CN116541934A - Analysis method for earthquake resistance of aging reinforced concrete sluice structure - Google Patents
Analysis method for earthquake resistance of aging reinforced concrete sluice structure Download PDFInfo
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- 239000004567 concrete Substances 0.000 claims abstract description 116
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 92
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- 230000007797 corrosion Effects 0.000 claims abstract description 50
- 238000005260 corrosion Methods 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 42
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
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Abstract
The invention discloses an analysis method for earthquake resistance of an aging reinforced concrete sluice structure, which establishes a three-dimensional finite element model of the sluice chamber structure comprising a foundation, a water body, a sluice pier, a sluice bottom plate, a steel sluice, an upper opening and closing machine room structure and steel bars according to the characteristics of the sluice chamber structure, adopts a finite element numerical simulation technology, considers the influence of concrete carbonization and steel bar corrosion, analyzes nonlinear earthquake damage of the aging sluice structure, and clarifies the influence mechanism of the aging effect on the earthquake resistance of the sluice structure. The method can accurately and scientifically reflect the influence of the aging effect on the earthquake resistance of the sluice structure, and fills the blank of the earthquake resistance analysis of the existing aging sluice chamber structure at the present stage.
Description
Technical Field
The invention relates to earthquake-proof safety analysis, in particular to an analysis method for earthquake-proof performance of an aging reinforced concrete sluice structure.
Background
The sluice has the dual functions of water retaining and water draining, and is widely applied in hydraulic engineering. The large and medium-sized danger sluice has the problem of reinforced concrete diseases, and the distribution position of the diseases is wide, the form is various, the cause is complex, the bearing capacity and the durability of the sluice are seriously influenced, and the sluice has great potential safety hazards for the normal operation of the sluice, and meanwhile, the sluice also brings great engineering loss and repair cost, and must be highly valued.
Reinforced concrete diseases are one of the problems which are more prominent in the current sluice, wherein concrete carbonization and steel bar corrosion phenomena are particularly common; meanwhile, many earthquake disasters of the sluice show that the sluice is seriously damaged by the earthquake compared with other hydraulic buildings. Therefore, there is a need to make more intensive studies on the mechanism and development law of these two disease phenomena and their influence on the bearing capacity and durability of the sluice structure under the action of earthquake.
At present, scholars at home and abroad conduct a great deal of researches on the earthquake resistance of carbonized concrete and aged reinforced concrete structures, but the scholars are mostly concentrated on the layers of reinforced concrete members and the scholars are concentrated on bridge and frame structures; in addition, the research emphasis is mainly on structural reinforcement and earthquake resistance evaluation, the research method is mainly based on model tests, most of the tests are corrosion test pieces, and the corrosion method is usually electrochemical rapid corrosion. In fact, the sluice structure is not only complex in form, but also often in a dry-wet alternate operating environment, and the concrete carbonization and steel bar rust phenomena are more pronounced, relative to bridge and frame structures. However, no related research on the influence of concrete carbonization and steel bar corrosion on the earthquake-resistant performance of the sluice structure is yet known, and the concrete carbonization and steel bar corrosion are exactly concerned by sluice management and engineering designers.
In summary, the existing earthquake-resistant analysis method for the sluice structure is concentrated on the reinforced concrete member level, does not consider the influence of concrete carbonization and steel bar corrosion, and is not suitable for analyzing the earthquake-resistant performance of the aged reinforced concrete sluice structure.
Disclosure of Invention
The invention aims to: the invention aims to provide an analysis method for the earthquake resistance of an aging reinforced concrete sluice structure, which solves the problem that the existing analysis method does not consider the influence of concrete carbonization and steel bar corrosion and cannot accurately analyze the earthquake resistance of the aging reinforced concrete sluice structure.
The technical scheme is as follows: the invention discloses an analysis method for the earthquake resistance of an aging reinforced concrete sluice structure, which comprises the following steps:
(1) According to the structural size and reinforcement condition of the existing sluice chamber, a three-dimensional sluice chamber structure finite element model is established, wherein the model comprises a foundation, a water body, a sluice bottom plate, a sluice pier, a steel gate, a highway bridge, an upper opening and closing machine room structure and concrete inner reinforcement;
(2) Based on ADINA finite element analysis, taking infinite foundation radiation damping effect, concrete dynamic damage, bonding slip effect of reinforced concrete, fluid-solid coupling effect of a water body and a sluice structure, carbonization and corrosion effects into consideration, inputting preset material parameters, boundary conditions and different loads, and carrying out nonlinear earthquake damage calculation on the established model to obtain dynamic responses of all parts of the sluice structure with different carbonization depths and different corrosion degrees under the action of earthquake load;
(3) Selecting characteristic points of the area with the maximum displacement, stress and damage values based on the calculation result of the step (2),
and drawing a change curve of displacement, stress and damage values of the characteristic points along with the earthquake duration, wherein the curve takes the earthquake duration as a horizontal axis and takes displacement response, stress response or damage values as a vertical axis.
The foundation unit range in the step (1) is based on the upstream, downstream, left side, right side and bottom elevation of the gate bottom plate, and the foundation unit range extends to the upstream, downstream, left bank, right bank and vertically downward by 2 times of gate chamber heights, wherein the gate chamber heights are the difference between the top elevation of the opening and closing machine room and the bottom elevation of the gate bottom plate. Meanwhile, in order to facilitate the establishment of a model, the nodes of the upstream and downstream water units are shared with the gate pier and the steel gate node; in the single spring coupling unit method, the normal displacement of the steel bar nodes is calculated according to the following formula, and the concrete formula is as follows:
in the method, in the process of the invention,the displacement value is the displacement value of the ith dimension of the steel bar node under the local coordinate system; n is the model dimension; r is (r) ij Is an interpolation coefficient, namely a coordinate transformation matrix element; u (u) j And the displacement value is the j-th dimension displacement value of the concrete node under the integral coordinate system.
The mechanical parameters of the carbonized concrete in the step (2) are specifically as follows:
f c ＝1.6f c0
E c ＝1.6E c0
ε c ＝0.7ε c0
wherein f c 、E c 、ε c Respectively the compressive strength, the elastic modulus and the ultimate strain of carbonized concrete, f c0 、E c0 、ε c0 Compressive strength, elastic modulus and ultimate strain of the completely uncarbonated concrete respectively;
the mechanical properties of the existing non-carbonized concrete are as follows:
wherein E is t 、β d The elastic modulus and the ductility ratio of the existing uncarbonized concrete; e (E) 0 The elastic modulus of the new concrete with the same strength; t is the service life of the existing non-carbonized concrete;
the carbonization depths were selected from 1cm, 3cm, 5cm, 7cm and all carbonization, and the dynamic response was calculated for finite element models of different carbonization depths.
The relation between the mechanical parameters of the rusted steel bars and the rusting rate rho in the step (2) is specifically as follows:
when 0 < ρ% -5%:
f y,c ＝f y0 (1-0.029ρ)
f u,c ＝f u0 (1-0.026ρ)
δ s,c ＝δ s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (1-0.052ρ)
when ρ% > 5%:
f y,c ＝f y0 (1.175-0.064ρ)
f u,c ＝f u0 (1.18-0.062ρ)
δ s,c ＝δ s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (0.895-0.031ρ)
wherein E is u,c ，f y,c ，f u,c ，δ s,c ，ε y,c The nominal elastic modulus, the yield strength, the ultimate strength, the elongation and the ultimate strain of the rusted steel bar are respectively; e (E) u0 ，f y0 ，f u0 ，δ s0 ，ε y0 Respectively non-rusted steel barsElastic modulus, yield strength, ultimate strength, elongation and ultimate strain;
the bond strength degradation coefficient formula of the post-rust reinforced concrete is as follows:
wherein ρ is the corrosion rate (%) of the steel bar, and β is the reduction coefficient of the bonding strength between the steel bar and the concrete after rust;
the corrosion of the steel bars is selected from 1%, 3%, 5%, 7% and 10%, and the dynamic response is calculated for finite element models of different corrosion rates of the steel bars.
The concrete in the step (2) adopts a four-parameter dynamic damage constitutive model, and the damage criterion is that
Wherein: epsilon * Is equivalent strain; A. b, C, D is four test constants, which can be obtained by combining a uniaxial tensile test, a uniaxial compression test, a biaxial isostatic test and a triaxial compression test; i' 1 ＝(ε 1 +ε 2 +ε 3 ) 3 is the first invariant of the strain tensor;is the maximum principal strain; />The second invariant is the strain offset; />J′ 3 ＝ε 1 ε 2 ε 3 The third invariant is the strain offset; epsilon 1 ,ε 2 ,ε 3 Three-way main strain is respectively adopted; epsilon m Indicating strain under ball stress.
Under the action of earthquake load, the concrete inevitably has unloading and reloading processes of a softening section, and the residual strain calculation in the simulation adopts the following formula:
wherein ε p Is the residual strain value; epsilon 0 ＝f t and/E is the ultimate strain under the tensile strength of the concrete, f t The tensile strength of the concrete is that E is the elastic modulus of the concrete; epsilon un Is the strain value at the unloading point.
The interaction between the steel bar and the concrete is simulated by a single spring coupling unit method based on a mixed coordinate system, wherein the interaction equation between the steel bar and the concrete is that
Wherein Deltau, deltau * And DeltaF, deltaF * Oxyz and O, respectively * x * y * z * Displacement vector increment and load vector increment in a coordinate system; k and k * Oxyz and O, respectively * x * y * z * A stiffness matrix in a coordinate system; k (k) s The method comprises the steps of carrying out a first treatment on the surface of the r is a coordinate transformation matrix; r is (r) T Is the transpose of the coordinate transformation matrix.
The potential fluid unit is adopted to simulate the fluid-solid coupling effect between the front and rear water bodies of the gate and the gate pier and the steel gate under the action of earthquake, and the control equation is as follows:
wherein P represents dynamic water pressure, c represents underwater acoustic wave velocity,for Laplace operator>Is the second derivative of hydrodynamic pressure with time.
The fluid-solid coupling boundary is arranged between the water body and the gate pier, the gate bottom plate and the steel gate, so that the energy transfer between the water body and the steel gate is simulated, and the method is concretely as follows:
wherein n is the external normal direction of the fluid domain on the fluid-solid coupling surface;the absolute acceleration along the normal direction on the fluid-solid coupling surface is represented by ρ, which is the water density.
2 seismic acceleration time-course curves are generated by adopting a triangle series expansion method based on a standard design reaction spectrum, and the velocity and displacement time-course curves are generated through integration, wherein velocity waves and displacement waves are vertically input from the bottom of the foundation based on viscoelastic artificial boundary conditions in the calculation process.
In the step (4), different damage levels of the sluice chamber structure are judged by using the sectional area of the concrete damaged area of the sluice chamber structure under the action of earthquake, and specific judgment standards are as follows:
discriminant criterion
The beneficial effects are that: aiming at the problems existing in the existing aging sluice structure earthquake resistance analysis, the three-dimensional finite element model of the sluice structure comprising a foundation, a water body, a sluice pier, a sluice bottom plate, a steel gate, an upper opening and closing machine room structure and steel bars is established according to the sluice chamber structure characteristics and reinforcement conditions, the nonlinear earthquake damage analysis is carried out on the aging sluice structure by taking the influence of concrete carbonization and steel bar corrosion into consideration by adopting a finite element numerical simulation technology, the influence mechanism of the aging effect on the sluice structure earthquake resistance is clarified, the influence of the aging effect on the sluice structure earthquake resistance can be reflected more accurately and scientifically, and the gap of the existing aging sluice chamber structure earthquake resistance analysis at the present stage is filled.
Drawings
FIG. 1 shows the carbonization of concrete and rust of steel bars in a hollow chamber structure of a shallow-hole gate
FIG. 2 is a diagram of an overall finite element model of a cell structure in a shallow-hole gate;
FIG. 3 is a finite element model of a cell structure in a shallow hole gate;
FIG. 4 is a shallow Kong Zha gate pier and gate bottom plate finite element model;
FIG. 5 shallow Kong Zhagang gate finite element model;
FIG. 6 shallow Kong Zha open-close machine room finite element model
Fig. 7 is a finite element model of a reinforcement finite element model in a shallow Kong Zha open and close machine room rack column;
FIG. 8 is a finite element model of a shallow hole gate overhaul platform;
FIG. 9 is a shallow hole gate highway bridge finite element model;
FIG. 10 is a shallow Kong Zhagang gate and pre-gate water finite element model;
FIG. 11 is a standard design response spectrum;
FIG. 12 is an x-direction acceleration time course curve;
FIG. 13 is a y-direction acceleration time course curve;
FIG. 14 is an x-direction velocity time course curve;
FIG. 15 is a y-direction velocity time course curve;
FIG. 16 is an x-displacement time course curve;
FIG. 17 is a y-displacement time course curve;
FIG. 18 is a schematic view of structural features of a shallow hole gate chamber;
FIG. 19 is a comparison of the river displacement time course curves at feature point A without carbonization and carbonization;
FIG. 20 is a comparison of the first principal stress time course curve at feature point B without carbonization and carbonization;
FIG. 21 is a graph comparing damage values at feature point B for the case of non-carbonization and carbonization;
FIG. 22 schematic diagram of chamber structural damage without carbonization
FIG. 23 is a schematic diagram showing chamber structural damage in the case of full carbonization
Fig. 24 is a comparison of the forward river displacement time course curves at feature point a for the case of non-rusted and 0% steel rust;
FIG. 25 is a graph comparing the first principal stress time course at characteristic point B for the case of non-rusted and 0% steel rust;
FIG. 26 is a graph showing the comparison of damage value time course at characteristic point B for the case of non-rusted and 0% steel rust;
FIG. 27 is a schematic view of chamber structural damage without rusting;
fig. 28 is a schematic diagram of chamber structural damage at 10% steel rust.
Detailed Description
The invention will be further described with reference to the accompanying drawings and specific examples.
The total 22 holes of the shallow hole gate engineering of a certain hinge are formed, the net width of each hole is 4.2m, the height is 8.2m, the top surface elevation of the gate bottom plate is 22.49m, the gate pier adopts C25 reinforced concrete, the gate pier is split, the two holes are connected in one, the thickness of the side pier is 0.7m, the thickness of the middle gate pier is 1.0m, and the bottom of the gate pier is provided with a sticking angle. After long-time operation, the concrete carbonization of the grid column of the junction engineering is serious and the corrosion of the steel bars is serious, and the concrete is shown in figure 1.
The calculation is mainly used for nonlinear earthquake motion damage analysis of the medium-hole one-connected brake chamber structure. According to the structural characteristics of the shallow hole gate, a three-dimensional finite element model comprising a foundation, a water body, a gate bottom plate, a gate pier, a steel gate, a highway bridge, an overhaul platform, an upper opening and closing machine room and steel bars is established, wherein the concrete model is shown in the specification of figures 2-10. The foundation unit ranges are respectively extended to 2 times of gate chamber heights up to the upstream, down to the downstream, left bank, right bank and vertically downwards based on the heights of the upper part, the down stream, the left side, the right side and the bottom of the gate bottom plate, wherein the gate chamber height is the difference between the top height of the opening and closing machine room and the bottom height of the gate bottom plate. Meanwhile, in order to facilitate the establishment of a model, the nodes of the upstream and downstream water units are shared with the gate pier and the steel gate node; in the single spring coupling unit method, the normal displacement of the steel bar nodes is calculated according to the following formula, and the concrete formula is as follows:
in the method, in the process of the invention,the displacement value is the displacement value of the ith dimension of the steel bar node under the local coordinate system; n is the model dimension; r is (r) ij Is an interpolation coefficient, namely a coordinate transformation matrix element; u (u) j And the displacement value is the j-th dimension displacement value of the concrete node under the integral coordinate system.
The mechanical parameters of the carbonized concrete adopted in the process are as follows:
f c ＝1.6f c0
E c ＝1.6E c0
ε c ＝0.7ε c0
wherein f c 、E c 、ε c Respectively the compressive strength, the elastic modulus and the ultimate strain of carbonized concrete, f c0 、E c0 、ε c0 The compressive strength, the elastic modulus and the ultimate strain of the completely uncarbonated concrete are respectively shown.
The mechanical properties of the existing non-carbonized concrete are as follows:
wherein E is t 、β d The elastic modulus and the ductility ratio of the existing uncarbonized concrete; e (E) 0 The elastic modulus of the new concrete with the same strength; t is the service life of the existing non-carbonized concrete.
The relation between the mechanical parameters of the rusted steel bars adopted at the time and the rusting rate rho is specifically as follows:
when 0 < ρ% -5%:
f y,c ＝f y0 (1-0.029ρ)
f u,c ＝f u0 (1-0.026ρ)
δ s,c ＝δ s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (1-0.052ρ)
when ρ% > 5%:
f y,c ＝f y0 (1.175-0.064ρ)
f u,c ＝f u0 (1.18-0.062ρ)
δ s,c ＝δ s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (0.895-0.031ρ)
wherein E is u,c ，f y,c ，f u,c ，δ s,c ，ε y,c The nominal elastic modulus, the yield strength, the ultimate strength, the elongation and the ultimate strain of the rusted steel bar are respectively; e (E) u0 ，f y0 ，f u0 ，δ s0 ，ε y0 The elastic modulus, the yield strength, the ultimate strength, the elongation and the ultimate strain of the non-rusted steel bars are respectively.
The bond strength degradation coefficient formula of the post-rust reinforced concrete is as follows:
wherein ρ is the corrosion rate (%) of the steel bar, and β is the reduction coefficient of the bonding strength between the steel bar and the concrete after rust.
In the calculation process, the concrete adopts a four-parameter dynamic damage constitutive model, and the damage criterion is as follows:
wherein: epsilon * Is equivalent strain; A. b, C, D is four test constants, which can be obtained by combining a uniaxial tensile test, a uniaxial compression test, a biaxial isostatic test and a triaxial compression test; i' 1 ＝(ε 1 +ε 2 +ε 3 ) 3 is the first invariant of the strain tensor;is the maximum principal strain; />The second invariant is the strain offset; />J′ 3 ＝ε 1 ε 2 ε 3 The third invariant is the strain offset; epsilon 1 ,ε 2 ,ε 3 The three-way main strain is respectively adopted.
Under the action of earthquake load, the concrete inevitably has unloading and reloading processes of a softening section, and the residual strain calculation in the simulation adopts the following formula:
wherein ε p Is the residual strain value; epsilon 0 ＝f t and/E is the ultimate strain under the tensile strength of the concrete, f t The tensile strength of the concrete is that E is the elastic modulus of the concrete; epsilon un Is the strain value at the unloading point.
The interaction between the steel bar and the concrete is simulated by a single spring coupling unit method based on a mixed coordinate system, wherein the interaction equation between the steel bar and the concrete is that
Wherein Deltau, deltau * And DeltaF, deltaF * Oxyz and O, respectively * x * y * z * Displacement vector increment and load vector increment in a coordinate system; k and k * Oxyz and O, respectively * x * y * z * A stiffness matrix in a coordinate system; k (k) s The method comprises the steps of carrying out a first treatment on the surface of the r is a coordinate transformation matrix; r is (r) T Is the transpose of the coordinate transformation matrix.
The potential fluid unit is adopted to simulate the fluid-solid coupling effect between the front and rear water bodies of the gate and the gate pier and the steel gate under the action of earthquake, and the control equation is as follows:
wherein P represents dynamic water pressure, c represents underwater acoustic wave velocity,for Laplace operator>Is the second derivative of hydrodynamic pressure with time.
The fluid-solid coupling boundary is arranged between the water body and the gate pier, the gate bottom plate and the steel gate, so that the energy transfer between the water body and the steel gate is simulated, and the method is concretely as follows:
wherein n is the external normal direction of the fluid domain on the fluid-solid coupling surface;the absolute acceleration along the normal direction on the fluid-solid coupling surface is represented by ρ, which is the water density.
The front gate and rear gate water levels of the shallow gate medium-hole gate chamber structure under the normal water storage level working condition are shown in table 1.
TABLE 1 shallow bore Gate chamber Structure Gate front and rear Water depth Table
The parameters of the structure materials of the medium-hole gate chamber of the shallow-hole gate are shown in Table 2.
TABLE 2 parameters of concrete materials for shallow hole sluice chamber structure
It should be pointed out that according to the "engineering standard for earthquake resistance of hydraulic construction" (GB 51247-2018), the elastic modulus of concrete material is improved by 50% on the basis of static elastic modulus, the standard value of dynamic compressive strength of concrete is improved by 20% compared with the standard value of static compressive strength, and the standard value of dynamic tensile strength of concrete is 10% of the standard value of dynamic compressive strength. In addition, the water density in the numerical simulation calculation process is 1000kg/m 3 The bulk modulus was 2.3GPa.
As known from the Chinese earthquake motion parameter demarcation graph (GB 18306-2015), the earthquake fortification intensity of the shallow hole gate junction engineering region is VIII DEG, and the characteristic period T of the foundation reaction spectrum of the engineering g Take 0.35s. According to the specification of the engineering standard for earthquake resistance of hydraulic buildings (GB 51247-2018), the horizontal design acceleration representative value alpha of the hollow chamber structure of the shallow-hole gate h =0.1 g. Meanwhile, according to the specification in the "engineering standards for earthquake resistance of Water works construction" (GB 51247-2018) table 4.3.3, the representative value beta of the maximum value of the response spectrum of the sluice structure max Taking 2.25, the sluice should consider the horizontal earthquake action along the river direction and the vertical river direction at the same time.
FIG. 11 is a schematic diagram of a design response spectrum adopted in the calculation, 2 seismic acceleration time courses are generated according to the design response spectrum by adopting a triangle series expansion method, 2 seismic acceleration time course curves are shown in FIGS. 12-13, velocity and displacement time course curves are shown in FIGS. 14-15 and 16-17 respectively, and velocity waves and displacement waves are vertically input from the bottom of a foundation based on viscoelastic artificial boundary conditions in the calculation process.
Based on the material parameters and the load parameters, nonlinear earthquake motion damage analysis is performed on the shallow hole gate chamber structure. In order to analyze the response results of displacement, acceleration, stress, damage distribution and the like under the earthquake action of the reinforced concrete gate chamber structure, a certain number of characteristic points are selected from the shallow hole gate chamber structure, and the positions of the characteristic points are shown in figure 18.
Meanwhile, in the field detection process, the concrete carbonization of the shallow Kong Zha bent column is found to be serious, and the detected carbonization depth reaches 5cm. Considering the most unfavorable working condition, assuming that the concrete is carbonized completely, the influence of the concrete carbonization on the earthquake resistance of the shallow hole gate chamber structure of the vortex and river junction engineering is explored. Figure 19 shows the comparison of the calculation results of the horizontal river displacement at the structural feature point A of the shallow hole sluice chamber under the condition of full carbonization of the concrete and the condition of no carbonization of the concrete. The graph shows that the horizontal river displacement oscillation frequency and the maximum value at the characteristic point A are larger than those of the non-carbonized concrete under the condition of full carbonization of the concrete, and the elastic modulus of the carbonized concrete is improved by 60% compared with that of the non-carbonized concrete.
FIG. 20 shows a comparison of the results of the first principal stress calculation at the structural feature point B of the shallow hole sluice chamber in the case of full concrete carbonization and in the case of no concrete carbonization. It can be seen that under the influence of concrete carbonization, the first principal stress at the characteristic point B starts to deviate to a certain larger extent after 4s under the earthquake action, wherein the calculated result is larger in the case of concrete full carbonization than in the case of non-carbonization, and particularly, the first principal stress at the characteristic point B is obviously increased in the case of concrete full carbonization, namely, 4.86s, 5.58s, 6.31s and 7.74 s.
FIG. 21 shows the comparison of the results of the calculation of the damage at the structural feature point B of the shallow hole gate chamber under the calculation of different methods. It can be seen that the uncarbonated concrete structure starts to be damaged at the position of 3s under the action of earthquake, the damage starts to occur at the position of 4.86s at the characteristic point B under the condition of full carbonization of the concrete, and the time for the damage to occur at the position of the characteristic point B is relatively delayed, mainly because the elastic modulus and the compressive strength of carbonized concrete are improved by 60%, and the dynamic tensile strength of the corresponding concrete is also improved. In addition, according to the comparison of the first principal stress at the characteristic point B, the first principal stress at the characteristic point B is larger than the principal stress peak value for a plurality of times between 4.86 and 7.74s under the condition of full carbonization of the concrete, and the principal stress peak values lead to the continuous accumulation of the damage values of the concrete on one hand and the continuous reduction of the bearing capacity of the concrete at the position on the other hand. Therefore, as the earthquake load continues, the final damage value at the characteristic point B under the condition of fully carbonized concrete is larger than the calculation result under the condition of non-carbonized concrete.
To further highlight the impact of concrete carbonization on the earthquake resistance of the sluice chamber structure, FIGS. 22-23 show the overall damage of the sluice chamber structure at the end of the earthquake. It can be seen that the maximum damage value of the damaged area is obviously larger than the calculation result of the non-carbonized condition, although the damaged area of the lock chamber structure is not obviously changed under the working condition of fully carbonized concrete.
In summary, the elastic modulus of the concrete is increased by carbonization of the concrete under the action of earthquake, so that the overall rigidity of the lock chamber structure is increased, the overall earthquake resistance of the lock chamber structure is gradually reduced along with the increase of carbonization depth, the possibility of earthquake damage to the lock chamber structure is gradually increased, and corresponding treatment measures are adopted in engineering practice to avoid the carbonization phenomenon of the concrete as much as possible.
In order to determine the breaking level of the gate chamber structure under the condition of full carbonization of concrete, according to the overall damage condition of the gate chamber structure at the end stage of the earthquake in fig. 22-23, the ratio of the cross-sectional area of the damaged area of the cross section of the concrete bent frame column of the open-close machine room structure under the condition of full carbonization of concrete at the end of the earthquake is 53%, and the ratio of the cross-sectional area of the damaged area of the cross section of the concrete bent frame column of the open-close machine room structure under the condition of no carbonization of concrete is 36%.
Based on the calculation result and the proposed discrimination standard, the damage level is known to be moderate when the concrete is fully carbonized under the action of the earthquake, and the damage level is known to be general when the concrete is not carbonized. The specific discrimination criteria are as follows:
discriminant criterion
In addition, in the field detection process, the steel bars of the shallow Kong Zha bent frame column are seriously corroded, and the detected corrosion rate reaches 10%. Figure 24 shows the comparison of the calculation results of the horizontal river displacement at the structural feature point A of the shallow hole gate chamber under the condition that 10% of the steel bars are corroded and the steel bars are not corroded. According to the graph, under the action of an earthquake, the calculated results of the 10% steel bar corrosion condition before 10s are basically consistent with the calculated results of the steel bar non-corrosion condition, the calculated results of the 10% steel bar corrosion condition after 10s are larger than the calculated results of the steel bar non-corrosion condition, the calculated results are mainly influenced by the steel bar corrosion, and the gate chamber structure after 10s is damaged to a certain extent, so that the structural displacement of the top bent frame column is larger.
Fig. 25 shows the comparison of the results of the first principal stress calculation at the structural feature point B of the shallow hole gate chamber in the case of 10% steel reinforcement rust and in the case of steel reinforcement non-rust. It can be seen that under the influence of corrosion of the steel bar, the first principal stress at the characteristic point B starts to deviate to a certain extent after 7s under the earthquake action, wherein the calculated result of the corrosion condition of 10% of the steel bar is larger than that of the calculated result of the non-corrosion condition of the steel bar, and particularly, the first principal stress at the characteristic point B is obviously increased under the condition of 10% of the corrosion condition of the steel bar when 8s and 10s are included.
Figure 26 shows the comparison of the damage calculation results at the structural feature point B of the shallow hole gate chamber in the case of 10% steel bar corrosion and in the case of steel bar non-corrosion. It can be seen that under the action of an earthquake, the damage calculation results at the characteristic point B are basically consistent between the corrosion condition of the 10% reinforcing steel bar before 7s and the non-corrosion condition of the reinforcing steel bar, the damage calculation results of the two reinforcing steel bar after 7s begin to deviate to a certain extent, and the damage calculation results of the reinforcing steel bar corrosion condition are gradually larger than the calculation results of the non-corrosion condition of the reinforcing steel bar, mainly because the first principal stress of the two working conditions at 7s, 8s and 10s deviates, and the damage calculation results are different.
In order to further highlight the influence of the corrosion of the steel bars on the earthquake resistance of the sluice chamber structure, the whole damage condition of the sluice chamber structure at the earthquake end stage is shown in the accompanying drawings 27-28, and it can be seen that the damage area of the sluice chamber structure is larger under the condition of 10% corrosion and the maximum damage value is larger than the calculation result of the non-corrosion condition under the influence of the corrosion of the steel bars.
In summary, the steel bar corrosion reduces the mechanical property of the steel bar material and the bonding sliding effect between the steel bar material and the concrete, and under the earthquake effect, the overall earthquake resistance of the lock chamber structure is gradually reduced along with the increase of the steel bar corrosion rate, the possibility of earthquake damage to the lock chamber structure is gradually increased, and the steel bar corrosion phenomenon needs to be avoided as much as possible in engineering practice.
In order to determine the damage level of the gate structure under the condition of 10% corrosion, according to the overall damage condition of the gate structure at the end stage of the earthquake in fig. 27-28, the ratio of the cross section area of the cross section damage area of the concrete bent frame column of the opening and closing machine room structure under the condition of 10% corrosion at the end of the earthquake is 47%, and the ratio of the cross section area of the cross section damage area of the concrete bent frame column of the opening and closing machine room structure under the condition of no corrosion of the steel bars is 36%.
Based on the calculation result, the proposed discrimination criteria are combined, and the damage level is known to be moderate when 10% of the damage is rusted under the action of earthquake, and the damage level is known to be general when the damage is not rusted.
Claims (6)
1. The method for analyzing the earthquake resistance of the aged reinforced concrete sluice structure is characterized by comprising the following steps of:
(1) According to the structural size and reinforcement condition of the existing sluice chamber, a three-dimensional sluice chamber structure finite element model is established, wherein the model comprises a foundation, a water body, a sluice bottom plate, a sluice pier, a steel gate, a highway bridge, an upper opening and closing machine room structure and concrete inner reinforcement;
(2) Based on ADINA finite element analysis, taking into consideration the effects of infinite foundation radiation damping effect, concrete dynamic damage, binding and sliding effect of reinforced concrete, fluid-solid coupling effect of a water body and a sluice structure, concrete carbonization and steel bar corrosion, inputting preset material parameters, boundary conditions and different loads, and carrying out nonlinear earthquake damage calculation on the established model to obtain dynamic responses of all parts of the sluice structure with different concrete carbonization depths and different steel bar corrosion degrees under the action of earthquake load;
(3) And (3) selecting the characteristic points of the area with the maximum displacement, stress and damage values based on the calculation result of the step (2), and drawing the change curves of the displacement, stress and damage values of the characteristic points with different concrete carbonization depths and different steel bar corrosion degrees along with the earthquake duration, wherein the curves take the earthquake duration as the horizontal axis and take the displacement response, stress response or damage values as the vertical axis.
(4) And determining the sectional area occupation ratio of the damaged area according to the change curve of the damage value of the sluice chamber structure along with the earthquake duration under different concrete carbonization depths and different reinforcement corrosion degrees, and judging the damage level of the aged sluice structure according to the sectional area occupation ratio of the damaged area.
2. The method according to claim 1, wherein the foundation unit in the step (1) is based on the upstream, downstream, left, right and bottom elevations of the gate bottom plate, and extends upward, downstream, left, right and vertically downward by 2 times the gate chamber height, wherein the gate chamber height is the difference between the top elevation of the hoist room and the bottom elevation of the gate bottom plate. Meanwhile, in order to facilitate the establishment of a model, the nodes of the upstream and downstream water units are shared with the gate pier and the steel gate node; in the single spring coupling unit method, the normal displacement of the steel bar nodes is calculated according to the following formula, and the concrete formula is as follows:
in the method, in the process of the invention,the displacement value is the displacement value of the ith dimension of the steel bar node under the local coordinate system; n is the model dimension; r is (r) ij Is an interpolation coefficient, namely a coordinate transformation matrix element; u (u) j And the displacement value is the j-th dimension displacement value of the concrete node under the integral coordinate system.
3. The method for analyzing earthquake-resistant performance of an aged reinforced concrete sluice structure according to claim 1, wherein the mechanical parameters of the carbonized concrete in the step (2) are specifically as follows:
f c ＝1.6f c0
E c ＝1.6E c0
ε c ＝0.7ε c0
wherein f c 、E c 、ε c Respectively the compressive strength, the elastic modulus and the ultimate strain of carbonized concrete, f c0 、E c0 、ε c0 Compressive strength, elastic modulus and ultimate strain of the completely uncarbonated concrete respectively;
the mechanical properties of the existing non-carbonized concrete are as follows:
wherein E is t 、β d The elastic modulus and the ductility ratio of the existing uncarbonized concrete; e (E) 0 The elastic modulus of the new concrete with the same strength; t is the service life of the existing non-carbonized concrete;
the carbonization depths were selected from 1cm, 3cm, 5cm, 7cm and all carbonization, and the dynamic response was calculated for finite element models of different carbonization depths.
4. The method for analyzing earthquake-resistant performance of an aged reinforced concrete sluice structure according to claim 1, wherein the relationship between the mechanical parameter of the rusted steel bar and the rusting rate ρ in the step (2) is specifically as follows:
when 0 < ρ% -5%:
f y,c ＝f y0 (1-0.029ρ)
f u,c ＝f u0 (1-0.026ρ)
δ s,c ＝v s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (1-0.052ρ)
when ρ% > 5%:
f y,c ＝f y0 (1.175-0.064ρ)
f u,c ＝f u0 (1.18-0.062ρ)
δ s,c ＝δ s0 (1-0.0575ρ)
ε y,c ＝ε y0 (1-0.0575ρ)
E u,c ＝E u0 (0.895-0.031ρ)
wherein E is u,c ，f y,c ，f u,c ，δ s,c ，ε y,c The nominal elastic modulus, the yield strength, the ultimate strength, the elongation and the ultimate strain of the rusted steel bar are respectively; e (E) u0 ，f y0 ，f u0 ，δ s0 ，ε y0 The elastic modulus, the yield strength, the ultimate strength, the elongation and the ultimate strain of the non-rusted steel bars are respectively;
the bond strength degradation coefficient formula of the post-rust reinforced concrete is as follows:
wherein ρ is the corrosion rate (%) of the steel bar, and β is the reduction coefficient of the bonding strength between the steel bar and the concrete after rust;
the corrosion of the steel bars is selected from 1%, 3%, 5%, 7% and 10%, and the dynamic response is calculated for finite element models of different corrosion rates of the steel bars.
5. The method for analyzing earthquake-resistant performance of an aged reinforced concrete sluice structure according to claim 1, wherein in the step (2), the concrete adopts a four-parameter dynamic damage constitutive model, and the failure criterion is as follows:
wherein: epsilon * Is equivalent strain; A. b, C, D is four test constants, which can be obtained by combining a uniaxial tensile test, a uniaxial compression test, a biaxial isostatic test and a triaxial compression test; i' l ＝(ε 1 +ε 2 +ε 3 ) 3 is the first invariant of the strain tensor;is the maximum principal strain; />The second invariant is the strain offset; />J′ 3 ＝ε 1 ε 2 ε 3 The third invariant is the strain offset; epsilon 1 ,ε 2 ,ε 3 Three-way main strain is respectively adopted; epsilon m Indicating strain under ball stress.
Under the action of earthquake load, the concrete inevitably has unloading and reloading processes of a softening section, and the residual strain calculation in the simulation adopts the following formula:
wherein ε p Is the residual strain value; epsilon 0 ＝f t and/E is the ultimate strain under the tensile strength of the concrete, f t The tensile strength of the concrete is that E is the elastic modulus of the concrete; epsilon un Is the strain value at the unloading point.
The interaction between the steel bar and the concrete is simulated by a single spring coupling unit method based on a mixed coordinate system, wherein the interaction equation between the steel bar and the concrete is that
Wherein Deltau, deltau * And DeltaF, deltaF * Oxyz and O, respectively * x * y * z * Displacement vector increment and load vector increment in a coordinate system; k and k * Oxyz and O, respectively * x * y * z * A stiffness matrix in a coordinate system; k (k) s The method comprises the steps of carrying out a first treatment on the surface of the r is a coordinate transformation matrix; r is (r) T Is the transpose of the coordinate transformation matrix.
The potential fluid unit is adopted to simulate the fluid-solid coupling effect between the front and rear water bodies of the gate and the gate pier and the steel gate under the action of earthquake, and the control equation is as follows:
wherein P represents dynamic water pressure, c represents underwater acoustic wave velocity,for Laplace operator>Is the second derivative of hydrodynamic pressure with time.
The fluid-solid coupling boundary is arranged between the water body and the gate pier, the gate bottom plate and the steel gate, so that the energy transfer between the water body and the steel gate is simulated, and the method is concretely as follows:
wherein n is the external normal direction of the fluid domain on the fluid-solid coupling surface;absolute acceleration along the normal direction on the fluid-solid coupling surface is represented by ρ, which is the water density;
2 seismic acceleration time-course curves are generated by adopting a triangle series expansion method based on a standard design reaction spectrum, and the velocity and displacement time-course curves are generated through integration, wherein velocity waves and displacement waves are vertically input from the bottom of the foundation based on viscoelastic artificial boundary conditions in the calculation process.
6. The method for analyzing earthquake-resistant performance of an aged reinforced concrete sluice structure according to claim 1, wherein in the step (4), different damage levels of the sluice structure are determined by using the sectional area of the concrete damaged area of the sluice structure under the action of earthquake, and specific determination criteria are as follows:
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