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Thursday, March 23, 2017

Different types of Loads and Forces functioning on Retaining Wall

Retaining wall design will contain any or all of loads and forces which are briefly described in the following sections:
1. Lateral earth pressure
2. Surcharge loads
3. Axial loads
4. Wind on projecting stem
5. Impact forces
6. Seismic earth pressure
7. Seismic wall self-weight forces
1. Lateral Earth Pressure Functioning on Retaining Wall
The primary objective of developing a retaining wall is to hold the soil. For this reason, soil lateral earth pressure is a vital factor in the design. Among various theories, sliding soil wedge theory is mostly recognized for measuring the lateral earth pressure.
The wedge theory implies that a triangular wedge of soil will fall down if retaining wall is disconnected unexpectedly and the wall has to withstand this wedge soil. From the Figure 1, we can view free body lateral forces performing on retaining walls.
Different types of Loads and Forces functioning on Retaining Wall
Coulomb and Rankine equations belong to most vital formulas which are used to compute lateral earth pressure:
The Coulomb method of Lateral Earth Pressure Calculation
This equation considers backfill slope, friction angle at wall face, rupture plan angle, and internal friction angle etc.
Different types of Loads and Forces functioning on Retaining Wall
Ka : coefficient of active pressure
Angle of internal friction: Angle of internal friction
Angle of backfill slope: Angle of backfill slope
Angle of friction among soil and wall: Angle of friction among soil and wall (2?3Angle of internal friction to 1?2Angle of internal friction is supposed)
Slope angle of the wall: Slope angle of the wall that is calculated from horizontal (same as 90 degree for vertical wall)
Besides, concerning flat level backfill soil, observing zero friction at soil-wall interface, and soil-sidewall is vertical, the coulomb equation is contracted to the following:
Different types of Loads and Forces functioning on Retaining Wall
To read the complete article, go through the following link.
Published By
Rajib Dey

Wednesday, March 22, 2017

Concept of Stress and Strain Curve/Diagram

This construction video tutorial will introduce you to the stress and strain curve/diagram for steel structures.
Definition of stress
When an applied force creates alteration in the dimension of the material, then the material is supposed to be in the state of stress. The stress can be detected by dividing the applied force (F) by the cross sectional area (A).
Definition of strain
When the dimension is altered in regard to the original dimension because of stress, it is called as strain. It is described with the symbol epsilon.
ε = x/ L
For a shear force, strain is stated with γ (gamma)
Stress strain curve belongs to a behavior of material when it has to withstand load. If a ductile material like mild steel has to pass through the tensile test, then it moves through different phases prior to fracture.
These phases are given below :-
1. Proportional Limit
2. Elastic Limit
3. Yield Point
4. Ultimate Stress Point
5. Breaking Point
The stress-strain diagram varies in form for different materials.
To acquire stress-strain diagrams, a graph or curve is drawn from the data that has been found in a tensile test. The modifications occurred in length can be detected and recorded through various strain measuring devices.

Concept of Stress and Strain Curve/Diagram

Published By
Rajib Dey

Tuesday, March 21, 2017

Building Construction Illustrated, 5th Edition – An exclusive e-book for construction professionals

Francis D. K. Ching, the well-known Professor Emeritus of Architecture at the University of Washington in Seattle, has written an exclusive book alias Building Construction Illustrated, 5th Edition. This construction book is available in paperback and ebook.

The book provides useful guidance to the fundamental of building construction supported with a 3D digital building model for conversational learning.
Features comprise of a 3D model that demonstrates how building components are originated collectively in a final project.
• There are some evident and precise drawings which show the cutting-edge in construction processes and materials
• Addition of up-to-the-minute information on sustainability, consolidation of building systems, and application of new materials
• Inclusion of archetypal drawings which provide perfect motivation for designers and drafters
• Sheds light on the 2012 International Building Codes and 2012 LEED system
In order to purchase the book, click on the following link
Building Construction Illustrated, 5th Edition – An exclusive e-book for construction professionals

Published By
Rajib Dey

Monday, March 20, 2017

How bridge works to sustain various loads

This construction article focuses on uses and types of bridges.
How bridges balance forces
Things are moved through forces, but they also retain them stagnant. A bridge remains stand steels as all the forces operating on it are correctly in balance. In a nutshell, bridge designers can be described as force balancers.
A bridge extents over a river, valley, sea, or road. There is no direct support under the enormous deck (the primary horizontal platform) of a bridge. If the bridge is lengthier, it becomes heavy and bears lots of weight. So, the chance for collapsing is increased. Bridges can sometime collapse, but most sustain securely for a prolonged period as it cautiously balance two primary types of forces known as compression (a pushing or compressing force, operating internal) and tension (a pulling or stretching force, operating external), by dispersing the load toward abutments (the supports at each side) and piers (one or more supports in the middle). There exist different types of bridges, substantially all of them function by balancing compressive forces in some areas with tensile forces somewhere else, so there does not exist universal force to induce motion and provide damage.
Carrying loads
At the time of unloading, a bridge has to provide support to its own weight (the dead load), therefore the tension and compression in its structure become really static forces (ones that don't give rise to movement) that is adjusted slightly from hour to hour or day to day. Though, by characterization bridges bear fluctuating amounts of weight (the live load) from things like railroad trains, cars, or people, which can significantly raise the ordinary tensile or compressive forces. Rail bridges, as for instance, bend and flex each time when an overweight train passes over them and then "relax" over again once the load has elapsed.
To read the complete article, go through the following link.
How bridge works

Published By
Rajib Dey

Saturday, March 18, 2017

Some useful construction tips to compute the sliding safety factor for cantilever retaining walls

This construction article is extracted from an exclusive article written by Javier Encinas, the renowned professional engineer Javier Encinas.
The article sheds light on how to compute the sliding safety factor for concrete or masonry cantilever retaining walls.
Retaining walls are specifically created to encircle soils among two dissimilar elevations. So, they have to primarily withstand the lateral pressures from the retained soil as well as any other surcharge. Cantilever walls are susceptible to sliding issues, specifically if constructed on inferior quality soils.
Cantilever retaining wall pressures
Pressures functioning on a retaining wall
Besides, to the retained backfill, retaining walls are dependent on surcharge loads at the top of retained mass. A surcharge belongs to a strip load. If the stem expands beyond backfill, the retaining wall has to withstand wind load. If the retaining walls are placed in seismic zones, the focus should also be given to seismic pressures.
The load has been used contains a definite effect on the wall. The backfill employs a triangular lateral pressure measured according to the equivalent earth pressure theory. The surcharge creates a constant rectangular pressure on the wall. The seismic pressure is trapezoidal, together with the greater pressure at the top. Due to the actions of these loads, a bearing pressure is created beneath the footing, as well as a passive pressure at the front of the wall.
Method for verifying the sliding failure mode
The wall will be moved to exterior by the horizontal pressures on the backfill side that will have a tendency to slide on its footing. The driving force from the assigned loads should be defied with an opposite friction force at the edge of the footing base and the foundational soil that is formed by the bearing pressure against the base.
Besides, the passive pressure against the front face of the wall and footing should also be taken into consideration. It will never happen that the natural soil will be unaffected throughout the construction, so usually the top portion of the soil cover for the passive force calculation is omitted.
To read the complete article, click on the following link
sliding calculation

Published By
Rajib Dey

Friday, March 17, 2017

Some useful construction tips to draw influence lines for truss members

This construction video is extracted from a lecture delivered by a construction professional. The video focuses on the importance of influence line for effective structural analysis as well as process for drawing influence lines for truss members.

This video exemplifies a truss bridge. The structure is undergoing a moving load. In order to design the structure flawlessly, the outcome of the moving load on each truss member should be determined.

Influence lines play an important role in designing beams and trusses applied in bridges & other structures where loads are transmitted across their span.
The influence lines demonstrate where a load will generate the utmost effect for any of the functions studied.The influence lines demonstrate where a load will generate the utmost effect for any of the functions studied.
The influence lines are applied even if the applied is not a unit load or if numerous loads are applied. To discover the consequence of any non-unit load on a structure, the ordinate results acquired by the influence line are multiplied by the magnitude of the actual load to be applied. The whole influence line can be scaled, or just the highest and smallest effects are accomplished along the line. The scaled highest and smallest belong to the critical magnitudes which should be designed for in the beam or truss.

Published By
Rajib Dey

Thursday, February 23, 2017


Reinforcement detailing of a slab is performed on the basis of its support conditions. Support to slab is generally provided through walls or beams or columns.

A slab is called one way if the supported is provided from two opposite edges. So, the prime load is transmitted onward the spanning direction. Here, the proportion of longer extent to shorter extent is over 2. In one way slab, one side is greater than the other one. In one way slab, the bending occurs mainly in one direction only (spanning direction).

Consequently, the main reinforcement is necessary to withstand the moments produced and designed for the same. The main reinforcement is arranged at the bottom of the slab that is usually described as the tension face.

In one way slab, as one side is larger as compared to the other one, the greatest load is carried by the larger side. To give more support on the larger side, main reinforcement is set perpendicular to that side or parallel to the shorter direction. Distribution steel is arranged in the extended direction that will not be very useful for carrying any load.

In one way slab, the main reinforcement is calculated with a formula (In limit state design) and to obtain the result the comparison is made between the comparing compressive force and tensile forces.

Ast = 0.5 Fck/Fu[1-√1-2.6Mu/Fck.b.d]b.d
and the distribution steel is calculated as

0.15% of Ag, for mild steel.
0.12% of Ag, for tor steel.
Where, Ast denotes Area of the steel in tension.
Fu denotes Ultimate strength of steel.

Mu denotes Ultimate moment of resistance.
b denotes Breadth of the slab section.
d denotes Depth of the slab section.
Ag denotes Gross area of the section.


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Published By
Rajib Dey