Written by Bradley Mackenzie
- Eccentric Foundations. An eccentric foundation is a foundation whereby t he wall sits on the outer edge of the foundation. ...
- Typical Foundations
- A typical foundation differs from this. This type of foundation can either be placed astride the line of junction, thereby acting as a Party Wall.
What is an eccentric wall foundation design?
May 21, 2020 · Eccentric Foundations are one of the most commonly used types of foundation designs in rear or side extensions and are commonly seen forming part of Party Wall Awards, Party Wall Notices and Party Wall Surveyor requests. An eccentric foundation is a foundation whereby the wall sits on the outer edge of the foundation.
What is an example of an eccentricity?
Mar 08, 2013 · The foundation is rectangular; the self weight (V sw) acts at the centreline. To calculate the effective foundation width (B’) for a bearing failure ULS verification, I need to know the eccentricity (e). Using the general form: e = M/V Is my eccentricity 1: e = (M a + H a *h + V a *x) / V sw Or 2: e = [(M a + H a *h) / V sw] + x
What is the effect of eccentricity on footings?
Feb 06, 2011 · Initially the eccentricity of the applied load needs to be calculated. It can be determined from the vertical load and the moment data available, but the basic purpose of design is to calculate the dimensions of the footing. The reduced effective dimension cannot be …
Is eccentricity present in sap-2000 results?
Locating a load away from the centroid (center) of the footing creates an eccentricity that changes the distribution of loads in the soil and may result in a bearing pressure that exceeds the allowable bearing capacity. These undesirable loading conditions increase the further the column is placed from the centroid or as the eccentricity increases.
What is eccentricity footing?
The eccentric footing is a spread or wall footing that must resist a moment in addition to the axial column load, and it has the shape of the shoe.Jul 15, 2020
How do you find the eccentricity of a foundation?
The eccentricity can be calculated from the following equation for eccentrically loaded foundations. when eccentricity is known the above equation can be simplified as follows. When e = B/6, qmin becomes zero, and the further increase of the eccentricity ( e > B/6), negative pressure will be generated on the soil.
Is eccentric footing safe?
Generally designing of eccentric footing is avoided. But in cases where Neighbourer's construction exists and it is not possible to adopt spread footings and there is no way out, it has to be done.
What is concentric and eccentric loading?
Loads applied to the center of gravity of the column cross-section are considered concentric. A beam that passes over and rests on the top of a column is an example of concentric loading. COLUMN LOADING – ECCENTRIC LOADING. Any load which is not concentric is eccentric.
What is meant by eccentricity?
1a : the quality or state of being eccentric. b : deviation from an established pattern or norm especially : odd or whimsical behavior. 2a : a mathematical constant that for a given conic section is the ratio of the distances from any point of the conic section to a focus and the corresponding directrix.
What is eccentrically loaded?
A load on a column or pile which is nonsymmetric with respect to the central axis, therefore producing a bending moment.
What is eccentricity construction?
The degree to which two forms fail to share a common center; for example, in a pipe or tube whose inside is off-center toth regard to the outside.
What is eccentric column?
Eccentric loading on column When the load acting on the column is offset from the centroid of the column, then it establishes the bending of column along with the axial stress. This offset loading of the column is referred as eccentric loading. Eccentric loading will not be at the middle of cross-section of the column.
What is eccentricity in civil engineering?
e = eccentricity, the distance from the center of gravity of the column section to the center of gravity of the applied load. Eccentri- city in this analysis is considered as being parallel to one of the sides of a rectangular column. = increments of deflection at midlength of a column in Salmon's analysis.
What is difference between eccentric and concentric?
In a concentric contraction, the muscle tension rises to meet the resistance then remains stable as the muscle shortens. During eccentric contraction, the muscle lengthens as the resistance becomes greater than the force the muscle is producing.
What is an example of an eccentric motion?
Movements that employ eccentric contractions include walking down stairs, running downhill, lowering weights, and the downward motion of squats, push-ups or pull-ups.Feb 24, 2021
What is the difference between eccentric and?
2:003:48Isometric vs. Concentric vs. Eccentric, what's the deal? - YouTubeYouTubeStart of suggested clipEnd of suggested clipYou start down low the muscle is long i lift the weight the muscle shortens okay so i contracted theMoreYou start down low the muscle is long i lift the weight the muscle shortens okay so i contracted the muscle the muscle shortens that's called a concentric an eccentric contraction is the opposite.
Effect Of Eccentricity On Analysis and Design Of Isolated Footings
PAPER ON EFFECT OF ECCENTRICITY ON ANALYSIS & DESIGN OF ISOLATED FOOTINGS#N#(A CASE STUDY OF Jammu and Kashmir)
Kanwarjot Singh
Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.
What causes a disturbed foundation?
Disturbed and/or contaminated foundation material encountered at the planned bottom of footing elevation is unacceptable and must be corrected even if the material itself is suitable. Disturbance of the foundation-bearing surface usually is caused by the excavation means and methods, including excavating below the footing elevation or disturbing the grade with the teeth on the excavator bucket. Contamination usually is due to the presence of water (typically uncontrolled) or sloughing. All disturbed or contaminated material must be removed to expose a suitable foundation surface. The foundation must then be restored by the Contractor, at the Contractor’s expense, to a condition at least equal to the undisturbed foundation as determined by the Engineer.
What is the importance of confirming suitable foundation material?
The importance of confirming suitable foundation material cannot be overstated. The Engineer is responsible for determining the foundation suitability as it relates to the design intent. That is, the foundation material has to have the minimum material properties required for the structure to behave as the Designer intended. Simple tests can be performed in the field to determine the bearing capacity and verify the suitability of the foundation material. They are discussed in the Caltrans Soil and Rock Logging, Classification, and Presentation Manual and include:
What is the ultimate bearing capacity of soil?
The ultimate bearing capacity of a soil mass supporting a footing foundation is the maximum pressure that can be applied without causing shear failure or excessive settlement. Ultimate bearing capacity solutions are based primarily on the Theory of Plasticity; that is, the soil mass is assumed to be incompressible (does not deform) prior to shear failure. After failure, deformation of the soil mass occurs with no increase in shear (plastic flow).
What is the mode of failure for soils with bearing capacity overloads?
The mode of failure for soils with bearing capacity overloads is shear failure of the soil mass that supports the footing foundation. It will occur in one of three modes:
What is trenching and excavation?
Excavation and trenching are inherent when constructing foundation elements, such as footing foundations. The Caltrans Trenching and Shoring Manual provides information about the complete process for administering, designing and reviewing excavation work and plans. What follows is a brief description of what to consider before excavation.
Why is groundwater important?
The control of groundwater is essential to the stability of a shoring system and the underlying soil intended to support the new foundations. In addition to controlling groundwater to facilitate construction operations, the Engineer also must consider soil heave and piping as they relate to the stability of the bottom of the excavation.
What is a Caltrans trenching and shoring plan?
The Caltrans Trenching and Shoring Manual provides procedures for reviewing and authorizing these plans. An important consideration in shored excavations is the minimum setback for a surcharge when on level ground. The setback usually is equal to the depth of the excavation unless specific surcharge loads are considered in the shoring design. The “Boussinesq” strip load formula is recommended for calculating the lateral pressures due to surcharge. (Figure 4-11). For example, no minimum setback of the surcharge load would be required if the earth support system is designed for the summation of lateral pressures due to the surcharge and earth pressures. However, a barrier should be provided to prevent material from entering the excavation. The Caltrans Trenching and Shoring Manual includes several examples of how this formula is used, and the SC website has a spreadsheet that can be used to calculate the pressures7.
What is subsurface exploration?
Subsurface explorations shall be performed to provide the information needed for the design and construction of foundations. The extent of exploration shall be based on variability in the subsurface conditions, structure type, and any project requirements that may affect the foundation design or construction. The exploration program should be extensive enough to reveal the nature and types of soil deposits and/or rock formations encountered, the engineering properties of the soils and/or rocks, the potential for liquefaction, and the ground water conditions. The exploration program should be sufficient to identify and delineate problematic subsurface conditions such as karstic formations, mined out areas, swelling/collapsing soils, existing fill or waste areas, etc.
Where are footings located?
Footings shall not be located on or within liquefiable soil. Footings may be located on liquefiable soils that have been improved through densification or other means so that they do not liquefy. Footings may also be located above liquefiable soil in a non-liquefiable layer if the footing is designed to meet all Extreme Event limit states. In this case, liquefied soil parameters shall be used for the analysis (see Chapter 6). The footing shall be stable against an overall stability failure of the soil (see Section
What are the Figures 8-8 and 8-9?
Figures 8-8 and 8-9 provide definitions and typical locations of the forces and moments that act on deep foundations such as driven piles. Table 8-8 identifies when to use maximum or minimum load factors for the various modes of failure for the pile (bearing, uplift, and lateral loading) for each force, for the strength limit state.
What is the minimum pile spacing for a bridge?
Center-to-center pile spacing should not be less than the greater of 30 IN or 2.5 pile diameters or widths. A center-to-center spacing of less than 2.5 pile diameters may be considered on a case-by-case basis, subject to the approval of the WSDOT State Geotechnical Engineer and Bridge Design Engineer.
What is a drilled shaft?
Throughout these provisions, the use of the term “drilled shaft” shall be interpreted to mean a shaft constructed using either drilling or casing plus excavation equipment and related technology. These provisions shall also apply to shafts that are constructed using casing advancers that twist or rotate casings into the ground concurrent with excavation rather than drilling. The provisions of this section are not applicable to drilled piles installed with continuous flight augers that are concreted as the auger is being extracted (e.g., this section does not apply to the design of augercast piles).
Can you remove expansive soil?
In general, uplift loads on foundations due to expansive soils shall be avoided through removal of the expansive soil. If removal is not possible, deep foundations such as driven piles or shafts shall be placed into stable soil. Spread footings shall not be used in this situation.
What is seismic design category D?
In buildings assigned to Seismic Design Category D 0, D 1 or D 2, as established in Table R301.2 (1), concrete foundation walls that support light-frame walls shall comply with this section, and concrete foundation walls that support above- grade concrete walls shall comply with ACI 318, ACI 332 or PCA 100 (see Section R404.1.3 ). In addition to the horizontal reinforcement required by Table R404.1.2 (1), plain concrete walls supporting light-frame walls shall comply with the following.
How thick is a masonry foundation?
Masonry foundation walls shall be not less than the thickness of the wall supported, except that masonry foundation walls of at least 8-inch (203 mm) nominal thickness shall be permitted under brick veneered frame walls and under 10-inch-wide (254 mm) cavity walls where the total height of the wall supported, including gables, is not more than 20 feet (6096 mm), provided the requirements of Section R404.1.1 are met.
What is soil test?
Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting or other questionable soil characteristics are likely to be present, the building official shall determine whether to require a soil test to determine the soil's characteristics at a particular location. This test shall be done by an approved agency using an approved method.
How much compressive strength is required for concrete?
The minimum specified compressive strength of concrete, f 'c, shall comply with Section R402.2 and shall be not less than 2,500 psi (17.2 MPa) at 28 days in buildings assigned to Seismic Design Category A, B or C and 3000 psi (20.5 MPa) in buildings assigned to Seismic Design Category D 0, D 1 or D 2.
When should backfill be placed against the wall?
Backfill shall not be placed against the wall until the wall has sufficient strength and has been anchored to the floor above, or has been sufficiently braced to prevent damage by the backfill.
What is permitted in a detached one and two family dwelling?
In detached one- and two-family dwellings that are three stories or less in height and constructed with stud bearing walls, isolated plain concrete footings supporting columns or pedestals are permitted.
How is concrete consolidated?
Concrete shall be consolidated by suitable means during placement and shall be worked around embedded items and reinforcement and into corners of forms. Where stay-in-place forms are used, concrete shall be consolidated by internal vibration.