Large web openings in steel and composite beams
This paper presents the basis for the design of steel and composite beams with large web openings. The main design requirements are the transfer of shear by Vierendeel bending and the control of web buckling next to and between the openings. Cellular beams with regular circular openings are a common example of highly perforated beams and their flange areas are often highly asymmetric. For these beams, web-post moments may be generated to develop the full shear resistance of the cross-section. Tests on beams with circular, elongated circular and rectangular openings are presented which are used to verify the design methodology. In addition, the openings cause local displacements due to shear and bending, which add to the overall deflection of perforated beams. Simplified formulae are presented to determine the additional deflection relative to the equivalent solid-web beams.
钢和复合梁中的大腹板开孔
本文为大腹板开孔钢梁和复合梁的设计提供了依据。主要设计要求是空腹弯曲的剪力传递和开口附近和开口之间的腹板屈曲控制。具有规则圆形开口的蜂窝梁是高度穿孔梁的常见例子，其翼缘区域通常高度不对称。这些梁可能会产生腹板后力矩，导致整个截面承受剪切载荷。本文对圆形、细长圆形和矩形开孔梁进行了试验，验证了设计方法。此外，开孔处由于剪切和弯曲而引起局部位移增加了穿孔梁的整体挠度，本文也给出了相对于等效实腹梁的附加挠度的简化公式。
1 Introduction
Steel and composite beams are often designed with large web openings for routing services or for roofs or other long-span structures. Castellated beams with hexagonal openings and cellular beams with circular openings are formed by cutting and rewelding IPE or UB sections so that the resulting beams are deeper and therefore stronger than the parent section for the same section weight. Castellated beams are manufactured with lsquo;standardrsquo; hexagonal shapes in which the openings are two-thirds of the final section depth. Cellular beams are much more variable in terms of their component section shapes and the size and spacing of the openings. Circular openings amounting to 60 to 75 % of the beam depth are typical.
1引言
钢和复合梁通常设计有大型的腹板开孔，用于管路布置或屋顶或其他大跨度结构。带六角形开口的蜂窝梁和带圆形开口的蜂窝梁是通过切割和重新焊接IPE或UB截面形成的，因此在相同截面重量下，使梁更高，比原截面的梁更强。六角形开口蜂窝梁采用“标准”六角形制造，开口为最终截面深度的三分之二。圆形开口的蜂窝梁在其构件截面形状以及开口的尺寸和间距方面变化更大。典型的圆形开口占梁深的60%至75%。
Often, IPE and HE sections are combined to create highly asymmetric sections, as shown in Fig. 1, which are efficient when used in composite construction. Elongated circular openings can be created by cutting away the webpost between circular openings, although these elongated openings are generally placed close to mid-span where shear forces are low.
通常，IPE和HE截面结合在一起形成高度不对称的截面，如图1所示，这在复合结构中使用时是有效的。细长圆孔可通过切断圆孔之间的腹杆来创建，尽管这些细长孔通常放置在剪切力较低的中跨附近。
Fabricated beams are made by welding together three plates, and these beams generally have large rectangular openings at isolated positions. Horizontal stiffeners are often welded above and below the openings to increase the resistance to transfer of shear forces by Vierendeel bending across the openings.
装配梁由三块板焊接而成，这些梁通常在隔离位置有大的矩形开口。水平加劲肋通常焊接在开口上方和下方，以减少通过开口的空腹弯曲传递的剪力。
1.1 Design requirements for beams with large web openings
The following design verifications of the structural adequacy of steel and composite beams with isolated or closely spaced openings should be carried out:
图1由两个型钢制成的蜂窝梁（来源：Kloeckner Metals UK）
图2不同开口形状的装配梁（来源：Severfield plc）
– Bending resistance of the reduced section based on the plastic or elastic section properties of the perforated sections, depending on the section class of the unsupported web.
– Shear resistance of the reduced section to existing Eurocode rules.
– Section class of the Tees in Vierendeel bending, which determines whether the plastic or elastic properties of the Tees may be used.
– Interaction of shear and axial forces on the bending resistance of the Tees.
– Contribution of local composite action in the Vierendeel bending resistance for composite beams. – Web buckling next to isolated openings.
– Web-post buckling between closely spaced openings.
– Effect of in-plane moments that may develop in the webposts for highly asymmetric sections.
– Additional flexural and shear deflections due to the web openings.
1.1大腹板开孔梁设计要求
应进行以下设计验证，以验证带有隔离或紧密间隔开孔的钢和复合梁的结构充分性：
-根据穿孔截面的塑性或弹性截面特性，根据无支撑腹板的截面类别，降低截面的抗弯强度。
-降低截面的抗剪强度符合现行欧洲规范的规定。
-空腹弯曲中T形的截面等级，决定了T形的塑性或弹性性能是否可用。
-剪切力和轴向力对T形弯曲阻力的相互作用。
-局部复合作用对复合梁空腹抗弯性能的贡献。
-隔离开口旁边的腹板屈曲。
-紧密间隔开口之间的腹板后屈曲。
-平面内力矩对高度不对称部分的影响。
-由于腹板开口而产生的额外弯曲和剪切变形。
The potential modes of failure are shown in Fig. 3. The effect of the openings is mainly to reduce the shear resistance of the beam. Web buckling next to or between the openings is normally the critical design condition. These design verifications are reviewed in the following sections.
潜在失效模式如图3所示。开孔的后果主要是减小了梁的抗剪强度。开孔附近或开孔之间的腹板屈曲通常是关键设计条件。这些设计验证将在以下章节中进行审查。
1.2 Proposed Eurocode rules for web openings
The design method for steel beams with web openings will be presented in a proposed Part 1.13 to EN 1993 [1] and the supplementary rules for composite beams will be included in new clauses in EN 1994-1-1 [2]. The scope of EN 1993 Part 1.13 will be based on design verifications already included in various national guidance documents [3], [4], and background information is based on research carried out in ECSC/RFCS projects, notably LWO (2002– 2005) [5] and DISCCo (2012–2015) [6].
1.2拟议的腹板开孔欧洲规范
带腹板开孔的钢梁的设计方法将在EN 1993[1]的建议第1.13部分中介绍，复合梁的补充规则将包含在EN 1994-1-1[2]的新条款中。EN 1993第1.13部分的范围将以各种国家指导文件[3]、[4]中已包含的设计验证为基础，背景信息以在ECSC/RFC项目中进行的研究为基础，特别是LWO（2002-2005）[5]和Discco（2012-2015）[6]。
The scope of the rules for large web openings is based on defining an equivalent rectangle for more regular opening shapes such as circular, elongated circular and hexagonal openings. The treatment of Vierendeel bending and web-pos
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