Study On Safety Technology And Management Of Bracket Girder And Cut Column Reformation For A Steel Factory Building

According to estimation, there is about40billion square meters existing buildings inChina, and the industrial building area is about10billion square meters. A large number ofindustrial buildings of1950’s and1960’s, which withstood long-term bad environmentsuch as high temperature, high humidity, corrosive gases, dust and heavy load, had seriousstructural damage and have been into elderly stage. With the rapid development of scienceand technology, industrial production is moving into a mechanization and modern era,besides, the adaptable reformation technology has become increasingly actively. Bracketgirder and cut column (BGCC), as an effective way to expand the column space, has beenwidely used, however, complex environmental conditions resulted in uneven quality andhigh-risk.There is a lot of construction technique and research about BGCC for steel structuralindustrial buildings; however, there are many problems which have been unresolved, suchas support-system design, primary structure deformation control and the whole workperformance of composite construction, etc. In order to make the design and constructiontechnology of BGCC normal and standard, and reduce the reformation safety risk, thesystematic theory and applied research of BGCC for steel structural industrial buildingswas promoted.In the thesis, modern safety management theory, system engineering principle, workbreakdown structure(WBS), project in-situ monitoring and fault tree analysis (FTA)method were applied to establish standard design process and construction technology ofBGCC for steel structural industrial buildings. In order to improve the construction qualityof BGCC and control the safety risk, the whole process of safety evaluation system andsafety risk control measures were provided.The main contents of the thesis are as follows:(1) Design principles and methods of BGCCReferring to the national standards, norms, and through expert interview, the generaldesign principles of underpinning design for existing buildings and anti-collapse designprinciples of BGCC were summarized.The thesis emphatically introduced the structureconstruction design principles, and expounded the design principles of limit state, stiffnesscontrol and structural arrangement for the key components-the bracket girder (or bracket).Finally, the general process of transformation design for steel structural industrialbuildings was proposed.(2) Construction technology and key construction technique of BGCC Through expert interview, according to the comparison of advantages anddisadvantages of the current three common methods of BGCC-non-complete bracketjacking construction method, complete bracket jacking construction method and completebracket without jacking construction method, complete bracket without jackingconstruction method was recommended in the thesis. By the use of work breakdownstructure (WBS) and the flow chart method, the general construction processes wereidentified. Finally, the key construction technology, which contained reinforcementtechnology of the foundation and steel columns, production technology of brackets in situ,and technology of cutting column with uninstallation, was described detailedly.(3) Comparison of project in-situ monitoring and theoretical resultThe checking calculation result of seismic performance and bearing capacity of thecritical components between the original steel structural industrial building and the BGCCreform industrial building, which was used by SAP2000finite element software, showedthat the bearing capacity and the stiffness met standard, and the design principles andconstruction methods were feasible. It was found that the internal forces changes law ofthe bracket and the column during cut-off column and uninstalling process after the in-situmonitoring of BGCC project after the analysis of stress and deflection of the keycomponents during underpinning. By analyzing the main reasons why the results betweentheory and test different, it was found that the temperature of the cutting part of columnincreased was due to the oxygen-acetylene flame. Therefore, it was confirmed that thecomplete bracket without jacking construction method was scientific.(4) Safety risk management of BGCCAfter identifing the potential major accident types during the construction ofBGCC-fall, object hitting, collapse, equipment damage and electric shock, the major riskfactors of accidents were decomposed. Then through fault tree analysis (FTA) method, theimportance coefficient of the accident event was found. Accordingly, safety evaluationsystem for BGCC of steel structural industrial buildings was established and the safetyrisk control measures were proposed.