Bending moment calculator

Bending moment plays an important role in designing different structural components.
An online bending moment calculator is now available at http://civilengineer.webinfolist.com/mech/bmcalc.htm

Resultant of Coplanar Concurrent Forces

Coplanar concurrent forces are those which are lying in the same plane and acting at the same point. The forces can be represnted in scalar form (magnitude and angle) or in a cartesian form(components along x, y, z axes alongwith unit vectors).

Scalar Form
To find the resultant of the system of coplanar concurrent forces the following steps should be followed.

1. Resolve all the forces into their rectangular components along x-axis and y-axis.

Note: Component of a force F along x-axis is F cos θ, (where θ is the angle between the force and the positive x-axis), and the component of a force F along y-axis is F sin θ.

2. Take the algebraic sum of the components along x-axis and y-axis

Σ Fx and Σ Fy.

3. Resultant of the force system will be calculated as

Magnitude, R= sqrt{(Fx)(Fx)+(Fy)(Fy)}

Direction, Angle α =Tan(-1){(Σ Fy/Σ Fx )}

Cartesian form
The forces are commonly resprented in the cartesian form with their x, y and z components as;

F=fx i + fy j + fz k

where fx, fy and fz are the components of the force along x, y and z axis and i, j, k are the unit vectors in the direction of x, y,z axis respectively, e.g., F=2 i + 3 j + 4 k

To find the resultant in the cartesian form, follow the following steps.

1. Resultant R=(Σ fx) i + (Σ fy) j + (Σ fz) k
where Σ fx is the algebraic sum of the x-components of all the forces
Σ fy is the algebraic sum of the y-components of all the forces
Σ fz is the algebraic sum of the z-components of all the forces

2. The magnitude and direction of the resultant will be calculatd in the normal way as for any vector.

For more on Engineering Mechanics visit http://civilengineer.webinfolist.com/mechanics.htm
or refer to Engineering Mechanics - Statics (11th Edition) by Hibbeler.

Environmental Challenges for Civil Engineers

Global warming is an important issue with which all engineers and scientist are concerned worldwide. The earth's surface temperature is increasing continuously due to the increase in greenhouse gas concentrations. This is mainly due to human activities as a result of industrial revolution in the last six decades.

The increasing global temperature has some serious effects as it it is expected to cause a rise in sea level (which may remove some areas from the world map), extreme weather conditions, significant changes in rainfall (leading to floods or droughts), increase in desertification etc. It is also expected to effect agricultural output, melting of glaciers (will cause an increase in sea level), extinction of species and increase in diseases.

Kyoto protocol is an attempt to reduce global warming and most governments have signed it but it is still under political manipulations and debate. United states being the largest emittor of greenhouse gases has not ratified Kyoto protocol!!! Intergovernmental Panel on Climate Change is associated with the task of evaluation of risk due to climate change casued by human beings.

Environmental division of Civil Engineering is also very much involved in the process of finding out the solution to global warming. Marching ahead for a better, comfortable and peaceful world for all irrespective of cast, creed or races.
Comments and suggestions are welcome

Precautions during hot-weather concreting

Precautions for hot-weather concreting should be planned when the temperature is expected to reach 30 to 35°C or more. These precautions may have one or more of the following applications:

• cooling of concrete ingredients
• dampening of formwork, reinforcement and subbase
• erection of wind breaks and sunshades to protect exposed concrete surfaces
• cooling of containers, pipelines, chutes, etc during transportation of concrete
• completion of transporting, placing and finishing of concrete as quickly as possible
• use of set-retarding admixtures to control premature stiffening of the fresh mix
• use of some chemicals on the exposed surface of concrete to limit evaporation
• immediatly start curing after final finishing is complete
• moist curing to control concrete temperature
• restricting the placement of concrete during night time when the temperatures are generally lower.