Theoretical And Experimental Research For The Construction Control Of Suspen-Dome Structures

Suspen-dome system is a prestressed long-span spatial hybrid structure,which consists of the topmost single-layer dome and the bottom tensegrity system,and it has been widely applied around the world due to its novel appearance,excellent structure properties and low difficulty of construction.However,there are still some problems in process of tension constrction and actual using.In order to promote the application of this kind of structure to practical engineering, this article carried out deep study on prestress optimization,adjustment on defect state,effect of friction in sliding-cable during tension construction,design of new joints and model experiment in the suspen-dome system.First of all,this paper set up an optimization mathematical model of prestress in suspen-dome structure,taking the prestress level of each hoop cable for variable,the lowest total prestress level of each hoop cable,the minimum value of horizontal radial support reactions,and the minimum peak value of members' axial stress in the topmost single-layer dome for objective function,Non-dominated Sorting Genetic Algorithmâ…¡(NSGA-â…¡) was used to make multi-objective optimization calculation for the prestress level of suspen-dome structure, considering the structural strength and deflection limits.The results revealed the rule that every objective function of the structure varied with the prestress level of every hoop cable,which provides the basis for decision-making in engineering design.In order to solve the prestress adjustment on defect state of the suspen-dome system,this paper proposed two kinds of analysis methods,modified tension method and displacement compensation method.Modified tension method is a precise prestress adjustment method based on force controlling,and the displacement compensation method is a prestress correction method based on deformation controlling.According to the measured prestress values of cables or the coordinate values of controlled nodes of structure with great prestress deviation in construction period or usage period,the results show that the two methods proposed in this paper can be applied to obtain modified prestress controlled values and they also can be used to adjust the prestress on defect state in structure orderly,simply and accurately and make structure meet the requirements of design and construction precision.The method presented in this paper is based on structure behavior analysis to adjust prestress on defect state of the suspen-dome system.First,carry out structural static,dynamic and stability sensitivity analysis considering the structural defect factors such as prestress deviation of cable and node location deflection,then determine the weight of structural defects according to the results of the sensitivity analysis,at last,use the genetic algorithm to adjust and optimize prestress on the defect state of structure in order to obtain the prestress adjusting scheme which will make the structural properties the optimal.The modified original length method proposed in this paper is aim to solve the problem of simulating cable sliding at joint with friction effect.First,allow the cable slid at joint ignoring the structural deformation compatibility.The original length of every cable section can be obtained after sliding balance based on equilibrium equation and the invariability of total original length of those continuous sliding cables.Then,solving the compatibility equation with updated original cable length to get the sliding results and complete one sliding calculation of cable sections.The research results show that the modified original length method can be used in the problem of simulating cable sliding at joint with friction effect,and the calculation is simple and convenient.In this paper,structural performance of sunflower-patterned suspen-dome were studied, taking into account the friction impact of sliding-cable during construction process,the static, dynamic and stability characteristic of structure were analyzed,and two new of joint were proposed.The results show that the friction between hoop cable and joint will cause tension redistribution in hoop and radial cable of structure,led to uneven force distribution of the same hoop cable,increase displacement of some joints and axial stress of some bars in the lattice shell, and static properties of the structure will be obviously affected,but the dynamic and stability characteristic almost will not.Finally,used a practical engineering as reference,a scale model of suspen-dome structure with span of 8m was made,including models of traditional joints and new joints.Structure model adopting both two types of joints was tested in shape forming processing,under full-span load and half-span load,and was excess stretched on hoop cable.The tests showed that the tension of each hoop cable and radial cable distributed unevenly under various working conditions,because of the friction between hoop cable and joints.Compared with the traditional joints,using new joints in structure could make the friction between hoop cable and joints reduce obviously,and friction loss on hoop cable at joints was small.Meantime the moditied original cable length method proposed in this paper was proved correct through the experiment.