(1) Photo of T3 Building
By Raymond O’Brocki
Recently an article,Construction Concerns: IBC 2021 Heavy Timber Proposal[1], appeared in Fire Engineering that raised concerns regarding the now newly passed “Tall Mass Timber” code additions to the International Building Code (IBC) 2021 Edition. The article briefly outlined some of the central code changes that will permit tall mass timber buildings.
A brief examination of all the Tall Mass Timber (TMT) code provisions that will be included in the 2021International Building Code(IBC) will demonstrate that the fire safety protection required by the new code changes provides for the life safety of occupants and firefighters that will respond to emergencies in these buildings.
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Why These Codes Were Necessary
Brock Commons (photo 2, below)是一座在温哥华不列颠哥伦比亚大学校园的18层TMT大楼，用于学生住房。最近的一篇文章188金宝搏是正规吗stated, “Had the Brock Commons at 190 feet in height been subject to the current IBC, it could not have been built.” This is true, as well, for the current building code used in Vancouver. Despite the prescriptive barriers that existing in the current codes to TMT, they do allow for non-conforming buildings.
In Section 104.11 of the IBC 2018 Edition, and in previous editions of the IBC underthe Alternative materials, design and methods of construction and equipmentcode section, taller “beyond code” buildings have been approved under the IBC. In fact, many are currently being proposed ahead of the adoption of the 2021 IBC, which will allow for taller mass timber buildings. If the building permit applicant can demonstrate that alternate means or methods can achieve the same level of safety as what is permitted in the code, the new method or material can be approved by the code officials.
（2）Brock Commons
(3) Carbon 12
(4) T3, exterior.
Portland, Oregon, has an eight-story condominium building, Carbon 12, made of mass timber (photo 3）。它是该国最高的现代木制木材建筑。明尼阿波利斯的T3大楼（photos 1, 4) is a seven-story mass timber office building. Two new tall mass timber buildings have been proposed by New Land Enterprises in Milwaukee, one an office building the other residential.[2] Others are being proposed in Cleveland, Newark, and other cities.
Building officials needed well-crafted code provisions to guide their plans review and approval process. The International Code Council (ICC) was asked to create a committee to study the science of tall wood buildings, assess their feasibility, and, if feasible, draft code provisions that would protect the occupants and first responders. The result of the three years of committee work and fire testing produced the 14-code provision that will be included into the IBC in 2021.
Summary of the Tall Mass Timber Code Changes
IBC 602.4: New types of construction：本节创建了三种新的结构类型：IV-A类型质量木材，IV-B类型和IV-C型。这些构造类型反映了非耐燃I-A和I型I-B中的耐火等级，但是IV-A和IV-B型含有其他标准，可通过非耐燃的材料保护质量木材。
IBC 703.8: Performance-based noncombustible protection:This section provides a performance path to determine the contribution to the fire resistance rating provided by noncombustible protection, i.e., gypsum wall board. The fire-resistance rating of mass timber structural members consists of the inherent (calculated) fire resistance rating of the mass timber and the additional fire-resistance provided by any noncombustible protection as described in new definitions. This section also allows any non-combustible material to be tested to determine the time assigned for its contribution to overall fire resistance rating of the element.
IBC 703.9: Sealants at edges：需要密封剂或粘合剂来抵抗在毗邻的边缘和大规模建筑物元素的相交以及大规模木材和其他建筑元素相交的相交处，需要耐火等级。密封胶和粘合剂必须分别满足ASTM C920和ASTM D3498的要求
IBC 718.2.1: Mass timber as fire blocking: The purpose of this code change is to recognize that mass timber is a suitable fire-blocking material, similar to nominal lumber. However, it should be noted that exposed mass timber in concealed spaces is required to be protected by noncombustible materials by other sections.
IBC 403.3.2：冗余供水: Fire pumps in Type IV-A and IV-B buildings more than 120 feet in building height are required to be supplied by at least two water mains located in different streets, with separate supply piping each sized to supply the flow and pressure required for the pumps to operate. Whereas this is required for Types I and II construction at 420 feet, this section requires it at 120 feet for mass timber buildings.
IFC 701.6: Owner’s responsibility: Passive protection required for fire resistance rated building elements is currently required to be inspected and maintained by the building owner at least annually, with documentation. This section requires the owner to include inspection of the required noncombustible protection provided on mass timber building elements and repair it if necessary.
IFC 3308.4: Fire safety during construction：除非被《消防法》官员另有批准，否则大于六层楼的大型木材建设必须遵守以下要求：根据现有法规规定的立管和消防部门的供水部门的供水供应；第602.4节所需的至少一层不可抑制的保护必须安装在所有建筑物元素上，包括四个以上的楼层，包括夹层，低于主动的质量木材建设，然后建立额外的地板水平；所需的外墙覆盖物必须在所有地板上安装超过四个地面水平，包括夹层，低于主动的大型木材建设，然后再建立额外的地板水平。
IBC Table 504.3: Height in feet,IBC Table 504.4: Height in stories:IBC表506.2:允许地区每飞路r: This section amends the tables for allowable area, height in stories, and height in feet.
General Information on Type IV Construction stories and area sections:
Type IV-C:
- Maximum nine stories (only in Group B occupancies, all other are less), with no increase in height in feet above grade compared to traditional heavy timber
- 暴露质量木材允许,除了concealed spaces, shafts, hoist ways, interior exit enclosures, and outside of exterior walls
- Fully sprinklered
- Two-hour fire resistance rating throughout
- Allowable area is limited to 1.25 times the allowable area of traditional heavy timber
- Conventional wood framing (light framing) not permitted
ivb型:
- Maximum 12 stories (but some occupancies like Mercantile and Storage are much less)
- 有限的裸露内部质量木材允许（天花板面积的20％，墙壁的40％，但合并后减少）；所有其他用不可抑制材料保护的大量木材等于2/3所需的等级，包括隐藏的空间，轴，吊式方式和内部出口外壳；外墙外部需要40分钟不可抗性的保护
- Fully sprinklered
- Two-hour fire resistance rating throughout
- Allowable area is limited to 2.0 times the allowable area of traditional heavy timber
- Conventional wood framing (light framing) not permitted
Type IV-A:
- 最多有18个故事（但有些占领等居民少得多）
- 暴露的质量木材不允许（所有内部质量木材必须受到不可抑制的防护保护，等于所需的火力抗性等级的2/3），包括隐藏的空间，轴，吊式方式和内部出口外壳；外墙外部需要40分钟的不可抗性保护
- Fully sprinklered with redundant water supply when exceeding 120 feet
- 两个小时（地板）和三小时（主要的结构框架和墙壁）耐火等级
- Allowable area is limited to 3.0 times the allowable area of traditional heavy timber
- Conventional wood framing (light framing) not permitted
To review the full stories, height, and area tables being proposed go to:http://media.iccsae.org/code-development/2018-Complete-ICC-Public-Comment-Agenda-compressed.pdf
IBC 3102 and IBC Appendix D: Membrane structures with mass timber, and Appendix D Fire Districts: These code changes were developed to retain the current Type IV-HT provisions and do not modify existing requirements.
IBC 722.7: Prescriptive noncombustible protection: This section includes a prescriptive approach to achieving the required fire resistance for mass timber elements. The fire resistance rating of a protected wood element is determined by adding the calculated fire resistance rating of the unprotected wood member to the protection provided by noncombustible protection applied to the exposed wood. Two-thirds of the required fire resistance rating must be provided by the noncombustible protection. Details such as required attachment are specified and required test protocol for measuring the fire resistance afforded by the noncombustible protection is set out.
IBC 508.4 and 509.4: Fire barriers: Mass timber elements serving as fire barriers or a horizontal assembly in Type IV-B or IV-C construction must be separated from the interior of the building with an approved thermal barrier consisting of a minimum of ½ gypsum wallboard or a noncombustible equivalent, when not already required to be protected. Most elements in Type IV-B require much more protection by virtue of other sections.
Addressing Fire Service Concerns
Below is a response to several concerns that have beenoutlined involving TMT buildings in a previous188金宝搏是正规吗article.
关心：We may find that we are fighting fires in the upper floors of combustible buildings beyond the reach of our tallest aerial apparatus.
This is no different than in any other tall building. Fire suppression in floors above the reach of an aerial ladder is always a challenge. The fire resistance rating for the TMT structure is three hours in buildings above 12 stories and two hours in all others. This is identical to concrete and steel buildings of similar height. Fire has a negative influence on any building material. A three-hour fire rated assembly is just that—a three-hour rated assembly, and this is true of any building material used in the assembly. Most if not all fires start as “room and contents” fires and are readily controlled in new high-rise construction by automatic sprinkler systems.
关心：We may find ourselves more dependent than ever on fixed fire protection systems like automatic fire sprinkler and extinguisher systems, and on standpipes of various types.
Once again, this applies to all tall buildings. A Canadian study performed that examined deaths and injuries of firefighters and civilians in structure fires concluded that the construction material had no effect of whether a person was seriously injured or killed in a fire. The key factor was the presence of a sprinkler system.[3]
The fire service has always been dependent of working standpipes and sprinkler systems in tall buildings of all varieties. Sprinklers have been overwhelmingly effective and reliable. The National Fire Protection Association (NFPA) reported that “sprinklers were effective at controlling the fire in 92 percent of the fires in which sprinklers were present and the fire was large enough to activate them.”[4]
On April 7, 2018, there was a fire in a steel high-rise in Midtown Manhattan that left one man dead and six firefighters injured. It was a $2.5 million-dollar apartment that was not sprinklered.[5] The construction material was not relevant; the absence of a sprinkler system was the determining factor.
关心：We may find ourselves dependent on the proper functioning of fire pumps that are part of the building’s equipment, rather than only dependent on the fire pumps on automotive fire apparatus
消防员一直依靠建造消防泵来向高大建筑物的上层铺设水。发动机公司必须始终准备好与建筑物的消防泵压力相匹配，但如果失败了。高大的木材建筑的最大高度为18层。两家串联的发动机公司应该能够匹配（如果不超过）安装任何消防泵。更高的建筑物将对抑制措施构成更大的挑战。
关心：We may find that our fire inspectors and fire marshals will need more specialized training to ensure that these systems are maintained according to NFPA codes and standards, so that they will be reliable when they are needed.
消防检查员和消防元帅的任务是确保根据模型代码维护消防安全系统。高大的木材代码添加没有改变，并为其添加了一层保护。代码更改包括有关所有者责任的部分（IFC 701.6），该部分需要每年对所有被动火灾保护进行第三方检查。这不需要对消防检查员的任何特殊知识来审查第三方检查报告。这与在年度检查中审查年度火灾警报和喷水仪报告相同。
关心：我们可能会发现，我们的消防员和消防员需要更专业的培训来有效地使用这些系统，以应对这些建筑物之一的火灾警报
The only specialized training needed to respond to a TMT building is training in high-rise operations. These buildings will perform as any high-rise building in the event of a fire.
关心：We may find that we need more detailed pre-incident plans for buildings like these, and for the occupancies located in them, than we have in place for many of our present buildings
NFPA 1620,Standard on Pre-Incident Planning，呼吁所有建筑物和消防人员的详细预生工计划应熟悉其第一警报区的所有建筑物，尤其是高层建筑物，复杂的建筑物以及他们所识别的任何目标危害。TMT建筑物的前计划不需要任何级别的细节或精致，而超出了目前的其他高层建筑物目前拥有的。
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关于TMT建筑消防问题must be presented with an understanding of the veracity of fire protection systems. In most cases they are the same concerns that firefighters should have for any tall building. The difference is that tall mass timber buildings, while not a new phenomenon in other parts of the world, are new to this country. That is why the committee that proposed these code additions built in redundant and robust fire protection features. But it is imperative for fire service personnel to educate themselves on all types of building construction and materials and to become intimately familiar with all large buildings and complex structures in their jurisdiction.
REFERENCES
[1] Havel, Greg,Construction Concerns: IBC 2021 Heavy Timber Proposal,//www.sacthai.com/articles/2018/12/construction-concerns-ibc.html,appeared December 28, 2018.
[2] Hughes, C.J.,Log Cabins? No, These Wooden Buildings Are High Rises,https://www.nytimes.com/2019/01/01/business/timber-wood-construction-real-estate.html，出现在2019年1月1日。
[3] Garis, Len and Clare, Joseph, Fire Outcomes by General Construction Type: A Retrospective Analysis of British Columbia Reported Fires, University of the Fraser Valley: February 2014.
[4] Ahrens, Marty,U.S. Experience with Sprinklers, NFPA: July 2017.
[5] Lucero and Peiser,Fire at Trump Tower Kills One, Police Say,New York Times online,https://www.nytimes.com/2018/04/07/nyregion/trump-tower-fire.html, retrieved January 4, 2019.
RAYMOND O’BROCKI,CBO, is the Manager of Fire Service Relations for the American Wood Council. Before that he was the chief building official for the city of Rockville, Maryland. He retired as the assistant fire chief the Baltimore City (MD) Fire Department in 2013. He was appointed fire marshal for Baltimore City in 2008. O’Brocki has served on the Maryland State Child Care Advisory Council, Maryland State Fire Code Update Committee, and the steering committee for the Mid-Atlantic Life Safety Conference. He has served on the NFPA Urban Fire Safety Task Force and is on the NFPA 1 technical committee. O’Brocki is the administrator of the Construction Fire Safety Coalition. He is a graduate of the University of Baltimore School of Law and a licensed attorney.
