Experimental Study On Performance Of Interfacing Between HPFL And RC Beams Under High Temperature-Forces

Fire is playing an important part in the human's life and creating,but once the fire is out of control,it will cause great damage to the human.Every kind of fire has caused a mass of death and great loss of natural resources and material fortunes.Our country also has many fire accidents in the buildings,and the fire resistance of structures is also an important problem in the filed of structural engineering.For the filed of structure strengthening,the fire resistance has becoming a headachy problem. In the exist strengthening methods,many need to use organic materials such as structural glue,but when the temperature exceed 70℃,the strengthening structure will lose its effect as soon as the glue doesn't work.The strengthening method with the HPFL(High-performance ferrocement laminate) has obvious advantages in the fire resistance ,because the materials it used mainly consist of inorganic materials, the material character of which is very similar to the concret,and has good consistent,harmonious and penetrative character with the mother-materials.Based on these points,it will has better fire resistance performance than other strengthening methods which use organic structural glue when using HPFL strengthening method.Fire resistance of the RC beams without web strengthened by the HPFL is analyzed in this dissertation,and also some experiment researches are carried on.The main contents are summarized as follows.(1) The popular thermal and mechanical behaviors of concret and reinforced steel bar at elevated temperature over the world are summarized and compared,at the same time,experiments are carried on the composite mortar used in the strengthening method in order to get its regularity of the compressive strength after elevated temperature.(2) In the component which is reinforced by HPFL, the bond strenth of interface is crucial to guarantee the effect of reinforcement, and the two main factors which influence the bond strenth of interface are the degree of roughness between new and old concretes and the distribution of shear pins in the interface. Through comparing with the result of high temperature test, the author analyzes the mechanism that the degree of roughness and the spacing interval of shear pins will influence bond strenth of interface in theory; In order to combine theory with practical project, various fire resistance rating demand different construction of the degree of roughness and the spacing interval of shear pins are proposed. (3) According to the results of high temperature test, the author made data analysis and deduces the relationship between the duration of fire resistance and initial load, at the same time , two important parameters are introduced: degree of roughness influence coefficientΨand spacing interval of shear pins influence coefficientζ(4) The article expatiates on the measures to strength RC beams by HPFL and also put forward some suggestions and experiences.