How to design a gabion retaining wall with Tekla Tedds

In this construction video tutorial, you will learn how to use Tekla Tedds for making calculations of gabion retaining wall analysis and design with adherence to the Eurocode to verify the strength of a gabion retaining wall from sliding overturning. Besides, it is also possible to find out the maximum and minimum base pressure underneath the wall.

A gabion retaining wall is built up with stacked stone-filled gabions which are attached together with wire. Gabion walls are generally battered (angled back towards the slope), or stepped back with the slope, in spite of stacked vertically. Besides, galvanized steel wire, PVC-coated and stainless steel wire are also utilized. This type of retaining wall is very effective for erosion control applications.

Tekla Tedds is a robust software that can be used to automate your tedious structural calculations. The users can select from one or more of the extensive calculation libraries.

The users will also be able to write their own, and generate professional documentation every time. It is also possible to integrate the structural calculations with 2D frame analysis.

The users can get access to the following extensive library of design modules.

• Loading - Seismic and Wind
• Analysis - Continuous Beams and Rolling Load
• Steel Design - Beams, Torsion, Columns
• Connections - Base Plates and Bolts

Tekla Tedds offer the following benefits :-

a. Get access of an expansive library of structural and civil calculations.
b. Employ a single solution for all common components & materials.
c. Reap benefits from a simple and intuitive interface.
d. Generate apparent calculations which can be simply analyzed.
e. Make comparison among various design options and create modifications instantly.
f. Create consistent documentation.
g. Improve your Quality Assurance processes.
h. Obtain new and improved calculations and code updates regularly.

To get online demonstration of Tekla Tedds, go through the following video tutorial.


Video Source: Tekla Software

~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Raft foundation construction details

This construction article provides the detail construction methods for raft foundation of a building. The raft foundation is conducted for the multistory buildings or building having heavy loads.

Step 1: Initially, the surveyor should begin exaction and as soon as the survey is completed then exaction is carried out to the desired level on the basis of the validated shop drawings.

Throughout excavation, precaution for safety should be undertaken, the entire area should be guarded and everybody should utilize PPE at site.

Step 2: As soon as the final phase of the exaction is completed then the surface should be consolidated with plate compacter as the area is small and it is not difficult to apply the roller compacter. But 95% compaction should be performed with compaction test.

Step 3: After getting the passable results of compaction test, 75mm or 100 mm blinding concrete is arranged. Blinding concrete should be garde 20/20 SRC (Sulphate Resisting concrete).

The blinding concrete facilitates to arrange a solid and flat surface for the reinforcement of raft foundation.

The curing polythene sheets should be arranged instantly after finishing and when the concrete is set, it should be substituted with hessian cloth and should be retained wet unless the surface becomes fully dry.

Once the blinding surface becomes dry, water proofing of surface should be started according to sanctioned specification.

Step 4: Once water proofing is done, perfect planning should be undertaken for the shuttering work, all material should be retained on a plate form and steel bars should be installed with adherence to sanctioned shop drawings of the surrounding. All working space should maintain neat & clean to get rid of accidents at site.

Upon the completion of the reinforcement work, the contractor should sanction it from the supervision consultants for pouring the concrete.



Read more
~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Arka Roy
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Benefits of Parapet Walls

A parapet belongs to a low wall built up over the roofline that normally extents around the boundary of a building. Parapets may be simply aesthetic or largely functional, like hiding mechanical equipment or functioning as a firewall.

The moisture may enter through the top portion of a parapet wall and it creates problems. To get rid of this issue, select a perfect cap.

There are different types of materials like limestone, terra cotta, hard-fired clay, or precast concrete to cap off the wall. These materials contain thermal properties identical to brick and concrete masonry.

Contrarily, metal includes a coefficient of thermal expansion almost three times higher than masonry that produces a considerable amount of differential movement among the parapet cap and the wall underneath. Metal versions should be arranged with firmly sealed slippage joints where the cap section bends.

Caps are available with various shapes, but they should contain pitch, projections (1-in. minimum), and incessant drips. These components safeguard the parapet from pooling water and resist moisture from flowing out of the exterior wall surface.

Most caps are prone to entering of moisture at the head (vertical) joints. In order to reduce penetration at these positions, rake out the mortar head joints, bed joints in the cap to a depth of ½ in., and use elastomeric sealant to fill the joint.

An incessant flashing membrane is to be installed directly underneath the mortar joint under the cap so that the moisture can’t penetrate through the top of the wall. This flashing membrane is built from sheet metal, combination sheet metal/asphaltic, or rubberized asphalt. The flashing has to be arranged entirely through the wall to make a slippage plane among the cap and the wall underneath. The cap should be anchored to the wall underneath.

Different types of stainless steel anchorage systems are applied to fix the coping to the wall. A flexible system should be set up so that the mason can be perfectly arranged with the dowel anchor through the pre-drilled holes in the cap. A considerate amount of mastic should be used to the flashing where anchor punctures may happen.

If the back portion of the parapet is fully uncovered, both exterior wythes should be built up of the same material. Brick situated on the backside of the parapet should be coated with rainproof water repellant.

The bottom flange of the steel beam should be connected with the concrete masonry underneath with a debonded shear anchor. The anchor is mechanically secured to the bottom of the beam at specified spacings that is arranged with the head joints in the concrete masonry wythe. A debonded shear anchor protects out-of-plane (but not in-plane) shear forces and allows structural movement of the steel beam (deflection). The anchor should be completely implanted in mortar, inside the head joint of the concrete masonry unit, for this connection to be effective.



Read Continue
~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Some vital tests for checking compressive strength of cement

If water is included in the cement, the compressive strength of the hardened cement is considered as the vital factor. Cement hydrates and exposes cohesion and consistency. It joins all the components like cement, sand, aggregate etc. collectively. The hardiness of cement-based compound like mortar/concrete is based on the type and nature of cement.

Owing to strength, nature of cement, both mortar and concrete contain high strength against compression and less strength against tension. Therefore, testing of cement for compressive strength is very crucial. Cement is examined for compressive strength so that the strength and stability of the structure is retained.

Initial strength gain is affected by high lime or high alumina content. The firmness of cement is also impacted with the degree of burning, the fineness of grinding, and the aeration it obtains once the final grinding is completed.

Under the strength test, cement mortar is applied since neat cement produces shrinkage and cracking and it becomes complicated for testing.

Primarily, cement is recognized with its compressive strength. Cement is designated with its grade like 53 grade, 43 grade, 33 grade of cement. This grade signifies the compressive strength of cement, i.e. 53 grade of cement species that compressive strength of cement cube after 28 days of curing should be 53 N/mm2 (MPa) or 530 kg/cm2.

Compressive Strength Test of Cement according to IS 4031 (Part 6) 1988.

The following equipments are required for conducting the test :

• Compression Testing Machine or Universal Testing Machine.
• Cube Mould: 70.6 mm*70.6 mm*70.6 mm size
• Vibrating Machine
• Weighing Machine
• Gauging Trowel
• Measuring Cylinder
• Tray

Method: Arrangement Of Test Samples

• Testing material is cement, sand and water.
• The necessary material for each cube is as follows:

1. Cement – 200gm,
2. Sand – 600gm,
3. Water quantity (P/4 + 3) % of the total mass of cement and sand. Where P denotes the standard consistency of cement.
• Initially, blend cement and sand in dry condition with a trowel for one minute and then include water and blend unless homogeneous colour is produced.
• The time of mixing should not be under 3 minutes and not in excess of 5 minutes.

Moulding Samples
• Once the blending is completed, mortar is provided in the cube mould. Prior to arrange the mortar, use oil on the inside surface of cube mould.
• To discharge the entrained air and get rid of honeycombing, the mortar should be stimulated 20 times in about 8 s and then consolidated with vibration.
• The vibration period should be 2 minutes at the certain speed of 12 000 ± 400 vibrations per minute.
• Then, the top surface of the cube in the mould should be completed by leveling the surface with the blade of a trowel.

Curing Samples
• Once the vibration is finished, retain the filled moulds in a moist closet or moist room for 24 hours.
• As soon as that period is ended, detach mortar cube from the moulds and instantly immerse in clean, fresh water and put there unless it is removed before testing.
• The cubes should not get dried once they are removed and unless they are tested.

Testing
• The testing is done with compression testing machine or universal testing machine.
• Test 3 cubes for compressive strength for every time period according to detailed specifications. As for instance 3 cubes for 3 days test, 3 cubes for 7 days test and 3 cubes for 28 days test.
• The cubes testing should be performed on their sides. No packing among the cube is allowed and the steel plates of the compression testing machine while testing is going on.
• The load shall be gradually and consistently employed and the rate of loading should remain 35 N/mm2/min.

Points to be considered
• Clean appliances should be applied for the tests.
• Test for temperature and humidity should be carried out at 27 ± 2°C temperature and 65 ± 5 percent of the relative humidity of the laboratory.
• The water in which the cubes are immersed should be changed every 7 days and retained at a temperature of 27 ± 2°C
• While determining the compressive strength, the faulty samples should not be utilized.
• The samples which produce strength differing by above 10 % from the average value of all the test samples.



Read more
~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Different types of rock drilling tools

Drilling alias boring , is easily performed with specialized equipment known as rock drills. The following types of drills are generally found :

a. The hydraulic drills
b. Electric motor drills
c. Pneumatic rock drills

The above types of tools are utilized in different types of projects like soil nailing, micro-pile, mining and tunneling job sites. The hydraulic drills are mostly recognized due to their light weight and capacity to operate on hard rocks devoid of utilizing a large compressor.

Parts of a Rock Drill: All types of rock drills contain a standard design that is basically a combination of exchangeable attachments. A standard rock drill comprises of the following sections:

1. Drill bit: It refers to the tip of the rock drill that initially touches with the ground throughout a boring operation.
2. Drill stem: It stands for the long frame that enters the ground throughout boring whose end houses the drill bit.
3. Drill rod: It belongs to the empty section of the drill stem that attaches the motor of the rig to the drill bit. The drill rod transmits the cutting force to the drill bit to allow the rock drill to enter into the ground.
4. Carbide bits: These belong to special types of drill bits which are found in rotary and percussive drilling containing carbide tungsten coated onto them at an angle.

How Rock Drills Work: All through soil nailing, micropile, mining or tunneling operations, rock drills enter the earth either by rotating or making incessant impact blows.

Rotary drills are activated by cutting and flushing out rock fragments, whereas percussive drilling splits rocks by making impact blows. Some contractors prefer to join both methods which are suitable for operations on medium to hard rocks.

The method of drilling is based on the type of hole a contractor plans to bore into the ground. The two mostly recognized holes are the cored holes and the open holes. Cored holes contain an opening whose diameter is preset beforehand prior to start of an operation. In this case, cored holes need a stem with exterior tubes to rotate the drill bit.

Alternatively, open holes do not contain predetermined diameter. The drill bit enters straight into the ground throughout an operation. The three main types of drill bits generally exist which are used in boring open holes. These range from rock roller bits, wing bits and down-the-hole hammers.

Rock roller bits alias tricone bits, contain teeth-like steel cones. These cones cut and flush rock fragments outsides via the drill rod. Wing bits alias drag bits, are built with carbide tungsten and effective for soft ground surfaces. Air core hammers contain three protruding blades that cut rock throughout an operation and apply compressed air to flush out fragments on the surface.



Read more
~~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~~

Types of Estimate found on various stages of a Project

Estimate is a raw calculation on quantities of various works and their expenses which are made by the experts of the proper field before a project gets complete. Accuracy of an estimate depends on the experience, ability and judgment power of the estimator.

An estimator has to be very careful about the quantity takeoff using the given data such as drawings, specifications and other documents about the project. Besides all of this, every estimate must be prepared with the consideration of other two factors which influence a project namely Direct & Indirect Cost. Direct Cost includes cost of materials, equipment, labor and subcontracted cost; while the Indirect cost includes overheads and contingency.

Types of estimate: There are seven types of estimates which are described below:

1. Approximate estimate: It is also known as budget, preliminary estimate which is prepared in the first stage of a project; this estimation is made to give a clear idea to the client about the amount of cost needed for the project and to get the acceptance from necessary approving bodies or banks to get the loan. So mainly the approximate estimate is calculated with relevant previous experience and the documents like project drawing plans, details about land, electricity & water supply and a full detailed report are necessary to make the estimate. So, Approximate estimate = rate of 1m2

2. Plinth Area estimate: This can be calculated by multiplying the values of length, width and area of plinth. The plinth area is considered as additional plinth area of the building at floor level which can also be known as the roof covered area of a building. The plinth area rate is originated by dividing the total cost of an early constructed building by plinth area of the earlier constructed building.

3. Cubic content estimate: It is done by multiplying the volume of the building by the unit cubic rate got form the earlier estimate.

4. Annual repair estimate and special repair estimate: These kinds of estimates are calculated for managing the constructed element in good condition. Special repair estimate is made in situations where the costs of materials increased when compare to annual repair estimate cost.

5. Revised estimate: This is made when the rate of earlier submitted estimate rises by 5% or more than that. There can be many reasons for the preparation of estimate as per the increase cost of materials while the reason and comparative statement between two estimates can be joined with the revised estimate.

6. Supplementary estimate: It is made when there is an important situation of supplementary work to progress out the original work.

7. Detailed estimate: This type of estimate is made with the help of complete set of contract data and the making of detailed estimate can do under two phrases like work out with quantities of different works and calculate the cost of each work. A detailed estimate must have some documents like report, specifications, drawings/plans, design charts and schedule of rates. Besides these there are many other factors that are needed to consider well in the time of planning the detailed estimate.

Article Source: www.basiccivilengineering.com



~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

A new Roof-Top units is added with previous Steel Roof Structure

A right amount of experience is needed to know the exact problem of existing Steel roof structure before adding a new Roof top unit with it as the work needs experienced methods to do.

Often contractors are asked to calculate a previous steel roof structure to establish if it can support new roof top units or not. Often tenants remodel commercial spaces for their needs and also sometime new air make-up units, exhaust fans and HVAC units need to add.

What is Roof Top Unit: A packaged rooftop unit or RTU is a kind of HVAC system that has all the components needed to supply conditioned air in one brief unit. Packaged rooftop units are naturally found in light and large commercial applications. They are very famous in the construction industry with retail and industrial properties.

The Roof-top Unit or Roof Top Air Handling Unit supplies Heating, Ventilation, and Air Conditioning (HVAC) to the space below. Air duct Smoke Detectors or Duct Detectors can be inside the Roof Top Unit or in the air ducts below it.

In this article we are going to show evaluations of two commercial spaces for new rooftop units; where one space was adding a commercial kitchen and needed new exhaust fans and air make-up unit while the other needed new cooling units to reverse all the extra heat that was coming.

New roof top units can be large and heavy and generally affect the existing roof structure; sp at first the existing roof structure is examined to know the size, space and span of the joists, location of bearing walls and girders and location of previous roof top units. Generally a typical commercial roof structure is constructed with steel bar joists which are mainly tagged by the manufacturer like Vulcraft who keep records of joists’ type to use in the projects. Next all the accurate measurements of the top and bottom flanges, the web members and the length of the joist has taken; besides all this contractors have to observe other parameters to make sure all new and previous load can be transferred to the supporting structure in the right way.

After that the ability of from the manufacturer is determined and/or is modeled as per its section properties which help the contractors to calculate the load carrying capacity of the steel joist. As previous joists don’t have a lot of extra load carrying capacity so they can be strengthened by welding steel rods and plates to the flanges. But it is always best to locate a new unit away from previous units and near the previous bearing wall or girder which will limit the amount of new load on the previous joints. So basically it is mandatory to examine a previous structure to know its strength and capacity and qualifying it accordingly the new one as it creates a good understanding of structural design as well as a wealth of knowledge of building construction.



Read more
~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~