Advanced Materials Research Vols. 163-167

Abstract: Arch bridge as well as arch frame of building is òne kind of plane-curved-bar system of bearing pressure.When the load of arch carrying reaches some value, the arch will lost the balance stability. Based on the theory of precise transfer matrix method and differential equation of circular arch in plane, a new method for plane-buckling analysis of circular arch under uniform load is derived, by which the critical load of circular arch with two hinge supports is calculated. Compared with the theoretical solution, they anastomosed each other well, that shows the method is right and effective.

Abstract: The effect of “zero time holding” quenching temperature on the 45 steel’s microstructure and mechanical properties were studied by the orthogonal regressive principle. The 45 steel’s microstructure characteristics with “zero time holding” quenched were analyzed. The results showed that the 45 steel’s strength and hardness increased with the increase of quenching temperature in the range of 780～ 900°C. The grain size in zero time holding was smaller than that with holding time (60 min). The martensite lath was very fine after “zero time holding” quenched. The mechanical properties of the 45 steel Processed by the zero time holding heat treatment is higher than those processed by the conventional heat treatment. The experimental results showed that the properties of the drive shaft with 45 steel were satisfying after they are processed with the “zero time holding”heat treatment technology.

Abstract: Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

Abstract: The best is to read these instructions and follow the outline of this text. The physical and numerical models were combined to analyze flow-induced vibration response of Qingshuihe River underwater horizontal gate in this paper; the pressures acting on the gate were divided into two parts: the fluctuating pressure of flow on the stationary gate and the hydrodynamic pressure caused by the gate vibration, which is additional pressure induced by disturbed flow. The temporal-spatial correlation of fluctuating pressures obtained by model experiments between different nodes was analyzed. In the study the coherence function is defined in frequency domain with consideration of different levels of correlation for different frequency components, and the nodal load of the fluctuating pressure could be obtained. A new distribution of additional mass with considering radial vibration of the gate is adopted as equivalent hydrodynamic pressure. Based on random vibration theory, the flow-induced vibration response of the gate was obtained. The results provide the reliable reference evidence for structural dynamic design of the gate and show that the hydrodynamic stability of the gate can meet the requirement. On the other hand, it is shown that this method is reasonable and feasible.

Abstract: The question whether hidden weld of unstiffened overlapped CHS (circular hollow sections) KK-joints is welded or un-welded is not clearly mentioned in China's steel structure design codes (GB50017-2003) .This paper mainly analyzes the influence of chord-to-brace diameter ratio β, diameter-to- ply ratio γ and brace-to-chord ply ratio τ to the ultimate bearing capacity of the joints with the hidden weld welded and un-welded. The influence of welded and un-welded hidden welds of the joints on hysteretic behavior under low frequency loading is analyzed , and hysteretic curve of the joints are obtained by the finite element software ANSYS. Side brace or opposite brace of the hidden weld of the joints has little influence on the failure modes and ultimate capacity of the joints. Hysteretic behavior of the joints with the hidden weld un-welded is much better than that of the welded.

Abstract: In order to study temperature effect on initial curve of main cable, three different temperature models were built about temperature changes of main cable along span direction, and iteration calculation methods to find initial curve of main cable in variable temperature field was proposed based on the theory that the length of non-stress wire strand is persistence in unloaded cable station and construction completion station. The catenary equation in variable temperature field was deduced and the suspender length variation as well as horizontal component of cable forces were calculated based on the catenary equation. Taking some suspension bridge for an example, suspender length variation, horizontal component of the cable forces and node coordinate under three different temperature models were calculated by iteration calculation methods.

Abstract: In order to reasonably analyze interlayer separation of complex roof in deep coal tunnel, the rational calculation model was chosen and distribution of normal stress, shear stress and interlayer separation of construction surface in elastic and plastic conditions were analyzed in different original rock stress. In order to analyze varying interlayer separation with time, rational creep model was chosen and the results were drawn that plastic deformation of complex roof had obvious influence on interlayer separation and numerical simulation agreed well with the actual varying interlayer separation with time by burger creep viscoplasticity model to analyze creep characters of complex roof.

Abstract: The seismic performance of braced steel frame was simulated by the finite element software ANSYS based on the passive energy-dissipation under the low-cycle repeated load and the time-history analysis under seismic load for the energy-dissipation braced steel frame structure, no-brace steel frame structure, and conventional braced frame structure. The energy dissipation and seismic performance of three kinds of frame were compared, the results show that the energy-dissipation braced structure can produce strong energy-dissipation control force to enhance energy dissipation capacity of the whole structure significantly, and weaken the seismic load of the main frame. It follows that the energy-dissipation braced steel frame can achieve the purpose of energy dissipation for structure, and has good seismic performance.

Abstract: A finite element method is proposed to determine the chord side wall failure load of welded RHS T-joints with axial compression branch. The width ratios β (=b1/b0) vary from 0.8 to 0.9, and the range of wall slenderness is 16.1≤h0/t0≤42.3. With strain hardening of the material not take into account, the validity of the FEM model is verified using existing experimental results. The failure of the joints is mainly due to the buckling or crippling of the chord side wall, which agree well with the experiment. The mean failure load determined by FEM is about 93% of the test and with a coefficient of vibration of 0.037. The ultimate strength so determined is also compared with the existing design formulae. The proposed method is more reliable. Further investigations are required to develop design formulae for the side wall failure of RHS joints with width ratio β≠1.0.

Abstract: Finite element model of both the single-layer Schwedler reticulated dome with the span of 50m and a Cuboid impactor were developed, incorporating ANSYS/LS-DYNA. PLASTIC_KINEMATIC (MAT_003) material model which takes stain rate into account was used to simulate steel under impact load. The automatic point to surface contact (NODES TO SURFACE) was applied between the dome and impact block. Three stages of time history curve of the impact force on the apex of the single-layer Scheduler reticulated dome including the impact stage, stable stalemate stage, the decaying stage were generalized according to its dynamic response. It must be pointed out that the peak of the impact force of the single-layer reticulated dome increase with the increase of the weight and the velocity of the impact block, but the change of the velocity of the impact block is more sensitive than the change of weight of the impact block for the effect of the peak of the impact force, and a platform value of the impact force of the single-layer reticulated dome change near a certain value, and the duration time of the impact gradually increase. Then four stages of time history curve of the impact displacement were proposed according to the dynamic response of impact on the apex of the single-layer reticulated dome based on numerical analysis. Four stages include in elastic deformation stage, plastic deformation stage, elastic rebound stage, free vibration stage in the position of the residual deformation.