The Analysis Of Causing The Non-load Cracks Of The Large Concretive Bridge's Components

With the booming development of transport,the widely appearance of long-span Bridge have already brought into attention.Meanwhile,pile cap,Anchorage,main tower,and big span rigid frame bridge's 0# beam of mass concrete was largely adopted by the long-span Bridge.Now,the requirement of concrete grade is gradually higher than before,but unfortunately,the problem of the mass concrete structural temperature and cracks have become increasingly sharp,because construction organization often adopt super-early-strength concrete for speeding up the construction period,which contribute to substantial increase the cement's hydration heat value and the cement's hydrous heat liberation rate adopted by mass concrete element.The main reason of concrete cracks is,in the hardening process hydration heat released by mass concrete,will produce biggish variations of temperature and constrains.During construction mass concrete element give birth to non-load cracks that will influence the integrity of the structure,waterproofing and durability,even turn into constructional hidden danger,so cracks control of mass concrete element should be seriously considered.Based on the reason of the appearance of mass concrete structural temperature and cracks,this paper studied the phenomenon of non-load cracks appeared on 3#,4# pier,and 0# beam section of Lo Tin Lok Bridge over the Red River located at the junction of GuiZhou province and GuangXi autonomous regions,as well as simulation analyzed the structure of 4# pier and 0# beam section.In addition,this essay makes the further exploration on the change rule of structural inner temperature field,temperature and stress of 0# beam section,and find out the unreasonable construction scenario that is integrate the restraint stress(from the effect of the first lift on the second new lift in the hydration contraction process) and the temperature stress(produced by hydration heat ultra-early-strength concrete in the early stage), which lead to produce non-load cracks. Numerical simulation analysis to the construction process of #0 beam segment has been carried out with MIDAS software.The temperature field,the transformation process of thermal stress,the temperatures and the extreme thermal stress of #0 beam segment which had been analyzed with finite element simulation method,matched well with the realistic situation.The deviation between the results of realistic monitoring as well as analysis and the results of simulation analysis is very small.To simulate and analyze the large volume components of bridges with finite element software before construction according to the realistic construction situation is of some usage to instruct the real construction.This paper based on the research that is 4# pier,and 0# beam section of Lo Tin Lok Bridge appear non-load cracks,and find out the specific reason of why the Bridge has non-load cracks,which provides an beneficial reference and resource for similar projects in the future.