1、roduction and prevention and cure of the crack of skyscraper Along with the speeding of town house construction step, not a few areas with small residences set up one after another, many inhabitants move continuously into the new residence, their quality to housing request is more and more high, par
2、ticularly pay attention to very much to some cracks circumstances which sprinkle building plank to appear now, worry these cracks aring end will cause insecurity trouble, but in succession to building quality direct the section hurl tell. Such as once the some city develop a company to set up 6 laye
3、rs of floor residence 16 totally, constructing area about 100,000 square meters, the brick mixs structure, the beginning repairs, one steps 2 box off with the brick wall, each ones establishing a turn of beam together building plank is togetherwhole to sprinkle, the plank thick 100 mms, concrete mar
4、k number is C20, house long about with 80-90 ms, dont establish flexible sew, first floor is the 2.2 m garage layer, the C20 reinforcing bar cage of the foundation adoption infuses to note a stake.Its small areas turn to complete work in October,2003, finishing construction acceptance, didnt discove
5、r obvious crack, discover the building plank appears crack when the inhabitant repair, past jointly to quality direct the section hurl tell, through step to see on the spot, 16 houses all exist the depth different crack.The crack width is between the 0.2 mms mms-0.4ses, the great majority of the cra
6、ck position is placed in plank four Capes, the dynasty sun is more obvious.Hence, the Superintendent office of quality concerned, sinking to decline quantity and inclination degree to carry on a reexamination to the house first, result all in allow the scope, again look into construction diagram pap
7、er to also match to request concerning the norm.Owing to above-mentioned circumstance, pass by hard analytical, the confirmation crack reason has the following what time: 1, cause now main reason of sprinkling the plank crack is the constringency of concrete, the concrete is in the nature the harden
8、ing the process, because water evaporates continuously, but the physical volume gradual constringency, but the plank is on all sides to be subjected to a stipulation of, cant flex freely, so when the constringency of concrete cause to sprinkle knothole stipulation now should the dint exceed certain
9、limit, certanly will cause to sprinkle plank to open crack now.And the crack part take place much at should the dint more concentrated Cape in the place-plank, but is mutually perpendicular with the Overcast angle line of wall 2, construct too early on the cast-in-place board , add and carry on ones
10、 shoulder or back the crack caused. norm of inspection of quality of structural construction of concrete stipulates , before the concrete intensity reaches 1.2N/mm2, cant trample or install template and support on it . But developer , for race against time , catch up with progress , or concrete at ,
11、 congeal and congeal stage after all for the first time still in water at the good cast-in-place board just, take up the post of purpose to trample, carry the material , concentrate on piling up fragment of brick , mortar , template ,etc. Premature adding and is carried on ones shoulder or back, has
12、 caused the crack of cast-in-place board artificially. 3, the crack which the temperature change causes. As everybody knows, the cement condenses and hardens fast at room temperature, the characteristic such as being great of heat of hydration, especially in summer, after the concrete is built, the
13、release amount of the heat of hydration is great, the concrete is under the high temperature, cant get and water maintenance in time , and desiccate and shrink, make concrete take place dry to split , result in fracturing finally. Investigation find in the majority board corner crack in , tan by the
14、 sun towards the front directly the sun. 4, the house is crossed too long to set up the essential expansion joint , is the reason which causes the crack too. The developer is in order to save the land, often take the length of the house into account , make the house whole too long, set up expansion
15、joint either, because of lack essential expansion joint, freedom flexible degree in house reach or exceed should set up interval that expansion joint require , will present the crack too. 5, the board is defeated by the muscle and sunk in the crack produced . In the course of constructing, because c
16、onstructors operate barbarously, trample the reinforcing bar arbitrarily , cause and shoulder the muscle and sink, the antiabrasion layer is too big, reduce the sectional effective height of the board, make the bearing capacity of the board unable to reach the requirement of ones that design, thus c
17、ause the production of the crack of board. Effective height, make the bearing capacity of the board unable to reach the requirement of ones that design, thus cause the production of the crack of board. How to prevent and cure the production of the board crack of cast-in-place board, according to the
18、 construction experience for many years, offer some following prevention measures, suitable for consulting : 1, Do well cast-in-place board maintain , work , guarantee concrete intensity , prevent and cure important link that crack produce one of conscientiously. The norm stipulates , must cover and
19、 keep maintenance warm in 12 hours after the concrete is built at room temperature, ordinary cement is no less than 7 days, if the one that ignored to concrete watered maintenance, on one hand it reduce concrete intensity, on the other hand it make concrete to be in the course of hardening too late
20、to supplement the moisture, therefore lack water and produce the crack in a large amount. So do a good job of watering maintenance of concrete , can already reduce the crack that temperature produces , can also reduce the crack that the concrete shrink and produce . 2, cast-in-place board dont pass
21、morning people , pile material , He Shi load , because concrete have a sclerosis course build , just have intensity； In this course , should maintain the concrete , cant exert any external force to the concrete . In a situation that the concrete has not had certain intensity yet , concentrate on , p
22、ile up construction material or prop up mould stand , rest on it, that brought the cast-in-place board is not intensity like this, but more cracks. So, must make sure that just allow to trample or install template and support on it after the concrete intensity reaches 1.2N/mm2. 3, shoulder thickness
23、 of antiabrasion layer of the muscle the strict control panel . Cast-in-place board shoulder muscle put , on board , have roof beam according to designing requirement through generally put on reinforcing bar of roof beam or stay with reinforcing bar lashing of roof beam cut off ,. For control good t
24、o shoulder muscle antiabrasion layer thickness , must adopt 10 - 14 reinforcing bar horse stool, vertical-horizontal interval 800mm come fixed position to shoulder muscle from side to side, and with electric welding horse with shoulder muscle weld firm stool, make horse to be stool while the concret
25、e builds non-wiping, guarantee , shoulder muscle sink, control , shoulder muscle thickness of antiabrasion layer effectively , make board shoulder muscle antiabrasion layer cross thick producing cracking. 4, control good sand , stone in a foot-path and mud content strictly. The thick sand in the cas
26、t-in-place board should be selected for use, a stone of foot-path between 0.25-0.5mm, the mud content of grit cant exceed 1% . Sand, stone grains of foot-path careful and too light, mud content too big, will reduce concrete intensity, will make the concrete produce the crack finally. 5, dispose cert
27、ain amounts of angle muscles in four corners of the board , radiate the muscle . Take place in board corner phenomenon this more to cast-in-place board crack, corner set up all around in boardThe length radiates the muscle for about 1800mm, so as to meet demands of angle stress of the board, the str
28、ess sphere of action of making the cast-in-place board produce the crack conforms with radiation muscle, thus change and control the production of the crack effectively forced concrete structure reinforced with an overviewRein Since the reform and opening up, with the national economys rapid and sus
29、tained development of a reinforced concrete structure built, reinforced with the development of technology has been great. Therefore, to promote the use of advanced technology reinforced connecting to improve project quality and speed up the pace of construction, improve labor productivity, reduce c
30、osts, and is of great significance. Reinforced steel bars connecting technologies can be divided into two broad categories linking welding machinery and steel. There are six types of welding steel welding methods, and some apply to the prefabricated plant, and some apply to the construction site, so
31、me of both apply. There are three types of machinery commonly used reinforcement linking method primarily applicable to the construction site. Ways has its own characteristics and different application, and in the continuous development and improvement. In actual production, should be based on specific conditions of work, working environment and technical requirements, the choice of suitable methods to achieve the best overall efficiency. 1、 steel mechanical link 1.1 radial squeeze link
