Abstract

Crawler crane designers continually extend the height of the machines. Models that reach over 500 feet high are commercially available. Of course, as the crane height increases, so do the hazards associated with tip-over accidents. Destabilizing tip-over moments are generated by the boom and the suspended payload when they extend beyond the base of support. Stabilizing moments are generated by the crane base and counterweights. Counterweights are normally secured by mechanical fasteners such as pins, bolts, or chains. However, some cranes use unrestrained counterweights that are held in place only with friction. This paper investigates the dynamic behavior of such unrestrained counterweights during tip-over accidents. The analysis shows that counterweight blocks can break free and slide off the crane when the tip angle is as small as 20 degrees. Scale-model testing of cranes with unsecured counterweights demonstrates that the fall path of the spilling counterweights on certain crane models intersects the operator cab and thus presents a deadly hazard.

摘要

履带式起重机设计师不断地扩展机器的高度。高度超过 500 英尺的型号已在市场上销售。当然，随着起重机高度的增加，与翻倒事故相关的危险也会增加。当悬臂和悬挂的有效载荷超出支撑底座时，会产生不稳定的倾翻力矩。稳定力矩由起重机底座和配重产生。配重通常由机械紧固件固定，例如销钉、螺栓或链条。然而，一些起重机使用无约束的配重，仅通过摩擦固定到位。本文研究了这种不受约束的配重在翻倒事故中的动态行为。分析表明，当倾角小至 20 度时，配重块可以脱离起重机并从起重机上滑落。