1. Introduction and research needTraditionally, bamboo has been limited for the use of building low-rise

structures located in tropical countries. In recent years, there has been a

massive increase in the use of bamboo products and the design of bamboo-

based, load-bearing systems..

Few studies have studied the structural fire performance of bamboo,

which is essential if fire safety considerations must be accounted for (e.g.

complex architectures, or mid-, high-rise construction).

The reduced mechanical properties and reduced cross-section methods both

form the basis of understanding the behaviour of bamboo under fire

conditions.

This work is focused on the reduction of the compressive strength of

bamboo at elevated temperature.

2. Test methodologies

Heating of test samples

The samples were tested at temperatures ranging between ambient

temperature (around 23○C) to 250○C.

Thermal penetration tests showed the temperatures changes inside the

samples at different temperatures. The tests were used for defining the

steady state conditions and the temperature inside the sample during the

test.

Figure 1. Thermal penetration test on round bamboo (left) and

variation of temperatures and thermal gradients in the sample (right)

Mechanical tests at elevated temperature

The compression test was developed in a novel set-up. the samples were

mechanically tested within the environmental chamber. and after specific

periods of time, the mechanical test was developed at the same time than

the sample was being heated up.

A set of thermocouples measured the temperature on the sample’s surface

with strain gauges and a load cell also being used to measure strain,

displacements and load.

Figure 2. Compression test set up at elevated temperatures

3. Analysis of compressive strength and failure modes

The compression strengths of the samples were obtained at different

temperatures calculated due to the correlation between surface and interior

temperatures. The strain was taken from the measurements of displacement

delivered by the machine crosshead. Afterwards, new measurements were

incorporated using strain gauges that can accurately be used at

temperatures up to 120○C.

Round bamboo has a substantial drop in the compression strength below

ambient temperature. Between 120○C and 160○C, there is a slight increase

in the strength. Beyond 160○C, the mechanical properties of the samples

decreased significantly.

Figure 3. Tested samples at ambient temperature (left), 120○C

(middle), and 250○C (right)

Figure 4. Stress – strain curves at elevated temperature on round

bamboo

Figure 5. Compressive strength reduction at elevated temperature on

round bamboo

4. Discussion & concluding remarks

Bamboo normally presents an elephant foot buckling failure, which induces

a splitting of the sample due to the low shear strength and poor

perpendicular tension strength of the material. However, a different failure

mode can be seen in samples tested at a higher temperature. e.g. buckling

at half – height or crushing.

At elevated temperatures, the material loses its plastics behaviour, losing

the capacity of resist higher deformations. At lower temperatures, bamboo

keeps resisting load in an inelastic zone.

5. Future work

The same experiments will be used for the testing of laminated bamboo.

Other load conditions will be tested during the development of the PhD

project. Dynamical Mechanical Analysis Tests (DMTA) will be performed

to understand the elasticity modulus variation. Mechanical tests in larger

elements will be conducted at temperatures and heat fluxes below and

above the ignition point.

Bamboo compressive strength at elevated temperaturesMateo Gutierrez, Joshua Madden, and Dr Cristian Maluk

School of Civil Engineering at The University of Queensland

Round Bamboo Sample

Thermocouples on the sample’s surface

Environmental Chamber case

Strain gauges on bamboo’s surface

Mobile machine crosshead for applying compression load