How to find shear force? How to find bending moment and shear force?

Let's start with shear force. Let's say from a simply supported beam.

Take out a small micro-element body ——— arbitrarily

1) If the left side of the small element body is subjected to downward shear force and the right side is subjected to upward shear force, then the shear force on the micro element is negative;

2) If the left side of the microelement is subjected to an upward shear force and the right side is subjected to a downward shear force, then the shear force of the microelement is positive.

To put it simply, the shear force all occurs in pairs, and the shear force is clockwise.

is positive, counterclockwise is negative, this is structural mechanics.

Inside.

Let's talk about bending moment: Structural mechanics says that when a beam is bent by bending moment, it is stipulated that the tensile side is positive and the compression side is negative. A theoretical model is involved here, that is, a beam is bent into three parts, with the tension side, the compression side, and the neutral layer, that is, the part that is neither tensile nor compressed.

Let's say a cantilever beam.

When the outermost end is subjected to concentrated load, the upper side of the beam should be drawn on the upper side of the beam.

After talking about the theory, let's talk about your question. The first point: clockwise and counterclockwise when judging the positive or negative shear force has no relationship with the selected reference point. That is, choose any point to be the same. The second point: talk about the steps of this kind of question———

1) Draw a shear force diagram: a Calculate the support reaction, which is the first step in the answer;

b first determine the shear force of a, b, c and then connect the line;

Point A has no support and zero shear force.

The shear force at point C is equal to the reaction force of the support, and then the shear force of any small element near point C is negative counterclockwise. (Actually, it's not as troublesome as what I wrote, but let's be more detailed in order to make the problem clear).

The left and right sides of point b shear force are different. When calculating the left force, the left beam is selected to study, the magnitude is calculated, and the direction is judged. The right shear force is the left shear force plus the support reaction.

cConnect the four points with a straight line.

The formula for calculating the shear force corresponds to the graph, needless to say, hehe.

2) Draw a bending moment diagram.

Just like drawing a shear force diagram, drawing a bending moment diagram is to first determine the bending moment of the key points, and then connect the lines.

The bending moments at points A and B are zero;

Then calculate the magnitude of the moment at point C (you can use the left side as the object of study to take the moment at point C), and the direction is drawn on the upper side because of the tension on the upper side. Then use a curve to connect the three points.

By the way, the derivative of the bending moment is the shear force, and it is said that the point bending moment with zero shear force goes to the extremum, which is the origin of the 9/128 on the graph you gave.

Of course, this can also be done: after the shear force diagram is drawn, the bending moment at any point is the area enclosed by the corresponding shear force diagram. I feel that this is how the formula for calculating the bending moment in the diagram you gave is listed.

He seems to assume that the bending moment is negative when the area surrounded by the shear force is below, and positive vice versa).

Writing so much, I hope it helps you.

Shear force, also known as shear force: "Shear" is a relative dislocation deformation phenomenon that occurs in the cross-section of a pair of materials along the direction of action of a pair of transverse external forces that are very close to each other, of the same magnitude, and pointing to opposite directions. The force that causes a material to shear deformation is known as shear or shear force.

The section in which shear deformation occurs is called a shear plane. The key to determining whether the material is "sheared" is whether the cross-section of the material is relatively dislocated.

Determine the positive and negative: if a small microelement is arbitrarily taken from a simply supported beam, if the left side of the small microelement is subjected to downward shear force and the right side is subjected to upward shear force, then the shear force on this microelement is negative; If the left side of the element is subjected to an upward shear force and the right side is subjected to a downward shear force, then the shear force on the element is positive.

The shear force is in pairs, the shear force is positive clockwise and negative counterclockwise, which is stipulated in structural mechanics.

Shear force, also known as shear force: "Shear" is a relative dislocation deformation phenomenon that occurs in the cross-section of a material along the direction of action of a pair of transverse external forces (i.e., forces perpendicular to the applied surface) that are very close to each other and of the same magnitude and point to the opposite direction. The force that causes a material to shear deformation is known as shear or shear force.

The section in which shear deformation occurs is called a shear plane. The key to determining whether the material is "sheared" is whether the cross-section of the material is relatively dislocated.

1. Simply put, shear force.

All come in pairs, and the shear force is clockwise.

It is positive and counterclockwise is negative, which is stipulated in structural mechanics. The cross-section is on the left, the shear force is positive upwards, and the bending moment.

Positive clockwise, if the cross-section is positive downward with shear force on the right, the bending moment is positive counterclockwise.

2. There are different regulations on the positive and negative of bending moments in different disciplines. By specifying the positive and negative moments, the bending moments can be calculated algebraically. As informed.

In the calculation of column bending moments, the discrimination method of "positive for upper left and lower right, negative for lower left and upper right" is applied.

3. Where the moment of the external force on the left side of the beam of the section is clockwise turning, or the moment of the external force on the right side of the section is counterclockwise turning, a positive bending moment will be generated, so the positive sign is taken; Otherwise, it is negative, that is, the left is backward and the right is reversed, and the bending moment is positive.

4. For a beam in a civil engineering structure (referring to the horizontal component spike), when the lower side of the component section is tensile, we call the bending moment of this section as the positive bending moment; When the upper side of a component segment is under tension, we call the bending moment on this segment a negative moment.

The formula for calculating the shear force is ws a(kg mm2). Shear force refers to the friction between blood flow and vascular endothelium, which is closely related to blood characteristics, blood flow velocity and vascular morphology, and the circumferential force is determined by blood pressure level and arterial diameter.

When two objects that are in contact with each other and squeezed each other, when they are in relative motion or have a relative tendency to motion, a force is generated on the contact surface that hinders the relative motion or relative tendency of motion, and this force is called friction. The direction of frictional force is opposite to the direction of the relative motion of the object or the relative tendency of motion.

Definition of shear force

The resultant force of the external force acting on both sides of the component is a transverse concentrated force with equal magnitude and opposite directions, and the lines of action are very close to each other. Under the action of such an external force.

The deformation characteristics of the component are: the cross-section between the two forces is the dividing line, and the two parts of the component are relatively dislocated along the surface. This form of deformation of a component is called shear, and its cross-section is a shear plane. The magnitude of the shear force per unit area of a cross-section is called the shear stress.

Question 1: How to calculate shear force? When the member is intercepted, the shear force on the side is positive downward, and the right side is upward, and in short, the shear force turns clockwise around the rod to be positive. The equation is calculated in the direction of the shear force, and the result is that the positive assumption is the same, otherwise the shear force is assumed to be in the opposite direction.

Question 2: How to calculate the shear force calculation formula of simply supported beam Take a look at **, this is the most basic force mode. If you want to go deeper, please find this manual of structural static potato knowledge and surplus calculation.

Question 3: How to calculate the shear force of the simply supported beam bending moment 1 8ql2 shear force 1 2ql

Question 4: How to calculate the size of the shear force in the middle, and the specific points of the troublesome answer, thank you! The picture above is an I-beam simply supported beam.

According to the moment balance at point a, 50*300+100*1700=rb*2100

It can be seen that the reaction force of point B support is, and the overall static balance can know that the reaction force of point A is.

Based on this, you can draw a shear force diagram from left to right.

Due to the reaction force at point A, the shear force diagram abruptly changes upward, 50 at the P1 point, 100 points at the P2 point, and 100 points at the P2 point, and points B changes upward.

Problem 5: Calculation of shear force of column When calculating the shear force of the column, it is necessary to divide the shear force caused by the load and the shear force caused by the bending moment. The formula for the fierce shear force due to the load is:

Shear force q = resultant force of all loads in the direction of q) A certain bending moment m causes the shear force at one end of the column = m h, and the shear force resultant force for the column = 0. (h is the calculated length of the column) pay attention to the superposition of the positive and negative signs of the shear force caused by the load and the shear force caused by the bending moment.

Question 6: How to calculate the shear force caused by the bending moment Take this section of the beam, draw m, various forces on the beam, etc., the shear force at the end of the beam, v left, v right then find the moment on the left end m right + m left + the force on the beam various moments on the left end + v right * the distance between the two ends of the beam = 0 can find v right to the right end of the moment m right + m left + various forces on the beam on the left moment + v left * distance from the two ends of the beam = 0 can find v left [in a word, that is, take the beam segment, the force is added, the balance equation of the force, and the two shear forces are solved].

Question 7: How to calculate the beam end shear force from the beam end bending moment v left = ql 2 + (m right - m left) l or v right = ql 2 - (m right - m left) l, this calculated value is a positive value, regardless of direction.

Shear force. Formula: =ws a(kg mm2), according to the known load acting on the beam, after finding the supporting reaction force of the statically determined beam, the internal force on the beam cross-section can be solved by using the "cross-section method" mentioned above, simply supported beam.

In equilibrium under the action of external forces, the internal forces on the cross-section of the stool are now discussed at a distance of the support.

First, find the bending moment of the node mu cherry brigade.

The bending moment of the column end is obtained by assigning the member end (including the column end) of each member assigned to the node, and according to the bending moment of the column end, the shear force of the column end is set as an unknown number, and the member moment balance equation is listed to obtain the shear force of the column end; According to the sum of the shear force at the end of the beam from the beams on both sides of the column top and the axial force at the bottom of the upper column at the top of the column, it is the axial force at the upper end of the column, and the axial force at the upper end of the column plus the self-weight of the column is the axial force at the lower end of the column.

1. Average shear stress v - calculate the shear force on the cross-section;

a - calculate the cross-sectional area;

b - cross-sectional width; h - high cross-section.

Minemate Kano value stress.

2. Shear force calculation formula based on shear flow.

v——Calculate the shear fluid force acting along the web plane;

s - calculate the area moment of the neutralization axis above or below the section above or below the shear stress (static moment is shouted);

i – moment of inertia of the cross-section;

t - web thickness.