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File: Building Pdf 84483 | Jj2011aug 09 11
international cooperation improving fire safety in buildings in last month s column introducing initiatives of japan s building ing material which is made with a non research institute we looked ...

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         INTERNATIONAL COOPERATION
         Improving Fire Safety in Buildings
         In last month’s column introducing initiatives of Japan’s Building                             ing material which is made with a non-
         Research Institute, we looked at the Institute’s efforts to unravel the                        combustible material, and it prevents the 
                                                                                                        heat of a fire from conducting to the 
         mystery of wind damage to buildings. In this month’s issue we look at                          components. As long as the temperature 
         the Institute’s work to improve the fire-resistance performance of                             of the components is kept down, it is 
         buildings as well as to develop performance regulations for fire control                       possible to retain the certified strength 
         standards based on clarification of fire phenomena.                                            of the design.
                                                                                                             In addition, it is important to create 
                                                                                                        fire compartments to contain fires. A 
                       espite starting on the twen-      engineers. As a result, we found that due      building or a floor is divided into several 
                       ty-first floor, a fire in a       to ongoing refurbishment of fire safety        fire compartments. If a fire breaks out, it 
                       high-rise building in Spain       measures, no fire compartments were            is contained inside the fire compartment 
         Din February 2005 destroyed  installed in the building where the fire                          where it started. Using materials that do 
         almost the whole thirty-two-story tower         broke out. Therefore, the fire was able        not easily conduct heat and securing a 
         with widespread collapse of the exterior        to spread through the gaps in the exterior     sufficient thickness for the walls and 
         walls and floors of the upper stories           walls and between the floors to the            floors of the fire compartment make it 
         (photo 1). Had it been a wooden build-          upper and lower floors in a short time,        difficult for the fire to spread to sur-
         ing, there would have been no wonder            and it became clear that the columns of        rounding areas. It is then possible to 
         about its total destruction and collapse        the peripheral steel frame lost strength       prevent the fire from spreading beyond 
         in a fire. However, there are hardly any        and broke down in the heat of the fire         the fire compartment and to prevent the 
         examples of a high-rise building collaps-       causing the widespread collapse.               destruction of the whole building. 
         ing in a fire. Since the Building                                                                   Aiming to improve fire safety in 
         Research Institute had a very strong in-        Constructing Fire-Resistant                    buildings, the Building Research 
         terest in the collapse of the building as a     Buildings                                      Institute is promoting research based on 
         result of this fire, we organized a field                                                      incidents such as the collapse of high-
         trip to Spain together with Japanese fire       In the past, many buildings and towns          rise buildings caused by fires in recent 
                                                         in Japan were constructed in wood              years. This article introduces some re-
                                                         and as a result, we have repeatedly ex-        cent research on improving fire-resistive 
                                                         perienced the total destruction of houses      performance in buildings. 
                                                         or the devastation of whole towns once 
                                                         a fire breaks out. Therefore, from the         Confirming Fire Resistance of Full-
                                                         late nineteenth century, buildings have        Size Steel Structural Components
                                                         been constructed with non-combustible 
                                                         material such as brick, concrete and           Steel frames and steel are widely used 
                                                         steel to protect buildings and cities from     materials in high-rise buildings and in 
                                                         fire. Certainly, a building constructed        buildings with large interior spaces. 
                                                         with non-combustible materials will not        Steel, of course, does not burn but if the 
                                                         itself burn, but many of our personal ef-      heat of a fire reaches high temperatures, 
                                                         fects including clothes and furniture are      it loses its strength and as a result, there 
                                                       TITUTEcombustible. Even if a building is con-    is a risk of deformation in steel columns 
                                                       S
                                                       N structed in concrete and steel, as long as     and beams. Therefore, the steel frame is 
                                                         there are people living in it, they will       protected with so-called fire-protective 
                                                       ESEARCH Iuse fire and since there are a lot of com-covering, which is material with high in-
                                                       NG Rbustible items inside a house, it is not     sulation properties, to prevent the heat of 
                                                       LDI
                                                       I possible to completely prevent the out-        a fire from driving up the temperature.  
                                                       U
                                                       B
                                                       E break of fires. Buildings constructed               The capacity of columns, beams and 
                                                         with columns and beams made of steel,          other components to withstand the heat 
                                                       Y OF THfor example, also collapse with the im-   of a fire and to support the weight of a 
                                                       TES
                                                       R pact of the heat from a fire.                  building (load-bearing capacity) and the 
                                                       U
                                                       O     What can we do to construct build-         capacity of walls, floors and other com-
                                                       OS C
                                                       T ings that are fire resistant and do not        ponents to block the heat of a fire and 
                                                       O
                                                       H collapse in a fire? First, we protect the      the flames themselves (insulation, integ-
                                                       ALL Pcolumns, beams and other components         rity) are collectively referred to as fire-
         Photo 1: Total destruction of high-rise 
         building in Spain with large-scale              with fire protective covering. Briefly, a      resistive performance. Components are 
         collapse of the upper floors                    fire protective covering is a heat insulat-    tested for fire-resistive performance by 
                                                                                                                                                 9
              INTERNATIONAL COOPERATION
                                                                                                                   Fire Resistance in Wooden Buildings
              loading them into a furnace that repro-
              duces the heat of a fire furnace. The du-
              ration until fire-resistive performance is                                                           Since there are definite limits on the 
              lost (destruction, heat penetration, holes)                                                          strength, fire resistance and other per-
              under exposure to the heat from the fire                                                             formance of wooden materials, efforts 
              is called the fire resistance rating.                                                                are underway to develop wood com-
              Naturally, the longer the time, the higher                                                           posites by combination with steel and 
              the fire-resistive performance.                                                                      other materials, or hybrid wooden 
                   The Building Standards Law of Japan                                                             structures by combination with rein-
              determines the required fire-resistive                                                               forced concrete construction and other 
              performance for components, that is, the                                                             structures. For our research, we imple-
              fire resistance rating, in accordance with                                                           mented the premise of a four-story 
              the purpose, number of floors and scale                                                              building using wood composites and 
              of buildings. There are notifications of                                                             hybrid wooden structures.
              concrete specifications. For example,                                                                     The drawback of wood is its com-
              where the steel frame columns (a mini-                                                               bustibility. It is certainly the case that 
              mum breadth end diameter of at least                                                                 small components will ignite and burn 
              25 cm) are covered with a fire-resistive                   Photo 2: Test column                      up within a short time if they are ex-
              covering of bricks to a thickness of at                    after fire testing where                  posed to the heat of a fire but when the 
              least 7 cm, the fire resistance rating is                  25% of the fire resistive                 components are large and thick, the 
              two hours.                                                 covering was stripped off                 surface burns without the combustion 
                   According to the Building Standards                                                             reaching the interior. This is because a 
              Law of Japan, a fire resistance rating of                                                            char layer forms when wood burns cre-
              three hours is required for columns near                Next, we simulated earthquake                ating an insulating effect that blocks the 
              to the ground level in skyscrapers. It is          damage to the fire protective covering            heat from the flame.
              necessary to conduct fire resistance tests         and conducted a test with 25% of the                   Therefore, we combined wood and 
              of the columns to confirm they have the            covering removed. As a result of the              steel to develop a component with glued 
              necessary fire resistance ratings with the         loss of the insulating effect of the fire         laminated timber (called glulam, made 
              applied load, but in the past these tests          protective covering, the fire rating was          of several layers of dimensioned timber 
              have not been possible with full-size              reduced to a mere 27 minutes. Since               glued together) bonded to the circumfer-
              columns due to the poor performance                the areas without fire protective cover-          ence of a steel frame. When this compo-
              of the testing equipment. Therefore, we            ing conducted large quantities of heat            nent is exposed to heat, the surface of 
              confirmed the fire-resistance performance          from direct exposure to the fire, the             the glulam ignites but as it burns, a char 
              with the full-size columns used in the             columns were heated to a high tempera-            layer is formed that functions as a fire 
              first floor of a fifty-story building using        ture in a short time despite their large          protective coating, as it were, and the 
              the Building Research Institutes upgrad-          size (photo 2).                                   insulating effect can prevent the tem-
              ed fire furnace for columns, which has                  In the past, there has hardly been           perature in the steel frame from rising. 
              the highest load capacity in the country.          any research of fire safety measures fol-         After the heat of the fire has been re-
                   Fire protective covering equivalent           lowing earthquakes. After demonstrating           moved, the glulam portion is smolder-
              to a fire rating of 1 hour was applied to          in this manner that damage or loss of             ing. We refer to this material that com-
              the steel frame columns that were tested.          fire protective 
              We found that the fire-resistive perfor-           covering has a 
              mance of the columns was adequate as               large impact on 
              they did not break even after more than            lowering fire-
              three hours of fire testing. This was              resistive perfor-
              thought to be due to the impact of the             mance, we plan 
              large dimensions of the steel frame col-           to carry on full-
              umns in addition to the insulating effect          scale research 
              of the fire protective covering. It is the         into measures to 
              same reasoning whereby a small amount              prevent damage 
              of heat will warm a cup of water, but a            or loss of fire 
              large amount of heat is necessary to               protective cov-
              warm a bathtub full of water. Since a              ering and other 
              large amount of heat is needed to heat up          measures to se-
              a steel frame column of large dimensions,          cure fire safety 
              it is obvious that the column as a whole           in the wake of 
              is difficult to heat up. As a result, the fire     an earthquake.   
              rating was higher than expected.                                           Photo 3: Full-size fire testing of a wooden hybrid construction
               10
          Photo 4: Fire performance after testing                     wood and requiring fire resis-      ated inside the concrete when it conducts 
                                                                      tive ratings is already under       the heat from a fire and it is hoped that 
                                                                      construction in Japan. Wood         this would have the effect of allowing 
                                                                      as a building material has re-      the moisture under pressure to escape. 
                                                                      cently attracted worldwide at-      As a result, tests have confirmed that 
                                                                      tention as a sustainable mate-      spalling would be curbed to a certain 
                                                                      rial that also reduces CO . As      degree even when the concrete is ex-
                                                                                                 2
                                                                      a result, much is anticipated       posed to the heat of a violent fire. 
                                                                      from continued research and 
                                                                      development aiming to ex-           Future Research Topics
                                                                      pand the use of wood while 
                                                                      securing fire safety.               To confirm the safety performance of 
                                                                                                          buildings, the Building Research 
                                                                      Prevention of Spalling in           Institute is working on topics such as 
                                                                      Concrete Components                 analysis of the phenomena of fire, evalu-
                                                                                                          ations of the performance of fire safety 
                                                                      Combined with rebars and            measures and performance-based fire 
                                                                      steel frames, concrete is a         safety standards. Fire safety measures in 
                                                                      widely used construction ma-        buildings have long been required by the 
                                                                      terial for buildings, roads and     specifications of building regulations. 
                                                                      tunnels. Since the concrete         Naturally, the standards in these laws 
                                                                      itself does not burn, it is 
          bines a steel frame with wood (glulam)          thought that buildings made of concrete 
          as a Hybrid Timber Member.                      can withstand fire. It is certainly the case 
              We have developed posts and beams           that in normal fires, there is only discol-
          with a fire rating of one hour using the        oration to the surface of the concrete and 
          Hybrid Timber Member and we have                there is hardly any structural damage. 
          confirmed the performance by conduct-           However, in case of exposure to violent 
          ing fire resistance testing. We also de-        fires burning for a long time, spalling 
          signed a four-story office building using       occurs in the surface of the components 
          Hybrid Timber Member posts and  and damage is caused when portions of 
          beams, even erecting a part of the build-       the concrete are stripped off. Also, as the 
          ing for full-scale fire testing. As a result    surface of concrete was lost and the rein-
          of a damage survey after the fire, we           forcing steel became exposed, another 
          were able to confirm that the perfor-           problem arose whereby the steel became 
          mance of the post and beam components           extremely hot from the heat of the fire. 
          was identical to the fire resistance test,      Since buildings are at risk of collapse in 
          allowing us to ascertain the fire-resistive     a fire if the components are damaged on 
                         photos 3, 4). 
          performance (                                   this scale, it is necessary to prevent spall-
              The Building Standards Law of                                 photo 5). 
                                                          ing of concrete (
          Japan was established to limit the height,           There are various theories for the             Photo 5: Spalling in concrete com-
          number of floors and scale of wooden            spalling mechanism of concrete but the              ponents
          buildings without any acknowledgement           most plausible theory is that spongy 
          of building fire resistant buildings in         pores in the concrete are destroyed with        and regulations are the accumulation of 
          wood. However, the revised Building             increased pressure on the moisture con-         the knowledge of engineers based on 
          Standards Law of Japan (1998–2000) in-          tent when exposed to the heat of a fire.        past experiences of fire. However, as a 
          troduced performance-based provisions           Consequently, one measure to prevent            result of great progress in the fire sci-
          for the fire-resistive performance required     spalling might be to control the sudden         ence and fire safety engineering, there 
          of fireproof buildings without restric-         rise in temperature in the surface of the       are now glaring inadequacies in the 
          tions on the materials used for the             concrete, but from an economical view-          specification standards. With regard to 
          structural components, which effective-         point, it is difficult to apply fire protec-    the required fire-resistive performance 
          ly constitutes an acknowledgement of            tive covering on a broad scale.                 of buildings, aside from the specification 
          the use of wood in fire resistant build-             Another method might be to mix the         standards of the past, it is also necessary 
          ings. That is to say, it is now possible to     concrete with organic fiber to create           to undertake research in order to clarify 
          construct medium-rise buildings of four         pathways to allow the moisture content          the primary and fundamental perfor-
          to five floors using the Hybrid Timber          under pressure to escape to the outside.        mance required by the society. This is 
          Member that we have developed.                  Since organic fiber melts at a fairly low       an area that the Building Research 
              A succession of buildings using             temperature, new pores would be gener-          Institute plans to tackle in the future. 
                                                                                                                                                   11
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...International cooperation improving fire safety in buildings last month s column introducing initiatives of japan building ing material which is made with a non research institute we looked at the efforts to unravel combustible and it prevents heat from conducting mystery wind damage this issue look components as long temperature work improve resistance performance kept down well develop regulations for control possible retain certified strength standards based on clarification phenomena design addition important create compartments contain fires espite starting twen engineers result found that due or floor divided into several ty first ongoing refurbishment if breaks out high rise spain measures no were contained inside compartment din february destroyed installed where started using materials do almost whole thirty two story tower broke therefore was able not easily conduct securing widespread collapse exterior spread through gaps sufficient thickness walls floors upper stories betwe...

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