18: * * 06:00 06: * * 44:15 44: * * * 26: * 29:15 28:40 29: * 24:15 26:00 26: :45 38:30 26:00 40: * * * 79:45 51** 9 * * * 23:15 23 Fire Resistance Rating (min) * This condition was not achieved during the fire test. ** Plaster ceiling in contact with furnace thermocouples at 51 minutes. The test method requires that the junction of the thermocouples in the furnace be placed 12 inches from the ceiling surface at the beginning of the test and shall not touch the sample as a result of deflection.

6 06 Engineered Lumber in Fire Conditions (continued from page 5) The results of the nine fire tests in terms of the ASTM E119 conditions of acceptance are summarized in Table 2. The objective of this research project was to develop fire endurance data on assemblies to compare the fire performance of legacy construction (dimensional sawn cut lumber, solid sub- and finish flooring) to that of modern protected and unprotected lightweight construction (engineering structural elements, oriented strand board subfloor and carpeted finish flooring). One insightful comparison is that of time to collapse: The unprotected legacy construction (assembly 1) collapsed at approximately 19 minutes as compared to six Finite element model of assembly 2 illustrating the mechanical loads Temperature result comparison between model and test for assembly 1 Temperature contour of cross section for assembly 2 at three minutes minutes for the unprotected lightweight construction (assembly 2) Adding a non-fire rated, generic ½ inch thick gypsum board increased the time to collapse for legacy construction (assembly 3) to 44 minutes, an improvement of 25 minutes For modern construction (assembly 4), the installation of ½ inch gypsum wallboard increased the time to collapse to approximately 27 minutes, an improvement of 21 minutes Of particular interest is the time to collapse of very familiar traditional construction, dimensional sawn cut lumber protected by a metal lath / plaster ceiling (assembly 8). This assembly demonstrated the longest time nearly 80 minutes to structural collapse. Computational modeling Computational modeling of the fire response of building materials, components and systems is gaining ground due to advances in analysis techniques and computing technology. As part of this project, studied the challenges of using computational modeling tools to simulate the fire performance of wood-based components. Using the commercial finite element (FE) software ANSYS, sequentially coupled thermal and mechanical analyses were conducted for two unprotected floor assemblies: a conventional wood floor (Assembly 1) and an engineered wood floor (Assembly 2). The main challenge in modeling wood floors as opposed to other common building materials such as steel, concrete and masonry is that wood burns and chars. As such, any model predicting performance of wood-based structural systems must account for this behavior. The FE models of the floor assemblies were built based on detailed construction drawings and included all relevant boundary and loading conditions of the floor furnace test. However, a very critical input to the FE models was the thermal and mechanical properties for the constituent materials. In a fire environment, construction elements are exposed to a very wide temperature range that reaches high temperatures. Over this wide range, wood degrades and decomposes significantly, changing material properties such as thermal conductivity, modulus of elasticity, etc. So it is important to have material property data for the different wood components over the entire temperature range of interest. As such, these properties will also include wood in its charred state. The input material properties for both the thermal and mechanical analyses were measured from wood samples of the two floor assemblies by Michigan State University under the direction of Dr. V. Kodur. Thermal results for the model were computed using a transient analysis that included radiation, convection and conduction modes of heat transfer. For structural results, a nonlinear, quasi-static elastic analysis was performed at select points in time. For the thermal model, comparison with thermocouple measurements pointed to the importance of adding internal heat generation elements to simulate the actual burning of wood and accurate measure of temperature dependent material properties of the wood and the char. Though the model did not accurately predict the final deflection magnitudes, the structural model did predict that floor assembly 2 would lose structural stiffness at a much faster rate than floor assembly 1. By designing and conducting tests similar to those described in this article and building test databases, is continuing research on improving the predictive capabilities of computer models for wood burning building components and systems. Getting the word out to the fire service To get the word out to the fire service, made numerous presentations at symposia sponsored by fire house and fire protection engineering trade media; the 2008 Chicago Fire Department s Strategy & Tactics Conference and Expo; s 2008 Global Fire Service Leadership Conference; the Georgia Fire Chiefs Association meeting; and the Colorado Fire Marshals and ICC Code training

7 07 symposia, 2009 NFPA Conference & Expo, FIRE 2009 Flammability & Combustibility in Building Materials Conference, and the 2009 IAFC Fire Rescue International Conference. The January/February 2009 issue of the International Fire Fighter distributed to more than 370,000 U.S. and Canadian fire fighters highlighted the research. s research was covered by WISN-TV in Milwaukee. A free web-based training program for the fire service providing a summary of the tests and lessons learned is available on s Web site at ltwtconstruction. For more information on this project, please contact Bob Backstrom at or at Robert.G.Backstrom@us.ul.com. For a full report on the first phase modeling of the wood floor assemblies, please contact Mahmood Tabaddor, Ph.D at or at Mahmood.Tabaddor@us.ul.com. Detector Regulations in Canada (continued from page 3) In the consultation process, several options for updating the HPA were presented. They were: 1. Take no action, which would have effectively resulted in industry manufacturing in compliance with C, NBC and NFC current state-of-the-art requirements, while HC would continue requiring compliance with outdated 1970s era standards 2. Adopt standards other than those in the proposed regulations that would have resulted in significant incremental costs for HCs with little incremental benefit 3. Adopt the proposed regulations referring to current C Standards as amended periodically. This was viewed as the most efficient option for the government of Canada to pursue as the C Standards development process includes extensive consultations with stakeholders including manufacturers and HC. The process also provides advance notice and time for manufacturers to adjust production specifications to bring their products into conformity with the newer standards The decision was to utilize option 3 that resulted in the creation of Residential Detectors Regulations referencing C Standards. This was deemed the best option for getting the most modern and safest detectors/alarm systems meeting C Standards into the hands of consumers. During its consultation process, HC gave a strong endorsement to the national standards system that is administered by the Standards Council of Canada as well as Underwriters Laboratories of Canada as a Standards Development Organization and a Certification and Testing Organization. The new regulations The Residential Detectors Regulations pursuant to Section 5 of the HPA came into effect on June 18, These federal regulations allow for the continuous reference to C Standards as amended from time to time and that any required text for products covered by the regulations be published in French and English. Compliance with these regulations will be monitored by ongoing Health Canada inspection programs. For more information on these new regulations, please contact Brian McBain, Regulatory Services, at or at Brian.McBain@ca.ul.com or Rae Dulmage at , ext or at Graham.R.Dulmage@ca.ul.com.

8 Non-Profit Org. U.S. Postage PA I D 333 Pfingsten Road Northbrook, IL United States of America Permit No Northbrook, IL The Fire & Security Authority 08 Calendar of Events If you would like The Fire & Security Authority to consider publishing your upcoming events, contact Kim Delort, editor, in Northbrook, IL, by at Kimberly.Delort@us.ul.com Please type Calendar in the subject line. October American Fire Sprinkler Association Annual Convention (AFSA) San Diego, CA October China Fire 2009 National Agricultural Exhibition Hall, Beijing, China October Security Canada Central Toronto, ON, Canada October International Security Conference 2009 (ISC East) New York, New York October IFSEC, India Pragati Maidan, New Delhi November 1 4 Security China Exposition 2009 Shenzhen, China News.aspx November 4 6 International Sleep Products Association (ISPA) Industry Conference and Exhibition Bonita Springs, FL November 4 6 India SCCP Workshop Theme: Fire Safety In Tall Buildings New Delhi, India November Fire 2009, Flammability and Combustibility in Building Materials Chicago, IL com December 2 4 Construct Canada Toronto, ON, Canada December 2 3 Residential Fire Safety Symposium Phoenix, AZ Hosted Event The Fire & Security Authority Published by the Regulatory Services Department and the Building Materials/Life Safety and Security Industries of Underwriters Laboratories Inc. A Nationally Recognized Testing Laboratory (NRTL) Managing Editor Kim Delort T:: E:: Kimberly.Delort@us.ul.com Address changes and additions T:: F:: E:: Diane.E.Fonzino@us.ul.com All rights reserved. BDI 09XXXX