Modelling a Frame Subjected to Multiple Loading Conditions

Topics: Theory, Physics, Experiment Pages: 6 (1337 words) Published: March 5, 2014

LAB REPORT

Pin Jointed Frame

1312800
1st year school of engineering University of Warwick

Date Submitted: 8/01/2014

Summary

In this experiment the main aim was to modelling a frame subjected to multiple loading conditions and record how the force and strain vary to different loads. The frame represented a simple roof trusses and the loading conditions are similar to what a typical roof would undergo. In this experiment a universal fame was used with load cells to provide the load and digital force and strain instruments to record the data. As the load was increased the strain went up linear showing a linear relationship between loading and strain. After analysing results it was found that the results for experimental forces compared to theoretical forces were very close showing that this experiment was very accurate, with very small uncertainty, the reason for this is due to very sensitive equipment as a change of 1µϵ is equivalent to change of 6 N (using young’s modulus) and other factors described in detail in the report.

Table of Contents

Summary
1 Introduction Pg 4 2 Theory Pg.4 3.1 Apparatus Pg 6 3.2 Experimental procedures Pg 8 4 Observation and results Pg 8 4.1 Results Pg8 4.2 Observations Pg11 4.3 Discussion Pg11 4.4 Sources of error Pg11 5 Conclusions Pg12 References Pg13 Appendices Pg13 Introduction The aim of this laboratory was to carry out an experiment to measure the strain in members of a frame, where load was being applied in different loading conditions. This experiment was carried out to put to use the theory learnt in lectures and see how they actually perform in a real life model. By doing this it is possible to appreciate the limit of theoretical approach to these loading conditions and compare the errors. The model used in the experiment was that of an idealised roof truss, a roof must withstand a lot of force over a long time during its lifetime. Three 3 different loading scenarios will be modelled and the strain forces are expected to be within the range of the calculated theoretical forces. Main aims were: 1. Measure the strain in each member and record results

2. Calculate theoretical values for the experiment
3. Compare theoretical values with experimental results and calculate percentage error

Theory

In a frame model where there is a load being applied members of the frame will feel a compressive or tensional force. The value of the force can be worked out by resolving the forces in horizontal and vertical directions and taking moments. This is done by analysing each of the joints of Fig 1 separately. In a rigid static frame the sum of the vector forces add up to zero

Fig 1 model of experiment
The first loading model has is simulated with a load of 500N. First work out the value for the reaction force at the supports. Then use these values to calculate the tension in each...


References: Mechanics structures and thermo dynamics –university of Warwick
Mechanics lectures by Dr. T. Karavasilis
http://www.tecquipment.com/Datasheets/STR8_0213.pdf 29/12/2013
Appendices
Pin jointed lab briefing sheets
Theory (1.)
(2). Stress strain thoery
Briefing sheet
http://www2.warwick.ac.uk/fac/sci/eng/eso/modules/year1/es184/studentresource/ms/lab_handout2012.pdf
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