Sang Sik Jang Professor Department of Forest Products / Chungnam National University Daejeon, Korea

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1 Certification of fire-resistant timber structures in Korea Sang Sik Jang Professor Department of Forest Products / Chungnam National University Daejeon, Korea Summary In Korea, Korea Building Code-Structural (KBC) was officially approved by the Ministry of Construction and Transportation (MOCT) in 2005, in which Timber Design Code is included as a chapter. Therefore, timber buildings can be designed and constructed in accordance with KBC. However, multi family and multi story timber buildings shall conform to the requirements of fire resistance and sound insulation in addition to the structural requirements. This study was carried to solve the problems related to fire resistance requirements and will be continued to solve the problems related to sound insulation. Even though KS F was formulated about 6 years ago, it shall be reconfirmed because the fire test method has been changed during the time. Two wall structures included in KS F were tested under fire to verify that KS F is still satisfying the fire resistance requirements under the changed testing method. Three additional interior wall structures were tested to obtain certification of fire resistance for timber structures and to revise KS F All the tested structures satisfied the requirements for 60 minute fire resistant structures. Additional tests for exterior wall and floor structures will be carried continuously to revise KS F and to obtain the certification of fire resistance. Tests to evaluate the sound transmission rate of wall and floor structures will also be performed continuously. 1. Introduction Even though timber structures have been used for quite long time in Korea, Building Code of Korea on timber structures was prepared very recently in Before 2005, most of timber structures were designed and constructed based on the experiences of architects and builders without any specified regulations or standards. Because of such a condition, most of timber buildings in Korea before 2005 were limited in area and height to the size of single family housings. To overcome the limiting conditions of timber construction in Korea, Timber Design Code was developed from 1998, and completed and submitted to Korean government in The Timber Design Code was incorporated as a part of Korea Building Code-Structural (KBC) which was officially approved in Timber Design Code is just a structural design standard and, thus, it cannot solve all the problems related to timber construction in Korea. Especially for multi-family and multi-story timber constructions, requirements for fire-resistance and sound insulation shall be satisfied. To evaluate the fire resistance of timber structures and develop KS standards for fire-resistance of timber structures, series of fire-resistance tests for light frame timber structures and heavy timber beams and columns were scheduled starting from the year Fire tests for light frame timber structures were continued to 2001 and the results were formulated to KS F (Fire resistance performance for elements of building construction. Part 1: Wall and floor/ceiling, roof/ceiling assemblies of light frame wood structures) in Fire tests for glulam beams and columns were continued to 2002 and the results were formulated to KS F (Fire resistance performance for elements of building construction. Part 3: Beams and columns made of structural glued-laminated timber) in Even though KS standards were formulated to recognize fire-resistance of timber structures, those standards could not be officially applied to actual construction before Building Code accepts them as parts of it. The Ministry of Construction and Transportation(MOCT) of Korea revised their Regulations on "Standard for the Evacuation and Fireproof Structure of Buildings"(SEFSB) and "Standard for Recognition and Management of Fire-resistant Structures"(SRMFS) to recognize KS

2 F and as applicable method to form fire-resistant structures in Even though it was expected that KS F and can be applied directly to construction without further verification or tests, SEFSB set requirements for additional quality verification process for the materials used which are performed by Korea Institute for Construction Technology(KICT) although additional fire tests are not required. Even though KS standards and MOCT regulations were revised to allow use of fire-resistant timber structures, most of government officials were not willing to give certification of fire-resistance to timber structures. Therefore, for last 3 years since formulation of KS standards nobody was successful to obtain certification of fire-resistance with timber structures. And KS F and which define testing method for fire-resistance of building elements were revised in 2005, in which several points of temperature measurements of the back surface of fire test specimen were added. Some of government officials insisted abrogation of KS F because the testing method was changed. To solve this problem, some verification fire tests were carried out for light frame wood wall structures included in KS F to show that the structures listed in KS F have still satisfactory fire resisting performance under changed testing method. And additional fire tests were performed for interior timber wall structures to check their fire-resistance, to apply for certification of fire resistance and to revise the existing KS F Tests to formulate KS F Materials and method Series of fire tests to develop KS F were performed for light frame wood wall(interior and exterior) and floor/ceiling structures during 1999 and 2001 at Fire Insurers Laboratory of Korea (FILK) located in Yeoju. Korea. For these tests, dimension lumbers having No.2 and better grade of Hem-fir(imported) and larch(domestic) based on KS F 3020 (Softwood structural lumber), fire resistant gypsum boards based on KS F 3504 (Gypsum boards) and mineral fibre insulation based on KS L 9102 (Artificial mineral fibre thermal insulation materials) were selected. Specimens used for fire tests were manufactured as given in Table 1. Table 1 Specimens used for fire tests to formulated KS F Wall Structure Interior wall Exterior wall No. Specification Support Size of Thickness Specimen Size Kind of Framing of Gypsum (a b) 1) condition Insulation at top (mm mm) board(mm) INW ply Mineral wool 3.0m 2.4m Roller INW ply No insulation 3.0m 2.4m Roller INW Mineral wool 3.0m 3.0m Roller INW No insulation 3.0m 3.0m Roller INW ply Mineral wool 3.0m 2.4m Roller INW No insulation 3.0m 2.4m Roller EXW ply (interior side) Mineral wool 3.0m 2.4m Roller EXW (interior side) Mineral wool 3.0m 2.4m Roller EXW ply Mineral wool 3.0m 2.4m Roller

3 1) (interior side) 15 1ply FC Mineral wool 3.0m 5.0m - (bottom side) Floor/ceiling FC No insulation 3.0m 5.0m - (bottom side) For wall specimen, a = width and b = height. For floor specimen, a = width and b = length. For fire tests, KS F and were applied for wall specimens and KS F and were applied to floor specimens. Loads applied to wall specimens were calculated based on the allowable stresses given in KS F 3020 and live loads defined in the Korea Building Code was applied to floor specimens. On top of the floor specimens, concrete Ondol system having thickness of 40mm was installed. 2.2 Results The results of the fire tests of the specimens listed in Table 1 can be summarized as given in Table 2 and were formulated to KS F Table 2 Results of fire tests performed to formulate KS F ) Wall Structure Interior wall Exterior wall Time to failure Fire resistance defined in Specimen No. (minute) KS F INW-1 41~43 30(INW-F30-1) INW-2 35~39 not acceptable INW ) ~67 60(INW-F60-1) INW ) ~76 60(INW-F60-2) INW-5 66~71 60(INW-F60-3) INW (INW-F90-1) EXW-1 36~55 30(EXW-F30-1) EXW ) 60(EXW-F60-1) EXW (EXW-F60-2) FC ) 60(FC-F60-1) Floor/ceiling FC ) 60(FC-F60-2) Tests were stopped after 60 minutes to check the condition of specimens for wall structures and to secure safety for floor structures. 3. Tests to verify KS F Materials and method To verify that the wall structures listed in KS F are still effective fire resistant structures under changed fire test method, INW-F60-1 and EXW-F60-1 specimens were tested by applying the changed test method(ks F and ). To construct specimens, dimension lumbers of SPF No. 2 grade imported from Canada were selected and other testing materials were selected as the same as given in KS F And specimens for fire tests were constructed in accordance with the procedure given in KS F Specimen size was 3.0m(width) 3.0m(height) for both structures and the applied loads were calculated based on the allowable stresses given in KS F 3020.

4 3.2 Results The results of the fire tests of the wall specimens can be summarized as given in Table 3. Table 3 Results of fire tests performed to verify KS F Time to failure Fire resistance defined in Structure Specimen No. (minute) KS F Interior wall INW-F (INW-F30-1) Wall Exterior wall EXW-F (EXW-F30-1) The difference of the changed fire test method compared to the old method is that the number of temperature measuring points on the back surface is increased to 12 points from 5 points. Except the number of temperature measuring points of back surface, all other method are exactly the same as before. So, if the temperature of back surface is not over the upper limit given in the testing method, then it can be concluded that the wall structures listed in KS F are still effective fire resistant structures under the changed testing method. Changes of the maximum temperature of back surface depending on time are given as Figure 1 in which new test results of INW-F60-1 specimen are compared with previous test data for the same specimen types. As shown in Figure 1, the maximum temperature of the back surface was almost not affected by the number and location of temperature measuring points on back surface of specimen. Among the 12 temperature measuring points of the back surface, the maximum temperature was appeared generally at the top of the centre of specimens. For exterior wall specimen EXW-F60-1, similar results were obtained Maximum temperature(oc) Old data 1 Old data 2 New data Time(minute) Figure 1. Changes of the maximum temperature depending on time under fire for INW-F60-1 specimens.

5 4. Tests to certify fire resistance of wall structures with fibre glass insulation 4.1 Materials and method Fire tests for interior light frame wood wall structures were performed to evaluate their fire resistance, to obtain the certification of fire resistance, and to revise KS F because the existing KS F contains only wall structures in which mineral wool was used as insulation. In most of recent light frame wood construction, mineral wool is not used because it is difficult and inconvenient to use. Instead, fibre glass insulation is widely used. Therefore these tests were performed to certify the fire resistance of interior wall structures using fibre glass insulation and to revise KS F by incorporating the test results. Dimension lumbers of SPF No. 2 grade imported from Canada were selected, bat type fibre glass insulations having R-value of 11 were selected and other materials including gypsum boards were selected in accordance with KS F Specimens used for fire tests were manufactured as given in Table 4. Table 4 Specimens used for fire tests of wall structures with fibre glass insulation 1) Structure Specimen No. Size of Framing (mm mm) Type of framing Thickness of Gypsum board(mm) Acoustic channel INW Single One side Interior INW Staggered One side wall INW Double No channel For wall specimen, a = width and b = height. For floor specimen, a = width and b = length. Support condition at top Roller Roller Roller For all the specimens in Table 4, stud spacing of 610mm was applied and R-11 fibre glass insulation was used. To improve the sound insulation, acoustic channel was attached on one side of specimen types INW-4 and INW-5. Specimen type INW-6 was double stud type having 25mm gap between two stud walls in which the space(25mm gap) between two stud walls was considered to have the roll of sound insulation. When selecting the specimen types in Table 4, the sound insulation performance of the wall structures were considered for the future tests of sound transmission rate. 4.2 Results The results of the fire tests of the specimens listed in Table 4 can be summarized as given in Table 5 and will be incorporated as parts of KS F Table 5 Results of fire tests of wall structures with fibre glass insulation 1) Structure Specimen No. Time to failure Fire resistance that will be (minute) defined in KS F INW ) ~ 82 60(INW-F60-4) Interior wall INW-5 74 ~ 82 60(INW-F60-5) INW-6 83 ~ 87 60(INW-F60-6) Tests were stopped after 60 minutes to check the condition of specimens.

6 As given in Table 5, all the specimens showed fire resistance greater than 60 minutes ranging from 74 minutes to 87 minutes. When checked the specimen INW-4 after 60 minutes of fire test, the cross section of stud was almost not reduced and just the surface colour of front edges of the studs was turned to black, which means that charring is just started from the front edges of studs. The maximum temperatures of back surfaces for the specimens given in Table 4 were compared with the results of the previous tests as shown in Figure 2. In Figure 2, INW-4(1) and INW-5(1) are the specimens in which fire was applied to the side where gypsum boards were directly attached to studs and back surface temperatures were measured at the side where acoustic channels were attached. INW-4(2) and INW-5(2) in Figure 2 show the change of the maximum back surface temperatures measured on the side where gypsum boards were attached directly to studs while fire was applied to the side where acoustic channels were attached. As given in Figure 2, the maximum temperature of back surface was less than 80 at the final stage of fire tests. As observed in the previous fire tests, the maximum temperature among the 12 temperature measuring points on the back surface was observed from the top point of the centre of the specimens. Maximum temperature( o C) Time (minute) Old data 1 Old data 2 New data INW-4(1) INW-4(2) INW-5(1) INW-5(2) INW-6(1) INW-6(2) Figure 2. Change of the maximum back surface temperature during fire tests. Figure 3 shows the change of the vertical and average horizontal deformation for the specimen INW-4(1) during fire test. The horizontal deformation is the average of the measured deformation at the center and at both edges of the specimen and at the middle height. The specimen showed 81 minutes of fire resistance in which the vertical and horizontal deformations were kept very small until just before collapse of the structure. The vertical and horizontal deformation of other specimens showed almost similar pattern to the deformation of INW-4(1) specimen.

7 Vertical deformation Horizontal deformation Deformation(mm) Time(minute) Figure 3. Increase of the vertical and horizontal deformation of specimen INW-4(1) during fire test. 5. Future tests for wall and floor structures Fire tests for light frame wood exterior wall structures with fibre glass insulations are scheduled to perform at the end of February in And various floor/ceiling structures in which fibre glass insulations are used will be tested to evaluate their fire resistance. All of these test results for wall and floor structures with fibre glass insulation will be used to revise KS F In Korea, multi-family housings composed of more than 20 units shall conform to the requirements of sound insulation as well as fire resistance, even though multi-family housing composed of less than 20 units are required to conform only to the fire resistance requirements. In this study, sound insulation performance of various wall and floor structures will also be evaluated, and the way to improve the sound proof against heavy impact sounds for timber structures will be studied. 6. Process to obtain fire resistance certification in Korea To obtain the certification of fire resistance in Korea, there are two representative ways. The first way is to obtain certification through KS standards and the second way is directly applying for fire resistance certification process which is managed by KICT. To follow the first way which is to obtain the certification of fire resistance through KS F (light frame structures) or (structural glulam beams and columns), application shall be submitted to KICT and the same certification process managed by KICT except fire tests as the second way shall be applied. Even though the first and second ways follow the same process, fire tests are not required for the first way but required for the second way. However, the first way can only be applied to the structures listed in KS F or Conclusions Series of fire tests for various combinations of interior and exterior wall structures have been performed. Some tests were performed to verify the effectiveness of KS F under the

8 changed testing method and some other tests were performed to obtain the fire resistance certification as well as to revise KS F All the tests results showed enough fire resistance required for 60 minutes fire resistant structures. Additional tests will be performed for exterior wall structures and floor/ceiling assemblies to obtain the fire resistance certification as well as to revise KS F The researches will be continued to evaluate the sound insulation performance of wall and floor structures. 8. References KS F Methods of fire resistance test for elements of building construction: Part 1 General requirements KS F Methods of fire resistance test for elements of building construction: Part 4 Specific requirements for load bearing vertical separating elements KS F Methods of fire resistance test for elements of building construction: Part 5 Specific requirements for load bearing horizontal separating elements KS F Fire resistance performance for elements of building construction: Part 1 Wall and floor/ceiling, roof/ceiling assemblies of light-frame wood structures KS F Fire resistance performance for elements of building construction: Part 3 Beams and columns made of structural glued-laminated timber KS F 3020 Softwood structural lumber KS F 3504 Gypsum boards KS L 9102 Artificial mineral fibre thermal insulation materials