Aerostatic stability analysis of long span half-through arch bridges

The main arch of a long-span arch bridge is a compression member. The static wind loads on the bridge not only causes changes of dynamic characters, but also leads the structure to collapse or buckling. Especially, when the arch bridge has longer span and less lateral braces,its stability is much different from the long span cable-stayed bridges and suspension bridges. This paper takes Chongqing Caiyuanba Yangzi River Bridge as a typical example and conducted the wind section tunnel tests. The displacement response of the bridge is obtained and its yield and static stability mechanism under static wind is analyzed. The results show that those factors, such as initial attack angle of the static wind, material yield strength and the static forces coefficients, have great effects on the aerostatics stability of a long span half-through arch bridge.     

Arch Axis Optimization of New Type Arch Bridge with Diagonal Web Cables Based on Geometric Nonlinear Mechanical Analysis

There are obvious geometric nonlinear mechanical characteristics in new type arch bridge with diagonal web cables. Meanwhile, the convergence of the existing arch axis iterative optimization method is not good. In order to solve new type arch bridge axis iteration convergence problem considering geometric nonlinear mechanical analysis, an arch axis iteration optimization method was proposed based on the iteration basis finite element model with two hinge arch model in main arch ring. A 600m span arch bridge with diagonal web cables was selected as an example to test the convergence performance and applicability of proposed method. The results showed that the bending moment of proposed method had better distribution along arch span, and it is about 35% smaller in maximum bending moment, 17% smaller in minimum bending moment and 23% smaller in bending strain energy compared to the results of linear iteration optimization method. Convergence analysis results demonstrated that proposed method had better iteration performance than the existing method. Meanwhile, different initial arch axis can converge to stable results.     

Wind Tunnel Tests of Long Span Half - through Arch Bridge Section Model

Wind induced vibration is one of the main control factors in the Long span bridge structure design. The wind tunnel tests for measuring the static wind forces on the bridge girder and the section model wind tunnel dynamic testing for Caiyuanba Yangtze River Bridge in Chongqing are introduced in this paper. The wind tunnel testing for measuring static wind forces and vortex- induced vibration test on the arch are introduced taking account of the influence between two arches. The main contents and outcomes of testing are presented. It is indicated that the bridge girder has excellent wind stability and the arch mechanical characters are rather complicated. The drag force on the hind arch varied a lot because of the font arch interference on the wind flow. The drag force on the hind arch will be negative when two arches are close to each other. It increases with the space of two arches. The results of testing will give the data of buffeting and vortex - induced vibration and flutter analysis of the bridge.     

Analysis on dynamic performance of hydrostaticoil film bearing throttled by capillary

With the linearization of the flow in oil chambers, the continuity equation of flow and the dynamic equation of the shaft are built for the hydrostatic journal bearing and thrust bearing respectively. Next, the transfer functions of the two bearings with capillary throttle are deduced. Then, the performance of the two bearings is simulated in Matlab. In general, the simulation results are well matched to the experimental data provided by Guangzhou Machine Tool Research Institute. It indicates that both of the models can predict the dynamic characteristic of the two bearings. Finally, the dynamics response of the hydrostatic thrust bearing is studied in various rotational speed of the shaft. Also, the dynamic performances of journal bearing are simulated in changing of inlet pressure and thickness of oil film.     

Nonlinear Seismic Response Analysis of Long- span CFST Arch Bridge

The non-linear seismic response behavior of concrete filled in steel tube(CFST) arch bridge subjected to synchronous seismic excition and multi-support seismic excitation is studied in this paper.The non-linear seismic response of CFST arch bridge is calculated by time-history analysis method,and the effect of geometric nonlinear to long-span CFST arch bridge is studied.The influence of internal-force and deformence under dead-load,multi-support seismic excitation,etc to nonlinear seismic response behavior of CFST arch bridge is analysed.The result show that the effect of geometric nonlinear to long-span CFST arch bridge is obvious.     

Spatial Interpretation of the Wooden Arch Gallery Bridges in Northeast Fujian from the Perspective of Behavior Space

On the basis of investigating wooden arch gallery bridges in China,perspectives of researchers studying wooden arch gallery bridges in northeast Fujian Province were reviewed,and the innovativeness of researches from the perspectives of cultural geography and significance of wooden arch gallery bridge for the locals’behaviors was proposed.Youxi Village in Qinyang Town,Shouning County,known as the Village of Gallery Bridge,was taken for example to analyze physical,spiritual and social properties of its wooden arch gallery bridge spaces.Wooden arch gallery bridge is an effective boundary point of settlement space,constituting natural ecological spaces and man-made physical spaces of rural settlements.And as a type of building space,wooden arch gallery bridge expands settlement spaces,contributes to settlement cultures,and enriches spiritual connotations of regional cultures.In northeast Fujian,wooden arch gallery bridge is an important social space for the locals’daily life by carrying on living,production and spiritual functions.     

Research on Seismic Behavior of Top-bear Arch Bridge with Viscoelastic Damping Braces

This paper proposes a new method of structure control that to set damping braces in a top - bear arch bridge. Lumped damping can be introduced to structures to reduce seismic response. The FEM analysis of Nimu bridge which is braced with viscoelastic dampers had done. The results show that the viscoelastic damping braces can remarkably decrease displacement within the arc plane, which is an efficient structure control method.     

Optimization Algorithm Research on the Arch Axis of Steel Box-Concrete Composite Arch Bridge

The paper proposed an innovative optimized design philosophy of the optimal arch axis of steel box-concrete arch bridge. Formulas to calculate the arch axis at the arch crown and the arch springing of this type of arch bridge were respectively derived wit     

Externally Pressurized Gas Journal Bearings in Power MEMS of Quasi Gas Power Cycle

An original thermodynamic idea for Power MEMS, which is called as quasi gas power cycle, is proposed to further intensify energy density and simplify structure of Power MEMS. Because gas supply with preset high pressure is set up in the Power MEMS engine of quasi gas power cycle, it is convenient for the Power MEMS engine to employ externally pressurized gas bearings to improve the performance of its bearings. Therefore mal design philosophy and structural type of the hyrostatic journal bearing as well as the hyrostatic thrust bearing in the Power MEMS engine are investigated, considering the limiting factor on meso scale. Then the structural and operational parameters are analyzed, and the optimal designs of typical externally pressurized gas bearings are put forward. Moreover the feasibility of the externally pressurized gas bearings applied to the Power MEMS engine is further verified by the calculation of load-carrying capacity of the hyrostatic gas bearings.     

Fuzzy Assessment Method for Seismic Damage of CFST Arch Bridges

In order to investigate the conditions of damage and failure of concrete-filled steel tube(CFST) arch bridges, considering the structural and mechanical characteristics of CFST arch bridges, the dual damage criteria assessment models of the various components based on deformation or strength and energy were developed. The nonlinear seismic response of CFST arch bridges was analyzed by finite element method and the fuzzy evaluation method of seismic damage based on fuzzy theory and analytic hierarchy process was studied. Finally, taking a long-span CFST arch bridge as example, the damage index of the bridge was 0.150, 0.152, 0.172 and 0.318 respectively when the seismic peak acceleration was respectively 0.1g, 0.2g, 0.4g and 0.8g. The results show that the CFST arch bridge is slightly damaged under the earthquake when the seismic peak acceleration is 0.4g, and the bridge is damaged moderately when the peak acceleration is 0.8g.     

Finite Element Analysis of the Contact Stress of the Rotary Hinge in the Rigid Frame Arch Bridge Constructed in a Vertically Downward Rotating Manner

Rotary hinges are temporary joints connecting arch ribs with the abutments of rigid frame arch bridges during the vertically downward rotating construction process.We probed the mechanical properties of a rotary hinge.Its stress distribution was simulated in contact FEM during the vertically downward rotating construction of a rigid frame arch bridge.The results show that nearly the entire structure of the rotary hinge is in a low-stress state with only a minor area in a high-stress state.By strengthening some local structures,rotary hinge construction security could be satisfied by its mechanical properties during vertically downward rotating construction.     

Seismic response of long span arch bridge under spatially variable seismic exicitation

Based on a spatial nonstationary model of seismic ground motion, the seismic acceleration time history are simulated by the wave superposition method. And then taking CaiYuanBa arch bridge in Chongqing as original model , this paper utilizes time history analysis method to analyze the seismic response characteristic of this type of long span arch bridge by support consistent or multi support seismic excitation .The numerical results indicate that the spatial variation of seismic ground motion have significant effect on the response of the arch bridge. Thrust of arch rib and vertical displacement, internal force of arch crown are increased greatly, but most internal forces of stiffener support are reduced.     

Time Effect Experimental Analysis of the Soil Arch Effect of Anti sliding Pile

Soil arching effect is important for stabilizing the soil behind anti sliding pile. The creep of soil mass will inevitably lead to the formation of soil arching, which has time effect. In this analysis, an indoor thrust pile model test is proposed. The characteristics of stress distribution in the soil and the time effect of soil arching behind anti sliding pile are analyzed. The experimental data acquired by the soil pressure cells arranged along the normal direction of the thrust show that soil arching effect is enhanced with the increase of thrust.The thickness of soil arch increases with time.And the data obtained by soil pressure cells arranged along the direction of the thrust show that the horizontal soil arching effect increases and then gradually extends.The scope of stress dispersion has very large growth along the normal direction as time goes on.     

Wind Tunnel Test for Section Model of Caiyuanbai Bridge Over Yangtse River

With the development of modern construction technique and the application of new material,arch bridges which progress towards small rigidity,long span and light weight,what's more is that long span bridge's rigidity under construction is much less than that in use stage.So it is very necessary to study the aerodynamic characteristics of long span bridge.The regularity of the three dimensional static component forces coefficient varying with attack angle and the girder's flutter properties of Caiyuanbai Bridge over Yangtse River are investigated with segmental molding's static wind-tunnel test and segmental molding's dynamic wind-tunnel test.Eight derivatives of the girder are also identified from the segmental molding's dynamic wind-tunnel test.Finally the assessment to wind resistant properties of the bridge is given based on detailed analysis of the test results.The conclusion which gets from analysis can provide an suggestion to design and construction this kind bridge.     

Effective Unloading Area between Cantilever Piles

The formation mechanism of the arching effect between cantilever piles is studied according to their stress characteristics. The soil arch is classified into three types based on its position in a space coordinate system, namely, a horizontal arch, a vertical arch and a free face arch. The master factor for distribution of unloading area between piles is the horizontal arch effect. The range of effective unloading area is defined. Based on the failure pattern of soil arches and the relationship between soil strength theory and the static equilibrium principle of soil arches, a calculation model is established by considering the presence of geostatic stress and sliding thrust force. The relation between soil strength and critical height is studied by variation of cohesion and friction angle. In addition, the impact of canonical distributions of the earth pressure to the vector height of unloading area is also discussed. Finally, the calculation model is verified by an example from real engineering work.     

Comparisons of Methods for In-Plane Bearing Capacity Calculation of Two-Hinged Parabolic Steel Arch Under Full-Span and Half-Span Loads

The internal force would vary largely with different load ratio for steel arches under combined full-span with half-span loads. However, most relevant formulas on in-plane stability capacity of steel arches were obtained by studying the stability under a single load. Thus, it lacks full considerations of the applicability of bearing capacity formulas under a combined full-span load with half-span load. To overcome this shortcoming, the two-hinged parabolic steel arch was used to compare the results of bearing capacity of arches with different load ratios, rise-span ratios and sections calculated by several methods, The method proposed in the current Chinese design specification of steel arch structure and the finite element method based on the perfect arch and the consistent imperfect arch were included. The results showed that the method in the specification for designing a steel arch would be conservative with a large ratio of the full-span load to the total loads while unsafe with a large ratio of the half-span load to the total loads.     

Study and Application of High Precision Nonlinear Plane Stress Element

A tangent stiffness matrix for quadrilateral plane stress element under large rotation with small strain is proposed in this paper,The corresponding program based on this theory has been worked out;The computation of examples with analytic values has verified that the element's formulation, its program given in this paper have strong nonlinear computation ability;A nonlinear whole-course analysis of stone arch bridge has been done in this paper.The computations presented preferably a comprehensive understanding of nonlinear characteristics of stone arch bridge with small span and could be beneficial for the engineer designers.     

Shear Capacity Calculation Analysis of Reinforced Concrete Beams Based on Truss-arch Model

According to the theory of truss-arch model, the shear mechanism of reinforced concrete beam was analyzed, and formula of shear bearing capacity was proposed. In this formula, softening effect of concrete and the arch function were taken into account, and the coefficients in the formula were amended with experimental data. When the performance difference between the structural material and the original material is huge, the code formula of shear bearing capacity calculation is inapplicable. After the computation, the ratio of the results calculated by truss-arch model theory formula and the results calculated by the current code formula was close to 1, and the standard deviation coefficient and coefficient of variation were smaller than those of standard formula results, and the results calculated by truss-arch model formula were in good agreement with the experimental results. The collected experimental data was calculated with the shear capacity formula in ACI318-08, and the calculation results showed that United States building code was more conservative than the standard of China. The results indicate that the shear bearing capacity formula based on truss-arch model can be used for computation of shear bearing capacity of reinforced concrete beams.     

Full Aero-elastic Bridge Model Design of Long Span Arch Bridge

Aero-elastic model design is the precondition of full bridge aero-elastic model tunnel tests. The full aero-elastic bridge model design of long span arch bridge is discussed. The effect on the model design of different transverse rod space and bend stiff is analyzed in detail. Different scheme need to be designed according to the transverse rod stiff. Considering the changing section dimensional arches, the method of projecting the spatial arches to the plane arches, then designing the plane arches, at last projecting the plane arches to the spatial arches is proposed at first. The results show that the method is effective.     

Experiments on heat loss characteristics in a fully opened cylindrical cavity receiver

The climate has a great impact on highway bridge rubber bearings than on building rubber bearings. In order to study the change of the mechanical properties during the life of the plain chloroprene rubber bearings of highway bridge under freeze-thaw cycle condition, the plain chloroprene rubber bearings were processed 25, 50, 75, 100 times by freeze-thaw cycle in the standard freeze-thaw chamber, then the axial compression tests were carried. The changes of the performance indicators in the bearing capacity , the ultimate compressive strength, vertical stiffness, elastic modulus under different freeze-thaw cycles were analyzed comparatively. The results show that the plain chloroprene rubber bearings are more prone to brittle failure after the freeze-thaw cycle, and the failure phenomena of steel plate exposing or cracks is more serious than the phenomena of the standard specimen. With the increase of the number of freeze-thaw cycle, the ultimate bearing capacity, ultimate compressive strength and compressive elastic modulus of the plain chloroprene rubber bearings decrease. The attenuation formula and decay curve in 50 years of ultimate compressive strength and elastic modulus of compression are analyzed by least square method, the trends of change are both in line with the exponential function. The mechanical properties of plain chloroprene rubber bearings of highway bridge significantly decreased under freeze-thaw cycle condition. therefore, the temperature ranges of plain chloroprene rubber bearings of highway bridge should be strictly controlled, and some suggestions, such as increasing its minimum applicable temperature, usng the natural rubber bearings as much as possible in cold regions, have been given.