Analysis And Control Of Time-dependent Behaviour Of High-rise And Large Span Structures In Construction

As two most popular types of large complex buildings, super high-rise buildingsand prestressed large-span steel structures have been developing rapidly in China,thanks to the fast growing economy. However, some new problems have beenencountered in construction of such structures. These include accumulation ofvertical deformation of high-rise buildings in construction, optimum scheduling ofinstallation of the outrigger-brace, pretensioning control of form of elliptical cable-suspended dome and control of cable node slippage, to name but a few. Theseproblems are all crucial issues for construction of large complex structures. If notproperly addressed, they can affect the precision and even safety of construction,especially with increasing scale and growing complexity of the structures nowadays.For healthy and smooth development of the large complex buildings, it is thusnecessary to conduct thorough investigation of the time-dependent behaviour of largecomplex buildings, and to develop proper construction scheme and control method,via both analysis and experiments.This study mainly covers the following work:1. Method for time-dependent analysis of constructionFor high-rise buildings, the CEP-FIB90prediction model for shrinkage andcreep of concrete and the age-adjusted effective modulus method were used tosimulate deformation of buildings during construction. An analytical method forsimulation of constructions process of high-rise buildings was developed, inconjuncture with techniques such as element activation and suppression, stepwiseloading and stepwise restrictions. For prestressed large span structures, theSteffensen method was adopted to develop a modified version of pre-tensioncompensation method, which improved the efficiency and convergence in stress-finding analysis. At the same time, a technique for simulating cable node sliding wasdeveloped based on the idea of friction-force distribution, which accounts for theeffect of friction. The technique was used successfully to simulate the time-dependent geometry and stiffness caused by cable node sliding, hence theimprovement in analysis of construction of prestressed large span structures.2. Analysis and control of vertical deformation of super high-rise buildingsduring construction Taking a typical super high-rise building over400meters high as example, theaccumulation of vertical deformation during construction was investigated with theanalytical method developed. The effect of leveling, shrinkage and creep of concreteand the storeys of the core tube constructed ahead of the steel frame was investigatedand the characteristics of the vertical deformation revealed. Furthermore, a method ofpre-deformation for super high-rise building was presented with deformationcompensation stepwise. Finally a construction monitoring system for super high-risebuilding was developed and applied to monitoring construction of the typical high-rise building, and on-site data collecting was implemented, which could verifies thecorrectness and precision of the analysis or simulation.3. Optimum scheduling and installation of the outrigger-brace in super high-risebuildingsAnalysis of optimum scheduling of outrigger-brace installation was conducted,in which the effect of two types of outrigger-brace on the lateral stiffness of superhigh-rise buildings was investigated. The additional stresses which develop in theoutrigger-braces due to relative deformation between the outer steel frame and innerconcrete core walls were analyzed. A couple of construction schemes were includedin the analysis. Curves of maximum additional stress against connection time of theoutrigger-brace were finally obtained. The curves have enabled the optimumscheduling of outrigger-brace installation. Finally, monitoring of construction wasimplemented, and the simulated results correlate well with the monitoring results,presenting the proof of the feasibility and the validity of this method.4. Analysis and control of prestressing of construction of cable-suspendedelliptical domesExisting methods for prestressing in construction of cable-suspended ellipticaldomes were reviewed, a new method was proposed, which stretches the radial cablesaccording to the principle of uniformity, alternative prestressing and symmetry. Thenumber of prestressing equipment and cost of construction can significantly bereduced using the proposed method. Analysis of the whole construction process of alarge cable-suspended elliptical dome was then conducted and suggestions regardingthe prestressing equipment choosing and proper timing for removal of the temporarybraces were given. The suggestions were adopted in the successful construction ofthe Dalian Stadium. Three practical measures for preventing cable nodes sliding werefurther proposed, based on the analysis of cable node sliding in construction of cable-suspended elliptical domes. Such measures were also proved effective in construction of the Dalian Stadium. Finally, a prestressing construction experiment was conductedon a model of cable-suspended elliptical dome with a plan size of14.5×11.6m. Twoconstruction schemes, prestressing of the diagonal cables and strut-lifting installation,respectively, were tested. The test results verify the accuracy of constructionsimulation and feasibility of the two proposed construction schemes.