GFRG – Glass Fibre Reinforced Gypsum Panel Building Construction
Glass Fibre Reinforced Gypsum panel is a new trend in rapid building construction technology. GFRG panels are manufactured from high-quality gypsum plaster (beta plaster), reinforced with glass fiber rovings and special additives. This product was originally developed and used since 1990 in Australia by Rapid wall Building Systems.
Presently, these panels are manufactured in a few Asian countries like India, China, Saudi Arabia and Oman. In Australia, several buildings had been built using the Rapid wall technology, but the use of the panels was restricted to walls, resisting gravity loads. The floors were made of conventional reinforced concrete slabs.
Since 2003, the IITM research team has been engaged in extensive research on extending the use of these panels as structural members for all components of the building, including floor slabs and staircases, thereby it reduces the consumption of Reinforced Concrete (RC) significantly. Furthermore, a detailed and accurate design of the GFRG panel entire for the building has been developed including earthquake and wind-resistant design.
GFRG panels are qualified for carbon credits by the World Bank under the Kyoto protocol and certified as green building material by The United Nations Framework on Climate Change (UNFCC).
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GFRG PANELS: DIMENSIONS AND MECHANICAL PROPERTIES
GFRG panel is available in the standard size of 12.0 m length, 3.0 m height and 124 mm thick, with modular cavities. These cellular cavities are formed between outer skins (flanges), 15 mm thick and interconnecting ribs, 20 mm thick, at 250 mm spacing. Each of the GFRG panels has cavities of size 230 mm length and 94 mm wide. The below table shows the mechanical properties both empty panels and panels filled with M20 concrete in all cavities.
|Sr. No||Mechanical Property||Characteristic Value|
|1||Unit weight||0.43 kN/m2|
|2||Uni-axial compressive strength||160 kN/m (empty panel) 1310 kN/m (filled panel)|
|3||Ultimate shear||strength 21.6 kN/m (empty panel) 61.0 kN/m (filled panel)|
|4||Water absorption||1% in 1 hour, 3.85% in 24 hours*|
|5||Fire resistance||2.30 hour rating (empty panel) 4.0 hour rating (filled panel) – withstood 900-1000°C|
|6||Coefficient of thermal expansion||12 x 10-6 mm/mm/°C|
GFRG PANEL – APPLICATIONS AND ADVANTAGES:
GFRG panel has the following applications:
a) To resist gravity load in the building they are used as load-bearing walls in buildings,
b) GFRG panel used infill walls or partition walls in multi-storeyed framed RC structures.
c) Used for compound walls ensuring minimum used of concrete.
d) As shear walls, to resist both gravity load and lateral load from earthquakes and wind; also as walls of lift-well and parapet walls;
e) GFRG panels used in pitched roof slabs, floor slabs/roof slabs and also as staircase waist slabs and mid-landing slabs;
GFRG panel system construction has following benefits over conventional systems:
i) High speed of construction;
ii) More carpet area for the same built-up area: the thickness of wall panels is the only 124mm;
iii) Less embodied the energy and carbon footprint, a significant reduction in the use of steel, cement, sand, and water; recycling of industrial waste gypsum;
iv) Less cost of construction: savings in materials; no cement plastering;
v) Less building weight (panels weigh only 44 kg/m2), thereby reduction in design for seismic forces and savings in the foundation, especially in multi-storeyed buildings;
vi) 8 to 10 storeyed buildings can be designed using GFRG panels, without the need of conventional RC beams and columns;
vii) GFRG panel gives smooth finish: use of factory-made panels for all the walls, floors and staircases;
viii) Less CO2 emission compared to other conventional building materials.
ix) GFRG panel made building gives better thermal comfort inside compared to conventional buildings.
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DESIGN AND CONSTRUCTION OF GFRG BUILDINGS:
GFRG panel system building designed as a load-bearing system. Therefore, all walls are constructed from the foundation or plinth beam till the terrace. Most suitability the same floor plan has to be replicated for all floors in multi-story buildings. Buildings can be designed up to ten stories in low seismic zones, using GFRG panels (and to lesser height in high seismic zones), without conventional columns and beams. In this building system, the foundation is conventional, while the entire structural elements in the superstructure are constructed using GFRG panels.
Limit states design procedures are used for the design of GFRG buildings, considering the ultimate limit state for strength design, as well as serviceability requirements. Most importantly while designing the GFRG panel system the factor of safety for reinforcing steel and the GFRG panel (with and without concrete infill) is taken as γs = 1.15 and γm = 1.50 respectively, as recommended in IS 456: 2000.
Earthquake resistant design is carried out in compliance with the requirements of international codes (in India IS 1893 (Part 1): 2002), where the response reduction factor (R) is taken as 3.0 for seismic load calculations.
The GFG building construction is not the same as a conventional system. It requires a special type of equipment, tools, and tackles such as appropriate crane for loading, unloading and erecting the panels, lifting jaws and spreader bars for lifting the panels and reset the prop later for supporting wall panels after erection. The design and construction of important structural elements are summarized in the following sections.
DESIGN AND CONSTRUCTION OF FOUNDATION
The conventional type of foundations is used in GFRG building constructions. The foundation is designed base on the safe bearing capacity of soil and soil profile at the particular site and the number of storeys of the structure.
Generally, strip footing is used, as the superstructure consists of load-bearing walls. For low rise GFRG building, Simple masonry spread footings is sufficient with a network of reinforced concrete (RC) plinth beams on top, above which the GFRG wall panels can be placed. ‘Starter bars’ have to be inserted in the plinth beams, at the locations (Fig.3), where the cavities of the panel are to be filled with RC, with appropriate lap length in accordance with national codes. This ensures the connection of the superstructure with the foundation, spread over the entire wall length over the network of plinth beams. If the foundation is deep, properly designed reinforced concrete pedestals can be used to support RC plinth beams, with small isolated footings. High rise GFRG panel System building, RCC wall may be provided to support the plinth beams, with appropriate strip or raft footing below.
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A system of reinforcing plinth has to be constructed as per the structural design drawings and the top has to be at a perfectly horizontal level. A DPC layer on the RC plinth beam is mandatory in order to avoid the possible absorption of water by glass fibers in the GFRG panels through capillary suction.
DESIGN AND CONSTRUCTION OF GFRG WALL:
The GFRG walls are designed to resist axial force (P) from gravity loads, lateral in-plane shear force (V) and in-plane bending moment (M) from wind and seismic loads. The in-plane bending capacity of the walls depends on its length, the reinforcement provided, as well as the level of axial load and lateral shear. The values of Mud and in-plane shear strength increase with the length of the wall.
Experimental research and study indicate that when GFRG panels subjected to lateral loading have shown that failure is initiated by vertical cracking caused by the shear failure of the GFRG. Longer shear walls tend to attract larger lateral loads and will form vertical shear cracks in the middle region, causing a further redistribution of forces, and possible further vertical shear cracking.
Design interaction curves are developed for various lengths of GFRG panels (from1.0m to 3.5m wide Based on the structural requirements and the design interaction curves, the interval of concrete infilling and size of reinforcement to be provided in walls are decided. The cavities in the GFRG wall panels shall be filled, wherever structurally required, with concrete of grade not less than M20, using an aggregate of size less than 12mm.
For up to 3 storeyed high low rise GFRG building there is no need structural requirement to infill all cavities with reinforced concrete, although it is desirable to fill all cavities with PPC or Cement quarry dust, in view of public perception of safety against intrusion, and also facilitate nailing, drilling, fastening of non-structural components etc.
Reinforcing bars may be provided where required, but in no case, more than three adjoining cavities shall remain unreinforced. Single bar reinforcement of suitable diameter (not less than 8mm), may be used in such low-rise buildings.
The GFRG panel building can be constructed fast using the crane. It is advisable to erect panel without removing door/ window cut pieces from the panel. This will keep the panel in balance and help to locate the center of gravity of the wall panel. Once the panel is brought in position, the plumb and level are to be checked. These props can be removed once the panels are in-filled with concrete and gain sufficient lateral stability.
The slump of concrete shall be 70mm + /- 20mm and the water-cement ratio shall be 0.50 to 0.55 to the infill of cavities of the wall panel. The first pour of concrete is to be of a maximum 300 mm high from the base of cavities. After 2 hrs for allowing an initial set of 1st pour of concrete, 2nd pour of concrete up to window sill level shall be done.
Simultaneously, the cavities which are not structurally required to be in-filled with concrete shall be in-filled with lean concrete or quarry dust mixed with cement (dry) in stages. All the electrical conduits and plumbing lines can be laid through cavities now. It is mandatory to provide RC embedded lintels over openings for doors and windows, exceeding 1.2 m in width. 3rd pour of concrete shall be done up to window/ door top (2.1m high) and 4th pour up to the bottom of a horizontal tie beam. This tie beam shall be done on top of walls, all around just below roof slabs.
GFRG panel can be utilized for the construction of staircase waist slabs. All the top flanges of panels shall be cut open and the reinforcement cage is to be inserted. This can be concreted after providing appropriate support. The steps can be constructed with either concrete or bricks.
GFRG BUILDINGS IN ASIAN COUNTRIES:
To demonstrate GFRG technology 2 storied GFRG building is constructed in IIT madras, India. The total built-up area of this building is 1981 sq.ft, shown in Fig. This model house apartment houses four flats (two for the Economically Weaker Section of carpet area of 269 sqft each and two for the Lower Income Group of carpet area of 497 sqft each), which can be replicated for mass housing, horizontally and vertically. The entire building was completed in 30 days.
The use of prefabricated lightweight GFRG panels for the entire building system facilitated a substantial reduction in building self-weight, construction time and workforce requirement. So far, more than 300 buildings are constructed in India, most of them are individual residential buildings. These panels can be used not only for residential buildings but also for industrial and institutional buildings. This building system gains popularity in a few Asian counties also like in Oman, China, Saudi Arabia, etc. Buildings from a few Asian countries are shown in Fig.
GFRG Panel Cost:
When the GFRG panel introduced in India, Its cost is around Rs. 999 per Sq.m. in 2018. With the addition of GST of 12 %, its price is 1120.
These panels are manufactured in FRBL factory Cochin, Kerala.
GFRG panels can be effectively used for the entire superstructure of buildings, including all walls, slabs, staircases, parapets, etc. This building system has many advantages over the conventional building. GFRG building has significant potential to providing rapid affordable mass housing. This is an eco-friendly and sustainable building system, making use of recycled industrial waste gypsum or natural gypsum and minimizing the use of cement, steel, sand, water and labor input. This technology is now gaining acceptance in India and other Asian countries.
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