Narrow Results

This paper deals with the experimental results obtained by in situ and model testing of a segment of the pipeline system of a thermal power plant. The field testing has been performed by using the forced and ambient vibration method. The model testing has been performed by means of a shaking table. The model was designed and constructed to the scale of 1/3 and tested on the seismic shaking table in the IZIIS' laboratory. The adopted modeling concept was an adequate model with artificial mass simulation, using the same material as that of the prototype. The spring hangings, as well as the special rolling support, have also been simulated. The model was subjected to random, harmonic and earthquake motion in horizontal, vertical and biaxial directions. The results show that the support springs can accept displacements in both the horizontal and the vertical direction in the elastic range of deformation, while the stop point base support is sensitive to the intensity of earthquake motion and is required to be limited to the horizontal and vertical directions.

Owing to the slenderness and lightness of most modern footbridges, vibration serviceability assessment becomes a crucial issue in the design process. As one of the key factors, the vibration comfort criterion has an important influence on the assessment of the final result. However, there is an obvious lack of experimental studies in this field, especially regarding the pedestrians' perception of the induced vibrations. In this study, an experiment was conducted to investigate the pedestrians' perception of human-induced vibrations of footbridges. During the experiment, the subjects walked on a pathway that was mounted on top of a shaking table. By imposing sinusoidal excitations with different amplitudes and frequencies, the experiment aimed to determine the influence of the two factors on the walking people's perception. Based on the data collected, perception scales were proposed for both the vertical and lateral vibrations of the footbridge. The established scales comprise five levels that depend on the acceleration amplitude and the frequency. Finally, a comparison between the proposed scales, existing comfort criteria in the literature and international codes was carried out.

This paper presents an experimental program to investigate the effects of cross-sectional shape on the seismic performance of irregularly shaped reinforced concrete (RC) columns. Five groups of specimens that were one-quarter of typical columns of a prototype medium-rise building were tested to failure using shaking table. The loading procedure was successively increasing peak ground acceleration until the test structure collapsed. The specimens were designed with the same cross-section area but different flange width and flange thickness. The seismic response characteristics of all specimens such as drift capacity, energy absorption capacity and failure mechanisms of each specimen group are evaluated, compared and discussed in detail. Based on the current test data, design recommendation is provided to assist engineers in designing such irregularly shaped columns.

A series of shaking table tests were conducted on reinforced slopes to study the slope dynamic characteristics. The influence of concrete-canvas tilt degrees on the seismic response was studied. By considering the effects of different concrete-canvas tilt degrees, the seismic responses of the reinforced slopes were analyzed, along with the accelerations, crest settlements, and horizontal displacements. The failure patterns of different model slopes were compared using white coral sand marks placed at designated elevations to monitor the internal slide of the reinforced slopes. Several round markers were placed on the slope surface to compare the deformation before and after shaking with different amplitudes. The results indicated that with the increase in concrete-canvas tilt degrees, a better reinforcing effect was obtained, and 30^° reinforcement reached a threshold level, the slide-out point shifts from the crest of the slope to the middle of the reinforced model. The bottom 2/7th zone of the slope was relatively stable during the earthquake and the reinforcement was ineffective at the bottom of the slope. When both considered the influence of reinforcing effect and construction difficulty, 20^° is the suitable tilt degree in concrete-canvas reinforced slopes. The characteristics of increasing strength of the concrete canvas make it suitable for the application in slope protection.

In this research, large-scale shaking table model test was conducted to study dynamic behavior of anchorage landslide under earthquake. Failure form of landslide soil, acceleration response and stress mechanism of pressure type anchor were analyzed respectively. The results indicate that: cracks of soil occurred mainly in the bottom and top of landslide: at low loading amplitude, shearing crack in slope toe appeared firstly; at high loading amplitude, top soil in landslide was seriously destructed; at last, large area of block-form soil were shot to the table. After many times of stimulation, the first order natural frequency of this model declined slowly, then increased, and finally tended to stabilize. With the increase of loading amplitude, acceleration response increased more obviously, and had elevation amplification effect. For different anchors, at low and medium loading amplitude, stress of the top anchor and the bottom anchor were bigger than other anchors, while at high loading amplitude, the second anchor was also very large. For the same anchor, like static loading condition, measured point stress near bearing plate was the biggest. The results could provide a reasonable foundation for the design of the anchors under earthquake.