CN102589987A - Bending-resistance mechanical property detection method of structural dimension lumber - Google Patents

Abstract

The invention relates to a bending-resistance mechanical property detection method of a structural dimension lumber, belonging to the technical field of the structural lumber. Based on a bending-resistance mechanical property detection result of a small sample of a perfect clear material and knot defect information included in the structural dimension lumber to be detected, the method detects the bending-resistance elasticity modulus and the bending-resistance intensity of the structural dimension lumber, wherein the main defects of the structural dimension lumber are the knots. The bending-resistance mechanical property detection method of the structural dimension lumber can quickly and accurately detect the bending-resistance mechanical property of the structural dimension lumber, furthermore reinforce the quality control of import dimension lumbers and the dimension lumbers produced in China, so that the structural dimension lumber is safely applied to the building stricture design in our country.

Description

The anti-bending mechanics method for testing performance of structural lumber dimension stock

Technical field

The present invention relates to a kind of anti-bending mechanics method for testing performance of structural lumber dimension stock, belong to the structural lumber technical field.

Background technology

Along with the popularization of light-duty wooden in China, the application quantity sustainable growth of structural lumber dimension stock.Identical with natural timber, defectives such as the knaur that dimension stock comprised, twill can have a strong impact on its physical and mechanical property, reduce its mechanical property design objective value.How to consider defect influence such as knaur, twill, detection architecture becomes one of key issue with the mechanical property of timber and lumber standards material quickly and accurately.

The seventies in last century, scholars such as Canadian Madsen propose to adopt the original foundation of full scale test (full-scale test) as timber design strength value in the timber deciding grade and level, and promptly material for test is directly from structured material, and sectional dimension is consistent with actual components.Particularly for dimension stock, directly make test specimen with dimension stock, sectional dimension is not changed, and obtaining the various intensity of dimension stock, and to name be " structural timber deciding grade and level test ", reflects the final service condition of timber-work as much as possible in the hope of test findings.The full scale test method of structural timber is accepted by the many developed countries in the world very soon, becomes the main flow of current detection structural timber intensity method.But adopt full scale test as detect and judge timber design strength value original according to the time, it need consume a large amount of material resources, financial resources and manpower, and the full scale test method is not omnipotent.In addition, the present structure of China needs to rely on a large amount of imports to meet the need of market with shortage, particularly dimension stock of wood-based product every year, does not still possess the condition that relies on full scale test to obtain timber design strength value fully.

Terseness and practicality based on flawless clear material small specimen method of testing; Existing China's " Code for design of timber structures " GB 50005 regulation logs all are to adopt the original foundation of the test findings of flawless clear material small specimen as definite its design strength value with the lumps of wood (containing sheet material), but flawless clear material small specimen test method reflect structure timber characteristics well.For dimension stock, the dimension stock to the different brackets of external part import in China GB 50005 standards has carried out the conversion of intensity index, but how its mechanical property is detected and check, and relevant criterion and detection method do not appear in China as yet.

Summary of the invention

The objective of the invention is to propose a kind of anti-bending mechanics method for testing performance of structural lumber dimension stock; With the knaur defect information that the anti-bending mechanics The performance test results and the structural lumber dimension stock test specimen to be detected of flawless clear material small specimen comprised, detection architecture is with timber and lumber standards material anti-bending mechanics performance.

The anti-bending mechanics method for testing performance of the structural lumber dimension stock that the present invention proposes comprises following each step:

(1) from the flawless clear material small specimen of the two ends intercepting of test specification material, small specimen is of a size of 20mm * 20mm * 300mm, measures the bending resistance elastic modulus E of flawless clear material small specimen ₀With bending strength f ₀, repeat this step, and to the bending resistance elastic modulus E of a plurality of flawless clear material small specimen that obtains ₀With bending strength f ₀Average, obtain the average bending resistance elastic modulus of flawless clear material small specimen

Average bending strength

(2) xsect of establishing the test specification material is a rectangle, and the wide of rectangular cross section is b, and height is h, and the moment of inertia of note xsect is I, I=bh ³/ 12, the cross section resistance moment is W, W=bh ²/ 6;

When (3) the test specification material being tested, maximum degradation defective knaur is placed two test load(ing) point c ₁And c ₂Between, two distances of testing between the load(ing) point are l ₁, l ₁=6h, the distance between each side strong point and the load(ing) point is l ₂, l ₂=6h, the distance between the end of each side strong point and test specification material is l ₃, l ₃Greater than h/2, two strong point a ₁, a ₂Between distance, promptly testing span is L, L=18h;

(4) measure two strong point a ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia I of neutral axis _Ig, knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _It, and to establish the moment of flexure that each knaur bears in any time of testing process be M _i, i=1 wherein, 2 ..., k, k are two strong point a ₁, a ₂Between all knaur numbers;

(5) at two test load(ing) point c ₁And c ₂The place is imposed load F/2 simultaneously, and the vertical displacement that records test centre of span point O place is a Δ, and the bending resistance elastic modulus that obtains the test specification material is E ₁, E ₁=Fl ₂(3L ²-4l ₂ ²)/(48I Δ), l wherein ₂Be the strong point of each side and the distance between the load(ing) point, L is the test span;

(6) continue at two test load(ing) point c ₁And c ₂The place applies equal loads simultaneously, destroys until the test specification material, and note load at this moment is failing load F _Max, obtain the bending strength f of test specification material ₁, f ₁=l ₂F _Max/ 2W;

(7) establishing central point O, to be in the moment of flexure that any time of test process bears be M ₀, M ₀=l ₂F/2, wherein l ₂Be the strong point of each side and the distance between the load(ing) point;

(8) the bending resistance elastic modulus E of the above-mentioned test specification material of employing ₁Average bending resistance elastic modulus with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₁, B ₁, with fitting parameter value A ₁, B ₁Average bending resistance elastic modulus to flawless clear material small specimen

The knaur defect information that is comprised with dimension stock

Revise, the bending resistance elastic modulus that obtains dimension stock does $E=\left({\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">A</figure-callout>}}_1\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\right[(I_{\mathrm{Ig}}/I)(M_i/M_o)]+B_1){\stackrel{\&OverBar;}{E}}_0,$ Wherein, I _IgBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia of neutral axis, I is the moment of inertia of dimension stock xsect;

(9) the bending strength f of the above-mentioned test specification material of employing ₁Average bending strength with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₂, B ₂, with fitting parameter value A ₂, B ₂Average bending strength to flawless clear material small specimen

The knaur defect information I that is comprised with the test specification material _ItRevise, the bending strength that obtains dimension stock does

Wherein, I _ItBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between maximum degradation fault location knaur be positioned at the moment of inertia of the cross section of tension side with respect to neutral axis.

The anti-bending mechanics method for testing performance of the structural lumber dimension stock that the present invention proposes; Adopt easy flawless clear material small specimen method of testing; And having comprised structural lumber dimension stock test specimen knaur defect influence to be detected, evaluation structure is with the anti-bending mechanics performance of timber and lumber standards material quickly and accurately.Detection method of the present invention can be used for strengthening the quality control of the dimension stock of import dimension stock and China's autonomous production, and implementation structure is with the Secure Application of timber and lumber standards material in China's Architectural Structure Design.

Description of drawings

Fig. 1 loads synoptic diagram for the bending resistance to structural lumber dimension stock test specimen in the detection method of the present invention.

Fig. 2 is the H-H sectional view of Fig. 1, the sectional view of the maximum degradation fault location knaur of structural lumber dimension stock test specimen promptly to be detected.

Fig. 3 is the bending resistance elastic modulus test result of the flawless clear material small specimen of the embodiment of the invention.

Fig. 4 is the bending strength test result of the flawless clear material small specimen of the embodiment of the invention.

Fig. 5 is the bending resistance elastic modulus of the test of the embodiment of the invention with the dimension stock test specimen, comprises the regretional analysis result of knaur defect information based on flawless clear material small specimen bending resistance elastic modulus test result and dimension stock test specimen.

Fig. 6 is the bending strength of the test of the embodiment of the invention with the dimension stock test specimen, comprises the regretional analysis result of knaur defect information based on flawless clear material small specimen bending strength test result and dimension stock test specimen.

Among Fig. 1 and Fig. 2, the 1st, structural lumber dimension stock test specimen to be detected, the 2nd, tension side is positioned at its neutral axis lower end, and the 3rd, maximum degradation defective knaur, the 4th, compression-side is positioned at its neutral axis upper end, and the 5th, neutral axis; a ₁, a ₂Be the strong point, c ₁, c ₂Be load(ing) point, l ₁Be the distance of anti-bending test two load(ing) points, l ₂Be the horizontal range of each side load(ing) point to strong point, l ₃Be the distance of the end of the strong point and structural lumber dimension stock, L is for detecting span, and O is a centre of span point, and h is a structural lumber dimension stock test specimen cross-sectional height to be detected, and b is a cross-sectional width.

Embodiment

The anti-bending mechanics method for testing performance of the structural lumber dimension stock that the present invention proposes, wherein as shown in Figure 1 to the bending resistance loading synoptic diagram of structural lumber dimension stock test specimen, comprise following each step:

(1) from the flawless clear material small specimen of the two ends intercepting of test specification material, small specimen is of a size of 20mm * 20mm * 300mm, measures the bending resistance elastic modulus E of flawless clear material small specimen ₀With bending strength f ₀, repeat this step, and to the bending resistance elastic modulus E of a plurality of flawless clear material small specimen that obtains ₀With bending strength f ₀Average, obtain the average bending resistance elastic modulus of flawless clear material small specimen

Average bending strength

(2) xsect of establishing the test specification material is a rectangle, and the wide of rectangular cross section is b, and height is h, and the moment of inertia of note xsect is I, I=bh ³/ 12, the cross section resistance moment is W, W=bh ²/ 6;

When (3) the test specification material being tested, maximum degradation defective knaur is placed two test load(ing) point c ₁And c ₂Between, two distances of testing between the load(ing) point are l ₁, l ₁=6h, the distance between each side strong point and the load(ing) point is l ₂, l ₂=6h, the distance between the end of each side strong point and test specification material is l ₃, l ₃Greater than h/2, two strong point a ₁, a ₂Between distance, promptly testing span is L, L=18h;

(4) measure two strong point a ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia I of neutral axis _Ig, knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _It, and to establish the moment of flexure that each knaur bears in any time of testing process be M _i, i=1 wherein, 2 ..., k, k are two strong point a ₁, a ₂Between all knaur numbers;

(5) at two test load(ing) point c ₁And c ₂The place is imposed load F/2 simultaneously, and the vertical displacement that records test centre of span point O place is a Δ, and the bending resistance elastic modulus that obtains the test specification material is E ₁, E ₁=Fl ₂(3L ²-4l ₂ ²)/(48I Δ), l wherein ₂Be the strong point of each side and the distance between the load(ing) point, L is the test span;

(6) continue at two test load(ing) point c ₁And c ₂The place applies equal loads simultaneously, destroys until the test specification material, and note load at this moment is failing load F _Max, obtain the bending strength f of test specification material ₁, f ₁=l ₂F _Max/ 2W;

(7) establishing central point O, to be in the moment of flexure that any time of test process bears be M ₀, M ₀=l ₂F/2, wherein l ₂Be the strong point of each side and the distance between the load(ing) point;

(8) the bending resistance elastic modulus E of the above-mentioned test specification material of employing ₁Average bending resistance elastic modulus with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₁, B ₁, with fitting parameter value A ₁, B ₁Average bending resistance elastic modulus to flawless clear material small specimen

The knaur defect information that is comprised with dimension stock Revise, the bending resistance elastic modulus that obtains dimension stock does $E=\left({\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">A</figure-callout>}}_1\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\right[(I_{\mathrm{Ig}}/I)(M_i/M_o)]+B_1){\stackrel{\&OverBar;}{E}}_0,$ Wherein, I _IgBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia of neutral axis, I is the moment of inertia of dimension stock xsect;

(9) the bending strength f of the above-mentioned test specification material of employing ₁Average bending strength with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₂, B ₂, with fitting parameter value A ₂, B ₂Average bending strength to flawless clear material small specimen

The knaur defect information I that is comprised with the test specification material _ItRevise, the bending strength that obtains dimension stock does

Wherein, I _ItBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between maximum degradation fault location knaur be positioned at the moment of inertia of the cross section of tension side with respect to neutral axis.

According to the method for the invention, structural lumber dimension stock of the present invention comprises knaur dissimilar, size, and major defect is a knaur.

According to the method for the invention, flawless clear material small specimen of the present invention is with reference to " timber structure test method standard " GB/T50329, earlier from the flawless clear material small specimen of the two ends intercepting of structural lumber dimension stock.

According to the method for the invention, flawless clear material small specimen of the present invention carries out its bending resistance elastic modulus E with reference to GB/T 1936 ₀With bending strength f ₀Test is behind the test loaded, by the destruction place density p of the flawless clear material small specimen of standard GB/T 1933 tests ₀, repeat this step, to the bending resistance elastic modulus E of a plurality of flawless clear material small specimen that obtains ₀, bending strength f ₀With destruction place density p ₀Average, obtain the average bending resistance elastic modulus of the flawless clear material small specimen of the corresponding intercepting of every dimension stock

Average bending strength

With average destruction density

According to the method for the invention, flawless clear material small specimen bending resistance elastic modulus E of the present invention ₀Test result, adopt its destruction place density p ₀As independent variable, carry out regretional analysis with reference to formula I, obtain fitting parameter value C ₁, D ₁:

${\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">E</figure-callout>}}_0={\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{\&rho;}}_0^{1.25}+{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">D</figure-callout>}}_1$ Formula (I)

According to the method for the invention, flawless clear material small specimen bending strength f of the present invention ₀Test result, adopt its destruction place density p ₀As independent variable, carry out regretional analysis with reference to formula II, obtain fitting parameter value C ₂, D ₂:

${\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">f</figure-callout>}}_0={\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{\&rho;}}_0^{1.25}+{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA0000141733420000011.png,HDA0000141733420000013.png"\; state="\{\{state\}\}">D</figure-callout>}}_2$ Formula (II)

According to the method for the invention, it should satisfy the dimensional requirement of " timber structure test method standard " GB/T 50329 structural lumber dimension stock to be detected of the present invention, and the maximum degradation defective of full size dimension stock test specimen is knaur, and measuring its average density is ρ ₁

According to the method for the invention, structural lumber dimension stock to be detected of the present invention carries out its bending resistance elastic modulus E by standard GB/T 50329 ₁With bending strength f ₁Test, bending resistance loading synoptic diagram sees also shown in Figure 1, and the maximum degradation fault location knaur (see figure 2) with dimension stock during anti-bending test places between two load(ing) points, is positioned at maximum degradation fault location to guarantee dimension stock test specimen bending resistance destruction place.Behind the test loaded, by the destruction place density p of standard GB/T 1933 test specification material test specimens ₂

According to the method for the invention, the bending resistance elastic modulus test result of structural lumber dimension stock to be detected of the present invention adopts density and tests knaur information all in the span as independent variable, carries out multiple regression analysis with reference to formula III:

${\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">E</figure-callout>}}_1={\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA0000141733420000011.png,HDA0000141733420000021.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\left[(I_i/I)(M_i/M_o)\right]+{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="HDA0000141733420000011.png,HDA0000141733420000021.png"\; state="\{\{state\}\}">D</figure-callout>}}_3{\mathrm{\&rho;}}^{1.25}+F_3$ Formula (III)

According to the method for the invention; The bending strength test result of structural lumber dimension stock to be detected of the present invention; The knaur information that adopts the maximum degradation fault location that is comprised in density and the full size dimension stock test specimen test span is carried out multiple regression analysis as independent variable with reference to formula IV:

f ₁=C ₄I _i/ I+D ₄ρ ^1.25+ F ₄Formula (IV)

According to the method for the invention; The ratio of the bending resistance elastic modulus of structural lumber dimension stock to be detected of the present invention and the average bending resistance elastic modulus of flawless clear material small specimen; Adopt all knaur information that comprise in the test span as independent variable, carry out regretional analysis with reference to formula V:

${\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">E</figure-callout>}}_1/{\stackrel{\&OverBar;}{E}}_0={\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">A</figure-callout>}}_1\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\left[(I_{\mathrm{Ig}}/I)(M_i/M_o)\right]+{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">B</figure-callout>}}_1$ Formula (V)

According to the method for the invention; The ratio of the average bending strength of the bending strength of structural lumber dimension stock to be detected of the present invention and flawless clear material small specimen; Adopt the maximum degradation fault location knaur information that comprises in the test span as independent variable, carry out regretional analysis with reference to formula VI:

${\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HDA0000141733420000011.png"\; state="\{\{state\}\}">f</figure-callout>}}_1/{\stackrel{\&OverBar;}{f}}_0=A_2{I}_{\mathrm{It}}/I+{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="HDA0000141733420000011.png,HDA0000141733420000013.png"\; state="\{\{state\}\}">B</figure-callout>}}_2$ Formula (VI)

Characteristics that below will be through specific embodiment further explain structural lumber dimension stock of the present invention anti-bending mechanics method for testing performance with use in the technique effect that had, but therefore the present invention does not receive any restriction.

Choose 22 Xing'an Mountains larches [Larix gmelinii RuPr] structural lumber dimension stock and use dimension stock as test; Its size is 40mm * 90mm * 3000mm; Xsect is a rectangle, and it comprises knaur dissimilar, size, and major defect is a knaur.

From above-mentioned test with the flawless clear material small specimen of dimension stock intercepting.With reference to " timber structure test method standard " GB/T 50329, before the full size anti-bending test, from the flawless clear material small specimen of 5 20mm * 20mm * 300mm of the every equal intercepting in dimension stock two ends.

With above-mentioned flawless clear material small specimen, reference standard GB/T 1936 its bending resistance elastic modulus Es of test ₀With bending strength f ₀, and the destruction place density of measuring flawless clear material small specimen is ρ ₀, repeat this step, to the bending resistance elastic modulus E of a plurality of flawless clear material small specimen that obtains ₀, bending strength f ₀With destruction place density p ₀Average, obtain the average bending resistance elastic modulus of the flawless clear material small specimen of the corresponding intercepting of every dimension stock

Average bending strength

With average destruction density

With above-mentioned destruction place density p ₀Be independent variable,, carry out regretional analysis, obtain fitting parameter value C according to formula I of the present invention to the bending resistance elastic modulus test result of above-mentioned flawless clear material small specimen ₁=19.95, D ₁=3.20, coefficient R ²Be 0.710, root mean square RMSE is 1.78, and compares (Fig. 3) with measured value, and the bending resistance elastic modulus that shows flawless clear material small specimen mainly receives the influence of its density, can adopt theoretical calculation model Come accurately prediction.

With above-mentioned destruction place density p ₀Be independent variable, the bending strength test result to above-mentioned flawless clear material small specimen carries out regretional analysis according to formula II of the present invention, obtains fitting parameter value C ₂=186.96, D ₂=-0.69, coefficient R ²Be 0.832, root mean square RMSE is 12.20, and compares (Fig. 4) with measured value, and the bending strength that shows flawless clear material small specimen mainly receives the influence of its density, can adopt theoretical calculation model

Come accurately prediction.

Above-mentioned test is rectangle with the xsect of dimension stock, and the wide b of rectangular cross section is 40mm, and high h is 90mm, and length is 2020mm, and the moment of inertia of xsect is I, I=bh ³/ 12=2430000mm ⁴, the cross section resistance moment is W, W=bh ²/ 6=54000mm ³, and to measure its average density be ρ ₁

Dimension stock is used in above-mentioned test, carried out the anti-bending mechanics performance test with reference to " timber structure test method standard " GB/T 50329, the loading synoptic diagram sees also shown in Figure 1, wherein, maximum degradation defective knaur is tested load(ing) point c as for two ₁And c ₂Between, two distances of testing between the load(ing) point are l ₁, l ₁=6h=540mm, the distance between each side strong point and the load(ing) point is l ₂, l ₂=6h=540mm, the distance between the end of each side strong point and test specification material is l ₃, l ₃=200mm is greater than h/2, two strong point a ₁, a ₂Between distance, promptly testing span is L, L=18h=1620mm.

Record above-mentioned test and test the moment of inertia I of the whole cross section of each knaur that is comprised in the span with respect to neutral axis with dimension stock _Ig, knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _It, and to establish the moment of flexure that each knaur bears in any time of test process be M _i, i=1 wherein, 2 ..., k, k are two strong point a ₁, a ₂Between all knaur numbers.

To above-mentioned two test load(ing) point c ₁And c ₂While imposed load F/2, the vertical displacement that records test centre of span point O place is a Δ, obtains testing the bending resistance elastic modulus that uses dimension stock and is E ₁, E ₁=Fl ₂(3L ²-4l ₂ ²)/(48I Δ), l wherein ₂Be the strong point of each side and the distance between the load(ing) point, L is the test span.

To above-mentioned two test load(ing) point c ₁And c ₂Continue to apply simultaneously equal loads, destroy with dimension stock until test, note load at this moment is failing load F _Max, and measure destruction place density p ₂, obtain testing bending strength f with dimension stock ₁, f ₁=l ₂F _Max/ 2W.

The moment of flexure that any time that above-mentioned test centre of span point O is in test process bears is M _o, M _o=l ₂F/2, wherein l ₂Be the strong point of each side and the distance between the load(ing) point.

Average destruction density with above-mentioned flawless clear material small specimen

Test uses the average density of dimension stock to be ρ ₁Or test is with the destruction place density p of dimension stock ₂In any one be first independent variable, with two strong point a ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia I of neutral axis _IgOr knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _ItBe second independent variable,, carry out regretional analysis according to formula III of the present invention to the bending resistance elastic modulus test result of above-mentioned test with dimension stock.

Following table 1 has been listed and has been tested the results by multivariate regression analysis with the bending resistance springform of dimension stock in the present embodiment, adopts above-mentioned test to use the average density of dimension stock to be ρ ₁Information with all whole cross sections of knaur in the test span

As independent variable, fitting result is best, fitting parameter value C ₃=-4.92, D ₃=6.27, F ₃=7.76, coefficient R ²Be 0.669, RMSE is 1.01, shows that test mainly receives its density and interior all the knaur defect influence of test span with the bending resistance springform of dimension stock, can adopt theoretical calculation model $E_{}$ ${}_1=-4.92\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\left[(I_{\mathrm{Ig}}/I)(M_i/M_o)\right]+6.27{\mathrm{\&rho;}}_1^{1.25}+7.76$ Come accurately prediction.

Table 1 test is with the bending resistance springform E of dimension stock ₁Results by multivariate regression analysis

Average destruction density p with above-mentioned flawless clear material small specimen ₀, the test use the average density of dimension stock to be ρ ₁Or test is with the destruction place density p of dimension stock ₂In any one be first independent variable, with two strong point a ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia I of neutral axis _IgOr knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _ItBe second independent variable,, carry out regretional analysis according to formula IV of the present invention to the bending strength test result of above-mentioned test with dimension stock.

Following table 2 has been listed and has been tested the results by multivariate regression analysis with the bending strength of dimension stock in the present embodiment, adopts above-mentioned test to use the average density of dimension stock to be ρ ₁Be positioned at the cross section information I of tension side with maximum degradation fault location knaur in the test span _It/ I is best as the fitting result of independent variable, obtains fitting parameter value C ₄=-61.41, D ₄=57.31, F ₄=10.44, coefficient R ²Be 0.759, RMSE is 4.94, shows that test mainly receives its density and the influence of testing maximum degradation fault location knaur in the span with the bending strength of dimension stock, can adopt theoretical calculation model

Come accurately prediction.

Table 2 test is with the results by multivariate regression analysis of the bending strength f1 of dimension stock

Through above-mentioned flawless clear material small specimen and test are compared with the regretional analysis of the bending resistance elastic modulus test result of dimension stock; Obtaining flawless clear material small specimen bending resistance elastic modulus major influence factors is density, the bending resistance elastic modulus major influence factors that dimension stock is used in test as density, test in the span all knaur information

and can set up a kind of knaur defect information that is comprised with flawless clear material small specimen bending resistance elastic modulus and dimension stock thus and come the method for detection architecture with timber and lumber standards material bending resistance elastic modulus.

Above-mentioned detection architecture adopts the bending resistance elastic modulus E of above-mentioned test specification material with the method for timber and lumber standards material bending resistance elastic modulus ₁Average bending resistance elastic modulus with flawless clear material small specimen

Ratio, carry out regretional analysis according to formula V of the present invention, obtain fitting parameter value A ₁=-0.53, B ₁=0.97 (Fig. 5) is with fitting parameter value A ₁, B ₁Average bending resistance elastic modulus to flawless clear material small specimen

The knaur defect information that is comprised with dimension stock Revise, obtain the bending resistance elastic modulus of dimension stock: $E=(-0.53\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}[(I_{\mathrm{Ig}}/I)(M_i/M_o)]+0.97){\stackrel{\&OverBar;}{E}}_0.$

Through above-mentioned flawless clear material small specimen and test are compared with the bending strength test result's of dimension stock regretional analysis; Obtaining flawless clear material small specimen bending strength major influence factors is density, and test uses the bending strength major influence factors of dimension stock to be maximum degradation fault location knaur information I in density, the test span _It/ I can set up a kind of with flawless clear material small specimen bending strength thus

Come the method for detection architecture with the knaur defect information that dimension stock is comprised with timber and lumber standards material bending strength.

Above-mentioned detection architecture adopts the bending strength f of above-mentioned test specification material with the method for timber and lumber standards material bending strength ₁Average bending strength with flawless clear material small specimen

Ratio, carry out regretional analysis according to formula VI of the present invention, obtain fitting parameter value A ₂=-0.66, B ₂=0.45 (Fig. 6) is with fitting parameter value A ₂, B ₂Average bending strength to flawless clear material small specimen

The maximum degradation fault location knaur information I that dimension stock comprised _It/ I revises, and obtains the bending strength of dimension stock: $f=(-0.66I_{\mathrm{It}}/I+0.45){\stackrel{\&OverBar;}{f}}_0.$

Claims (1)

1. the anti-bending mechanics method for testing performance of a structural lumber dimension stock is characterized in that this method comprises following each step:

(1) from the flawless clear material small specimen of the two ends intercepting of test specification material, small specimen is of a size of 20mm * 20mm * 300mm, measures the bending resistance elastic modulus E of flawless clear material small specimen ₀With bending strength f ₀, repeat this step, and to the bending resistance elastic modulus E of a plurality of flawless clear material small specimen that obtains ₀With bending strength f ₀Average, obtain the average bending resistance elastic modulus of flawless clear material small specimen

Average bending strength

(2) xsect of establishing the test specification material is a rectangle, and the wide of rectangular cross section is b, and height is h, and the moment of inertia of note xsect is I, I=bh ³/ 12, the cross section resistance moment is W, W=bh ²/ 6;

When (3) the test specification material being tested, maximum degradation defective knaur is placed two test load(ing) point c ₁And c ₂Between, two distances of testing between the load(ing) point are l ₁, l ₁=6h, the distance between each side strong point and the load(ing) point is l ₂, l ₂=6h, the distance between the end of each side strong point and test specification material is l ₃, l ₃Greater than h/2, two strong point a ₁, a ₂Between distance, promptly testing span is L, L=18h;

(4) measure two strong point a ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia I of neutral axis _Ig, knaur is positioned at the moment of inertia I of the cross section of tension side with respect to neutral axis _It, and to establish the moment of flexure that each knaur bears in any time of testing process be M _i, i=1 wherein, 2 ..., k, k are two strong point a ₁, a ₂Between all knaur numbers;

(5) at two test load(ing) point c ₁And c ₂The place is imposed load F/2 simultaneously, and the vertical displacement that records test centre of span point O place is a Δ, and the bending resistance elastic modulus that obtains the test specification material is E ₁, E ₁=Fl ₂(3L ²-4l ₂ ²)/(48I Δ), l wherein ₂Be the strong point of each side and the distance between the load(ing) point, L is the test span;

(6) continue at two test load(ing) point c ₁And c ₂The place applies equal loads simultaneously, destroys until the test specification material, and note load at this moment is failing load F _Max, obtain the bending strength f of test specification material ₁, f ₁=l ₂F _Max/ 2W;

(7) establishing central point O, to be in the moment of flexure that any time of test process bears be M ₀, M ₀=l ₂F/2, wherein l ₂Be the strong point of each side and the distance between the load(ing) point;

(8) the bending resistance elastic modulus E of the above-mentioned test specification material of employing ₁Average bending resistance elastic modulus with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₁, B ₁, with fitting parameter value A ₁, B ₁Average bending resistance elastic modulus to flawless clear material small specimen

The knaur defect information that is comprised with dimension stock

Revise, the bending resistance elastic modulus that obtains dimension stock does $E=\left(A_1\underset{i=1}{\overset{k}{\mathrm{\&Sigma;}}}\right[(I_{\mathrm{Ig}}/I)(M_i/M_o)]+B_1){\stackrel{\&OverBar;}{E}}_0,$ Wherein, I _IgBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between the whole cross section of each knaur with respect to the moment of inertia of neutral axis, I is the moment of inertia of dimension stock xsect;

(9) the bending strength f of the above-mentioned test specification material of employing ₁Average bending strength with flawless clear material small specimen

Ratio carry out regretional analysis, obtain fitting parameter value A ₂, B ₂, with fitting parameter value A ₂, B ₂Average bending strength to flawless clear material small specimen

The knaur defect information I that is comprised with the test specification material _ItRevise, the bending strength that obtains dimension stock does

Wherein, I _ItBe two strong point a in the dimension stock anti-bending test ₁, a ₂Between maximum degradation fault location knaur be positioned at the moment of inertia of the cross section of tension side with respect to neutral axis.

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