Lateral Loading on Piles

For piling foundation, the lateral force on the pile head is resisted by the surrounding soil.

Simplified calculation can be carried out in accordance with recommendation by Tomlinson, M.J..
On the other hand, the pile and the surrounding soil could be modelled as frame elements with soil spring supports (ie. subgrade reaction method).

The soil spring could be determined in accordance with Figure 9 of Geoguide 1 (2nd Edition) published by Geotechnical Engineering Office (GEO). The spring constant (k_sj) is given by

k_sj = n_hz_jDz_j,

where
n_h = Constants of horizontal subgrade reaction
z_j = Depth of spring
Dz_j = Length of pile served by spring

Hence we can observed that the soil spring is depended on (i) n_h value of the soil; (ii) depth of soil spring; and (iii) distance between soil spring. It shall be noted that the value of soil spring is independent of the pile dimension. Typical value of nh value can refer to Table 6.11 of GEO Publication No. 1/2006- Foundation Design and Construction (2006) .

The reaction on the surrounding soil is assumed to be within the soil capacity, provided that maximum deflection of the pile/ surrounding soil is within 25mm.

The model can be carried out by linear analysis as the piles are surrounded by soil in all direction. If sheet piling/ pipe piling are analyzed with soil spring, non-linear analysis is required such that the soil element on the un-excavated side could only take up compression.

Soil Parameter

Soil Properties

The design for foundation and ELS works require some soil parameter like c’ (cohesion) and f’ (angle of shearing resistance) .

The soil parameters could be determined by triaxial compression test of soil sample obtained in ground investigation work.

Mohr’s Circle Diagram for different soil sample shall be as follow:

The triangles formed by the Mohr’s Circle shall be similar.

i.e q_i / (p_i + c’/tan f') = sin f’= constant
or q_i = p_i sin f’+ c’ cos f’

Hence, for same type of soil, a "p-q" graph can be plotted based on the laboratory test result, where p = (s₁ + s₃)/2 and q = (s₁ - s₃)/2.

We could then obtain the best fit curve for the data in form of q_i = mp_i + b. The soil parameters are then determined by f’= sin^-1 m and c’ = b/ cos f’

Weld

Welding connection between steel members could take up axial tension, shear and bending moment.

For fillet welds, the connection strength depends on the weld thickness.

In general, the welds in the flanges are used for resisting bending moment and welds in the web are used for resisting shear.

The following is a example for checking of weld strength for a UB section:

As-built Drawings from BD

In the past, if you want to obtain the record plan from the Buildings Department, you have to fill in the Appendix of PNAP110 and return the Form to 13/F of the Buildings Department's office.

In January 2009, BD has launched online system BRAVO which allow the public to access the record plan system.

In order to view the list of record plan for a specific site, you have to pay $36 first. The BRAVO system does not allow copying and screen capture for the drawings. You have to pay for printing of the record plan.

However, you could in fact save the record plan (in tiff format) to your local computer.

The BRAVO system use viewone to view the record plan. The temporary files will save at c:\user\Your_Username\Viewone\cache

The BRAVO system has disabled the copy & paste function of Window System. In order to save the files, you have to zip the record plan into zip file and then MOVE the file to other folders.

For viewing calculation, you can press "F3" in order to save all pages at the same time.

However, you need to decode the ".tif" files by a small programme "decode.exe" with the following command in DOS mode:
"decode OLD.tif NEW.tif"

You may use batch file if you wish to decode many files.
This trick can really help you saving a lot of money.

Beam Opening

Very often, openings in beam are required to allow the passing through of E&M Services.

The addition of beam openings will impair strenght of the beam. General recommendation for size and location of beam opening could be found in PANP 230 published by the Buildings Department.

If large opening is required, the beam opening shall not be located near concentrated point load and the strength of the beam shall be checked as following:

(1) Global Check

(i) Determine the design moment(M) and shear(V) at the opening location.

(ii) Check if the opening will be extruded into the compression zone of the section.

(iii) If the whole opening is located within the tensile zone, then only local checking is required. Othrwise, the moment capacity of the reduced section shall be checked.

(2) Local Check

(i) The upper chord and lower chord of the opening will take up shear in accordance with their stiffness (ie, their height h₁ and h₂).

(ii) Shear of upper chord, V_up = V x h₁/ (h₁ + h₂) and Shear of lower chord, V_low= V x h₂ / (h₁ + h₂)

(iii) The Design Moment for Upper Chord, M_up = V_up x L/2, where L = width of opening. Similarly, the Design Moment for Lower Chord, M_low = V_low x L/2

(iv) Design the upper chord and lower chord with M_up, V_up, M_low and V_low.