The contents of the design drawings of bridge construction engineering are different from those of the design drawings of house construction engineering. As the basic data for compiling the project cost, the project quantity is usually calculated by the designer while completing the design drawings. Before compiling the project cost, the cost engineer needs to be familiar with the design drawings and check the engineering quantity, so the key to compiling the cost is how to correctly extract the engineering quantity from the design drawings and apply the appropriate quota. In the compilation of cost documents, bridge engineering is more complicated, which accounts for a large part of the cost documents. At the same time, the continuous development of bridge design and construction technology and the wide application of new structures, new materials and new technologies in recent years have increased the difficulty in compiling project cost.
1, and the quantities are extracted in sequence.
There are many projects in the compilation of bridge engineering cost documents, and the calculation and extraction of engineering quantity are also difficult. Experience shows that it is more accurate and faster to extract quantities according to the usual construction process. At present, the list of bridge engineering projects compiled by the Ministry budget is based on the order of foundation → lower engineering → upper engineering → renovation engineering, and the auxiliary engineering is listed in the corresponding engineering part at the same time, so as to systematize the working procedures and avoid the mistakes of missing items or repeated calculation to the maximum extent.
2, the bridge foundation engineering
2. 1 foundation pit excavation
According to different conditions such as earthwork, stonework, silt, quicksand, depth of foundation pit, dry place or wet place. , respectively calculate the excavation quantities of foundation pit, reasonably determine the types and quantities of cofferdams in combination with the river bed water level and overburden soil quality during the construction period, and determine the maximum consumption of drainage pumps in foundation pit, as well as the safety technical measures that must be taken. Understand the long-distance transportation and treatment of foundation excavation waste, and restore the original topography and rivers. The above items are determined according to the principle of proceeding from reality and leaving no hidden dangers, and the required expenses are included in the project cost.
When compiling the cost, we should fully understand the water flow of the bridge. Some rivers belong to seasonal rivers. When the dry season is long, construction can be considered in the dry season. At this time, there is no need to consider auxiliary projects such as cofferdam and drainage.
2.2 foundation engineering
The foundation works of the bridge include masonry, concrete, open caisson, piling and filling pile, masonry and concrete expansion foundation forms. Masonry foundation shall be statistically summarized according to flaky and rubble respectively. If the mortar design label is different from the quota when compiling the cost, the mortar label should be replaced. Concrete foundation should be statistically summarized according to different strength grades and whether flaky is mixed. If the concrete design strength grade is different from the specification, the concrete strength grade should also be replaced. The construction technology of bored pile foundation is complicated. When compiling the cost, we should combine the actual situation and the implementation of the construction organization plan, and pay attention to the following points:
(1) According to the construction situation and the soil quality of the hole, you can choose manual digging, hole pushing or mechanical drilling, and then apply the corresponding quota according to the drilling length corresponding to different soil thickness in the design document. At this time, it should be noted that the total hole depth quota is implemented for different soil qualities in the same hole, regardless of its depth.
(2) When the cofferdam is used for island filling in drilling construction, the quantities of cofferdam and island filling can be determined according to the outer edge of the cast-in-place pile of about 3.0m.
(3) The liners buried in a dry place can generally be calculated according to the length of each liner of 2.0m or the number of rings provided in the design documents, and the turnover amortization amount of the weight of liners in the quota will not be recovered; Steel liners buried in water are calculated according to the total design quantity, and the recovery quantity is calculated according to the design requirements. When calculating the number of steel liners, the quantity and quality of steel liners in dry water and water are calculated according to the water level investigated on site.
① Manual digging pile
② Mechanical pore-forming.
For steel lining, the following points should be noted:
(1) If the cofferdam is used in water, it will be considered according to the land conditions, and the steel casing will not be used for the whole length. At this time, the calculation and application of buried lining number should be regarded as a dry place. By comparing the unit price of dry and wet parts of steel casing, the unit price of wet part per ton of steel casing is about 5~6 times that of dry part. Therefore, the dry or wet part quota of the gasket should be correctly applied, otherwise the deviation of the manufacturing value will be great.
(2) In general, the length of each pile casing is 2m. When the casing is dry-treated, the design generally requires that the buried depth is 1.5m, the periphery is compacted with 0.2m clay, and the total length is 1.8m+0.2m=2m. Therefore, when the casing is buried in a dry place, its length should be calculated as 2m.
(3) When the pile casing is submerged in water, when the water depth is less than 5m, the general design requires the buried depth to be 3m, and the actual length of the pile casing is 8m.
④ Determination of cylinder diameter. The diameter of the protective foundation can be determined with reference to the relevant provisions of the bridge construction code. The diameter of casing is related to the type of drilling rig and geological conditions. In general, it is enough to add about 0.2m according to the pile diameter.
(4) When drilling in water, the working platform of cast-in-place pile, mud boat and circulation system shall be listed.
(5) There are 8 kinds of soil-taking quota for drilling, and they are divided into several quota standards according to the pile diameter and hole depth. Therefore, the number of drilling holes should be determined according to the geological drilling data and the fixed soil type. Because the unit of measurement for drilling holes is meters, the drilling depth should be based on the depth between the ground and the design pile bottom. When the cofferdam is used for island filling in water, the depth between the top surface of the cofferdam and the design pile bottom should be based on this. If drilling waste needs long-distance transportation, it shall be separately priced according to the average transportation distance of waste.
3. Bridge substructure engineering
Bridge substructure works include masonry, cast-in-place concrete and precast concrete members.
(1) When compiling the expenses, the quantities will be extracted one by one according to the partial projects and priced separately. The valuation quantities of pier and abutment are pier body, wing wall, pier cap, arch frame, capping beam, ear back wall, etc. To distinguish the different strength grades of mortar and concrete, the filling and tamping in the cone slope should also be priced separately. If the abutment backfill is considered above the subgrade, it will not be priced in the bridge, but if the subgrade earthwork is not considered, it should be priced.
(2) Where piers, abutments, arch stones, cap stones and railings are made of mortar concrete precast blocks, the number of precast blocks shall be based on the design masonry multiplied by the coefficient of 0.92.
(3) Sometimes the designer neglects to write the abutment capping beam as abutment cap, and the cost personnel directly adopt the abutment cap quota without consulting the drawings, which is inappropriate, because the pier cap quota does not consider the cost of bottom formwork, and the capping beam construction needs bottom formwork.
pier
be adjacent/next/contiguous to
4, the bridge superstructure engineering
The superstructure of a bridge is usually divided into roadway, deck pavement and sidewalk, and there are different structural forms such as masonry, cast-in-place concrete, precast concrete members, steel trusses and cable suspension bridges. In order to avoid repetition and omission, the valuation quantities of superstructure should be extracted in the order of roadway → deck pavement → sidewalk.
4. 1 Prefabrication and installation of main structure works
At present, prefabricated concrete structures are mostly used in bridges. When compiling the cost, prefabricated components should be divided into three construction processes: prefabrication, installation and transportation, all of which are subject to the design volume of components; Steel bars, steel strands or high-strength steel wires, cast-in-place reinforced concrete, drainage pipes, supports and expansion joints shall be subject to the quantities provided in the design documents. If the service life of lifting equipment exceeds 4 months specified in the quota, the amortization fee of the equipment can be adjusted according to the planned construction period. The planned service life of the equipment shall include the round-trip transportation between the equipment warehouse and the construction site, the trial assembly before installation and all the time required for cleaning, trimming and painting after dismantling; The quantities of small components such as prefabricated sidewalks, kerbs, railings and handrails should be increased by 65,438+0% according to the volume of the designed components.
4.2 Prefabrication and installation of structural accessory works
Sometimes the unit price of bridge superstructure is always very low, such as C50 precast concrete T-beam, which is usually 1000 yuan /m3, but sometimes it is 700 yuan /m3, which is very low, mainly because ancillary works are not considered. The auxiliary project for prefabrication and installation of prestressed T-beam is shown in the following figure:
(1) The site leveling area of the prefabrication yard shall be determined according to the scale and construction period of the construction project.
(2) The number of plane bases of large prefabricated members shall be determined according to the number of times that the construction progress may be reused. If two bridges * * * use prefabricated yard, one bridge has 80 T-beams with 25m length and the other bridge has 7 T-beams with 30m length. The construction pedestal was originally planned to be 16, but considering the length of the second bridge is 5m, 12 pedestal was finally adopted. During construction, 25mT beam is prefabricated first, and then 30mT beam is prefabricated.
(3) The gantry of the prefabrication plant can generally be compiled according to the construction organization plan, and then the amortization fee of the equipment can be adjusted according to the planned service life of the equipment.
(4) Lifting equipment such as double guide beams can refer to the mileage given in the quota. There are a variety of construction methods and supporting hoisting equipment for component hoisting in the budget, but each has its own scope of application. When compiling the cost, the appropriate hoisting equipment should be selected according to the upper structure form and construction technology, and there should be no omissions.
(5) If conditions permit, the existing subgrade can be used as the prefabrication yard of the superstructure, which not only saves money, but also facilitates the transportation and construction of beams.
5, steel engineering
Steel works and concrete are measured separately, and the unit is tons. The quantities shall be extracted respectively according to the requirements of divisional works and primary and secondary steel bars.
(1) Steel bars shall be listed according to the weight provided in the design documents. When applying the quota, the actual amount of primary and secondary steel bars should be changed respectively.
(2) The number of steel strands and high-strength steel wires is the sum of anchoring length and working length. For example, the prestressed hollow slab with the length of 10~ 16cm can generally be calculated as the increase of slab length1.5m..
(3) When setting the steel strand quota, attention should be paid to the number of holes of steel strand group anchors, and the number of steel strand bundles is half of the number of corresponding anchorage groups.
Abutment slab reinforcement
6. Summary
As cost personnel, we may not know much about the construction technology and technology of bridges, especially those with new structures, new materials and new technologies. This requires us to go to the construction site when we have the opportunity, learn more about and be familiar with the new construction technology and technology of bridges, and know more about the relevant aspects at ordinary times, so as to calculate the cost that can truly reflect the specific situation of bridges.
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