Human-Structure Interaction Based On 2DOF Bipedal Model And Its Parameters’ Effect

With the widespread development of long-span, slender and low-frequency structures in modern civil engineering, human-induced vibrations attracted great public attention. Human-structure interaction is an important but relatively new consideration. As independent dynamical system, crowd on structure can induce dynamic forces and change the dynamic properties of structure. And structure vibration also make crowd adjust motion state and influence forces induced by human. Bipedal model has been employed to simulate human-structure interaction problem. But the current bipedal model cannot describe whole-body vibrations. Stability and parameter domains for stable walking are not clear. And there is a lack of proper control mechanism for stability of bipedal running model. The mechanism of crowd-structure dynamic interaction by a probabilistic approach cannot be studied using this model.Aiming at these problems above,2DOF bipedal model is developed based on the ISO 5982 model and bipedal model. The stability of 2DOF bipedal model, modelling of human-structure interaction process, control mechanism for stability running and structure vibration response induced by crowd are analyzed. The main contents and achievements of this paper are as follows:(1) Based on the ISO 5982 model describing whole-body vibrations and bipedal model describing bipedal nature of human locomotion, a 2DOF bipedal model was introduced, and parameter domains for stable walking are proposed. The dynamic equations of human walking are established by means of the Lagrange equation. The dynamic characteristics and energy change process of human locomotion is studied. The effects of leg stiffness, impact angle and walking speed on the reaction force of ground are analyzed. Centering on the stability of 2DOF bipedal model, parameter domains are studied. The research results show that 2DOF bipedal model can be used to simulate human periodic walking cycles consisting of single and double support phases. The total energy of the model during continuous walking is constant, while energy transfer occurred between gravitational potential energy, elastic potential energy and kinetic energy. Variations of leg stiffness, impact angle and walking speed have a greater effect on walking characteristics. These parameters are interrelated and 2DOF bipedal model can only converge to steady-state walking at parameter domains proposed. It is notable that total parameter domains for stable locomotion include parameter domains matching walking characteristics and parameter domains do not matching walking characteristics. And the parameter domains matching walking characteristics are just one out of the many stable solutions to locomotion of the model.(2) The modelling of human-structure interaction is presented. Based on 2DOF bipedal model considered human dynamic characteristic, the dynamic equations of human-structure system are established by means of the Lagrange equation. The basic theory and algorithm implementation are studied. Dynamic response and interaction of human and structure are analyzed. The process of human motion is presented. And effect of human dynamic characteristic on structure vibration is also analyzed. The results show that human-structure interaction will increase with a large vibration level of the structure. Human can affect structural vibration and structure vibration can also in turn influence human behavior. The mode frequencies and damping radios in any mode of structure reach the minimum and maximum respectively, while human walking pass the peak of each corresponding mode shape. Human whole-body vibration characteristic has abated effect on human-structure interaction. And 2DOF bipedal model could well describe human-structure interaction.(3) The modelling of human-structure system under human running is studied. Based on 2DOF bipedal running model, a new feedback mechanism which included swing-leg retraction and control force is proposed to maintain stable running. The mechanical characteristics, control process, energy change and stability in running are studied. And the dynamic response of structure under 2DOF bipedal running model is also analyzed. The results show that 2DOF bipedal model can reproduce periodic running cycles consisting of support and flight phases. The new feedback mechanism allows the running model to automatically adapt the motion state and compensate for energy dissipated. The stability of running model is significantly improved. When human runs across the structure, the max increase amplitude of ground reaction force under running is 1.48%. The human-structure dynamic interaction is weak when human run.(4) The dynamic response of structure subjected to stochastic crowd by considering interaction between crowd and structure is studied based on 2DOF bipedal model. The dynamic equations of crowd-structure system are established. And the basic theory and algorithm implementation are studied. The results show that the structure response and effect of crowd-structure interaction will be larger with the increase of crowd density and synchronization proportion. The dynamic characteristics of structure is associated with crowd density and distribution, presented as frequency reduction and damping increment. The response of system considered crowd-structure interaction is noted to be larger than the response induced by single person. It is necessary to use 2DOF bipedal model describe the dynamic interaction between crowd and structure.