在木结构建筑中创建高效的结构网格

大量木材产品，如交叉层压木材(CLT), nail-laminated timber (NLT) and glue-laminated timber (glulam) are at the core of a revolution that is shifting how designers think about construction. At no time has materials selection been such an integral aspect of the building designer’s daily responsibilities. 除了它的可持续性和低碳足迹, 大量木材的好处包括增强美学, speed of construction and light weight, all of which can positively impact costs. However, 让业主和开发商相信大量木材的解决方案是可行的, 结构设计也必须具有成本竞争力. This requires a full understanding of both material properties and manufacturer capabilities.

大量木材通常用于办公室等项目, schools and tall mixed-use buildings, 通常假设结构网格. 旨在满足租户灵活性的需求, 这些“默认”网格与历史上使用的材料的能力保持一致.e., steel and concrete. 当涉及到为大量木材铺设结构网格时, 方钉/圆孔的类比是恰当的. Although a mass timber solution may work economically on many grids conducive to steel/concrete framing, some grid modification may be valuable. Trying to force a mass timber solution on a grid laid out for steel and concrete can result in member size inefficiencies while negating opportunities related to manufacturer capabilities. 因此，设计大型木结构建筑至关重要 as a mass timber building from the start. 这需要彻底了解如何最好地布局结构网格, without sacrificing space functionality, 优化成员大小——但成本效率比列间距更重要.

The following considerations are based on a post-and-beam frame for occupancies such as offices; however, 许多也适用于其他占用类型的承重墙支撑系统.

Grid Selection

Simplistically, there are two main grid options for mass timber buildings: square and rectangular. 在决定使用哪一种时，有许多因素需要考虑.

To determine efficient grid spacing, 了解大质量木地板的可能跨度范围是很重要的. Due to their relative light weight, allowable spans for these panels are often governed by vibration and deflection rather than bending or shear capacity. In addition to panel vibration design, 框架系统的整体振动性能, including beams, should be taken into account. The table below illustrates example ranges based on panel size, assuming stiff supports. (Each project’s specific span, loading and support conditions, 以及制造商特定的设计属性, 在选择面板厚度时应该考虑到什么.) For more details on the structural design of mass timber floor panels, contact your local WoodWorks Regional Director or email the WoodWorks help desk at help@ilovehermitcrabs.com. For additional information, see the Structure magazine article, 交叉层压木结构地板和屋顶设计, and Nail-Laminated Timber: U.S. Design and Construction Guide.

Based on completed buildings in the US, square grids tend to be in the range of 20×20 to 30×30 ft. Although a mass timber panel may be able to span the 20-ft distance between support beams in a 20×20-ft grid, an alternate method would be to include one intermediate beam within each bay to reduce the span of the mass timber floor panel. For example, a 20×20-ft grid could have one intermediate beam so 3-ply CLT floor panels spanning 10 ft can be used. This scenario was used for the Albina Yard 俄勒冈州波特兰的办公楼(上图). Larger square grids such as 28×28 or 30×30 ft with one intermediate beam can also be used. This typically results in the use of 5-ply CLT or 2×6 NLT floor panels, spanning 14 or 15 ft. This scenario was used for Clay Creative, also in Portland (pictured below). 一般来说，较薄的地板和屋顶板可能会降低材料成本. However, lower horizontal panel costs may be offset by higher beam (and perhaps column) costs, 额外的中间波束也需要与MEP系统协调. 因此，更厚的地板和更少的梁的成本分析. 可能需要更薄的地板和更多的横梁.

Going much beyond a 30 or 32-ft span with glulam girders starts to require fairly large (deep) beams. It can be done, but economics and headroom issues may outweigh the benefits of longer spans. 下图说明了几个方形网格选项和相关的成员大小.

矩形网格通常在12×20-ft到20×32-ft的范围内. The main difference with a rectangular grid is that intermediate beams tend not to be used, 常常简化适应环境保护的方法. The narrower grid dimension is typically based on the span capability of the floor panel (see table of span ranges above). 较大的网格尺寸主要基于程序化布局, 同时考虑到胶合板的经济跨度. 使用此场景的项目包括 First Tech Federal Credit Union 在俄勒冈州的希尔斯伯勒，他们使用了一个5-1/2英寸的12×32-ft网格. CLT panels spanning 12 ft, and the 111 East Grand Office 它使用了一个20×25-ft网格和2×8-ft DLT面板，跨度为20英尺. Both projects are pictured below.

消除中间梁有几个原因, 但设计团队经常引用的是更容易的MEP协调. Since exposing the mass timber floor panels on the ceiling side is desired in most mass timber buildings, some creativity in how ductwork, 需要配备洒水管路和其他MEP服务. 有关此主题的更多信息，请阅读本文 WoodWorks Ask an Expert Q&A. If there are no intermediate beams, the main MEP trunk lines can be run around a central corridor with branch lines extending into each bay. A benefit to this approach is that no intermediate beams means no or minimal penetrations through glulam purlins or girders to coordinate, cut, design for, etc.

Manufacturer Input

When selecting grid dimensions, another important consideration is manufacturer capabilities. Most North American CLT manufacturers certified to the PRG-320 Standard for Performance-Rated Cross-Laminated Timber are capable of producing panels between 8 and 12 ft wide and between 40 and 60 ft long. 最大限度地减少每个面板的浪费量是提高效率的关键. For example, a grid with 20-ft increments could be very efficient; it could use 40-ft-long panels or 60-ft-long panels (if the manufacturer is capable of producing those sizes). On the other hand, a 24-ft grid may not be as efficient since it would either require 48-ft-long panels (for double spans) or cutting 16 ft from 40-ft-long panels. 这两种选择都增加了浪费，降低了效率. When considering especially long panels, trucking logistics should also be taken into account.

The University of Arkansas Adohi Hall 费耶特维尔学生宿舍项目, AR在60英尺宽的建筑中使用了20英尺的网格增量. CLT制造商提供了40英尺长的面板, resulting in the use of one full length and one half-length panel to achieve the full 60-ft building width. 因为每一块半长面板都是将全长面板切成两半, 效率高，浪费少.

While manufacturer capabilities differ, 创建对几个制造商都有效的网格是可能的. An important step in mass timber building design is to consult with manufacturers to determine the most efficient panel layouts for their capabilities. 大多数北美木材制造商都是WoodWorks国家合作伙伴. 每个网站的信息都可以通过点击图标找到 this webpage.