Unit 3 | unit 3 construction methods basics

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CEM

Unit - 3

Construction Methods basics

Q1) Explain the steps involved in construction method?

A1) The basic steps involved in a building project are briefly explained.

Planning

Permits

Preparation of Construction Site

Foundation Construction

Superstructure Construction

Punch Lists

Building Warranty Period

Planning:

The planning in building construction involves three major steps:

Developing the Building Plan

Analyzing the Finance

Selecting the Construction Team

Once the site where the building project is indented to construct is chosen, the expertise of engineers and architects are taken to develop the site and the building plan.

Sometimes, an appropriate site is selected after the building layout is prepared. The building plan is developed based on the owner’s requirements and budget.

Once the plan is in hand, the finance and total cost is estimated. The structural design details, the material estimates are prepared which help to derive project cost estimate. The cost calculated include:

The material cost

The construction cost

The labor cost

Miscellaneous cost

Based on the estimated cost, either a bidding process is performed or the project to handover to a known contractor. The contractor and the owner must agree to contract based on which the project is implemented. The contract mentions the completion period and necessary guides, exclusions to remove claims.

Permits and Insurance in Building Construction:

Before starting a building construction, the owner must make sure that one has necessary permits taken to start the construction. Permits and insurance are obtained from different sources in cities and states.

A construction work conducted without permits results in project delay or project demolition or huge fines. Possessing insurance for the required parties helps to save the owner and the contractor.

Site Preparation:

From here, the actual construction process starts. Based on the site and building plan, necessary excavations, leveling, and filling can be undergone to prepare the site. The necessary excavation for utilities, power, water and sanitation lines, and temporary storage facilities are prepared. Mostly the works needed to set up the utilities are prepared. This is followed by an inspection from the government officials.

Inspections are performed at different stages on structural, building codes, the utilities, HVAC, electrical works etc. After the completion of the whole project, a final inspection is performed.

Foundation / Substructure Construction:

Building structures are generally constructed on concrete foundations. Based on the soil type and water table level of the area, the foundation chosen can vary. If necessary, soil testing is performed to check the bearing capacity. Shallow foundations are required for low-rise building. For high-rise building, pile foundation is employed.

Once the foundation is selected, the soil is excavated to construct the foundation. It is performed based on the foundation layout. Formworks are placed in the foundation trenches and reinforcement is placed based on the foundation detailing design prepared in the planning stage. The reinforcement works performed by the contractor is periodically checked by the engineer in charge. The concrete mix of the required proportion is poured to formwork and is cured to form the finished foundation.

Superstructure Construction:

The superstructures constructed once the substructure is complete. Generally, a framed structured is developed which is later finished with masonry walls. Adequate windows and exterior doors are placed based on the building plan. Other works coming under this section is:

Construction of roofs or siding

Installation of heating, ventilation and air conditioning

Providing adequate electric and water lines connection line.

Provide insulation works as required to protect from lighting

Provision of waterproofing to the walls.

Plastering and finishing the walls and surfaces

Flooring works

Exterior and Interior Painting

Punch List:

Once the project is complete, the contractor inspects the whole work one by one and make a punch list.

Those structural units or areas that were not constructed properly or are below the quality level is listed in the punch list. This is later corrected by the contractor in charge.

Warranty Period:

Once the project is complete and handovered to the owner, the contractor specifies a warranty period.

Within this period, any defects found in building constructed must be fixed and replaced by the contractor in charge.

The warranty for materials and appliances are obtained from manufacturers and suppliers.

Q2) What are Shallow foundations?

A2)

Foundations provided immediately beneath the lowest part of the structure, near to the ground level are known as shallow foundations.

Such foundations are mostly placed on the first hard and firm strata available below the ground level.

Shallow foundations are further classified into the following types:

Spread footing or open trench foundations

Grillage foundations

Raft foundations

Stepped foundations

Inverted arch foundations

Q3) Explain the method of construction of Raft foundation?

A3) Method of construction of Raft Foundation is as follows:

In Raft Foundation construction the whole area is dug out to the specified depth and 30 cm more wide than the area to be covered.

The bed is compacted and sprinkled over with water.

Then a layer of lime concrete or lean concrete (1: 8: 16) is laid to a suitable thickness to act as a bottom cover.

After this, the reinforcement is laid. The reinforcement consists of closely spaced bars placed at right angles to one another.

Then the cement concrete (1: 2: 4) is laid and compacted to the required thickness.

The concrete slab so laid is then properly cured

When loads are excessive, thick concrete beams running under the columns can also be constructed.

Q4) Explain Inverted arch foundation?

A4)

The foundation consisting of inverted arches between the piers is known as inverted arch foundation.

In this type of foundation, the load from the piers is transferred to the soil by constructing arches in inverted position at their base.

The rise of the inverted arches is about one - fifth to one - tenth of the span and they are usually built-in half-brick rings.

The position of arches may be either along the row of piers or across the row of piers in both the directions depending upon the nature of soil and the type of land to be taken by them.

This of foundation is not commonly used for buildings, but it is quite suitable for other structures like bridges, reservoirs, tanks, supports for drainage lines etc.

Q5) Explain about Deep Foundation?

A5)

The foundation constructed sufficiently below ground level with some artificial arrangements such as piles, wells etc, at their base are called deep foundations. Deep foundation is further classified into the following types;

Pile foundation

Well foundation

Caisson foundation

Pile foundation: A foundation (spread footing or grillage) supported on piles is called a pile foundation. A pile foundation usually consists of a base of spread footing or grillage supported by piles at their bottom. Piles distribute the load of structure to the soil in contact either by friction alone or by friction combined with bearing at their ends.

Method of construction:

For constructing this type of foundation:

Excavation is done to the required depth.

The bottom of the excavation is leveled and compacted

Then the foundation concrete is laid to the required thickness and finished according to the layout of the arches to be constructed under the piers.

The arch rings, usually half brick thick, are then built-in cement mortar and piers are constructed.

The end piers should be designed and constructed to take the outward thrust caused by arch action.

Q6) What is Traditional Stick Framing?

A6)

This process involves a building system in which workers will assemble the main skeleton of your home. The construction system actually begins when skeleton items including wall studs, ceiling joists, roof trusses, rafters and then all flooring systems are installed. These items will be installed step-by-step and then eventually build a platform for the entire home.

Traditional stick framing new construction methods

Traditional stick framing processes start with the base floor and then adds the second story eventually adding in the roof framing. A number of smaller homes have prebuilt wall panels and wood frame structures in the home that can have items like electrical work/plumbing and more placed into the framing as it gets built up. Following the process of inspection inside the walls, they are usually then covered with drywall and the exterior of the home is then coated with stucco, bricks, or siding to protect it from the elements.

Traditional stick framing is a tested and well-used method. It has been used throughout North America over the decades. New-home construction with traditional stick framing is a time-tested method now.

Q7) Explain about Modular homes?

A7)

Modular homes continue to use the same type of method for conventional stick framing but they are built-in off-site conditions.

This can often lead to a home that can be built much more efficiently and then hold its value well. Modules are built entirely in a factory and then assembled on the job site.

They get moved into a place with a crane and they are constructed in some of the same measures that a traditional stick framing method is used.

The only opposing change with traditional stick framing homes and modular homes is that these homes are assembled in small modules and then trucked to the site.

Modular homes in California - US

Builders will take modular homes and knit the various modules together to create a custom-built home that follows extremely complex designs. Popular architectural features can be added into modules to produce almost any type of home.

Q8) What is Light Gauge Steel?

A8)

Light gauge steel is a process that involves building in a similar way as traditional stick framing but with a light difference. Instead of the wooden design of the stick-built home, each of the components is instead made out of metal.

The big advantage here is that any of this deal will not rot, shrink or experience damage from termites.

Steel can last longer than any type of wood frame and there is less worry for things like drywall cracks, warping or shrinking.

Light gauge steel

Light gauge steel designs are often a bit more expensive for a build but they can often be beneficial for adding rigidity to the home as well as a longer lifespan for any type of property.

Light gauge steel is a common tool for many types of commercial buildings and it’s starting to make its way into many residential buildings as well.

Steel studs do pose a number of challenges for plumbers and electricians. The overall cost of steel also fluctuates far more than other building materials in the market which can lead to costs going up substantially.

Q9) Explain about Structural insulated panels?

A9)

A structural insulated panel is otherwise called SIP. This solution is a small sandwich of rigid foam installations that are placed between an oriented strand board. This can create the structural panel that makes up the main element of a home.

Structural insulated panels

SIPs often come with door openings and precut windows and they are usually constructed with areas for electrical wiring. These building methods are common for use in producing ceilings and walls. Specifically trained crews are required to assemble them on the job site.

These types of building processes are the most common for producing traditional timber frame, post-and-beam structures as well as self-supporting homes. SIP homes are often designed with improved insulation and they are built to be draft-free. This can also ensure that she save money on the cost of their electricity bills and the labor on the home as well. Because the materials take far less time and labor to assemble and the insulation is already in place, this is an option that is less expensive for the future of the building.

Q10) Explain Slip forming for tall structures?

A10)

Slip forming, continuous pouring, continuous forming or slip forming is a construction technique during which concrete is poured into a continuously moving form.

Slip making is used for tall constructions as well as horizontal constructions such as roadways.

Slip forming allows continuous, non-interruption, cast-in-place flawless concrete structures with superior efficiency characteristics to piecewise construction using discrete form components.

Sheathing or vertical forms are the components of slip form Vertical forms can be wood staves, metal, plywood, glass-fibre reinforced plastic or a combination of this materials.

The function of vertical forms is to shape the concrete.

Q11) Explain Vertical Slip formwork?

A11)

The vertical slip form depends on the quick setting properties of the concrete that is required between the initial strength gain and the ability to work.

Placing the concrete into the formwork requires sufficient work to be done practically, it is sufficiently strong to develop the initial strength so that the form slips freshly onto the concrete without any disturbance.

While the concreting process, hydraulic lifters extend the formwork for the entire horizontal projection of a given structure in a continuous sliding motion upward.

Work platforms are permanently attached to the top of the vertical slip form & they are suspended from inside and outside slip form are light in weight.

Q12) Explain Cantilever jump form method?

A12)

In vertical slip form there is no need to erect and destroy expensive scaffolding.

In the cantilever jump form slip formwork method, the lifting device is synchronized by electric motors.

This system is that climbers are independent of cranes and attached to a large area of formwork at storey height.

In this system, shuttering has already been completed, which is part of the structure between individual levels of climbers.

The cantilever jump form system gives maximum protection, providing a complete self-climbing formwork system that is independent of cranes for walls, columns, supports and floor beers.

Q13) Explain Egg shape slip formwork?

A13)

Egg-shape slip formwork is based on the jump form principle that can be adapted to any geometric shape.

If this system, when the egg-shaped circumference changes, the cantilever plate on the periphery is removed or extended.

Individual curvature adjustment can be obtained by adjusting the axis and vertical circumferential slope.

The system can be adjusted independently on each side of the wall as well as products of optimal working condition.

It also shows clear savings in time and personnel costs.

Q14) What is conical formwork system?

A14)

Conical formwork is a system by which it is possible to construct structures of varying wall thicknesses and tapering walls.

It is also possible to construct structures whose formwork changes geometrically from angular to circular.

The conical formwork is made up of cantilever plates and overlapping plates, which are fastened to steel yoke frames.

The cantilever plate and overlapping plates automatically adjust the formwork geometry.

It features integrated scaffolding systems consisting of horizontal work platforms that provide an optimal and safe working area for labour, engineers and supervisors.

Q15) Explain methods of Bridge construction?

A15) Described below are the different methods employed in the construction of bridges.

Cast-in-situ Method of Bridge Construction:

This method is a flexible method of bridge construction where complex and unusual geometrical shapes of dams can be constructed easily. Situations when it is hard to transport pre-fabricated elements either due to size or unreachability, this method is a good choice.

Steel Column to Foundation Details

Balanced Cantilever Method of Bridge Construction:

This method is used for constructing bridges with span 50 to 250m. The bridge constructed can either be cast-in-place or precast. Here, the segments are attached in an alternative manner at opposite ends of the cantilevers supported by piers. This is the best choice for the construction of long span length bridges, irregular length, and cable-stayed bridges.

Balanced Cantilver Bridge Construction

Precast Method of Bridge Construction:

In this method, the bridge is constructed with the help of precast concrete elements. The prefabrication is performed in different methods. The precast elements include:

Precast Beams

Precast Decks

Precast Segmental Decks

Precast method of bridge construction

Span by Span Casting method of Bridge Construction:

This method is associated with cantilever construction method but with many advancements in the technique, it is considered as most economic and rapid in construction. For long bridges and viaducts with an individual span up to 60m, the method is feasible.

Decks are begun at one abutment and constructed continuously by placing segments to the other end of the bridge. Segments can be positioned by either a temporary staying mast system through more commonly using an assembly truss.

Incremental Launching Method of Bridge Construction:

The Incremental Launching Method (ILM) method of bridge construction is employed mainly for the construction of continuous concrete bridges or steel girder bridges. The method performs the procedure in increments. With this method of construction, the bridge deck is built in sections by pushing the structure outwards from an abutment towards the pier. The ILM method can be used for bridge decks with a length greater than 250m.

Incremental Launching Method of Bridge Construction;Image Courtes

Cable-Stayed Method of Bridge Construction:

In the cable-stayed method of construction, cables are used to carry the bridge deck from one or both sides of the supporting tower. The cables carry and transfer all the loads to the foundations. Cable-stayed method of construction is used for constructing bridges that span more than 300m.

Arch Method for Bridge Construction:

Arch shaped bridge construction is one of the most economical choices when the bridge under consideration is required to cross over landscapes that are inaccessible. Many modern arch construction methods have made the arch construction more economical. The arch construction can be built with concrete or pre-cast concrete. The cast-in-situ free cantilever method and slip formed sections are two main construction techniques coming under arch methods.

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