Shen Shi-zhao

DYNAMIC BEHAVIOR OF SINGLE-LAYER LATTICED CYLINDRICAL SHELLS SUBJECTED TO SEISMIC LOADING

The single-layer latticed cylindrical shell is one of the most widely adopted space-framed structures. In this paper, free vibration properties and dynamic response to horizontal and vertical seismic waves of single-layer latticed cylindrical shells are analyzed by the finite element method using ANSYS software. In the numerical study, where hundreds of cases were analyzed, the parameters considered included rise-span ratio, length-span ratio, surface load and member section size. Moreover, to better define the actual behavior of single-layer latticed shells, the study is focused on the dynamic stress response to both axial forces and bending moments. Based on the numerical results, the effects of the parameters considered on the stresses are discussed and a modified seismic force coefficient method is suggested. In addition, some advice based on these research results is presented to help in the future design of such structures.

A New Method for Wind-Induced Response Analysis of Long Span Roofs

Long span roofs are usually characterised by their dense distribution of natural frequencies and remarkable coupling effects among different natural modes. Those traditional methods, such as modal superposition method, are not suitable for analyzing wind-induced response of these structures. In this paper, a new method named as Ritz-POD method is proposed to analyse wind-induced response of long span roofs in frequency domain, which synthesises proper orthogonal decomposition (POD) technique and direct superposition method with Ritz vectors. The eigenvectors of fluctuating wind load with POD technique are regarded as spatial distributions of this load to generate Ritz vectors, and wind-induced response is analysed by direct superposition method with Ritz vectors. Therefore, it can take into account multimode buffeting response automatically, even the case that structures vibrate in high order modes. According to this method, the wind-induced response of a single layer reticular shell is analysed, and compared to the results achieved with modal superposition method. It shows that Ritz-POD method is more accurate and efficient with fewer Ritz vectors.

A study on dynamic stability of elastic structures by degree of stability of equilibrium

Publisher Summary The chapter describes dynamic stability criteria to establish a rigorous basis for that criteria by relating it to Liapunovs theory of stability of motion and to apply the criteria to analyze the stability of structures. For the structures, such as reticulated space structures, that possess multi-equilibrium states below the bucking load, static stability alone provides no assurance of a safe design; the structures can be forced from one equilibrium state to another by sufficiently large disturbances including earthquake action. The dynamic stability of a well-known structural model under harmonic disturbance as well as seismic disturbance is analyzed by the criteria in the chapter. Hence, the stability of equilibrium can only be decided related to the disturbances that can arise during the life of structures, and therefore, the dynamic stability analysis of these kinds of structures is needed.