Structural Systems & Forces

Role of Structural Systems

• Structural systems are essential for buildings and bridges to perform tasks related to forces and stability.
• These systems facilitate interaction between the structure and loads.
• They direct forces appropriately.

Loads Changing Over Time

• Structures bear different types of weights, some permanent and others temporary.
• Live loads, such as furniture inside a room, exemplifies how a load can vary over time.

Structural Support Restricting Movement

• Some structural supports restrict movement and rotation at connection points completely.
• Supports provide the highest degree of constraint, preventing displacement or turning

Interaction Between Forces

• Forces always act in pairs in opposite directions
• When force is applied to an object, it exerts a force back

Forces Structural Systems Resist

• Structural systems are designed to resist forces that directly impact stability and safety.
• Structural systems must withstand permanent, variable, and environmental forces.
• Decorative elements are not a primary force structural systems are designed to resist.

Pinned Connection Behavior

• A pinned connection in structural frameworks primarily allows connected elements to turn relative to each other.
• A hinge exemplifies a pinned connection; it allows rotation.

Structural System Relying on Internal Resistance

• Some structural systems maintain stability based on their shape, whereas others rely on flexible connections.
• The stiffness and strength of components and joints ensures load bearing

Moment in Structural Mechanics

• Moment in structural mechanics refers to a the tendency of a force to cause rotation.
• Moment relies on magnitude of force and its distance from a pivot point
• The standard unit of measurement is kilonewton meters (kN.m).

Natural Structures Resisting Pulling Forces

• Tension refers to a force that stretches or pulls.
• A spiderweb exemplifies a structure in nature where thin, elongated elements are pulled taut.

Forces Resisted by Vertical Load-Bearing Elements

• A column supports weight from above, which results in compression.
• Primary force resisted by a column is compression.

Hyperstatic Structural Systems

• Hyperstatic structures are rigid because they have more supports than needed for equilibrium.
• Fixed-fixed beams exemplify a hyperstatic structural system.

Purpose of Foundations

• The foundation acts as the interface between the structure and the ground.
• Foundations manage forces to ensure stability and longevity

Diagrams for Internal Rotational Forces

• Bending moment diagrams are used in structural analysis to represent the variation of internal rotational forces along the length of a beam.

Structures General Function

• Structures support loads
• Structures transfer loads safely to the ground

Live Load

• Live loads can change or move on a structure
• Furniture is an example of a live load

Supports Preventing Rotation and Translation

• Fixed supports prevent rotation and translation in all directions

Newtons Third Law

• For every action, there is an equal and opposite reaction.

Types of Structural Load

• Structural loads are forces that act on a structure
• Dead loads are permanent, while environmental loads are due to nature.
• Decorative loads are not a type of structural load.

Pinned Supports

• Pinned supports allow rotation only

Rigid Frame Systems

• "Rigid frames" are a classic example of structures where the members themselves (sections) and their rigid connections are key to load resistance.
• Rigid frames leads elements to both transfer forces and moments
• Section-active structural system, resistance relies on internal stresses

Natural Tension Resistance

• A spiderweb exemplifies efficient tension resistance because made of threads pulled taut.

Hyperstatic Structure

• Fixed-fixed beams represents the most restrictive support conditions.
• Statically indeterminate describes a hyperstatic structure

Foundation Purpose

• Distributes the weight from the loads to the ground

Diagrams Measuring Variation

• It is a bending moment diagram

Major Differences Between Structures

• Trusses primarily resist axial forces.
• Frames resist bending moments.
• Trusses have pinned connections, frames have rigidly connected members

Torsion

• Torsion is twisting force

Primary Load for Structures

• Beams must resist bending

Buckling

• Buckling represents instability due to compression

Significance of a Materials Attributes

• Modulus of elasticity determines stiffness of objects

Form Active Structural Systems

• An arch is an example

Shear Force

• Shear force is the force towards the surface