Concrete Formwork Svstems - Part 8

Vertical Formwork Systems: Crane-Independent Systems - 8,1 Slipforms 8,2 Hệ thống Cốp pha tự Nâng cao Như đã đề cập trong Chương 5, ván khuôn thẳng đứng có thể được phân thành hai loại chính, cụ thể là, hệ thống cần cẩu phụ thuộc và các hệ thống độc lập cần cẩu. Slipform và ván khuôn tự nâng cao được phân loại là hệ thống cần cẩu độc lập trong đó các tấm ván khuôn di chuyển theo chiều dọc bởi các cơ chế vận chuyển theo chiều dọc khác | 8 Vertical Formwork Systems Crane-Independent Systems Slipforms Self-Raising Formwork System Copyright Marcel Dekker Inc. All rights reserved. As mentioned in Chapter 5 vertical formwork can be classified into two main categories namely crane dependent systems and crane-independent systems. Slipform and self-raising formwork are classified as crane-independent systems in which formwork panels are moved vertically by other vertical transportation mechanisms. SLIPFORMS History The history of slipforming can be traced back to the 1920s and before. In the late 1920s a number of concrete structures were cast using a system of formwork that was moving during the placing of concrete. At that time forms were being raised by hand-screw jacks and job-built wooden yokes. Laborers would pull ropes that would raise the forms. Early application of slipform was limited to storage bins and silos with a constant thickness all over the wall height. Since the late 1950s slipform construction has come a long way locomotion is accomplished by jacks climbing on smooth steel rods or pipes anchored at the base of the structure and the system has been employed successfully and economically in situations which have required discontinuity of section. As a result the list of recent application expanded to include towers cores bridge piers power plant cooling chimney shafts pylons and the legs of oil rig platforms. Copyright Marcel Dekker Inc. All rights reserved. Construction Practices Most contractors using slipforming do not own their own slipforming equipment. A general contractor who finds it feasible to use slipforming has three options 1. To design build and operate the slipform complex. This requires the assistance of expert consultants who will help at every step of the project. 2. To subcontract the work to a subcontractor who specializes in slipform. 3. To buy or rent the forming system completely designed and fabricated ready to be erected at the site to be