Uniaxial Tensile Principal Structure Relationship Of EPS Concrete And Performance Study Of Light Steel Composite Axial Tensile Members

Concrete,as the most widely used building material since the twentieth century,has a pivotal role in current construction projects,while with the progress of modernization,concrete building fires have become an important direction in the development of building science.Concrete materials have good thermal inertia,but concrete materials,especially new concrete materials under the action of high temperature performance changes have been the focus of research at home and abroad,scholars from various countries on the high-temperature performance of ordinary concrete materials have been more mature research results,but for high-strength highperformance concrete materials after the fire performance changes,the results of the study is not perfect,for the fiber on high-strength concrete in The influence of high temperature effect is less considered.In order to accurately understand the performance changes of mixed-fiber high-strength concrete after the action of high temperature,the following research results were obtained after ambient and high-temperature tests on steel-polypropylene fiber high-strength concrete:(1)On the basis of the high temperature test,the apparent changes of concrete specimens and the law of mass loss rate were analyzed.With the increase of temperature,the apparent changes of concrete were,dark gray → light gray with red → yellowish white → light yellow;the cracks on the surface of concrete specimens gradually increased,almost no visible cracks at 200℃ temperature,sparse tiny cracks began to appear at 400℃ temperature,and at 600℃ temperature The cracks gradually increased and connected,and the cracks gradually became wider after the temperature reached800℃,and the surface of the specimens were covered with cracks after the temperature reached 1000℃,but the fiber concrete specimens did not burst;the mass loss rate of concrete gradually increased with the increase of temperature,and reached 15% at1000℃.(2)The strength changes of high-strength concrete with different fiber admixtures and the strength changes of high-strength concrete specimens with different fiber admixtures and temperature gradients were observed and analyzed and fitted,and it was found that the effect of steel fiber on the strength of high-strength concrete at room temperature was more significant,and the optimal ratio and strength formula of steelpolypropylene fiber high-strength concrete at room temperature were obtained;it was found that the strength of concrete after the high temperature effect showed a little The strength of high-strength concrete was found to decrease slightly and then increase slightly after high temperature,and the strength decreased rapidly after 400℃ and decreased to less than one-fourth after more than 600℃,and the relationship between strength and temperature of high-strength concrete was summarized.(3)The risk assessment methods and testing methods for building fires are summarized,and the identification methods that are more suitable for concrete structures after fires are recommended;the post-fire damage levels and assessment criteria for different concrete materials are summarized through experimental analysis.