This paper investigates the characteristics of unstable behaviour and critical buckling load by joint rigidity of framed large spatial structures which are sensitive to initial conditions. To distinguish the stable from the unstable, a singular point on equilibrium path and a critical buckling level are computed by the eigenvalues and determinants of the tangential stiffness matrix. For the case study, a two-free node example and a folded plate typed long span example with 325 nodes are adopted, and these adopted examples' nonlinear analysis and unstable characteristics are analyzed. The numerical results in the case of the two-free node example indicate that as the influence of snap-through is bigger; that of bifurcation buckling is lower than that of the joint rigidity as the influence of snap-through is lower. Besides, when the rigidity decreases, the critical buckling load ratio increases. These results are similar to those of the folded-typed long span example. When the buckling load ratio is 0.6 or less, the rigidity greatly increases.
In order to improve the wind performance of buckling-restrained braces (BRBs), Hybrid buckling-restrained braces (H-BRBs) have been studied in Korea. The seismic performance of H-BRBs is different according to the action of VE damper. In this study, the nonlinear time history analyses have been performed on the parameters such as brace types and input earthquakes. The results of the study suggest that H-BRBs meet the BRB's requirement of ANSI/AISC 341-10 only if VE damper is not working during an earthquake.
The author has proposed and verified the accuracy through experiments on a method of measurement through the use of sound waves that not only can quantitatively measure each of the dual directions of the fiber axis with high accuracy of membrane tension created on the surface of the membrane structure, but also can be easily operated in the field of construction. This paper reports the solution for problems of variables caused in the process of downsizing of the measurement equipment in order for practical use, and verifies the correspondence possibility of various stress ratios.
When adjacent tall buildings experience earthquake excitation, structural pounding may happen. In order to mitigate seismic pounding damage to adjacent structures, many studies have been done to date. Tuned mass dampers (TMD) are widely used for reduction of dynamic responses of building structures subjected to earthquake excitations. If a TMD is shared between adjacent buildings and it shows good control performance, it will be effective and economic means to reduce seismic responses of adjacent structures. In this study, control performance of a shared tuned mass damper (STMD) for seismic response reduction of adjacent buildings has been evaluated. For this purpose, two 8-story example buildings were used and multi-objective genetic algorithms has been employed for optimal design of the stiffness and damping parameters of the STMD. Based on numerical analyses, it has been shown that a STMD can effectively control dynamic responses and reduce the effect of pounding between adjacent buildings subjected to earthquake excitations in comparison with a traditional TMD.
Most of the structural forms in which ETFE film is used are the cushion(pneumatic membrane structures) and tension type(tensile membrane structures), which have been generally accepted to be the most efficient forms. Tensile membrane structures are pulled outward from the exterior to introduce initial stress. And such structures offer the advantage of a natural shape formed by tensile stress and eliminate the need for blast air. Recently, the number of tension type structures is increasing. However, there are problems of creep and relaxation of ETFE films under long-term stresses. In this paper, the stretch fabrication method is proposed for stretching the film into the plastic region during initial tensioning as a way to increase its strength. And its effectiveness is confirmed by investigating experimental and analytical test using ETFE films.
Ethylene Tetrafluoroethylene (ETFE) has been widely used in long-span buildings because of its light weight and high transparency. This paper studies the short and long term creep behaviour of ETFE foil. A series of short-term creep and recovery tests were performed, in which the residual strain was observed. A long-term creep test of the ETFE foil was also performed over 110 days. A viscoelastic-plastic model was then established to describe the short-term creep and recovery behaviour. The model contains a traditional multi-Kelvin part and an added steady-flow component to represent the viscoelastic and viscoplastic behaviour, respectively. The model successfully fit the data for three stresses and six temperatures. Additionally, time-temperature equivalency was adopted to predict the long-term creep behaviour of ETFE foil. Horizontal shifting factors were determined from the process of shifting creep-curves at six temperatures. The long-term creep behaviours at three temperatures were predicted. Finally, the long-term creep test showed that the short-term creep test at identical temperatures insufficiently predicted additional creep behaviour, and the long-term test verified the horizontal shifting factors derived from the time-temperature equivalency.
Recently, natural disasters such as earthquake, tsunami, typhoon and tornado are increasing, and cause huge economical loses and victim. Thus, when the disaster occurs, it is important to prepare emergency evacuation shelters for fast and easy construction compared to general building system. And, deployable structures will provide a great help for such aim. Deployable structures have the great advantage of being faster and easier to erect and dismantle compared to conventional building forms. In this study, we confirm the possibility of deployment for shelter structures using scissor structure system. First, Basic model was performed to recognize the appllicability of the deployable systems of the dome-shaped structure. Second, Advanced model that more improved inner space and deployment mechanism was confirmed.