What Is False Work?
Temporary structures are used in construction to support permanent structures. These temporary structures are maintained until the permanent constructions are strong enough to support themselves. Such a temporary structure is called falsework. Falsework is often called centered for arches.
Falsework is used in the construction of buildings, bridges, and elevated roadways. Also included in the falsework are the temporary support structures of the formwork used for the concrete mold.
The definition for falsework was formulated as per BS 5975: 2008. “The temporary structure used to support the permanent constitution is not self-supporting in the constitution itself.”
From ancient times the construction of bridges and viaducts has been carried out in the form of falsework. The Romans did the falsework by crossing the river in Turkey like the Limira Bridge.
False constructions were made from wood for different purposes till the 20th. There was a shortage of timber in different regions, and new techniques were developed to replace the timber used by the people on a daily basis.
Falsework involves supporting structural members such as bridge slab, foundation, building slab, legs, and permanent structure, etc.
Temporary structures are made for a permanent structure, plant, apparatus and man-made way, etc., which is called falsework.
Falsework is used to support formwork for in-situ concrete, prefabricated concrete elements or stone arches, bridge slabs, etc.
Improper operation is a temporary structure used to support concrete forms. Must be strong enough to achieve the purpose of the falsework. The components used in the wrong work must have sufficient strength. So that it should be able to withstand a load of forms, new concrete, and any construction equipment and workers, etc.
The improper operation should be able to maintain a sufficient height. An appropriate strong structure is erected using suitable jacks, base jack wedges, etc., used as part of the falsework.
Types of Falsework
- Shorbrace System
- Cup-Lock Supporting System
1. Shorbrace System
The shorbrace support system is widely used to support heavy structures such as bridge decks.
The shore-brace is arranged using the default size in the shore-brace frame. In which to get the distance of the frames, crosses of one size are connected to each other.
Shorbrace system support is widely used to provide safe support to the bridge deck. This system has various qualifications. The simplest and quickest way to eliminate false positives from this system. Also, it is used specifically to support heavy structures in a way. This system is made up of different parts.
The various parts of this system are as follows
- Shorbrace Frame
- Shorebrace Telescopic Frame
- Vertical Frame Connector
- U Head Jack
- Cross Bracing
These frames are the main part of the wrong operation. They are connected to each other to achieve the required height to support the formwork, as shown in the figure below.
Shorbrace Telescopic Frame
The function of this frame is to help maintain the required height. This frame is fixed inside the shorbrace frame. This frame is connected to the mainframe by a load pin.
Vertical Frame Connector
The function of this frame is to increase or decrease the height according to the requirement of falsework. This frame is connected to the mainframe by a loading pin. Bracing is used to support the vertical frame.
U Head Jack
The head jack or U-head is an adjustable component in this system. The use of a u-jack contributes to providing an accurate level for the casted slab.
The use of bracing serves to support two adjacent vertical members. The bracing crosses into the shorbrace system, as shown in the figure below. The figure shows the various components of a falsework operation.
2. Cup-Lock Supporting System
The cup-lock support system is widely used in high-rise projects like bridges and buildings. This system requires storage space. Compared to other auxiliary systems lift and disassembly of the cup lock system are easy and fast. The temporary structure is formed with the help of a cup lock system.
- Base jack
- U and Post Head Jack
- Spigot Connector
The height of the adjustable base jack in the cup lock system is 760 mm and 600 mm. While the use of a base jack provides a base for the system to stand on the ground.
U and Post Head Jack
While Universal Jack is available in the market in height of 760mm and 600mm. It is used to level the slab.
The spigot connector is used to connect two vertical members when the height of the structure is high.
The laser is used to connect the vertical member in a longitudinal direction. It is also used as a guard in high rise buildings. Ledgers are available in various lengths. Which are as follows
- Cuplock Ledger 2.5 Mtr
- Cuplock Ledger 1.8 Mtr
- Cuplock Ledger 1.6 Mtr
- Cuplock Ledger 1.3 Mtr
- Cuplock Ledger 1.2 Mtr
- Cuplock Ledger 1 Mtr
- Cuplock Ledger 0.9 Mtr
- Cuplock Ledger 0.6 Mtr.
Causes of Falsework Failures
Falsework fails due to overload, imperfections related to formwork and human error on the job, indifference, haste and lack of information, etc.
The following is a report by Hadiprio and Wang (1986) examining the causes of 85 major failures in the last 23 years.
|Sr No||Causes of Failure||Number Of Occurrences|
|(A)Triggering Cause Of Failure|
|1||Strong River Current Casing Flushwork Foundation Slippage||1|
|2||Improper operation due to heavy rains causes the foundation to slip||3|
|5||Failure of equipment for moving formwork of falsework||5|
|6||Effects of formwork component failure||4|
|7||Concentrated load due to improper prestressing operation||1|
|8||Other imposed loads||2|
|9||Concentrated load due to construction material||2|
|10||Impact loads from concrete debris and other effects during concreting||27|
|11||Impact load from construction equipment/vehicles||3|
|12||Effect of improper/premature falsework or formwork removal||6|
|13||Vibration from nearby equipment/vehicles or excavation work||5|
|14||Other causes or not available||20|
|(B) Enabling causes of failure|
|1||Inadequate falsework cross- bracing/lacing||17|
|2||Inadequate falsework component||14|
|3||Inadequate falsework connection||9|
|4||Inadequate falsework foundation||7|
|5||Inadequate falsework design||8|
|6||Insufficient number of shoring||4|
|8||Failure of movable falsework/formwork components||4|
|9||Improper installation/maintenance of construction equipment||2|
|10||Failure of permanent structure component||1|
|11||Inadequate soil foundation||4|
|12||Inadequate design/construction of a permanent structure||2|
|13||Other causes or not available||30|
|(C) Procedural causes of failure|
|1||Inadequate review of falsework design/construction||23|
|2||Lack of inspection of falsework/formwork during concreting||22|
|3||Improper concrete test prior to removing falsework /formwork||2|
|4||Employment of inexperienced/inadequately trained workmen||4|
|5||Inadequate communication between parties involved||1|
|6||Change of falsework design concept during construction||5|
|7||Other causes or not available||38|