Researches On Mechanics And Optimal Control Of Spatial Steel Structure Construction

In recent years, spatial steel structure is widespread in large-scale public buildings with increasingly novel structure system, expanding complicated layout and progressively larger scale. It has already become one of the most essential fields for modem building structures. The rapid development of spatial steel structure makes a higher request to construction technology.Firstly, state-of-art is reviewed domestic and international of spatial steel structures construction technique and construction mechanic. Based on construction mechanics, several resolvent and rationalization proposal are present for construction of complicated large-scale spatial steel structure.Theoretical basis of spatial steel structure construction mechanic is analized. Large deformation spatial beam elements equations are derived. The theory of existing two operational methods, i.e birth-death element and multi-stage construction algorithm are analysized. The merits and drawbacks, imorovement measures of the two theories are dissected combined with commonly-used construction methods.Temperature compensation method during tension construction of spatial steel structure is present. The effect of temperature changes to beam elements is analyzed, then based on the theory of controlling initial length, an algorithm to adjust cable tension according to temperature changes is proposed. The characteritic effect of temperature changes to pre-stressed cylindrical latticed shell structure, cable suspan dome and tensile cable net structure are analyzed.Due to significant interrelationship between each tension construction stage of the second type of pre-stressed spatial steel structure, an index reflected the oscillation of cable force during tension construction is proposed. The effect of unprestressed cable length to tension construction is analysized. Based on Genetic alogrithm, an algorithm with real-valued encoding is proposed to optimize the sequence of cables tensioned in groups, with constraint condition of the optimization introduced into object function by penalty function method.Take consideration of equilibrium equation and compatible equation, 3 kind of equilibrium state determination of the structure during hoistiong process are analysized with semi-analytical method: 1) When spatial steel structure is hoisted with one crane, and in a special posture; 2) When spatial steel structure is hoisted with one crane, and the length of cable is given; 3) When spatial steel structure is integral hoisted with several cranes, and in a special posture.Based on improved Genetic Alogrothm, A method to optimize the falsework layout of spatial steel structure is present with structure strain energy as object function. When the search area was regular, continuous spatial location was selected as search variable; otherwise discrete node was selected as search variable. Gray code was adopted to encode chromosome. A method to determine the length of chromosome is present.