| With the high-quality development of China’s modernization,various large and super-large public construction projects are increasing year by year.The basement part of such buildings has a span of a hundred meters or even several hundred meters,and has complex structure and working conditions.In order to meet the use function of the building,such projects usually adopt seamless design,so it will generate high temperature stresses,which will cause cracks in the structure and cause serious damage to the project.In this context,construction measures regarding the temperature rise and change during the construction of extra-long and complex basements and the effective reduction of temperature stresses need to be studied urgently.This thesis takes Shanghai Nine Stars City super-long complex basement project as the research object,and starts the research on the bottom slab engineering and top slab engineering of the project.In the bottom slab project,the temperature of the bottom slab was analyzed about48 h after pouring by jumping method through the method of engineering measurement,and the control effect of jumping method on the temperature rise of the bottom slab and the relationship between the boundary constraint of the slab and the temperature distribution were studied to provide valuable reference for the construction of the same type of project.For the top slab project,Midas/GEN finite element analysis software was used to study the construction measures such as selective machine construction,selection of overlay insulation materials and number of days to close the post-cast zone,analyze the influence of the above construction measures on the temperature stress,and obtain the optimal combination of construction measures and the control effect of this combination on the temperature stress of the top slab through binary logistic verification,and make predictions on the possible temperature stress The study is also carried out to predict the possible excessive temperature stress areas,and to propose prevention and control plans in combination with the actual engineering practice,so that this study has the value of guiding engineering practice.The main research conclusions are as follows:(1)After the concrete of the bottom slab was poured by the skip bin method,the temperature of 12 bins in plot 07-01 was tested,and the suppression effect of the skip bin method on the temperature rise of the extra-long and complex basement bottom slab was analyzed,and the distribution of the surface temperature,the middle temperature and the bottom temperature were studied to derive the effect of different boundary constraints on the temperature distribution of the bins.The results show that the number of boundary constraints has a small effect on surface temperature and bottom surface temperature,and a large effect on middle temperature,the more boundary constraints,the higher the temperature;the use of jumping bin method of pouring can make the temperature of the core of 12 bin blocks in plot 07-01 controlled within39℃,the temperature difference between surface and inside controlled within 14℃,and the temperature difference between inside and outside controlled within 19℃,which can effectively avoid a large temperature difference in the bottom slab of extra-long complex basement temperature difference,thus reducing the temperature stress.(2)Using Midas/GEN finite element analysis software,we established a model of superlong and complex basement roof slab in Shanghai Nine Stars City,and analyzed the effects of opportunistic construction,selection of cladding insulation materials and the number of days of closure of post-cast zone on the temperature stress of super-long and complex basement roof slab,and obtained the best construction month,the ranking of insulation performance of materials and the law between temperature stress and the number of days of closure of post-cast zone.The results show that the single construction measures such as selective construction,laminated insulation and post-cast zone setting can reduce the temperature stress of basement roof slab by 27%,45% and 41%,respectively;the ambient temperature difference is the smallest in May and the largest in April,and the temperature stress of the roof slab becomes larger as the ambient temperature difference becomes larger;the effect of each insulation material to reduce the temperature stress of the roof slab is,straw bag > wood board > sand layer;the temperature stress of the roof slab The temperature stress of the top slab decreases with the increase of the closing time of the backcasting zone,and the rate of temperature stress decrease decreases with the increase of the closing time of the backcasting zone.(3)On the basis of Midas/GEN finite element analysis,a binary logistic model was constructed to further demonstrate the relationship between the above construction measures and temperature stresses,and finally the best combination of three types of construction measures and the distribution law of temperature stresses in the top slab of extra-long complex basements affected by the combination of construction measures were obtained.The results show that the best combination of construction measures is to use straw bag as the cladding insulation material,to carry out construction in May and to close the post-pouring zone after100 days of pouring;a temperature stress greater than 2.2 MPa may occur in the intersection area between axis B-58～B-59 and axis B-D～B-E and between axis B-58～B-59 and axis B-M～BN of the project,and specific countermeasures are proposed in combination with the actual situation of the project.The optimal combination of construction measures can reduce the temperature stress by 76% compared with the original bottom slab model,and the temperature stress at 65% of the measured points is concentrated in the interval of 0.6MPa-1.4MPa,with the maximum value of 1.7MPa and the minimum value of 0.4MPa,which are lower than the standard value of C35 concrete tensile strength of 2.2MPa.. |
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