1、 附录 英文翻译 : BEAMBRIDGE In designing a bridge, preference is often given to beam structure, unless it has a very long span. Simple in structure, convenient to fabricate and erect, easy to maintain, and with less construction time and low cost, beam structure has found wide application in bridgework. I
2、n 1937, over the Qiantang River, in the city of Hangzhou, was erected a railway-highway bi-purpose bridge, with a total length of 1453m, the longest span being 67m. When completed, it was a remarkable milestone of the beam bridges designed and built by Chinese engineers themselves before liberation.
3、 Since 1949, this kind of bridge has made giant strides. Reinforced concrete beam structure is the most commonly used for short- and medium-span bridges. A representative masterpiece is the RongJiangBridge completed in 1964 in the city of Nanning, the provincial capital of Guangxi Zhuangzu Autonomou
4、s Region. The bridge, with a main span of 55m and its cross section of a thin-walled box with continuous cells, was designed in accordance with closed thin-walled member theory, the first of its kind in China. Pre-stressed concrete girder bridges cover a wide range of spans and types. In the short s
5、pan range, pre-cast AASHTO beams with a composite cast-in-place non pre-stressed concrete slab are frequently used for simple spans. A similar form of construction is used for partially continuous spans using I-girders and box girder in the medium span range .In the medium to long span range, contin
6、uous pre-cast segmental box girders are common, while the longest spans are generally cast-in-place segmental box girders. For cost-in-place construction, the girders and slab are generally formed together and both cast before formwork and supports are removed. This construction is fully composite f
7、or dead load and live load. The usual cross sections are T-beams and box girders. Spans are usually continuous, and transverse post-tensioning of the slab is frequently prescribed to allow the use of thinner slabs or a reduced number of longitudinal girders at a larger spacing. Since longitudinal po
8、st-tensioning is required on site, transverse post-tensioning is usually economical and normally used. The design and analysis items given for reinforced concrete girder bridges also apply to pre-stressed girder bridges. For the box girder section, a detailed transverse live load analysis of the sec
9、tion should be carried out. Temperature effects are important for box girder, due to the possibility of large differential temperatures between the top and bottom slabs. For cast-in-place segmental construction built by the balanced cantilever method, a knowledge of the exact construction loads is n
10、ecessary, in order to calculate stresses and deformations at each stage. A knowledge of the creep characteristics of the concrete is essential for calculating deformations after the addition of each segment, and also to calculate the redistribution of moments after completion and final stressing. St
11、andard pre-cast, pre-stressed beams cover spans up to the 140ft (43m) range. After the beams are erected, forms for the slabs are placed between the beams and a reinforced concrete slab cast in place. The slab and beams act compositely for superimposed dead load and live load. Intermediate diaphragm
12、s are not normally used , and the design and analysis items given for reinforced concrete girder bridges, also apply to pre-stressed multi-beam type bridges. Pre-cast pre-stressed beams can be made partially continuous for multi-span bridges. This system is not only structurally efficient, but has t
13、he advantage of reducing the number of deck joints. Support moments are developed due to superimposed dead load, live load, differential temperature, shrinkage and creep. Continuity for superimposed dead load and for live load can be achieved by casting diaphragms at the time the deck concrete is pl
14、aced. Reinforced steel placed longitudinally in the deck slab across the intermediate pier will resist the tension from negative moment at the supports. At the diaphragms, the bottom flanges of adjacent beams should be connected to resist the tensile stress due to positive moments generated by diffe
15、rential temperature, shrinkage and creep. Continuous spans , beyond the range of the type pre-cast girder, temporarily supported on bends, with joints near points of minimum moment, are post-tensioned for continuity after placement of the deck slab. The maximum lengths of segments are usually determ
16、ined by shipping length and weight restriction. Pre-cast segmental construction employs single or multiple cell boxes with transverse segments post-tensioned together longitudinally. For medium sans, the segments may be erected for the full span on falsework before post-tensioning. Longer spans are
17、usually erected by the balanced cantilever method, where each segment is successively stressed after erection. The design and analysis considerations given for cast-in-place segmental construction also apply to pre-cast segmental construction. The deformation of the structure during cantilever erection is dependent upon the time difference between segment pre-casting and erection. The design calculations may need to be repeated if the construction schedule differ from that assumed at the design stages.
