共查询到20条相似文献，搜索用时 31 毫秒
1.
In With one-storey, two-span prestressed frames, a comparative study is done between under vertical and horizontal loads. The studies include the pattern of the plastic hinges occurring and, the demanded and available rotational capability of the hinges in critical sections. The relative height of compression zone and prestressed degree are considered. The result indicates that there is much difference in the pattern of the plastic hinge occurring when each plastic hinge has enough rotational capability. The beams can finish a full redistribution of internal force under vertical loads, but not under horizontal loads. Moreover, as increasing of the relative height of compression zone, a stronger rotational capability of hinges will be demanded to finish a full redistribution under vertical loads when a weaker rotational capacity will be needed under horizontal loads. 相似文献
2.
An analytical solution was presented for the stresses and displacements around horseshoe-shaped tunnel using Cauchy integral method and Optimization theory in an elastic half-plane. Since the depth of a tunnel was larger than the size of the tunnel, gravity loads were simplified as uniform normal loads along far-field boundary. Finite element model was used to verify the accuracy of analytical solutions. Comparison between the results of numerical analysis by finite element method and those from the closed solutions indicates that the closed solution is reliable and applicable for the stress and displacement field around horseshoe-shaped tunnel tunnels at great depth. 相似文献
3.
The finite element of a prestressed concrete (PSC) beam is analyzed in a case of diverse prestressing forces. The mechanical model applied is that advanced by Clough for a concrete beam bearing axial force. The results indicate that the beam frequencies decrease with increasing prestressing force. A dynamic experiment of a non bonded PSC beam was carried out to validate the veracity of the finite element analysis. Test beam frequencies increase with increasing prestressing force. The analysis model thus is unfit for frequency analysis of a PSC beam. The determinant factor of frequencies is analyzed, and the dynamic model is modified according to experimental results. The modified model analysis result shows that: the calculated frequencies of mode 1 agree with the test results well; the frequencies of mode 2 posses some errors; and, the modified model can reflect the direction of frequency change along with the change of prestressing force well. 相似文献
4.
Zhang Peiyuan Liu Song 《保鲜与加工》1989,(2):10-16
It's recommended that the term coupled in temperature and strain is nonlinear and is significant in thermoelastic theory. Using the solution of linear coupled and uncoupled theory and selecting appropriate general coordinates, authers approach the nonlinear coupled problems with a variational method. A solution to the problem in half space, is given. It is shown that the difference between the nonlinear coupled theory and the linear coupled or uncoupled theory would be notable when the amplitute of temperature is much larger than that of the reference slate. 相似文献
5.
Through many tests and standard analysis, the effects of solution concentration and temperature on rate of concrete sulfate attack were investigated. The test results show that when solution concentration and temperature are lower than certain value, the speed of attack is accelerated with increasing concentration and temperature, however, higher temperature and concentration of solution may decrease the rate of attack. The speed of attack of sodium sulfate is faster than the one of attack of magnesium sulfate under various factors. It is suitable to adopt the coefficient of tensile as the accelerated assessing criterion for the attack of sodium sulfate. The coefficient of tensile and compressive strength should be considered together for the attack of magnesium sulfate. 相似文献
6.
Random-amplitude fatigue load spectrum for experiments is made according to the ubiquitous three-parameter Weibull distribution in gear transmission. Gear bending fatigue test under the random load is carried out on a MTS electro-hydraulic servo material fatigue tester by using group testing method,and the S-N curve of gear bending strength under three-parameter Weibull distribution with specific variation coefficients is obtained. The fatigue test results show the gear’s endurance life under random load is far less than that under constant load when the load submits to three-parameter Weibull distribution random load spectrum. The theoretical value of fatigue limit for gear under random load is predicated and compared with test results. The theoretical value is in accordance with the test results. Therefore,the fatigue strength of gear bending under random load can be deduced according to the load ratio coefficient of random load spectrum. 相似文献
7.
The governing partial differential equations (PDEs) are deduced from the asymptotically correct, geometrically nonlinear theory to research the bucking and mode jumping behavior of biaxially antisymmetric angle-ply composite laminates. The PDEs are transformed into a system of nonlinear ordinary differential equations (ODEs) by using the generalized Galerkin method. Then, the post-buckling behavior is analyzed by using the solution extension software. At last, the paths of buckling mode jumping and critical loads for the composite laminates under the in-plane boundary condition of straight edge are determined. An example of 4-layer composite laminates shows that the numerical results in the primary post-buckling region from the present method agree with the finite element analysis (FEA); while the FEA may lose its convergence when solution comes close to the secondary bifurcation point, the analytic method has the capability to explore deeply into the post-secondary bucking realm and capture the mode jumping phenomenon. 相似文献
8.
Based on the fact that existing bend component is tend to produce inflection point on the steel strand by its small radius, the experiment is designed to study the influence of steel strand mechanical properties by bend component with specific radius R and bending angle θ. The law and mechanism of ultimate strength, ductility of steel strand and prestressing loss due to friction affected by R and θ is analyzed detailly. The results show that the radius of bend component should be as large as possible to improve the mechanical property of steel strand, and it shouldn't less than 100mm when the size is limited. In addition, the uniform calculating formulas of prestressing loss due to friction is presented based on experiment data, which take the affection factor of R into account. 相似文献
9.
The accurate calculation of the deformation capacity of structures is very important to performance-based seismic design, which satisfies the explicit deformation demands. The method to evaluate drift capacity of fiber reinforced polymer (FRP) confined reinforced concrete circular columns under simulated seismic loading is focused. Firstly, the moment-curvature relationship of FRP confined sections of reinforced concrete (RC) circular columns is simulated by numerical analysis. It is found that the calculated ultimate curvature is significantly less than the test result, and the difference is controlled by the axial load ratio of the tested columns. According to the numerical and the test results, an equation is proposed to modify the calculated ultimate curvature. Based on this, the drift capacity can be predicted with the equivalent plastic hinge method. The calculated result agrees well with the test result when FRP amount is low, but it is significantly larger when FRP amount increases. Finally, the main parameters exerting influences on the drift capacity of the FRP-confined RC circular column are analyzed. 相似文献
10.
During the pre - stressing of the unbonded prestressed concrete wide flat beam - waffle slab system, the displacements and strains of slab and the prestressed concrete beams were site - measured and the results were analyzed. The prestressing construction was simulated by finite element program. The prestressing efficiency of the unbonded prestressed concrete wide flat beam - waffle slab system was discussed. It indicates that the prestressing efficiency was affected by the in -plane stiffness of slab. 相似文献
11.
As the self weight of cable affects mechanical behavior obviously with the inerease of span length.FRP (fiber reinforced polymer) cable that has the lighter weight than the conventional cables has advantage for long span structures.The analysis of single cable is the fundamental theory for the design of cable structures.Based on different considerations of gravity loads.the solutions of the single cable on gravity loads have three sets of solutions: parabola solution.catenary solution and elastic catenary solution.And the equations for the three sets of solutions are derived by taking the end tension force of cable as the control parameter.The comparison between FRP cables and steel cables is conducted by elastic catenary solution.and the results show that the lager span structure can be realized by FRP cables.The precision for the parabola solution and catenary solution is compared for stay cables and horizontal cables.and the proper ranges of both approximate methods are proposed.Based on the above methods.the ultimate span length of FRP cable and steel cable are analyzed.It is concluded that the ultimate span of FRP cable is 4.4 times larger than that of steel cable. 相似文献
12.
The performance of heat transfer of fin-tube with circular hole is better than fin-tube without hole if there is no frost,but what is the situation if under the frost condition.Tthe comparison study on performance of heat transfer and refrigeration is carriedout under the frost condition for the heat exchanger with three kinds of fins: circular and half circular hole,circular hole,plane form.The experiment process is finished through the refrigeration system of icebox.In the course of experiment,the influence of frost process to the diameter of circular hole;is analyzed The real refrigeration amount,heat transfer coefficient and real refrigeration coefficient of the three kinds of fins are compared;compare the effect of energy saving of enforced fins is given.The fin efficiency is calculated method and make out the real convection coefficient to disclose the situation of heat transfer of fins is lnade out.Results: compared with plane form fin,the following results are for fin-tube with circular hole: average heat transfer coefficient rise 11.53%,convection coefficient rises 18.84%,real refrigeration coefficient rises 6.83%,virtual refrigeration amount rises 6.02%,electricity saving is 6.39%.Fin-tube with circular hole is the best form for the three kinds of fins. 相似文献
13.
To get the spatial distribution characteristic of roadway's surrounding rock stress, circular section roadway was taken as a case study. The solution of stress was got by using complex function method, and roadway's surrounding rock stress field was analysed after the solution of mapping space was transformed into the solution of roadway space. As a result, the visual diagram of stress field distribution of roadway's surrounding rock was obtained, which could describe intuitively stress distribution of roadway's surrounding rock at any position. Considering the influence of different radius and side pressure coefficients on surrounding rock stress field, the following conclusions have been obtainded: the peak value and direction of circular roadway's surrounding rock stress has nothing to do with the radius; when side pressure coefficient is less than 1/3,the roof can produce tensile stress; when side pressure coefficient is more than 3, the surrounding rock in two sides can produce tensile stress. And the change rule of hoop stress, radial stress, shear stress and the maximum and minimum of stress have also been generated. 相似文献
14.
LARGE DEFLECTION OF A CIRCULAR PLATE ON PASTERNAK FOUNDATION UNDER A CONCENTRATED LOAD AT THE CENTER
Liu Dong Liu Longquan 《保鲜与加工》1992,(4)
Based on Karman's nonlinear foundamental differential equations, the new method combines perturbation method with integral equation method is forward to solve nonlinear bending of a clamped circular plate on Pasternak foundation under a concentrated load at the center. This method is simple and easy to use. The numerical results show that the present solution is reliable. 相似文献
15.
The dynamic behaviour of a new reinforced concerte hollow plate using the medium strength(800 MPa yield strength)ribbed bar as prestressed wire has been studied experimentaly under various concentrated impact loads.The test results on the inherent characteristics,frequency,damping,dynamic rigidity etc.are presented.Meanwhile the important points in respect to the strength,deformation,cracking under impact loads and earthquake response of plate have discussed. 相似文献
16.
This paper introduces the analysis and test of prestressed flat beams in tube-in-tube concrete structures at different construction stages; moreover, the corresponding structural analysis models with FEA program are set up. Through the comparative analysis between the results of construction field test and that of calculation with FEA method, it proves the reliability of the primary design method; meanwhile, it also indicates that establishment of prestressing force and prestressed effects in similar structures is a complex procedure and should be noticed. 相似文献
17.
Based on the project of a prestressed concrete beam-slab structure,this paper introduces the optimum design of a four-spanned exceedingly long prestressed floor. Different schemes,such as the scheme of the prestressed major beam,the scheme of the prestressed secondary beam with the same span and the scheme of the prestressed secondary beam with different spacing,are compared and analyzed in this paper.Meanwhile,various methods of the exceedingly treatment for long prestressed reinforcement are compared.Finally,based on two prestressed beams,the prestress loss,the prestressing value at the ends of the beam and the deflection in the midspan of the beam are detected during the tension and anchorage stage in order to verify the results of the theoretical analysis. 相似文献
18.
In order to study the stress distribution effect of the webs which is under the action of vertical prestress, pairs of forces were acted on a long and narrow rectangular thin plate, and the webs stress field under the effect of vertical prestressing was simulated, with analytical solution of vertical normal stress derived and the numerical solution obtained by the Least-square method. The parameters,λ and κ, were introduced and calculated to describe vertical stress uniformity and stress level, which shows that λand κ value are more sensitive to webs vertical reinforcement spacing. On the premise of uniformity of vertical prestress and stress level, the fitting diffusion angle of vertical prestress acting on the webs is obtained and fitted by polynomial. Vertical prestress diffusion effect of the webs was tested in bridge site and analyzed by the finite element software. The results show that the webs stress diffusion is obvious, and the stress has a good uniformity at the section of H/2 but a bad uniformity at axillary and shore up. 相似文献
19.
An analytical solution of the elastic circular plate on multi layered soil can be obtained by using the transfer matrix solutions for displacements and stresses of multi layered soil. This solution is based on the continuity of vertical displacements and the smooth contact conditions between a multi layered soil surface and the elastic circular plate. Numerical calculation and analysis are carried out by the computer program compiled for this purpose. The numerical results show that the rigidity of the elastic circular plate greatly influences the displacement of the circular plate and the normal stresses under the center of the circular plate. 相似文献
20.
Amino-functionalzed mesoporous MCM-41（AP-MCM-41）is synthesized by the microwave method, using 3-aminopropyltriethoxylsilicane（APTES） as the coupling agent, and through polymerizing AP-MCM-41 with N-isopropylacrylamide (NIPAAm), a typical composite material which is sensitive to temperature is synthesized. By low-temperature N2 absorption-desorption, X-ray diffraction, Fourier transform infrated spectroscopy and thermogravimetry analysis etc., it’s found that the new composite material possesses temperature sensitivity. Selecting hydrochlorothiazide as a model drug and using the impregnation method, its release behavior under different temperatures are studied. The results show that when the temperature is higher than the lower critical solution temperature (LCST), the hydrophobicity of the material that blocks the releasing of the drug will be formed, and when the temperature is lower than the LCST, the release amount will increase significantly due to the hydrophilicity of the material. 相似文献