Analyzing the Form-Finding of a Large-Span Transversely Stiffened Suspended Cable System: A Method Considering Construction Processes

The precise control of the shape of transversely stiffened suspended cable systems is crucial. However, existing form-finding methods primarily rely on iterative calculations that treat loads as fixed known conditions. These methods are inefficient and fail to accurately control shape results. In this study, we propose a form-finding method that analyzes the load response of models under different sag and stress levels, taking into account the construction process. To analyze the system, a structural finite element model was established in ANSYS, and geometric nonlinear analysis was conducted using the Newton-Raphson method. The form-finding analysis results demonstrate that the proposed method achieves precise control of shape, with a maximum shape error ranging from 0.33% to 0.98%. Furthermore, the relationships between loads and tension forces are influenced by the deformed shape of the structures, exhibiting significant geometric nonlinear characteristics. Meanwhile, the load response analysis reveals that the stress level of the self-equilibrium state in the transversely stiffened suspended cable system is primarily governed by strength criteria, while shape is predominantly controlled by stiffness criteria. Importantly, by simulating the initial tensioning process as an initial condition, this method solves for a counterweight that satisfies the requirements and achieves a self-equilibrium state with the desired shape. The shape of the self-equilibrium state is precisely controlled by simulating the construction process. Overall, this work presents a new method for analyzing the form-finding process of large-span transversely stiffened suspended cable system, considering the construction process which was often overlooked in previous studies.

Structural design and model fabrication of cable-rib tensioned deployable parabolic cylindrical antenna

Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based on cable-rib tension structures is proposed and verified by a physical prototype. The parabolic cylindrical antenna adopts simple parallel four-bar mechanisms to construct the basic deployable unit, and the cylindrical direction dimension can be easily extended by modularization, which has obvious advantages in storage ratio and area density. Considering the complexity of the entire antenna structure design, including cable networks and flexible trusses, the form-finding design optimization model of a parabolic cylindrical antenna is established using the force density sensitivity method, and then the kinematics analysis of the deployable mechanism is carried out. Finally, a single-module prototype with a deployable diameter of 4 m × 2 m was designed and fabricated. The results of the ground deployment process test and surface accuracy measurements show that the antenna has good feasibility and practicability.

Form-fnding methods for deployable mesh reflector antennas

Deployable high-frequency mesh reflector antennas for future communications and obser- vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surface accuracy are widely required. The form-finding analysis of deployable mesh reflector antennas becomes more vital which aims to determine the initial surface profile formed by the equilibrium prestress distribution in cables to satisfy the surface accuracy requirement. In this paper, two form-finding methods for mesh reflector antennas, both of which include two steps, are pro- posed. The first step is to investigate the prestress design only for the cable net structure as the circum- ferential nodes connected to the supporting truss are assumed fixed. The second step is to optimize the prestress distribution of the boundary cables connected directly to the supporting truss considering the elastic deformation of the antenna structure. Some numerical examples are carried out and the simulation results demonstrate the proposed form-finding methods can warrant the deformed antenna reflector surface matches the one by design and the cable tension forces fall in a specified range.

Theoretical analysis and experimental study of an air inflated membrane structure

In this paper,an experimental study of an air inflated membrane was carried out based on the China National Stadium (the Bird's Nest). After the 2008 Olympic Games,it was apparent that the future use of the Bird's Nest would be enhanced if rainfall could be prevented from entering the stadium. The installation of an air inflated membrane across the opening of the steel structure was proposed as a solution to this problem. To verify the scheme,a theoretical analysis and experimental study of an air inflated membrane was carried out. Experimental and computational models were developed,form-finding was carried out using both experimental and theoretical methods,and the results from the two approaches,including the deflection of the air inflated membrane and deformation of the support structure,were analyzed and compared. The force-transfer path and deformation of the air inflated membrane under loads was studied. Conclusions and suggestions are presented.

The Gift from Nature： Bio-Inspired Strategy for Developing Innovative Bridges

Biology has been a brilliant teacher and a precious textbook to man-made construction for thousands of years, because it allows one to learn and be inspired by nature＇s remarkable and efficient structural systems. However, the emerging biomimetic studies have been of increasing interest for civil engineering design only in the past two decades. Bridge design is one of aspects on structural engineering of biomimeties that offers an enormous potential for inspiration in various aspects, such as the ge- ometry, structure, mechanism, energy use and the intelligence. Recently built bridges and design proposals in which biological systems have produced a range of inspiration are reviewed in this paper. Multidisciplinary cooperation is discussed for the implementation of bio-inspired methods in future design. A case study about using bio-inspired strategy is trying to present a problem-solving approach, yet further cooperation is still needed to utilize biomimetie studies for design inspiration. This paper aims to call a close multidisciplinary collaboration that promotes engineers to build more sustainable and smart structural systems for bridges in the 21 st century.