دانلود رایگان مقاله انگلیسی آزمایش به عنوان مبنایی برای بررسی مقاومت آتش زیر ساخت های RC زیرزمینی - الزویر 2019

ABSTRACT

Fire disasters occurring in underground structures generally result in severe damage. In order to investigate the fire performance of typical underground structures, a large-scale fire test on a three-span frame structure was carried out. The tested model was loaded both by vertical and horizontal earth pressures. The applied temperature history, representing the time-dependent fire load, was determined by simulations of fire scenarios in the underground structure with the help of the software FDS. The paper contains test results of the temperature of the air in the furnace, the concrete and the steel bars in the structural model, and the state of deformation of the model. Apparent phenomena, such as cracking and spalling, were observed throughout the whole testing process. The results show that a very dangerous situation of the underground structure exposed to fire may occur during the cooling process. Curling of the top slab was observed during the heating process. More attention in fire-resistance design must be paid to the columns. The fire test results are useful for validation of numerical models and for further fire-resistance research of underground structures.

Conclusions

This paper has dealt with the description of the setup of and the results from a large-scale fire test on a substructure of a typical subway station. The test results are considered to be useful for theoretical and numerical research. The main conclusions are as follows:

(1) Due to the thermal inertia of concrete, the temperature in the concrete is still increasing for a while after termination of the heating process. The highest temperature inside the structure in this test occurs after termination of this process.

(2) The most seriously fire-affected members of underground structures are the columns. They are subjected to the fire at four sides and, thus, the temperature inside the column is increasing fast. Moreover, they bear a high intensity of compressive loading, which may indirectly lead to increased cracking. This suggests that the columns need more attention in fire-resistance design.

(3) During the heating process all slabs experienced a thermal expansion. While the increase of the deformations of the top slab during the heating process was relatively small, the increase of the deformations of the lateral slab during this process was significant.

(4) Since the slab does not have lateral restraints, curling occurred during the heating process.

(5) In the test, the actual fire curve was used instead of a scaled fire curve. The consequence of using the actual fire curve needs to be further studied by means of experimental tests or numerical simulations. This paper gives the results of only one large-scale fire test, more experimental tests will be necessary in the future research.