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1.
Numerical Method for Load Bearing Capacity of High Strength Steel Columns at Elevated Temperature 总被引：2，自引：0，他引：2
In order to make fire resistance design of high strength steel columns in building structures, the numerical calculation method on load bearing capacity of high strength steel columns at elevated temperature was investigated. By taking the mechanical property of high strength steel at elevated temperature into consideration, extension was made on the inverse calculation segment length method and the program to compute the load bearing capacity of high strength steel columns at elevated temperature was performed. The program was adopted to compute the load bearing capacity. The results obtained by the program and the finite element analysis were compared and good agreement had been found. The influence of magnitude, distribution mode of residual stress and initial geometry imperfection on ultimate load bearing capacity was analyzed by employing the program. It is shown that the extended method can be is shown used to calculate the load bearing capacity of high strength steel columns at elevated temperature; the magnitude and distribution mode of residual stress had little influence but the geometry imperfection have significant influence on ultimate load bearing capacity. 相似文献
2.
In order to investigate the fire resistance of high strength steel beams made from Q460, the method to compute temperature distribution of high strength Q460 steel beams was derived and the temperature distribution was calculated by using finite difference method. The modified equations of temperature for components of steel beam were proposed. According to critical moment at room temperature and mechanical properties of high strength Q460 steel at elevated temperature, the critical moment and stability checking coefficient were obtained by analysis. The load bearing capacity and critical temperature as well as stability factor were studied by using equivalent stiffness method through considering the effect of temperature gradient on stiffness. 相似文献
3.
In order to investigate the fire resistance of steel columns with partial fire retardant coating damage in fire, based on the differential equation of equilibrium on each portion of steel column, the deflection of steel column after the fire retardant coating damage was derived, with the pined ends and rigid ends of the columns at elevated temperatures. The critical temperature calculation method was proposed for partial fire protection damage and axial restrained steel columns by taking the edge yielding criteria. The deflection and axial displacement were verified by finite element method at elevated temperature. With a case study, the critical temperature and relationship of axial force and temperature were obtained for pined column with axial restraint. It was shown that the axial force of the steel column at elevated temperatures was increased and the critical temperature was decreased by the axial restraint. The longer the fire retardant coating damage was and the higher the axial restraint was, the lower the critical temperature was. 相似文献
4.
Experiments and analysis were carried out for the axial compression performance of reinforcement concrete filled tubular steel(CFTS). The deformation capacity and ultimate load capacity were investigated with the analysis of load bearing behavior, deformation capacity and failure modes of the reinforcement CFT short columns. And the influence of reinforcement on the deformation and ultimate load capacity were analysed as well. Finally, the calculation method for axial bearing capacity of reinforcement CFT short column was discussed and a simplified calculation formula was proposed. It was indicated that the columns’ failure modes were changed and their ultimate load capacity and deformation performance were improved by reinforcement. 相似文献
5.
The first degree second order moment method (JC method) recommended in Unified Standard for Reliability Design of Building Structures (GB500682001) was applied to analyze the reliability of steel reinforced high strength concrete filled steel tubular slender columns. Several performances were studies, which were the influences of different load combinations, specific values of loads, strength grades of concrete, thickness of steel tube, area of cross section of structural steel, steel yield strength and slenderness ratio on the reliability of the composite column. It was found that, when the slenderness ratios were within common range, the reliability indexes of the proposed formulae satisfied the demand of GB500682001 for plastic material on the whole. And it was concluded that the reliability index varied with the load combination and specific value of loads. The reliability index increased with the increase of concrete strength grade and decreased with the increase of steel tube thickness. Furthermore, steel yield strength and slenderness ratio had different influences on the reliability indexes. 相似文献
6.
The effects of the restraint stiffness ratio, the axial load ratio and the column slenderness on the buckling temperature and failure temperature of a restrained H section steel column under axial load in fire were studied with a calibrated finite element method (FEM) model. And the calculation methods of buckling temperature and failure temperature were proposed. The effect of the restraint stiffness ratio on the buckling temperature and failure temperatures could be expressed with an exponent curve while polynomial functions was appropriate for the effects of the axial load ratio and the column slenderness. The results of the proposed method were in good agreement with those by FEM method and on the safe side. 相似文献
7.
For exploring the practicality of engineered bamboo products in timber structure, the formula of dowel bearing strength parallel to the grain was investigated. In this paper, seven groups of twenty eight specimens were tested. The effect of the thickness of engineered bamboo products, end distance and pin diameter on the maximum load, stiffness and dowel bearing strength were analyzed. It was showed the thickness of engineered bamboo products had no effect on the dowel bearing strength. The effect of end distance on the dowel bearing strength could be negligible with the end distance greater than 64mm. And the dowel bearing strength approximately linear improved with the decrease of pin diameter. The influence coefficient of pin diameter was obtained by regression analysis. Finally, a simplified theoretical calculation formula of dowel bearing strength was establishment. And the results of dowel bearing strength by the theoretical calculation formula had a good agreement with those obtained by test. 相似文献
8.
Single-lap-joint adhesively bonded metal specimen which is the national standard experimental method in use has an extremely non-uniform distribution of shear stresses along the joint, and tensile stress concentration of high values is produced on the steel substrate interfaces. Therefore the test result, which is not the real bonding shear strength between adhesive and steel substrates, can only be used as a test index for qualities of adhesives not the strength criterion for load is capacity evaluation. The combined bonding disc specimen is adopted for measuring bonding shear properties of adhesive on steel substrates, has a very uniform distribution of shear stresses in adhesive and along the bonding surfaces of steel substrates, of which the uniform coefficient is greater than 0.97. Furthermore, when adhesive joint is treated as an arc and steel substrates are chamfered at both ends of the joint, tensile stresses on the bonding surfaces can be reduced to less than 20 MPa which can hardly cause tensile failure. Thus, the results of combined bonding disc specimens can actually represent the real bonding shear strength or bonding shear-compression strength between adhesive and steel substrates, which can be used as strength criterion for load capacity evaluation of bonding members. 相似文献
9.
In the previous companion paper, the fire resistance of high strength steel beams made from Q460 was theoretically studied. The methods to obtain temperature distribution, critical moment, critical temperature and stability coefficient were presented. The temperature distribution and load bearing capacity was analyzed by finite element method, and the validation was evaluated by comparison of results between theoretical computation and finite element analysis as well as experimental results. The comparison was made between Q460 steel beam and mild Q235 steel beam and the difference on fire resistance was obtained. A simplified approach for fire resistance of high strength Q460 steel beams was proposed and an example was given to show the application and reference of the approach. 相似文献
10.
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. 相似文献
11.
The Quasi static tests of one steel frame and two the composite deep beams infilled steel frames were carried out. The effects of the deep beams on the load capacity, ductility, hysteretic property and energy dissipation of pure steel structure were analyzed. It is found that the hysteresis curve is a straight line with the constant of the stiffness at the beginning and without residual deformation. And the hysteresis curve of specimen was full after yielding, and the skeleton curves had a clear plastic flow phase with triple linear. The lateral drifts of the beam specimens at failure were 1/25 and 1/22. The composite deep beams enhance the initial stiffness, yield load and maximum load bearing capacity of steel frame. Therefore, seismic performance of the composite deep beams is better. 相似文献
12.
As for the local buckling of aluminum bending members, a finite element analysis of the stability of aluminum plates under bending was performed. Compared with the results of codes’ method and finite element method, the advantages and disadvantages of existing codes were discussed. Base upon the results of simulation, the relevant design formula in Code for design of steel structures (GB50017) were modified with the reference of existing foreign codes. And the design methods were proposed for buckling strength and post buckling strength of aluminum plates under in plate bending. It was found that the results of proposed methods were in high accuracy and safer condition, and suitable for the stability design of aluminum plates under in plate bending. 相似文献
13.
Because section steel can only be extended to the edge of the support, when a simple support RC beam is reinforced by bonded section steel, a notch comes into being at the end of the beam which is called a secondary dapped end beam, making the stress state of the beam more complex. Through experimental analysis on 21 dapped end beam specimens shear reinforced by steel plate bonded, the deformation process, performing characteristics and failure mechanism of the specimens were investigated. The result shows that two steel bonded forms, including horizontal steel plate and oblique steel plate with angle 45° bonded, delay the appearance of cracks significantly and improve the maximum bearing capacity by 102% and 93%. Due to the impact of stress concentration at the notch, the main modes of damage include concrete tensile or shear failure with the result of bonding failure of a steel plate. By changing the width of steel plates and analyzing different reinforcement effects, formula of bearing capacity of shear reinforcement was proposed based on the method of truss analogue, which provides a reference for engineering application. 相似文献
14.
The finite element software ABAQUS is used to calculate the deformation of reinforced concrete walls under fire. The calculated results agree well with previous experimental results. Based on the finite element model, the influences of such parameters as axial load level, lateral load level, height-to-thickness ratio, wall thickness, concrete compressive strength, steel reinforcement yield strength, steel reinforcement ratio and concrete protection thickness on deformation and fire resistance of walls are analyzed systematically. It is found that, under the conditions of big axial load level or wall thickness without lateral load and small height-to-thickness ratio, the reverse deflection of reinforced concrete walls in fire is apt to occur. Within the work range of parameters in common use, the fire resistance of walls decreases with the increase of axial load level, lateral load level, height-to-thickness ratio, steel reinforcement yield strength or steel reinforcement ratio, and increases with the increase of wall thickness or concrete compressive strength. 相似文献
15.
Aiming at the lack of the current determination method for voids in practical engineering applications, in order to accurately quantify the voids beneath cement slab, the determination method was proposed with slab edge slab center deflection difference and slab corner slab center deflection difference in the same cement slab for voids.Three dimensional models were set up using the ANSYS finite element method for voids beneath slab corner and slab edge.And the load was simulated with FWD test results.Thereafter, the deflection values were calculated in slab center, slab corner, slab edge under different void depth, void area and load transfer capacity.And the range of deflection diffidence was obtained.With Yantai Weihai expressway, detection data for deflection using Falling Weight Deflectometer were statistically analyzed.And the criteria and correction factors of load transfer capacity were given with simulation and samples analysis.The feasibility of criteria was verified by actual test data.It is found that the simulation values and the test values are in good agreement.The accuracy of void determination by lab edge slab center deflection difference and slab corner slab center deflection difference are 88.5% and 84.6%, respectively, which meet the engineering requirements.The voids were determined under the same conditions with the elimination of deflection variability. 相似文献
16.
In order to investigate the effect of prestressed binding bars on axial compressive behavior of rectangular concrete-filled tubular (CFT) short columns, five rectangular CFT short columns, three with prestressed binding bars, one with ordinary binding bars, the other with no binding bars, were constructed and tested under axial compressive loads. The binding bars were made up with high-strength bolts. As used for ordinary binding bars, the high-strength bolts were welded to the steel tube before the column was loaded to axial compressive force. As used for prestressed binding bars, the high-strength bolts were first tensed by screwed screw cap down to bring force to prestress the steel tube and its core concrete, then welded to the steel tube before the column was loaded to axial compressive force. Test results indicate that the bearing capacity and ductility of rectangular CFT short columns are increased by setting binding bars. Compared to ordinary binding bars, the prestressed binding bars can decrease the longitudinal displacements corresponding to ultimate strength, but have little effect on the ultimate strength and displacement capacity after ultimate strength of the columns. The longitudinal displacements corresponding to ultimate strength of the columns decrease with the decreasing of space between binding bars. With the same section width and amount of binding bars, the bearing capacity of the columns improves with the increase of section long-broad-ratio, while displacement capacity after ultimate strength decreases with the increase of section long-broad-ratio. 相似文献
17.
Eight concrete beams reinforced with 500MPa steel bars and four reinforced with 400MPa ultra fine grain steel bars were tested under two point symmetrical concentrated static loading to observe the details of crack pattern development on these beams and investigate their cracking characteristics. It was shown that the cracking behavior of the beams with high strength bars was essentially similar to that of common RC flexural members, whereas the computed crack widths using the formula adopted in the Code for Design of Concrete Structures GB 50010 2002 exceeded that of the experiment under the normal service. Furthermore, the formulas for crack spacing and crack width specified in GB 50010 2002 were evaluated through the experimental results and previous studies of sixty seven concrete beams reinforced with high strength bars. On the basis of the calculation model in GB 50010 2002, revised formulas for crack spacing and crack width were proposed. The values calculated by revised formulas were in good agreement with the test results. 相似文献
18.
The finite element model involving geometric large deformation,materials and contact nonlinearity is established.Specimens of cold-formed steel quadruple-C built-up section members are simulated and the finite element models are proved to be valid.Then,numerical analysis on the behavior of specimens with different slenderness ratio and flange flakiness ratio are carried out,and then the axial bearing capacities of specimens are obtained.Based on effective width method and direct strength method (DSM) in related codes,two design methods of cold-formed steel quadruple-C built-up section members under axial compression are proposed:effective length method and correction factor method.It is shown that:the final failure characteristics of all specimens are local buckling and distortional buckling.In the case of not considering the reduction of effective length,the results calculated by each code are slightly lower than those of test and FEM when the slenderness ratio is less than 50,while the results are too conservative when the slenderness ratio is more than 50. 相似文献
19.
Traditional nonlinear analysis of RC structures usually adopts nonlinear FEM based on continuum mechanics, and it is hard to reflect macroscopic deformation characteristic, such as local rotation in crack sections and plastic hinge of failure stage. From the perspective of physical model, a new deformation condensation method is developed. The analysis of RC flexural members in the 1-D elastic problem involve three stages based on the concept of deformation condensation. RC flexural members were divided into several elements according to average crack spacing to get numerical model consistent with the physical model with higher computational efficiency tests of RC flexural members reinforced with high strength rebars conducted by Institute of Prestressed Structures in Tongji University, were simulated and the simulation results agreed well with the experimental data indicating that this novel method is applicable. 相似文献
20.
In order to study bearing characteristics of deep rock-socketed piles (hr/b≥5), based on the test results of self-balancing test of zh12 pile in Qingdao Gulf Bridge, the bearing characteristics of deep rock-socketed piles were analyzed. The relation between sides shear resistance of the piles and its displacement socked in soft rock was researched, and the relation between end bearing resistance and displacement was studied. The hyperbolic distributions on the load transfer method were compared to them. The results indicate that Q -S curve of large diameter deep socketed pile in soft rock area declines slowly, approximately in linear distribution. According to the fitting curve based on measured results, it is feasible to fit the relationship between sides shear resistance and its displacement by using hyperbola. The parameter of 1/b also reflects the ultimate side resistance values of piles. The load-displacement curve at the top of pile is similar to the hyperbolic form. By using the parameters of a、b obtained from fitting curve, the calculated load-displacement curve on top of pile is close to the measured curve of self-balance method. At last, according to the measured results, the value range of parameterαin empirical formula was analyzed under different states of axial compressive strength. 相似文献