The crane collapse danger zone modeling project seeks develop models to predict the area that may be at risk should the crane collapse or drop its payload. Probability analysis regarding where the payload or crane sections may pass through or land at can then be used to inform decisions regarding where to restrict access.
A number of sub-models may be combined to obtain a complete model for use in danger zone analysis. Subtopics that may be combined to develop the full model include:
- Modeling the effect of wind loads.
- Determining the stability characteristics of tower cranes at various stages of assembly and disassembly.
- Modeling falling payloads or crane sections as well as the impact of crane sections, payloads, or other debris with the surrounding environment and the behavior of these large objects as the bounce, tumble, and/or roll after initial impact.
- Modeling the separation of tower crane sections.
- Modeling the structural deformation caused by bending and shock loading of tower crane sections.
Modeling the effects of wind loads
Modeling the external loads on crane structures due to wind is necessary for understanding how the structure may collapse and the behavior of the falling debris. Currently an approach modeling the effect of wind on each bar in the lattice structure individually is being investigated for use in evaluating the effect of wind on the entire structure. Additionally, the impact of wind directionality and gust frequency may influence the collapse behavior of tower crane structures. Thus, these parameters will be varied in simulation to obtain a full understanding of the impact of wind loading.
Research efforts related to modeling the effects of wind loading are explained further on the Wind Load Modeling page.
Stability characteristics during various stages of assembly and disassembly
Given the configuration status and the externally applied loads, the stability characteristics of a tower crane will vary. If the external forces are large enough and applied in a direction with limited stability, then the tower crane may tip over or experience structural failure. These stability characteristics will be investigated to determine under what conditions the crane will tip over or collapse.
Crane and payload modeling during free fall, impact, bounce, tumble, and roll
Understanding the behavior of debris during free-fall and following impact with the surrounding environment is critical in determining which areas are at risk during a potential crane collapse. To this end an experimental setup is in development to track the free-fall and bounce of a known payload. The release of the known payloads at varying states may be used to evaluate the appropriateness of various contact models for use in simulation.
Separation of tower crane sections
The separation of tower crane sections is in part being investigated by developing a simulation of tower crane cab removal during disassembly. This work is detailed further in Crane Section Lift-Off Modeling.
However, separation may also occur due to structural failure. To this end a methodology was developed to permit a simulated crane structure to move together as a single rigid body or move independently as multiple sub-assemblies following an event-driven transition. The current software was kept general to accommodate more complicated architectures that will be investigated in the future. To fully implement this approach, it will be necessary to develop an understanding of the conditions under which failure will occur.
Structural deformation caused by bending and shock loading
As falling sections and debris contact the ground or other objects in the surrounding environment they experience large impact forces that can lead to permanent structural deformation. The goal of this sub-model is to determine if deformation occurs for each section, update the configuration of the sections that have deformed in the model simulation, and track this over time for each section as they tumble, bounce, and/or roll.