CONSTRUCTION METHOD

Abstract: The invention concerns a method of building an arch, wherein the prefabricated arch units are lowered all at once to rest on end supports using a crane. No supporting bottom structures are used under the arch, which makes the method simple and cheap to implement.

Description: CONSTRUCTION METHOD. TECHNICAL FIELD The invention relates to building technology and it concerns a method of building arches and prefabricated units for use in the method. TECHNICAL BACKGROUND An arch or vault is a supporting arc-like structure made of pieces and supported by end supports to span an open space and having a bearing capacity based mainly on bearing stresses. Arched constructions have been used for more than 2000 years. In known arch building methods a supporting bottom structure is first made and the arch pieces are then piled on top of it. Upon completion of the arch the suppor¬ ting bottom structure is removed. GENERAL DESCRIPTION OF THE INVENTION It has now been found that an arch can be built without using any supporting bottom structure when the arch units are placed to rest on end supports all at once using a crane. The invention and some advantageous embodiments are de¬ fined in greater detail in the appended claims. DETAILED DESCRIPTION OF THE INVENTION The method is intended for building relatively large arches of an approximate minimum length of 5 metres. The arch consists of at least three prefabricated units, but there are always considerably more units in practice, for example, no less than eight. The units are preferably made of concrete or stone. The prefabricated units are lowered into their positions in the arch to rest on end supports all at the same time by using one or several cranes. When two or more cranes are used quite large arches can be built. The units are preferably first joined together into bigger arcs, wherein they are supported separately. It must hereby be made sure during hoisting that the units remain in the desired arc-like shape. This can be made, for example, with the aid of a hoisting beam in the direction of the arc, from which beam each unit is suspended with a rope of suitable length. The units may also be attached suitably to each other to keep them in the shape of an arc during hoisting. They may be formed first, for example, into arch halves, which are then lowered into position using two cranes. The arcs may be formed on a sui¬ table base shaped like an arc. The prefabricated units are made with suitable means for securing them to the hoisting equipment. The units are preferably of such a wedge-like shape that their meeting surfaces are pressed directly against each other in the completed arch structure. However, wedge-shaped seams may also be made between the units, whereby different arcs can be made of similar units. Wedges of some kind can hereby be used between the units to set the units in the desired arc-like shape before seaming. The weight of a prefabricated unit could be, for example, in the range of one ton. The prefabricated units are preferably made of concrete, but other materials such as stone may also be used. Some advantageous embodiments of the invention are described in the following referring to examples. In the drawings of the description - Figure 1 shows the manufacture of an arch structure to be used as a casting mould for the concrete arc, - Figure 2 shows the manufacture of an arch structure formed of prefabricated units to be filled by grouting, - Figure 3 shows the manufacture of a smaller arch structure formed of units to be filled by grouting, and - Figure 4 shows a vaulted bridge for light traffic. In Figure 1 an arch structure is formed of prefabricated concrete units 2.1 resting on end supports for use as a casting mould for a concrete arc. The units 2.1 are downwardly wedge-shaped, so that by placing them one after another the desired arch can be formed without needing any seaming material between them. The units have walls 4 rising upwards at the side edges of the bottom 3. This arch structure has three arch units in parallel. The unit size may be, for example, about 2x2 metres and the unit weight, for example, about 500 - 2000 kg. Each arch 3 in this embodiment is made by lowering the arch halves 5 formed of units 2.1 both at the same time to rest on supports 1. Hoisting beams 6 in the longitudinal direction of the arch are used as hoisting means, from which the units are suspended with the aid of ropes 7 of a suitable length, so that the arch half remains in the desired shape during hoisting. In addition, the units can be attached to one another in a suitable way to prevent them from moving during the hoisting operation. For suspending, the units 2.1 have two holes 8.1 extending through the side walls 4 with bars 9 pushed through the holes. Ropes 7 are attached at the middle of the bars. Using the holes 8.1 it is possible to attach adjoining units 2.1 to one another, for example, by using a through- going bar. The structure is then braced also in the trans¬ verse direction. The meeting ends of the arch halves 5 may also be attached together just before being lowered into their positions. In this way the ends are made to go immediately into their exact positions. Such fastening may be temporary. It can be made, for example, with bolts, a steel bushing or slot joint . Upon completing the arch structure it is reinforced in the required way and casting is performed. Figure 2 shows an embodiment where a light arch structure is first made of box-like units 2.2 resting on supports l. Thereafter concrete is cast into the elements to make a strong supporting arch. A hole 8.2 extends through the side walls 4 of the units 2.2 at the centre, through the point of gravity, and a bar 9 is placed into the hole. Each unit is suspended from a hoisting beam 6 with a rope 7.2 of suitable length. Other holes 10 also extend through the side walls 4 of the units 2.2. Using these the units to be placed side by side in the structure can be attached to each other to form one arch unit. This is preferably done by using a bar, extending through the entire structure. Holes 12 extend through the end walls 11 of the prefab¬ ricated units 2.2. From these the units can be mounted lightly to one another for hoisting, for example, using bolts. For hoisting, the units 2.2 are first placed onto a suitably arc-like base 13, where they are joined together to form arch halves 5. If e.g. rectangular units are used wherein the surfaces do not come closely against one another in the completed arch structure, seaming may also be done on the arc-like base 13. Figure 3 shows the manufacture of a similar structure as in Figure 2. Here, however, the entire arch is lowered into position using one hoisting beam 6. This method is suitable for making lighter structures. Figure 4 shows a bridge for light traffic formed of prefabricated units 2.3. In principle, the units are similar to those in Figure 1. In addition, they have railing units 14, which are joined together in the completed bridge and, for example, coated in a suitable manner to form a railing. According to the invention, the arch structure can be made without any supporting bottom structures. To place the units into position one only needs such conventional hoisting equipment which is used normally on building sites. If desired, the invention may of course also be applied for building arches having several criss-crossing arcs.

Claims: CLAIMS 1. Method of building an arch of prefabricated arc-like units resting on end supports, characterized in that the arch is built from at least three, preferably from at least about eight prefabricated units in such a way that the units are lowered all at the same time to rest on end supports using one or several cranes. 2. Method according to claim 1, characterized in that before lowering the units into position they are formed into an arch or into arch components wherein there are no less than two, preferably no less than four arc-like units. 3. Method according to claim 2 or 3, characterized in that before being lowered into position the units of the arch or arch component are attached to one another. 4. Method according to claim 2 or 3, characterized in that for being lowered into position the units of the arch or arch component are attached each one separately to the hoisting equipment of a crane. 5. Method according to any one of claims 1 - 4, charac- terized in that the arch is built of wedge-shaped units, which when placed after one another with wedge-like surface against wedge-like surface form an arch of the desired shape. 6. Method according to any one of claims 1 - 5, charac¬ terized in that the arch is built to form a casting mould for a vaulted concrete bridge. 7. Method according to any one of claims 1 - 6, charac¬ terized in that the arch is built of box-like casting moulds. 8. Prefabricated arc-like unit for an arch, wherein there are sides in the direction of the arc and ends in a trans- verse direction to the arc, characterized in that it is intended for use in a method as defined in any one of claims 1 - 7. 9. Prefabricated unit as defined in claim 8, characterized in that it has walls (4) extending upwards at its sides. 10. Prefabricated unit as defined in claim 8 or 9, charac¬ terized in that at least one hole (8) extends through the sides in a transverse direction to the arc.

Inventors: RUUSUNEN JARI, RUUSUNEN, JARI
Applicants: RUUSUNEN JARI, RUUSUNEN, JARI
Application year: 1993
Main classification: E01D3
IPC codes: E01D1, E01D4, E01D21, E01D101, E04C3