Advanced Materials Research Vols. 243-249

Abstract: In earthquake engineering, researchers have found that many structures were not damaged after strong ground motions because of the rocking effect. In order to reveal the potential application value of the uplift effect on seismic isolation, it will be using numerical simulation software OpenSees to research the seismic response of pier considering uplift. Building the pier’s finite element model and considering the plasticity and nonlinear of the pier and soil spring, the ground motion from El Centro and TCU101 are taken as the input respectively. Through analyzing the result, it is shown that at the base of the pier the maximum bending moment is reduced by 36.93% and 46.70%, and the maximum curvature is also reduced by 78.42% and 87.12% respectively. Meanwhile, the maximum horizontal acceleration at the top of the pier is decreased 12.60% and 16.90%. The uplift effect significantly reduces the plastic deformation and plays a base-isolated role according to the results. It has also found that the earthquakes with velocity pulse effect are dangerous to the structures.

Abstract: For the past few years, Push-over analytical method was regarded as a new evaluation method for seismic resistance capacity of structure in some advanced countries. More available information can be obtained from Push-over analysis than from elastic static, even elastic dynamic analysis and the method is easy to be operated. The elastic spectrum from the Highway Engineering Seismic Design Code (JTJ 004-89) was improved in order to take the inelastic effect into account. The inelastic demand spectra were derived by means of Vidic's strength reduction factors. By comparing capacity curves of bridge structure with the demand elastic spectrum, the earthquake resistance of bridge structure can be estimated. Furthermore, it is applied to evaluate seismic resistance capacity of a real bridge example in this paper. The results show that Pushover method can replace inelastic dynamic history analysis method in some cases.

Abstract: The settlement of railway subgrade has an important connection with the quality, safety and natural life of the railway, the excessive settlement of subgrade will directly cause too many problems in the process of railway using. Especially in high speed railway, these problems will be more outstanding, thus affecting the development and progress of the railway. For the foundation of traffic infrastructure in areas with soft subsoil often embankments supported by piles are necessary due to the settlement requirements. For sufficient load transfer into the piles different construction methods are possible. For the construction of a high speed railway, a cement stabilization of the embankment material and geogrid reinforcement on top of the piles were used. Before the temporary load the settlement is monitored continuously for 10 months. In this paper, the method of construction is described and important field monitoring results are presented.

Abstract: Federal aviation administration rigid and flexible iterative elastic layered design (FAARFIELD) software program became the exclusive approved method for airport pavement thickness design adopted by federal aviation administration (FAA) in the United States after the advisory circular AC150/5320-6E “Airport Pavement Design and Evaluation” was issued in September 2009. In this paper, a sensitivity analysis was conducted to investigate the effect of FAARFIELD input parameters on the required thickness of the airport rigid pavement. The input parameters studied are: concrete flexural strength (modulus of rupture, MOR), the subgrade reaction modulus, K, subbase layers and air traffic mix .Each evaluated input parameter was varied within its recommended range to study its effect on the required thickness of the airport pavement. It was found that the concrete modulus of rupture is the most sensitive parameter on the required thickness.

Abstract: A 3D finite element model is used to investigate the state of load stress developed in concrete pavement with dowel bar under the effect of typical pavement damages of pumping area of slab corner and pumping area of transverse joints edge. The results indicate that slab corner stress tends to decrease with the increase of slab thickness and possesses a nonlinear growth as pumping area increases; when the pumping area of slab corner is less than 1.5m×1.5m, the maximum pavement slab tensile stress is less than or close to the load stress in critical loading position. Stress in transverse joints edge also grows in a nonlinear tendency and axle load also grows gradually with the expansion of pumping area, of which the slope of the curve in the relationship between stress and void size is much greater. Whether it is a pumping area of slab corner or pumping area of transverse joints edge, pavement slab deformation and stress are significantly reduced after setting the dowel bar. Therefore, dowel bar can improve the stress state of concrete pavement obviously.

Abstract: Ball penetration test is used to measure the penetration depth of steel ball on the original asphalt pavement which is under impact load. The penetration depth is to evaluate the flexibility of the original pavement and one of mix proportion design parameters of chip seal. The test result is the plastic deformation of asphalt pavement under impact load. In this paper, layered half-space elastic-plastic model of the asphalt pavement is set up by transient dynamic analysis which is in structural analysis, the progress of the steel ball impacting pavement is numerical simulated, and the plastic deformation of asphalt pavement under impact load is studied. Results indicated that the using material parameters are mainly reasonable and the theoretical calculation result satisfies the requests of the engineering application. The method and results can be used in the theoretical analysis of chip seal mix proportion design.

Abstract: The present study is to evaluate micro-density of timber materials on cell level. Density, one of the most important parameters for such materials, is discussed in details. Four kinds of timbers are placed under a microscope for cell photos from which the cavity ratios are obtained through an appropriate image processing computer code. Micro density is calculated by dividing bulk density by cell wall ratio. It is found that three out of four kinds of timbers have similar micro-density and therefore, for those samples, macro-density can be expressed as the multiplication of the cell wall ratio and micro-density which is treated as one of their characteristic constants, no matter it is late wood or early wood. In the future, micro-density can be one of the criteria to categorize structural timbers.

Abstract: This study utilized mechanical calculation method and finite element method ABAQUS software to analyze the mechanical response of different flexible pavement material combinations on steel deck. Heavy vehicle load with high axle load and high tire pressure were considered, so as to know the reasons for steel deck pavement distress, and to define the arrangement principle for steel deck pavement and the combination of materials suitable for flexible pavement. The results show that the fatigue damage of steel deck pavement coincides with traditional theory, the maximum tensile strain at the bottom of surface course is still the determination index, and the fatigue crack is presented mainly in four types; the maximum compressive strain on the top of steel plate is the determination index of rutting damage, the major cause for rut is the surface course under compressive strain in the wheel load position. The suitable material for steel deck one-course pavement is full depth Guss asphalt mix; the suitable combination for steel deck two-course pavement is modified asphalt mix on top and Guss asphalt mix at bottom.

Abstract: A comprehensive study of fractal property applied in earthquakes is analyzed based on the aftershock of 2008 Wenchuan earthquake. Different fractal parameters are analyzed to study the magnitude, epicenter and hypocenter structural distributions in time or space. The b-value is found to be 0.86 closed to which is usually 1.0 observed worldwide. This indicates there is a relative abundance of small magnitude events than large ones in the studied range. The spatial correlation is calculated using correlation integral technique, indicating that epicenters are approaching a two-dimensional region and the aftershocks are uniformly distributed along the trend of the aftershock zone. The rate of the fall of aftershock activity with time reflects the decrease of stress is modestly slow. Temporal correlation is 0.59 for aftershocks of M >4.0, indicating a non continuous aftershock activity. Geometrical probability dimension reflecting epicenter clustering degrees of the region was also analyzed. Also the volume fractal dimension of the aftershock region has been calculated using the box-counting technique to study the hypocenter distributions. From the assessment of slip on different faults it is inferred that 67.9% displacement is accommodated on the primary fault and the remainder on secondary faults.

Abstract: According to the tests and researches, this paper combine the constructing condition of scoria (volcanic ash) subgrade and lime-volcanic ash gradation macadam subgrade and the result of investigation and detection after the test section is completed, the physicochemical property, engineering property, compaction mechanism and performance, formation mechanism and increasing rule of strength of scoria (volcanic ash) and lime-volcanic ash are systematically analyzed, propose the construction technology and detection method of scoria (volcanic ash) subgrade and lime-volcanic ash gradation macadam subgrade, provide technical support and theoretical basis for application of scoria (volcanic ash) on road construction.