Principle and applicable condition of LED display steel structure hoisting scheme
Time:2018-10-08
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The installation of LED display steel structure is a complex and comprehensive technology with many contents and a wide range.Combined with some steel structure projects, this paper expounds the basic principles and applicable conditions of the design of steel structure hoisting scheme, and summarizes the feasibility of conventional installation methods and corresponding technical measures.
With the development of science and technology, the shape and form of steel structure are more and more complex, which brings new challenges to the design and construction of steel structure.For example, the Olympic venues represented by "bird‘s nest" and "water cube", as well as influential steel structure projects such as the national center for the performing arts, the new CCTV site, guangzhou TV tower, and the stupas of famen temple, have not only innovated and developed in design, but also made new achievements in steel structure installation technology.Many mature and advanced technological methods have become working methods, which have promoted the development of steel structure industry.
Because of market reason, steel structure installation accident and illegal phenomenon happen from time to time, caused unnecessary economic loss and social influence.In order to further improve the overall level of steel structure construction and promote the development of the industry, steel structure construction should not only strengthen the management of the construction site, but also study and summarize the construction organization design, scheme and technical measures.Vigorously promoting new technologies and new technologies;According to the characteristics of the project, select advanced, reliable and economical construction scheme.
I. basic principles of the hoisting scheme of LED display steel structure
1. Policy: strictly implement the relevant national laws and regulations on production safety based on the drawings and in accordance with the standards.
2. Reliability: stick to safety first, ensure the feasibility of the scheme implementation and increase its reliability.No matter which method is adopted, the first thing to be considered is whether the scheme has a successful precedent and supporting equipment, otherwise the scheme must be demonstrated.It is proved that the stability of the structure, the stress and deformation of the bar meet the requirements.The mechanical equipment can meet the installation requirements.Whether the construction site conditions are satisfied, such as the civil construction environment and surrounding structures, whether the implementation of the scheme is restricted.
3. Advanced nature: with the development of science and technology, new technologies, new equipment and technologies emerge in the field of structural installation.Such as the advent of heavy duty cranes, computer synchronous control of the whole lifting and sliding technology for structural installation has added a new chapter.Especially for large steel structure projects, new technology and new technology should be promoted and applied when field conditions and structure form permit.Reduce the overhead work as much as possible, and improve the installation efficiency of steel structure.
4. Economy: a good installation plan should be simple, proper, efficient, low construction cost and wide application range, which can stand examination and test.Therefore, we must adhere to the principle of program comparison, carry out technical and economic analysis, and choose the program with short duration and low cost.
Ii. Applicable conditions of the hoisting scheme of LED display steel structure
Due to the disunity of building shape and structure form, the construction site conditions are quite different. It can be said that there is no one method or program applicable to the installation of any steel structure project, so each installation method has its own supporting conditions.
The common installation methods of grid structure include: upper bulk method, sub-block installation method, structural sliding method, support sliding method, integral hoisting method, integral lifting method, etc.
1. Considering by process method: understand the characteristics of structure form, structure weight, installation height and span, and try to select mature and advanced installation process based on the actual situation on site.
2. Consideration of lifting equipment: first, use the own equipment, make full use of on-site lifting equipment, and second, rent it nearby.General situation: when the number of components is small, more automotive cranes are used;The portal frame hoisting is mostly medium and small sized automobile crane;Crawler crane is more economical than truck crane when installation period is longer, installation height and larger radius of gyration.Hydraulic synchronous lifter (top push) is often used in integral hoisting and sliding.Tower crane is generally used for installation of medium and tall steel structures.The bridge is usually installed with gantry crane and bridge crane.
3. Upside-down construction: upside-down installation is a special installation process, which is applicable to structures with high aspect ratio, such as steel tower and mast.When the conventional crane is difficult to get close to the hoisting, the upside-down method is usually adopted.When adopting this method, we should consider the whole stability of the structure and the equipment itself, and have reliable supporting stability measures.Structural slip method - structural slip method has been developed to adopt hydraulic ejector and computer synchronous control technology, which is one step more advanced than the previous grid slide method.Its applicable condition is: first, because the field condition is limited, cannot set the crane and the support frame within the span;Second, the structure supporting conditions are favorable for laying track;Thirdly, the strength and stiffness of the calculated sliding element structure meet the requirements.Fourthly, understand the form of structural support and fixed methods;Fifth, the longer the longitudinal slip route, the higher the efficiency.Support frame slip method -- its applicable condition is to occupy span inside field, install height is lower, structural area is larger or longitudinal length is longer.First, when the installation height is less than 15 meters, the common steel pipe scaffold or the cup scaffold can be selected as the support frame.Second, when the frame body is high and bearing capacity is high, it is advisable to choose the shape steel support frame.No matter which scheme is adopted, the horizontal dynamic load should be considered in the design calculation in addition to the requirements of the specification, and the large inclined brace should be added when necessary to improve its overall stability.
4. Integral lifting method: the integral lifting method currently mostly adopts the computer synchronous control and hydraulic lifting equipment developed by tongji university.It is applicable to the following conditions: first, it occupies a cross-site space;Secondly, the installation height is high.Third, the components are heavy;Fourth, limited to vertical lifting, cannot horizontal displacement.That is, the higher the installation height, the heavier the lifting weight, the better the effect.
5. Earth hoisting: earth hoisting is to use unicorn bar, herringbone rack, winder and pulley group as lifting equipment to carry out structural hoisting.As there are more and more heavy lifting equipment and advanced installation techniques, there are fewer and fewer earth lifting.
6. Rotary construction: this method is mainly used for bridge installation. Due to the influence of railway and highway traffic, as well as the special environment such as mountains, rivers and ditches, other bridge construction methods are mostly adopted when they are limited.
7. Integral hoisting method: it is basically similar to the integral lifting method, except that the lifting equipment is different, which is suitable for small and medium-sized structure installation.In the early stage, the multi-taiwan independence pole or herringbone, winch, pulley block and cable wind system were adopted for large tonnage hoisting.Now, as there are many large tonnage cranes, several cranes are selected for installation in small and medium sized projects.
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