Novel Cable-strut System Based On Sliding Continuous Cables And Its Analytical Theory

Cable-strut structures are composed of cables in tension and struts in compression.They are widely used in the field of structural engineering for their lightweight,high-strength,and flexible shapes.In existing applications of cable-strut structures,cables are sometimes designed as continuous components to carry continuous tension forces,and the connections between the nodes and continuous cables are always fixed in the operation stages.This research investigates a novel design concept for cable-strut structures,in which the continuous cables are allowed to slide through the nodes.The design concept provides the following benefits:(1)in terms of structural constructions,the procedure of clamping the cables on the nodes is omitted by allowing cable-node slidings;(2)in terms of structural static properties,the cable-node sliding can transform deformations between the adjacent segments of continuous cables,which reduces the peak forces under external loads;and(3)in terms of structural dynamic properties,the energy dissipation caused by frictional slidings between cables and nodes can increase the damping and thus improve the performance under dynamic loads.The design and analysis of cable-strut structures with sliding cables are different from that of conventional ones.Most of the existing studies focus on the analysis of structural responses with pre-determined nodal sliding states and load paths or use the frictionless assumption.The existing studies cannot satisfy the design requirements of real engineering structures under complex operating conditions.In this research,the form-finding method,the mechanical analysis method,and the construction control method of the proposed structure are systematically studied based on real engineering requirements.Furthermore,a Geiger-type cable dome with sliding ridge cable is proposed.The structural responses under static and dynamic loads are investigated by numerical simulations,and a model test is conducted to show its potential for real applications.First,a form-finding method for cable structures with sliding cables is proposed.The shape of the structure is determined based on given cable forces and strut lengths so that the force distribution satisfies the requirements of continuous cables.The total potential energy function of the structure is given,and the equilibrium conditions of the structure are derived based on the first-order derivative of the potential energy.An intermediate function is constructed based on the characteristics of the total energy function to solve the equilibrium equations.The effectiveness of the method is through numerical examples.Second,frameworks for the mechanical analysis of continuous cable systems are provided.The load-displacement relation for frictional sliding cable structures is derived,in which the sliding amount parameters used in existing methods are eliminated.The nodal displacements are expressed as formulations in terms of the external loads,the initial prestresses,and the relative force ratios of the segments that belong to continuous cables.The load-displacement relationship is then applied to the static and dynamic analysis.For a definite load path,the structural responses can be uniquely determined by successively trials and modifications of the nodal sliding state.For an indefinite load path,a formula of all the possible structural responses is derived,and the ranges of the structural responses can be obtained.Furthermore,the dynamic analysis procedures considering the influence of frictional energy dissipation are given based on the Newmark-β method.The accuracy and effectiveness of the computational frameworks are demonstrated by numerical examples and an experimental study.Third,a construction control approach for sliding cable structures considering measurement errors is proposed.The sensitivity matrix relating the member forces to the elongations of sliding cable systems is derived.The control objective of the structural internal forces considering friction is derived.The active and measured elements are selected based on the physical meaning of the singular values of the sensitivity matrix.A robust method based on sparse regression is proposed to determine the elongations of active elements,and a modified Orthogonal Matching Pursuit method is proposed to obtain the sparse solution.The effectiveness of the method is illustrated by numerical examples and experimental studies.It shows that the proposed approach can significantly decrease the pre-stress errors by adjusting a small number of active elements and is robust to noise.Finally,a modified Geiger-type cable dome form with sliding ridge cabled is proposed and investigated.Compared to conventional Geiger-type cable domes,the pre-stresses in the cables are more uniform,and there are only two different cable forces in the initial state.The ridge cables are all connected to the supported nodes so that the tensioning procedures are easier.The static and dynamic properties of the new structural form are investigated and compared with conventional structures.A numerical example is presented to illustrate the feasibility of the new cable dome,in which the static and dynamic properties of the new structural form are investigated and compared with conventional ones.The influences of the strut lengths and the ratio of the hoop cable force to the ridge cable force on the structural performances are studied.A physical model with a span of 10 m is designed and built,and the structural performances in tensioning procedures and under static/dynamic loads are tested to further verify the feasibility of the proposed structural system.