3. 2 Load

i) Loads
This load acting on an area that is too small and can be  said to act at one point as the point x (Figure 3.6). unit = N

ii) A uniformly distributed load
It acts on the whole or part of a long beam with a uniform   way (figure 3.7). units = N / m

 

iii) Non-uniform distributed load

This load is continually changing. Normally the load form a  triangle (Figure3.8). units = N / m

iv) The moment of the coupling
It is the effect of a twisting action imposed on a beam (clockwise direction) will be produced by two forces F acting on the arm. The value of M₁ is (F x d) Nm. While  M₂ is another example of the coupling moments acting   at point x, in an anticlockwise direction

CHAPTER 3: SHEAR FORCE AND BENDING MOMENT

CHAPTER 3: SHEAR FORCE AND BENDING MOMENT

In this chapter, emphasis will be placed on the shear force (V) and bending moment (M) resulting in a beam. Beam was used to describe a bar or rod which carries the load laterally. It is much used in various fields of engineering, especially civil engineering. The study will be conducted on a beam of horizontal loads only, and that act is considered in a vertical plane only.

3.1 A type of beam

               
 i) simply supported beam                  
 This beam is simply supported at both ends A and B (Figure 3.1). RA and RB reaction on the beam at  points   A and B

ii)     Cantilever beam

 The end of the rigid beam is installed so as not allowed to turn (figure3.2). Reaction R and the moment M    results to ensure the beam is in equilibrium.

 iii) The drop beam

One or two sides of the ends hanging down in a state that is part of the beam depending on the outside of the support (figure 3.3).

iv) Continuous beam

It occurs when there are more than two fans are used to support beams (Figure 3.4).

v)  The built-in beam

 It is rigidly mounted on both ends and having reactions RA and RB, and MA and MB (Figure 3.5). The equations of equilibrium are not sufficient to determine the response.

2.5 HEAT STRESS IN SERIES COMPOSITE BARS

2.5    HEAT STRESS  IN SERIES COMPOSITE BARS

... When the temperature is raised, the two bars will expand. Total expansion due to temperature rise are:

... However, this expansion was blocked by both ends rigidly mounted. Compressive force, P will be produced to counter this development. From the force equation, we know the power of one is equal to the force of two equal forces 
   ® P1 = P2 = P
Therefore, the extension is arrested by the force P:      S d_p = d_p1  +  d_p2

... Then finally, the unknown amount of expansion by heat is equal total extension by the force  P:     

       

\ forces resulting in the bar:

2. 6   HEAT STRESS IN PARALLEL COMPOSITE  BARS
... Of the bar consists of different types of materials, expansion and contraction depending on the coefficient of linear expansion, ie if  a2 > a1, the second material should expand more than the material one. Therefore, the material having a greater coefficient of linear expansion will experience compressive stress rather small coefficients will experience tensile stress.

2.1 THERMAL STRESS AND COMPOSITE BAR

2.4  HEAT STRESS

When the temperature of a material change, then the material was changed. Development of materials will occur if the temperature rises, while contraction occurs if the temperature is down. An expansion of the material shrinkage due to temperature @ is proportional to the original length and temperature change itself.          d_t µL_o Dt

... But the expansion is blocked, then the extension is supposed to happen has been detained by the force of the wall. Therefore, we say these forces have arrested elongation wall materials:

... Finally, note that the initial length is equal to the length of the end. Therefore the extension and expansion did not bring any change in shape.

... And note that the stresses inherent in the material either compression or tension is equal to the force per surface area materials.



CHAPTER 2: THERMAL STRESSES AND COMPOSITE BARS

2. 1 BAR COMPOSITE
The definition of the compound bar is a bar made ​​of two or more materials with both mounted rigidly applied so that the burden can be shared and experienced the same extension @ shortening. Bars compound can be categorized into two types, series and parallel bars.



2. 2 SERIES  COMPOSITE BAR 

Two or more bars that are mounted together by a series  (figure 2.1), can not be determined what is going on    in the bar. Therefore, an equation of deformation must be  produced, in addition to the equation the forces involved.

2. 3 PARALLEL COMPOSITE BARS
It's hard to determine what happens in a plural parallel bars   Figure 2.2). However, existing equations can be simplified.

1.6 SAFETYOF FACTOR

                                                                                                                                                      

1.6 FACTORS OF SAFETY

In our daily lives, it is difficult to determine accurately the burden imposed on a structure. It is because there are many obstacles and challenges arising out like wind resistance, water, gravity and so on. So as a safety measure, the designers have agreed to use a safety factor that could have stale security against the value obtained. Safety factor can be defined as the ratio of maximum load with the workload.

... If the load is the reference yield,

                                      

1.5 HOOKE'S LAW AND MODULUS OF ELASTICITY

1.5   HOOKE'S LAW AND MODULUS OF ELASTICITY

We can learn some of the mechanical properties by performing tensile tests using a testing machine that can impose a pure axial load. From these tests, we have some data and data of which are stress and strain occur on the specimen being studied. Examples of stress-strain diagram is as figure 5.3.

In the elastic limit (0-1), the material will return to its original condition after its release. It meets one law called Hooke's Law, which states that stress is proportional to the strain of an elastic material so long as does not exceed the elastic limit. Thus, a constant that can show this Hooke's law, the Young's Modulus (Modulus of Elasticity), where it also is the slope straight line in the elastic limit.

                                         Units for young modulus is Pascal (Pa).

... From the basic equation:

 

Apart from the stress-strain data, several other results can be known from tensile tests carried out, including

From the results obtained, several new properties of materials are available, namely: