CN104990793A - Bearing capacity assessment method for timber architecture obtained after fire disaster - Google Patents

Abstract

The invention discloses a bearing capacity assessment method for timber architecture obtained after the fire disaster. The method comprises the following steps that a detection scheme is determined according to the combustion situation constructed through the fire disaster field timber architecture; probe drilling detecting is carried out on the timber architecture components on the fire disaster field through an impedance instrument, and resistance values of different parts of the timber architecture components, subjected to fire, on the fire disaster field are obtained; a relevance mathematical model between mechanical performance parameters and impedance values of timber is established through the test; part of physical and mechanical performance parameters of the timber, subjected to different fire degrees, of different parts of the timber architecture components are obtained; the rest of unknown mechanical performance parameters of anisotropic materials of the timber are calculated according to the approximate proportion relation between mechanical parameters of the timber; structural modeling and material defining are carried out in Abaqus finite element analysis software, and the bearing capacity of the timber structure obtained after the fire disaster is calculated. The bearing capacity assessment method for the timber architecture obtained after the fire disaster is scientific, objective and accurate.

Description

The bearing capacity evaluation method of concrete on fire timber buildings

Technical field

The invention belongs to the bearing capacity evaluation method of building structure, particularly relate to the bearing capacity evaluation method of timber buildings after being subject to fire.

Background technology

Fire is one of the most common, disaster threatening public security and social development the most at large, has sporadic strong feature, can cause huge loss and destruction to national economy and human environment.China's ancient building is in the majority with timber structure, the easiest breaking out of fire, timber structure fire can cause heavy direct property loss and casualties, simultaneously due to its distinctive construction history of ancient Wood construction, artistic value with just cannot be regenerated once destroy by fire, these indirect losses that fire causes cannot be weighed with money.

Building is after suffering fire, and due to the difference of developing fire, on-the-spot ventilation condition and fire extinguishing situation, structural elements can produce damage and fracture in various degree, and whole building also can be caused time serious to cave in.Compared with other building materials, one of major defect of timber is exactly inflammable.Timber, once burning, discharges a large amount of heats, aggravation fire development, and along with the burning of timber compoment, its sectional dimension can reduce, and the intensity of timber also can reduce.Therefore, the generation of fire has a significant impact for the load-bearing capacity of timber buildings and stability.Can the timber buildings after suffering fire continue to be on active service, and which structural elements needs to carry out reinforcing or replacing, and all depends on the load-bearing capacity of concrete on fire timber buildings.Therefore, a kind of appraisal procedure fast and effectively for timber buildings concrete on fire load-bearing capacity is formulated extremely important.

Although the appraisal procedure of existing multiple building structure load-bearing capacity at present, but evaluation object is main mainly with steel construction, concrete, but the material of timber buildings has certain singularity, damage check supporting with it and bearing capacity evaluation method are also relative blank.Existing test and assessment method is often the degree of impairment of qualitatively analyze structure construction and makes grading to degree of injury, quantitatively can not provide the decreasing value of fire for strength of wood and the load-bearing capacity of concrete on fire timber structure.In simulation calculation, market mainstream finite element software carry material depot based on steel and concrete, still effectively can not simulate timber.

Summary of the invention

For above-mentioned defect and the deficiency of the existence of prior art, the object of the invention is to a kind of bearing capacity evaluation method proposing science, accurate and effective concrete on fire timber buildings.Whether this appraisal procedure can be applied to damage check and the safety assessment of timber buildings concrete on fire, by carrying out bearing capacity evaluation to by the timber compoment after fire, evaluating it and being applicable to continuing to be on active service or degradation use, for follow-up reinforcing and transformation provide theoretical foundation.

For achieving the above object, present invention employs following technical scheme:

A bearing capacity evaluation method for concrete on fire timber buildings, is characterized in that, comprise the following steps:

Step 1: the combustion case determination detection scheme built according to scene of fire timber buildings;

Step 2: according to the determined detection scheme of step 1, uses the timber buildings component of impedance instrument to scene of fire to carry out probe boring and detects, obtain the Resistance Value of scene of fire by fiery timber buildings component different parts;

Step 3: by testing the correlativity mathematical model set up between each mechanical property parameters of timber and resistance value;

Step 4: the Resistance Value and the step 3 gained correlativity mathematical model that are subject to fiery timber buildings component different parts according to step 2 gained calamity scene, calculates a part of Physical and mechanical properties parameter of timber buildings component different parts difference by the timber of fiery degree;

Step 5: according to the approximate ratio relation existed between timber each mechanics parameter, the Wood mechanical property parameter utilizing step 4 known to calculate in Abaqus finite element software calculates timber as all the other the unknown mechanical property parameters needed for anisotropic material;

Step 6: carry out structural modeling and material definition in Abaqus finite element analysis software, calculate the load-bearing capacity of concrete on fire timber structure.

Described step 1 comprises:

A) according to combustion of wood situation, all timber compoments in scene of fire are classified: if this component burns completely or lose effective connection with other components of surrounding, be then judged to be I class A of geometric unitA; If this each cross section, component elongatedness direction combustion case evenly and be effectively connected with other components of surrounding, is then judged to be II class A of geometric unitA; If this component is because fire fire location or on-the-spot ventilation situation cause it to there is combustion case in various degree in each cross section along its length, and other components of this component and surrounding are effectively connected, be then judged to be III class A of geometric unitA;

B) for different classes of component, formulate different detection schemes: for I class A of geometric unitA, do not detect, be considered as the component without load-bearing capacity; For II class A of geometric unitA, be that (the concrete number in region should consider specification and the testing amount two aspect factor of component in 3 ~ 5 regions along component length steering handle component equal area partition, in order to make testing result can truly, reactive means situation all sidedly, each region along the length of component no more than 1 meter), at least 2 measuring points are arranged in each region, wherein Width 1, short transverse 1; For III class A of geometric unitA, burning degree according to component diverse location along its length carries out Region dividing, areal is not limit (unevenness that the concrete number in region is burnt along its length with energy actual response component is advisable), 2 measuring points are at least arranged in each region, wherein Width 1, short transverse 1.

Described step 2 comprises:

A) use impedance instrument to carry out probe borehole test to each measuring point, obtain this point impedance value curve map;

B) resistance value curve is processed, calculates the equivalent drag value at each measuring point place as follows:

$R_e=\frac{{\∫}_a^{b}R\·ds}{b-a}$

R in formula _efor the equivalent drag value at measuring point place; A be Resistance Value curve when there is resistance probe thrust the degree of depth; When b is the disappearance of Resistance Value resistance due to curvature, probe thrusts the degree of depth; R is the Resistance Value of a certain depth in timber a to b this section of degree of depth.

Described step 3 comprises:

A) content of the test comprises two aspects: resistance value testing experiment, Physical and mechanical properties testing experiment;

B) take timber as research object, brand-new is not made into test specimen by the timber of fire, above-mentioned test specimen is carried out to the fire simulation experiment of different temperatures, different time, obtain the different timber test specimen by fiery degree, test described in gained test specimen is used to carry out a);

C) resistance value testing experiment: adopt impedance instrument method of testing described in step 2, carries out Resistance Value mensuration to difference by the timber test specimen of fiery degree;

D) physics, Mechanics Performance Testing is tested: according to China " Method for determination of the density of wood " (GB/T 1933-2009), " Method for determination of the modulus of elasticity in compressive parallel to grain of wood " (GB/T 15777-1995), " Method of testing in compressive strength parallel to grain of wood " (GB/T1935-2009), " Method of testing in compression perpendicular to grain of wood " (GB/T 1939-2009) and " Method of testing in bending strength of wood " (GB/T1936.1-2009), determine the density of different this timber test specimen by fiery degree, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and bending strength,

D) take least square method as principle, to c) gained resistance value and d) each Physical and mechanical properties parameter of gained carry out linear regression analysis, obtain correlativity mathematical model.

Described step 4 comprises:

According to the Resistance Value of step 2 gained scene of fire timber buildings component zones of different, by correlativity mathematical model, calculate the density in each region of component, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and bending strength:

Density (unit g/cm ³): y=0.2196x+0.3375;

Parallel-to-grain compressive strength (unit N/mm ²): y=9.4006x+34.586;

Compression strength perpendicular to grain (unit N/mm ²): y=2.0432x+2.8809;

Bending strength (unit N/mm ²): y=22.004x+54.202;

Modulus of elasticity parellel to grain (units MPa): y=3572.8x+9020.1;

Wherein y represents certain physics, mechanical property parameters, and x represents Resistance Value.

Described step 5 comprises:

A) mechanical property of timber has significant anisotropy, and the mechanical property of its rift grain direction, band radial direction and band tangential direction possesses certain correlativity.Utilize the timber modulus of elasticity parellel to grain of step 4 gained, parallel-to-grain compressive strength, compression strength perpendicular to grain and bending strength, approximate treatment can go out the mechanical property in other directions of timber.

B) there is following approximation relation in the elastic modulus E of timber all directions.Wherein E _lrepresent modulus of elasticity parellel to grain; E _trepresent the tangential elastic modulus of band; E _rrepresent band radial elastic modulus.

$\frac{E_T}{E_L}=0.043~0.056,\frac{E_R}{E_L}=0.068~0.115$

C) timber all directions cut elastic modulus G and modulus of elasticity parellel to grain E _lthere is following relation.Wherein G _lTrepresent that distortion produces the modulus of shearing in longitudinal and tangential formed plane; G _lRrepresent that distortion produces in the modulus of shearing longitudinally and on the radial face formed; G _rTrepresent that distortion produces the modulus of shearing in radial direction and tangential formed face.

$\frac{G_{LT}}{E_L}=0.037~0.078,\frac{G_{LR}}{E_L}=0.054~0.089,\frac{G_{RT}}{E_L}=0.005~0.021$

D) the rift grain pressurized of timber, rift grain tension and there is following relation by between curved intensity.Wherein f _{t, L}represent rift grain tensile strength; f _{c, L}represent rift grain compressive strength; f _mrepresent by curved intensity.

$\frac{f_m}{f_{c,L}}=\frac{3\frac{f_{t,L}}{f_{c,L}}-1}{\frac{f_{t,L}}{f_{c,L}}+1}$

E) there is following relation in the strength parallel to grain of timber and band intensity.Wherein f _{c, T}represent the tangential compressive strength of band; f _{c, R}represent band radial crushing strength; f _{c, L}represent parallel-to-grain compressive strength; f _{t, T}represent band tangential tensile strength; f _{t, R}represent the radial tensile strength of band; τ _lTrepresent that distortion produces the shear resistance in longitudinal and tangential formed plane; τ _lRrepresent that distortion produces in the shear resistance longitudinally and on the radial face formed; τ _rTrepresent that distortion produces the shear resistance in radial direction and tangential formed face.

$f_{c,T}\≈f_{c,R}=(\frac{1}{10}~\frac{1}{3})f_{c,L}$

$f_{t,T}\≈f_{t,R}=(\frac{1}{20}~\frac{1}{3})f_{c,L}$

τ _RT＝(0.5～1)f _c,L， ${\mathrm{\τ}}_{LR}=(\frac{1}{7}~\frac{1}{3})f_{c,L},{\mathrm{\τ}}_{LT}=(\frac{1}{7}~\frac{1}{3})f_{c,L}$

Described step 6 comprises

A) char depth of the investigation of foundation step 1 scene of fire and step 2 impedance instrument bore detecting gained component, determines that building members after fire still possesses the part size of load-bearing capacity, for structural modeling.Consider that the mechanical property of different burning degree timber is different, structural modeling answers subregion to carry out, and Region dividing is with step 1 content c);

B) using the density of step 4 and step 5 gained zones of different timber, elastic modulus, compressive strength, tensile strength and bending strength as in the material definition module of parameters input Abaqus, complete the definition of zones of different wooden material mechanics parameter.

C) in Abaqus finite element software, carry out the calculating by timber buildings load-bearing capacity after fire.

The present invention possesses following advantage:

1) the present invention considers that timber is subject to the feature that changes of mechanical property parameters after fire, combined impedance instrument detection method, establish the correlativity mathematical model by timber Resistance Value and mechanical property parameters after fire, this model can predict the mechanical property parameters of the different burning degree timber in scene of fire accurately, quickly and efficiently;

2) the anisotropy Wood mechanical property parameter that the present invention establishes effectively compensate for the deficiency that Abaqus finite element analysis software carries material depot, improves the degree of accuracy that timber buildings calculates in finite element software;

3) the impedance instrument testing result of scene of fire is combined with Abaqus FEM Simulation, define a kind of science, bearing capacity evaluation method that is objective, concrete on fire timber buildings accurately.The method is that the safety assessment of concrete on fire timber buildings and later stage strengthening reconstruction provide theoretical foundation.

4) based on the test of step 3, the summary and induction density of timber, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and the correlativity mathematical model between bending strength and resistance value, its validity is through checking.Engineering staff is when carrying out the evaluation of concrete on fire timber buildings, only need to work described in completing steps 1 and step 2, then, by correlativity mathematical model disclosed in this invention, after carrying out a small amount of evaluation work, each Physical and mechanical properties parameter of scene of fire timber can be obtained.

Accompanying drawing explanation

Fig. 1 is certain timber structure block schematic illustration of concrete on fire.

Fig. 2 is the schematic diagram of A-A section.

Fig. 3 is that scene of fire uses impedance instrument to detect to carrying out probe boring by timber compoment after fire the Resistance Value curve map obtained.

Fig. 4 is the linear regression mathematical model by timber resistance value and density after fire.

Fig. 5 is the linear regression mathematical model by timber resistance value and parallel-to-grain compressive strength after fire.

Fig. 6 is the linear regression mathematical model by timber resistance value and compression strength perpendicular to grain after fire.

Fig. 7 is the linear regression mathematical model by timber resistance value and bending strength after fire.

Fig. 8 is the linear regression mathematical model by timber resistance value and modulus of elasticity parellel to grain after fire.

In figure: 1, wooden frame 2, pin 3, detection zoning 4, certain surface member width direction, region measuring point 5, certain member height direction, region measuring point 6, the region 7 of component charing because of burning, component inside unburned region.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.For a certain timber structure framework in scene of fire, as Fig. 1, this wooden frame is made up of a wooden frame 1 and two pins 2, as follows to the appraisal procedure of its load-bearing capacity:

Step 1: scene of fire situation is investigated, determines detection scheme.

Learn after consulting original plan sheet that the concrete size of this wooden frame is as follows: pin 300mmX300mm; Wooden frame 300mmX450mm.Kind judging is carried out to beam, post component, finds through visual examination: beam and each cross section, right post elongatedness direction combustion case evenly and be effectively connected with other components of surrounding, judge that beam and right post are II class A of geometric unitA; The lower semisection combustion case of left post is more serious than upper semisection, but around Ren Ranyu, other components effectively connect, and judges that left post is as III class A of geometric unitA.Be divided into five regions 3 along component length direction homalographic Jiang Liang and right post, arrange a measuring point 4 in the surface member width direction in each region, short transverse arranges a measuring point 5.Left post is divided into five regions by combustion case, and region is intensive compared with upper semisection at lower semisection.

Beam and column one has 30 measuring points, is numbered it, as " beam 1-district 1-measuring point 1 " " post 2-district 3-measuring point 2 ".Wherein, " beam (post) " represents that the numbering " district " of component represents zone number, and " measuring point " represents that measuring point is numbered.In this example, No. 1 post is left post, and No. 2 posts are right post.

Step 2: according to the determined detection scheme of step 1, uses impedance instrument to carry out probe boring respectively to this beam and column by the rear timber structure framework of fire and detects.

Timber compoment forms charing region because of burning in surperficial certain depth scope, as shown in Figure 2.Charing region does not possess load-bearing capacity, depends on the unburned part timber in member center region by the load-bearing capacity of timber compoment after fire.

The Resistance Value curve that the probe boring detection of each measuring point place obtains as shown in Figure 3.Resistance Value curve represents the Resistance Value of each depth of component, and a bit of Resistance Value of curve high order end and most back segment is close to 0, and this segment length is the degree of depth in charing region.Can judge that timber compoment thrusts the charing regional depth in direction and the length of member center unburned part at probe by Resistance Value curve, above-mentioned size value is used for the modeling of later stage Abaqus finite element analysis computation.

Carry out integral and calculating process to each measuring point resistance value curve, there are two measuring points in each region of component, gets the average resistance value as this region of two point impedance values.After being subject to fire to this example, the impedance instrument test of wooden frame obtains resistance value as shown in following table one.

Table one wooden frame each region measuring point resistance value

Step 3: density of wood, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and the equation of linear regression between bending strength and resistance value that inquiry the present invention concludes.As shown in Fig. 4 ~ 8.

Step 4: according to the Resistance Value in each region of step 2 gained wooden frame beam and column and the equation of linear regression known to step 3, calculate the density of this wooden frame each region timber, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and bending strength.Result of calculation lists in table two (numerical value of overstriking)

Step 5: according to the approximate ratio relation existed between each mechanics parameter of timber, on the basis of step 4 gained Wood mechanical property parameter, calculates the mechanical property parameters of other all directions the unknowns of timber.Result of calculation lists in table two (numerical value of non-overstriking)

Table two wooden frame each region timberphysics, mechanical property parameters

Table two Elastic Modulus, shear mode unit is MPa, and volume unit is unit N/mm ², density unit is g/cm ³

Step 6: carry out structural modeling and material definition in Abaqus finite element analysis software.Carry out load-bearing capacity analysis calculating.

According to the wooden frame model that the size in the component unburned region of gained in step 2 form is set up.

Using step 4 calculate gained in various degree the density of combustion zone, elastic modulus, modulus of shearing, compressive strength, tensile strength and bending strength input Abaqus as parameter value, complete the definition of anisotropy timber.

Consult original design data, when learning that this wooden frame designs, on beam, line load is 4kN/m, in Abaqus FEM (finite element) calculation formula, applies above-mentioned load to wooden frame.Result of calculation shows, wooden frame No. 3 regions and No. 1 post 3 ~ No. 5 region internal stress level all exceed the intensity level of this region timber, likely destroy.

From Physical and mechanical properties parameter and the Abaqus result of calculation of timber in table two, this timber structure framework No. 1 post, 3 ~ No. 5 regions are weakness zone, advise reinforcing or reduce this wooden frame born load in use to this region.

Claims (7)

1. a bearing capacity evaluation method for concrete on fire timber buildings, is characterized in that, comprise the following steps:

Step 1: the combustion case determination detection scheme built according to scene of fire timber buildings;

Step 2: according to the determined detection scheme of step 1, uses the timber buildings component of impedance instrument to scene of fire to carry out probe boring and detects, obtain the Resistance Value of scene of fire by fiery timber buildings component different parts;

Step 3: by testing the correlativity mathematical model set up between each mechanical property parameters of timber and resistance value;

Step 4: the Resistance Value and the step 3 gained correlativity mathematical model that are subject to fiery timber buildings component different parts according to step 2 gained calamity scene, calculates timberphysics, the mechanical property parameters of timber buildings component different parts difference by fiery degree;

Step 5: according to the approximate ratio relation existed between timber each mechanics parameter, the Wood mechanical property parameter utilizing step 4 known to calculate in Abaqus finite element software calculates timber as other the unknown mechanical property parameters needed for anisotropic material;

Step 6: carry out structural modeling and material definition in Abaqus finite element analysis software, calculate the load-bearing capacity of concrete on fire timber structure.

2. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 1, is characterized in that, described step 1 comprises:

A) according to combustion of wood situation, all timber compoments in scene of fire are classified: if this component burns completely or lose effective connection with other components of surrounding, be then judged to be I class A of geometric unitA; If this each cross section, component elongatedness direction combustion case evenly and be effectively connected with other components of surrounding, is then judged to be II class A of geometric unitA; If this component is because fire fire location or on-the-spot ventilation situation cause it to there is combustion case in various degree in each cross section along its length, and other components of this component and surrounding are effectively connected, be then judged to be III class A of geometric unitA;

B) for different classes of component, formulate different detection schemes: for I class A of geometric unitA, do not detect, be considered as the component without load-bearing capacity; For II class A of geometric unitA, be 3 ~ 5 regions along component length steering handle component equal area partition, at least 2 measuring points, wherein Width 1 are arranged in each region, short transverse 1; For III class A of geometric unitA, the burning degree according to component diverse location along its length carries out Region dividing, and areal is not limit, and 2 measuring points are at least arranged in each region, wherein Width 1, short transverse 1.

3. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 2, is characterized in that, described step 2 comprises:

A) use impedance instrument to carry out probe borehole test to each measuring point, obtain this point impedance value curve map;

B) resistance value curve is processed, calculates the equivalent drag value at each measuring point place as follows:

$R_e=\frac{{\∫}_a^{b}R\·ds}{b-a}$

R in formula _efor the equivalent drag value at measuring point place; A be Resistance Value curve when there is resistance probe thrust the degree of depth; When b is the disappearance of Resistance Value resistance due to curvature, probe thrusts the degree of depth; R is the Resistance Value of a certain depth in timber a to b this section of degree of depth.

4. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 3, is characterized in that, described step 3 comprises:

A) content of the test comprises two aspects: resistance value testing experiment, Physical and mechanical properties testing experiment;

B) take timber as research object, brand-new is not made into test specimen by the timber of fire, above-mentioned test specimen is carried out to the fire simulation experiment of different temperatures, different time, obtain the different timber test specimen by fiery degree, test described in gained test specimen is used to carry out a);

C) resistance value testing experiment: adopt impedance instrument method of testing described in step 2, carries out Resistance Value mensuration to difference by the timber test specimen of fiery degree;

D) physics, Mechanics Performance Testing is tested: according to China " Method for determination of the density of wood " (GB/T 1933-2009), " Method for determination of the modulus of elasticity in compressive parallel to grain of wood " (GB/T 15777-1995), " Method of testing in compressive strength parallel to grain of wood " (GB/T1935-2009), " Method of testing in compression perpendicular to grain of wood " (GB/T 1939-2009) and " Method of testing in bending strength of wood " (GB/T1936.1-2009), determine the density of different this timber test specimen by fiery degree, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and bending strength,

D) take least square method as principle, to c) gained resistance value and d) each Physical and mechanical properties parameter of gained carry out linear regression analysis, obtain correlativity mathematical model.

5. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 4, is characterized in that, described step 4 comprises:

According to the Resistance Value of step 2 gained scene of fire timber buildings component zones of different, by correlativity mathematical model, calculate the density in each region of component, modulus of elasticity parellel to grain, compression strength perpendicular to grain, parallel-to-grain compressive strength and bending strength:

Density (unit g/cm ³): y=0.2196x+0.3375;

Parallel-to-grain compressive strength (unit N/mm ²): y=9.4006x+34.586;

Compression strength perpendicular to grain (unit N/mm ²): y=2.0432x+2.8809;

Bending strength (unit N/mm ²): y=22.004x+54.202;

Modulus of elasticity parellel to grain (units MPa): y=3572.8x+9020.1;

Wherein y represents certain physics, mechanical property parameters, and x represents Resistance Value.

6. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 5, is characterized in that, described step 5 comprises:

A) there is following approximation relation in the elastic modulus E of timber all directions:

$\frac{E_T}{E_L}=0.043~0.056,\frac{E_R}{E_L}=0.068~0.115$

Wherein E _lrepresent modulus of elasticity parellel to grain; E _trepresent the tangential elastic modulus of band; E _rrepresent band radial elastic modulus;

B) timber all directions cut elastic modulus G and modulus of elasticity parellel to grain E _lthere is following relation:

$\frac{G_{LT}}{E_L}=0.037~0.078,\frac{G_{LR}}{E_L}=0.054~0.089,\frac{G_{RT}}{E_L}=0.005~0.021$

Wherein G _lTrepresent that distortion produces the modulus of shearing in longitudinal and tangential formed plane; G _lRrepresent that distortion produces in the modulus of shearing longitudinally and on the radial face formed; G _rTrepresent that distortion produces the modulus of shearing in radial direction and tangential formed face;

C) the rift grain pressurized of timber, rift grain tension and there is following relation by between curved intensity:

$\frac{f_m}{f_{c,L}}=\frac{3\frac{f_{t,L}}{f_{c,L}}-1}{\frac{f_{t,L}}{f_{c,L}}+1}$

Wherein f _{t, L}represent rift grain tensile strength; f _{c, L}represent rift grain compressive strength; f _mrepresent by curved intensity;

D) there is following relation in the strength parallel to grain of timber and band intensity:

$f_{c,T}\≈f_{c,R}=(\frac{1}{10}~\frac{1}{3})f_{c,L}$

$f_{t,T}\≈f_{t,R}=(\frac{1}{20}~\frac{1}{3})f_{c,L}$

${\mathrm{\τ}}_{RT}=(0.5~1)f_{c,L},{\mathrm{\τ}}_{LR}=(\frac{1}{7}~\frac{1}{3})f_{c,L},{\mathrm{\τ}}_{LT}=(\frac{1}{7}~\frac{1}{3})f_{c,L}$

Wherein f _{c, T}represent the tangential compressive strength of band; f _{c, R}represent band radial crushing strength; f _{c, L}represent parallel-to-grain compressive strength; f _{t, T}represent band tangential tensile strength; f _{t, R}represent the radial tensile strength of band; τ _lTrepresent that distortion produces the shear resistance in longitudinal and tangential formed plane; τ _lRrepresent that distortion produces in the shear resistance longitudinally and on the radial face formed; τ _rTrepresent that distortion produces the shear resistance in radial direction and tangential formed face.

7. the bearing capacity evaluation method of concrete on fire timber buildings according to claim 6, is characterized in that, described step 6 comprises

A) determine that resistance value curve map determination building members after fire that the region that detection scheme is determined and step 2 obtain still possesses the part size of load-bearing capacity according to step 1, subregion structural modeling;

B) using the density of step 4 and step 5 gained zones of different timber, elastic modulus, compressive strength, tensile strength and bending strength as in the material definition module of parameters input Abaqus, complete the definition of zones of different wooden material mechanics parameter;

C) in Abaqus finite element software, carry out the calculating by timber buildings load-bearing capacity after fire.