Category Archive : Shear capacity of pile
The ultimate bearing capacity of a pile is the maximum load which it can carry without failure or excessive settlement of the ground. While calculating pile load capacity for cast in situ concrete piles, using static analysis, we need to use soil shear strength parameter and dimension of pile. The pile transfers the load into the soil in two ways. It depends upon the undrained shear strength of soil and may be obtained from the figure given below. A minimum factor of safety of 2.
The first term is the expression for the end bearing capacity of pile Q b and the second term is the expression for the skin friction capacity of pile Q s. Geotechnical-Material Engineer.
To know more about me just visit AboutMe. Good evening sir. I m Joydip from Assam Guwahati. Sir my question is a dia pile10 metres length. Your email address will not be published. Notify me of follow-up comments via e-mail address. Save my name, email, and website in this browser for the next time I comment. Notify me of follow-up comments by email. Notify me of new posts by email.
The equation given below is used to calculate the ultimate load carrying capacity of pile. Share this:. Joydip das August 5, Reply. Ravi Peddodu December 21, Reply. Can u plz tell me Double tangent method in full description. Please send me how we determine pile capacity using test! Add a Comment Cancel reply Your email address will not be published. Theme by MyThemeShop. Sorry, your blog cannot share posts by email.For a complete version of this document click here. There are numerous types of load bearing piles.
Figure shows a pile classification system based on type of material, configuration, installation technique and equipment used for installation. Load bearing piles can also be classified based on their method of load transfer from the pile to the soil mass. Load transfer can be by friction, toe bearing or a combination. The general category of steel piles includes H-piles and pipe piles. Since steel piles are a manufactured product, their properties are controlled and well known prior to installation.
Among all piling materials steel piles are allotted the highest allowable unit working stresses, but not necessarily the highest in proportion to the ultimate strength of the material. Steel piles are generally considered to be high capacity piles but have been historically used for a wide range of loadings.
Steel H-piles are a specially designed sub-group of wide flange shapes with equal thickness in the web and flanges. The depth of the section is approximately equal to the width. H-piles are hot rolled from ingots on the same type mill used to manufacture wide flange structural shapes. A table of the various sizes commonly available is shown in Table Other wide flange shapes have been used for foundation piles in special situations.
H-piles are very versatile pile type. They can be used for both friction and end bearing applications.
They are manufactured as a finished product, which can be driven with standard equipment. Advantages and disadvantages of H-Piles are shown in Table H-piles can be considered for a design load between 80 kips kN and kips kN. They function most efficiently for end-bearing or partial end-bearing applications.
They are a standard in many states for highway bridge piers and abutments where the job sites are remote, compacted fill approach embankments must be penetrated, battered piles are often required and pile loadings are in the medium to high medium range 80 kips kN to kips kN. H-piles are also commonly applied for high unit dead and live loads associated with multi-story buildings.
The magnitude of these loads generally requires high capacity piles driven to end-bearing conditions to limit settlements and for space and economic reasons. H-piles have carried design loads of over kips kN in a number of such applications.
H-piles are good piles in tension — the constant cross-section together with the entrapment of soil between the flanges provides excellent resistance to pullout when that is a factor. H-piles are used as battered tension piles to anchor sheet pile bulkheads. Uplift due to hydrostatic or wind conditions is an important consideration in many foundation designs, and steel H-piles have the ability to work both as compression and tension piles.
Their low-displacement characteristic would favor H-piles over displacement piles where ground heave might be a problem.
The properties for these specifications and their grades are shown in Table This formulation is a 50 ksi MPa steel with improved corrosion performance in the salt-water splash zone. Experience indicates that corrosion is not a practical problem for steel piles driven in natural soil, due primarily to the absence of oxygen in the soil. However, in fill ground at or above the water table, moderate corrosion may occur and protection may be needed.Your email address will not be published.
Save my name, email, and website in this browser for the next time I comment. Search for:. The column is reinforced with longitudinal bars of 12 No. Complete pile cap design will be illustrated here; except superimposed load weight of pile cap also exerts some load on piles. Lets consider cap weight exerts 3 kips load on each pile. Now what can be punched through pile cap? One is pile itself ; another is column o r columns supported by pile cap.
Should we check both cases? The basis is to have idea about punching perimeter relative to load. If a column is heavily loaded and he selects relatively small size of piles cross-section with more pile, the piles can be punched.
Again if column load is small and relatively greater cross-section of pile is chosen, pile may not be punched. But calculation for punching of column through pile foundation must be checked for all situations. Consider No. Therefore column will also not be punched. But a partial contribution is considered P u divided by fraction outside the critical section. Now we calculate beam shear capacity of pile cap. We know critical section lies at a distance d from face of column figure below.
The critical section lies N ow distance between column face to pile face inside. If all piles lie inside of critical section for beam shear, no shear is considered to produce shear failure in foundation.
Beam shear is often called flexure shear. The critical section is located at the face of column. For each direction there have three piles to contribute to bending moment.Aside from flexural checks, one of the most important points to consider in the design of the pile cap is the Punching Shear Checks.
As we all know, Punching Shear is a concentrated load causing shear stress on the section around the load and this load should be resisted by the structural member from where the concentrated load or the reaction is rested.
In punching shear considerations, there are actually two checks to consider in the design of pile caps. One is the punching shear strength of pile cap due to the concentered load of the column and the other is the shear strength of pile caps due to the reactions of a pile or group of piles.
Punching shear checks should be taken seriously as structural failures due to punching before it occurs leaves a minimal warning or specifically, no warning at all.
As a structural engineer, of course, the safety of the occupants is more important than anything else that is why we need to be very cautious in our design concerning punching shears.
After the geometrical assumptions as tackled in previous article Pile Cap Design Assumptions and Recommendations were made, the design validation using software or manual calculations should be done accordingly.
One of the verifications required is to check if the design thickness is adequate to resist the concentrated load or reactions, if not we need to increase the thickness or provide additional shear reinforcements.
It will show you how to consider the punching shear checks using the SAFE program and the punching shear capacity checks as specified by the ACI code. Perhaps the Punching Shear Check is the last step to consider in the design of the pile cap. Let us take a look at the image below an excerpt from a working model. Supposed we had a SAFE model of pile cap already performed the run analysis.Capacity of Group of Piles, Mumbai University Solved Example
For the member to be adequate in punching shear, the ratio of the actual shear stress divided by the capacity of shear stress should be less than one. If the result says otherwise then, our assumed thickness is inadequate and an increase in thickness is required. Let us take a look at a mm thick pile cap supported with 5 numbers of piles in Figure 1. It is noticed in Figure 2 that the capacity ratios due to pile reactions and column loads are less than 1 then our assumed thickness is adequate in punching shear.
Although there is a separate approach on how to design the punching shears in detailed, we can verify the above SAFE result using the punching shear capacity check. The capacity of pile cap to resist the punching shear can also be check manually according to ACI table The compression force due to column loads and the vertical reaction due to piles in cases of punching check due to column and piles respectively should be less than the value of the following three equations:.
Kindly select the images for more! We would love to hear from you! Share your thoughts on the comment form below.This grade has been satisfactory for most applications in that it provided a relatively high yield point for design and a high ultimate strength for drivability. The formulation is not well respected for weldability, although procedures for welding this grade have been published or are available from the manufacturers. The steel is not particularly tough and fractures originating at notches have been noted, particularly in cold environments.
This steel has a minimum yield point of 39 ksi and a minimum tensile strength of 70 ksi. Higher strength steels for structural applications are available for sheet piling such as the ASTM A series. All strengths may not be available from every manufacturer, however Grade 50 is almost always offered. High strength grades find application 1 to substitute a lighter section of higher strength for a heavier section of regular strength, 2 to maintain safety factors against yield where it cannot be accomplished with section modulus.
High strength grades can maintain some safety factor against yield where corrosion might reduce section properties. High strength steels, are generally more weldable than higher carbon grades. Safety factors for the high strength steels are similar to lower strength grades. It is now available as silicon killed, fine-grain formulation with greatly improved Charpy V-Notch impact properties. This steel might be considered for fracture critical applications, for example, construction in arctic regions and structures subject to impact.
This is a premium priced formulation. ASTM-A Grade was developed to recognize specially formulated steel for sheet and H- piles for use in salt-water applications. This grade has shown advantages over regular carbon steels for resisting corrosion in the salt-water splash zone that is an area of concern. The steel also provides a minimum yield point of 50 ksi and therefore can be designed along the lines of A steels.
In some cases weight can be reduced, thus providing a saving which will pay some of the additional cost of the grade. More discussion of this material is provided in Most steel sheet piling is still designed using allowable stress design methods; thus, a factor of safety is usually specified that reduces the allowable stress in the pile from the yield stress.
The allowable stress is thus. With steel piling in pure bending see belowthere are two reduction factors used:. For static loads, for permanent works the reduction factor is generally 0.Online Deep Excavation and Soil nail wall design Workshop.
Early registration ends soon! Sheet pile design must account for earth, water, and adjacent structures. Sheet pile design can be straightforward in simple cases, and quite complex in some other conditions. Many unknowns and factors that influence the behavior of the sheet pile wall. Typically, there are two systems in sheet pile wall that must be designed: A the sheet pile wall that retains the earth and water etc.
Sheet pile design with our DeepXcav software. The image above shows a sheet pile design with two levels of struts for a cofferdam inside a water body. The AZ48 sheet pile walls are designed to resist bending moments, while the sheet pile design capacity is shown with the red lines next to the bending moment diagrams. Within the image we can also see the structural demand to capacity ratios for the struts and the walls.
These ratios should be kept below 1 for a safe design. In this case, the safety factors must be applied either in the applied earth and water loads or within the structural steel yield strength.
The overall safety factors should be about 1. Sheet pile design can be performed with both traditional and non-linear analysis methods. While it is realized that traditional methods of analysis have obvious limitations in predicting real behavior accurately, they are important for framing the problem and providing a back-check for more rigorous finite element methods. Performing detailed calculations for both systems can be a very time consuming process, especially when parameters have to be changed.
In addition, many current software programs do not offer an integrated platform of structural and geotechnical analyses required to design shoring excavations. As a result, the designer is forced to use numerous software programs to analyze the excavation and the structural system seperately. With the exception of finite element analyses, there are very few theoretical solutions for calculating lateral soil pressures from complex surface profiles.
Furthermore, the designer has to save under different filenames different stages for the same excavation. As a result, the whole process can become unescessarily complicated and time consuming. DeepXcav addresses most of these issues and provides an integrated structural and geotechnical platform for designing deep excavations.
When the sheet pile wall will not experience any axial loads the structural capacity of the pile can be determined from the section modulus and the yield strength of the steel.
Chapter 2 – Structural Design of Sheet Pile Walls
In the case of allowable stresses for temporary structures the allowable moment is typically taken as:. Before all, a designer has to appropriately select the type of lateral earth pressures that are expected to act on the sheet pile. For most sheet pile walls active or at-rest earth pressures are appropriate.
Passive soil resistance should be used with caution.
The possibility of including water pressures has to be considered if sufficient drainage is not provided. In the USA, depending on the design approach, some design codes LRFD apply safety factors that multiply each pressure by a safety factor.
In Europe, a strength design approach is applied where soil strength is divided by safety factors and loads are multiplied according to their nature temporary and permanent.
Each method has its benefits and its shortcomings. External stability checks refer to calculations that represent the overall stability of the shoring system.
Two calculations are typically performed:. When a retaining wall is based on soil the bearing stability tends to be more critical. The first task in this check is to properly compute bearing stresses on the toe and heel of the wall. The reason why bearining stresses have to be computed on both sides is because the overturning causes increased stresses in the toe and reduced stresses on the heel base. The bearing stresses have to be examined againgst the permissible bearing stresses and a minimum safety factor of 3.
Using such a high safety factor typically ensures that wall settlements are kept within acceptable levels.
Chapter 2 – Pile Types and Guidelines for Selection
Otherwise detailed settlement alculations are required if settlement control is critical.Log In. Engineer and international traveler interested in construction techniques, problems and proper design.
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Promoting, selling, recruiting, coursework and thesis posting is forbidden. Students Click Here. Related Projects. It appears that the building used 2' circle open-ended lightly reinforced concrete piles. Plus, any additional information pertaining to the collapse would be greatly appreciated.
Quick I would say not. Even more that you want to use the value as input for a probe even if theoretical into the case. To your purpose, especially if for some real world application, the most accurate soil-structure interaction should be used; but if thinking that thing out of reach, a common structural analysis should not be in any case.
Note that since related to some ruin many other aspects may have ignited the failure and except that you know the contrary is the case shear atop the piles might not be as relevant as say, solid rotation on lack of bearing, a weakened bad detail at the caps, etc I mean, of course with your model you may get some interesting appraisals of what could have happened yet one would have to consider I think a number of concurrent or alternative scenarios to come closer and closer to a correct report.
And I'm sure you wouldn't design the piles to resist the slope failure! An example analysis uses a shear force of kN, but I'm not sure how they calculated that or for what kind of pile. Any thoughts? I think these are spun piles which are common in China.
The first problem is that you are not sure of the diameter, you think 2'. But spun piles are available inand mm diameter plus the wall thickness can be varied to give the required properties. Try looking up "spun pile" on the internet. The initial question referred to the "shear force" of the piles, but obviously the force is induced by the soil, conditions and has no bearing on the properties of the pile itself.
With some familiarity with the massive projects going on concurrently, I would think it is a "cookie cutter" design of similar or identical buildings with the same materials from the same plants within a one year or so period 24x7 construction.
Only an observation.