Soil mechanics and foundation engineering – An exclusive book for civil engineers

Dr. K. R. Arora, having 25 years of teaching experience, has written an exclusive book alias soil mechanics and foundation engineering. The book is available in PDF version.

The book is specifically designed for the undergraduate students as well as the students appearing for different competitive examinations and AMIE. A huge numbers of charts and tables are provided to make the text informative for practicing engineers.

Soil mechanics and foundation engineering (geotechnical engineering) is a part and parcel of civil engineering that witnesses a significant growth. The book is enriched with the most updated information in the field. The author has accumulated the material from different sources and demonstrated them in the form of a text.

The text is segregated into two parts. The first part sheds light on the basics of soil mechanics. The second part focuses on earth retaining structures and foundation engineering. The subject matter is explained in a rational and organized way.

The book comprises of the syllabi of undergraduate courses in soil mechanics and foundation engineering prescribed by most of Indian Universities and Institutes.

With the use of simple and coherent language, the author tries to narrate the basics for the students. Basic concepts have been emphasized throughout. The special emphasis is given on the complexities faced by the students. The book is supported with the extensive range of descriptive examples to present the application of the theory to field issues. Numerical problems, with answers, are provided for practice.

Some objective type questions are provided at the end of the each chapter.

The text is plentifully exemplified with diagrams and charts. Latest IS codes are abided by, as far as possible. References are provided at the end of each chapter. Both MKS and SI units are applied in this book.

Click on the following link to download the book Soil mechanics and foundation engineering

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Different types of bearings used in bridge structures

Bridge bearings stand for structural equipment or devices which are set up among bridge substructure and superstructure with the purpose of transmitting the functional load together with earthquake loads; wind loads; traffic loads; and superstructure self-weight.

Bridge bearings also allow for relative movements among superstructure and substructure, as for example, rotation movements and translational movements in horizontal and transverse direction.

Bearing is employed in building up the bridge structure. It is categorized as expansion bearings and fixed bearings. The first one allows for both translational and rotational movements while the second one allows for rotational and limited translational movements.

There are several types of bridge bearings which are frequently utilized in bridge construction. The details are given below :-

Various types of bearings for bridges: Sliding bearings, Rocker and pin bearings, Roller bearings, Elastomeric bearings, Curved bearings, Pot bearings, Disk bearings

Sliding Bearings for Bridges: Sliding bearing is made of two metal plates, generally stainless-steel plates, which slide corresponding to each other and therefore allows room for translational movement and lubricating material among them.

A friction force is produced in sliding bearing and it is enforced on substructure, superstructure and sliding bearing itself. So, it is necessary to arrange lubricant like polytetrafluoroethylene (PTFE) to reject generated friction.

As per guidelines by ASSHTO, the bridge span should be less than 15m to use sliding bearing in bridge structures. It is due to sliding bearing is not fully applicable if there is rotation movement in bridge.

While using sliding bearing, this span limitation can be avoided if it is employed in conjunction with other bearing types.

Rocker and Pin Bearings for Bridge Structures: Rocker stands for an expansion bearing that contains curved surface at the bottom. It adjusts translational movement and a pin at the top takes rotation movement into consideration.

Both rocker and pin bearings are vital parts of steel bridge structure. Rocker and pin bearing are taken into account when the bridge movement is suitably known and defined, because such bearings can allow for both translational and rotational movements in one direction only.

These bearings are susceptible to deterioration and corrosion, so inspection and maintenance should be performed on regular basis.

To get further details, go through the following article theconstructor.org

Different types of bearings used in bridge structures

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Guidelines to follow for acceptance criteria for concrete

As per IS 456 : 2000 (C1 15.1), it is known that 28 days compressive strength shall individually be the standard for approval and disapproval of concrete.

But as per IS 456 : 2000 (C1 16), there exist two criterion for acceptance of concrete that range from compressive strength and flexural strength.

Prior to arrange test results for acceptance criteria, it is necessary to examine validation i.e. whether the sample is proper or improper for acceptance criteria.

The test results should be as follow :-

Test results are average of three specimens.

Individual deviation should be under ± 15% of the average.

Suppose M25 grade of concrete is applied in the construction. Let strength of specimen for first one should be 28.5 MPa (Mega Pascal). For the second one, it should be at 26 mega pascal and for third one, it should be 29 mega pascal.

By summing up, we get the average as 27.83 MPa (mega pascal).

If the individual deviation is computed from the average for first specimen, it shall be 2.4%.

For second, it shall be -6.57%

For third, it shall be 4.20%

From the test result, it can be said that the specimens are legitimate for acceptance criteria as the deviation of individual sample does not surpass 15%.

To get more details, go through the following video tutorial.

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RetainWall version 2.60 – A powerful software for designing a concrete or masonry retaining wall

Dhani Irwanto has developed RetainWall. It is an exclusive software that can be used for making the design of a concrete or masonry retaining wall. The wall may preserve soil or other granular material.

It examines the strength of the wall on the basis of the loads and resistances, and leads to bearing pressure, sliding, overturning and rotational stabilities. Loads which operate on the wall may include self weight, soil pressure, water pressure, live and seismic loads.
Resistances may contain base friction and cohesion, passive earth pressure, other structures or a shear key. Load and resistance factor design (LRFD) mode can be employed. If the wall is a reinforced concrete structure, the software can also produce the reinforcement design for any reinforced concrete structure wall. Besides, there is a soil pressure calculator.

This user-friendly application provides on-screen trial-and-error method and instant solution for the design. With it, any designer will be able to design the wall swiftly. Complete outputs are visible on screen or printed.

The software starts it’s operation by clicking on the specified dimensions to produce the initial dimensioning of the wall, earth surface and water levels. After that, it enters material properties of the wall, soil, water and reinforcement bars. Provided external loads contain surcharge load, seismic load as a horizontal seismic coefficient and any concentrated loads implemented on the wall if necessary. Load and resistance factors combinations are easily selected. Results of the wall stability are gained immediately. If satisfactory result is not obtained, then another trial can be produced instantly. You can also choose from options to use or not to use water, seismic or ashear key. The final results can also be printed.

The reinforced concrete design can be made instantly by applying the internal forces of the wall. It only needs bar diameters and spacings of the reinforcements.

RetainWall is compatible with metric, SI and British unit systems.

Given below, some exclusive features of the software :-

  1. Ability to design Load and resistance factors.
    b. Apply load and resistance factors combinations from AASHTO LRFD 2007, ACI 318-08 and IBC 2006.
    c. Load and resistance factors editor to change or generate new combinations
    d. Concrete reinforcement design from ACI 318-08.
    e. Force diagrams (moment, shear and normal) for every combination.
    f. Loads, resistances and reactions diagrams for every combination.
  2. Wall stabilities (bearing, sliding, overturning, rotation) for every combination.
    h. Workout nominal soil bearing resistance by applying theoretical or semi empirical methods.
    i. Ability to select active or at rest soil pressures.
    j. Ability to select elastic (rock) or plastic (soil) bearing pressures.
    k. Ability to enter user’s soil pressure coefficients.
    l. Reinforcement design for upper stem, lower stem, toe and heel.
    m. Unit systems, properties, load and resistance factors, reinforcement design method, and page setup from last editing which turn out to be the default for new design.
    n. Ability to include other loads on wall.
    o. Offer stability resistances from a shear key, toe passive soil pressure, adjacent structure, anchors or piles.
    p. Enable or disable a shear key, water or seismic.
    q. Various types of units of measurements like metric, SI and British unit systems are supported.
    r. Easy, clear, quick and simple software operation.
    s. Help facilities, can be printed to produce manual.

Click on the following link to download a trial version RetainWall version 2.60

RetainWall version 2.60 – A powerful software for designing a concrete or masonry retaining wall

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How concrete strength is impacted with different factors

The strength of concrete is impacted by various factors. The details are given below :-

Concrete porosity: Air and water are the useful substances to fill up voids in concrete. Air voids belong to pores in concrete. When concrete is blended it contains air trapped in the mix. The vibrators are used to clear out the air at the time of pouring walls.

If the concrete is less porous, it’s strength will be increased and calculated with compressive strength. The most crucial source of porosity in concrete refers to the proportion of water to cement in the mix, called the ‘water to cement ratio’.

Factors water/cement ratio: It is described as the mass of water divided by the mass of cement in a mix. As for instance, in a concrete mix if there are 400kg cement and 240litres(=240kg) of water, the water/cement ratio will be 240/400=0.6. The water cement ratio is shortened as ‘w/c ratio’ or just ‘w/c’. In mixes where the w/c is in excess of roughly 0.4, all the cement can, in theory, react with water to develop cement hydration products. If the w/c ratios are greater, it follows that the space occupied by the supplementary water over w/c=0.4 will persist as pore space filled with water, or with air when the concrete becomes dry.

As a result, when the w/c ratio become higher, the porosity of the cement paste in the concrete also upsurges. With the higher porosity, the compressive strength of the concrete will reduce.

Stability of aggregate: It is inevitable that when the aggregate in concrete is feeble, the concrete also becomes feeble. Rocks like chalk that contain low intrinsic strength, are not appropriate to be utilized as aggregate.

Aggregate-paste bond: The strength of the bond among the paste and the aggregate is vital. When no bond exists, the aggregate practically reproduces a void and the strength of concrete is decreased.

Cement-related parameters: Various parameters pertaining to the formation of the individual cement minerals and their ratios in the cement can impact the rate of strength growth and the final strengths gained.

To get more information, click on the following link www.onlinecivilforum.com

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Some newest technology to make construction process smarter

Some advanced technologies have emerged in materials science which can transform the construction industry to the next level.

As for instance, ordinary concrete is employed for different types of building applications ranging from foundations to flat surfaces. But, cracking may frequently occur for this type of concrete. If the cracking is not repaired, water can penetrate on its surface.

The problem can be resolved with a new self-healing concrete that employs bacteria to seal cracks devoid of any interference in the works. A permeable concrete that facilitates the water to gutter through it instead of pool on it is also being developed.

Other new materials are still in the testing phase. As for example, a transparent aluminum that provides the pleasing visuals of glass but the strength and longevity of metal. Transparent metal technology is also very useful for generating transparent solar panels for sustainable energy devoid of large, unappealing black rectangles on the roof.

3D printing technology is also gaining popularity among housing and construction sectors to fulfill the requirements for reasonable housing. With this technology, it is possible to 3D print a house in about a day at a lower cost as compared to conventional construction process.

Augmented reality, or AR, will play a significant role in construction. Contradictory to VR, or virtual reality, in which a person’s total field of vision is substituted with a rendered environment, AR arranges images over what’s actually come into reality.

In construction, an AR wearable will show the exact amounts to a 3D blueprint to workers as they’re on the job. The latest smart safety goggles like Google Glass, or smart helmets with a combination visor-screen are emerged in the market to make construction process superior.

Now-a-days, the drones are extensively used for surveying purposes, particularly for larger commercial projects on previously undeveloped land. With drones, it becomes easier to obtain full information on a job site rapidly efficiently.

The industry will continue to expand and advance and more improvements will occur in wearables and robotics which will provide a great impact in construction sectors.

Article Source: thenextweb.com

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How to layout columns for a residence on the basis of thumb rules

In order to generate a column layout concerning a building, the following three crucial thumb rules are necessary:

  1. Size of the Columns 2. Distance between the columns 3. Alignment of Columns

Here, you will learn how the column layout of a residence is accomplished on the basis of the aforesaid three thumb rules.
Here, you will learn how the column layout of a residence is accomplished on the basis of the aforesaid three thumb rules.

Column Layout for a residence

The residential villa is built up with 1 and half floors. In the beginning, the column size 9″x12″ is utilized together with the M15 grade of concrete. To save money, the builder usually forms the columns smaller in size.

Therefore, the columns in the Floor plans remain 9″x9″ in size. The Engineer verifies that M20 grade of concrete must have been employed for Columns.

Thumb rule no1:

Size of the Columns

The size of the columns should be 9″x9″ together with the utilization of M20 grade of concrete.

Thumb rule no.2:
Space among the columns:
The space among the columns should not surpass 4.5m.

Thumb rule no.3:
Alignment of Columns
The Columns should be provided on an iron grid pattern. Therefore, no zigzag walls and zigzag beams exist which minimize complexities in the structure.

Article Source : www.civilprojectsonline.com

How to layout columns for a residence on the basis of thumb rules

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Details of Punching Shear in slabs and foundations

Definition of Punching Shear?
The punching shear refers to a failure system that occurs in structural members like slabs and foundation with presence of shear under the action of concentrated loads.

The action of concentrated loads remains on a minor area in the structural members. Normally, this reaction is the one from the column that behaves against the slab.

The punching shear failure mechanism can be applied in normal floor slabs, flat slabs, and in the foundation slabs underneath the column.

Punching Shear in Reinforced Concrete Slabs: The Punching shear in reinforced concrete slabs is treated as a 2D analog of the shear detected in beams. Due to unforeseen crack, this type of failure happens. It becomes difficult to control this crack by making use of main reinforcement.

Therefore, the ultimate load capacity of the structure is decreased underneath the flexural capacity with the action of shear. The punching shear is not so important with regards to beam shear.

In slabs, the punching shear happens if there are high values of concentrated loads for slabs. These load ranges from the wheel loads on the bridge slabs or the loads from over floors on the columns that support the slab floors.

Calculations in Punching Shear: If it is required to compute punching shear for the design, it is dependent on the punching shear force that is punching against the density of the slab or foundation. It can occur only if shear remains separately in the system. It becomes impossible, if any form of moment is in the pedestal or the column.

The Maximum Punching Shear Stress is obtained on the basis of the punching shear failure cone and the applied values of shear and moments. The ‘d’ denotes the effective depth of the slab. The punching shear perimeter is developed at a gapping of d/2 from the edges of the column or the pedestal. In the example given in fig 1, Dped stands for the depth of the pedestal.

1. Proper examinations should be done to ensure that the concrete is very durable.
2. If there is not sufficient strength for the concrete, verify whether the amount of supplied reinforcement is proper.
3. If it is improper, it will be better to adjust the form of the structure.

The form of the structure can be adjusted in the following ways:

1. Raise the depth of the slab
2. Expand the column size
3. Assimilation of drop panels
4. Creation of Flared column heads
5. Other foreign codes are recommended to practice other liberal designs

Different failure zones are described in the example given in figure-2 that is based together with the area where the reinforcement should be arranged. Normally vertical and traverse failure lines can be provided. It becomes difficult to identify where the failure can take place. Therefore, each prospective failure plane should have been reinforced.

Details of Punching Shear in slabs and foundations

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KaderColumn – A useful construction program for column analysis

KaderColumn is a powerful construction program that is created for reinforced concrete tied short columns.

It can be used to create the designs of columns based on up to eleven cases of loading comprising of axial load and bending moment implemented about the maximum principle axis.

The program allows to build up the column strength interaction diagram (Bending moment-Axial load curve) out of the input data of the cross-section and verify whether all input cases of loading are situated inside the design curve. If the input data of the cross-section is insufficient, the program enhances them to commence from the Min. Roh to the cross-sectional dimensions unless all input cases of loading remain inside the design curve. The program provides proposition for setting ties properly and draws them.

Features:

  • It is very user-friendly and short.
    • It computes and draws the column strength interaction diagram toward a reinforced concrete tied short column having a rectangular (containing rebars at two sides only or at all four sides), square or circular section and depending on axial load and bending moment around the max. principle axis of its cross-section.

 

  • Up to eleven cases of loads (axial load and bending moment) are permissible. The program examines all these cases which should remain inside the column interaction diagram.
    • It designs the section and draws by organizing ties in an efficient manner.
    • The user will be capable of rectifying the section dimensions, the min. and max. ratio of reinforcement and some other parameters for obtaining the rational section from his point of view.
  • The user will be able to save and open the input data file that is already saved by the program.
    • The program employs the ultimate strength method for design and abides by the exact ACI 318-02 Code requirements.

To download this construction program, visit the developer’s website www.cadkad.com

KaderColumn – A useful construction program for column analysis

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Some useful tips to read civil engineering drawings efficiently

This construction video tutorial sifts through the process for evaluating engineering drawing easily.

In this video, some crucial topics like grid lines in civil engineering, problems found in the drawing, are explained briefly.

A civil drawing contains a series of various types of site drawings. It is a type of technical drawing that provides information on utility, grading and drainage, site improvements, and landscaping plans as well as other site details. The objective of these drawings is to provide a clear conception of all things in a construction site to a civil engineer. In these drawings the site layout plan and floor plans are set up.

Civil drafters arrange the drawings, topographical and relief maps which are applied in leading construction or civil engineering projects like highways, bridges, pipelines, flood control projects, and water and sewage systems.

In the drawing, there are Grid Lines specified with dimensions n. The grid lines facilitate references to be created on the basis of the position/location of different constituents in the project. The Main Contractor will then employ a license surveyor to organize the grid lines on site.

In the video, a sample drawing is considered. There are 8 columns in this drawing with the dimension 29.5” x 19.5”. Here the header lines will demonstrate the center line of the column.

To learn the complete process, watch the following video tutorial

Some useful tips to read civil engineering drawings efficiently

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Arka Roy
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