碳纤维布加固混凝土梁的高温抗弯承载力——影响因素及衰减关系

通过引入混凝土高温等效抗压强度,提出了碳纤维布加固混凝土梁高温抗弯承载力的一种简化计算方法.利用所提方法,考察了防火涂料设置、碳纤维布加固量、受拉钢筋配筋率、混凝土保护层厚度等参数对加固梁高温抗弯承载力的影响规律.在大量分析结果基础上,建立了加固梁高温抗弯承载力随升温时间的定量衰减关系.研究结果表明:(1)利用该简化方法所得加固梁的耐火极限与试验结果吻合较好;(2)实际工程中梁侧防火涂料高度可以90 mm为限,在此范围内加固梁的高温抗弯承载力随着梁侧防火涂料高度的增加逐渐增大;(3)混凝土保护层厚度越小,加固梁抗弯承载力随升温时间增加而降低的速率越大,但升温2 h以后加固梁的抗弯承载力基本按同一速率下降.

Flexural capacity of RC beam strengthened with carbon fiber sheets under high temperature:influence factors and attenuation rule

Using the concept of equivalent compressive strength of concrete at high temperature,a simplified method was proposed for calculation of the flexural capacity of RC beam strengthened with externally bonded carbon fibersheets and subjected to fire.Utilizing the proposed method,the influence of some parameters(e.g.,insulation condition,strengthening ratio,steel ratio,and thickness of concrete cover)on the flexural capacity of the strength-ened beam in fire was discussed.Based on extensive parametric analysis,a regressive formula was suggested for the relationship between the flexural capacity of the stengthened beam and the heating time.Simulation results show that:(1)the fire resistance of the strengthened beam obtained using the aforementioned simplified method is in good agreement with the test result;(2)the insulation height at beam sides should be less than 90 mm,and the flexural capacity of the strengthened beam increases with an increasing of the insulation height within a range of 0-90 mm;and(3)with a decreasing of the thickness of concrete cover,the flexural capacity of the strengthened beam drops more significantly with heating time,but the flexural capacity deteriorates following similar trerids when the heating time is larger than 2 hours.