Tower crane in the construction project layout and positioning is not reasonable or error is divided into the following categories.

(1) in the construction organization design only pay attention to the efficiency of the use of engineering and ignore the technical requirements of tower crane installation.

Most of the equipment of this type of user comes from the leasing channel. "Paid the rental fee should meet the use", the loss caused by the arrangement or positioning to transfer to a third party or shared by both sides, in order to the lessor to develop remedial measures for them. In the usual construction process, the construction unit because of the lack of understanding of the technical performance of the tower crane before installation, only pay attention to the maximum use of the project, consider the surrounding building residential building construction convenience and coverage, and ignore the tower crane after the elevated attachment requirements, resulting in the tower crane more than the basic height and the building can not be attached, the tower crane and each residential building distance are greater than 10m, must design special attached wall device to be reinforcement. Due to the tower layout and positioning errors caused delays and increased costs.

In addition, in the building is a curved block of high-rise residential construction, if the construction unit in the installation of a QTZ80 tower before the lack of reasonable choice of tower installation base and positioning demonstration, could have used track walking type, in order to dismantle the tower before walking through the tower to avoid the curvature and lower the tower, but made into a fixed base type, resulting in the tower demolition lower section when the front end of the boom and balance arm tail end and curved building touch, can not be lowered, only to choose the 150m tower. Can not lower the section, only to choose 150t truck crane, directly from nearly 50 meters aerial demolition, both increased the risk of high-altitude operations, but also increase the cost of demolition. If walking, demolition only need to lower the tower to a height of 19m, using 25t truck cranes can be demolition operations, can reduce the cost of 70%, such as a residential site in Nanjing Jiangning, a QTZ40 tower crane installed in the center of the walkway outside the residential building, tower 3 sides surrounded by buildings, demolition can not be lowered, had to choose a large tonnage truck crane high-cost demolition.

(2) in the construction organization and design of the construction unit without engineering geological survey report on the construction in a hurry.

Construction units in order to meet the schedule, the engineering foundation information, geological reports are not meticulously studied on the haphazard layout of the tower, due to the foundation foundation problems caused by positioning errors also occur. In Shanghai Songjiang a site, the use of units due to the lack of detailed understanding of the foundation, random layout of the tower, make the foundation and install the tower, in less than 5 days of installation, found that the foundation is seriously sinking and tilting phenomenon, had to immediately remove the tower just installed, the implementation of remedial measures to increase the construction cost. If not found and removed in time, it is likely to cause safety accidents.

(3) in the construction organization design, although the layout of the tower positioning has been repeatedly demonstrated, but limited to the construction conditions as a last resort.

In Nanjing Xinjiekou is located in a busy area of the Wanda Plaza project construction site is small, the project is 120m long, 90m wide 5-story building. The layout of the tower crane was technically proven by the construction unit and installed in the center 1/3 of the project. Due to insufficient consideration of the demolition plan, after the completion of construction to dismantle the QTZ80 tower located in the center of the project, after a multi-programme demonstration and screening, must use more than 200t truck crane to meet the requirements of demolition operations. In the work radius of 42m, the 200t truck crane 54m main boom plus 12m jib, demolition operations. Because Nanjing Xinjiekou is located in a busy area, construction work is not allowed during the day, all work must be carried out at night, so that the demolition work increases the risk of working at height, while the demolition costs are also quite large. To sum up, the layout and positioning of the tower crane is very important, and the tower crane in the project layout and positioning of the determining factors are also multifaceted.
In order to do a good job in the construction of a reasonable layout and positioning of the tower, from the following aspects.

(1) choose the tower model. First of all, according to the maximum weight of the project unit for selection, the tower crane lifting capacity, installation height and lifting arm length to be determined. Secondly, to understand the technical performance of the tower crane and installation of the basic requirements, whether its coverage can meet the use of the requirements, whether there are "dead ends" and "blind spots" within the scope of operation, to provide the basis for the reasonable layout and positioning of the tower crane.

(2) determine the number of towers required. Sometimes to reduce the blind spot, a project needs more than one tower crane work at the same time. In the construction organization design, the reasonable arrangement of multiple tower operations, is also one of the main focus of the construction process.

(3) determine the layout of the tower plan. Model, number to determine, according to the characteristics of the project to determine the layout of the tower program. Large project multi-tower operation focus is the selection and positioning, that is, how to carry out the reasonable layout of the tower, both to understand the project profile, clear progress on each node and the lifting and transportation requirements in each link, but also to have a scientific and economic theory of Shin Shin's calculation.

(4) determine the tower positioning point, calibrate the tower foundation load. After the tower layout program to determine the foundation positioning point. The reasonable choice of foundation positioning point depends on the "up", "down" two points: "up" refers to the tower foundation positioning point corresponding to the building has the attachment conditions;. "Under" refers to the tower foundation positioning point corresponding to the foundation bearing capacity can meet the requirements. The tower foundation must meet the tower stability, foundation strength and foundation uniform settlement of these 3 requirements.

(5) do a good job on site technical survey, understand the project surrounding environment. In the tower layout and positioning plan to determine before, but also the project surrounding environment for a detailed survey, whether there are obstacles affecting the operation of the tower, such as high-rise buildings, high-voltage lines, etc., but also to estimate and understand the environment when the removal of the tower, while familiar with the road into and out of the field, whether there are obstacles affecting the transport of the tower, such as underground pipelines, cables, etc..

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