【正文】 middle part, case is it might fracture to contain 4, The difference of basic type of structure is great. Unite it in the bridge the samly , mix and use and does not expand the foundation and a foundation with the foundation, or adopt a foundation when a footpath or a long difference is great at the same time , or adopt the foundation of expanding when basis elevation is widely different at the same time , may cause the ground not to subside evenly too 5, Foundation built by stages. In the newlybuilt bridge near the foundation of original bridge, if the half a bridge about expressway built by stages, the newlybuilt bridge loads or the foundation causes the soil of the ground to consolidate again while dealing with, may cause and subside the foundation of original bridge greatly 6, The ground is frozen bloatedly. The ground soil of higher moisture content on terms that lower than zero degree expands because of being icy。 Strong wind , heavy snow , earthquake happen , explode etc.. Stress crack once means the stress of secondary 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 structure 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 , 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 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 ponent , it will produce the diffraction phenomenon that strength flows, intensive near the hole in a utensil, 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 if deal with improper, in corner or ponent 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 mon reason which loads the crack. Stress crack once belong to one more piece of nature 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 acplish reasonable checking putations too. For example to such stresses 2 times of producing as prestressing force , creeping ,etc., department39。 It is simply little and assigning the mistake for reinforcing bar to set up。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 quality lead of mon occurrence report that bridge collapse even because the crack appears The concrete can be said to often have illness ing on while fracturing and frequentlyoccurring disease , often perplex bridge engineers and technicians. In fact , if take certain design and construction measure, a lot of cracks can be overe and controlled. For strengthen understanding of concrete bridge crack further, is it prevent project from endanger larger crack to try one39。 It is insufficient to design the section。 Receive the contact , striking of the vehicle , shipping。 It is too long, cause and divide storey, thick aggregate sinks to the ground floor, the upper strata that the detailed aggregate stays, the intensity is not even , the upper strata incident shrink the crack. And shrink the crack caused to temperature, worthy of constructing the reinforcing bar againing can obviously improve the resisting the splitting of concrete , structure of especially thin wall (thick 200cm of wall ). Mix muscle should is it adopt light diameter reinforcing bar (8 |? construct 14 |? ) to have priority , little interval assign (whether 10 construct 15cm ) on constructing, the whole section is it mix muscle to be rate unsuitable to be lower than 0 to construct. 3%, can generally adopt 0 . 3%~0. 5%. (4), crack that causes out of shape of plinth of the ground Because foundation vertical to even to subside or horizontal direction displacement, make the structure produce the additional stress, go beyond resisting the ability of drawing of concrete structure, cause the structure to fracture. The even main reason that subside of the foundation is as follows, 1, Reconnoitres the precision and is not enough for , test the materials inaccuratly in geology. Designing, constructing without fully grasping the geological situation, this is the main reason that cause the ground not to subside evenly . Such as hills area or bridge, district of mountain ridge, hole interval to be too far when reconnoitring, and ground rise and fall big the rock, reconnoitring the report can39。 混凝土橋梁裂縫種 類 和形成原 因復雜而繁多，甚至多種因素相互影響，但每一條裂縫均有其產(chǎn)生的一種或幾種主要原因。裂縫產(chǎn)生的原因有： （一） 在設計外荷載作用下，由于結構物的實際工作狀態(tài)同 常規(guī)計算有出入或計算不考慮，從而在某些部位引起次應力導致結構開裂。次應力裂縫也是 由荷載引起，僅是按常規(guī)一般不計算，但隨著現(xiàn)代計算手段的不斷完善，次應力裂縫也是可以