Research On Design Methods And Construction Techniques For The Outer Jacketing Structure Reconstruction Project Of Harbin Nangang Hall

With the transition of construction industry from"mainly constructing newbuilding"to"constructing new building on a par with reconstructing old building"inour country, the reconstruction technique using outer-jacketing structure to add storiesaround the existing building has become one of issues highly concerned in the circlesof civil engineering. Based on the practice from the typical project of HarbinNangang Hall, it is of practical significance to enrich and perfect the design theoryand construction technique of reconstruction and extension project around theexisting building.Combined with the characteristics of reconstruction project of Harbin NangangHall and the requirements of the owner, after iterative discussing, the adding schemeof mega frame including the main frame and sub frame around old building is applied.At the same time, the calculation models for construction stage and service stage aregiven. The vertical loads are transmitted from the sub frame to the main frame bydavit. The main frame is formed by angle-steel concrete columns and prestressedconcrete beams with encased H-steel. The sub frame is formed by encased steelcolumns and encased steel beams hanging over the mega frame. The outer-jacketingstructure is constructed in accordance with the following sequence: the first is steelstructure project, after the angle steel skeleton is fixed into steel column, the H-steelbeam of the top story is lift, then the davit is assembled, at last, the rest parts of thesteel frame are assembled, which become the load-bearing structure whenconstructing the concrete structure; the second is concrete structure project, the first,cast concrete of the columns and beams of the main frame, then tension theprestressed tendons in the beams of the main frame, finally, cast concrete of the subframe.In order to ensure the original building work as usual and avoid transferringconstruction load to the roof of the original building during conctruction, the designidea of"self-supporting concrete structure cast in situ during construction"is adopted.The idea is: H-steel is used in the main beam, from which the bottom form for castingthe beam can be suspended, and then the side form can be fixed on the bottom form.In this way, the H-steel can carry the main beam's own weight and construction loadduring concrete being cast. The prestressed concrete beam with encased H-steel andthe column of the main frame are connected to be a united one by the fast joint duringservice. Moreover, as an outer-jacketing frame, they can bear the new added load. Static analysis for phase of construction is applied to the project by Sap2000procedure, from which the internal forces of critical sections during the variousphases in the structure are got, on which the steel members and composite membersbased are designed. The construction measures are given as well as the constructionsequence, the method of tensioning the prestressed tendons and the constructiondetails of beam-column joints.Seven structural schemes including the selected one in the tentative design arepresented. In the finality of this article, comparisons between the selected programsand other alternative methods are given, and then the advantages and disadvantagesof various options are pointed out.The reconstruction project of Harbin Nangang Hall introduced in this paper hascome into construction. The design concept, detail of construction and innovatetechnique are certain to provide valuable reference for design and construction of thesimilar projects.