Unimap Module

To develop the ability to model or idealize a structure so that the structural engineer can perform a practical force analysis of the members


*Support Connections
- Pin connection (allows some freedom for slight rotation)
- Roller support (allows some freedom for slight rotation)
- Fixed joint (allows no relative rotation)
- E.g. are shown in Fig 2.1 & 2.2
- Idealized models used in structural analysis are shown in Fig 2.3

Fig 2.1 & 2.2 & 2.3



Fig 2.1 & 2.2 & 2.3


Fig 2.1 & 2.2 & 2.3



*Support Connections
- In reality, all connections exhibit some stiffness toward joint rotations owing to
friction & material behavior
- A more appropriate model for a support or joint might be that shown in Fig 2.3 (c)
- If k = 0 the joint is pin and -> , the joint is fixed
- When selecting the model for each support, the engineer must be aware how the
assumptions will affect the actual performance
- The assumptions must be reasonable for the structural design
- The analysis of the loadings should give results that closely approximate the
actual loadings
- Common types of connections on coplanar structures are given in Table 2.1
- In reality, all supports actually exert distributed surface loads on their
contacting members
- The concentrated forces & moments shown in Table 2.1 represents the resultants of
these loads distributions

Table 2.1



*Idealized Structure
- Consider the jib crane & trolley in Fig 2.5(a)
- For analysis, we neglect the thickness of the 2 main member & will assume that the
joint at B is fabricated to be rigid
- The support at A can be modeled as a fixed support
- Details of trolley can be excluded
- The members of the idealized structure is shown in Fig 2.5(b)


Idealized Structure
Fig 2.5


Idealized Structure
Consider the framing used to support a typical floor slab in a building as shown in Fig 2.6(a)

The slab is supported by floor joists located at even intervals
These are in turn supported by 2 side girders AB & CD