From 9a614e7f4fb5fef3e5fa7e9351e1647089fb0482 Mon Sep 17 00:00:00 2001
From: Peter Mackenzie-Helnwein on deflection, rotation, transverse shear and the bending moment in a single span beam. This tool employs the Bernoulli-Euler beam theory. This theory, also
known as shear rigid beam theory, is based on the kinematic assumption
that
- Any plane cross section perpendicular to the undeformed beam’s
+ Any plane cross section perpendicular to the undeformed beam’s
axis remain plane and perpendicular to the axis throughout the
- deformation. This allows us to reduce the three-dimensional problem to a single unknown
+ deformation. This allows us to reduce the three-dimensional problem to a single unknown
function, v(x), known as deflection of the beam.
- Navier’s assumption leads to
- Navier’s assumption leads to
+" class="math-display" >
This displacement field induces an axial strain of
-
+" class="math-display" >
Equation (2) states that a fiber parallel to the beam axis stretches in the bottom
portion of the beam (y < 0) and contracts if the fiber is located above the beam
axis (y > 0). The beam axis itself does not stretch.
-
-
For a slender beam, we can ignore stress components acting perpendicular to the
+ For a slender beam, we can ignore stress components acting perpendicular to the
beam’s axis. Thus, the constitutive relations can be simplified as the 1D-version
of Hooke’s law:
-
+" class="math-display" >
where E is the modulus of elasticity.
- The imposed state of deformation induces normal stress proportional to the
+ The imposed state of deformation induces normal stress proportional to the
strain field (2) as
-
+" class="math-display" >
This relation states that (i) the stress varies linearly with the distance from the
beam’s axis, vanishing at the axis, and (ii) the stress is proportional to the
curvature of the beam.
-
-
The beam sees two stress resultants: the internal moment,
- The beam sees two stress resultants: the internal moment,
+
+M (x) = - A yσ(x,y)dA
+" class="math-display" >
and the transverse shear force,
-
+" class="math-display" >
Substituting (4) into (5) yields
-
+" class="math-display" >
where
-
+I = y2dA
+ A
+" class="math-display" >
is the area moment of inertia or, short, moment of inertia.
- Note that the modulus of elasticity, Note that the modulus of elasticity, E, characterizes the material, the
moment of inertia, I, characterized the shape of the cross section, and the second
@@ -191,11 +173,11 @@
-
Equilibrium is formulated in terms of shear forces, Equilibrium is formulated in terms of shear forces, V (x), and internal moments,
5 x). Equilibrium of forces on an beam element of infinitesimal length,
formulated in the y-direction, yields
-
+" class="math-display" >
where w(x) is the distributed lateral load per length. 5 x) is defined positive if
pointing against the (upward) positive y-axis.
- Moment equilibrium around the out-of-plane axis on the same element
+ Moment equilibrium around the out-of-plane axis on the same element
yields
-
+src="theory9x.png" alt="M ′(x) = V (x) .
+" class="math-display" >
A system for which equations (9) and (10) are sufficient to determine the
@@ -241,11 +219,11 @@ Simple Beam Educational Tool
-(version 1.0, released Winter 2019)
+(version 1.1, released June 2019)
(version 1.0, released Winter 2019)
Version history
+
+
+
diff --git a/docs/help/theory.4ct b/docs/help/theory.4ct
index 3241f03..5bd936c 100644
--- a/docs/help/theory.4ct
+++ b/docs/help/theory.4ct
@@ -7,4 +7,8 @@
\doTocEntry\tocsection{5}{\csname a:TocLink\endcsname{1}{x1-50005}{QQ2-1-6}{Equilibrium}}{10}\relax
\doTocEntry\tocsection{6}{\csname a:TocLink\endcsname{1}{x1-60006}{QQ2-1-7}{Governing equation}}{11}\relax
\doTocEntry\tocsection{7}{\csname a:TocLink\endcsname{1}{x1-70007}{QQ2-1-8}{Finding moment, shear force, and slope from the displacement function}}{12}\relax
+\doTocEntry\tocsection{8}{\csname a:TocLink\endcsname{1}{x1-80008}{QQ2-1-9}{Examples}}{14}\relax
+\doTocEntry\tocsubsection{8.1}{\csname a:TocLink\endcsname{1}{x1-90008.1}{QQ2-1-10}{Single span beam with constant distributed force}}{14}\relax
+\doTocEntry\tocsubsection{8.2}{\csname a:TocLink\endcsname{1}{x1-100008.2}{QQ2-1-11}{Single span beam with a single concentrated force}}{20}\relax
+\doTocEntry\tocsubsection{8.3}{\csname a:TocLink\endcsname{1}{x1-110008.3}{QQ2-1-12}{Single span beam with a concentrated force and distributed load using the stiffness method}}{23}\relax
\par
diff --git a/docs/help/theory.4tc b/docs/help/theory.4tc
index d13b88e..fe520f3 100644
--- a/docs/help/theory.4tc
+++ b/docs/help/theory.4tc
@@ -7,3 +7,7 @@
\doTocEntry\tocsection{5}{\csname a:TocLink\endcsname{1}{x1-50005}{QQ2-1-6}{Equilibrium}}{10}\relax
\doTocEntry\tocsection{6}{\csname a:TocLink\endcsname{1}{x1-60006}{QQ2-1-7}{Governing equation}}{11}\relax
\doTocEntry\tocsection{7}{\csname a:TocLink\endcsname{1}{x1-70007}{QQ2-1-8}{Finding moment, shear force, and slope from the displacement function}}{12}\relax
+\doTocEntry\tocsection{8}{\csname a:TocLink\endcsname{1}{x1-80008}{QQ2-1-9}{Examples}}{14}\relax
+\doTocEntry\tocsubsection{8.1}{\csname a:TocLink\endcsname{1}{x1-90008.1}{QQ2-1-10}{Single span beam with constant distributed force}}{14}\relax
+\doTocEntry\tocsubsection{8.2}{\csname a:TocLink\endcsname{1}{x1-100008.2}{QQ2-1-11}{Single span beam with a single concentrated force}}{20}\relax
+\doTocEntry\tocsubsection{8.3}{\csname a:TocLink\endcsname{1}{x1-110008.3}{QQ2-1-12}{Single span beam with a concentrated force and distributed load using the stiffness method}}{23}\relax
diff --git a/docs/help/theory.aux b/docs/help/theory.aux
index 1db4859..aa9daae 100644
--- a/docs/help/theory.aux
+++ b/docs/help/theory.aux
@@ -6,15 +6,50 @@
\newlabel{Eq:3}{{\rEfLiNK{x1-3001r3}{3}}{\rEfLiNK{x1-3001r3}{7}}}
\newlabel{Eq:4}{{\rEfLiNK{x1-3002r4}{4}}{\rEfLiNK{x1-3002r4}{8}}}
\newlabel{Eq:5}{{\rEfLiNK{x1-4001r5}{5}}{\rEfLiNK{x1-4001r5}{8}}}
-\newlabel{Eq:6}{{\rEfLiNK{x1-4002r6}{6}}{\rEfLiNK{x1-4002r6}{9}}}
+\newlabel{Eq:6}{{\rEfLiNK{x1-4002r6}{6}}{\rEfLiNK{x1-4002r6}{8}}}
\newlabel{Eq:7}{{\rEfLiNK{x1-4003r7}{7}}{\rEfLiNK{x1-4003r7}{9}}}
\newlabel{Eq:7b}{{\rEfLiNK{x1-4004r8}{8}}{\rEfLiNK{x1-4004r8}{9}}}
\newlabel{Eq:8}{{\rEfLiNK{x1-5001r9}{9}}{\rEfLiNK{x1-5001r9}{10}}}
-\newlabel{Eq:9}{{\rEfLiNK{x1-5002r10}{10}}{\rEfLiNK{x1-5002r10}{11}}}
+\newlabel{Eq:9}{{\rEfLiNK{x1-5002r10}{10}}{\rEfLiNK{x1-5002r10}{10}}}
\newlabel{Eq:10}{{\rEfLiNK{x1-5003r11}{11}}{\rEfLiNK{x1-5003r11}{11}}}
-\newlabel{Eq:11}{{\rEfLiNK{x1-6001r12}{12}}{\rEfLiNK{x1-6001r12}{12}}}
+\newlabel{Eq:11}{{\rEfLiNK{x1-6001r12}{12}}{\rEfLiNK{x1-6001r12}{11}}}
\newlabel{Eq:12}{{\rEfLiNK{x1-6002r13}{13}}{\rEfLiNK{x1-6002r13}{12}}}
-\newlabel{Eq:13}{{\rEfLiNK{x1-7001r14}{14}}{\rEfLiNK{x1-7001r14}{13}}}
+\newlabel{Eq:13}{{\rEfLiNK{x1-7001r14}{14}}{\rEfLiNK{x1-7001r14}{12}}}
\newlabel{Eq:14}{{\rEfLiNK{x1-7002r15}{15}}{\rEfLiNK{x1-7002r15}{13}}}
-\newlabel{Eq:15}{{\rEfLiNK{x1-7003r16}{16}}{\rEfLiNK{x1-7003r16}{14}}}
-\newlabel{Eq:16}{{\rEfLiNK{x1-7004r17}{17}}{\rEfLiNK{x1-7004r17}{14}}}
+\newlabel{Eq:15}{{\rEfLiNK{x1-7003r16}{16}}{\rEfLiNK{x1-7003r16}{13}}}
+\newlabel{Eq:16}{{\rEfLiNK{x1-7004r17}{17}}{\rEfLiNK{x1-7004r17}{13}}}
+\newlabel{A1}{{\rEfLiNK{x1-9001r18}{18}}{\rEfLiNK{x1-9001r18}{14}}}
+\newlabel{A2}{{\rEfLiNK{x1-9002r19}{19}}{\rEfLiNK{x1-9002r19}{14}}}
+\newlabel{A3}{{\rEfLiNK{x1-9003r20}{20}}{\rEfLiNK{x1-9003r20}{15}}}
+\newlabel{A4}{{\rEfLiNK{x1-9004r21}{21}}{\rEfLiNK{x1-9004r21}{15}}}
+\newlabel{A5}{{\rEfLiNK{x1-9005r22}{22}}{\rEfLiNK{x1-9005r22}{16}}}
+\newlabel{A6}{{\rEfLiNK{x1-9006r23}{23}}{\rEfLiNK{x1-9006r23}{16}}}
+\newlabel{A7}{{\rEfLiNK{x1-9007r24}{24}}{\rEfLiNK{x1-9007r24}{16}}}
+\newlabel{A8}{{\rEfLiNK{x1-9008r25}{25}}{\rEfLiNK{x1-9008r25}{17}}}
+\newlabel{A9}{{\rEfLiNK{x1-9009r26}{26}}{\rEfLiNK{x1-9009r26}{17}}}
+\newlabel{A10}{{\rEfLiNK{x1-9010r27}{27}}{\rEfLiNK{x1-9010r27}{18}}}
+\newlabel{A11}{{\rEfLiNK{x1-9011r28}{28}}{\rEfLiNK{x1-9011r28}{18}}}
+\newlabel{A12}{{\rEfLiNK{x1-9012r29}{29}}{\rEfLiNK{x1-9012r29}{18}}}
+\newlabel{A13}{{\rEfLiNK{x1-9013r30}{30}}{\rEfLiNK{x1-9013r30}{19}}}
+\newlabel{A14}{{\rEfLiNK{x1-9014r31}{31}}{\rEfLiNK{x1-9014r31}{19}}}
+\newlabel{A15}{{\rEfLiNK{x1-9015r32}{32}}{\rEfLiNK{x1-9015r32}{19}}}
+\newlabel{B1}{{\rEfLiNK{x1-10001r33}{33}}{\rEfLiNK{x1-10001r33}{20}}}
+\newlabel{B2}{{\rEfLiNK{x1-10002r34}{34}}{\rEfLiNK{x1-10002r34}{20}}}
+\newlabel{B3}{{\rEfLiNK{x1-10003r35}{35}}{\rEfLiNK{x1-10003r35}{21}}}
+\newlabel{B4}{{\rEfLiNK{x1-10004r36}{36}}{\rEfLiNK{x1-10004r36}{21}}}
+\newlabel{B5}{{\rEfLiNK{x1-10005r37}{37}}{\rEfLiNK{x1-10005r37}{21}}}
+\newlabel{B6}{{\rEfLiNK{x1-10006r38}{38}}{\rEfLiNK{x1-10006r38}{22}}}
+\newlabel{B7}{{\rEfLiNK{x1-10007r39}{39}}{\rEfLiNK{x1-10007r39}{22}}}
+\newlabel{B8}{{\rEfLiNK{x1-10008r40}{40}}{\rEfLiNK{x1-10008r40}{22}}}
+\newlabel{B9}{{\rEfLiNK{x1-10009r41}{41}}{\rEfLiNK{x1-10009r41}{23}}}
+\newlabel{B10}{{\rEfLiNK{x1-10010r42}{42}}{\rEfLiNK{x1-10010r42}{23}}}
+\newlabel{C1}{{\rEfLiNK{x1-11001r43}{43}}{\rEfLiNK{x1-11001r43}{24}}}
+\newlabel{C2}{{\rEfLiNK{x1-11002r44}{44}}{\rEfLiNK{x1-11002r44}{24}}}
+\newlabel{C3}{{\rEfLiNK{x1-11003r45}{45}}{\rEfLiNK{x1-11003r45}{24}}}
+\newlabel{C4}{{\rEfLiNK{x1-11004r46}{46}}{\rEfLiNK{x1-11004r46}{25}}}
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diff --git a/docs/help/theory.dvi b/docs/help/theory.dvi
index 47f3439763d59939aa45e0db2835b59323f4c5e1..122c94ca2b1369b893f36c6f2396d8188f74bcfa 100644
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zODOX7)Hly^sBaR+g~xBpHtDY}iEBernoulli-Euler beam theory
1 Introduction
-
+2 Kinematics
-
-
(1) (1)
+
-
-
(2) (2)
+3 Constitutive relations
-
-
(3) (3)
+
-
(4) (4)
+4 Stress resultants
-
-
(5) (5)
+
-
-
(6) (6)
+
+
-
(7) (7)
+
-
-
(8) (8)
+4 ′′
(x), characterizes the deformation (curvature) of
the beam.
-5 Equilibrium
-
-
(9) (9)
+
-
-
(10) (10)
+5 statically indeterminate. Solving these equations for the
latter requires consideration of the kinematic relation (7) and respective
+
boundary conditions.
-
Equations ( Equations (9) and (10) may be combined into one equation as
-
@@ -253,17 +231,16 @@ 5 | (11) |
+" class="math-display" >
Equation (11) replaces both equilibrium equations (9) and (10). -
-
+
The governing equation is obtained by assuming the displacement function, +
The governing equation is obtained by assuming the displacement function, v(x), as the primary unknown and expressing 6 11) using (7) to obtain - -
| (12) |
+src="theory11x.png" alt="( ) + EI (x)v′′(x )′′ + w (x ) = 0 +" class="math-display" >
This equation is known as the governing equation of the Bernoulli-Euler beam. -
If the beam possesses a constant cross section and is made of one material, + +
If the beam possesses a constant cross section and is made of one material, then EI(x) = EI = const. and (12) simplifies to -
| (13) |
+src="theory12x.png" alt=" ′′′′ +EIv (x)+ w(x) = 0 +" class="math-display" >
Equation (13) is what is implemented in this program. -
-
+
Solving ( Solving (13) and applying suitable boundary conditions yields the displacement
function, v(7 θ(x), is obtained through differentiation
as
-
| (14) |
+" class="math-display" >
It is positive if the cross section rotates counter-clockwise during deformation. -
The moment follows from ( The moment follows from (7) as
-
| (15) |
+" class="math-display" >
The transverse shear force follows from (11) as -
-
| (16) |
+src="theory15x.png" alt="V (x ) = M ′(x) = (EI (x)v′′(x))′ +" class="math-display" >
or, for constant EI, simplifies to -
| (17) |
-
+ +" class="math-display" >+
+
+
Both bending stiffness, EI, and distributed load, w(x) = w0, are constant over +the length of the beam. Thus, (13) simplifies to +
+ | (18) |
+
+ | (19) |
+
+ | (20) |
+
+ | (21) |
+
+ | (22) |
+
+ | (23) |
+
+ | (24) |
+Pinned on both ends yields the boundary conditions +
+
+ | (25) |
+
+ | (26) |
+
+ | (27) |
+
+ | (28) |
+
+ | (29) |
+
+
+ | (30) |
+Shear vanishes at x = ℓ and, thus, +
+ | (31) |
+By symmetry, rotation vanishes at x = ℓ and, thus, +
+ | (32) |
+ +
+
+ | (33) |
+
+ | (34) |
+
+ | (35) |
+
+ | (36) |
+
+ | (37) |
+
+
+ | (38) |
+
+ | (39) |
+
+ | (40) |
+ +
+ | (41) |
+
+ | (42) |
+
+
+
+ | (43) |
+
+ | (44) |
+
+ | (45) |
+ +
+ | (46) |
+
+ | (47) |
+
+ | (48) |
+
+ | (49) |
+
+ | (50) |
+
+ | (51) |
+
+ | (52) |
+
+
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