1、The bridge crack produced the reason to simply analyse In recent years, the traffic capital construction of our province gets swift and violent development, all parts have built a large number of concrete bridges. In the course of building and using in the bridge, relevant to influence project quali
2、ty lead of common occurrence report that bridge collapse even because the crack appears The concrete can be said to often have illness coming on while fracturing and frequently-occurring disease , often perplex bridge engineers and technicians. In fact , if take certain design and construction measu
3、re, a lot of cracks can be overcome and controlled. For strengthen understanding of concrete bridge crack further, is it prevent project from endanger larger crack to try ones best, this text make an more overall analysis , summary to concrete kind and reason of production , bridge of crack as much
4、as possible, in order to design , construct and find out the feasible method which control the crack , get the result of taking precautions against Yu WeiRan. Concrete bridge crack kind, origin cause of formation In fact, the origin cause of formation of the concrete structure crack is complicated a
5、nd various, even many kinds of factors influence each other , but every crack has its one or several kinds of main reasons produced . The kind of the concrete bridge crack, on its reason to produce, can roughly divide several kinds as follows : (1) load the crack caused Concrete in routine quiet . I
6、s it load to move and crack that produce claim to load the crack under the times of stress bridge, summing up has direct stress cracks , two kinds stress crack onces mainly. Direct stress crack refer to outside load direct crack that stress produce that cause. The reason why the crack produces is as
7、 follows, 1, Design the stage of calculating , does not calculate or leaks and calculates partly while calculating in structure； Calculate the model is unreasonable； The structure is supposed and accorded with by strength actually by strength ； Load and calculate or leak and calculate few； Internal
8、force and matching the mistake in computation of muscle； Safety coefficient of structure is not enough. Do not consider the possibility that construct at the time of the structural design； It is insufficient to design the section； It is simply little and assigning the mistake for reinforcing bar to
9、set up； Structure rigidity is insufficient； Construct and deal with improperly； The design drawing can not be explained clearly etc. 2, Construction stage, does not pile up and construct the machines , material limiting ； Is it prefabricate structure structure receive strength characteristic , stand
10、 up , is it hang , transport , install to get up at will to understand； Construct not according to the design drawing, alter the construction order of the structure without authorization , change the structure and receive the strength mode； Do not do the tired intensity checking computations under m
11、achine vibration and wait to the structure . 3, Using stage, the heavy-duty vehicle which goes beyond the design load passes the bridge； Receive the contact , striking of the vehicle , shipping； Strong wind , heavy snow , earthquake happen , explode etc. Stress crack once means the stress of seconda
12、ry caused by loading outside produces the crack. The reason why the crack produces is as follows, 1, In design outside load function , because actual working state and routine , structure of thing calculate have discrepancy or is it consider to calculate, thus cause stress once to cause the structur
13、e to fracture in some position. Two is it join bridge arch foot is it is it assign X shape reinforcing bar , cut down this place way , section of size design and cut with scissors at the same time to adopt often to design to cut with scissors, theory calculate place this can store curved square in ,
14、 but reality should is it can resist curved still to cut with scissors, so that present the crack and cause the reinforcing bar corrosion. 2, Bridge structure is it dig trough , turn on hole , set up ox leg ,etc. to need often, difficult to use a accurate one diagrammatic to is it is it calculate to
15、 imitate to go on in calculating in routine, set up and receive the strength reinforcing bar in general foundation experience. Studies have shown , after being dug the hole by the strength component , it will produce the diffraction phenomenon that strength flows, intensive near the hole in a utensi
16、l, produced the enormous stress to concentrate. In long to step prestressing force of the continuous roof beam , often block the steel bunch according to the needs of section internal force in stepping, set up the anchor head, but can often see the crack in the anchor firm section adjacent place. So
17、 if deal with improper, in corner or component form sudden change office , block place to be easy to appear crack strength reinforcing bar of structure the. In the actual project, stress crack once produced the most common reason which loads the crack. Stress crack once belong to one more piece of n
18、ature of drawing , splitting off , shearing. Stress crack once is loaded and caused, only seldom calculate according to the routine too, but with modern to calculate constant perfection of means, times of stress crack to can accomplish reasonable checking computations too. For example to such stress
19、es 2 times of producing as prestressing force , creeping ,etc., departments finite element procedure calculates levels pole correctly now, but more difficult 40 years ago. In the design, should pay attention to avoiding structure sudden change (or section sudden change), when it is unable to avoid ,
20、 should do part deal with , corner for instance, make round horn , sudden change office make into the gradation zone transition, is it is it mix muscle to construct to strengthen at the same time, corner mix again oblique to reinforcing bar , as to large hole in a utensil can set up protecting in th
21、e perimeter at the terms of having angle steel. Load the crack characteristic in accordance with loading differently and presenting different characteristics differently. The crack appear person who draw more, the cutting area or the serious position of vibration. Must point out , is it get up cover
22、 or have along keep into short crack of direction to appear person who press, often the structure reaches the sign of bearing the weight of strength limit, it is an omen that the structure is destroyed, its reason is often that sectional size is partial and small. Receive the strength way differentl
23、y according to the structure, the crack characteristic produced is as follows: 1, The centre is drawn. The crack runs through the component cross section , the interval is equal on the whole , and is perpendicular to receiving the strength direction. While adopting the whorl reinforcing bar , lie in
24、 the second-class crack near the reinforcing bar between the cracks. 2, The centre is pressed. It is parallel on the short and dense parallel crack which receive the strength direction to appear along the component. 3, Receive curved. Most near the large section from border is it appear and draw int
25、o direction vertical crack to begin person who draw curved square, and develop toward neutralization axle gradually. While adopting the whorl reinforcing bar , can see shorter second-class crack among the cracks. When the structure matches muscles less, there are few but wide cracks, fragility destruction may take place in the structure 4, Pressed big and partial. Heavy to press and mix person who draw muscle a less
