Contd. from Part-II …..
Highly skilled supervision is necessary for slipform construction of highrise building cores or any other tall structure for that matter. The slipform unit is carefully designed and once accepted, no change should be made in it during construction unless well-examined and approved by the designer. If a crane too is tied to the structure for various purposes such as lifting of steel reinforcement, inserts, frames etc., then the impact of the same on the structure is also considered in the design of the core. Steel re-bars are usually handled by guides which are attached to the slipform unit itself. Sometimes, ordinary hoists are also deployed in stead of a crane for lifting rebars, inserts etc. from the ground, especially for mid-rises.
Similarly, adequate provision for smooth movements of workers from ground to the slipform structure and vice versa must be in place. The slipform structure itself should have sufficient working space for these movements as well as for working with long re-bars.
Slipform construction, by it’s nature, is most convenient for continuous walls with virtually no or minimum joints or projections. However, that is not the case in a building whether it is a concrete-framed or a steel-framed one. Good number of connections such as, connections for slabs, beams etc. are bound to be there which need to be meticulously addressed to right from the beginning stage. Proper pre-planning and adequate care during execution are of utmost importance, especially in the case of pull-out bars for in concrete-framed buildings or steel inserts in steel-framed ones.
As discussed in an earlier post, verticality of any tall structure including building is of extreme importance as any negligence on that could result in development of eccentricities in the structure which is utterly unwanted. Tolerance limit for verticality must be well stipulated for any highrise. Usually, the same for lift shafts are stipulated by the lift manufacturing or installing agencies themselves. Effective mechanism for monitoring verticality of the structure right from the beginning must be in place in order to avoid deviations at any stage of construction. Verticality at no point of time during the entire construction period should go beyond the prescribed tolerance limit.
An efficient communication system, good co-ordination, high safety standards are some other basic requirements of successful implementation of slipform construction of high-rise Buildings.