Summary of the invention
The present invention needs arch structure and support system thereof are carried out precompressed in order to solve in existing traditional large-span steel-reinforced concrete arch structure construction, not only to drop into a large amount of labours, vertical transport and weight material, speed of application is slow, and problem such as form removal rear arch body concrete surface impression is relatively poor, a kind of prepressing-free construction process for large-span steel-reinforced concrete arch structure is provided.
The present invention adopts following technical scheme to realize: prepressing-free construction process for large-span steel-reinforced concrete arch structure may further comprise the steps:
(1) Foundation Design: piling base, cushion cap, arch springing;
(2) set up support system along arch structure axis two ends symmetry;
(3) determine camber, build monolithic arc bed die on support system, the arc bed die leaves the closure section at the vault place;
(4) arch structure is carried out construction section and divide, then along the section construction of span of arch direction symmetry;
(5) in each construction section, at first on bed die by two ends to middle assembling reinforcement, prop up side form then, construction section normal direction template is set, Zhi Dingmo, the installing with concrete construction height with beating of backform, the monolithic backform is 1-1.5 rice along the donor arc to the width of direction, last concreting; Treat to remove backform, side form and normal direction template after the concrete final set, constuction joint is a normal direction after the normal direction form removable, the processing method of constuction joint be at first rejecting surperficial laitance and loose concrete, picks crucial point and exposes water flushing behind the stone, moistening getting final product, and carries out next section construction then;
When (6) treating construction closure section to the end, arc closure bed die tunable arrangement is installed on support system, a side form, concreting, the environment temperature during the arch structure closure section construction is controlled at 5-15 ℃;
Require the donor concrete strength to reach 100% design strength when (7) bed die is removed, consider the system conversion of structure when falling frame, according to low, first intermediate and then both sides, the high back of elder generation, the principle of segmentation symmetrical construction is removed support system.
The partition length of construction section of the present invention can be decided according to on-the-spot actual needs.
Arc closure bed die tunable arrangement of the present invention is to be " arc closure bed die tunable arrangement in the large-span steel-reinforced concrete domes construction technology " in denomination of invention, the patent No. is a disclosed patented technology in 200620023362.3 the application documents, so do not do detailed description at this.
Because arch structure can produce following elasticity and nonelastic deformation in construction and after removing the support system conversion: the A. arch ring is because the elastic deflection that deadweight is produced; B. arch ring is because of elastic deflection that variations in temperature produced; C. arch ring is subjected to squeeze the elastic deflection that produces with displacement because of cushion cap; D. arch ring answers hardening of concrete to shrink and the nonelastic deformation of generation; E. elasticity and the non-resilient sinking of bow member under design load; F. the nonelastic deformation behind the elastic deformation of support system and the basic stand under load, the camber of these domes is determined according to following second-degree parabola, σ
x=α σ (1-4x
2/ L
2), wherein σ is that vault always adds height in advance; L is the arch ring span; X is the horizontal range of span centre to the arbitrfary point; α is pre-arch correction factor, gets 0.5-1.0, and this formula is that the applicant gets summing up on the basis of determining of camber and through theory analysis, calculating and practical experience according to existing method.
Vault of the present invention closes up the part bar splice and adopts cold extrusion or welding manner to connect, and the bar splice at other position adopts straight thread to connect.
Since the reinforced concrete arch span greatly, highly high, working load is big, intensity, rigidity, stability, globality to support system in the construction have very high requirement, the kind of support system is a lot of at present, and support system of the present invention adopts the bowl fastening type scaffold building.As calculated, support system stability is higher, sets up under the prerequisite of quality in assurance, can support upper load fully.
The present invention is since second construction section, build the 1-2m slightly expanded concrete during every section construction earlier,, produce the crack to control every section concrete shrinkage strain, vault closure section concrete also adopts slightly expanded concrete, and slightly expanded concrete designs concrete grade and improves a grade.
Compared with prior art, why the present invention can realize exempting from precompressed, its basic innovative point just is that vault is reserved with the closure section, the distortion that makes arch structure be produced in work progress discharges fully, according to the real size of closure section arc closure bed die tunable arrangement is installed then, whole construction technology has the following advantages:
1, construction safety, simple to operate;
2, camber distortion is controlled, and the camber value is more accurate, and this job practices can pre-control to eliminating support system elasticity and nonelastic deformation, thereby guarantees the construction precision of domes;
3, donor surface circle is suitable, smooth, the arch color and luster is even, and common quality defects such as concrete face crack and honeycomb, pitted skin, faulting of slab ends do not take place, and has guaranteed construction quality, and the arched girder quality after the closure meets the requirement of design, job specfication, produces a desired effect;
4, simplified working procedure, shortened the duration greatly, compared with case history of the same type, work efficiency can double, for advantage has been created in the overall completion of follow-up engineering and engineering;
5, avoid using a large amount of weight material, reduced the input of a large amount of construction machineries and manpower, greatly reduce construction costs;
6, the present invention carries out the overall process monitoring to the stress in the donor work progress, strain, understands the effective and operability of construction technology by the data analysis and the entity certificate of inspection;
In a word, by adopting job practices of the present invention, its construction quality has reached the national acceptance standard, has obtained good social benefit and economic benefit.
The specific embodiment
Embodiment: with certain college sports shop large-span steel-reinforced concrete arched girder is that example describes,
One, project profile: have the parallel reinforced concrete arch north-south of twice to cross over the sky, sports palace in this project, in order to support its roof system; The central span of this arch is 115m, and spring of arch is 32m; The two ends of arch are the entity section, and the middle part is the rectangular enclosure section; Sectional dimension is high 2.5m, wide 1.5m, and cavity part wall thickness is 400mm; Twice arch axis linear distance is 24 meters, is steel work arch net shell between two arches.
Two, constructure scheme:
1, arch base plinth is made up of pile foundation and cushion cap, and cushion cap is a box foundation, has all designed a box foundation under each arch springing, and planar dimension is 18.5m * 10.5m;
2, support system adopts the bowl fastening type scaffold building, and set up along arch structure axis two ends symmetry, according to arch structure span and load, through calculating the scaffold horizontal spacing is 900mm, and longitudinal pitch is 1200mm, and horizontal step pitch is 1200mm, the 450mm place sets up one vertical rod respectively in vertical rod both sides, middle part, adopt the fastener type scaffold building, and increase the two-way horizontal bar, to bear the big load in top;
3, behind measurement and positioning, on support system, build monolithic arc bed die, the camber of arch structure can be according to formula σ
x=α σ (1-4x
2/ L
2) pointwise determines;
4, template adopts the steel large form, arc bed die whole set of installation, side form and backform are pressed construction section quantity turnover and are used, because of the concreting of backform effect of altitude, so backform with the concrete construction height with beating, the monolithic backform is processed into fillet, it is 1-1.5 rice along the donor arc to the width of direction, like this, not only more helps exhaust, vibrate conveniently, and form removal rear arch surface impression quality height;
5, as shown in Figure 1, arch structure is divided into four construction sections, first, second and third construction section is in turn along span of arch direction symmetrical construction, wherein the sequence of construction of each construction section is as follows, on the arc bed die, tie up end muscle → tie up a sidewall and top rebars → installation built-in fitting → side form → construction section normal direction template → cleaning foreign material → Zhi Dingmo → concreting, for reducing every section concrete shrinkage strain,, build the long slightly expanded concrete of 2m earlier for every section at second and third, when four construction sections are constructed; The 4th construction section that is positioned at vault is the closure section, when constructing the closure section, after reinforcing bar binding is finished, arch structure has produced elastic deflection and sinking distortion owing to be subjected to the various factors influence in work progress, make arc closure bed die tunable arrangement according to real size and be installed on the support system this moment, prop up side form then, build slightly expanded concrete.Environment temperature during the arch structure closure section construction is controlled at 5-15 ℃;
6, in work progress, treat to remove backform, side form and normal direction template after the concrete final set, because bed die is removed and support system falls frame must just can carry out after donor closure back and concrete strength reach 100% design strength, should formulate the dismounting scheme, by the middle part to both sides piecemeal symmetry remove bed die, according to low, first intermediate and then both sides, the high back of elder generation, the principle of segmentation symmetrical construction is removed support system.