| As the China urbanization process accelerates,the scale of construction project keeps escalating and the amount of tower cranes has reached nearly 400,000 units.Tower crane is the lifeline of building construction,but tower crane accidents have continued to occur.Tower crane safety is a complex sociotechnical system problem involving the interaction of technology and society subsystems.The systematic research of the tower crane accident causation mechanism,risk evolution rule and safety monitoring method are of great significance to reduce the accident rate.This thesis studies the accident causation mechanism of the tower crane and risk evolution rule of the tower crane whole process from the complex sociotechnical system perspective.The concept of overall robustness and process operation safety theory are established.The monitoring methods for the tower crane structure safety(TCSS)and tower crane process operation safety(TCPOS)are developed.The front-end-early-warning monitoring system for the tower crane safety is built based on the Internet of Things(IoT).The main research contents are as follows:(1)The five components,five layers and 56 contributing factors of the tower crane safety system were analyzed from on the complex sociotechnical system perspective.The mixed methods research(consistency parallel design)were conducted to study the system.The accident causation model of the tower crane was established based on the Acci Map,and the nine factor dimensions and key factors of the tower crane safety were identified based on the principal component analysis and statistical importance ranking.The tower crane safety is an emerging property under the complex sociotechnical system.The tower crane accident results from the lack of feedback and vertical integration of the multi-level of the system.The idea to follow the overall system and dynamic control principle and focus on the horizontal and vertical integration of the system level was established for the tower crane safety management.(2)The risk identification framework was constructed for the tower crane whole process.The risk elements(i.e.risk influence factors,critical events,accidents and consequences)and evolution paths of the tower crane whole process were identified according to the accident causation mechanism and the nine factor dimensions.The risk assessment method was established based on the Intuitionistic Fuzzy Sets(IFS)and Bayesian Belief Network(BBN).The risk models of the tower crane whole process under the complex uncertainties were designed and verified.The risk of each stage of the tower crane has the complex sociotechnical system characteristics.The risk control directions of the tower crane whole process include the structure intrinsic safety,functional component safety and process operation safety.(3)The concept of overall robustness was proposed to describe the integrity loss of the tower crane structure caused by the failure of the connection structure.The tower crane structure system and key control issues of the TCSS were analyzed.The monitoring system and measures of the TCSS were established based on the overall robustness.The TCSS early-warning system were constructed,which consists of the multi-layers(the indicator,performance,component and structural system layer)and multi-states(the red,orange,yellow and green warning).The TCSS early-warning management framework were built,which contains the information management,early-warning analysis and safety emergency layer.The early-warning evaluation model for the TCSS was established based on the Cloud Model and D-S evidence theory.The feasibility of the monitoring and early warning methods were verified through the actual case.(4)The safety of the construction activity that has the logical process was defined as the process operation safety(POS).Based on the ontology theory,the POS ontology was constructed to standardize the process,parameters and risks of the TCPOS.Based on the Data Acquisition System(DAQ)and Finite State Machine(FSM),the logical association mappings among the work steps,process,process parameters and safety alerts of the POS were built to reach the parameterized monitoring of the TCPOS.The control objectives,control structure and control strategy of the POS were formulated based on the cybernetics to realize the automatic control of the TCPOS.The feasibility of the TCPOS monitoring methods were verified through the actual tower crane climbing activity.(5)According to the monitoring methods of the TCSS and TCPOS,the characteristics and function requirements of the monitoring system were detailed.The monitoring system architecture was designed to deploy the localized resources of computing,network and storage.The architecture consists of the sensor layer,network convergence layer and management control layer.The architecture could provide the localized functions of data sensing,network transmission and data processing for the monitoring system and support the front-end-early-warning of tower crane safety.The front-end sensing devices,mid-range transmission devices,and terminal transceiver devices were developed based on the IoT.The hierarchical topology transmission scheme based on RFID-WIFI was constructed,and the tower crane safety monitoring software system was developed. |
