SM-1421 Parabolic Arch Apparatus

Experiments

  • Mechanical principles of the parabolic arch.
  • Differences between statically determinate and statically indeterminate arches.
  • Measurement of the deformations of the arch under load.
  • Measurement of the support reactions on the statically indeterminate arch under load.
  • Calculation of the support reactions.
  • Influence of point load or distributed load on reaction forces and deformation of the arch.

Specifications

  • Investigation of a parabolic arch, optionally statically determinate (1 fixed support, 1 movable support) or indeterminate (2 fixed supports).
  • Loading of the arch with a distributed load by way of 7 evenly distributed weight positions or by point loads.
  • Dial gauges record the deformation of the arch under load.
  • Weights to compensate for the reactions of a fixed support.
  • Storage system to house the components.
  • Experimental set-up in frame.

Description

In this apparatus the major components are arch, point or distributed load and dial gauge. Out of two ends of the arch one is fixed and the other one is on the roller bearing. The purpose of dial gauge is to measure the deflection of arc under the horizontal thrust which is created by applying loads on the arch. Loads are applied through vertically suspended hangers with the arch at equal distances.

Parabolic arches are popular elements in construction engineering. They can be employed as bridges or beams for example. Normally these bridges are statically indeterminate. The special feature of the parabolic arch is that in the arch only normal forces and bending moments occur, but no shear forces. That is the case when the arch is subjected to a uniform distributed load and both ends are mounted in fixed bearings. This enables arches to be constructed from loosely set stones – a construction technique which has been in existence for many centuries. Loads acting upon the inner of the arch are primarily compressive forces in the direction of the normal force at every point of the arch.

SM-1421 includes a pre-shaped parabolic arch. It can be subjected to point or distributed loads. One of the arch’s supports is fixed, the other is on a roller bearing. Weight sets are used to cancel this movement. The movable support thus becomes a fixed support. Additional weight sets compensate for the vertical support reaction.

Dial gauges record the deflection of the arch under load and the horizontal displacement of the movable bearing. As long as the roller bearing is movable, the arch is statically determinate, though it is substantially deformed under load. As soon as the roller bearing becomes immovable, the arch is no longer statically determinate and is deformed only to a minor degree.

All the component elements of the experiment are clearly laid-out and housed securely in a storage system.

The complete experimental set-up is arranged in the frame.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.