Method for determining residual cross section of wood-bamboo component after combustion by considering cracking influence

Abstract

The invention discloses a method for determining a residual cross section of a wood-bamboo component after combustion by considering cracking influence. The method comprises the following steps: S1, measuring the size of a surface crack of the wood-bamboo component and the position of the surface crack on the cross section; s2, the carbonization depth of the non-cracking wood-bamboo component is calculated, and the width and height of the remaining section of the non-cracking wood-bamboo component after combustion are determined according to the fire surface; s3, determining the crack width and depth after combustion; and S4, according to the crack distribution after combustion and the residual section after combustion of the non-cracked wood-bamboo component, determining the residual section after combustion of the wood-bamboo component considering the cracking influence. According to the method, the influence of cracking on the residual cross section after combustion of the wood-bamboo component is considered, and compared with an existing method for determining the residual cross section after combustion in which only the non-cracked cross section is considered, the calculation precision is higher. By means of the method, the section parameters of the wood-bamboo component after fire combustion can be more accurately estimated, so that designers can accurately evaluate the fire resistance of the wood-bamboo component, and building designers can conveniently optimize structural design.

Description

Technical Field

[0001] The invention relates to the field of construction, and in particular to a method for determining the remaining cross-section of a wood or bamboo component after combustion taking into account the influence of cracking. Background Art

[0002] Since wood and bamboo are biomass materials, they are affected by external temperature and humidity during processing, manufacturing and use, and the moisture content or dryness degree of each part of the wood and bamboo materials is different, resulting in inconsistent internal and external shrinkage of the wood and bamboo fibers. The wood and bamboo fibers separate from each other longitudinally to produce longitudinal shrinkage cracks. As time goes by, the mechanical properties of the wood material will decrease under the action of external loads, causing the original shrinkage cracks to continue to deepen and widen under the action of external forces, becoming a hidden danger affecting the safety performance of the components and the entire structure.

[0003] Wood and bamboo are solid combustible materials. When the surface temperature of wood and bamboo reaches 200-400℃, they ignite and gradually form a carbonized layer. The carbonized layer has almost no strength, while the mechanical properties of the normal internal area are less affected by the fire. Therefore, in the fire-resistant design of wood and bamboo structures, the residual cross-section method is usually used to calculate the residual bearing capacity of wood and bamboo components during and after the fire. Therefore, the remaining cross-section of wood and bamboo components after burning is an important parameter for determining the fire resistance of wood and bamboo structures. When the wood structure is exposed to fire, the cracking of the components increases the area of ​​wood exposed to the open flame, which will accelerate the carbonization of the wood. At present, there is only a method to determine the remaining cross-section of uncracked wood and bamboo components after burning, and there is no method to determine the remaining cross-section of wood and bamboo components after burning that takes into account the influence of cracking. Summary of the invention

[0004] In view of the above defects and shortcomings of the prior art, the present invention aims to propose a scientific, accurate and effective method for determining the remaining cross-section of wood and bamboo components after combustion that takes into account the influence of cracking. This calculation method can be applied to determine the remaining cross-section of cracked wood and bamboo components, laying a theoretical foundation for the fire performance evaluation of cracked wood and bamboo structures.

[0005] To achieve the above objectives, the present invention provides a method for determining the remaining cross-section of a wood or bamboo component after combustion taking into account the influence of cracking, which comprises the following steps:

[0006] S1: Measure the size and cross-sectional location of cracks on the surface of wood and bamboo components;

[0007] S2: Calculate the carbonization depth of the uncracked wood and bamboo components, and determine the remaining cross-sectional width and height of the uncracked wood and bamboo components after combustion based on the fire-exposed surface;

[0008] S3: Determine crack width and depth after burning;

[0009] S4: Based on the crack distribution after combustion and the remaining cross-section of uncracked wood and bamboo components after combustion, determine the remaining cross-section of wood and bamboo components after combustion taking into account the influence of cracking.

[0010] A further improvement of the present invention is that in step S1, the width, depth and distribution position of the cracks on the surface of the wood or bamboo component are measured and recorded one by one.

[0011] A further improvement of the present invention is that in step S2, the carbonization depth d of the uncracked wood and bamboo components is n The expression is:

[0012] d n =β n t 0.813

[0013] where β n is the carbonization rate, t is the fire exposure time;

[0014] The calculation formula for the remaining section width is b(t) = b-c1d n , the calculation formula for the remaining section height is h(t) = h-c2d n , where c1 and c2 are determined according to the number of surfaces affected by fire. If two surfaces in this direction are affected by fire, the value is 2, otherwise the value is 1.

[0015] A further improvement of the present invention is that in step S2, β n According to the types of wood and bamboo, a further improvement of the present invention is that step S3 specifically includes:

[0016] The width of the crack on the fire-exposed surface increases by 0.3d on both sides. n , but not exceeding the remaining size of the cross section after carbonization in that direction, so as to determine the crack width after combustion;

[0017] The crack depth on the fire-exposed surface increases by d n , to determine the crack width after burning, but not exceeding the remaining size of the cross section after carbonization in that direction;

[0018] The crack depth after burning is d(t) = d. After burning, the surface position of the wood and bamboo components changes due to carbonization. The expression of the crack width after burning is:

[0019] The advantages of the present invention are as follows: the present invention takes into account the influence of cracking on the remaining cross-section of the wood and bamboo components after combustion, and has a higher calculation accuracy than the existing method for determining the remaining cross-section after combustion that only considers the uncracked cross-section. Through the method of the present invention, the cross-sectional parameters of the wood and bamboo components after fire can be estimated more accurately, so that designers can accurately evaluate the fire resistance of the wood and bamboo components, which is convenient for architectural designers to optimize the design and improve the fire resistance of the building. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flowchart of a method for determining the remaining cross-section of a wood or bamboo component after combustion taking into account the influence of cracking according to an embodiment of the present invention.

[0021] Figure 2 The diagram is a schematic diagram of the remaining cross-section of a rectangular cracked wooden beam when three sides are exposed to fire in a method for determining the remaining cross-section of a wooden or bamboo component after combustion taking into account the influence of cracking according to an embodiment of the present invention.

[0022] Figure 3 The diagram is a schematic diagram of the remaining cross-section of a circular cracked wooden column when four sides are exposed to fire in a method for determining the remaining cross-section of a wooden or bamboo component after combustion taking into account the influence of cracking according to an embodiment of the present invention.

[0023] Figure 4 It is a schematic diagram of the remaining cross-section of a square cracked glued bamboo column when four sides are exposed to fire in a method for determining the remaining cross-section of a wood-bamboo component after combustion taking into account the influence of cracking according to an embodiment of the present invention.

[0024] Wherein, the accompanying drawings are marked as follows:

[0025] 1——Carbonized layer,

[0026] 2——Cracks on the bottom surface of the beam before combustion,

[0027] 3——Cracks on the bottom surface of the beam after burning,

[0028] 4——Before burning, cracks on the side of the beam,

[0029] 5——Cracks on the side of the beam after burning,

[0030] 6——Remaining cross section after combustion. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] While some exemplary embodiments of the present invention have been described for the purpose of illustration, it should be understood that the present invention may be implemented in other ways not specifically shown in the drawings.

[0033] Embodiment 1:

[0034] The present invention is described in detail below in conjunction with specific embodiments. Figure 2Take the cracked wooden beam shown in the figure as an example. For a historical building with a wooden structure, the cross-sectional size of the wooden beam is 200mm×300mm. The wooden beam is exposed to fire on three sides for 1 hour. n =38mm / h.

[0035] according to Figure 1 The calculation steps of the remaining cross section after combustion are as follows:

[0036] Step S1: measuring the size of cracks on the surface of the wood and bamboo component and their locations on the cross section;

[0037] There is a crack in the mid-span section at the bottom of the beam. After measurement, the width of the crack 2 at the bottom of the beam is 15mm and the depth is 80mm.

[0038] Step S2: Calculate the carbonization depth d of the uncracked wood and bamboo components n =β n t 0.813 , where β n is the carbonization rate, t is the fire exposure time;

[0039] d n =β n t 0.813 =38mm

[0040] Determine the remaining cross-section of the uncracked wood and bamboo component after combustion, deduct 1 times the carbonization depth from each fire-exposed surface and change the rectangular cross-section corners into arcs. In this step, the wood and bamboo component is taken as the uncracked wood and bamboo component, the purpose is to determine the thickness of the carbonized layer, so as to determine the main contour of the remaining cross-section of the wood and bamboo component after combustion.

[0041] Step S3: Determine the width and depth of the crack after combustion. The width of the crack on the fire surface is increased by 0.3d on both sides. n =11.4mm, but not exceeding the remaining size of the cross section after carbonization in that direction; the crack depth on the fire-exposed surface increases by d n =38mm, but not exceeding the remaining size of the cross section after carbonization in this direction, the crack width after burning is 37.8mm, and the crack depth after burning is 118mm;

[0042] Step S4: Based on the distribution of cracks after burning 3 and the remaining cross section of the uncracked wood and bamboo components after burning, the remaining cross section of the wood and bamboo components after burning considering the influence of cracking is comprehensively determined. In the process of determining the remaining cross section after burning, the position, depth and width of the cracks after burning can be determined through step S3; the original contour of the wood and bamboo components minus the carbonization thickness can be used to obtain the contour of the remaining cross section. The remaining cross section of the wood and bamboo components after burning can be determined by comprehensively considering the remaining cross section contour, the position, depth and width of the cracks after burning.

[0043] Embodiment 2:

[0044] The present invention will be further described below in conjunction with specific embodiments. Figure 3 Take the cracked wooden column shown in the figure as an example. In a historical building wooden structure, the cross-sectional size of the round wooden column is 300mm in diameter. The wooden column is exposed to fire on all four sides. After being exposed to fire for 1 hour, β n =38mm / h.

[0045] according to Figure 1 The calculation steps of the remaining cross section after combustion are as follows:

[0046] Step S1: measuring the size of cracks on the surface of the wood and bamboo component and their locations on the cross section;

[0047] There is a crack in the column section located on the side of the column. After measurement, the width of crack 2 is 15mm and the depth is 80mm.

[0048] Step S2: Calculate the carbonization depth d of the uncracked wood and bamboo components n =β n t 0.813 , where β n is the carbonization rate, t is the fire exposure time;

[0049] d n =β n t 0.813 =38mm

[0050] Determine the remaining cross-section of uncracked wood and bamboo components after burning, and deduct twice the carbonization depth from the diameter of the remaining cross-section after burning.

[0051] Step S3: Determine the width and depth of the crack after combustion. The width of the crack on the fire surface is increased by 0.3d on both sides. n =11.4mm, but not exceeding the remaining size of the cross section after carbonization in that direction; the crack depth on the fire-exposed surface increases by d n =38mm, but not exceeding the remaining size of the cross section after carbonization in this direction, the crack width after burning is 37.8mm, and the crack depth after burning is 118mm;

[0052] Step S4: Based on the crack distribution 3 after combustion and the remaining cross-section of the uncracked wood and bamboo member after combustion, comprehensively determine the remaining cross-section 4 of the wood and bamboo member after combustion taking into account the influence of cracking.

[0053] Embodiment 3:

[0054] The present invention will be further described below in conjunction with specific embodiments. Figure 4 The cracked glued bamboo column shown in the figure is taken as an example. In a glued bamboo structure, the cross-sectional size of the glued bamboo column is 300mm×300mm. The glued bamboo column is exposed to fire on three sides for 1 hour. n =54mm / h.

[0055] according to Figure 1 The calculation steps of the remaining cross section after combustion are as follows:

[0056] Step S1: measuring the size of cracks on the surface of the wood and bamboo component and their locations on the cross section;

[0057] There is a crack on the side of the column section. After measurement, the width of the crack 2 on the side is 15mm and the depth is 50mm.

[0058] Step S2: Calculate the carbonization depth d of the uncracked wood and bamboo components n =β n t 0.813 , where β n is the carbonization rate, t is the fire exposure time;

[0059] d n =β n t 0.813 =54mm

[0060] Determine the remaining cross-section of uncracked wood and bamboo components after combustion. Deduct 1 times the carbonization depth from each fire-exposed surface and change the corners of the rectangular cross-section into arcs.

[0061] Step S3: Determine the width and depth of the crack after combustion. The width of the crack on the fire surface is increased by 0.3d on both sides. n =16.2mm, but not exceeding the remaining size of the cross section after carbonization in that direction; the crack depth on the fire-exposed surface increases by d n =54mm, but not exceeding the remaining size of the cross section after carbonization in this direction, the crack width after burning is 47.4mm, and the crack depth after burning is 104mm;

[0062] Step S4: Based on the crack distribution 3 after combustion and the remaining cross-section of the uncracked wood and bamboo member after combustion, comprehensively determine the remaining cross-section 4 of the wood and bamboo member after combustion taking into account the influence of cracking.

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for determining the remaining cross-section of a wood or bamboo component after combustion taking into account the effect of cracking, characterized in that: The following steps are involved: S1: Measure the size and cross-sectional location of cracks on the surface of wood and bamboo components; S2: Calculate the carbonization depth of the uncracked wood and bamboo components, and determine the remaining cross-sectional width and height of the uncracked wood and bamboo components after combustion based on the fire-exposed surface; S3: Determine crack width and depth after burning; S4: Based on the crack distribution after combustion and the remaining cross-section of uncracked wood and bamboo components after combustion, determine the remaining cross-section of wood and bamboo components after combustion taking into account the influence of cracking.

2. A method for determining the remaining cross-section of a wood or bamboo component after combustion taking into account the effect of cracking according to claim 1, characterized in that: In step S1, the width, depth and distribution position of the cracks on the surface of the wood and bamboo components are measured and recorded one by one.

3. A method for determining the remaining cross-section of a wood or bamboo component after combustion considering the effect of cracking according to claim 1, characterized in that: In step S2, the carbonization depth d of the uncracked wood and bamboo components is n The expression is: d n =b n t 0.813 where β n is the carbonization rate, t is the fire exposure time; The calculation formula for the remaining section width is b(t) = b-c1d n , the calculation formula for the remaining section height is h(t) = h-c2d n , where c1 and c2 are determined according to the number of surfaces affected by fire. If two surfaces in this direction are affected by fire, the value is 2, otherwise the value is 1.

4. A method for determining the remaining cross-section of a wood or bamboo component after combustion considering the effect of cracking according to claim 3, characterized in that: In step S2, β n Determined by the type of wood and bamboo.

5. A method for determining the remaining cross-section of a wood or bamboo component after combustion considering the effect of cracking according to claim 3, characterized in that: Step S3 specifically includes: The width of the crack on the fire-exposed surface increases by 0.3d on both sides. n , but not exceeding the remaining size of the cross section after carbonization in that direction, so as to determine the crack width after combustion; The crack depth on the fire-exposed surface increases by d n , to determine the crack width after burning, but not exceeding the remaining size of the cross section after carbonization in that direction; After burning, the crack depth d(t) = d, width

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