CN105512394A - Analysis system and analysis method for overall fire resistance of beam-post wood structure frame - Google Patents

Abstract

The invention discloses an analysis system and an analysis method for overall fire resistance of a beam-post wood structure frame. The analysis system comprises an actual fire simulation module, a structure interior finite element heat transfer analysis module and a structural field finite element analysis and calculation module, wherein the actual fire simulation module is used for generating a simulated fire working condition corresponding to the actual fire working condition in the beam-post wood structure frame; the structure interior finite element heat transfer analysis module is used for acquiring interior temperature distribution of the wood structure under the simulated fire working condition generated by the actual fire simulation module; the structural field finite element analysis and calculation module is used for loading the wood structure so as to acquire structural deformation and damage. With the adoption of the analysis method for fire resistance of the beam-post wood structure frame, fire development, structural interior heat transfer and structure response in the fire development process are simulated, quick analysis of deformation and damage development of the structure in the fire bearing process is realized, visualization can be realized, the method has the characteristics of low cost and conciseness, and practical value is provided for fire performance design and fire risk assessment of the wood structure.

Description

The analytic system of the overall fire resistance of a kind of beam-post wood frame framework and analytical approach

Technical field

The present invention is a kind of method for designing of beam-post wood frame framework fire-resistance of technical field of civil engineering, specifically, is with numerical simulation means, solves beam-post wood frame framework by fiery problem, for actual timber structure fire protection design is offered help.

Background technology

Along with development and the widespread use of recent forest resourceies, the fire resistance that domestic scholars starts to commonly use China seeds carries out research and probe.Timber is the potpourri of the inorganics compositions such as the multiple macromolecule organic such as cellulose, hemicellulose and lignin, water and minerals, they are compared with other building materialss, topmost shortcoming is inflammable, timber is once burning, discharge the development that a large amount of heats accelerates fire, cause larger casualties and property loss.

The foundation of current timber structure fire protection design mainly contains " Code for design of timber structures " and " Code for fire protection design of buildings ".But the main structure fire resistant design method adopting Component-Based Development test in traditional code for fire protection design, influencing each other of timber structure integrated member is not yet considered, the response of structure under natural fire operating mode can not be reflected based on the method for designing of test simultaneously, be difficult to really reflect real stressing conditions.Meanwhile, tradition fire-resistance is based on standard heating curve simulated fire temperature-rise period, many scholars use combustion furnace to carry out relevant fire resistance test to component or structure, and this differs comparatively large with actual fire temperature-rise period, thus can not the fire response of accurate simulation analytical structure.

Research weak point at present about beam-post wood frame framework fire resistance is: 1. the evaluates calculation method lacking timber structure framework under actual fire working accurately; 2. structure analysis lacks the computational analysis based on space entirety; 3., although existing many scholars propose the thought of Systematic Design, for beam-post wood frame, still need design more reasonably computing method.Through consulting the retrieval of existing document, propose a kind of Design of Steel Structures Against Fire method based on Fire-resistance of Steel Structures expert system in the Chinese invention patent of application publication number 103886161A, the method compares difference with the inventive method technical essential and is:

(1) invent described in 103886161A mainly for Design of Steel Structures Against Fire, the present invention mainly focuses on the computation and analysis solving the overall fire resistance of beam-post wood frame framework, and its target, flow process and performance are all different.

(2) invent described in 103886161A and mainly adopt Subject-oriented higher level lanquage VisualBasic to develop a set of Fire-resistance of Steel Structures expert system (ESSFF), the present invention mainly adopts Python that fire calculating, analysis of Heat Transfer and Structure Calculation are integrated in unified calculation environment, research and analyse for beam-post wood frame framework fire-resistance, whole process of calculation analysis is succinctly convenient.

Summary of the invention

Goal of the invention: for the defect of existing investigative technique, the invention provides analytic system and the analytical approach of the overall fire resistance analysis of a kind of beam-post wood frame framework.Considering the impact of actual fire development, take one-piece construction as object, adopts standardized designs flow process, realizes economic timber structure fire protection design scheme reliably.This invention can reduce the high cost of full scale test, improves analysis efficiency.

Technical scheme:

An analytic system for the overall fire resistance of beam-post wood frame framework, is characterized in that, comprising:

Actual fire disaster simulation module, for generating the simulated fire operating mode corresponding with actual fire working in beam-post wood frame framework;

Inside configuration finite element analysis of Heat Transfer module, for obtaining the interior temperature distribution of timber structure under the simulated fire operating mode of described actual fire disaster simulation CMOS macro cell;

Structure field finite element analysis computation module, for loading described timber structure thus obtaining malformation and damage.

Analytic system of the present invention also comprises:

Visualization model, for the malformation that described structure field finite element analysis computation module obtained and damage visual.

An analytical approach for the overall fire resistance of beam-post wood frame framework, is characterized in that, comprise the following steps:

Step one, in finite element analysis software ABAQUS, set up beam-post wood frame frame temperature field and structure field model, the thermal property that wherein temperature field raises along with temperature according to heat transfer principle and timber pyroconductivity, density and specific heat and reduces sets up associated materials attribute, determine by fiery face, setting associated hot radiation coefficient; Finite element model is set up according to finite element theory in structure field;

Step 2, according to locus, the rate of heat release of actual fire thermal source and the ventilation condition that punches, design fire operating mode;

Step 3, fire working according to setting, ins conjunction with the beam-post wood frame frame temperature field model set up, adopt fire disaster simulation software to set up fire disaster simulation model, calculate the thermo parameters method result in change space during conflagration area inner structure surface;

Step 4, thermal-structure coupled finite element analysis is carried out to timber structure: be updated in Temperature calculating using the Calculated Results of Temperature Field becoming space time above-mentioned as thermal boundary condition, by the analysis of Heat Transfer of Finite Element Simulation Software, obtain the temperature results of beam-post wood frame lower portion thermo parameters method result and each finite element unit node;

Step 5, acquired beam-post wood frame lower portion Calculated Results of Temperature Field is updated in structure field model, apply conventional load and boundary condition, calculate beam-post wood frame framework and respond the structure field of malformation and damage in actual fire is by fiery process.

Also comprise step 6, realize the visual of malformation and damage: in finite element analysis software ABAQUS, work out visualization procedure, and the structure field result of calculation that steps for importing five calculates, realize distortion and the damage visualization process of fire process central sill pillar timber structure framework.

Described beam-post wood frame frame temperature field model uses DC3D8 unit in finite element software ABAQUS; Described beam-post wood frame frame temperature field model selects solid element C3D8R to set up in finite element software ABAQUS.

Visualization procedure realizes according to result of finite element: finite element software ABAQUS provides Python interface, by the Python program of establishment, import odbAccess module and extract in finite element structural analysis the result of calculation of specifying iteration step, after result being exported as TXT document format, again establishment read the Python program of these data imported to finish writing based in OPENGL visualization procedure, beam-post wood frame framework can be realized by the distortion in fiery process and damage visual.

The overall fire resistance analysis of beam-post wood frame framework of the present invention research and analyse method, comprise with lower part:

One, in finite element analysis software ABAQUS, beam-post wood frame frame temperature field and structure field model is set up, the thermal property that wherein temperature field raises along with temperature according to heat transfer principle and timber pyroconductivity, density and specific heat and reduces sets up associated materials attribute, determine by fiery face, setting associated hot radiation coefficient; Finite element model is set up according to finite element theory in structure field, and the timber constitutive model subroutine using FORTRAN to compile;

Two, according to actual conditions setting fire location, quantity of flammable substances, HRR, the quantity that punches and size, fire working is determined;

Three, according to finite element model in, use Python Program Generating fire disaster simulation software FDS input file, set up fire entity analogy model, and become space temperature field when calling FDS solver calculating conflagration area inner structure surface, obtain result surface heating curve;

Four, carry out thermal-structure coupled calculating: first Python Calling calculated try to achieve time become space temperature field result data be set to thermal boundary condition, generate ABAQUS thermal analyses original document, call ABAQUS solver and calculate beam-post wood frame lower portion thermo parameters method result; According to acquired structural system finite element temperature field data genaration structure analysis original document, call ABAQUS solver and calculate the structural response of beam-post wood frame framework under conventional load and temperature load effect.

Five, the visual of malformation process under fire effect is carried out: still read structure response results data in the Python program compiled, the malformation walk designated analysis and unit damage data are preserved with document format, read corresponding data by the OPENGL program in Python, use double buffering technology to realize malformation and damage unit from the visualization process being initialised to net result.

Six, the mechanical properties test of structure fire-resistant is carried out: the quantity according to visual deformation process malformation and damage disabling unit judges that structural beams pillar timber structure framework destroys position and whether collapses.

Below that the concrete implementation step of the present invention is described in further detail:

(1) the present invention's program execution architecture fire-resistance analysis of using Python to work out, finite element model, fire disaster simulation model and computing thereof solve, and analyze data processing and the Visual Implementation process is all automatically performed by program.User need input the basic parameters such as corresponding fire working, moulded dimension before computing.

(2) finite element model first set up in finite element analysis software uses entity C3D8R unit, and fire disaster simulation model is determined according to moulded dimension in finite element software.Fire working sets according to actual conditions.

(2) Python program uses pipe control to call software solver to carry out computational analysis calling in finite element analysis software and fire disaster simulation software, software computational analysis can be made like this to be integrated into the unified calculation environment of Python establishment, and computation process is succinctly convenient.

(3) api interface that provides mainly through Python routine call finite element analysis software ABAQUS of visualization process, extract the database file of result of calculation, again by column joints deformation and coordinate data, unit loss amount data repaint in OPENGL, make the deformation process of beam-post wood frame framework under fire effect and lesion development situation visual.

Beneficial effect: compared with current wooden frame fire-resistance analytical technology, the present invention proposes a kind of beam-post wood frame framework fire-resistance analytical approach, fire development in simulated fire evolution, inside configuration heat transfer and structure corresponding, achieve structure in the express-analysis by distortion and lesion development in fiery process, can also realize visual simultaneously.The present invention is based on existing fire disaster simulation and structure analysis software, by the analyzing and processing to input file and analog result file, carry out the data environment that modeling again builds the fire scene of a fire, in conjunction with the timber constitutive model program compiled voluntarily and Python visualization procedure, achieve the process of carrying out beam-post wood frame Frames In Fire structural simulation on a data environment and software platform, the present invention is that building fire research provides numerical experiment method calmly, have fast, cheap, succinct feature, practical value is provided for the design of timber structure fire performance and fire risk assessment.

Accompanying drawing explanation

Fig. 1 is the ingredient of beam-post wood frame framework fire-resistance analytic system of the present invention;

Fig. 2 is the process flow diagram of beam-post wood frame framework fire-resistance analytical approach of the present invention;

Fig. 3 is fire of the present invention design and calculation specifications;

Fig. 4 is the timber constitutive relation that the present invention adopts;

Fig. 5 is the reduction model that the present invention adopts timber under high temperature, and wherein a is the reduction model of modulus of elasticity of wood, and b is the reduction model of strength of wood;

Fig. 6 is visualized data processing flow chart of the present invention;

Fig. 7 is that beam-post wood frame framework of the present invention is by lesion assessment flow process after fire.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.

As shown in Figure 1, the analytic system of the overall fire resistance of a kind of beam-post wood frame framework of the present invention, comprising:

Actual fire disaster simulation module, for generating the simulated fire operating mode corresponding with actual fire working in beam-post wood frame framework;

Inside configuration finite element analysis of Heat Transfer module, for obtaining the interior temperature distribution of timber structure under the simulated fire operating mode of described actual fire disaster simulation CMOS macro cell;

Structure field finite element analysis computation module, for loading described timber structure thus obtaining malformation and damage.

And visualization model, for the malformation that described structure field finite element analysis computation module obtained and damage visual.

The analytical approach of the overall fire resistance of a kind of beam-post wood frame framework of the present invention, as shown in Figure 2, comprises the following steps:

Step one, in finite element analysis software ABAQUS, set up beam-post wood frame frame temperature field and structure field model, the thermal property that wherein temperature field raises along with temperature according to heat transfer principle and timber pyroconductivity, density and specific heat and reduces sets up associated materials attribute, determine by fiery face, setting associated hot radiation coefficient; Finite element model is set up according to finite element theory in structure field;

Step 2, according to locus, the rate of heat release of actual fire thermal source and the ventilation condition that punches, design fire operating mode;

Step 3, fire working according to setting, ins conjunction with the beam-post wood frame frame temperature field model set up, adopt fire disaster simulation software to set up fire disaster simulation model, calculate the thermo parameters method result in change space during conflagration area inner structure surface;

Step 4, thermal-structure coupled finite element analysis is carried out to timber structure: be updated in Temperature calculating using the Calculated Results of Temperature Field becoming space time above-mentioned as thermal boundary condition, by the analysis of Heat Transfer of Finite Element Simulation Software, obtain the temperature results of beam-post wood frame lower portion thermo parameters method result and each finite element unit node;

Step 5, acquired beam-post wood frame lower portion Calculated Results of Temperature Field is updated in structure field model, apply conventional load and boundary condition, calculate beam-post wood frame framework and respond the structure field of malformation and damage in actual fire is by fiery process.

Also comprise step 6, realize the visual of malformation and damage: in finite element analysis software ABAQUS, work out visualization procedure, and the structure field result of calculation that steps for importing five calculates, realize distortion and the damage visualization process of fire process central sill pillar timber structure framework.

The structure of step one finite element model.According to beam column size, vertical load and boundary condition that user inputs in Python program in ABAQUS, set up beam-post wood frame framework finite element model, entity hot cell adopts DC3D8, and entity structure unit adopts C3D8R.

Timber structure is due to himself anisotropic feature, and as shown in Figure 4, timber under a stretching force brittle rupture occurs its constitutive model, and ductile fracture occurs under pressure, draws simultaneously, presses yield strength unequal.X in figure _t, X _cbe respectively timber rift grain tension and compressive yield strength, Y _t, Y _cbe respectively the radial tension of timber band and pressurized yield strength, Z _t, Z _cbe respectively the tangential tension of timber band and compressive yield strength.

Timber is along with the rising of temperature, and charing in various degree occurs, and its intensity, elastic modulus also change thereupon.The present invention adopts Eurcode5 (EC5) dual slope reduction model, as shown in Figure 5.

In consideration wood damage process, first the present invention adopts Yamada-Sun yield criteria to judge whether timber is surrendered, and the evolutionary model set up based on the timber progressive damage of Yamada-Sun yield criteria, consider the feature of timber tension brittle rupture and pressurized ductile fracture simultaneously.The Yamada-Sun yield criteria that the present invention adopts is as follows:

X to: $F=\frac{{{\mathrm{\σ}}_{11}}^2}{X^2}+\frac{{{\mathrm{\σ}}_{12}}^2}{{S_{XY}}^2}+\frac{{{\mathrm{\σ}}_{31}}^2}{{S_{ZX}}^2}\≤1$

Y-direction: $F=\frac{{{\mathrm{\σ}}_{22}}^2}{Y^2}+\frac{{{\mathrm{\σ}}_{12}}^2}{{S_{XY}}^2}+\frac{{{\mathrm{\σ}}_{32}}^2}{{S_{YZ}}^2}\≤1$

Z-direction: $F=\frac{{{\mathrm{\σ}}_{33}}^2}{Z^2}+\frac{{{\mathrm{\σ}}_{31}}^2}{{S_{ZX}}^2}+\frac{{{\mathrm{\σ}}_{23}}^2}{{S_{YZ}}^2}\≤1$

In formula: F is yield function, X, Y and Z represent three axial tensions of normal stress or compressive strength respectively, σ ₁₁, σ ₂₂and σ ₃₃be respectively and draw accordingly or compressive stress; S _ijfor the shearing strength in i – j plane.The present invention sets:

Once the yield function F in formula is greater than 1, then timber starts to enter injury stage.The present invention is in order to represent that timber extent of damage in damage development process introduces the damage variable d in three directions _i.Wherein damage variable is an amount progressively added up, and this considers that timber cannot recover after impaired automatically.D _ibe one between 0 to 1 number.Work as d _iwhen being 0, represent timber not damaged; Work as d _iwhen being 1, represent that timber damages completely.Consider above-mentioned timber constitutive model, reduction model and Yamada-Sun yield criteria under high temperature, the present invention uses formula translation establishment to meet rational ABAQUS subroutine.

2, the design of fire working.According to fire location, quantity of flammable substances, HRR, the quantity that punches and size in actual fire, determine fire scale.The material calorific value numerical value that China specification CECS200 provides is as shown in table 1-1.

Table 1-1 material combustion calorific value

After the combustion heat value obtaining various material, namely statistical computation is carried out to combustible in building, show that fire load is:

Q _L＝ΣmH _u

In formula

Q _l---fire load (MJ);

The quality (kg) of m---combustible;

H _u---the combustion heat value (MJ/kg) of combustible.

Fire load density is defined as the ratio of the feature reference area in total amount of heat and the room produced when indoor all combustible materials burn completely.The feature reference area in room generally adopts the floor area in room.The present invention adopts the fire load density of the floor area in room to be expressed as:

q _f＝Q _L/A _f

In formula

Q _f---fire load density (MJ/m ²);

A _f---room floors area (m ²).

The floor area fire load density based on room that China specification CECS200 provides is as shown in following table 2-2.In practical application, can the rank of safe coefficient as required, select mean value or different tantiles.S.I biogas engine density in table only takes into account movable S.I biogas engine, as clothing, furniture and books etc., does not comprise the fixed S.I biogas engine such as flammable wallpaper, furred ceiling and ground.If have fixed S.I biogas engine in building, need additionally count.

The fire load density of all kinds of building in table 1-2 Chinese regulations CECS200

Note: the fire load density in all kinds of warehouse should be estimated according to practical use

3, according to the fire working set, automatically set up FDS fire disaster simulation model in Python program in conjunction with finite element program moulded dimension and fire parameter, call FDS solver and carry out the time varying temperature field result that analytical calculation obtains conflagration area inner structure surface.

When setting up fire dynamics model adopting FDS calculating and submit calculating to, its basic step comprises following content:

Mass-conservation equation

$\frac{\∂\mathrm{\ρ}}{\∂t}+\▿\mathrm{\ρu}=0---\left(2.1\right)$

Momentum conservation equation

$\frac{\∂}{\∂t}\left(\mathrm{\ρu}\right)+\▿\mathrm{\ρuu}+\▿p=\mathrm{\ρg}+f_b+\▿{\mathrm{\τ}}_{\mathrm{ij}}---\left(2.2\right)$

Energy conservation equation

State equation

$p=\frac{\mathrm{\ρ}RT}{M}---\left(2.4\right)$

In formula

ρ---gas density;

U---velocity.

P---pressure;

F _b---external force vector;

τ _ij---stress tensor.

R---ideal gas constant;

M---gaseous mixture molecular weight.

H _s---sensible enthalpy;

Q ^///---unit volume HRR;

Q _b ^///---the energy of drop evaporation transfer;

Q ^//---thermal flux vector;

θ---dissipative function.

FDS solves and mainly submits job order to by designator window, and the program in the present invention is called cmd order by pipeline control module and submitted to job tasks carrying to calculate.After calculating completes, FDS can generate the time varying temperature data on conflagration area inner structure surface.This result is as the thermal boundary condition of next step finite element analysis of Heat Transfer.

4, thermal-structural coupling analysis: the space temperature field data that FDS fire disaster simulation obtains by Program of the present invention imports in ABAQUS finite element thermal analysis as thermal boundary condition, in conjunction with the thermal analyses finite element model set up, generate corresponding calculation document, concrete implementation step is as follows:

(1) thermal analyses type, boundary condition, thermal convection and the coefficient of heat convection is defined;

(2) read in the form document that FDS fire disaster simulation result generates, fire disaster simulation is obtained time become space temperature field result and be applied in thermal analyses finite element model as boundary condition.ABAQUS can submit job task to by designator form when carrying out solving calculating, and the present invention submits task to by routine call ABAQUS designator and calculates, and obtains the thermo parameters method data result of component inside thus.

(3) according to ABAQUS finite element temperature field result of calculation in (2), in conjunction with the structure field finite element model set up, generate new calculation document, call the structure of ABAQUS solver calculating beam-post wood frame framework under temperature load and conventional load effect corresponding.

5, calculating ODB destination file is extracted, realize visual in OPENGL: ABAQUS provides the api interface of Python, the ABAQUS structure field analysis result ODB file that the present invention has been calculated by Python routine call, extract the column joints deformation of designated analysis iteration step, coordinate and unit loss amount data, these data are read in OPENGL visualization procedure with array form, as shown in Figure 6, visual by distortion in fiery process and damage and failure of structure is realized thus.After calculating completes, the present invention's flow process according to Fig. 7 carries out safety evaluation to concrete on fire structure.

It is more than the description to specific implementation method of the present invention.The present invention is not limited to the embodiment of above-mentioned certain scenarios, and those skilled in the art can carry out adjusting and improving according to actual fire condition and structure type within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (6)

1. an analytic system for the overall fire resistance of beam-post wood frame framework, is characterized in that, comprising:

Actual fire disaster simulation module, for generating the simulated fire operating mode corresponding with actual fire working in beam-post wood frame framework;

Inside configuration finite element analysis of Heat Transfer module, for obtaining the interior temperature distribution of timber structure under the simulated fire operating mode of described actual fire disaster simulation CMOS macro cell;

Structure field finite element analysis computation module, for loading described timber structure thus obtaining malformation and damage.

2. analytic system according to claim 1, is characterized in that, also comprises:

Visualization model, for the malformation that described structure field finite element analysis computation module obtained and damage visual.

3. an analytical approach for the overall fire resistance of beam-post wood frame framework, is characterized in that, comprise the following steps:

Step one, in finite element analysis software ABAQUS, set up beam-post wood frame frame temperature field and structure field model, the thermal property that wherein temperature field raises along with temperature according to heat transfer principle and timber pyroconductivity, density and specific heat and reduces sets up associated materials attribute, determine by fiery face, setting associated hot radiation coefficient; Finite element model is set up according to finite element theory in structure field;

Step 2, according to locus, the rate of heat release of actual fire thermal source and the ventilation condition that punches, design fire operating mode;

Step 3, fire working according to setting, ins conjunction with the beam-post wood frame frame temperature field model set up, adopt fire disaster simulation software to set up fire disaster simulation model, calculate the thermo parameters method result in change space during conflagration area inner structure surface;

Step 4, thermal-structure coupled finite element analysis is carried out to timber structure: be updated in Temperature calculating using the Calculated Results of Temperature Field becoming space time above-mentioned as thermal boundary condition, by the analysis of Heat Transfer of Finite Element Simulation Software, obtain the temperature results of beam-post wood frame lower portion thermo parameters method result and each finite element unit node;

Step 5, acquired beam-post wood frame lower portion Calculated Results of Temperature Field is updated in structure field model, apply conventional load and boundary condition, calculate beam-post wood frame framework and respond the structure field of malformation and damage in actual fire is by fiery process.

4. analytical approach according to claim 3, is characterized in that, also comprises:

Step 6, realize the visual of malformation and damage: in finite element analysis software ABAQUS, work out visualization procedure, and the structure field result of calculation that steps for importing five calculates, realize distortion and the damage visualization process of fire process central sill pillar timber structure framework.

5. analytical approach according to claim 3, is characterized in that: described beam-post wood frame frame temperature field model uses DC3D8 unit in finite element software ABAQUS;

Described beam-post wood frame frame temperature field model selects solid element C3D8R to set up in finite element software ABAQUS.

6. analytical approach according to claim 3, it is characterized in that: visualization procedure realizes according to result of finite element: finite element software ABAQUS provides Python interface, by the Python program of establishment, import odbAccess module and extract in finite element structural analysis the result of calculation of specifying iteration step, after result being exported as TXT document format, again establishment read the Python program of these data imported to finish writing based in OPENGL visualization procedure, beam-post wood frame framework can be realized by the distortion in fiery process and damage visual.