Name: structure types and force paths
Uploaded: 2023-09-22T11:49:23.000Z
Duration: 1 min 30 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS.P3

HS.P3U2.7

Introduction to Structures

Una struttura è un sistema di elementi interconnessi come travi, puntoni, giunti, ecc., progettati per sostenere o trasferire forze e resistere in sicurezza ai carichi che agiscono su di essi.
Lo smontaggio della struttura e l'analisi dei diagrammi di corpo libero dei singoli membri o di una combinazione di elementi aiuta a determinare le forze interne di una struttura.
Le strutture sono classificate in tre categorie: capriate, telai e macchine.
Le capriate sono strutture fisse e rimangono rigide se sottoposte a forza. Una capriata è costituita da elementi diritti collegati da giunti alle estremità di ciascun elemento. Quindi, i membri di un traliccio hanno due forze uguali e opposte che agiscono lungo il membro.
Un telaio è una struttura rigida e fissa progettata per supportare i carichi. Tuttavia, ha sempre almeno un membro su cui agiscono tre o più forze. Almeno una di queste forze non è diretta lungo l'asse dell'asta.
Le macchine sono strutture non rigide aventi parti mobili progettate per trasmettere e modificare gli effetti delle forze. Almeno un membro multi-forza è presente in una macchina.

<ol>
	<li>Birra, F.P.; Johnston, E.R.; Mazurek, D.F; Cromwell, P.J. e Self, B.P. (2019). Meccanica vettoriale per ingegneri \u2012 Statica e dinamica. New York: McGraw-Hill. pagine 299.</li>
</ol>

Nessun conflitto di interessi dichiarato.

introduzione alle strutture

Una struttura è definita come un sistema di membri interconnessi, progettati per sostenere o trasferire le forze e resistere con successo ai carichi che agiscono su di essi. Le forze interne di una struttura possono essere determinate scomponendo la struttura e analizzando i diagrammi di corpo libero dei singoli membri o di una combinazione di membri. Questo aiuta a comprendere il comportamento degli elementi strutturali e a garantire che la struttura sia stabile e possa sopportare i carichi a cui è sottoposta.

Ci sono tre principali categorie di strutture: capriate, telai e macchine. Le capriate sono strutture fisse che rimangono rigide quando sono sottoposte a forze. I membri di una capriata sono elementi rettilinei collegati da giunti alle estremità di ciascuno di essi. Ogni membro di una capriata ha due forze uguali e opposte che agiscono lungo di esso. Queste sono comunemente utilizzate in ponti, tetti e torri.

I telai sono strutture rigide e fisse progettate per sostenere carichi. I membri nei telai possono subire sia forze assiali che momenti flettenti. Tuttavia, almeno un membro di un telaio ha sempre tre o più forze che agiscono su di esso, e almeno una di queste forze non è diretta lungo l'asse del membro. I telai sono comunemente utilizzati in edifici e strutture industriali, come gru e portici.

Le macchine sono strutture con parti mobili progettate per trasmettere e modificare gli effetti delle forze. Coinvolgono meccanismi che consentono il movimento o la trasformazione delle forze. In una macchina deve essere presente almeno un membro a forza multipla. Le macchine sono comunemente utilizzate in attrezzature, come le presse, e veicoli, come automobili e aerei.

Introduzione alle strutture

Una struttura è definita come un sistema di elementi interconnessi progettati per sostenere o trasferire forze e resistere con successo ai carichi che agiscono su di essi. ...

Education

Didattica

JoVE Core

Mechanical Engineering

Ingegneria Meccanica

Unit 1

Unità 1

Structural Analysis

Analisi Strutturale

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

structure types and force paths

Structures are systems of interconnected members that support or transfer forces and handle the loads placed on them. Engineers can find the internal forces in a structure by breaking it apart and drawing free-body diagrams for individual members or groups of members. This helps show how structural elements behave and how the whole system stays stable under load.

There are three main categories of structures: trusses, frames, and machines. Trusses are stationary structures that stay rigid when force is applied. Their members are straight and connected at the ends by joints, and each member has two equal and opposite forces acting along it. Trusses are commonly used in bridges, roofs, and towers.

Frames are also rigid, stationary structures that support loads. Members in a frame may experience axial forces and bending moments. In addition, at least one member in a frame has three or more forces acting on it, and at least one of those forces is not along the member’s axis. Frames are commonly found in buildings and industrial structures such as cranes and gantries.

Machines are structures with moving parts that transmit and modify the effects of forces. They use mechanisms that allow motion or change how force acts. At least one multi-force member should be present in a machine. Common examples include presses, cars, and planes.

Structure Types and Force Paths

introduction to structures

Structures are systems of interconnected members that support or transfer forces and handle the loads placed on them. Engineers can find the internal forces in a structure by breaking it apart and drawing free-body diagrams for individual members or groups of members. This helps show how structural elements behave and how the whole system stays stable under load. There are three main categories of structures: trusses, frames, and machines. Trusses are stationary structures that stay rigid when...

simple trusses

Simple Trusses and Triangular Frames

Simple trusses are planar trusses built from slender members joined at points in one flat plane. They are designed to carry external loads while using less material and keeping weight low. A truss is a structural framework, and the simple truss is one of its most basic forms. The most basic simple truss uses three members arranged in a triangle. That triangular shape is naturally stable and rigid because of its geometry. It gives students a clear starting point for understanding how larger...

method of joints

Truss Forces Using the Method of Joints

The method of joints is used to find the forces in structural trusses. It relies on equilibrium, which means the forces at a joint must balance. In this model, the truss members are connected by frictionless pins. For a plane truss, the members lie in the same plane. That means each joint has a coplanar and concurrent force system. The analysis begins by identifying and labeling all the joints in the truss. Next, each joint is isolated and shown in a free-body diagram. This diagram includes...

method of joints: problem solving i

Truss Joint Force Analysis by Equilibrium

The method of joints uses equilibrium to find forces in structural trusses. It treats the truss members as being joined by frictionless pins. For each joint, the forces acting there must balance. That balance makes it possible to solve for the member forces one joint at a time. Here, a truss has 20 N acting at joint C and 10 N acting at joint D. The method of joints is used to find FCB, FDC, FDB, and FAD. The analysis starts with a free-body diagram of joint C. Free-body diagram means drawing...

method of joints: problem solving ii

Truss Force Analysis at Joints A to E

Truss force analysis at joints A to E uses the method of joints to find the force in each member. The truss has frictionless joints, a wall support, and a roller support. A 150 N force is applied at joint A, and the member forces are solved from joint to joint. First, the angle between members AC and AB is found using the inverse tangent of the ratio of BC to AB. This gives an angle of 67.38°. A free-body diagram of joint A is then drawn, and each unknown force is split into vertical and...

zero-force member

Finding Zero-Force Members in Trusses

Trusses are frameworks made of slender members that connect at their ends by joints. Engineers and architects use them to stabilize and strengthen structures such as bridges, roofs, and towers. Truss members carry loads through tension and compression so the structure can handle external forces. A key part of truss analysis is spotting zero-force members. A zero-force member is a truss member that carries no stress under loading conditions. During analysis, some members may show zero force,...

method of sections

Truss Member Force Analysis by Sections

Truss member force analysis by sections finds the force in selected members of a truss. In this problem, forces F1 and F2 act at joints B and D. The goal is to determine the forces in members EF, DC, and DF. The method uses the idea that a truss in equilibrium also has each of its sections in equilibrium. A free-body diagram of the whole truss is drawn first. The moment equation about joint A is then used to estimate the support reaction at point E. Next, a cut is made along a sectional plane...

method of sections: problem solving i

Truss Member Force Calculation by Sections

Truss member forces can be found with the method of sections in a symmetrical roof truss. The structure here includes vertical, diagonal, and horizontal members. Each horizontal member is 4 m long. The vertical members FB and HD are 4 m long, and member GC is 6 m long. The roof truss carries loads at several joints. Joints F, G, and H each have a 2 kN load. Joints A and E each have a 1 kN load. To start the analysis, moment equilibrium is used at point A. The force and distance values are...

method of sections: problem solving ii

Truss member force analysis by sections finds the forces in selected members of a wall-mounted truss. The structure here includes diagonal, vertical, and horizontal members. The known loads and member lengths are used to solve for the forces in CB, GB, and GH. A cut is made through members CB, GB, and GH. The right side of the truss is then isolated as a free-body diagram. Next, the moment equilibrium equation is taken about point G. This step gives the force in member CB as 4 kN, and the...

space trusses

Space Truss Forces and Stability

A space truss is a three-dimensional truss made from members joined at their ends. It is the 3D version of a planar truss. These frameworks often use ball-and-socket joints, which help the structure stay stable and flexible under load. Space trusses are used in many construction projects because they can adapt to complex forces. Their basic building block is the tetrahedron. A tetrahedron has six members and four triangular faces. Engineers can build larger space trusses by adding one joint...

space trusses: problem solving

3D Truss Force Analysis with Joint Equilibrium

A space truss is a three-dimensional truss structure made of members connected at their ends. It often uses ball-and-socket joints to form a stable and versatile framework. Because it can handle complex loads, this type of structure is used in many construction projects. The example begins with a tripod made from a tetrahedral space truss. A ball-and-socket joint is located at C. The height and the lengths of the horizontal and vertical members are known. A tensile force is applied at joint D.

frames

Frame Analysis in Structural Systems

Frames are important parts of many mechanical and structural systems used every day. They are valued for stability and for their ability to bear heavy loads. A frame is built from two-force members and multi-force members, and the parts are connected with pin joints. Trusses are different because they are made entirely of two-force members. Frames appear in many practical settings. They can support beams and columns in buildings. They are also used in automobile chassis construction. In the...

frames: problem solving i

Jib Crane Reaction Forces in Frames

Jib crane reaction forces in frames are found by analyzing the pin joints, the cable tension, and the load carried by the pulley. The structure in this problem has an external load suspended from the pulley, and the member sizes are shown in the figure. Because the pulleys are frictionless, the force balance can be worked out step by step. The frame has two main parts. Member BD is a two-force member, which means it is a straight part loaded only at its two ends, D and B. Those end forces are...

frames: problem solving ii

Hydraulic Hoist Force Analysis

Hydraulic hoist force analysis shows how to find the forces in key members of a simple frame. The load is 1 kN, and the structure is represented with known member dimensions. In this setup, BF and BD act as two-force members. EFG and EDC are multi-force members, so each one is analyzed with a free-body diagram. The first step is to study member EFG. The inclined force in BF is split into vertical and horizontal parts. Then the moment equilibrium condition is applied at joint E. Using this...

machines

Cutting Pliers as a Force-Multiplying Machine

Cutting pliers are a machine that helps transmit force through movable, pin-connected members. In this example, the handles and cutting edges work together to cut wire by turning an input force into a larger output force at the jaws. When equal and opposite forces are applied to the handles, the cutting edges move toward each other. They then apply equal and opposite reaction forces to the wire. These reaction forces are greater than the forces applied to the handles, which is why the wire can...

machines: problem solving i

Toggle Clamp Force Analysis

A toggle clamp can be analyzed to find its clamping force from a known handle force. In this example, a 200 N force is applied at the handle. The clamp is used in holding and clamping tasks in woodworking, metalworking, and assembly operations. The toggle clamp is a machine structure made of movable, pin-connected multi-force members. These members form a stabilized system that transmits force. Member CD is a two-force member, which means the forces at its ends are equal in magnitude and...

machines: problem solving ii

Lifting Tong Force Analysis

Lifting tong force analysis shows how forces move through a pin-connected machine. The structure uses movable sections DAF and CBG with member AB linking them together. Because these parts work as connected members, the load can be studied with equilibrium methods. The example starts with a 100 kg load at point E. The load weight is found by multiplying mass by gravity, which gives 981 N. The cable tension acts upward and balances that weight. Since the structure is symmetrical at E, the...

key terms and concepts

Learn how structures carry loads through trusses, frames, and machines. Explore force paths, free-body diagrams, and real-world examples for grades 9–12.

Structure Types and Force Paths | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Position and Displacement

The position of an object defines its location relative to a convenient frame of reference at any particular time. A frame of reference is an arbitrary ...

Average Velocity

To calculate the other physical quantities in kinematics, we must introduce the time variable. The time variable allows us not only to state the position ...

Average Acceleration

The importance of understanding acceleration spans our day-to-day experiences, as well as the vast reaches of outer space and the tiny world of subatomic ...

Instantaneous Acceleration

Acceleration is in the direction of the change in velocity, but it is not always in the direction of motion. When an object slows down, its acceleration ...

velocity-and-position-by-graphical-method

Velocity and Position by Graphical Method

Velocity and position can be calculated from the known function of acceleration as a function of time. The total area under the acceleration-time graph ...

Kinematic Equations - I

When an object moves with constant acceleration, the velocity of the object changes at a constant rate throughout the motion. The kinematic equations of ...

Kinematic Equations: Problem Solving

When analyzing one-dimensional motion with constant acceleration, the problem-solving strategy involves identifying the known quantities and choosing the ...

Force

Forces affect every moment of our life. Our bodies are held to the Earth by force, and they are held together by the forces of charged particles. When we ...

Mass and Weight

Mass and weight are often used interchangeably in everyday conversation. For example,&#160; medical records often show our weight in kilograms, but never ...

Newton's Laws of Motion

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment examines at various situations involving two interacting ...

Newton's First Law: Introduction

Motion draws our attention. Motion itself can be beautiful, causing us to marvel at the forces needed to create spectacular sights, such as that of a ...

first-law-particles-in-one-dimensional-equilibrium

First Law: Particles in One-dimensional Equilibrium

Newton&#39;s first law of motion states that a body at rest remains at rest, or if in motion, remains in motion at constant velocity, unless acted on by a ...

Newton's Second Law

Newton&#39;s second law is closely related to his first law of motion. It mathematically gives the cause-and-effect relationship between force and changes ...

Force and Acceleration

Source: Nicholas Timmons,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of California, Irvine, ...

Second Law: Motion under Same Force

Newton&#39;s laws can be applied to bodies at rest and bodies in motion. Newton&#39;s first law is applied to bodies in equilibrium, whereas the second ...

Newton's Third Law: Introduction

Whenever one body exerts a force on a second body, the first body experiences a force equal in magnitude and opposite in direction, to the force that it ...

Drawing Free-body Diagrams: Rules

The first step in describing and analyzing most phenomena in physics involves the careful drawing of a free-body diagram. Free-body diagrams are useful in ...

Free Body Diagrams: Examples

Solving problems that involve forces is easy using free-body diagrams. A free-body diagram is a sketch showing all the external forces that are acting on ...

Equilibrium and Free-body Diagrams

Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of California, ...

Collect, analyze and interpret data regarding the change in motion of an object or system in one dimension, to construct an explanation using Newton’s Laws.

HS.P3U1.6

Solving Problems in Physics

Problem-solving is the ability to apply general physical principles to specific situations, usually expressed by equations. It is an essential skill in ...

Problem Solving in Statics

Problem-solving in statics is a crucial aspect of engineering and physics that involves resolving issues associated with bodies in a state of equilibrium. ...

An Introduction to Mechanics

Humans have been making ships, shelters, pyramids, weapons, agricultural equipment, and many more items without recording the process or theory behind ...

A structure is defined as a system of interconnected members designed to support or transfer forces and successfully withstand the loads acting on them. ...

Simple Trusses

A truss is a structural framework consisting of slender members connected at joints, designed to support external loads while minimizing material usage ...

Method of Joints

The method of joints is a commonly used technique to analyze the forces in structural trusses. The method is based on the principle of equilibrium, which ...

Rigid Body Equilibrium Problems - I

A rigid body is said to be in static equilibrium when the net force and the net torque acting on the system is equal to zero. To solve for rigid body ...

Stability of structures

Consider two rods connected at point O by a pin and a torsional spring of constant k. The ends of both the rods are pin-connected.
If both the rods are ...

Buckling of Steel Columns

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
In the design of civil works, it is important ...

Machines

Machines are complex structures consisting of movable, pin-connected multi-force members that work together to transmit forces. One example of a machine ...

DC Motors

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. 
The DC machine operates with DC currents and voltages as ...

Rolling Resistance

When a solid cylinder rolls steadily on a rigid surface, the normal force applied by the surface on the cylinder is perpendicular to the tangent at the ...

Propulsion and Thrust

Source: Alexander S Rattner; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
Aircraft, rockets, ...

Rocket Propulsion in Empty Space - I

The driving force for the motion of any vehicle is friction, but in the case of rocket propulsion in space, the friction force is not present. The motion ...

aerodynamic-performance-of-a-model-aircraft-the-dc-6b

Aerodynamic Performance of a Model Aircraft: The DC-6B

Source: Jose Roberto Moreto and Xiaofeng Liu, Department of Aerospace Engineering, San Diego State University, San Diego, CA
The low-speed wind tunnel is ...

airfoil-behavior-pressure-distribution-over-a-clark-y-14-wing

Airfoil Behavior: Pressure Distribution over a Clark Y-14 Wing

Source: David Guo, College of Engineering, Technology, and Aeronautics (CETA), Southern New Hampshire University (SNHU), Manchester, New Hampshire
An ...

Use mathematics and computational thinking to explain how Newton’s laws are used in engineering and technologies to create products to serve human ends.

Structure Types and Force Paths

Description

Transcript

Tags

More videos by Standards