Mechanical Analysis Of Fastener Type Steel Tube High Formwork Support

The fastener steel pipe formwork and scaffold system is widely used in practical engineering.However,in the process of construction,there are a lot of unstable and unsecured factors in the scaffold system,such as stability failure,inadequate bearing capacity of foundation and so on.It causes that formwork support system collapse accidents often happen.The safety accidents seriously affected the normal construction and the normal use of the buildings.Through the analysis,an important cause of the high formwork collapse is unreasonable template support system of stress analysis,the defects in calculation model established.Based on summarizing the research status at home and abroad,the main problem of the engineering practice of the instability,insecurity and the defects in the template support model,and the unreasonable analyses on stress were studied in this paper.I hope this article can provide the reference for the design of fastener-style steel tube high formwork support system.The formwork design includes the construction process,construction method,installation and disassembly method and requirement of formwork and support system,precautions in concrete pouring,deformation monitoring of formwork and support system,checking and acceptance of formwork and support,stress analysis of formwork and support system,stability checking of stand pole,bearing capacity checking of foundation and indispensable construction techniques.Technical measures,such as the main template and its support system stress analysis and checking process.After analysis and study,the following conclusions are drawn:the maximum cantilever of the roof beam of this project is 7.350m,and the height of the formwork bracket reaches about 40m,which belongs to the super-heavy formwork support.The formwork support scheme must be checked according to the force analysis of the high formwork and perfected after expert demonstration.In the implementation process,attention should be paid to the importance of the scheme submission,so that the workers can deeply understand the main contents of the design scheme and be strict.According to the scheme,the concrete can be poured only after the experience is qualified;the deformation monitoring of formwork support is indispensable during the concrete pouring and subsequent maintenance process,and the frequency of deformation detection meets the requirements of the scheme to ensure the safety of the construction process;the checking calculation of the lateral pressure on the side formwork is indispensable.According to the two formulas of the lateral pressure calculation in the Construction Manual,the deformation monitoring of formwork support is indispensable.The formwork under lateral pressure is checked by force analysis,otherwise the force analysis is incomplete and it is easy to cause the formwork swelling phenomenon under the action of dynamic load during construction;the formwork panel is generally analyzed according to the three-span continuous beam under uniform load,and the distance between supports is the distance between the outer corrugated wood.The flexural strength,shear strength and deformation of the formwork are checked separately to ensure the strength and deformation of the formwork panel.Stiffness meets the requirements;the first supporting corrugated timber of formwork is generally analyzed according to three-span continuous beam under uniform load.The distance between the supports is the distance between the outside or the bottom and the vertical steel pipe.The first supporting corrugated timber mainly bears the uniform load from the panel,and checks bending strength,shear strength and deformation in turn to ensure that the strength and stiffness of the supporting corrugated timber meet the requirements.According to the analysis of three-span continuous beam under concentrated load,the distance between supports is the distance between pull bolts or vertical steel pipe poles.The second supporting corrugated wood mainly bears the concentrated load from inside or above corrugated wood which is perpendicular to each other.It requires checking calculation of bending strength,shear strength and deformation of corrugated wood or steel pipe to ensure the main corrugated wood.Or the strength and stiffness of steel pipe meet the requirements;the tension bolt will bear the axial tension to ensure that the tensile strength of the tie rod meets the requirements;the vertical steel pipe mainly bears the axial pressure,so the stability analysis of the component must be carried out.It mainly bears the load from the longitudinal horizontal steel pipe at the bottom of the beam and the weight of the steel pipe.The stability coefficient is obtained by looking up the table of the slenderness ratio of the vertical bar,and the calculated length is according to the table.According to the criterion,a larger value of the calculated length is obtained in the light of safety considerations,so as to ensure that the stability meets the requirements.The anti-sliding capacity of fasteners and the bearing capacity of foundation should also be analyzed and checked.In order to ensure the safety and orderliness of the construction process,it is necessary to ensure that the steel pipe fasteners do not slip,the bearing capacity of the foundation meets the requirements and the uneven settlement does not occur.Through the above analysis and calculation,the strength,stiffness and stability of the plate formwork and between them are ensured to meet the requirements.When the high and large formwork foundation is on different foundations,the compactness control of backfill soil is strengthened by thickening the thickness of formwork support foundation(300 mm),so as to ensure that the settlement of formwork support on backfill soil is reduced to a minimum,close to the settlement of formwork support on basement roof,and the sweeping dry and horizontal support here are doubled to adjust the uneven settlement.To ensure the stability of foundation settlement,the upper frame is erected.It is suggested that for cantilever structures over a certain scale,the construction unit should communicate with the design as far as possible,and adopt steel structure as far as possible.Steel structure can be assembled on the ground and lifted as a whole,which is both safe and economical.In order to erect super high formwork support,the pouring of vertical structure should be completed first,so that the frame body has horizontal tie joints to resist lateral displacement,so as to ensure that nothing is lost.In the process of construction,the project is constructed strictly according to the special design scheme,and the implementation process is safe and orderly.The project has been successfully completed without any safety accidents.Practice has proved the superiority of the design scheme and the rationality of calculation.Based on the analysis model of high and large formwork support system,the influence of structural measures such as horizontal bar step,vertical bar spacing,sweeping pole height,vertical pole extension sweeping pole length and scissors brace on the stability bearing capacity of high and large formwork support system is quantitatively analyzed,and the relevant structural measures in the code"Technical Code for Safety of Steel Tube Scaffold with Fasteners in Construction"(JGJ130-2011)and other codes are also standardized.The application is analyzed and calibrated.Finally,based on the quantitative analysis results,reasonable suggestions for various structural measures are given.It is precisely because of the correct stress analysis and structural measures.The successful completion of the construction of high formwork support provides relevant data and experience for colleagues to solve the problem of such high formwork support.During the erection of the high formwork support,it attracted many visitors and learners from the construction industry in Bozhou City,and achieved good social benefits.