Advanced Materials Research Vols. 163-167

Abstract: In view of masonry structures with rigid floor slab, seismic behavior of R. C. stairs and influence of stairs on the stiffness of lateral walls of stair well was analyzed, calculation formulae of the seismic internal forces of stairs were deduced, calculation method of the seismic shear forces considering the seismic effect of stairs on main structure were given out. Analysis and comparison on engineering ensamples were carried out. The results show K-type bracing function of step slabs to main structure is evident. Considering the bracing function, shear deformation of the floor layer and shear forces in the seismic walls are decreased, internal forces in R. C. stairs are increased. Seismic design recommendation of step slab to decrease the seismic forces was presented.

Abstract: As separated platform subway station structures are close to the bridge piles, its seismic performance need to be analyzed. An artificial earthquake record is used to analyze seismic performance of the subway station structure. The artificial earthquake record with the Kanai–Tajimi model and trigonometric series superprosition method is generated. It is shown that the influences of the stresses of arch springing and basement are significant under horizontal direction earthquake. Under horizontal direction earthquake, the horizontal stresses of arch springing and basement are 1.46 and 1.61 times than the original stresses and their vertical stresses are 1.34 and 1.59 times than the original stresses. It is shown that the influences of the horizontal stress of soleplate and the vertical stresses of arch springing and basement are significant under vertical direction earthquake. Under vertical direction earthquake, the horizontal stresse of soleplate is 3.30 times than the original stress, while vertical stresses of arch springing and basement are 2.78 and 2.72 times than the original stresses.

Abstract: Wind pressure fluctuations acting on space structures are important for prediction of peak pressure values and for fatigue design purpose. Collection of several time histories of pressure fluctuations by traditional wind tunnel measurements is time consuming and expensive. Thus, a study on developing new wind pressure simulation technique on domed structures is carried out. An efficient, flexible and easily applied stochastic non-Gaussian simulation algorithm is presented using a cumulative distribution function (CDF) mapping technique that converges to a desired target power spectral density. This method first generates Gaussian sample fields using wavelet bases and then maps them into non-Gaussian sample fields with the aid of an iterative procedure. Results from this technique are presented and compared with those from the wind tunnel experiments. The advantages and limitations of this method are also discussed.

Abstract: Characteristics of wind pressure distributions over the spherical shell with 3/4 rise-span ratio have been investigated based on the data obtained from a wind tunnel experiment. A discussion of the spectral characteristics including shape of wind pressure spectra, reduced frequency corresponding to the peak spectral amplitude, and spectral slope in high frequency range is also made. The results show that the normalized pressure spectra has a broadband peak at a reduced frequency between 0.15 and 0.50, the slope of Sp( f ) in a high frequency range varies from -1.85 to -0.30 and the reduced peak frequency depends on the tapping locations. Though spectral patterns change from place to place, standard normalized spectra associated with various zones of spherical shell could be appropriately classified based on identical spectral characteristics. On this basis, an empirical spectral equation is figured out including three parts which represent the contribution of approach turbulence, turbulence induced by separation on the top of spherical shell and wake turbulence respectively. The accuracy of model is verified by comparison with the measured spectra results.

Abstract: Based on the shaking table model test of a bent-type aqueduct on the rigidity foundation, the dynamic characteristics and seismic performance of the aqueduct structure subjected to vertical seismic waves are discussed. The test indicates that (1) Water in the aqueduct makes the mass of the structure larger and the frequency of the model structure lower. The water in aqueduct makes fundamental frequency of the model reduce 32% and the modal damping increase 38.5% averagely. (2)The hydrodynamic pressure response at the bottom of the aqueduct is the highest. (3)The dynamic effect of El waves on the aqueduct structure is greater than that of all SEW waves. (4) Different types of earthquake waves have different frequency spectrum characteristics, so that the aqueduct model responses differently to different waves. (5) The water in the aqueduct sometimes plays a role as TLD damping in certain scope. If surpassing this scope, the water sloshing makes the vertical acceleration response of the aqueduct increase. The results of the test not only lead to some significant conclusions for the earthquake-resistant design of large bent-type aqueducts, but also provide a ground for further studies on the effects of soil-pile-aqueduct interaction.

Abstract: Based on the shortcomings of the continuous girder bridge with single column pier, two-span T-shape rigid-frame bridges with single integral pier and two separated piers are put forward in this paper. Using time-history analysis and considering the material nonlinearity of reinforced concrete of the pier, the nonlinear seismic responses of the three bridge structures subjected to horizontal seismic wave are analyzed. The results show that, compared with continuous girder bridge, the shear forces of the two types of T-shape rigid-frame bridge are bigger, the moments of the T-shape rigid-frame bridges is smaller, and rotation angle of plastic hinge of T-shape rigid-frame bridge is much smaller. The energy dissipation and the anti-seismic capacities of T-shape rigid-frame bridges are better than continuous girder bridge under the condition that the shear resistance capacity of pier is secure.

Abstract: The pounding between adjacent segments of bridge has significant influences on its seismic performance, which is a complex nonlinear phenomenon involving many parameters. Based on Kelvin impact model, a simple-supported girder bridge was introduced to discuss the effects of impact stiffness and initial gap between joints. With dynamic analysis, it can be drawn the reasonable range for impact stiffness ratio and initial gap at expansion joint are respectively 0.05~0.2 and 0.04m~0.05m, which make the earthquake response of bridge reach a good balance.

Abstract: A number of methods for assessing wind-induced vibration of structures are available ranging from simplified procedure using quasi-static methods to the detailed procedure using statistical methods. The appropriate procedure should be selected in accordance with wind sensitivity of structures. However, it still remains unresolved concerning how to provide a universal criterion with physically meaningful and convenient for the concept of the wind sensitivity until now. In order to solve the previous problem of how to distinguish between those structures for which the wind effects can be treated by simplified procedure, and those for which the wind effects must be treated by detailed procedure, a concept of sensitivity for wind-resistance is presented in this paper. The essential idea of this theory is to provide a general expression of wind sensitivity of structures by synthesizing three factors between wind load and the structure, including the size-effect factor, frequency-effect factor and mode-effect factor, which are based on the analytical derivation and take duly into account the influence of all the significant parameters for the response. Based on that, two case studies of cantilevered roof and single-layer reticulated shell structures under wind actions are demonstrated as illustrative examples.

Abstract: The paper proposes an aseismic hybrid control system to control the response of structures subjected to large ground motions caused by large magnitude earthquakes. The proposed hybrid control system consists of a base isolation system (laminated rubber bearings) connected to an active control system (a tuned mass damper and an actuator). The base isolation system is used to decouple the horizontal ground motions from the structure, whereas the active control system is used to protect the safety and integrity of the base isolation system. A 5-story benchmark building model is developed to study the effectiveness of the hybrid control system against different ground motions. It was found from the numerical results that rubber bearing system alone shows good performance and resists ground motion due to Hachinohe 1968, Kobe 1995, and Northridge 1994 earthquakes, but is somewhat unable to protect the model against El-Centro 1940 earthquake. After the installation of an active control system onto the rubber-isolated model, further improvements to earthquake resistance against these four earthquakes were observed, especially against the El-Centro earthquake. The merit of the hybrid control system lies in its capability to protect against different ground motions, with varying intensity and frequency content.

Abstract: A new damping wall system is proposed to improve the seismic performance of high-rise coupling shear walls. The coupling beams of the proposed wall are slit in the middle with damping devices (steel dampers) installed in the slit vertically aiming to dissipate energy during earthquakes and prevent severe damage of the structure. A FEM program named OpenSees is used to analyze the seismic performance of the new damping wall utilizing macro finite element model. During the analysis, influence of damper parameters and other factors on seismic performance of the damping wall is considered, and the analysis indicates that with proper damper parameters, the new damping wall can be provided with better seismic performance compared with the conventional wall.