CN103246766B - The actual moment of flexure projectional technique of girder of beam bridge and beam bridge Bearing Capacity Evaluation method - Google Patents
The actual moment of flexure projectional technique of girder of beam bridge and beam bridge Bearing Capacity Evaluation method Download PDFInfo
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Abstract
The invention discloses a kind of actual moment of flexure projectional technique of girder and Bearing Capacity Evaluation method of beam bridge.Moment of flexure projectional technique is wherein for foundation with actual average fracture height, from corresponding xsect moment of flexure-fracture height figure, read the moment of actual measurement place, crack xsect, described moment of flexure-fracture height figure obtains by carrying out cross section Nonlinear Full Range Analysis to bridge cross section.Bearing Capacity Evaluation method adopts moment of flexure projectional technique disclosed by the invention to calculate after crucial section moment on evaluation bridge, utilizes the correction factor Z obtained based on FRACTURE CHARACTERISTICS
3rapid evaluation is carried out to the load-bearing capacity of beam bridge, evaluates unsanctioned bridge for by the inventive method, choice for use loading test can carry out Bearing Capacity Evaluation further.Adopt bridge calculation of Bending Moment method of the present invention can calculate the moment of flexure of its respective cross-section fast, thus reduce the number of times of loading test, or evaluate load carrying capacity of bridge more exactly.
Description
Technical field
The present invention relates to a kind of girder moment of flexure projectional technique and concrete beam bridge Bearing Capacity Evaluation method of the concrete beam bridge based on fracture height.
Background technology
When adopting the standard system method in " highway bridge load-bearing capacity detecting appraisal code " to evaluate concrete beam bridge load-bearing capacity, Structure Checking Method will be carried out to each evaluation object, even need to carry out loading test, process is more numerous and diverse, and technical requirement is high.
Standard system method mainly comprises bridge technology status investigation and loading test, obtains checking coefficient Z by bridge technology status investigation
1, bring in " highway bridge load-bearing capacity detecting appraisal code " and calculate in formula (7.3.1), the result according to calculating judges whether to need to carry out loading test:
Work as γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1(1-ξ
e) time, assessed beam bridge is without the need to carrying out loading test;
Work as γ
0s > R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1(1-ξ
e) time, assessed beam bridge need carry out loading test, obtains checking coefficient Z by loading test
2, by this checking coefficient Z
2as checking coefficient Z in formula (7.3.1)
1the load-bearing capacity of value to beam bridge evaluate.
γ
0S≤R(f
d,ξ
cα
dc,ξ
sα
ds)Z
1(1-ξ
e)（7.3.1）
In formula (7.3.1): γ
0: the important coefficient of structure; S: load effect function; R (): drag effect function; f
d: design value for strength of material; a
dc: concrete members geometric parameter values; a
ds: member reinforcing steel bar geometric parameter values; Z
1: load-bearing capacity checking coefficient; ξ
e: load-bearing capacity deterioration coefficient; ξ
c: the cross section reduction coefficient of armored concrete structure; ξ
s: the cross section reduction coefficient of reinforcing bar.
Checking coefficient Z is obtained by bridge technology status investigation
1there is larger artificial subjectivity, do not consider the stressing conditions of structure, for differentiating that bridge exists larger artificial subjectivity the need of the situation of carrying out loading test.Especially, when there is erroneous judgement, cause occurring mistake to the evaluation of bed rearrangement load carrying capacity of bridge.
Summary of the invention
An object of the present invention is to provide a kind of girder of the beam bridge based on fracture height actual moment of flexure projectional technique, to ask for the girder xsect moment of flexure of concrete beam bridge quickly and accurately.
For this reason, the actual moment of flexure projectional technique of girder of beam bridge provided by the invention, the method calculates the girder xsect moment of flexure of concrete beam bridge, feature is with the actual average fracture height of this transverse cross-sectional area for foundation, reads the moment of flexure of this xsect from the moment of flexure-fracture height figure of this xsect; This transverse cross-sectional area described is: along bridge to, the region of 0.5m before and after this xsect; Moment of flexure-fracture height the figure of this xsect described gets as follows:
If this xsect described is A cross section:
Step 1, sets up the A cross-section analysis model of bridge, and carries out cross section Nonlinear Full Range Analysis according to Bridge Design parameter, obtain the strain of the moment of flexure in the A cross section under load at different levels, curvature and the centre of form;
Step 2, ask for the fracture height in A cross section under every grade of load respectively, the fracture height wherein under one-level load in A cross section is y '
cr, and:
Y'
cr=(ε
c-γ f
tk/ E
c)/φ+y
c(formula 1)
In (formula 1): ε
cfor the centre of form in A cross section under this grade of load strains; γ is plastlcity coefficient of reinforced concrete member in tensile zone; f
tkfor bridge characteristic value of concrete tensile strength used; E
cfor bridge modulus of elasticity of concrete used; φ is the curvature in A cross section under grade load; y
cfor the centre of form wheelbase in front A cross section of ftractureing is from the vertical range of soffit;
Afterwards, the fracture height in the A cross section under every grade of load is obtained;
Thus the moment of flexure in the A cross section under the corresponding load in integrating step 1 can obtain the moment of flexure-fracture height in A cross section under every grade of load;
Step 3, with the moment of flexure under load at different levels-fracture height mapping, obtains the moment of flexure-fracture height figure of this xsect.
In above-mentioned steps 1 when carrying out cross section Nonlinear Full Range Analysis, load application is f step by step
1, f
2, f
3..., f
a..., f
a; Wherein f
1=0, load f
a+1time A cross section curvature=load f
atime A cross section curvature+1/200 be the limit curvature in A cross section, load f
atime A cross section curvature be the limit curvature in A cross section.
Another object of the present invention is to provide a kind of beam bridge Bearing Capacity Evaluation method, the method is the improvement done existing standard system method, by introducing more objective factors to guarantee the objectivity of bridge technology status investigation result, more objectively to determine that bridge is the need of carrying out loading test, thus reduce the impact of artificial subjective factor in bridge technology status investigation, specify the service condition of loading test.The method utilizes standard system method to evaluate beam bridge load-bearing capacity, and feature is: utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judge that assessed beam bridge is the need of carrying out loading test, wherein:
γ
0: the important coefficient of structure; S: load effect function; R (): drag effect function; f
d: design value for strength of material; a
dc: concrete members geometric parameter values; a
ds: member reinforcing steel bar geometric parameter values; Z
1: load-bearing capacity checking coefficient; ξ
e: load-bearing capacity deterioration coefficient; ξ
c: the cross section reduction coefficient of armored concrete structure; ξ
s: the cross section reduction coefficient of reinforcing bar;
Checking coefficient Z
3value is:
When being evaluated bridge and thering is no crack, checking coefficient Z
3be 1;
When being evaluated bridge and having crack, checking coefficient Z
3computing method are as follows:
First, utilize the girder moment of flexure projectional technique of above-mentioned beam bridge to ask for the actual measurement moment of flexure in each crucial cross section of bridge to be evaluated respectively, wherein the actual measurement moment of flexure of crucial cross section n is M
real n, n=1,2,3 ..., N; N is total number in crucial cross section on bridge to be evaluated; Described crucial cross section be bridge to be evaluated by investigation girder spaning middle section, and this is investigated girder spaning middle section region and is had crack; Described girder spaning middle section region is: along bridge to, the region of 0.5m before and after this girder spaning middle section;
Then, utilize the theoretical moment of flexure in each crucial cross section of finite element analysis computation respectively, wherein the theoretical moment of flexure of crucial cross section n is M
reason n;
Then, the capacity correct coefficient ξ of bridge to be evaluated is asked for:
When ξ≤0.5, Z
3=1.30;
As 0.5 < ξ < 0.6, Z
3=1.8-ξ;
When ξ=0.6, Z
3=1.20;
As 0.6 < ξ < 0.7, Z
3=1.5-0.5 ξ;
When ξ=0.7, Z
3=1.15;
As 0.7 < ξ < 0.8, Z
3=1.05-0.5 ξ;
When ξ=0.8, Z
3=1.05;
As 0.8 < ξ < 0.9, Z
3=1.45-0.5 ξ
When ξ=0.9, Z
3=1.00;
As 0.9 < ξ < 1.0, Z
3=1.45-0.5 ξ;
When ξ=1.0, Z
3=0.95;
As 1.0 < ξ < 1.1, Z
3=1.95-ξ;
When ξ=1.1, Z
3=0.85;
As 1.1 < ξ < 1.2, Z
3=1.95-ξ;
When ξ=1.2, Z
3=0.75;
As 1.2 < ξ < 1.3, Z
3=1.95-ξ;
When ξ=1.3, Z
3=0.65;
As 1.3 < ξ < 1.4, Z
3=1.3-0.5 ξ;
When ξ=1.4, Z
3=0.60;
As 1.4 < ξ < 1.5, Z
3=1.3-0.5 ξ;
When ξ>=1.5, Z
3=0.55;
Utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) when judging whether to need to carry out loading test:
Work as γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, without the need to carrying out loading test;
Work as γ
0s > R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, need loading test be carried out.
Beam bridge Bearing Capacity Evaluation method of the present invention adopts moment of flexure projectional technique disclosed by the invention to calculate after crucial section moment on evaluation bridge, utilizes the correction factor Z obtained based on FRACTURE CHARACTERISTICS
3rapid evaluation is carried out to the load-bearing capacity of beam bridge, evaluates unsanctioned bridge for by the inventive method, choice for use loading test can carry out Bearing Capacity Evaluation further.Adopt bridge calculation of Bending Moment method of the present invention can calculate the moment of flexure of its respective cross-section fast, thus reduce the number of times of loading test, or evaluate load carrying capacity of bridge more exactly.
Accompanying drawing explanation
Fig. 1 is the derivation reference view of formula 1 in method of the present invention;
Fig. 2 is the moment of flexure-fracture height figure of embodiment, each straight line shown in this figure by represent drag standard value R respectively from lower
k, drag design load R
dwith the basic combined value γ of effect
0s
ud;
Fig. 3 be across footpath be 10 meters, deck-molding is the RC freely-supported hollow slab bridge side plate spaning middle section moment of flexure-fracture height figure of 0.45 meter;
Fig. 4 be across footpath be 10 meters, deck-molding is plate spaning middle section moment of flexure-fracture height figure in the RC freely-supported hollow slab bridge of 0.45 meter;
Fig. 5 be across footpath be 10 meters, deck-molding is the RC simple T beam bridge side bar spaning middle section moment of flexure-fracture height figure of 0.9 meter;
Fig. 6 be across footpath be 13 meters, deck-molding is the RC simple T beam bridge central sill spaning middle section moment of flexure-fracture height figure of 1.1 meters;
Fig. 7 be across footpath be 25 meters, deck-molding is the PSC simple T beam bridge side bar spaning middle section moment of flexure-fracture height figure of 1.7 meters;
Fig. 8 be across footpath be 40 meters, deck-molding is the PSC simple T beam bridge central sill spaning middle section moment of flexure-fracture height figure of 2.5 meters;
Fig. 9 be across footpath be 30 meters, deck-molding is the PSC continuous T beam bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2 meters;
Figure 10 be across footpath be 30 meters, deck-molding is across side bar spaning middle section moment of flexure-fracture height figure in the PSC continuous T beam bridge of 2 meters;
Figure 11 be across footpath be 35 meters, deck-molding is the PSC continuous T beam bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.3 meters;
Figure 12 be across footpath be 35 meters, deck-molding is span centre girder span middle section moment of flexure-fracture height figure in the PSC continuous T beam bridge of 2.3 meters;
Figure 13 be across footpath be 20 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 1.5 meters;
Figure 14 be across footpath be 30 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay central sill spaning middle section moment of flexure-fracture height figure of 2.0 meters;
Figure 15 be across footpath be 35 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.3 meters;
Figure 16 be across footpath be 40 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.5 meters.
Embodiment
In concrete beam bridge, one of modal disease is exactly crack.Based on following 2 points, between crack and the load-bearing capacity of structure, there is corresponding relation: the destructive process of (1) xoncrete structure is exactly in fact that crack produces, the process of expansion and unstability; (2), when carrying out structural design according to design specifications, mainly carry out from amount of deflection, stress, this three aspect of fracture width checking;
In loading test method, using several leading indicators that amount of deflection, stress, crack situation are evaluated as load carrying capacity of bridge, crack therefore can be selected as the indirect reflection index of section capacity.
And in bridge appearance checks, crack is always as paying close attention to object, and crack is a main Index for examination, so many scholars have used the relation between the Developing Condition of multiple method fracture and the load-bearing capacity of structure to do research.But Maintenance specification and evaluation criteria just give the limit value of fracture width, and the details such as cracking height, crack location, cracking scope are not added clearly state.
Fracture parameters has several as follows: (1) maximum height, average height, accumulative height; (2) breadth extreme, mean breadth, accumulative width; (3) maximum/minimum spacing, average headway; (4) ftracture scope.Wherein crack width and spacing parameter influence many factors, is difficult to the model that theorizes, and is not monotonic functional relationship with load/load-bearing capacity, therefore is difficult to utilize; Cracking scope weakens the impact in crucial cross section, will not utilize.Like this, also remaining three parameters relevant to fracture height.Crack maximum height has recorded the maximal bending moment that structure was once subject to faithfully, is the optimal parameter of reflection load/load-bearing capacity.
Document is had to record according to short-cut method, the fracture height of derivation cross section under ultimate limit states.Due to the impact of this structure of nonlinear material, concrete cracking, short-cut method precision is very limited; The more important thing is, short-cut method can not provide the overall process relation curve to the vital fracture height of assessment and load-bearing capacity (moment of flexure).
In conjunction with the introduction in background technology, in bridge technology status investigation and loading test assessment, all do not make full use of bridge machinery achievement.To generally detect and make regular check on the crack Information application that obtains in load carrying capacity of bridge evaluation if can deeply excavate, this can not only improve evaluation effect, and meet the overall evaluating system of current Chinese code of practice, do not increase too many extra work amount, the bridge maintenance work that task is heavy can be adapted to.
The present invention is based on reliability and importance that fracture height value evaluates load carrying capacity of bridge, a kind of computing method calculating the girder section moment of flexure of concrete beam bridge according to actual measurement fracture height value are proposed, the method calculates a certain xsect moment of flexure of the girder of concrete beam bridge, specifically with the actual average fracture height of this transverse cross-sectional area for foundation, from the moment of flexure-fracture height figure of this xsect, read the moment of flexure of this xsect; This transverse cross-sectional area is wherein: along bridge to, the region of 0.5m before and after this xsect; Namely centered by this xsect, along bridge to, the region in the 0.5m of its back and forth or left and right; Moment of flexure-fracture height the figure of used xsect gets as follows:
Step 1, sets up the A cross-section analysis model of bridge, and carries out cross section Nonlinear Full Range Analysis according to the design parameter on bridge drawing, obtain the strain of the moment of flexure in the A cross section under load at different levels, curvature and the centre of form; The constitutive relation adopted when setting up the A cross-section analysis model of bridge is actual structure in " Code for design of concrete structures GB50010-2010 [S] ", namely this structure of bridge material truth is reflected, corresponding with actual measurement fracture parameters to ensure the calculating fracture parameters adopted in whole Method And Principle derivation; And then ensure: when adopting the load-bearing capacity of method of the present invention to bridge to evaluate, when the calculating fracture parameters of surveying in fracture parameters and Method And Principle derivation contrasts, adopt actual structure of material; Need to limit further, in this step 1 when carrying out cross section Nonlinear Full Range Analysis, load application is f step by step
1, f
2, f
3..., f
a..., f
a; Wherein f
1=0, load f
a+1time A cross section curvature=load f
atime A cross section curvature+1/200 be the limit curvature in A cross section, load f
atime A cross section curvature be the limit curvature in A cross section.
Step 2, asks for the fracture height in A cross section under every grade of load respectively, wherein under certain one-level load (as load f
aunder) fracture height in A cross section is y '
cr, and:
Y'
cr=(ε
c-γ f
tk/ E
c)/φ+y
c(formula 1)
In (formula 1):
ε
cfor the centre of form in A cross section under this grade of load strains;
γ is plastlcity coefficient of reinforced concrete member in tensile zone;
F
tkfor characteristic value of concrete tensile strength, the strength grade of concrete used according to bridge is determined;
E
cfor modulus of elasticity of concrete, the strength grade of concrete used according to this bridge is determined;
φ is the curvature in A cross section under this grade of load;
Y
cfor the centre of form wheelbase in front A cross section of ftractureing is from the vertical range of soffit;
Afterwards, obtain the fracture height in the A cross section under every grade of load, thus obtain the moment of flexure-fracture height under every grade of load;
Step 3, with the moment of flexure under load at different levels-fracture height mapping, is surveyed the moment of flexure-fracture height figure in direction across bridge cross section, place, crack accordingly,
Above-mentioned steps 1 to step 3 can use cross section Nonlinear Full Range Analysis software simulating.
Below the derivation about (formula 1) that inventor provides:
With reference to figure 1, in a certain direction across bridge cross section of bridge as in spaning middle section, if:
Before bridge cracking, the centre of form wheelbase of spaning middle section is y from the distance of soffit
c,
The distance of the neutral axis distance soffit of spaning middle section is y
n;
Before bridge cracking, centre of form axle overlaps with neutral axis, i.e. y
c=y
n;
Under certain grade of cracking load effect:
Fracture height is y '
cr;
Neutral axis is from distance soffit y
nposition move to distance soffit y '
nposition;
Crack apogee distance centre of form axle ± Δ '
crdistance, i.e. y'
cr=y
c± Δ '
cr;
Have according to plane cross-section assumption: ε
y=ε
c-φ (y-y
c), y represents a certain height on spaning middle section, ε
yrepresent the strain at spaning middle section height y place,
Therefore: y=(ε
c-ε
y)/φ+y
c(formula 11)
According to geometric relationship and the mechanics of materials, the cracking height of fracture has: y=y'
cr, ε
y=γ f
tk/ E
c, substituting into (formula 11) can obtain:
y'
cr＝(ε
c-γf
tk/E
c)/φ+y
c。
It should be noted that, the actual measurement fracture height in the present invention and fracture height are the vertical range that crack upwards extends bottom beam section; The actual average fracture height of transverse cross-sectional area (girder spaning middle section region) refers to the mean value of all slits actual measurement height in this transverse cross-sectional area.
The present invention makes full use of the crack information of bridge inspection, in conjunction with the mechanism support that cross section non-linear full--process is destroyed, a kind of beam bridge load-bearing capacity rapid method for assessment is proposed, and embed in the standard system method in " highway bridge load-bearing capacity detecting appraisal code ", be particularly useful for the bridge types such as simply supported girder bridge, cantilever glider bridge, continuous bridge.
Concrete beam bridge Bearing Capacity Evaluation method of the present invention utilizes checking coefficient Z
3concrete beam bridge load-bearing capacity is evaluated, namely adopts Z
1z
3replace the Z in formula (7.3.1) in " highway bridge load-bearing capacity detecting appraisal code "
1, loading test is carried out in the requirement specified according to " highway bridge load-bearing capacity detecting appraisal code " for the bridge needs not meeting evaluation requirement.
Wherein:
When bridge to be evaluated does not have crack, checking coefficient Z
3be 1;
When bridge to be evaluated has crack, checking coefficient Z
3computing method are as follows:
First, utilize the girder calculation of Bending Moment method of above-mentioned concrete beam bridge to ask for the actual measurement moment of flexure in each crucial cross section of bridge to be evaluated respectively, wherein the actual measurement moment of flexure of crucial cross section n is M
real n, n=1,2,3 ..., N; N is total number in crucial cross section on bridge to be evaluated; The spaning middle section of the side bar of bridge, central sill and other beams chooses crucial cross section by inquiry.
Then, utilize finite element analysis computation to obtain the theoretical moment of flexure in each crucial cross section respectively, wherein the theoretical moment of flexure of crucial cross section n is M
reason n;
Then, the capacity correct coefficient ξ of bridge to be evaluated is asked for:
Wherein:
When ξ≤0.5, Z
3=1.30;
As 0.5 < ξ < 0.6, Z
3=1.8-ξ;
When ξ=0.6, Z
3=1.20;
As 0.6 < ξ < 0.7, Z
3=1.5-0.5 ξ;
When ξ=0.7, Z
3=1.15;
As 0.7 < ξ < 0.8, Z
3=1.05-0.5 ξ;
When ξ=0.8, Z
3=1.05;
As 0.8 < ξ < 0.9, Z
3=1.45-0.5 ξ
When ξ=0.9, Z
3=1.00;
As 0.9 < ξ < 1.0, Z
3=1.45-0.5 ξ;
When ξ=1.0, Z
3=0.95;
As 1.0 < ξ < 1.1, Z
3=1.95-ξ;
When ξ=1.1, Z
3=0.85;
As 1.1 < ξ < 1.2, Z
3=1.95-ξ;
When ξ=1.2, Z
3=0.75;
As 1.2 < ξ < 1.3, Z
3=1.95-ξ;
When ξ=1.3, Z
3=0.65;
As 1.3 < ξ < 1.4, Z
3=1.3-0.5 ξ;
When ξ=1.4, Z
3=0.60;
As 1.4 < ξ < 1.5, Z
3=1.3-0.5 ξ;
When ξ>=1.5, Z
3=0.55;
Utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) when judging whether to need to carry out loading test:
Work as γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, without the need to carrying out loading test;
Work as γ
0s > R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, need loading test be carried out.
ξ and Z
3between the theoretical foundation of above-mentioned value relation and analytic explanation be: checkout coefficient Z
3=1/ ξ, in practical application, Z for the purpose of safe
3value be above-mentioned value.
Utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judge whether that the theoretical foundation needing to carry out loading test is: the checking coefficient Z obtained by bridge technology status investigation
1with the correction factor Z obtained based on FRACTURE CHARACTERISTICS
3comprehensive Assessment, namely utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judge whether the stressing conditions that needs to consider bridge reality when carrying out loading test, comparatively with utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1(1-ξ
e) judge that beam bridge is more objective, reliable the need of the result of carrying out load.
Inventor utilizes the moment of flexure-fracture height figure of the application to obtain the moment of flexure-fracture height figure of each girder spaning middle section on each beam bridge in standard drawing as access method, and wherein partial graph is as follows:
Across footpath be 10 meters, deck-molding is the RC freely-supported hollow slab bridge side plate spaning middle section moment of flexure-fracture height figure of 0.45 meter, as shown in Figure 3;
Across footpath be 10 meters, deck-molding is plate spaning middle section moment of flexure-fracture height figure in the RC freely-supported hollow slab bridge of 0.45 meter, as shown in Figure 4;
Across footpath be 10 meters, deck-molding is the RC simple T beam bridge side bar spaning middle section moment of flexure-fracture height figure of 0.9 meter, as shown in Figure 5;
Across footpath be 13 meters, deck-molding is the RC simple T beam bridge central sill spaning middle section moment of flexure-fracture height figure of 1.1 meters, as shown in Figure 6;
Across footpath be 25 meters, deck-molding is the PSC simple T beam bridge side bar spaning middle section moment of flexure-fracture height figure of 1.7 meters, as shown in Figure 7;
Across footpath be 40 meters, deck-molding is the PSC simple T beam bridge central sill spaning middle section moment of flexure-fracture height figure of 2.5 meters, as shown in Figure 8;
Across footpath be 30 meters, deck-molding is the PSC continuous T beam bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2 meters, as shown in Figure 9;
Across footpath be 30 meters, deck-molding is across side bar spaning middle section moment of flexure-fracture height figure in the PSC continuous T beam bridge of 2 meters, as shown in Figure 10;
Across footpath be 35 meters, deck-molding is the PSC continuous T beam bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.3 meters, as shown in figure 11;
Across footpath be 35 meters, deck-molding is span centre girder span middle section moment of flexure-fracture height figure in the PSC continuous T beam bridge of 2.3 meters, as shown in figure 12;
Across footpath be 20 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 1.5 meters, as shown in figure 13;
Across footpath be 30 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay central sill spaning middle section moment of flexure-fracture height figure of 2.0 meters, as shown in figure 14;
Across footpath be 35 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.3 meters, as shown in figure 15;
Across footpath be 40 meters, deck-molding is the PSC Continuous Box Girder Bridge end bay side bar spaning middle section moment of flexure-fracture height figure of 2.5 meters, as shown in figure 16;
In Fig. 3 to Figure 16, horizontal ordinate is fracture height, and unit is rice, and ordinate is moment of flexure, and unit is KNm.
Embodiment:
The bridge of this embodiment is: the continuous small box girder of 3 × 20m, and single hole is 20m across footpath, adopts C50 concrete, and regular reinforcement adopts HRB335, deformed bar tensile strength standard value f
pk=1860Mpa, the wide 12m of bridge floor, laterally four prefabricated small box girders, deck-molding 1.5m.Class of loading is I grade, highway.
The load-bearing capacity of standard system method to the bridge of this embodiment in " highway bridge load-bearing capacity detecting appraisal code " is adopted to evaluate:
Step 1, can obtain checking coefficient Z by bridge technology status investigation
1=0.9;
Step 2, utilizes formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judge that this bridge is the need of carrying out loading test:
(1) the central sill spaning middle section place actual measurement moment M of this beam bridge
realcalculating:
Carrying out of fracture is investigated, and occurs crack in the span centre region of middle span centre beam.Crack average height is the mean value according to the maximum fracture height of investigated cross section.Investigate the scope that cross section scope is chosen as 0.5m near spaning middle section, calculate the mean value of 2 ~ 5 maximum fracture heights in this region.The actual average fracture height of investigation is 47cm;
Utilize method of the present invention can this embodiment beam bridge middle span centre beam mid span moment-fracture height figure as shown in Figure 2.
The actual measurement moment M of this beam bridge central sill spaning middle section is obtained by Fig. 2
real=4010KNm;
(2) by the Bridge Design parameter of this embodiment, set up structure of finite element analysis model, by structural finite element analysis software, obtain the theoretical moment of flexure of central sill spaning middle section.M
reason=3337KN.m
(3) capacity correct coefficient ξ is 1.202, Z
3=0.748.
The coefficient for importance of structure γ of the beam bridge of this embodiment
0=1.0, check according to specification " Highway bridge technique status assessment standard ", " highway bridge load-bearing capacity detecting appraisal code " and the requirement of " highway bridge and culvert Maintenance specification ", obtain load-bearing capacity deterioration coefficient ξ
e, armored concrete structure cross section reduction coefficient ξ
c, reinforcing bar cross section reduction coefficient ξ
s;
The basic combined value γ of the effect of span centre beam in bridge can be obtained by structural finite element analysis software
0s
udwith drag design load R
d, be respectively 3337KNm and 5780KNm.
By load-bearing capacity checking coefficient Z
1z
3=0.9 × 0.748=0.6732 brings into and can obtain load-bearing capacity situation.Checking computation results is as follows:
3337≤5780×0.9×0.748=3901.5
The effect of structure is less than its drag, and therefore load-bearing capacity meets the demands, without the need to carrying out loading test.
The second time of the beam bridge of this embodiment is investigated:
Due to increasing of overweight car, middle span centre beam Bridge Crack is carried out further, and the actual measurement moment of flexure of second time investigation result and central sill spaning middle section is as shown in table 1:
Table 1
This time the capacity correct coefficient ξ of investigation is 1.998, Z
3=0.55.
Adopt formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judging that this beam bridge is the need of carrying out loading test, checking computation results is as follows:
3337＞5780×0.9×0.55=2861.1
Load-bearing capacity does not meet design requirement, and now needs to carry out loading test.
As follows by the evaluation conclusion of carrying out loading test in " highway bridge load-bearing capacity detecting appraisal code ":
(1) under highway I grade of trial load effect, strain, amount of deflection checking coefficient mean value are 0.94,0.90.
(2) during I grade, highway, Z
3=0.45;
(3) the overall evaluation result of bridge is three class bridges, needs to give maintenance and reinforcement in time.
Z in this embodiment
1z
3and Z
2error 10%,
Explanation utilizes formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) to carry out preliminary judgement to the load-bearing capacity of beam bridge be reliable.
Claims (2)
1. beam bridge Bearing Capacity Evaluation method, is characterized in that, the method utilizes standard system method to evaluate beam bridge load-bearing capacity, and feature is: utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) judge that assessed beam bridge is the need of carrying out loading test, wherein:
γ
0: the important coefficient of structure;
S: load effect function;
R (): drag effect function;
F
d: design value for strength of material;
A
dc: concrete members geometric parameter values;
A
ds: member reinforcing steel bar geometric parameter values;
Z
1: load-bearing capacity checking coefficient;
ξ
e: load-bearing capacity deterioration coefficient;
ξ
c: the cross section reduction coefficient of armored concrete structure;
ξ
s: the cross section reduction coefficient of reinforcing bar;
Checking coefficient Z
3value is:
When being evaluated bridge and thering is no crack, checking coefficient Z
3be 1;
When being evaluated bridge and having crack, checking coefficient Z
3computing method are as follows:
First, utilize the girder moment of flexure projectional technique of beam bridge to ask for the actual measurement moment of flexure in each crucial cross section of bridge to be evaluated respectively, wherein the actual measurement moment of flexure of crucial cross section n is M
real n, n=1,2,3 ..., N; N is total number in crucial cross section on bridge to be evaluated; Described crucial cross section be bridge to be evaluated by investigation girder spaning middle section, and this is investigated girder spaning middle section region and is had crack; Described girder spaning middle section region is: along bridge to, the region of 0.5m before and after this girder spaning middle section;
The actual moment of flexure projectional technique of girder of described beam bridge calculates the girder xsect moment of flexure of concrete beam bridge, with the actual average fracture height of this transverse cross-sectional area for foundation, reads the moment of flexure of this xsect from the moment of flexure-fracture height figure of this xsect; This transverse cross-sectional area described is: along bridge to, the region of 0.5m before and after this xsect; Moment of flexure-fracture height the figure of this xsect described gets as follows:
If this xsect is A cross section:
Step 1, sets up the A cross-section analysis model of bridge, and carries out cross section Nonlinear Full Range Analysis according to Bridge Design parameter, obtain the strain of the moment of flexure in the A cross section under load at different levels, curvature and the centre of form;
Step 2, ask for the fracture height in A cross section under every grade of load respectively, the fracture height wherein under one-level load in A cross section is y '
cr, and:
Y'
cr=(ε
c-γ f
tk/ E
c)/φ+y
c(formula 1)
In (formula 1): ε
cfor the centre of form in A cross section under this grade of load strains; γ is plastlcity coefficient of reinforced concrete member in tensile zone; f
tkfor bridge characteristic value of concrete tensile strength used; E
cfor bridge modulus of elasticity of concrete used; φ is the curvature in A cross section under grade load; y
cfor the centre of form wheelbase in front A cross section of ftractureing is from the vertical range of soffit;
Afterwards, the fracture height in the A cross section under every grade of load is obtained;
Thus the moment of flexure in the A cross section under the corresponding load in integrating step 1 can obtain the moment of flexure-fracture height in A cross section under every grade of load;
Step 3, with the moment of flexure under load at different levels-fracture height mapping, obtains the moment of flexure-fracture height figure of this xsect;
Then, utilize the theoretical moment of flexure in each crucial cross section of finite element analysis computation respectively, wherein the theoretical moment of flexure of crucial cross section n is M
reason n;
Then, the capacity correct coefficient ξ of bridge to be evaluated is asked for:
When ξ≤0.5, Z
3=1.30;
As 0.5 < ξ < 0.6, Z
3=1.8-ξ;
When ξ=0.6, Z
3=1.20;
As 0.6 < ξ < 0.7, Z
3=1.5-0.5 ξ;
When ξ=0.7, Z
3=1.15;
As 0.7 < ξ < 0.8, Z
3=1.05-0.5 ξ;
When ξ=0.8, Z
3=1.05;
As 0.8 < ξ < 0.9, Z
3=1.45-0.5 ξ
When ξ=0.9, Z
3=1.00;
As 0.9 < ξ < 1.0, Z
3=1.45-0.5 ξ;
When ξ=1.0, Z
3=0.95;
As 1.0 < ξ < 1.1, Z
3=1.95-ξ;
When ξ=1.1, Z
3=0.85;
As 1.1 < ξ < 1.2, Z
3=1.95-ξ;
When ξ=1.2, Z
3=0.75;
As 1.2 < ξ < 1.3, Z
3=1.95-ξ;
When ξ=1.3, Z
3=0.65;
As 1.3 < ξ < 1.4, Z
3=1.3-0.5 ξ;
When ξ=1.4, Z
3=0.60;
As 1.4 < ξ < 1.5, Z
3=1.3-0.5 ξ;
When ξ>=1.5, Z
3=0.55;
Utilize formula γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) when judging whether to need to carry out loading test:
Work as γ
0s≤R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, without the need to carrying out loading test;
Work as γ
0s > R (f
d, ξ
cα
dc, ξ
sα
ds) Z
1z
3(1-ξ
e) time, need loading test be carried out.
2. beam bridge Bearing Capacity Evaluation method as claimed in claim 1, it is characterized in that, in described step 1 when carrying out cross section Nonlinear Full Range Analysis, load application is f step by step
1, f
2, f
3..., f
a..., f
a; Wherein f
1=0, load f
a+1time A cross section curvature=load f
atime A cross section curvature+1/200 be the limit curvature in A cross section, load f
atime A cross section curvature be the limit curvature in A cross section.
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| CN106485029B (en) * | 2016-10-27 | 2019-07-09 | 北京市市政工程研究院 | Bearing capacity evaluation method after Concrete beam bridge damage based on overstrain |
| CN108345568B (en) * | 2018-02-09 | 2021-04-06 | 石家庄铁道大学 | Health monitoring characteristic parameter-based heavy-load railway concrete bearing capacity evaluation method |
| CN110399678B (en) * | 2019-07-25 | 2022-12-09 | 武汉理工大学 | Feasibility judgment method for large vehicle passing through simply supported beam bridge |
| CN112906162B (en) * | 2021-03-19 | 2024-03-29 | 大连科迈尔海洋科技有限公司 | Bending moment calculation method and device for support column of marine crane |
| CN113408024B (en) * | 2021-05-11 | 2023-10-27 | 北京城建设计发展集团股份有限公司 | Method for calculating bending-resistant bearing capacity of grouting tongue-and-groove joint of assembled underground structure |
| CN113654504B (en) * | 2021-09-03 | 2022-06-14 | 招商局重庆交通科研设计院有限公司 | Prestressed concrete beam bridge evaluation method based on crack appearance characteristics |
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| CN103065035A (en) * | 2012-09-29 | 2013-04-24 | 长沙理工大学 | Method for designing longitudinal prestressed tendons of variable-section prestressed concrete continuous beam bridge |
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| CN103065035A (en) * | 2012-09-29 | 2013-04-24 | 长沙理工大学 | Method for designing longitudinal prestressed tendons of variable-section prestressed concrete continuous beam bridge |
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