8/12/2019 Structures Plastic collapse of a portal frame

1/2

ECM2109 Structures

Plastic collapse of a portal frame

1 Aim

The aim of this experiment is to examine how structures behave in reality and to see how physicalexperiments compare with the theory you have been learning in the lectures.

2 Objectives

1. To examine the elastic and elasto-plastic behaviour of a portal frame under increasing load.

2. To observe the onset of plasticity and its consequences.

3. To compare the theoretical value of the plastic collapse load for a statically indeterminatestructure with that found in experiment.

3 Apparatus

The apparatus comprises a loading rig into which has been clamped a model portal frame madeof of mild steel section with a uniform rectangular section. The loading system is provided bya system of cables which is designed to apply a vertical load at the centre of the beam and ahorizontal load at the top of one column.

Two gauges have been placed in order to monitor the horizontal deflection of the beam and itscentral vertical deflection.

4 Experimental procedure

The nominal centre-line dimensions of the portal frame are as shown in Figure 1 but you shouldverify that they are accurate.

W

W

300 mm

200 mm

Figure 1: Nominal dimensions of the portal frame

1

8/12/2019 Structures Plastic collapse of a portal frame

2/2