To investigate the fire endurance of wood beams exposed to three-side fire, we conducted bearing capacity tests of two wood beams and experiments of five wood beams exposed to three-side fire. The finite element softw...To investigate the fire endurance of wood beams exposed to three-side fire, we conducted bearing capacity tests of two wood beams and experiments of five wood beams exposed to three-side fire. The finite element software ANSYS was also used to predict the fire endurance of those beams with the indirect order coupling method. It was found that the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. In the case of a certain load level, the fire endurance is improved if the section size is increased or covered by the fire protection coating. The central deformation increases as the fire duration increases, and the ratio of increase tends to rise. On another note, an increase in the density of wood leads to a rise in the fire endurance of a given beam. From the finite element method (FEM) calculation results, the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. When the load level is greater than 0.5, the fire endurance is significantly reduced, and it does not change significantly when the load level changes. Lastly, for a load level magnitude below 0.5, the fire endurance and load level are proportional to one another.展开更多
In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influ...In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influence of factors such as the number of reinforcement surfaces and the degree of damage.The results indicate that single-sided repaired beams have certain advantages in crack resistance performance,but are more disadvantageous in ultimate bearing capacity,with obvious debonding phenomenon before the end of loading.Compared with single-sided reinforcement,the cracking load of the three-sided reinforced beam increased by an average of 1.85 times,the ultimate bearing capacity increased by an average of 177.5%,and a good UHPC-RC combination effect could be formed,which could work synergistically until the end of loading.The degree of pre damage has a significant impact on the crack resistance performance of reinforced beams,while its impact on the ultimate bearing capacity is relatively limited.When the pre splitting width of the RC beam increases from 0.2 mm to 0.4 mm,the ultimate bearing capacity decreases by 28.33%.展开更多
To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together wit...To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 51178115)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Shanghai Rising-Star Program (Nos. 11QH1402100 and 07QB14031), China
文摘To investigate the fire endurance of wood beams exposed to three-side fire, we conducted bearing capacity tests of two wood beams and experiments of five wood beams exposed to three-side fire. The finite element software ANSYS was also used to predict the fire endurance of those beams with the indirect order coupling method. It was found that the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. In the case of a certain load level, the fire endurance is improved if the section size is increased or covered by the fire protection coating. The central deformation increases as the fire duration increases, and the ratio of increase tends to rise. On another note, an increase in the density of wood leads to a rise in the fire endurance of a given beam. From the finite element method (FEM) calculation results, the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. When the load level is greater than 0.5, the fire endurance is significantly reduced, and it does not change significantly when the load level changes. Lastly, for a load level magnitude below 0.5, the fire endurance and load level are proportional to one another.
文摘In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influence of factors such as the number of reinforcement surfaces and the degree of damage.The results indicate that single-sided repaired beams have certain advantages in crack resistance performance,but are more disadvantageous in ultimate bearing capacity,with obvious debonding phenomenon before the end of loading.Compared with single-sided reinforcement,the cracking load of the three-sided reinforced beam increased by an average of 1.85 times,the ultimate bearing capacity increased by an average of 177.5%,and a good UHPC-RC combination effect could be formed,which could work synergistically until the end of loading.The degree of pre damage has a significant impact on the crack resistance performance of reinforced beams,while its impact on the ultimate bearing capacity is relatively limited.When the pre splitting width of the RC beam increases from 0.2 mm to 0.4 mm,the ultimate bearing capacity decreases by 28.33%.
基金supported by the National Natural Science Foundation of China (Grant No. 51178115)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.
