JNTU B.Tech II STRUCTURAL ANALYSIS I Previous Question Paper (July/August - 2021 - R13)

To determine the forces in the members of a plane truss, we apply the principles of static equilibrium. The process involves calculating support reactions followed by the method of joints or the method of sections.

1. Identify the support conditions and calculate the global reactions at the supports by applying the equations of equilibrium: ΣF_x = 0, ΣF_y = 0, and ΣM = 0.
2. Select a joint where there are at most two unknown member forces. Apply the equations of equilibrium at this joint (ΣF_x = 0 and ΣF_y = 0) to solve for the unknown forces.
3. Proceed to adjacent joints sequentially, using the previously determined member forces as known values until all member forces are calculated.
4. For members in tension, the force will be positive (pulling away from the joint), and for members in compression, the force will be negative (pushing towards the joint).
5. Alternatively, use the method of sections by cutting the truss through a maximum of three members with unknown forces. Apply equilibrium equations to the isolated section to solve for the internal forces directly.

The final forces in the members are determined by checking the consistency of results across all joints to ensure the entire structure remains in equilibrium under the applied loads.

Frames are structural systems composed of beams and columns connected by rigid or pinned joints, designed to resist both vertical and lateral loads. They are primarily classified based on their geometry, support conditions, and the nature of their joints.

1. Rigid Jointed Frames (Plane Frames)

In these frames, the joints are capable of resisting moments, shears, and axial forces. The angle between members remains constant even after deformation. They are highly redundant and provide significant stability against lateral loads like wind or seismic forces.

2. Pin-Jointed Frames (Trusses)

These consist of members connected by frictionless pins. The members are subjected only to axial tension or compression, with no bending moments. They are typically used for long-span structures such as roof trusses and bridges.

3. Portal Frames

These are simple, single-story, rigid-jointed frames consisting of two vertical columns connected by a horizontal beam. They are widely used in industrial buildings and warehouses to provide large, unobstructed floor spaces.

4. Multi-Storey Frames

These are complex structures consisting of multiple bays and multiple stories. They are designed to transfer loads from the roof and floors through beams to the columns and finally to the foundation. These frames are analyzed as indeterminate structures due to the continuity of members at joints.

5. Gable Frames

A variation of the portal frame where the roof is sloped (pitched) rather than flat. This design is efficient for shedding rain or snow and allows for greater interior height at the center of the span.

6. Non-Sway vs. Sway Frames

Frames can also be classified by their lateral stability. A non-sway frame is prevented from moving horizontally by bracing or shear walls, whereas a sway frame is free to undergo lateral displacement under horizontal loading.