10-10-2012, 05:37 PM
Erection or large span structures
ERECTION PPT.ppt (Size: 1.92 MB / Downloads: 91)
Introduction
Erection of component structures is a complex mechanized process of continuous assembly of buildings and installations from prefabricated elements and components like built roof of industrial buildings, bridge span structures etc…
The erection effectiveness is ease of erection with minimum consumption of labour, time and other means.
An erection work plan is part of construction project design for the whole building or installation being built.
The erection work plan includes:
description of erection work.
diagram illustrating erection procedures for various structures.
diagram for the pre-assembly of structures and installations of cranes.
schedules of erection work and movement of machines.
specifications of erection and auxiliary equipment.
estimates of labour requirements.
if necessary the project design may include additional process requirements.
Erection cycles and methods
An erection cycle is a method of operations for placing a component in its design process.
The operations requiring an erecting crane and therefore consumption of machine time are,
1.Slinging and lifting and delivering the component to a point of erection.
2.Guiding and positioning and placing it in design position.
3.Temporary fastening of component, unslinging and returning load-lifting hook to the initial position.
4. The time required for slinging, lifting, carrying to place of installation and unslinging varies negligilbly,as it is governed mainly by skill of labours and design of slinging devices.
Slinging of structures
Building structures, various parts, equipment units and other loads are slung by means of various devices, such as
Flexible slings- made of steel wire ropes, employed to lift light columns, beams, wall panel slabs, roof slabs etc..
Spreader beams-
Beam type- made of metal beams of two channel connected web to web. To ensure the uniform tensioning and transfer of load to all 4 points of attachment.
Latticed spreader bars- made of metal triangular welded trusses. To handle long-line structures.
Grabs-
Friction grips- handling lightweight columns.
Lever grips- handling heavy large wall slabs.
The vacuum lifters- to lift the hook of cranes