JP2010275792A - Method for verifying non-damage property of wooden framework member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for verifying non-damage property of a wooden framework member that can efficiently verify a non-damage property in high accuracy only through a small-scale combustion test on a test piece of wood constituting the wooden framework member. <P>SOLUTION: The method for verifying non-damage property after the combustion of a column constituting a wooden bearing wall, for instance, as the wooden framework member, includes: conducting a heating experiment on wood of a raw material of the wooden framework member to acquire beforehand the discolored condition of the wood at a predetermined temperature and to acquire beforehand the correlation between the rise of internal temperature and a fall in structure yield strength in the wood of the raw material; performing the combustion test on the test piece of wood constituting the wooden framework member, and then removing a carbonized portion in the predetermined cross section of the test piece while setting a temperature rise range from the discolored portion of the measured wood; and verifying the non-damage property after combustion of the wooden framework member in consideration of the fall in structure yield strength due to the rise of internal temperature from the correlation between the rise of internal temperature and the fall in structure yield strength. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for verifying non-damage of a wooden frame member, and more particularly, to a method for verifying non-damage of a wooden frame member for verifying non-damage after burning of a wooden frame member such as a column or a beam.

  When the surface of wood is ignited and carbonized, a carbonized layer is formed in the combustion part. This carbonized layer is provided with a heat insulating property that blocks the supply of oxygen necessary for burning wood and protects a healthy portion inside the carbonized layer from high-temperature heating. In addition, the thermal conductivity of wood itself is as small as about 1/10 of that of concrete, and wood contains a considerable amount of water even in an air-dried state. It will take a considerable amount of time.

  Furthermore, wood has been found to vary such that when its surface is subjected to constant heating, the internal temperature rise decreases from the surface side toward the center side, and as the internal temperature rises, It has also been found that the structural yield strength decreases (for example, see Non-Patent Document 1).

  On the other hand, for example, the fireproof performance of a wooden bearing wall is evaluated by, for example, heat-resistant heating in a state where a predetermined load is loaded on a test wall having a height of one floor, and for a predetermined time, heat-shielding property, flame-proofing property and Although it is conducted by checking whether the non-damage property does not exceed the respective allowable limits (full-scale load heating test), the area where facilities for performing such a fire-resistant heating test can be established is limited. In addition, since the burden of the cost and labor is large, it is desired that the fireproof performance can be effectively predicted by a small experiment or calculation.

  And, for example, the fireproof performance of the wall of a timber framed wooden building is generally considered to be governed by non-damage properties among heat insulation, flame proofing and non-damage, and for example, a timber frame true wall Since it is considered that the non-damaging property of the steel is governed by the buckling of the column due to flame heating, a method for predicting the fireproof performance by a compression test using only the column as a specimen is conceivable. As such a method, for example, a specimen of a column that reproduces the mechanical state after fire-resistant heating, which is expected for non-damage during fire-resistant heating of a wooden wall, is prepared, and obtained by a compression experiment on the created specimen. From the obtained results, a method for predicting the buckling load of a true wall column for 30 minutes for fire prevention and 45 minutes for quasi-fire resistance is proposed by applying a certain coefficient to the buckling load formula of Euler. (For example, refer nonpatent literature 1).

"Fireproof design of wooden buildings" by Nakamura Ryoichi and Makoto Yamada, published in October 1998 “Prediction of fireproof performance of wooden wall” Mariko Shimizu et al., Architectural Institute of Japan, 611 P165-170, January 2007, published by Architectural Institute of Japan

  However, in the prediction of the fire resistance of the wooden wall of Non-Patent Document 2, for example, assuming that the carbonization depth of 45 minutes after heating is 30 mm, the cross section corresponding to the carbonization depth is cut from the three directions of the heating surface front and both side surfaces. The temperature distribution inside the burning column is set for each depth from the charring end (the outermost part on the non-carbonized heating side), and the Young's modulus in each range surrounded by the set temperature distribution isotherm By replacing the remaining rate with the decrease in the cross-sectional area of each cross section, the cross section of the test specimen is designed assuming that the column is burned. However, if there is a burning in the column that is different from what is assumed in the actual full-scale load heating test, it is judged whether the prediction is correct, whether the test result is acceptable or not. hard. In addition, when assuming the state of incineration during refractory heating at the beginning of the calculation, it was usual to simplify the carbonization position and temperature rise position and set it to the disadvantaged model for safety reasons. It was difficult to understand the actual ability value of the sensor, and it was difficult to accurately verify the non-damage.

  The present invention can efficiently verify non-damage with high accuracy by performing a small-scale combustion test on a wood specimen constituting a wooden frame member without performing a full-scale load heating test. An object of the present invention is to provide a non-damage verification method for a wooden frame member.

  The present invention relates to a non-damage verification method for a wooden frame member for verifying the non-damage after burning of a wooden frame member such as a column or a beam, and is a method for verifying the timber of the raw material of the wooden frame member. The heat dissipating experiment was conducted in advance to grasp the discoloration status of the wood at a predetermined temperature in advance, and the correlation between the increase in internal temperature and the decrease in structural strength in the wood of the raw material of the wooden frame member was grasped in advance. In addition, after performing a combustion test on the wood specimen constituting the wooden frame member, in the predetermined cross section of the specimen, the carbonized portion is removed and the temperature increase range is set from the measured discolored portion of the wood. And providing a non-damage verification method for a wooden frame member that verifies the non-damage property of the wooden frame member after combustion in consideration of a decrease in structural strength due to an increase in internal temperature from the correlation. Achieves the above objectives .

  In the method for verifying non-damage of a wooden frame member according to the present invention, the wooden frame member whose non-damage property after combustion is verified is a column, and the structural strength that decreases as the internal temperature increases is The yield strength is preferred.

  In the non-damage verification method for a wooden frame member according to the present invention, the raw material of the wooden frame member is preferably cypress, cedar, bay pine, or SFP (Spruce Pine Fur).

  According to the non-damage verification method of the wooden frame member of the present invention, the accuracy can be obtained only by performing a small-scale combustion test on the wood specimen constituting the wooden frame member without performing a full-scale load heating test. It is possible to efficiently verify the good non-damage.

It is a chart explaining the correlation with the raise of the internal temperature in the wood of the raw material of a wooden frame member, and the fall of structural yield strength (residual yield strength). It is a flowchart explaining the procedure which verifies the non-damage property of a wooden frame member from the test body after combustion. (A) is a partially broken front view, (b) is a vertical cross-sectional view, and (c) is a horizontal cross-sectional view of a test wall body used in a full-scale load heating test in Examples. (A)-(c) demonstrates the condition which verifies undamaged by the verification method of this invention by making into a test body the pillar after combustion in the wall for a test used for the full-scale load heating test in the Example. FIG. 4 is a cross-sectional view and an equivalent cross-sectional view of a portion A in FIG.

  A non-damage verification method for a wooden frame member according to a preferred embodiment of the present invention is a load that supports a building even when subjected to fire heating, for example, a pillar constituting a wooden bearing wall as a wooden frame member. It was adopted as a method for verifying non-damage, which is a performance that resists deformation and does not cause deformation, melting, destruction, or other damage that hinders structural strength. That is, for example, the evaluation of the fireproof performance of a wooden wall bearing a wall made of pillars is considered to be governed by the non-damage of heat barrier, flame barrier and non-damage. Since the non-damage of the wooden bearing wall is considered to be governed by the buckling of the column due to flame heating, the buckling expected after the fire heating based on the Euler's buckling load formula of the above formula (1) By calculating the bending load, the non-damage of the wooden frame member is verified.

  Further, the non-damage verification method of the wooden frame member according to the present embodiment performs a combustion test on the wood specimen constituting the wooden frame member, and from the burning, carbonization, and discoloration state in the actually remaining cross section. By determining the temperature distribution and strength distribution, the actual residual strength including these effects can be applied to non-damaged sections even when irregular burning occurs due to knot holes, dry cracks, and various other factors. It is possible to verify the accuracy with high accuracy.

  And the non-damage verification method of the wooden frame member of this embodiment is a verification method for verifying the non-damage after burning of a pillar constituting a wooden bearing wall, for example, as a wooden frame member. Then, by conducting a heating experiment on the raw material wood of the wooden frame member, grasping the discoloration status of the wood at a predetermined temperature in advance, the internal temperature rise and structure of the wooden frame member raw material The correlation with the decrease in proof stress is grasped in advance, and after performing a combustion test on a wood specimen constituting a wooden frame member, the carbonized portion is removed and measured in a predetermined cross section of the specimen. After setting the temperature rise range from the discolored part of wood, considering the decrease in structural strength due to the increase in internal temperature from the correlation between the increase in internal temperature and the decrease in structural strength described above, I will verify the non-damage of It has become.

  Moreover, in this embodiment, since the wooden frame member is a column, the non-damage property is verified through the buckling strength as the structural strength that decreases as the internal temperature increases.

  In this embodiment, prior to performing a combustion test on a wood specimen constituting a pillar, a heating experiment is performed on the raw material wood of the pillar, and the discoloration state of the wood at a predetermined temperature is grasped in advance. deep. That is, cypress, cedar, bay pine, or SFP is preferably cut as a discoloration test piece having a width of about 105 mm, a thickness of 52 mm, and a length of about 500 mm, for example, and placed inside an electric furnace. For example, at a temperature of 100 ° C., 150 ° C., 180 ° C., 220 ° C., and 250 ° C., for example, after heating and discoloration for about 2 to 7 hours until the heating temperature and the wood temperature become equal, the color is taken out from the electric furnace. . These taken-out discoloration test specimens are used as color samples for setting the temperature rise range from the discoloration portion in a predetermined cross section of the test specimen after performing a combustion test described later.

  Further, in the present embodiment, prior to performing a combustion test on a specimen of wood constituting the pillar, an increase in internal temperature in the wood of the pillar raw material and a factor of structural strength, for example, a decrease in Young's modulus Is previously known. The correlation between the increase in internal temperature and the decrease in Young's modulus in wood can be easily grasped from, for example, the content described in Non-Patent Document 1 described above. For example, from the results of the elastic modulus (Young's modulus) and the residual rate of fracture load (%) described in Table 3-3 on page 40 of Non-Patent Document 1 above, the internal temperature and residual proof stress as shown in FIG. And get a relationship.

  1 can be drawn from the relationship between the internal temperature and the residual proof stress shown in FIG. 1, and the relationship between the cross-sectional position and Young's modulus as shown in Table 1 can be obtained. Can do.

  Furthermore, in this embodiment, for example, standard heating by ISO834 assuming actual fire heating, etc., for a test body having a quadrangular columnar shape having a size of about 105 mm in length and width, and about 500 to 3500 mm in length, made of wood constituting the column. From the predetermined remaining cross section of the specimen after combustion according to the procedure of the method for verifying non-damage from the remaining cross section shown in FIG. Verify the non-damage of the column.

  That is, in STEP 1, after collecting the cross section of the portion to be verified in the test specimen after combustion, in STEP 2, the carbonized portion of the collected cross section (the portion that easily peels off in black) and the discolored portion (not carbonized, A healthy part and a part where a color difference is recognized.According to the color sample by the above-mentioned discoloration test specimen, for example, discoloration that can be visually discerned occurs in the range of about 150 to 180 ° C., and often has a yellow or brown color. ), And using these as a clue, set the temperature rise range and set the temperature distribution.

  Here, according to the above-mentioned Non-Patent Document 1, the situation of variation in internal temperature when wood is heated for a certain period of time is known, and for example, the heating according to the standard heating curve of ISO834 is directly received for 30 to 45 minutes. In addition, a temperature increase is recognized within a range of about 30 mm including the discolored portion from the carbonized end (cross-sectional edge where charcoal of the carbonized portion is dropped), and the value becomes larger as it is closer to the carbonized end. By using these data, it is possible to set the temperature increase range according to the separation distance on the basis of the carbonized portion and the discolored portion that can be visually confirmed.

  Next, in STEP 3, the temperature distribution and the strength at high temperature of the wood are collated to set the strength distribution. That is, according to the relationship between the internal temperature and the residual strength shown in FIG. 1 obtained from the non-patent document 1 described above, it is clear that the structural strength of wood decreases as the temperature rises. When combined with the temperature rise range set in step 1, it is possible to set the intensity distribution in the collected cross section.

Furthermore, in STEP 4, the equivalent cross section is calculated by replacing the partial decrease in strength in the sampled cross section with the decrease in cross sectional area and integrating. Here, the strength of the material is generally represented by a stiffness EI using an elastic modulus (Young's modulus) E and a secondary moment of inertia I, and the buckling load equation of Euler's long column is Since it is proportional to EI, non-damage can be assessed by the magnitude of this EI. Rectangular cross-section in the ^{EI = Ebh 3/12 (b} = weak axis direction width, h = strong axis width), and when all the cross-section considered a collection of small rectangular cross-section, the temperature rise in each minute section The decreased E can be replaced by a decrease in the respective cross-sectional areas bh. If the cross-sectional area whose strength has been reduced due to the temperature rise in this way is reduced and integrated, a mechanically equivalent equivalent cross-section can be obtained.

Furthermore, in STEP5, the non-damage property is verified based on the secondary moment of the equivalent cross section. That is, by calculating the second moment I _t of equivalent sectional, can the size and the neutral axis and distance between the loading point, the relationship such as the edge stresses, to evaluate the non-damaging diverse members become. Note that the 30-minute fire structure wooden Makabe granulation or quasi fireproof structure 45 minutes, due to the presence of the prediction equation of the above equation (1), by inputting a I _t to _50% I _k, directly during heating It becomes possible to know the buckling load that can withstand.

  And according to the non-damage verification method of the wooden frame member of the present embodiment having the above-described configuration, a small-scale combustion test is performed on the specimen of wood constituting the pillar without performing the actual large-scale heating test. It is possible to efficiently perform highly accurate non-damage verification simply by performing.

  That is, according to the present embodiment, a heating experiment is performed on the raw material wood of the wooden frame member, the discoloration state of the wood at a predetermined temperature is grasped in advance, and the raw material of the wooden frame member The correlation between the increase in internal temperature and the decrease in structural yield strength is grasped in advance, and after performing a combustion test on a specimen of wood constituting a wooden frame member, a carbonized portion in a predetermined cross section of the specimen In addition, the temperature rise range is set from the measured discolored part of the wood, and the decrease in structural strength due to the increase in internal temperature is taken into account from the correlation between the increase in internal temperature and the decrease in structural strength. Since it is designed to verify the non-damage of the frame members after burning, small-scale burning tests are conducted on the wood specimens that make up the pillars, and the burning, carbonization, and discoloration in the actual remaining cross section are performed. From state By determining the degree distribution and intensity distribution, it is possible to verify the non-damaging accurately.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, a wooden frame member to be verified for non-damage after combustion does not necessarily have to be a pillar of a wall-bearing wooden bearing wall, and may be a wooden frame member such as a column, a beam, or a foundation. . Further, the raw material of the wooden frame member is not necessarily cypress, cedar, bay pine, or SFP, and may be other various kinds of wood.

  Hereinafter, although a non-damage verification method of a wooden frame member of the present invention is explained still in detail by an example, the present invention is not limited to these.

〔Example〕
An actual large-scale heating test was performed on the actual large-scale partition walls shown in FIGS. 3A to 3C, and the post-combustion column was sampled as a specimen to verify non-damage. The outer dimension of the partition wall was H3200 (column only 3230) × W3000 mm, and a 105 mm square column was arranged in the center. A 105 × 75 mm auxiliary material was joined to both sides of the column with an epoxy resin adhesive so as to move together with the column. EWSPF (E95-F315) was used for both the column and the auxiliary material. The walls were finished with a reinforced plasterboard 12.5 mm on both sides, the heating side was fitted with a true wall, and the non-heating side was fitted with a large wall.

As a combustion method, in accordance with “Fireproofing Performance Test / Evaluation Business Method Manual” of the Building Materials Testing Center, overheating according to IS0834 was performed for 45 minutes. The loaded load was set to 27.75 kN (buckling length L = 3230 mm, reference strength Fc = 26.3 N / mm ² ) corresponding to the long-term allowable stress of the column material. The measurement items were the test body temperature and the axial shrinkage, and the post-test column was cut at three different locations to investigate the carbonization and discoloration of the cross section.

As a test result, according to the evaluation items of the following performance evaluation organization, when the flame shielding property, the heat shielding property, and the non-damage property were evaluated, all these specified values were satisfied, and the performance of the semi-refractory structure 45 minutes was confirmed. We were able to. Regarding non-damage, the performance was confirmed from the remaining cross section as described later. In addition, the start time of water injection fire extinguishing was 4 minutes after finishing the heating.
Confirmation of flame shielding property → No flame penetration on the back side Confirmation of heat shielding property → Maximum back surface temperature: 111 ° C (specified value 157 ° C),
Maximum average back surface temperature: 86 ° C (specified value 197 ° C)
Confirmation of non-damage property → Maximum axial shrinkage: 0.45 mm (specified value 32.3 mm),
Shrinkage rate: 0.15 mm / min (specified value 9.69 mm / min)

  As a method for verifying the non-damage from the remaining cross section, FIGS. 4A to 4C show three types of remaining cross-section photographs obtained by cutting the column at different positions after the experiment, and equivalent cross-sectional views obtained from the remaining cross sections. Indicates. When the photograph of FIG. 4 was seen, the part which carbonized and the cross-sectional defect | deletion was clear, and discoloration had arisen in the range inside about 5 mm from the carbonization end. As described above, when subjected to refractory heating for 30 minutes or 45 minutes, a temperature increase due to heat transfer occurs between 30 mm from the carbonization end, and those that have reached 150 to 180 ° C. or more are discolored. It is known that the carbonization proceeds when the temperature reaches 240 to 260 ° C. or more, which is called the ignition temperature of. Based on these considerations, the relationship between the internal temperature of the wood and the residual yield strength shown in FIG. 1 can be combined to approximately set the relationship between the cross-sectional position and the elastic modulus (Young's modulus) as shown in Table 1. It is possible to obtain an equivalent cross-section by substituting the reduction rate of the cross-sectional area with the rate of reduction of the cross-sectional area and integrating them (lower diagrams of FIGS. 4A to 4C).

The equivalent cross section was calculated by adding auxiliary materials that remained firmly attached to the column after combustion. When calculating the pillar and the auxiliary material and the combined moment of inertia of I _t, section A is I _t = 562cm ^4, section B is I _t = 545cm ^4, section A was obtained results that I _t = 449cm ⁴ . This value and other parameters related to buckling that were used during the full-scale test (E = 95 tf / cm ² , L = 3230 mm as a 105 mm square column with strength E95-F315) were used for the fire resistance of the true wall described above. If you enter a prediction equation [1], the buckling load _50% P _k is section a which is expected 34.1KN, section B is 33.0KN, sectional C in 27.2KN, section a and section B is actually The value exceeded the load of 27.75 kN corresponding to the long-term allowable stress level loaded during the test. On the other hand, the section C was 2% lower than the load 27.75 kN corresponding to the long-term allowable stress, but the terminal condition coefficient K in the formula [1] used for the calculation is the average value of the experiment in the cited references. Is taken to be 0.83 and the standard deviation can be read as 0.11. Therefore, it is considered that an error of about 13% may occur in the equation [1] using such K. For this reason, the shortage of the cross-section C is included in the error range, and it can be said that the cross-section necessary for ensuring non-damage is retained.

  By the above method, in the quasi-refractory 45-minute heating, the non-damage property could be verified by calculating the cross-sectional second moment of the equivalent cross section from the remaining cross-section using the set values in Table 1.

Claims (3)

A method for verifying non-damage of a wooden frame member for verifying non-damage after burning of a wooden frame member such as a column or a beam,
Conducting a heating experiment on the wood of the raw material of the wooden frame member, grasping in advance the discoloration status of the wood at a predetermined temperature,
Understand in advance the correlation between the rise in internal temperature and the decline in structural strength in the wood of the raw material of the wooden framework member,
After performing a combustion test on the wood specimen constituting the wooden frame member, in a predetermined cross section of the specimen, the carbonized portion is removed, and the temperature increase range is set from the measured discolored portion of the wood, A non-damage verification method for a wooden frame member that verifies non-damage after burning of the wooden frame member in consideration of a decrease in structural strength due to an increase in internal temperature from the correlation. 2. The non-damage of a wooden frame member according to claim 1, wherein the wooden frame member whose non-damage property after combustion is verified is a column, and the structural strength that decreases as the internal temperature increases is a buckling strength. Method of verification. The method for verifying damage to a wooden frame member according to claim 1 or 2, wherein the raw material of the wooden frame member is cypress, cedar, bay pine, or SFP (Spruce Pine Fur).

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