SEGi University College

TITLE : Buckling of Strut

OBJECTIVE : To determine the Euler buckling load for strut undergoing longitudinal loading.

THEORYBuckling is a*fcilure mode characterized by a sudden failure of a structural member subjected to high compressive stresses, where the actual compressive stress at the point of failure is less than the ultimate compressive strength.When a strut is subjected to longitudinal loading, it is possible that the strut suddenly bent to one side and buckle before attaining the admissible compressive strain, due to structural instability. The critical value that causes buckling is commonly understood as the Euler Buckling load,

where E - Young's modulus/ = Second moment of areaLeff = Effective length of the strut (varies with boundary condition).

where Leff = L for pin-pin support; and Leff = f°r

pin-fix support)

APPARATUSForce measurement (hydraulic force measuring device), bottom specimen holder (thrust piece with V notch for knife edge mounting), top specimen holder (long thrust piece with V notch), deformation measurement (measuring gauge), and rod specimens (S3 and S6).

Load spindle Load nut Load cross bar

Basic if amc

horcc measuringdevice

EXPERIMENTAL PROCEDURE1. Insert the top specimen holder into the load cross-bar.

2. Note the dimensions of the rod specimen (S3) at different locations and then insert the rod into the attachment socket.3. Align the rod specimen and then pre-tighten the rod specimen with low, non measurable force.4. Align the measuring gauge to the middle of the rod specimen in such a manner that it is right angle to the length of the rod specimen.5. Increase the load gradually (i.e., 50 N interval) and record the corresponding lateral deflection of the rod specimen at mid-length.6. Stop the procedure when rapid lateral deflection is observed.

1. Repeat Steps 2 to 6 by using rod specimen S6

1.RESULTS AND DISCUSSIONCalculate the second moment of area of the rod specimens and hence determine the Euler buckling load for struts under different boundary conditions, (assuming steel rod with E = 210GPa)Tabulate the results and then plot the graph of lateral deflection vs. force.Compare the difference between the experimental buckling load with the theoretical prediction. Give your comment on the discrepancy obtained, and ways to improve the experimental result.