Concrete Formwork Svstems - Part 7

Wall Form Design - 7,1 Các thành phần tường Mẫu 7,2 tải Thiết kế Phương pháp phân tích Nhấn mạnh tính toán 7,5 Xác định thiết kế cho phép tối đa 7,6 Span giằng Lateral Chương này trình bày một phương pháp thiết kế cho tất cả các gỗ hình thức tường bê tông. Thủ tục này đã được xây dựng để cung cấp cho một thiết kế hình thức bức tường an toàn cho tất cả các thành phần. Các phương pháp thiết kế dựa trên tải trọng khuyến cáo của ACI-347-1994 và nhấn mạnh giá trị khuyến. | 7 Wall Form Design Wall Form Components Design Loads Method of Analysis Stresses Calculations Determination of Maximum Allowable Span Design of Lateral Bracing Copyright Marcel Dekker Inc. All rights reserved. This chapter presents a design method for all-wood concrete wall forms. This procedure was formulated to provide for a safe wall form design for all components. The design methodology is based on loads recommended by ACI-347-1994 and stresses values recommended by NDS-1991 and APA 1997. WALL FORM COMPONENTS A wall form is usually made up of sheathing studs wales ties and bracing as shown in Figure . The fresh concrete places a lateral pressure on the sheathing which is supported by studs. Studs behave structurally as a continuous beam with many spans supported on wales. Wales in turn are assumed to act as a continuous beam that rests on ties. Ties finally transmit concrete lateral pressure to the ground. DESIGN LOADS The pressures exerted on wall forms during construction need to be carefully evaluated in the design of a formwork system. Loads imposed by fluid concrete in walls and columns are different from gravity loads produced on slab forms. Fresh concrete exhibits temporary fluid properties until the concrete stiffens sufficiently to support itself. Copyright Marcel Dekker Inc. All rights reserved. Lateral Pressure of Concrete Forms for Wall Formwork should be designed to resist the lateral pressure loads exerted by the newly placed concrete in the forms. If concrete is placed rapidly in wall or column forms the pressure can be equivalent to the full liquid head pressure. This requires that rate of placement exceed the initial set time of the concrete mix. Excessive deep vibration can liquefy the initial set of concrete within the effective coverage of the vibrations. Retarder additives or cool weather can also delay the initial set and result in higher than anticipated lateral pressure. The formula for wall .