1、roduction and prevention and cure of the crack of skyscraperAlong 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, part

2、icularly 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 l

3、ayers 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 one's establishing a turn of beam together building plank is togetherwhole to sprinkle, the plank thick 100 mms, conc

4、rete mark number is C20, house long about with 80-90 ms, don't 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.It's small area's turn to complete work in October,2003, finishing construction ac

5、ceptance, didn't discover 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, t

6、he great majority of the crack 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 i

7、nto construction diagram paper 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

8、 is in the nature the hardening 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, can't flex freely, so when the constringency of concrete cause to sprinkle knothole stipulation no

9、w should the dint exceed certain 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-pl

10、ace board , add and carry on one's 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, can't trample or install template and support on it . But developer , for race

11、 against time , catch up with progress , or concrete at , 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. Prem

12、ature adding and is carried on one's shoulder or back, has 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 hydra

13、tion, especially in summer, after the concrete is built, the release amount of the heat of hydration is great, the concrete is under the high temperature, can't get and water maintenance in time , and desiccate and shrink, make concrete take place dry to split , result in fracturing finally. Inv

14、estigation find in the majority board corner crack in , tan by the 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 hou

15、se into account , make the house whole too long, set up expansion 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 sun

16、k in the crack produced . In the course of constructing, because constructors 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

17、 board unable to reach the requirement of ones that design, thus cause 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 prod

18、uction of the board crack of cast-in-place board, according to the 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 pr

19、oduce one of conscientiously. The norm stipulates , must cover and 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 othe

20、r hand it make concrete to be in the course of hardening too late 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 t

21、he concrete shrink and produce . 2, cast-in-place board don't pass morning people , pile material , He Shi load , because concrete have a sclerosis course build , just have intensity; In this course , should maintain the concrete , can't exert any external force to the concrete . In a situat

22、ion that the concrete has not had certain intensity yet , concentrate on , pile 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 suppor

23、t on it after the concrete intensity reaches 1.2N/mm2. 3, shoulder thickness 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

24、stay with reinforcing bar lashing of roof beam cut off ,. For control good to 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 wi

25、th shoulder muscle weld firm stool, make horse to be stool while the concrete 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 san

26、d , stone in a foot-path and mud content strictly. The thick sand in the cast-in-place board should be selected for use, a stone of foot-path between 0.25-0.5mm, the mud content of grit can't exceed 1% . Sand, stone grains of foot-path careful and too light, mud content too big, will reduce conc

27、rete intensity, will make the concrete produce the crack finally.5, dispose certain 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 musc

28、le for about 1800mm, so as to meet demands of angle stress of the board, the stress 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 effectivelyforced concrete structure reinforced with an overvie

29、wReinSince the reform and opening up, with the national economy's rapid and sustained 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

30、quality and speed up the pace of construction, improve labor productivity, reduce costs, 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

31、 some apply to the prefabricated plant, and some apply to the construction site, some 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 con

32、tinuous 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 linkWill be a steel sleeve in t

33、wo sets to the highly-reinforced Department with superhigh pressure hydraulic equipment (squeeze tongs) along steel sleeve radial squeeze steel casing, in squeezing out tongs squeeze pressure role of a steel sleeve plasticity deformation closely integrated with reinforced through reinforced steel sl

34、eeve and Wang Liang's Position will be two solid steel bars linkedCharacteristic: Connect intensity to be high, performance reliable, can bear high stress draw and pigeonhole the load and tired load repeatedly.Easy and simple to handle, construction fast, save energy and material, comprehensive

35、economy profitable, this method has been already a large amount of application in the project.Applicable scope : Suitable for , , grade reinforcing bar (including welding bad reinforcing bar ) with ribbing of 18- 50mm, connection between the same diameter or different diameters reinforcing bar .1.2

36、must squeeze linkExtruders used in the covers, reinforced axis along the cold metal sleeve squeeze dedicated to insert sleeve Lane two hot rolling steel drums into a highly integrated mechanical linking methods.Characteristic: Easy to operate and joining fast and not having flame homework , can cons

37、truct for 24 hours , save a large number of reinforcing bars and energy.Applicable scope : Suitable for , set up according to first and second class antidetonation requirement -proof armored concrete structure , grade reinforcing bar with ribbing of hot rolling of 20- 32mm join and construct live.1.

38、3 cone thread connectingUsing cone thread to bear pulled, pressed both effort and self-locking nature, undergo good principles will be reinforced by linking into cone-processing thread at the moment the value of integration into the joints connecting steel bars.Characteristic: Simple , all right pre

39、paratory cut of the craft , connecting fast, concentricity is good, have pattern person who restrain from advantage reinforcing bar carbon content.Applicable scope : Suitable for the concrete structure of the industry , civil building and general structures, reinforcing bar diameter is for for the t

40、he 16- 40mm one , grade verticality, it is the oblique to or reinforcing bars horizontal join construct live. conclusionsThese are now commonly used to connect steel synthesis methods, which links technology in the United States, Britain, Japan and other countries are widely used. There are differen

41、t ways to connect their different characteristics and scope of the actual construction of production depending on the specific project choose a suitable method of connecting to achieve both energy conservation and saving time limit for a project ends.References1 、construction manual write the group.

42、 Construction manual. Beijing: China Construction Industry Press, 1992.2 、JGJ107-96 reinforcing bar machinery connects the common technical regulation 3 GB 1499-91 The armored concrete uses the reinforcing bar. 4 、GB with ribbing of hot rolling 13013-91 The armored concrete uses the round reinforcin

43、g bar of hot calendaring.現(xiàn)澆樓板裂縫的產(chǎn)生與防治隨著城市住宅建設(shè)步伐的加快，不少住宅小區(qū)相繼建成，許多住戶陸續(xù)搬進(jìn)新居，他們對(duì)住房的質(zhì)量要求越來越高，尤其對(duì)一些現(xiàn)澆樓板出現(xiàn)的裂縫情況非常關(guān)注，擔(dān)心這些裂縫最終會(huì)引發(fā)不安全事故，而紛紛向建筑質(zhì)量監(jiān)督部門投訴。 如某市一開發(fā)商共建6層樓住宅16幢，建筑面積約10萬平方米，磚混結(jié)構(gòu)，初裝修，一梯二戶用磚墻分隔，每層設(shè)有圈梁同樓板整澆，板厚100mm，混凝土標(biāo)號(hào)為C20，房屋長約80-90m之間，不設(shè)伸縮縫，底層為2.2m車庫層，基礎(chǔ)采用C20鋼筋籠灌注樁。該小區(qū)于2003年10月完工，竣工驗(yàn)收時(shí)，未發(fā)現(xiàn)明顯裂縫，在住戶裝修時(shí)

44、，發(fā)現(xiàn)樓板有裂縫出現(xiàn)，故聯(lián)名向質(zhì)量監(jiān)督部門投訴，經(jīng)實(shí)地踏看，16幢房屋均存在深淺不一的裂縫。裂縫寬度在0.2mm-0.4mm之間，裂縫位置絕大多數(shù)處在板四角，朝陽處更為明顯。于是，質(zhì)監(jiān)部門組織有關(guān)單位，首先對(duì)房屋沉降量和傾斜度進(jìn)行復(fù)查，結(jié)果都在允許范圍內(nèi)，再查看施工圖紙也符合有關(guān)規(guī)范要求。鑒于上述情況，經(jīng)過認(rèn)真分析，確認(rèn)裂縫原因有以下幾點(diǎn)： 1、引起現(xiàn)澆板裂縫的主要原因是混凝土的收縮，因?yàn)榛炷猎谧匀挥不^程中，由于水份不斷蒸發(fā)，而體積漸漸收縮，但板四周受支座的約束，不能自由伸縮，所以當(dāng)混凝土的收縮所引起現(xiàn)澆板的約束應(yīng)力超過一定限度時(shí)，勢(shì)必引發(fā)現(xiàn)澆板開裂。而且裂縫部位多發(fā)生在應(yīng)力比較集中的地方

45、板角處，卻與墻陰角線相垂直。 2、現(xiàn)澆板上過早施工，加荷引起的裂縫?；炷两Y(jié)構(gòu)工程施工質(zhì)量驗(yàn)收規(guī)范規(guī)定，混凝土強(qiáng)度達(dá)到1.2N/mm2前，不得在其上踩踏或安裝模板及支架。但開發(fā)商為了搶時(shí)間，趕進(jìn)度，在剛澆好的現(xiàn)澆板上或混凝土尚處在初凝和終凝階段，就任意踩踏，搬運(yùn)材料，集中堆放磚塊、砂漿、模板等。過早的加荷，人為地造成了現(xiàn)澆板裂縫。 3、溫度變化引起的裂縫。大家知道，水泥在常溫下具有凝結(jié)硬化快，水化熱大等特點(diǎn)，尤其在夏天，混凝土澆筑后，水化熱釋放量大，混凝土在高溫下，得不到及時(shí)澆水養(yǎng)護(hù)，而失水收縮，使混凝土發(fā)生干裂，最終導(dǎo)致開裂。調(diào)查中發(fā)現(xiàn)，居多板角裂縫都處在遭受太陽直接曝曬的朝陽面。 4、房屋

46、過長未設(shè)置必要的伸縮縫，也是導(dǎo)致裂縫的原因。開發(fā)商為了節(jié)省土地，往往不顧及房屋長度，使房屋整體過長，也不設(shè)置伸縮縫，由于缺少必要的伸縮縫，當(dāng)房屋的自由伸縮度達(dá)到或超過應(yīng)設(shè)置伸縮縫要求的間距時(shí)，也會(huì)出現(xiàn)裂縫。 5、板負(fù)筋下沉產(chǎn)生的裂縫。在施工過程中，由于施工人員野蠻操作，任意踩踏鋼筋，致使負(fù)筋下陷，保護(hù)層過大，減少了板截面的有效高度，使板的承載能力達(dá)不到設(shè)計(jì)的要求，從而導(dǎo)致板裂縫的產(chǎn)生。 如何防治現(xiàn)澆板板裂縫的產(chǎn)生，根據(jù)多年的施工經(jīng)驗(yàn)，提供以下一些防治措施，可供參考： 1、認(rèn)真做好現(xiàn)澆板養(yǎng)護(hù)工作，是保證混凝土強(qiáng)度、防治裂縫產(chǎn)生的重要環(huán)節(jié)之一。規(guī)范規(guī)定，常溫下混凝土澆筑后12小時(shí)內(nèi)，必須覆蓋保溫養(yǎng)護(hù)，普通水泥不少于7天，如果忽視對(duì)混凝土的澆水養(yǎng)護(hù)，一方面會(huì)降低混凝土強(qiáng)度，另一方面會(huì)使混凝土在硬化過程中來不及補(bǔ)充水分，因而大量缺水而產(chǎn)生裂縫。所以做好混凝土的澆水養(yǎng)護(hù)，既可減少溫度產(chǎn)生的裂縫，也可降低混凝土收縮而產(chǎn)生的裂縫。 2、現(xiàn)澆板上不要過早上人、堆料、施荷加載，因混凝土澆筑后要有一個(gè)硬化過程，才