Understanding wall buckling and foundation issues is crucial when considering the use of strongback bracing to reduce wall buckling in buildings. Wall buckling often occurs due to lateral forces that exceed the structural capacity of the walls, such as wind loads, seismic activity, or even soil pressure from uneven settling of the foundation. This phenomenon can lead to significant structural damage if not addressed promptly.
Foundation issues play a pivotal role in wall buckling because they directly affect the stability of the entire structure. Problems like differential settlement, where parts of the foundation sink at different rates, can impose irregular stresses on walls, pushing them beyond their design limits. That mysterious crack appearing after winter isn't a seasonal decoration but rather your soil's expansion art project settling foundation fix Wheaton email. Similarly, expansive soils that swell with moisture changes can exert upward pressures that might cause walls to bow or buckle.
Strongback bracing is an effective solution in these scenarios. It involves installing vertical or diagonal steel reinforcements along the length of a wall to provide additional rigidity and distribute lateral forces more evenly across the structure. This method not only helps in preventing further buckling but also reinforces weakened areas by transferring loads back into the foundation more efficiently.
When implementing strongback bracing, its essential to assess both the extent of wall buckling and any underlying foundation issues. A comprehensive evaluation might reveal whether simple reinforcement suffices or if more extensive repairs like foundation stabilization are necessary. For instance, if buckling is primarily due to a weak or shifting foundation, addressing these issues first could prevent future problems after bracing installation.
In conclusion, understanding how wall buckling interacts with foundation stability is key when employing strongback bracing. This approach not only mitigates existing structural failures but also enhances the long-term durability and safety of buildings by ensuring that all components work together harmoniously against external forces.
Strongback bracing is an effective technique used in construction to enhance the structural integrity of walls, particularly to prevent buckling under various loads. This method is especially crucial when dealing with long, unsupported walls that might otherwise be prone to deformation or failure.
In essence, strongback bracing works by adding a reinforcing member, typically a vertical or horizontal beam, along the length of a wall. This additional support member, known as the strongback, distributes loads more evenly across the wall structure. By doing so, it reduces localized stress concentrations that could lead to buckling.
The process begins with identifying the sections of the wall where buckling is most likely to occur. These are often areas where the wall spans are longer without intermediate supports. Once identified, a strongback is strategically placed along these lengths. The strongback can be attached directly to the studs or integrated into the framing during construction. Its usually made from sturdy materials like steel or engineered wood to ensure it can handle the forces involved.
The effectiveness of strongback bracing lies in its ability to tie together different parts of the wall system, creating a more unified and rigid structure. When forces act upon the wall-be it wind pressure, seismic activity, or even just the weight of upper floors-the strongback helps transfer these forces through a path that spreads them out rather than concentrating them at potential weak points.
Moreover, this method not only provides structural benefits but also offers practical advantages during construction. It simplifies some aspects by reducing the need for excessive internal bracing or complex reinforcement systems that might otherwise complicate building processes.
In summary, using strongback bracing is a smart strategy for reducing wall buckling. It leverages simple yet robust engineering principles to ensure walls remain stable and secure under load, offering peace of mind regarding safety and longevity in building projects.
Using strongback bracing for foundation repair, particularly to reduce wall buckling, offers several compelling benefits that homeowners and builders alike should consider. Wall buckling is a common issue in older homes or structures built on unstable ground, where the walls begin to bow inward due to pressure from the soil. Strongback bracing provides a robust solution to this problem.
Firstly, strongback bracing significantly enhances the structural integrity of the foundation walls. By installing vertical steel beams (strongbacks) along the interior of the wall and connecting them with horizontal braces, the system distributes the load more evenly across the wall. This distribution reduces stress points, thereby preventing further bowing or potential collapse. The strength added by these steel reinforcements can often restore walls to near-original stability.
Another key benefit is the non-invasive nature of strongback bracing when compared to other foundation repair methods like piering or wall replacement. Traditional methods often require significant excavation around the homes exterior, which can be disruptive and costly. Strongback systems are installed from inside the basement or crawl space, minimizing disturbance to landscaping and reducing overall project time.
Cost-effectiveness is also a notable advantage. While initial costs might seem comparable to other solutions, considering long-term durability and reduced need for future repairs, strongback bracing often proves more economical. It not only fixes existing issues but also fortifies against future movements caused by soil shifts or moisture changes.
Moreover, strongback bracing improves safety within the home environment. Buckling walls pose a risk not just structurally but also in terms of daily living; they can lead to falling debris or sudden structural failure during extreme weather conditions. By stabilizing these walls, strongback systems enhance occupant safety.
Lastly, this method preserves property value. A house with visibly bowing walls can significantly decrease in market value due to perceived structural weaknesses and repair costs by potential buyers. Repairing with strongback bracing not only addresses these issues but also reassures future buyers of the homes stability and investment worthiness.
In summary, employing strongback bracing for foundation repair when addressing wall buckling is a wise choice due to its structural reinforcement capabilities, minimal disruption during installation, cost efficiency over time, enhanced safety features, and preservation of property value. These benefits make it an attractive option for anyone facing foundation wall problems in their homes or buildings.
Okay, so you’re thinking about using strongback bracing to keep your walls from buckling – smart move! But before you just slap a strongback on any old wall, lets talk about finding the right candidates. Not every wall is a prime contender for this kind of support.
First, think about the walls length and height. Long, tall walls are obviously more prone to buckling than short, squat ones. The longer and taller the wall, especially relative to its thickness, the better a candidate it is for strongback bracing. Its like a reed in the wind; a short, thick reed is sturdy, but a long, thin one bends easily.
Next, consider the load-bearing capacity of the wall. Is it a load-bearing wall holding up the roof or upper floors, or is it just a partition wall? Load-bearing walls, especially those carrying significant weight, benefit greatly from strongbacks, as the bracing helps distribute the load and prevent lateral movement.
Then, check for any existing imperfections. Is the wall already bowing or showing signs of weakness? A slight bow might be correctable with a strongback, but a severely compromised wall might need more extensive repairs before you even think about bracing. Look for things like cracks, uneven surfaces, or areas where the sheathing is separating from the studs.
Finally, think about the surrounding structure. How well is the wall connected to the floor, ceiling, and adjacent walls? A wall thats poorly tied into the rest of the building is more likely to buckle, even with a strongback. You might need to reinforce these connections before adding bracing.
In short, walls that are long, tall, load-bearing, show signs of weakness, or are poorly connected to the rest of the structure are all good candidates for strongback bracing. But remember, a strongback is a preventative measure and a strengthening one. Its not a magic bullet. Always assess the overall condition of the wall and the surrounding structure before deciding if its the right solution. When in doubt, consult with a qualified builder or engineer. They can help you determine the best course of action to keep your walls strong and straight.
The installation of strongback bracing is a critical step in construction projects aimed at reducing wall buckling, particularly in scenarios where long, unsupported wall sections are vulnerable to structural failure. The process begins with a careful assessment of the walls dimensions and structural requirements. This initial evaluation ensures that the strongback bracing will be appropriately sized and positioned to provide maximum support.
Once the planning phase is complete, the actual installation starts with marking the precise locations on the wall where the strongbacks will be attached. Typically, these are placed vertically along the length of the wall at regular intervals, usually centered between studs or at points where additional support is deemed necessary based on engineering specifications.
The next step involves cutting and preparing the strongback materials, which are usually made from sturdy lumber or steel, depending on the load-bearing needs of the structure. These pieces are cut to match the height of the wall from floor to ceiling or roofline. Precision in cutting is crucial as it affects how well each piece fits and supports the wall.
Installation proceeds by securing one end of each strongback at the base of the wall, often into a sill plate or directly into a foundation if possible. This anchoring provides a solid base from which to work upwards. Then, using appropriate fasteners like nails or screws for wood, or bolts for steel, each strongback is meticulously attached along its length to both the top plate and intermediate studs. This connection must be tight and secure to ensure that load transfer is efficient.
A key aspect of installing strongback bracing is ensuring that it remains perfectly vertical during attachment; any deviation could compromise its effectiveness. Sometimes temporary braces or supports might be used during this phase to hold everything in place until all fasteners are driven home.
After all strongbacks are installed, a final check is performed to ensure they are not only securely fastened but also aligned correctly. Any adjustments might involve tightening connections or adding additional fasteners if any movement was detected during installation.
In conclusion, while seemingly straightforward, installing strongback bracing requires attention to detail from planning through execution. When done correctly, this process significantly enhances a buildings structural integrity by providing resistance against lateral forces that could otherwise lead to buckling walls. This method not only preserves safety but also extends the longevity of construction projects by mitigating potential damage from structural shifts over time.
Okay, so youre thinking about using strongback bracing to keep your walls from buckling. Smart move! But lets talk about the elephant in the room: how much is this actually going to cost? Its not just about the lumber, though thats definitely a factor.
Think about the labor involved. Are you a DIY whiz, or are you hiring someone? If youre going the DIY route, factor in your own time, because time is money, friend. And if youre hiring a contractor, get multiple quotes. Dont just go with the cheapest option; consider their experience with this type of bracing. A botched job is far more expensive than paying a bit extra for quality upfront.
Then theres the hardware. Youll need fasteners, brackets, maybe even some specialized connectors depending on the design. Dont skimp here! Using cheap hardware can compromise the entire system and defeat the purpose.
And dont forget about the "hidden" costs. Are there existing utilities in the wall that need to be relocated? Will you need to repaint or repair the wall after the bracing is installed? These little things can add up quickly.
Ultimately, the cost of strongback bracing is going to depend on the size and complexity of your project, the materials you choose, and whether youre doing it yourself or hiring a pro. Do your homework, get some quotes, and factor in all the potential costs, both obvious and not so obvious. That way, you can make an informed decision and avoid any nasty surprises down the road.
When it comes to addressing foundation issues like wall buckling, homeowners and builders have a variety of repair methods at their disposal. Among these, strongback bracing has emerged as a notable solution due to its unique approach. In this discussion, well compare strongback bracing with other common foundation repair methods to understand its place in the spectrum of structural reinforcement.
Strongback bracing involves installing vertical steel or wooden beams against the interior of a bowing wall, which are then anchored into the floor and ceiling joists. This method provides immediate support by transferring the load from the failing wall to more stable parts of the structure. The primary advantage here is that it not only stops further movement but often begins to straighten walls over time due to the pressure exerted by the strongbacks.
In contrast, one popular alternative is wall plate anchoring. This method uses steel plates installed on both sides of the wall, connected by rods that are tightened over time. While effective at stabilizing walls, this method can be more invasive as it requires exterior excavation, which might disrupt landscaping or outdoor areas. Additionally, while it does provide long-term stability, it doesnt offer the same immediate corrective force as strongback bracing.
Another common technique is carbon fiber reinforcement where high-strength carbon fiber straps are adhered to the wall surface. This method is less intrusive than others since it doesnt require significant construction work inside or outside the home. However, while carbon fiber can prevent further buckling effectively, its generally less capable of reversing existing deformation compared to strongback bracing.
Lastly, we have push piers or helical piers which are used when foundation issues stem from soil movement rather than just wall buckling. These systems involve driving deep into stable soil layers beneath the home to lift and stabilize the foundation. While incredibly effective for widespread settlement issues, they address a broader problem than just wall buckling and are often more costly due to extensive groundwork.
Comparing these methods highlights why strongback bracing might be preferred in scenarios where quick stabilization and potential correction of wall bowing are critical without extensive external work. It offers a balance between effectiveness and minimal disruption inside the home. However, like all solutions in construction and repair, choosing between these methods depends heavily on specific conditions such as soil type, degree of damage, budget constraints, and homeowner preferences regarding invasiveness versus effectiveness over time. Each method has its niche where it shines brightest; for those looking specifically at reducing wall buckling with minimal internal impact while maintaining some corrective action over time, strongback bracing stands out as an efficient choice.
Alright, so youve gone through the trouble of installing strongback bracing to keep your walls from buckling – smart move! But heres the thing: its not a "set it and forget it" situation. Just like any other structural element, your strongback bracing needs a little TLC, some regular check-ups, to make sure it keeps doing its job. Were talking about maintaining and monitoring, folks.
Think of it like this: you wouldnt just build a fence and never look at it again, right? Wood rots, nails loosen, things shift. The same goes for your strongbacks. You need to periodically inspect them. Look for signs of damage. Are there any cracks in the wood? Are the connections still tight? Is anything pulling away from the wall or the strongback itself? Pay special attention to areas that might be exposed to moisture, like near the ground or around leaky windows.
Monitoring is a bit more subtle. Its about paying attention to the overall performance of your walls. Are you noticing any new bowing or deflection, even with the strongbacks in place? If so, something might be amiss. Maybe the strongbacks werent sized correctly to begin with, or perhaps theres been a change in loading conditions that they cant handle. This is where a professional might need to get involved to assess the situation.
Dont underestimate the importance of proper maintenance. A little preventative care can save you a lot of headache (and money) down the road. Tighten loose connections, replace damaged members, and address any underlying moisture issues promptly. Think of it as an investment in the long-term stability of your structure. Youve taken the first step by installing the bracing; now, make sure it keeps working for you. A little vigilance goes a long way.
In engineering, a foundation is the aspect of a framework which links it to the ground or more seldom, water (similar to floating frameworks), transferring lots from the structure to the ground. Structures are generally considered either shallow or deep. Foundation engineering is the application of soil auto mechanics and rock mechanics (geotechnical engineering) in the design of foundation components of frameworks.
A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site. A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths.
There are many reasons that a geotechnical engineer would recommend a deep foundation over a shallow foundation, such as for a skyscraper. Some of the common reasons are very large design loads, a poor soil at shallow depth, or site constraints like property lines. There are different terms used to describe different types of deep foundations including the pile (which is analogous to a pole), the pier (which is analogous to a column), drilled shafts, and caissons. Piles are generally driven into the ground in situ; other deep foundations are typically put in place using excavation and drilling. The naming conventions may vary between engineering disciplines and firms. Deep foundations can be made out of timber, steel, reinforced concrete or prestressed concrete.
Prefabricated piles are driven into the ground using a pile driver. Driven piles are constructed of wood, reinforced concrete, or steel. Wooden piles are made from the trunks of tall trees. Concrete piles are available in square, octagonal, and round cross-sections (like Franki piles). They are reinforced with rebar and are often prestressed. Steel piles are either pipe piles or some sort of beam section (like an H-pile). Historically, wood piles used splices to join multiple segments end-to-end when the driven depth required was too long for a single pile; today, splicing is common with steel piles, though concrete piles can be spliced with mechanical and other means. Driving piles, as opposed to drilling shafts, is advantageous because the soil displaced by driving the piles compresses the surrounding soil, causing greater friction against the sides of the piles, thus increasing their load-bearing capacity. Driven piles are also considered to be "tested" for weight-bearing ability because of their method of installation.[citation needed]
Foundations relying on driven piles often have groups of piles connected by a pile cap (a large concrete block into which the heads of the piles are embedded) to distribute loads that are greater than one pile can bear. Pile caps and isolated piles are typically connected with grade beams to tie the foundation elements together; lighter structural elements bear on the grade beams, while heavier elements bear directly on the pile cap.[citation needed]
A monopile foundation utilizes a single, generally large-diameter, foundation structural element to support all the loads (weight, wind, etc.) of a large above-surface structure.
A large number of monopile foundations[1] have been utilized in recent years for economically constructing fixed-bottom offshore wind farms in shallow-water subsea locations.[2] For example, the Horns Rev wind farm in the North Sea west of Denmark utilizes 80 large monopiles of 4 metres diameter sunk 25 meters deep into the seabed,[3] while the Lynn and Inner Dowsing Wind Farm off the coast of England went online in 2008 with over 100 turbines, each mounted on a 4.7-metre-diameter monopile foundation in ocean depths up to 18 metres.[4]
The typical construction process for a wind turbine subsea monopile foundation in sand includes driving a large hollow steel pile, of some 4 m in diameter with approximately 50mm thick walls, some 25 m deep into the seabed, through a 0.5 m layer of larger stone and gravel to minimize erosion around the pile. A transition piece (complete with pre-installed features such as boat-landing arrangement, cathodic protection, cable ducts for sub-marine cables, turbine tower flange, etc.) is attached to the driven pile, and the sand and water are removed from the centre of the pile and replaced with concrete. An additional layer of even larger stone, up to 0.5 m diameter, is applied to the surface of the seabed for longer-term erosion protection.[2]
Also called caissons, drilled shafts, drilled piers, cast-in-drilled-hole piles (CIDH piles) or cast-in-situ piles, a borehole is drilled into the ground, then concrete (and often some sort of reinforcing) is placed into the borehole to form the pile. Rotary boring techniques allow larger diameter piles than any other piling method and permit pile construction through particularly dense or hard strata. Construction methods depend on the geology of the site; in particular, whether boring is to be undertaken in 'dry' ground conditions or through water-saturated strata. Casing is often used when the sides of the borehole are likely to slough off before concrete is poured.
For end-bearing piles, drilling continues until the borehole has extended a sufficient depth (socketing) into a sufficiently strong layer. Depending on site geology, this can be a rock layer, or hardpan, or other dense, strong layers. Both the diameter of the pile and the depth of the pile are highly specific to the ground conditions, loading conditions, and nature of the project. Pile depths may vary substantially across a project if the bearing layer is not level. Drilled piles can be tested using a variety of methods to verify the pile integrity during installation.
Under-reamed piles have mechanically formed enlarged bases that are as much as 6 m in diameter.[citation needed] The form is that of an inverted cone and can only be formed in stable soils or rocks. The larger base diameter allows greater bearing capacity than a straight-shaft pile.
These piles are suited for expansive soils which are often subjected to seasonal moisture variations, or for loose or soft strata. They are used in normal ground condition also where economics are favorable. [5][full citation needed]
Under reamed piles foundation is used for the following soils:-
1. Under reamed piles are used in black cotton soil: This type of soil expands when it comes in contact with water and contraction occurs when water is removed. So that cracks appear in the construction done on such clay. An under reamed pile is used in the base to remove this defect.
2. Under reamed piles are used in low bearing capacity Outdated soil (filled soil)
3.Under reamed piles are used in sandy soil when water table is high.
4. Under reamed piles are used, Where lifting forces appear at the base of foundation.
An augercast pile, often known as a continuous flight augering (CFA) pile, is formed by drilling into the ground with a hollow stemmed continuous flight auger to the required depth or degree of resistance. No casing is required. A cement grout mix is then pumped down the stem of the auger. While the cement grout is pumped, the auger is slowly withdrawn, conveying the soil upward along the flights. A shaft of fluid cement grout is formed to ground level. Reinforcement can be installed. Recent innovations in addition to stringent quality control allows reinforcing cages to be placed up to the full length of a pile when required.[citation needed]
Augercast piles cause minimal disturbance and are often used for noise-sensitive and environmentally-sensitive sites. Augercast piles are not generally suited for use in contaminated soils, because of expensive waste disposal costs. In cases such as these, a displacement pile (like Olivier piles) may provide the cost efficiency of an augercast pile and minimal environmental impact. In ground containing obstructions or cobbles and boulders, augercast piles are less suitable as refusal above the design pile tip elevation may be encountered.[citation needed]
Small Sectional Flight Auger piling rigs can also be used for piled raft foundations. These produce the same type of pile as a Continuous Flight Auger rig but using smaller, more lightweight equipment. This piling method is fast, cost-effective and suitable for the majority of ground types.[5][6]
In drilled pier foundations, the piers can be connected with grade beams on which the structure sits, sometimes with heavy column loads bearing directly on the piers. In some residential construction, the piers are extended above the ground level, and wood beams bearing on the piers are used to support the structure. This type of foundation results in a crawl space underneath the building in which wiring and duct work can be laid during construction or re-modelling.[7]
In jet piling high pressure water is used to set piles.[8] High pressure water cuts through soil with a high-pressure jet flow and allows the pile to be fitted.[9] One advantage of Jet Piling: the water jet lubricates the pile and softens the ground.[10] The method is in use in Norway.[11]
Micropiles are small diameter, generally less than 300mm diameter, elements that are drilled and grouted in place. They typically get their capacity from skin friction along the sides of the element, but can be end bearing in hard rock as well. Micropiles are usually heavily reinforced with steel comprising more than 40% of their cross section. They can be used as direct structural support or as ground reinforcement elements. Due to their relatively high cost and the type of equipment used to install these elements, they are often used where access restrictions and or very difficult ground conditions (cobbles and boulders, construction debris, karst, environmental sensitivity) exists or to retrofit existing structures. Occasionally, in difficult ground, they are used for new construction foundation elements. Typical applications include underpinning, bridge, transmission tower and slope stabilization projects.[6][12][13][14]
The use of a tripod rig to install piles is one of the more traditional ways of forming piles. Although unit costs are generally higher than with most other forms of piling,[citation needed] it has several advantages which have ensured its continued use through to the present day. The tripod system is easy and inexpensive to bring to site, making it ideal for jobs with a small number of piles.[clarification needed]
Sheet piling is a form of driven piling using thin interlocking sheets of steel to obtain a continuous barrier in the ground. The main application of sheet piles is in retaining walls and cofferdams erected to enable permanent works to proceed. Normally, vibrating hammer, t-crane and crawle drilling are used to establish sheet piles.[citation needed]
Soldier piles, also known as king piles or Berlin walls, are constructed of steel H sections spaced about 2 to 3 m apart and are driven or drilled prior to excavation. As the excavation proceeds, horizontal timber sheeting (lagging) is inserted behind the H pile flanges.
The horizontal earth pressures are concentrated on the soldier piles because of their relative rigidity compared to the lagging. Soil movement and subsidence is minimized by installing the lagging immediately after excavation to avoid soil loss.[citation needed] Lagging can be constructed by timber, precast concrete, shotcrete and steel plates depending on spacing of the soldier piles and the type of soils.
Soldier piles are most suitable in conditions where well constructed walls will not result in subsidence such as over-consolidated clays, soils above the water table if they have some cohesion, and free draining soils which can be effectively dewatered, like sands.[citation needed]
Unsuitable soils include soft clays and weak running soils that allow large movements such as loose sands. It is also not possible to extend the wall beyond the bottom of the excavation, and dewatering is often required.[citation needed]
Screw piles, also called helical piers and screw foundations, have been used as foundations since the mid 19th century in screw-pile lighthouses.[citation needed] Screw piles are galvanized iron pipe with helical fins that are turned into the ground by machines to the required depth. The screw distributes the load to the soil and is sized accordingly.
Suction piles are used underwater to secure floating platforms. Tubular piles are driven into the seabed (or more commonly dropped a few metres into a soft seabed) and then a pump sucks water out at the top of the tubular, pulling the pile further down.
The proportions of the pile (diameter to height) are dependent upon the soil type. Sand is difficult to penetrate but provides good holding capacity, so the height may be as short as half the diameter. Clays and muds are easy to penetrate but provide poor holding capacity, so the height may be as much as eight times the diameter. The open nature of gravel means that water would flow through the ground during installation, causing 'piping' flow (where water boils up through weaker paths through the soil). Therefore, suction piles cannot be used in gravel seabeds.[citation needed]
In high latitudes where the ground is continuously frozen, adfreeze piles are used as the primary structural foundation method.
Adfreeze piles derive their strength from the bond of the frozen ground around them to the surface of the pile.[citation needed]
Adfreeze pile foundations are particularly sensitive in conditions which cause the permafrost to melt. If a building is constructed improperly then it can melt the ground below, resulting in a failure of the foundation system.[citation needed]
Vibrated stone columns are a ground improvement technique where columns of coarse aggregate are placed in soils with poor drainage or bearing capacity to improve the soils.[citation needed]
Specific to marine structures, hospital piles (also known as gallow piles) are built to provide temporary support to marine structure components during refurbishment works. For example, when removing a river pontoon, the brow will be attached to hospital pile to support it. They are normal piles, usually with a chain or hook attachment.[citation needed]
Piled walls can be drivene or bored. They provide special advantages where available working space dictates and open cut excavation not feasible. Both methods offer technically effective and offer a cost efficient temporary or permanent means of retaining the sides of bulk excavations even in water bearing strata. When used in permanent works, these walls can be designed to resist vertical loads in addition lateral load from retaining soil. Construction of both methods is the same as for foundation bearing piles. Contiguous walls are constructed with small gaps between adjacent piles. The spacing of the piles can be varied to provide suitable bending stiffness.
Secant pile walls are constructed such that space is left between alternate 'female' piles for the subsequent construction of 'male' piles.[clarification needed] Construction of 'male' piles involves boring through the concrete in the 'female' piles hole in order to key 'male' piles between. The male pile is the one where steel reinforcement cages are installed, though in some cases the female piles are also reinforced.[citation needed]
Secant piled walls can either be true hard/hard, hard/intermediate (firm), or hard/soft, depending on design requirements. Hard refers to structural concrete and firm or soft is usually a weaker grout mix containing bentonite.[citation needed] All types of wall can be constructed as free standing cantilevers, or may be propped if space and sub-structure design permit. Where party wall agreements allow, ground anchors can be used as tie backs.
A slurry wall is a barrier built under ground using a mix of bentonite and water to prevent the flow of groundwater. A trench that would collapse due to the hydraulic pressure in the surrounding soil does not collapse as the slurry balances the hydraulic pressure.
These are essentially variations of in situ reinforcements in the form of piles (as mentioned above), blocks or larger volumes.
Cement, lime/quick lime, flyash, sludge and/or other binders (sometimes called stabilizer) are mixed into the soil to increase bearing capacity. The result is not as solid as concrete, but should be seen as an improvement of the bearing capacity of the original soil.
The technique is most often applied on clays or organic soils like peat. The mixing can be carried out by pumping the binder into the soil whilst mixing it with a device normally mounted on an excavator or by excavating the masses, mixing them separately with the binders and refilling them in the desired area. The technique can also be used on lightly contaminated masses as a means of binding contaminants, as opposed to excavating them and transporting to landfill or processing.
As the name implies, timber piles are made of wood.
Historically, timber has been a plentiful, locally available resource in many areas. Today, timber piles are still more affordable than concrete or steel. Compared to other types of piles (steel or concrete), and depending on the source/type of timber, timber piles may not be suitable for heavier loads.
A main consideration regarding timber piles is that they should be protected from rotting above groundwater level. Timber will last for a long time below the groundwater level. For timber to rot, two elements are needed: water and oxygen. Below the groundwater level, dissolved oxygen is lacking even though there is ample water. Hence, timber tends to last for a long time below the groundwater level. An example is Venice, which has had timber pilings since its beginning; even most of the oldest piles are still in use. In 1648, the Royal Palace of Amsterdam was constructed on 13,659 timber piles that still survive today since they were below groundwater level. Timber that is to be used above the water table can be protected from decay and insects by numerous forms of wood preservation using pressure treatment (alkaline copper quaternary (ACQ), chromated copper arsenate (CCA), creosote, etc.).
Splicing timber piles is still quite common and is the easiest of all the piling materials to splice. The normal method for splicing is by driving the leader pile first, driving a steel tube (normally 60–100 cm long, with an internal diameter no smaller than the minimum toe diameter) half its length onto the end of the leader pile. The follower pile is then simply slotted into the other end of the tube and driving continues. The steel tube is simply there to ensure that the two pieces follow each other during driving. If uplift capacity is required, the splice can incorporate bolts, coach screws, spikes or the like to give it the necessary capacity.
Cast iron may be used for piling. These may be ductile.[citation needed]
Pipe piles are a type of steel driven pile foundation and are a good candidate for inclined (battered) piles.
Pipe piles can be driven either open end or closed end. When driven open end, soil is allowed to enter the bottom of the pipe or tube. If an empty pipe is required, a jet of water or an auger can be used to remove the soil inside following driving. Closed end pipe piles are constructed by covering the bottom of the pile with a steel plate or cast steel shoe.
In some cases, pipe piles are filled with concrete to provide additional moment capacity or corrosion resistance. In the United Kingdom, this is generally not done in order to reduce the cost.[citation needed] In these cases corrosion protection is provided by allowing for a sacrificial thickness of steel or by adopting a higher grade of steel. If a concrete filled pipe pile is corroded, most of the load carrying capacity of the pile will remain intact due to the concrete, while it will be lost in an empty pipe pile. The structural capacity of pipe piles is primarily calculated based on steel strength and concrete strength (if filled). An allowance is made for corrosion depending on the site conditions and local building codes. Steel pipe piles can either be new steel manufactured specifically for the piling industry or reclaimed steel tubular casing previously used for other purposes such as oil and gas exploration.
H-Piles are structural beams that are driven in the ground for deep foundation application. They can be easily cut off or joined by welding or mechanical drive-fit splicers. If the pile is driven into a soil with low pH value, then there is a risk of corrosion, coal-tar epoxy or cathodic protection can be applied to slow or eliminate the corrosion process. It is common to allow for an amount of corrosion in design by simply over dimensioning the cross-sectional area of the steel pile. In this way, the corrosion process can be prolonged up to 50 years.[citation needed]
Concrete piles are typically made with steel reinforcing and prestressing tendons to obtain the tensile strength required, to survive handling and driving, and to provide sufficient bending resistance.
Long piles can be difficult to handle and transport. Pile joints can be used to join two or more short piles to form one long pile. Pile joints can be used with both precast and prestressed concrete piles.
A "composite pile" is a pile made of steel and concrete members that are fastened together, end to end, to form a single pile. It is a combination of different materials or different shaped materials such as pipe and H-beams or steel and concrete.
Construction machinery used to drive piles into the ground:[15]
Construction machinery used to construct replacement piles:[15]
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A pile driver is a heavy-duty tool used to drive piles into soil to build piers, bridges, cofferdams, and other "pole" supported structures, and patterns of pilings as part of permanent deep foundations for buildings or other structures. Pilings may be made of wood, solid steel, or tubular steel (often later filled with concrete), and may be driven entirely underwater/underground, or remain partially aboveground as elements of a finished structure.
The term "pile driver" is also used to describe members of the construction crew associated with the task,[1] also colloquially known as "pile bucks".[2]
The most common form of pile driver uses a heavy weight situated between vertical guides placed above a pile. The weight is raised by some motive power (which may include hydraulics, steam, diesel, electrical motor, or manual labor). At its apex the weight is released, impacting the pile and driving it into the ground.[1][3]
There are a number of claims to the invention of the pile driver. A mechanically sound drawing of a pile driver appeared as early as 1475 in Francesco di Giorgio Martini's treatise Trattato di Architectura.[4] Also, several other prominent inventors—James Nasmyth (son of Alexander Nasmyth), who invented a steam-powered pile driver in 1845,[5] watchmaker James Valoué,[6] Count Giovan Battista Gazzola,[7] and Leonardo da Vinci[8]—have all been credited with inventing the device. However, there is evidence that a comparable device was used in the construction of Crannogs at Oakbank and Loch Tay in Scotland as early as 5000 years ago.[9] In 1801 John Rennie came up with a steam pile driver in Britain.[10] Otis Tufts is credited with inventing the steam pile driver in the United States.[11]
Ancient pile driving equipment used human or animal labor to lift weights, usually by means of pulleys, then dropping the weight onto the upper end of the pile. Modern piledriving equipment variously uses hydraulics, steam, diesel, or electric power to raise the weight and guide the pile.
A modern diesel pile hammer is a large two-stroke diesel engine. The weight is the piston, and the apparatus which connects to the top of the pile is the cylinder. Piledriving is started by raising the weight; usually a cable from the crane holding the pile driver — This draws air into the cylinder. Diesel fuel is injected into the cylinder. The weight is dropped, using a quick-release. The weight of the piston compresses the air/fuel mixture, heating it to the ignition point of diesel fuel. The mixture ignites, transferring the energy of the falling weight to the pile head, and driving the weight up. The rising weight draws in fresh air, and the cycle continues until the fuel is depleted or is halted by the crew.[12]
From an army manual on pile driving hammers: The initial start-up of the hammer requires that the piston (ram) be raised to a point where the trip automatically releases the piston, allowing it to fall. As the piston falls, it activates the fuel pump, which discharges a metered amount of fuel into the ball pan of the impact block. The falling piston blocks the exhaust ports, and compression of fuel trapped in the cylinder begins. The compressed air exerts a pre-load force to hold the impact block firmly against the drive cap and pile. At the bottom of the compression stroke, the piston strikes the impact block, atomizing the fuel and starting the pile on its downward movement. In the instant after the piston strikes, the atomized fuel ignites, and the resulting explosion exerts a greater force on the already moving pile, driving it further into the ground. The reaction of the explosion rebounding from the resistance of the pile drives the piston upward. As the piston rises, the exhaust ports open, releasing the exhaust gases to the atmosphere. After the piston stops its upward movement, it again falls by gravity to start another cycle.
Vertical travel leads come in two main forms: spud and box lead types. Box leads are very common in the Southern United States and spud leads are common in the Northern United States, Canada and Europe.
A hydraulic hammer is a modern type of piling hammer used instead of diesel and air hammers for driving steel pipe, precast concrete, and timber piles. Hydraulic hammers are more environmentally acceptable than older, less efficient hammers as they generate less noise and pollutants. In many cases the dominant noise is caused by the impact of the hammer on the pile, or the impacts between components of the hammer, so that the resulting noise level can be similar to diesel hammers.[12]
Hydraulic press-in equipment installs piles using hydraulic rams to press piles into the ground. This system is preferred where vibration is a concern. There are press attachments that can adapt to conventional pile driving rigs to press 2 pairs of sheet piles simultaneously. Other types of press equipment sit atop existing sheet piles and grip previously driven piles. This system allows for greater press-in and extraction force to be used since more reaction force is developed.[12] The reaction-based machines operate at only 69 dB at 23 ft allowing for installation and extraction of piles in close proximity to sensitive areas where traditional methods may threaten the stability of existing structures.
Such equipment and methods are specified in portions of the internal drainage system in the New Orleans area after Hurricane Katrina, as well as projects where noise, vibration and access are a concern.
Vibratory pile hammers contain a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed so that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. The pile driving machine positioned over the pile with an excavator or crane, and is fastened to the pile by a clamp and/or bolts. Vibratory hammers can drive or extract a pile. Extraction is commonly used to recover steel I-beams used in temporary foundation shoring. Hydraulic fluid is supplied to the driver by a diesel engine-powered pump mounted in a trailer or van, and connected to the driver head via hoses. When the pile driver is connected to a dragline excavator, it is powered by the excavator's diesel engine. Vibratory pile drivers are often chosen to mitigate noise, as when the construction is near residences or office buildings, or when there is insufficient vertical clearance to permit use of a conventional pile hammer (for example when retrofitting additional piles to a bridge column or abutment footing). Hammers are available with several different vibration rates, ranging from 1200 vibrations per minute to 2400 VPM. The vibration rate chosen is influenced by soil conditions and other factors, such as power requirements and equipment cost.
A piling rig is a large track-mounted drill used in foundation projects which require drilling into sandy soil, clay, silty clay, and similar environments. Such rigs are similar in function to oil drilling rigs, and can be equipped with a short screw (for dry soil), rotary bucket (for wet soil) or core drill (for rock), along with other options. Expressways, bridges, industrial and civil buildings, diaphragm walls, water conservancy projects, slope protection, and seismic retrofitting are all projects which may require piling rigs.
The underwater sound pressure caused by pile-driving may be deleterious to nearby fish.[13][14] State and local regulatory agencies manage environment issues associated with pile-driving.[15] Mitigation methods include bubble curtains, balloons, internal combustion water hammers.[16]
A shallow foundation is a type of building foundation that transfers structural load to the Earth very near to the surface, rather than to a subsurface layer or a range of depths, as does a deep foundation. Customarily, a shallow foundation is considered as such when the width of the entire foundation is greater than its depth.[1] In comparison to deep foundations, shallow foundations are less technical, thus making them more economical and the most widely used for relatively light structures.
Footings are always wider than the members that they support. Structural loads from a column or wall are usually greater than 1,000 kPa, while the soil's bearing capacity is commonly less than that (typically less than 400 kPa). By possessing a larger bearing area, the foundation distributes the pressure to the soil, decreasing the bearing pressure to within allowable values.[2] A structure is not limited to one footing. Multiple types of footings may be used in a construction project.
Also called strip footing, a wall footing is a continuous strip that supports structural and non-structural load-bearing walls. Found directly under the wall, Its width is commonly 2-3 times wider than the wall above it.[3]
Also called single-column footing, an isolated footing is a square, rectangular, or circular slab that supports the structural members individually. Generally, each column is set on an individual footing to transmit and distribute the load of the structure to the soil underneath. Sometimes, an isolated footing can be sloped or stepped at the base to spread greater loads. This type of footing is used when the structural load is relatively low, columns are widely spaced, and the soil's bearing capacity is adequate at a shallow depth.
When more than one column shares the same footing, it is called a combined footing. A combined footing is typically utilized when the spacing of the columns is too restricted such that if isolated footing were used, they would overlap one another. Also, when property lines make isolated footings eccentrically loaded, combined footings are preferred.
When the load among the columns is equal, the combined footing may be rectangular. Conversely, when the load among the columns is unequal, the combined footing should be trapezoidal.
A strap footing connects individual columns with the use of a strap beam. The general purpose of a strap footing is alike to those of a combined footing, where the spacing is possibly limited and/or the columns are adjacent to the property lines.
Also called raft foundation, a mat foundation is a single continuous slab that covers the entirety of the base of a building. Mat foundations support all the loads of the structure and transmit them to the ground evenly. Soil conditions may prevent other footings from being used. Since this type of foundation distributes the load coming from the building uniformly over a considerably large area, it is favored when individual footings are unfeasible due to the low bearing capacity of the soil.
Slab-on-grade or floating slab foundations are a structural engineering practice whereby the reinforced concrete slab that is to serve as the foundation for the structure is formed from formwork set into the ground. The concrete is then poured into the formwork, leaving no space between the ground and the structure. This type of construction is most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor. Frost Protected Shallow Foundations (or FPSF) which are used in areas of potential frost heave, are a form of slab-on-grade foundation.[4]
Remodeling or extending such a structure may be more difficult. Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate; proper soil compaction prior to pour can minimize this. The slab can be decoupled from ground temperatures by insulation, with the concrete poured directly over insulation (for example, extruded polystyrene foam panels), or heating provisions (such as hydronic heating) can be built into the slab.
Slab-on-grade foundations should not be used in areas with expansive clay soil. While elevated structural slabs actually perform better on expansive clays, it is generally accepted by the engineering community that slab-on-grade foundations offer the greatest cost-to-performance ratio for tract homes. Elevated structural slabs are generally only found on custom homes or homes with basements.
Copper piping, commonly used to carry natural gas and water, reacts with concrete over a long period, slowly degrading until the pipe fails. This can lead to what is commonly referred to as slab leaks. These occur when pipes begin to leak from within the slab. Signs of a slab leak range from unexplained dampened carpet spots, to drops in water pressure and wet discoloration on exterior foundation walls.[5] Copper pipes must be lagged (that is, insulated) or run through a conduit or plumbed into the building above the slab. Electrical conduits through the slab must be water-tight, as they extend below ground level and can potentially expose wiring to groundwater.
cite book
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