Axial and Shear Behavior of Glass FiberReinforced Gypsum Wall Panels: TestsYu-Fei Wu1 and Mike P. Dare2

JOURNAL OF COMPOSITES FOR CONSTRUCTION – ASCE NOVEMBER-DECEMBER 2004

What Is GFRG ?• GFRGS are Gypsum Fiber Reinforced Glass • It is made up of gypsum a waste product of fertilizer industries

as like fly ash.• These are lightweight, hollow-core panels are machine made

using formulated gypsum plaster (Gypcrete) reinforced with chopped glass fiber

• The size of these panels – 120mm thick and of 1.02X3.05 m (or 2.85 m).

• These panels are reinforced with glass fibers about 300–350 mm long are randomly distributed inside the panel skins and the ribs in the manufacturing process.

• These panels have cavities as shown there about 8 cavities in 2.02 m wide panel

• The construction panels are cut/tailored into the specific design of each wall, including windows and doors, in a factory

Property name Value NoteCompressive strength 160 kN/m unfilled single leaf glass

fiber reinforced gypsum panel

Tensile strength 35kN/m Elastic modulus 3000-6000 MPa Unit weight 40kg/m2 Thermal expansion Coefficient

123 10−6mm/mm/ °C

Water absorption 5% By weight after 24 h of immersion

Thermal resistance

0.36 m2 K/W1.63 m2 K/W

Unfilled panelWith 35 kg/m3 and R2.5 Rockwool bats infill and

standardSound transmission Coefficient

28 Unfilled panel

45 Concrete filled panel

Fire resistance level 3 h For structural adequacy

DESIGN OF GLASS FIBER REINFORCED GYPSUM WALLSYSTEM

The design steps involves • Determination of Axial load capacity through concentric and eccentric axial tests•Shear Strength under monotonic and cyclic shear loa test

CONCENTRIC AND ECCENTRIC AXIAL LOAD TEST

Procedure • The walls were tested in an Amsler compression

machine with a maximum capacity of 5,000 kN• Stiff steel spreader beams were made and used to

spread the load uniformly from the compression machine to the ends of the test specimens

• The eccentricity (ECC) of the axial load was applied to the wall by placing the roller bars away from the centerline of the specimen, as shown in Fig.

• The compression load was applied to the specimen by the upward movement of the bottom platen and the tests were conducted under displacement control

• Five LVDTs were used to measure the axial displacements, out-of-plane displacement, and lateral expansion in the wall plane

• Two types of support conditions were tested. The first support condition was pinned support at both ends of a wall, as shown in the test setup of Fig

• The second support condition was one fixed end and one pinned end. For one fixed end and one pinned end supports, the top roller pin and the bearing steel plate shown in Fig, were removed to provide a “fixed” support

• Three types of specimens of height 2.85m were tested

• Type A-Filled with 25 MPa concrete with one end fixed and other end pinned

• Type B -Filled with 25 MPa concrete both with and without reinforcement both ends are pinned

• Unfilled wall – Type C

MONOTONIC AND CYCLIC SHEAR LOAD:

The unique features of this setup were noted •First, the specimen was tested horizontally (about 1 m above ground) instead of standing vertically. •Second, the top and bottom steel beams were able to clamp the edges of the panel and transfer the shear load uniformly into the panel without crushing the gypsum plaster, as shown in Fig•Third, the axial load could be adjusted and the axial load effect on the shear strength could be measured•Fourth, it was relatively simple and inexpensive compared to other shear tests setups. This simple test setup proved to be a very successful design.

• Panels with two different widths were tested for both unfilled and concrete filled panels; i.e., 1.52 m wide with six cavities and 2.02 m wide with eight cavities.

• Filled concrete strength is 25 MPa• For the 1.5 m panels, two different designs of

longitudinal with reinforcements• lateral load at the top measured by Load Cell 1;

horizontal displacements by LVDTs 1, 2, and 3,as shown in Fig

• Movements of the test rigs were monitored by Dial Gauges 1, 2, 3, and 4; and strain gauges at Side Supports 1 and 2 .

• The three LVDTs were used to measure the lateral deformation of the specimens

• The strain gauges on the side supports were used to measure the longitudinal strains that were calibrated to give

• Axial Forces F1 and F2 in these two side supports. The summation of F1 and F2 gave the axial load applied on the test specimens

• The two side supports ensured that the test specimens deformed and failed in a shear mode instead of in a flexural mode.

• Testing was conducted under displacement control of the hydraulic jack,

• Simply pushing (monotonic tests) or pushing and pulling (cyclic tests) the specimens at the top and measuring all of the responses.

• Type a specimen=1.52 m wide unfilled panel without initial axial load.• Type b specimen=1.52 m wide unfilled panel with 30 kN/m initial axial load. • Type c specimen=1.52 m wide unfilled panel with 60 kN/m initial axial load. • Type d specimen=2.02 m wide unfilled panel without initial axial load. • Type e specimen=2.02 m wide unfilled panel with 60 kN/m initial axial load.• Type f specimen=2.02 m wide unfilled panel with 30 kN/m initial axial load. • Type g specimen=1.5 m wide RC filled (full-length bars) without initial axial

load. • Type h specimen=1.5 m wide RC filled (full-length bars) with 95 kN initial

axial load. • Type i specimen=1.5 m wide RC filled (starter bars) without initial axial load. • Type j specimen=2.02 m wide RC filled (starter bars) without initial axial load

• The shear capacity calculated from the peak lateral load of the response charts gave a conservative shear strength of the unfilled panels

• The three 1.5 m concrete filled panels with starter bars failed by tensile breaking of the GFRG panels

• For all of the other concrete filled panels, extensive 45° shear cracking developed before the peak load was achieved.

• Specimens reached the peak load when visible and substantial longitudinal shear cracks developed in the panel

• Accompanied by the clear sound of plaster tearing off at the longitudinal cracks.

• The lateral load (shear strength) dropped quickly when the longitudinal cracks developed

Discussion of Test Results• All unfilled panels failed due to plaster crushing, irrespective of the

load eccentricity. • The maximum tested eccentricity was the design eccentricity for

residential house construction in accordance with AS 3600 2001• The concrete filled specimens all failed due to buckling and flexural

tensile breaking of the GFRG walls.• The Euler buckling load for the wall with an effective length of 3 m

and without eccentricity is calculated to be approximately 2,000 kN.

• Compared to the test results of approximately 1,300 kN, the difference apparently resulted from the imperfect test conditions—especially the inaccurate eccentricity that was difficult to control in the tests.

Shear test • The typical shear failure mode for the concrete filled

GFRG walls was the longitudinal shear failure in the gypsum plaster panel between two adjacent concrete cores (infill).

• Substantial slips or relative movements between the concrete cores and the plaster panel had occurred in the tests

• There were visible 45° shear cracks, developed before the peak load was reached and shear strength varies from 19.1 kN/m to 24.5 kN/m.

Conclusion • The in-plane shear and flexural strengths of GFRG walls are

significantly lower than those of a same size RC wall• Therefore, significant wall length is needed to share the lateral

loads.• As a result, GFRG walls are more suitable for residential

construction• The axial and shear capacities of GFRG walls as a walling

member have been obtained from the tests. The test results illustrated that

1.The compressive strength of 3 m high unfilled walls was governed by the plaster strength.

• The compression strength of a 3 m high concrete filled wall was governed by out-of-plane buckling

• the infill concrete strength and reinforcement inside the cores had no effect on the compression strength of the walls

• The axial capacity was only affected by the axial load eccentricity and support conditions.

• The shear test setup ensured a shear failure for panels but also effectively established the relation between the axial load and additional shear strength due to the axial load.

• The additional shear strength due to the axial load was found to be about 0.2N.