(A) the development history and present situation of China arch bridge.
In the series of highway bridges in China, the arch bridge, as an ancient bridge type, has the longest architectural history and strong competitiveness with its unique technical advantages such as large spanning capacity, high bearing capacity, local materials, economical cost, low maintenance cost and beautiful appearance. It is an ever-developing bridge form. According to statistics, there are as many as 1 15 arch bridges with single span 100m in China. Arch bridge is still one of the main types of long-span highway bridges in China. The development of highway arch bridges in China can be roughly divided into four stages. The first stage was from the 1950s to the mid-1960s. Most of them are small and medium-sized stone arch bridges. At that time, there was also research on flaky concrete arch bridge, but it was not popularized. The arch bridge with the largest span is Changhong Bridge (single span 1 12.5m hollow rubber stone arch bridge) built on Nanpanjiang River in Yunnan in 196 1 year. The second stage is from the mid-1960s to the 1970s, and the dominant bridge type is the hyperbolic arch bridge with low reinforcement. Due to the small amount of steel used in the double-curved arch bridge, it can be disassembled into parts during construction, requires less lifting equipment, and is easy to engage in mass movements at that time, so it developed rapidly. At that time, arch bridges with less reinforcement, such as precast concrete block arch and two hinged arch, were also studied. The longest span is the He Qian Bridge in Songxian County, Henan Province, which was completed in 1968 (span 150m, hyperbolic arch bridge). The third stage is from the end of 1970s to 1980s, and the dominant bridge type is large and medium-span precast reinforced concrete box (ribbed) arch bridge. The largest span built by lifting without support is Mamingxi Bridge in Yibin, Sichuan (1979 completed, span 150m), and the largest span built by support method is Baoding Bridge in Panzhihua, Sichuan (1982 completed, span 170m). During this period, the maximum span of reinforced concrete arch bridges abroad has reached 390m (KrKI, I Bridge in Kerk, Yugoslavia, 1980 completed). The fourth stage is marked by the Jinsha River Bridge at Nanmen, Yibin, Sichuan, which was completed in 1990. The bridge is a half-through concrete ribbed arch bridge with rigid skeleton, with a span of 240m, which is the highest in the world at that time. Yibin Bridge adopts rigid skeleton to arch, hang formwork and cast-in-place arch rib concrete, which greatly reduces the lifting weight and ensures the safety of the arch. In the pouring process, the stress and deformation are adjusted by loading the water tank, which greatly saves steel. Modern computer technology and electrical measurement method are applied to the simulation calculation and construction monitoring of arch bridge, which makes the construction decision of arch bridge more scientific. The design and construction experience and scientific research achievements have greatly promoted the technical progress of super-large arch bridges in China. In the next few years. Dozens of arch bridges with spans over 100 meters have been built in China. The span of Yongning Yongjiang Bridge in Guangxi, which was built in 1996, was selected as 3 12m, which improved the world record of half-through rigid skeleton concrete arch bridge by 72m. The bridge is safer and more reliable than the water tank method by suspending rigid skeleton truss and pouring arch rib concrete to adjust construction stress and deformation. Wanxian Yangtze River Bridge in Sichuan is also a rigid skeleton concrete arch bridge with a span of 420m, which improves the world record of through arch bridge by 30m from 390m of KRKI Bridge in Yugoslavia. During this period, a river bridge with a span of 330 meters was built in Guizhou Province, ranking first in the world as a prestressed truss arch bridge. 1995, a 10-hole arch bridge with a span of 200m was built in Guangdong province, ranking first in the world. 199 1 year, the Bird's Nest River Bridge with a span of 120m was built in Fenghuang County, Hunan Province, which is the first stone arch bridge in the world. These span records, design and construction experience and scientific research results show that at present, China's arch bridges have leapt to the advanced ranks of arch bridges in the world.
(2) Main structural types of arch bridges in China.
1. Stone arch bridge is the earliest bridge built in China, including ribbed arch and slab arch.
2. Steel arch bridge: Before China collapsed into the world's largest steel producer in 1990s, there were relatively few steel products and few steel arch bridges were built. The longest span highway steel arch bridge is the 3003 bridge in Panzhihua, Sichuan. The span is 18 1m( 1969).
3. The types of concrete arch bridges are box arch, truss arch, slab arch, ribbed arch, rigid frame arch, truss composite arch, hyperbolic arch, tied arch, half-through arch and concrete filled steel tube arch. Many of them have reached the advanced level in the world.
(3) Construction method of China arch bridge.
Construction method is the most critical technology of long-span arch bridge. Non-support construction is the development direction of long-span arch bridge. At present, the main construction methods of arch bridges in China are:
1. Cable hoisting method
Cable hoisting construction method is one of the main methods to build long-span arch bridges in China. That is to say, the cantilever arch section is hung by tower, cable and buckle cable until it is closed. Generally, 3 ~ 7 segments are used in China, and some of them are as many as 1 1 segment, which is widely used in porous materials. Mamingxi Jinsha River Bridge in Yibin, Sichuan is a reinforced concrete box arch with a clear distance of 1.50m, which is hoisted in five sections and weighs 70 tons. Yupingshan Bridge in Nanping, Fujian Province, the loom rib arch has a clear span and is hoisted in five sections, weighing 59.6438+0 tons. Wanxian Yangtze River Bridge in Sichuan (L=420m) is also hoisted by cable, divided into 1 1 sections, with a length of 40m and a hoisting weight of more than 50 tons.
2. Rotating construction method
Half-span arch ring is poured on site and rotates horizontally or vertically around the arch frame. Among them, the arch bridge constructed by horizontal rotation is the first in China. Swivel construction method has developed rapidly in China in recent years and has been widely used in arch bridge construction. Huangbaihe Bridge and Xialaohe Bridge, the external highway of Three Gorges, are horizontal swivel bridges with balanced weights. The total weight of faucets is 3500 tons and 3600 tons, and the weight of faucets is the largest tonnage at present. The rotary spherical hinge is made of hemispherical steel plates, and the last two steel plates are precisely compressed and rotated. Wenfeng Road Overpass in Anyang, Henan Province is prefabricated in the opposite direction of the bridge axis, then rotated vertically to the required elevation, and then rotated horizontally to 180 degrees for closure.
3. Cantilever truss method
The truss composed of arch ring, column, temporary or permanent diagonal tie rod and upper chord is constructed by cantilever until it is closed. In China, it is mainly used for composite truss arches, all of which are cantilever assembled without temporary members, but with temporary prestressed tendons. The 330m-span Jiangjiehe Bridge uses steel herringbone mast as crane, and the maximum lifting weight is 120 tons.
4. Rigid skeleton and semi-rigid skeleton methods
The arch frame is made of section steel, and concrete is poured around the frame to form the arch frame. Strong skeleton method is rarely used in China, and semi-rigid skeleton is mainly used. Generally, after the skeleton is folded into an arch, it is divided into three layers: bottom, abdomen and top, and concrete is poured from the arch foot to the vault. In order to prevent the skeleton from becoming unstable, it needs to be weighed in the vault section and gradually unloaded with the concrete pouring to the vault section. Wanxian Yangtze River Bridge and Yongning Yongjiang Bridge are constructed by semi-rigid skeleton method, but steel pipes with a diameter of 40cm are added at the corners of their skeletons, and concrete is poured in the pipes after the skeletons are closed. So as to increase that rigidity of the bone. Wanxian Yangtze River Bridge divides each layer of concrete into six sections, which are poured symmetrically and synchronously, so that the skeleton deflects evenly, avoiding the unfavorable factors such as repeated deformation, heavy weight at the vault and saddle-shaped pre-camber when pouring from the arch foot to the vault, which is a great improvement of this method.
5. Arch construction method
Bailey truss is mainly used in our country, and some small bars are added to the upper chord to form Bailey arch frame for construction. For example, in Hunan, a single-layer Bailey arch frame is adopted, and the cables are stiffened and assembled into a cable Ziwan Shui Yuan Bridge with a span of 133m.
To sum up, we can see that there are many advanced and feasible construction methods in China at present, and a set of unique arch bridge construction methods without supports have been formed, that is, cable hoisting is the main method, combined with swivel construction method, semi-rigid skeleton method and cantilever truss method. Of course, it needs further development and improvement.
(D) the development direction of China arch bridge
1. The smooth arch of the circle
Lightweight arch ring can reduce the demand for hoisting capacity, save the engineering quantity of upper and lower structures and save costs. The box arch in China is limited by the hoisting weight, and there are many thick slats, which can account for 20 ~ 25% of the main arch ring, but they are not needed in stress. Therefore, in addition to reducing the thickness of thin-plate parts, lightweight arch rings are also developing towards wide boxes and fewer boxes to reduce the volume of web plates. The arch ring of three-chamber box composed of two boxes, one roof and one floor has appeared, and there is also a trend to rib arch, or box ribs, industrial rectangular ribs or even I-shaped ribs have been adopted. Lightweight arch rings also put forward stricter requirements for design and construction:
(1) Large deformation theory should be considered in design, and deflection theory or nonlinear finite element theory should be adopted in internal force calculation.
(2) The stability in construction, especially the out-of-plane stability of rib arch, is outstanding. Therefore, the construction measures of multi-section hoisting and single-section middle closure are often adopted to ensure stability.
2. Lightweight arch ring in construction stage
Directly affect the need to reduce the ability to improve. In the construction stage of some long-span arch bridges, the hoisting weight can be greatly reduced by using steel-concrete composite members or concrete filled steel tubes and pouring arch rings after closure. Semi-rigid steel tube skeleton may become the most promising construction method for super-long-span arch bridges. After the arch ring is lightened in the construction stage, the stability in the construction stage is a key technical problem. Considering the influence of geometric nonlinearity and physical nonlinearity, the stability coefficient of each step is calculated to ensure foolproof construction.
3. Tied arch and half-through arch are often used more.
Tied arch is a kind of structure without thrust, which has low requirements for pier and abutment. The whole bridge structure is simple and light, and the deck view is wide, so it is widely used in highway bridges.
In urban bridges and navigable rivers in plain areas, half-through arch bridges are often favored because they can reduce the bridge height, increase the rise-span ratio and reduce the thrust; The height of the bridge deck building is small, which can shorten the bridge length; Beautiful shape, adding scenery to the town; The cost is also low. At present, the development trend is relatively fast.
4. Concrete-filled steel tubular arch bridge has developed rapidly.
An arch bridge made of steel tubes or steel tube trusses and filled with concrete is called a concrete filled steel tube arch bridge. As a kind of steel-concrete platform material, concrete-filled steel tubular (CFST) can improve the stability, corrosion resistance and durability of the steel tube wall under compression with the help of concrete, on the other hand, it can hoop the concrete with the help of the tube wall. The compressive strength and ductility of concrete are improved. Organically combine steel and concrete; In architecture. Concrete filled steel tube can use hollow steel tube as rigid skeleton or even formwork, which has the advantages of light weight, fast progress and low steel consumption. Because of its superiority in materials and construction methods, it is very reasonable to apply this structure to arch bridges with stress as the main force. The appearance of concrete filled steel tube has solved two major problems of arch bridge materials and construction. Therefore, concrete-filled steel tubular arch bridge has developed rapidly in China.
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