Study On Collapse Mechanism Of Long-Span Reticulated Structures And Its Multi- Dimensional Earthquake Isolation And Mitigation Control

From the birth of space reticulated structures in early 20th century, due to their specific advantages of long span and light weight, they have become important structural styles in large structural engineering. These structures are always used as public facilities in places that hold huge number of people, for example, railway stations, stadiums and so on. The collapse of these structures would cause great casualties and huge economic loss. Additionally the space reticulated structures always cover a long span and have numerous bars. As a result of long span and massive bars, the structures will fall to great nonlinear mechanical behavior, which bring great difficulties to the structural designer to understand the seismic performance of such structures and determine whether the failure and collapse of structures will occur under certain loads.This thesis is supported by Chinese National Nature and Science foundation "study on collapse mechanism of long span reticulated structures under the multi-dimensional earthquakes and their isolation and mitigation control". Theoretical derivation, numerical calculation and experimental test are performed to study the dynamical response and failure mechanism, damage process and collapse mechanism of the structures. A characteristic index is proposed to describe the total failure of structure. The law of the energy transition in the elements of the structures is studied. The inner connection of the energy transition, distribution, dynamic response and damage are studied. The main work and conclusions are listed below:1. The elastoplastic stability criterion based on energy method are proposedBased on the elastic stability degree index, an elastoplastic energy stability criterion are proposed to describe the total failure of structures. This criterion can directly determine whether the structures are collapse or not in a specific external loads. Comparing to the traditional method to determine the collapse by incremental dynamic analysis, the method using the elastoplastic energy stability critical index saves a lot of computing time. A classical Hexagram Goethe Scott dome net shell is analyzed and the result implied that this criterion is reasonable, and can be used as an allied method to determine whether the structure is failure or not.2. The failure determination of a double layer lattice based on the elastoplastic stability criterionThe elastoplastic energy stability criterion are used to determine the failure of a double layer lattice. The inner connection of the criterion and the strength and displacement are studied. The results imply that, the proposed criterion can determine the structural collapse clearer than the traditional incremental dynamic analysis. Besides the elastoplastic stability criterion can reveals the inner laws of large reticulated structures, and is safer.3. The energy transition and distribution law of the earthquake energy in the structuresThrough the whole process of double non-linear dynamic time history analysis, the law of energy transition and distribution in the long-span reticulated structures is studied, and the inner connection of energy transition, distribution, dynamic response, element inner force and structural damage are revealed.4. The study on the effectiveness of the vibration control on the multi-dimensional earthquake isolation and mitigation devices on long span reticulated structures.Base on the performance test and sturdy of multi-dimensional earthquake isolation and mitigation devices (China Pattern, approved number:ZL 200610097219.3), analysis method and finite element model are established. The dynamic analysis, damage process and failure mechanism of the long-span reticulated structures with the devices are studied. The effect of the device on the seismic ability of long-span reticulated structures are studied and the results imply that the multi-dimensional earthquake isolation and mitigation devices can reduce the failure of the structures and control the collapse of the long-span reticulated structures.5. Shaking table tests on structures without and with the multi-dimensional earthquake isolation and mitigation devicesShaking table tests are performed on structures without and with the multi-dimensional earthquake isolation and mitigation devices. The influence of different earthquake waves, different amplitude on the dynamic characteristic and response are studied. The results imply that the devices can indeed improve the seismic capacity of the long-span reticulated structures, and the analysis method and finite element model is reasonable and correct.Innovations of this paper are mainly reflected as follows:(1) The elastoplastic energy stability criterion are proposed to determine the failure of long-span reticulated structures.(2) The law of energy transition and distribution in the long-span reticulated structures is studied, and the inner connection of energy transition, distribution, dynamic response, element inner force and structural damage are revealed.(3) Shaking table tests are performed on structures without and with the multi-dimensional earthquake isolation and mitigation devices. The seismic isolation and mitigation performance of the device are verified. The results valid that the seismic capacity of the device, the effectiveness of the proposed analysis method and numerical mode are correct and reasonable.