| In recent years,with the rapid development of economy in our country and expanding city construction,the emergence of many large long public buildings and industrial and civil buildings.This type of construction in order to meet the needs of appearance and function of the building,usually have no or a few joints,then need to set the post pouring belt to solve concrete shrinkage crack problem.Research but after pouring engineering experience with law is far ahead of theory,design personnel basicly refer to the practical experience in the design,and do not calculate after careful analysis.It makes the structure not only cannot achieve the purpose of controlling cracks,but caused a large number of cracks appear late,which makes many problems for the use of the later building.Based on the summary of previous research achievements on study of large,super long cast-in-situ concrete frame post cast strip closed relationship between the time and the spacing of the.The main works are as follows:Firstly,introduced the post pouring belt action principle in the ultra long concrete structure,and the super long concrete structure after pouring With the research status in the domestic and international were summarized and analysis.Secondly,mainly introduced the cast-in-place reinforced concrete structure temperature and shrinkage and creep effects,and these effects are analyzed one by one.Using MIDAS/Gen software simulates the overlong frame structure under the action of force of uniform temperature,for the following analysis to pave the way for the latter pouring belt.Then using MIDAS/Gen software simulation analysis of 71.4 meters of concrete frame structure sets 0,1,2 and 3 post pouring belt longitudinal beam stress and the across the board change shrinkage stress,then study the post pouring band spacing effects on the structure of shrinkage stress.And then analysis the 71.4 meters of concrete frame structure in the post pouring strip indwelling for 15 days,30 days of simulation,changes of 60 days in the case of the cross board shrinkage stress,then study the post pouring strip indwelling time effect on the structure of shrinkage stress.Finally it determines the post pouring belt closed the theory relationship spacing time and installation,and be used for engineering example.The work of this paper is summarized,and the further research work is prospected.Studies have shown that,Temperature effect of multi-layer super-long concrete frame structure is mainly in the bottom of the first and the second layer.By a layer of each layer gradually,and temperature effect weakened quickly,so that can be neglected;Whether single increase the number of the article of post-cast strip or single increase the indwelling time of post-cast strip,longitudinal beam,plate efficiency of shrinkage stress reduce efficiency reduce rapidly,this shows that only by setting the post-pouring belt,to solve the temperature shrinkage stress of frame structures is limited,this is we need to take some other methods;After pouring belt can not only achieve directly reduce the pouring belt is located across the board,the purpose of shrinkage stress and still can reach to a relatively large shrinkage stress transfer adjacent smaller across goal;When the spacing of post-cast strip determine,after pouring belt is located across the adjacent spans in the longitudinal beam,slab shrinkage stress with the increase of the indwelling time,its value is more and more big.This is the place that need our attention;According to specific project closed frame post-cast strip plate before contraction stress and closed after the board of post-cast strip temperature contraction stress is not greater than the sum of 55 meters frame structure in thte same layout and same temperature under the action of temperature shrinkage stress,to determine the certain conditions in closed time spacing of post-cast strip concrete frame structure of the project,to provide theoretical basis for setting post-cast strip for later. |
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