Influence Of Temperature Change On Steel Composite Support Structure System Of Deep Foundation Pit

With the progress of China’s urbanization and rapid economic development,there are many deep and large foundation pits in the construction.Due to the environmental effects and temporary characteristics of the foundation pit engineering,the seasonal alternating temperature and the large temperature difference between day and night in some areas,especially steel,the phenomenon of thermal expansion and contraction is very obvious.Therefore,it is very necessary to study the influence of ambient temperature and profile temperature on the support structure.Based on the analysis of the measured data of a deep foundation pit in the soft soil area of Hangzhou in the west of Hangzhou for 6 months,this paper mainly studies the effects of environmental temperature changes and surface temperature changes of the support in the foundation pit on the supporting structure of the foundation pit.The measured data analysis shows that the axial force variation of the steel support increases with the increase of the surface temperature and atmospheric temperature of the steel,and decreases with the decrease of the temperature.For the upper and lower steel supports,the second support is affected by the temperature change.The axial force is larger than the first layer,and the maximum influence is about twice the value.For the removal of the second layer support,only the first layer of support,the axial force variation value of the innermost single steel of each support is almost fitted with the temperature difference of the profile steel.The quadratic function curve.At the same time,the axial force generated by the single section steel in the combined steel support(corner)has the characteristics of large inside and small outside;with the increase of the support length,the axial force of the combined steel gusset is linear with the change of temperature difference.The change and the magnitude of the change are larger;the axial force(k N/m~3)normalized by the length and the cross-sectional area and the temperature of the profile steel(°C)can be obtained by considering the different support factors for different temperatures and the different support lengths and cross-sectional areas.Approximate linear relationship,the fitting curve is:y=0.27x+1.03;the average surface temperature of the profile steel increases from 1°C(close to 0°C)to 31°C,and the support length is86.85 m,the axial force changes.Is 2523 k N;Effects of soil properties significant effect on the temperature of the support.Relying on a deep foundation pit in Hangzhou as the background project,the ABAQUS finite element software was used to carry out the three-dimensional numerical simulation analysis,and the following conclusions were drawn:the calculated axial force of the steel support can be well matched with the measured value,and the numerical simulation is verified.Rationality;when the two layers of support have the same effect,the displacement of the retaining structure is increased compared to the one layer of support,and the casting of the bottom plate increases the axial force of the second layer;when the first layer and the second layer are When the support is simultaneously heated,the displacement of the longest support A6 end is the largest.