Investigating Lateral Buckling of Joists as a Cause of Falls from Elevation

调查托梁横向屈曲导致高处坠落的原因

• 批准号: 7313848
• 负责人: Daniel P Hindman
• 金额: $ 21.32万
• 依托单位: VIRGINIA POLYTECHNIC INST AND ST UNIV
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7313848
• 关键词: Investigating; Lateral; Buckling; Joists; Cause

DESCRIPTION (provided by applicant): Falls from elevation are a leading cause of fatalities and injuries among construction workers, especially in the residential construction industry. The majority of existing evidence regarding falls from elevation has described the demographics and occupational tasks of the victims, but little information is available on the causes or events that initiate fall incidents. A review of case reports suggests that lateral buckling of unbraced I-joists may be an important contributor to worker falls. Lateral buckling is an instability condition of beam failure where the beam twists out of plane. Beams or joists which undergo lateral buckling return to their undeformed state when the load is removed (fall has occurred). Falls caused by lateral buckling are most likely to occur when workers are installing temporary bracing or sheathing to unbraced joists and are walking from the end support towards the center of the joists. Lateral buckling can easily be prevented by providing clear direction to workers on what sections of a beam can be safely accessed for construction purposes, representing substantial savings in lost time and medical expenses. Little research has been published on the lateral buckling of wood I-joists, which are currently used in the majority of residential wood structures. The goal of this research is to explore the relationship between construction worker loadings and mechanical behavior causing lateral buckling of wood composite I-joists. First, observations of construction activities performed by workers on unbraced beams will be made. Next, a group of construction workers will perform these same activities in the laboratory environment where the loads caused by construction activities can be measured. A series of lateral buckling models will be created to describe the load where buckling occurs. Verification of these models will include experimental testing of lateral buckling using loads identical to those measured from construction activities. Based upon the loads measured due to worker activities and the modeling and subsequent experimental validation of lateral buckling loads for I-joists, safety strategies to prevent falls from elevation will be formulated.

描述（由申请人提供）：从高处坠落是建筑工人伤亡的主要原因，特别是在住宅建筑行业。关于高处坠落的大多数现有证据都描述了受害者的人口统计和职业任务，但关于引发坠落事件的原因或事件的信息很少。对病例报告的回顾表明，未支撑的工字梁的侧向屈曲可能是工人摔倒的重要原因。侧向屈曲是梁破坏时的一种失稳状态，是指梁扭曲出平面。经过侧向屈曲的梁或托梁在卸除荷载（发生了下降）后恢复到未变形状态。当工人在未支撑的托梁上安装临时支撑或护套，并从末端支撑走向托梁中心时，最容易发生由侧向屈曲引起的坠落。通过向工人明确指示梁的哪些部分可以安全进入施工目的，可以很容易地防止横向屈曲，从而节省大量的时间和医疗费用。目前在大多数住宅木结构中使用的木材i型托梁的横向屈曲研究很少。本研究的目的是探讨建筑工人载荷与引起木复合工字梁侧屈曲的力学行为之间的关系。首先，将对工人在无支撑梁上进行的施工活动进行观察。接下来，一组建筑工人将在实验室环境中进行这些相同的活动，在实验室环境中可以测量由建筑活动引起的负荷。将建立一系列横向屈曲模型来描述屈曲发生的荷载。这些模型的验证将包括侧向屈曲的实验测试，使用与施工活动中测量的荷载相同的荷载。基于工人活动所测量的载荷，以及工字梁横向屈曲载荷的建模和随后的实验验证，将制定防止高处坠落的安全策略。