Advanced Materials Research Vols. 250-253

Abstract: Pre-stressed spatial tubular truss system is adopted in steel roof truss structures of China International Exhibition Center New Venue. Bottom chord joints are multiplanar KK-joints consisting of chord with square hollow section and brace with circular hollow section. However, not only that relatively little research has been carried out on such joints, but also that no detailed design guidance on KK-type joints consisting of chord with square hollow section and brace with circular hollow section can be found Current design code for steel structure (GB 50017-2003). This paper reports the study into the strength of this type of KK-joints under axial loading. The numerical models were adopted, and several various geometric parameters which affect the strength and failure modes, were investigated. It was indicated that the geometric parameters affects significantly the ultimate capacity and failure modes of the joints. The varied relationship of the strength and failure mode with parameter varying was studied in detail. The results of the work presented provide initial discussion on behavior of this type of KK-joints and lay the foundation for a future large-scale parametric study and put out design formula.

Abstract: Based on the general FEA program, the bidirectional nonlinear behavior of lead rubber bearing is taken into account by using two orthogonal nonlinear spring elements. Considering the effect of radius of curvature, lead diameter and dissimilar seismic motions, dimensional FEA model of seismically isolated curved continuous bridge is established. And the seismic energy response analyses for seismically isolated curved continuous bridge are carried out under the three-dimensional seismic motions. So, some meaningful references are provided for the design of vibration absorption and isolation of the curved beam bridge in this paper.

Abstract: By the traditional calculation method of evaluating the stability of the karst foundation, the results often exist certain differences from actual engineering situation. Based on the hydrodynamics theories and the engineering case, a model of karst groundwater flow is established, the groundwater hydrodynamic force and the ability of carrying particles in sandy foundation of karst areas are calculated, and the karst foundation stability is evaluated in this paper.

Abstract: The main object of study is the natural loess. The confined compression test and confined compression resilience test of nature loess and remolded loess under nature water content condition was done separately by using unsaturated high pressure consolidation apparatus. Through comparisons of test data, we investigated the effects of overconsolidated and structural factors on the loess compressibility under specific moisture conditions and analyzed the natural laws of compressive deformation properties of loess.

Abstract: The expanding properties of limestone from 200°C to 700°C were investigated under high temperature and bidirectional restraints with the device used to heating rock designed by ourselves. The experimental results show that the two directional expanding stress of limestone increased with temperature increasing during raising temperature before 600°C, and decreased after 600°C. The expanding stress perpendicular to bedding plane was bigger than that parallel to bedding plane. The curves of expanding stress and temperature ascend steadily during constant temperature before 600°C, but the slopes were much less than those during raising temperature. The expanding stress tended to steady value at last with the time of constant temperature prolonging. The expanding stress when constant temperature ended was smaller than those before constant temperature at 700°C. It showed that the limestone had expanded to the limit value after a certain temperature. The expanding stress reduced possibly after a certain temperature because the rock sample was restricted and some fissures closed and the number of cracks reduced after over-high temperature, but the detailed cause needs more researches to testify it.

Abstract: The measurement data indicates that the main reason for tunnel damage is continuing level displacement with the characteristic of Pie Form. The experiment shows that, compared with uniaxial compressing, the residual stress in triaxiality compressing is greater, this can result that the level support can increase the stress of the surrounding rocks and decrease or stop the level displacement, at same time, control the pie form displacement of the coal. Based on the situation of tunnel displacement, semi-closing support with I bar or support structure with anchor cable are designed, which can control the continuing displacement of tunnel effectively.

Abstract: In order to discuss the relationship between truss string structure weight and the rise, so as to find out the optimal rise of different spans, Fibonacci search method is used to write truss string structure optimization program which takes the rise as variable. To effectively improve search efficiency and ensure the accuracy, the dynamic search interval is introduced when writing the Fibonacci search program. This paper use Fibonacci to search the optimal rise in span of 100m of truss string structure, meanwhile analysis the dynamic search interval, the analysis results show that the approximate solutions of this method is very approximate to exact solutions, and search efficiency is improved.

Abstract: Juancheng Yellow River Highway Bridge is the largest externally pre-stressed concrete continuous box-girder bridge with corrugated steel webs in the world with the total length of 1460m and span arrangement of 70m+11×120m+70m. Based on the monitoring practice for this bridge construction, the paper illustrates the application of the two modeling methods for box-girder with corrugated steel webs in the calculation of alignment control using bridge analysis system GQJS, i.e. the one-node method and two-node method. Additionally, the comparison between the measured and predicted deformation under different construction stages including cantilever construction, closure construction, system transformation and external prestress tension is presented and discussed. The results turn out both the two proposed modeling methods can perfectly meet the requirements of alignment control of this kind of bridge.

Abstract: This paper discusses the stope parameters of the sublevel subsequent filling stage in Daye Iron Shizishan section. According to the similar material simulation technology, which is the main means, displacement monitoring and internal stress monitoring, several conclusions are summarized as bellow: When the parameter of the room and pillar is 18m, the underground mining is safe and steady. Impacts, which come from different regions’ mining, is different, and the greatest impact comes from the pillar’ mining. Stress monitoring shows that before roof fell down, there is a process of stress concentration. The stress in the roof is shear stress, and compressive stress in the pillar.

Abstract: Assuming the internal friction angle of backfill and the displacement are in nonlinear, to adopt the calculation model that was put forward by the author, combined with the in-room model experiment, to calculate and analyze the passive earth pressure acted on the retaining wall in the model of RBT movement. The analysis results show: the calculated values and the test values can agree with each other very well in the three ways of the distribution of earth pressure along the wall height, the values of the passive total force and its action point position. So it is feasible to use the calculation model to calculate the passive earth pressure in the model of RBT movement. Comparatively, when n = 0 the calculated values are the most identical with the test values, when n = 0.25 are worse, when n = 0.5 are the worst. Those may be relative to the sizes effect of the box of model test and the property of the interface between the soil and the plate at the bottom of model box. In addition, with the value of n increasing gradually, the maximum displacement needed to reach Rankine’s passive limit state will be decreased.