CN111324924B - Existing pile supporting and retaining structure service state quantitative evaluation method based on reliability - Google Patents
Existing pile supporting and retaining structure service state quantitative evaluation method based on reliability Download PDFInfo
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Abstract
The invention discloses a reliability-based quantitative evaluation method for service state of an existing pile retaining structure, which comprises the following steps of: s1: establishing a function of the service state of the existing pile retaining structure to be evaluated; s2: according to long-term and real-time monitoring data of the existing pile supporting and retaining structure, statistical analysis is carried out to obtain statistical characteristics of pile body functions; considering material time-varying weakening factors related to pile body concrete carbonization and steel bar corrosion, establishing a time-varying resistance calculation expression of the existing pile retaining structure, and calculating the statistical characteristics of the time-varying resistance; s3: calculating the failure probability and the reliable index of the function according to the statistical characteristics of the pile body action and the statistical characteristics of the time-varying resistance; s4: and obtaining a quantitative evaluation result of the service state of the existing pile retaining structure according to the failure probability and the reliable index of the functional function, and predicting the residual service life of the existing pile retaining structure.
Description
Technical Field
The invention relates to a quantitative evaluation method, in particular to a reliability-based quantitative evaluation method for the service state of an existing pile retaining structure.
Background
The mountain areas of China approximately occupy 2/3 of the land areas, mountain long and large trunks such as the Baochun railway, the Nankun railway, the Neckian railway and the like which are noticed by the world are successively built in China, and the mountain railways play an extremely important role in the economic and social development process as important infrastructures and popular transportation tools in China. At present, a large number of pile retaining structures are involved in the mountain railways and are already in service for decades, and how to evaluate the risk of the service state of the existing pile retaining structures becomes a concern of a railway operation department.
When the reliability-based method is used for quantitative evaluation, because the existing pile retaining structure is constructed, formed and in service, the existing pile retaining structure reliability evaluation method cannot monitor and evaluate the development process of the reliability index of the pile retaining structure along with time.
Disclosure of Invention
The invention aims to: aiming at the problems in the prior art, the method for quantitatively evaluating the service state of the existing pile supporting and retaining structure based on the reliability is provided, the time-varying weakening effect of the material after long-term service is considered, and the prediction of the residual service life is realized.
In order to achieve the purpose, the invention adopts the technical scheme that:
a reliability-based existing pile supporting structure service state quantitative evaluation method comprises the following steps:
s1: establishing a function of the service state of the existing pile retaining structure to be evaluated;
s2: according to long-term and real-time monitoring data of the existing pile supporting and retaining structure, statistical analysis is carried out to obtain statistical characteristics of pile body functions; considering material time-varying weakening factors related to pile body concrete carbonization and steel bar corrosion, establishing a time-varying resistance calculation expression of the existing pile retaining structure, and calculating the statistical characteristics of the time-varying resistance;
s3: calculating the failure probability and the reliable index of the function according to the statistical characteristics of the pile body action and the statistical characteristics of the time-varying resistance;
s4: and obtaining a quantitative evaluation result of the service state of the existing pile retaining structure according to the failure probability and the reliable index of the functional function, and predicting the residual service life of the existing pile retaining structure.
As a preferable embodiment of the present invention, in step S1, the function z (t) of the service state of the existing pile retaining structure is:
Z(t)＝g[R(t)，S(t)]＝R(t)-S(t)；
in the formula, R (t) is a random resistance process of the pile retaining structure, and changes along with the time-varying effect of the material performance after the structure is in service for a long time; s (t) is a random process of the load effect of the pile retaining structure, changes along with the natural environment and the state of slope rock soil, and t is time.
As a preferable scheme of the present invention, the acquiring of the statistical characteristics of the pile body function in step S2 includes:
a21: drilling holes in front of and behind the existing pile retaining structure to be evaluated, burying soil pressure monitoring equipment, and monitoring active soil pressure behind the pile and passive soil pressure in front of the pile for a long time in real time;
a22: and D, introducing the long-term and real-time monitoring data in the step A21, and performing statistical analysis to obtain the statistical characteristics of the pile body action.
As a preferable embodiment of the present invention, the step a22 includes:
a221: determining a data time period T used for evaluation, calculating the group number n as T/T +1, and introducing n groups of monitoring data of the pile body soil pressure obtained by each soil pressure monitoring device in the step A21 in the time period T;
a222: establishing a database by using the passive soil pressure monitoring data before the pile in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; obtaining a compressive stress distribution map of rock and soil in front of the pile according to each group of monitoring data, and obtaining the maximum compressive stress of rock and soil in front of the pile;
establishing a database by using the post-pile active soil pressure monitoring data in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; accumulating and summing each group of monitoring data along the direction of the pile body to obtain the post-pile active soil pressure corresponding to the group of data; introducing an elastic foundation beam model, and calculating the maximum bending moment action and the maximum shearing force action of the pile body corresponding to the group of data;
a223: performing statistical analysis on the maximum compressive stress of the n pre-pile rock-soil within the T time period obtained in the step A222 to obtain statistical characteristics of the pre-pile rock-soil action;
and B, performing statistical analysis on the maximum bending moment action and the maximum shearing force action of the n groups of pile bodies in the T time period obtained in the step A222 to obtain the statistical characteristics of the action of rock and soil behind the pile.
As a preferred aspect of the present invention, the statistical characteristics of the time-varying resistance calculated in step S2 include:
b21: determining the statistical characteristics of the pile resistance design parameters according to the specifications and design data, wherein the statistical characteristics comprise the material strength parameter statistical characteristics of pile concrete and reinforcing steel bars and the geometrical parameter statistical characteristics of piles;
b22: considering material weakening factors related to pile body concrete carbonization and steel bar corrosion, and acquiring statistical characteristics of material weakening strength of the existing pile retaining structure within service life;
b23: and establishing a time-varying resistance calculation expression according to a design resistance calculation formula of the functional function, and calculating the statistical characteristics of the time-varying resistance in the functional function.
As a preferred scheme of the present invention, in step B21, the statistical characteristics of the material strength parameters of the pile body concrete and the steel bar include axial compressive strength of the concrete, tensile strength of the concrete, elastic modulus of the concrete, and tensile strength of the steel bar; the statistical characteristics of the geometrical parameters of the pile comprise the width of the section of the pile and the height of the section of the pile;
the step B22 includes:
b221: classifying resistance related parameters into geometric parameters and material parameters, considering the statistical characteristics of the time-varying influence of the material parameters, and adopting the statistical characteristics of design parameters for the geometric parameters;
b222: considering the influence of time varying of pile body concrete carbonization, calculating the statistical characteristics of the time varying strength of the concrete, wherein the calculation formula comprises the following steps:
μf(t)＝η(t)μf0wherein
σf(t)＝ξ(t)σf0Where ξ (t) ═ 0.0305t + 1.2368;
in the formula, muf(t)、σf(t) -mean and standard deviation, μ, of concrete at time tf0、σf0-average and standard deviation of the 28-day intensity of the concrete, η (t), ξ (t) -function of the average and standard deviation of the intensity of the concrete as a function of time t;
b223: and judging the corrosion stage according to the service time of the pile by calculating time nodes of three stages in the steel bar corrosion process, and calculating the statistical characteristic of the time-varying strength of the steel bar according to the judgment whether the time-varying effect generated by the corrosion of the steel bar is considered.
As a preferable embodiment of the present invention, the step B23 includes:
b231: the design resistance calculation expression of the arrangement pile supporting and retaining structure comprises the following calculation formula:
bending moment resistance (kN · m):
shear resistance (kN):
in the formula (f)yu-normal rebar tensile strength normalized value (MPa); a. thesLongitudinal tension bar cross-sectional area (m)2)；fcu-concrete axial compressive strength standard value; f. oftu-a concrete axial tensile strength standard value (MPa); b. h is a total of0-a cross-sectional width (m), an effective height (m); f. ofyvu-stirrup tensile strength limit (MPa); a. thesvStirrup cross-sectional area (m)2) (ii) a S-stirrup spacing (m); alpha is alpha1-a coefficient;
rock compressive stress resistance (kPa): sigmaH＝σb-σa(soil mass);
σH＝KHRc(rock mass);
in the formula: sigmaa-active earth compressive stress (kPa); sigmab-passive earth compressive stress (kPa); kH-a horizontal scaling factor; rc-uniaxial compressive ultimate strength (kPa) of rock;
b232: establishing a time-varying resistance calculation expression according to the design resistance calculation expression, wherein the general formula of the time-varying resistance calculation expression is as follows:
R(t)＝KP·f[f1(t)，f2(t)，...，fn(t)，a1，...，am]；
where R ═ f (g) -design resistance calculation function, KP-calculating a model uncertainty factor, fn(t) -standard values of the relevant material parameters taking into account the time-varying influence, am-standard values of the relevant geometrical parameters;
the structural time-varying resistance calculation expression is as follows:
moment-variation resistance (kN · m):
shear time-variation resistance (kN):
in the formula, Kp-M-a bending moment calculation model uncertainty factor; k isp-Q-a shear force calculation model uncertainty coefficient; f. ofyThe tensile strength (MPa) of the common steel bar at the (t) -t moment; a. thes(t) -t time the sectional area (m) of the longitudinal tension bar2)；fc(t) -t moment concrete axial compressive strength (MPa); f. oft(t) -t moment concrete axial tensile strength (MPa); b. h is0-a cross-sectional width (m), an effective height (m); f. ofyvThe tension strength (MPa) of the stirrup at the time (t) -t; a. thesvSection area (m) of stirrup at time (t) -t2) (ii) a S-stirrup spacing (m);
b233: calculating the time-varying resistance R in the function by adopting an error transfer method or a Monte Carlo method according to the calculation conditionstThe statistical characteristics of (1).
As a preferred embodiment of the present invention, the step B223 includes:
b2231: calculating the preliminary corrosion time of the steel bar, wherein the calculation formula comprises the following steps:
preliminary rusting time (a) of the steel bar:
wherein, c-the thickness (mm) of the concrete protective layer, x0Residual carbonization amount (mm), kc-concrete carbonation coefficient;
coefficient of carbonization
Wherein, K1，K2，K3Concrete area, outdoor, maintenance impact coefficient, fcuk-concrete cube compressive strength normalized value (MPa);
residual quantity of carbonization x0＝4.86(-RH2+1.5RH-0.45)(c-5)(ln fcuk-2.30), RH ambient relative humidity (%);
b2232: calculate the exact occurrence of the reinforcementDepth of rust-up delta in case of rust-up of protective layercr(mm), the calculation formula of which includes:
in the case of a round steel bar,
for the stirrups and the mesh-like reinforcing bars,
in the formula, Kcrs-the factor of influence of the position of the reinforcement, d-the diameter of the reinforcement (mm), fcu-concrete cubic compressive strength (MPa);
b2233: calculating the rust swelling time of the steel bar protective layer, and judging whether the protective layer is rusted and cracked, wherein the calculation formula comprises the following steps:
rust speed (mm/a) before rust cracking of the protective layer:
protective layer rust cracking time (a): t is tcr＝δcr/λe1；
In the formula, Kcr-a reinforcement position correction factor, Kce-a small ambient condition correction factor;
b2234: preliminary rust and protective layer rust time t calculated by step B2231 and step B2233c、tcr(a) Judging the corrosion stage according to the service time t (a) of the pile, and if the pile is in the non-corrosion stage, not considering the corrosion time-varying effect of the steel bars;
b2235: according to the judgment result of the step S2234, if corrosion occurs, a corrosion depth calculation formula is selected according to the stage, and the calculation formula includes:
rust depth (mm) before rust swelling of protective layer: deltae1(t)＝λe1(t-tc)；
Rust depth (mm) after rust swelling of the protective layer:
b2236: calculating the corrosion rate eta of the reinforcing steel bars(t) the calculation formula includes:
in the formula, deltae(t) -the depth of corrosion of the steel bar, d-the diameter of the steel bar;
the calculation of the mean value and the standard deviation meets the general formula of statistical analysis: e (aX) ═ ae (x), σ (aX) ═ a2σ(X)；
B2237: calculating the statistical characteristics of the corrosion section area of the steel bar, wherein the calculation formula comprises the following steps:
As(t)＝As[1-ηs(t)]；
in the formula, As(t) -t time the sectional area (m) of the longitudinal tension bar2)，AsLongitudinal tension bar cross-sectional area (m)2)，ηs(t) -corrosion rate of steel reinforcement;
the calculation of the mean value and the standard deviation meets the general formula of statistical analysis: e (aX) ═ ae (x), σ (aX) ═ a2σ(X)；
B2238: calculating the statistical characteristics of the corrosion strength of the steel bars, wherein the calculation formula comprises the following steps:
corrosion bar time-varying strength (MPa):
in the formula (f)yu-standard value of tensile strength (MPa) for ordinary steel bars.
As a preferred embodiment of the present invention, in step S3, JC method or monte carlo method is adopted to calculate the failure probability and reliability index.
As a preferable embodiment of the present invention, the step S4 includes:
c41: determining the failure probability grade of the evaluation structure according to the failure probability and the probability grade standard obtained by calculation;
c42: determining the economic loss grade and the casualty grade of the pile structure after failure according to the economic loss grade standard and the casualty grade standard, and further determining the comprehensive consequence grade after failure;
c43: and determining the risk level of the existing pile structure according to the probability level and the consequence level, and giving corresponding countermeasures.
As a preferable embodiment of the present invention, the step S4 includes:
d41: according to the current stage t1Monitoring the action effect at the moment, if the irresistance does not occur, the action effect does not change greatly along with the time, and then t in the futurenTime of day effect S (t)n) Is the same as S (t)1) The same;
d42: according to the long-term service state function of the existing pile retaining structure, P is satisfied at the end of the service lifef＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]Wherein [ Pf]Is an acceptable value for the probability of failure, R (t)n) -retaining structure tnMoment resistance, S (t)1) -retaining structure t1A time of day effect;
d43: using a trial algorithm, a t is givenn＞t1Calculating tnThe statistical characteristics of the time-varying resistance and whether P is satisfied are judgedf＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]If not, increasing tnRecalculating until a critical point satisfying the formula is found;
d44: the time t finally calculated on the basis of the step D43nThen t isn-t1Namely the residual service life of the existing pile supporting and retaining structure.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
the invention provides a quantitative evaluation method of an existing pile retaining structure considering a time-varying weakening effect of a material, which can acquire a rock-soil action effect in real time through monitoring and acquire a resistance time-varying effect of a pile by considering a material time-varying weakening factor, and provides a quantitative evaluation functional general formula of a long-term service state of the existing pile retaining structure: z (t) ═ g [ r (t), s (t) ═ r (t) -s (t). The method can monitor and evaluate the development process of the reliable indexes along with time, quantitatively evaluate the real-time service state of the existing pile retaining structure, ensure that the evaluation result is more reliable, and predict the residual life of the existing pile structure.
Drawings
Fig. 1 is a flowchart of a reliability-based quantitative evaluation method for service states of existing pile retaining structures according to the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
As shown in fig. 1, a reliability-based quantitative evaluation method for service state of an existing pile retaining structure includes the following steps:
s1: and establishing a function (bending resistance, shearing resistance, pre-pile rock-soil compression resistance and the like) of the service state of the existing pile supporting and retaining structure to be evaluated.
In the step S1, the function z (t) of the service state of the existing pile retaining structure is as follows:
Z(t)＝g[R(t)，S(t)]＝R(t)-S(t)
in the formula, R (t) -pile type retaining structure resistance random process, which changes along with time-varying effect of material performance after the structure is in service for a long time; s (t) -the random process of the load effect of the pile retaining structure changes along with the natural environment and the state of slope rock soil, and t is time.
S2: drilling holes in front of and behind the existing pile retaining structure to be evaluated, burying soil pressure monitoring equipment, and monitoring active soil pressure behind the pile and passive soil pressure in front of the pile for a long time in real time.
S3: and (4) introducing the long-term and real-time monitoring data in the step S2, and carrying out statistical analysis to obtain statistical characteristics (mean, variance and probability distribution) of pile body effects (compressive stress of rock soil in front of the pile, internal force of the structure and the like).
The step S3 specifically includes the following steps:
s31: determining a data time period T used for evaluation, calculating the group number n as T/T +1, and introducing n groups of monitoring data of the pile body soil pressure obtained by each soil pressure monitoring device in the step S2 in the time period T;
s32: establishing a database by using the passive soil pressure monitoring data before the pile in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; obtaining a compressive stress distribution map of the rock soil in front of the pile according to each group of monitoring data, and obtaining the maximum compressive stress of the rock soil in front of the pile;
s33: performing statistical analysis on the maximum compressive stress of the rock and soil in front of the n piles within the T time period obtained in the step S32 to obtain statistical characteristics of the rock and soil action in front of the piles;
s34: establishing a database by using the active soil pressure monitoring data behind the pile in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; accumulating and summing each group of monitoring data along the direction of the pile body to obtain the post-pile active soil pressure corresponding to the group of data; introducing an elastic foundation beam model, and calculating the maximum bending moment action and the maximum shearing force action of the pile body corresponding to the group of data;
s35: performing statistical analysis on the maximum bending moment effect and the maximum shearing force effect of the n groups of pile bodies in the T time period obtained in the step S34 to obtain the statistical characteristics of the post-pile rock-soil effect;
s4: determining the statistical characteristics of the design parameters of the pile body resistance according to the specifications and the design data, wherein the statistical characteristics comprise the statistical characteristics of the strength parameters of materials such as pile body concrete, reinforcing steel bars and the like (the compressive strength of the axis of the concrete, the tensile strength of the concrete, the elastic modulus of the concrete and the tensile strength of the reinforcing steel bars), and the statistical characteristics of the geometrical parameters of the pile (the width of the section of the pile and the height of the section of the pile);
s5: considering time-related material weakening factors such as pile body concrete carbonization and steel bar corrosion, and obtaining the statistical characteristics of the material weakening strength of the existing pile retaining structure within the service life;
the step S5 specifically includes the following steps:
s51: classifying resistance related parameters into geometric parameters and material parameters, considering the statistical characteristics of the time-varying influence of the material parameters, and adopting the statistical characteristics of design parameters for the geometric parameters;
s52: considering the influence of the time varying of the concrete carbonization of the pile body, calculating the statistical characteristics of the time varying strength of the concrete, wherein the calculation formula comprises the following steps:
μf(t)＝η(t)μf0wherein
σf(t)＝ξ(t)σf0Wherein xi (t) ═ 0.0305t +1.2368
In the formula, muf(t)、σf(t) -mean and standard deviation, μ, of concrete at time tf0、σf0-average and standard deviation of the 28-day intensity of the concrete, η (t), ξ (t) -function of the average and standard deviation of the intensity of the concrete as a function of time t;
s53: the steel bar corrosion process comprises a non-corrosion stage, a preliminary corrosion stage and a protective layer rust expansion cracking stage. Through calculating the time node of three stages of the corrosion process, judge the corrosion stage according to this stake service time to whether take into account the time-varying effect that the reinforcing bar corrosion produced with this judgement, calculate the statistical character of reinforcing bar time-varying intensity, its concrete process includes:
s531: calculating the preliminary corrosion time of the steel bar, wherein the calculation formula comprises the following steps:
preliminary rusting time (a) of the steel bar:
wherein, c-the thickness (mm) of the concrete protective layer, x0Residual carbonization amount (mm), kc-concrete carbonation coefficient;
coefficient of carbonization
Wherein, K1，K2，K3Concrete area, outdoor, maintenance influence factor, K1(southern 1.5), K2(generally 1.0) and K3(generally 1.5), fcuk-concrete cube compressive strength normalized value (MPa);
residual quantity of carbonization x0＝4.86(-RH2+1.5RH-0.45)(c-5)(ln fcuk-2.30), RH-ambient relative humidity (%).
S532: calculating the rust expansion depth delta of the steel bar when the rust expansion of the protective layer happenscr(mm), the calculation formula of which includes:
in the formula, Kcrs-the steel bar position influence factor, angular 1.0, non-angular 1.35, d-steel bar diameter (mm), fcuConcrete cubic compressive strength (MPa).
S533: calculating the rust swelling time of the steel bar protective layer, and judging whether the protective layer is rusted and cracked, wherein the calculation formula comprises the following steps:
rust speed (mm/a) before rust cracking of the protective layer:
protective layer rust cracking time (a): t is tcr＝δcr/λe1；
In the formula, KcrThe reinforcement position correction factor, corner steel 1.6, middle reinforcement 1.0, Kce-small ambient condition correction factor, suggesting: the outdoor environment of the wet area is 3.0-4.0, the indoor environment of the wet area is 1.0-1.5, the outdoor environment of the dry area is 2.5-3.5, and the indoor environment of the dry area is 1.0.
S534: preliminary rust sum calculated by step S531 and step S533Rust-swelling time t of protective layerc、tcr(a) Judging the corrosion stage according to the service time t (a) of the pile, and if the pile is in the non-corrosion stage, not considering the corrosion time-varying effect of the steel bars;
s535: according to the judgment result of the step S534, if corrosion occurs, a corrosion depth calculation formula is selected according to the stage, and the calculation formula includes:
rust depth (mm) before rust swelling of protective layer: deltae1(t)＝λe1(t-tc)
Rust depth (mm) after rust swelling of the protective layer:
s536: calculating the corrosion rate eta of the reinforcing steel bars(t) the calculation formula includes:
in the formula, deltae(t) -the depth of corrosion of the steel bar and d-the diameter of the steel bar.
The calculation of the mean value and the standard deviation meets the general formula of statistical analysis: e (aX) ═ ae (x), σ (aX) ═ a2σ(X)。
S537: calculating the statistical characteristics of the corrosion section area of the steel bar, wherein the calculation formula comprises the following steps:
As(t)＝As[1-ηs(t)]
in the formula, As(t) -t time the sectional area (m) of the longitudinal tension bar2)，AsLongitudinal tension bar cross-sectional area (m)2)，ηs(t) -corrosion rate of steel bars.
The calculation of the mean value and the standard deviation meets the general formula of statistical analysis: e (aX) ═ ae (x), σ (aX) ═ a2σ(X)
S538: calculating the statistical characteristics of the corrosion strength of the steel bars, wherein the calculation formula comprises the following steps:
corrosion bar time-varying strength (MPa):
in the formula (f)yu-standard value of tensile strength (MPa) for ordinary steel bars.
S6: establishing a time-varying resistance calculation expression according to a design resistance calculation formula of the functional functions, and calculating the statistical characteristics of the time-varying resistance in each functional function by adopting an error transfer method or a Monte Carlo sampling method;
the step S6 specifically includes the following steps:
s61: the design resistance calculation expression of the arrangement pile supporting and retaining structure comprises the following calculation formula:
bending moment resistance (kN · m):
shear resistance (kN):
in the formula (f)yu-normal rebar tensile strength normalized value (MPa); a. thesLongitudinal tendon section area (m)2)；fcu-concrete axial compressive strength standard value; f. oftu-a concrete axial tensile strength standard value (MPa); b. h is0-a cross-sectional width (m), an effective height (m); f. ofyvu-stirrup tensile strength limit (MPa); a. thesvStirrup cross-sectional area (m)2) (ii) a S-stirrup spacing (m); alpha (alpha) ("alpha")1The coefficients, generally taken to be 1.
Rock compressive stress resistance (kPa): sigmaH＝σb-σa(soil body)
σH＝KHRc(rock mass);
in the formula: sigmaa-active earth compressive stress (kPa); sigmab-passive earth compressive stress (kPa); kH-a horizontal scaling factor; rc-uniaxial compressive ultimate strength (kPa) of rock.
S62: establishing a time-varying resistance calculation expression according to the design resistance calculation expression, wherein the general formula of the time-varying resistance calculation expression is as follows:
R(t)＝KP·f[f1(t)，f2(t)，...，fn(t)，a1，...，am]
where R ═ f (g) -design resistance calculation function, KP-calculating a model uncertainty factor, fn(t) -standard values of the relevant material parameters taking into account the time-varying influence, am-standard values of the relevant geometrical parameters;
the structural time-varying resistance calculation expression is as follows:
bending moment resistance (kN · m):
shear time-variation resistance (kN):
in the formula Kp-M-a bending moment calculation model uncertainty factor; kp-Q-a shear force calculation model uncertainty coefficient; f. ofyThe tensile strength (MPa) of the common steel bar at the (t) -t moment; a. thes(t) -t time the sectional area (m) of the longitudinal tension bar2)；fc(t) -t moment concrete axial compressive strength (MPa); f. oft(t) -t moment concrete axial tensile strength (MPa); b. h is0-a cross-sectional width (m), an effective height (m); f. ofyvThe tension strength (MPa) of the stirrup at the time (t) -t; a. thesvArea of stirrup cross-section at time (t) -t (m)2) (ii) a S-stirrup spacing (m).
S63: calculating the time-varying resistance R in each function from either one of the steps S64 or S65 according to the calculation conditiontThe statistical characteristics of (1);
s64: the adopted error transmission method comprises the following steps of calculating a general formula:
and (3) mean value calculation: mu.sR(t)≈f(μf1(t)，μf2(t)，...，μfn(t)，μa1，...，μam)
And (3) variance calculation:
in the formula, mufn(t)、σfn(t)Mean and standard deviation, μ, of the relevant material parameters taking into account the time-varying influenceam、σam-mean and standard deviation of the relevant geometric parameter.
S65: the Monte Carlo method is adopted, and the method specifically comprises the following steps:
s651: sampling for the first time according to the time-varying statistical characteristics of the material parameters and the statistical characteristics of the geometric parameters, and substituting the time-varying resistance expression to obtain a group of sample values of the time-varying resistance;
s652: and determining the sampling times according to the required calculation precision and the parameter characteristics, repeating the step S651 for sampling for multiple times to obtain sample values of different time-varying resistance, and performing statistical analysis to obtain the statistical characteristics of the group of resistance.
S653: repeating the steps S651-S652, and calculating all the time-varying resistance statistical characteristics such as bending resistance, shearing resistance, pre-pile rock-soil pressure resistance and the like;
s7: calculating the failure probability and the reliable index of the functional function by a JC method or a Monte Carlo sampling method according to the time-varying resistance and the action statistical characteristics of the functional function;
the step S7 specifically includes the following steps:
s71: the statistical characteristics of the effect and the time-varying resistance are obtained in steps S3 and S6, and the failure probability P is calculated from either one of steps S72 or S73 according to the calculation condition of the function z (t) ═ r (t) -S (t) ((t))fAnd a reliability index beta;
s72: adopting JC method to calculate reliable indexes, the method comprises the following steps:
s721: if the time-varying resistance and the action are distributed abnormally, performing equivalent normalization firstly;
s722: and calculating the reliability index by the following calculation formula:
in the formula, muR、μSIs the mean value, σ, of R (t), S (t), respectivelyR、σSAre respectively R (t),Standard deviation of S (t).
S73: adopting a Monte Carlo method to calculate failure probability and reliable indexes, and specifically comprising the following steps:
s731: sampling for the first time according to the statistical characteristics of the time-varying resistance and the action to obtain a group of sample values of the time-varying resistance and the action and judge the structural state, wherein Z is less than 0, Z is more than 0, and Z is 0 to respectively represent structural failure, reliability and limit state;
s732: determining the sampling times according to the required calculation precision, repeating the step S731, sampling the time-varying resistance and the action for multiple times to obtain different structural states, performing statistical analysis to obtain the structural failure probability P under multiple samplesf。
S733: and further calculating a reliability index according to the calculated failure probability:
β＝Φ-1(1-Pf)
s734: repeating the steps S731 to S733, and calculating reliable indexes of all function functions such as bending moment, shearing force, pre-pile rock-soil pressure and the like;
s74: and quantitatively evaluating the instant service state of the existing pile retaining structure to be evaluated according to the failure probability and the reliable index of each functional function.
S8: obtaining a quantitative evaluation result of the service state of the existing pile retaining structure according to the failure probability and the reliable index of the functional function;
the step S8 specifically includes the following steps:
s81: determining a failure probability level of the evaluation structure based on the failure probability calculated at step S7 and the probability level criteria (table S81);
TABLE S81 probability rating standards
| Range of probability | Center value | Description of probability classes | Probability level |
| ＞0.3 | 1 | Is likely to be | 5 |
| 0.03-0.3 | 0.1 | Can make it possible to | 4 |
| 0.003-0.03 | 0.01 | By chance | 3 |
| 0.0003-0.003 | 0.001 | It is impossible to use | 2 |
| ＜0.0003 | 0.0001 | Is very unlikely to | 1 |
Wherein, when the probability value is difficult to obtain, the probability can be replaced by the frequency; the central value represents the logarithmic mean of the given interval, meaning that the upper limit is included and the lower limit is not included, as is the case in the tables below.
S82: determining the economic loss grade and the casualty grade of the pile structure after failure according to the economic loss grade standard (table S82-1) and the casualty grade standard (table S82-2), and further determining the comprehensive consequence grade after failure;
TABLE S82-1 economic loss rating Standard
| Qualitative description of consequences | Catastrophic of | Is very serious | Severe (severe) | Is bigger | Is slight |
| Grade of consequence | 5 | 4 | 3 | 2 | 1 |
| Economic loss (Wanyuan) | ＞1000 | 300-1000 | 100-300 | 30-100 | ＜30 |
TABLE S82-2 casualty grade standards
In the table, F is the number of dead, SI is the number of severe injury, and MI is the number of mild injury.
S83: determining the risk level of the existing pile structure according to the probability level and the consequence level (Table S83-1), and finally giving corresponding countermeasures (Table S83-2);
TABLE S83-1 Risk rating standards
TABLE S83-2 Risk acceptance criteria and measures
S9: and predicting the residual service life of the existing pile structure according to the long-term service state function.
The step S9 specifically includes the following steps:
s91: according to the current stage t1Monitoring the action effect at the moment, if the ineffectiveness such as earthquake, landslide and continuous heavy rainfall does not occur, the action effect does not change greatly along with the time, and then t is measured in the futurenTime of day effect S (t)n) Is the same as S (t)1) The same;
s92: according to the long-term service state function of the existing pile retaining structure, P is satisfied at the end of the service lifef＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]Wherein [ Pf]Is an acceptable value of failure probability, and can be taken as 0.3, R (t) according to the probability level standardn) Is a supporting structure tnMoment resistance, S (t)n) Is a supporting structure tnEffect of time of day, S (t)1) Is a supporting structure t1A time of day effect;
s93: using a trial algorithm, a t is givenn＞t1Substituting into steps S5 and S6 to calculate tnThe statistical characteristics of the time-varying resistance and whether P is satisfied are judgedf＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]If not, increasing tnRecalculating until a critical point satisfying the formula is found;
s94: step S93 finally calculates time tnThen t isn-t1Namely the residual service life of the existing pile supporting and retaining structure.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A reliability-based existing pile supporting structure service state quantitative evaluation method is characterized by comprising the following steps:
s1: establishing a function of the service state of the existing pile retaining structure to be evaluated;
s2: according to long-term and real-time monitoring data of the existing pile supporting and retaining structure, statistical analysis is carried out to obtain statistical characteristics of pile body functions;
the statistical characteristics of the pile body effect are acquired by the following steps:
a21: drilling holes in front of and behind the existing pile retaining structure to be evaluated, burying soil pressure monitoring equipment, and monitoring active soil pressure behind the pile and passive soil pressure in front of the pile for a long time in real time;
a22: introducing the long-term and real-time monitoring data in the step A21, and carrying out statistical analysis to obtain the statistical characteristics of the pile body action; the step A22 includes: a221: determining a data time period T used for evaluation, calculating the group number n as T/T +1, and introducing n groups of monitoring data of the pile body soil pressure obtained by each soil pressure monitoring device in the step A21 in the time period T; a222: establishing a database by using the passive soil pressure monitoring data before the pile in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; obtaining a compressive stress distribution map of the rock soil in front of the pile according to each group of monitoring data, and obtaining the maximum compressive stress of the rock soil in front of the pile; establishing a database by using the post-pile active soil pressure monitoring data in the T time period, wherein n monitoring time points in the T time period correspond to n groups of monitoring data; accumulating and summing each group of monitoring data along the direction of the pile body to obtain the post-pile active soil pressure corresponding to the group of data; introducing an elastic foundation beam model, and calculating the maximum bending moment action and the maximum shearing force action of the pile body corresponding to the group of data; a223: performing statistical analysis on the maximum compressive stress of the rock and soil in front of the n piles within the T time period obtained in the step A222 to obtain statistical characteristics of the rock and soil action in front of the piles; performing statistical analysis on the maximum bending moment effect and the maximum shearing force effect of the n groups of pile bodies in the T time period obtained in the step A222 to obtain the statistical characteristics of the post-pile rock-soil effect;
considering material time-varying weakening factors related to pile body concrete carbonization and steel bar corrosion, establishing a time-varying resistance calculation expression of the existing pile retaining structure, and calculating the statistical characteristics of the time-varying resistance;
the statistical characteristics of the time-varying resistance are calculated as follows:
b21: determining the statistical characteristics of the pile resistance design parameters according to the specifications and design data, wherein the statistical characteristics comprise the material strength parameter statistical characteristics of pile concrete and reinforcing steel bars and the geometrical parameter statistical characteristics of piles; the statistical characteristics of the material strength parameters of the pile body concrete and the reinforcing steel bar comprise the axial compressive strength of the concrete, the tensile strength of the concrete, the elastic modulus of the concrete and the tensile strength of the reinforcing steel bar; the statistical characteristics of the geometrical parameters of the pile comprise the width of the section of the pile and the height of the section of the pile;
b22: considering material weakening factors related to pile body concrete carbonization and steel bar corrosion, and acquiring statistical characteristics of material weakening strength of the existing pile retaining structure within service life; the step B22 includes: b221: classifying resistance related parameters into geometric parameters and material parameters, considering the statistical characteristics of the time-varying influence of the material parameters, and adopting the statistical characteristics of design parameters for the geometric parameters; b222: considering the influence of time varying of pile body concrete carbonization, calculating the statistical characteristics of the time varying strength of the concrete; b223: by calculating time nodes of three stages of the steel bar corrosion process, judging a corrosion stage according to the service time of the pile, judging whether a time-varying effect generated by the steel bar corrosion is considered or not according to the corrosion stage, and calculating statistical characteristics of the time-varying strength of the steel bar;
b23: establishing a time varying resistance calculation expression according to a design resistance calculation formula of the functional function, and calculating the statistical characteristics of the time varying resistance in the functional function;
s3: calculating the failure probability and the reliable index of the function according to the statistical characteristics of the pile body action and the statistical characteristics of the time-varying resistance;
s4: and obtaining a quantitative evaluation result of the service state of the existing pile retaining structure according to the failure probability and the reliable index of the functional function, and predicting the residual service life of the existing pile retaining structure.
2. The method for quantitatively evaluating the service state of the existing pile-type retaining structure based on the reliability of claim 1, wherein in the step S1, the function z (t) of the service state of the existing pile-type retaining structure is:
Z(t)＝g[R(t)，S(t)]＝R(t)-S(t)；
in the formula, R (t) is a random resistance process of the pile retaining structure, and changes along with the time-varying effect of the material performance after the structure is in service for a long time; s (t) is a random process of the load effect of the pile retaining structure, changes along with the natural environment and the state of slope rock soil, and t is time.
3. The reliability-based quantitative evaluation method for the service state of the existing pile retaining structure according to claim 1,
the step B23 includes:
b231: the design resistance calculation expression of the arrangement pile supporting and retaining structure comprises the following calculation formula:
bending moment resistance (kN · m):
shear resistance (kN):
in the formula (f)yu-normal rebar tensile strength normalized value (MPa); a. thesLongitudinal tension bar cross-sectional area (m)2)；fcu-concrete axial compressive strength standard value; f. oftu-a concrete axial tensile strength standard value (MPa); b. h is0-a cross-sectional width (m), an effective height (m); f. ofyvu-stirrup tensile strength limit (MPa); a. thesvStirrup cross-sectional area (m)2) (ii) a S-stirrup spacing (m); alpha is alpha1-a coefficient;
rock compressive stress resistance (kPa): sigmaH＝σb-σaSoil mass;
σH＝KHRca rock mass;
in the formula: sigmaa-active earth compressive stress (kPa); sigmab-passive earth compressive stress (kPa); kH-a horizontal scaling factor; rc-uniaxial compressive ultimate strength (kPa) of rock;
b232: establishing a time-varying resistance calculation expression according to the design resistance calculation expression, wherein the general formula of the time-varying resistance calculation expression is as follows:
R(t)＝KP·f[f1(t)，f2(t)，...，fn(t)，a1，...，am]；
where R ═ f (g) -design resistance calculation function, KP-calculating a model uncertainty factor, fn(t) -standard values of the relevant material parameters taking into account the time-varying influence, am-standard values of the relevant geometrical parameters;
the structural time-varying resistance calculation expression is as follows:
moment-variation resistance (kN · m):
shear time-variation resistance (kN):
in the formula, Kp-M-a bending moment calculation model uncertainty factor; kp-Q-a shear force calculation model uncertainty coefficient; f. ofyThe tensile strength (MPa) of the common steel bar at the (t) -t moment; a. thes(t) -t time the sectional area (m) of the longitudinal tension bar2)；fc(t) -t moment concrete axial compressive strength (MPa); f. oft(t) -t moment concrete axial tensile strength (MPa); b. h is0-a cross-sectional width (m), an effective height (m); f. ofyvThe tension strength (MPa) of the stirrup at the time (t) -t; a. thesvSection area (m) of stirrup at time (t) -t2) (ii) a S-stirrup spacing (m);
b233: calculating the time-varying resistance R in the function by adopting an error transfer method or a Monte Carlo method according to the calculation conditionstThe statistical characteristics of (1).
4. The method for quantitatively evaluating the service state of the existing pile-based retaining structure according to any one of claims 1 to 3, wherein in the step S3, a JC method or a Monte Carlo method is adopted to calculate the failure probability and the reliability index.
5. The reliability-based quantitative evaluation method for the service state of the existing pile-type retaining structure according to any one of claims 1 to 3, wherein the step S4 comprises:
c41: determining the failure probability grade of the evaluation structure according to the failure probability and the probability grade standard obtained by calculation;
c42: accurately determining the economic loss grade and the casualty grade of the pile structure after failure according to the economic loss grade standard and the casualty grade, and further determining the comprehensive consequence grade after failure;
c43: and determining the risk level of the existing pile structure according to the probability level and the consequence level, and giving corresponding countermeasures.
6. The method for quantitatively evaluating the service state of the existing pile-type retaining structure based on the reliability according to any one of claims 1 to 3, wherein the step S4 comprises:
d41: according to the current stage t1Monitoring the action effect at the moment, if the irresistance does not occur, the action effect does not change greatly along with the time, and then t in the futurenTime of day effect S (t)n) Is the same as S (t)1) The same;
d42: according to the long-term service state function of the existing pile retaining structure, P is satisfied at the end of the service lifef＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]Wherein [ Pf]Is an acceptable value for the probability of failure, R (t)n) Is a supporting structure tnMoment resistance, S (t)1) Is a supporting structure t1The effect of time of day effects;
d43: using a trial algorithm, a t is givenn＞t1Calculating tnThe statistical characteristics of the time-varying resistance and whether P is satisfied are judgedf＝P(Z(tn)＝g[R(tn)，S(tn)]＝R(tn)-S(t1)＜0)≥[Pf]If not, increasing tnRecalculating until a critical point satisfying the formula is found;
d44: the time t finally calculated on the basis of the step D43nThen t isn-t1Namely the residual service life of the existing pile supporting and retaining structure.
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