Nestle Cabuyao Egron Building

This is another project with numerous revisions. I finished this first around mid-2008.

Scope:

New equipments within Egron Building
Additional Access left of the building

Things I've learned:

1. Retrofitting of existing concrete columns/girders can be done by:
a. providing 45 degree - knee braces
b. providing diagonal knee braces
c. providing vertical knee braces
d. providing vierendeel trusses
e. providing intermediate steel beams

2. There are instances where I was asked to "release" the ends of overstressed girders (considered hinge) as "it will develop a plastic hinge when loaded" as per my boss. I researched over the net about plastic hinge:

"In structural engineering beam theory the term, plastic hinge, is used to describe the deformation of a section of a beam where plastic bending occurs.

Plastic behaviour
In plastic limit analysis of members subjected to bending, it is assumed that an abrupt transition from elastic to ideally plastic behaviour occurs at a certain value of moment, known as plastic moment (Mp). Member behaviour between Myp and Mp is considered to be elastic. When Mp is reached, a plastic hinge is formed in the member. In contrast to a frictionless hinge permitting free rotation, it is postulated that the plastic hinge allows large rotations to occur at constant plastic moment Mp.
Plastic hinges extend along short lengths of beams. But detailed analyses have shown that it is sufficiently accurate to consider beams rigid-plastic, with plasticity confined to plastic hinges at points. While this assumption is sufficient for limit analysis, finite element formulations are available to account for the spread of plasticity along plastic hinge lengths[2].
By inserting a plastic hinge at a plastic limit load into a statically determinate beam, a kinematic mechanism permitting an unbounded displacement of the system can be formed. It is known as the collapse mechanism. For each degree of static indeterminacy of the beam, an additional plastic hinge must be added to form a collapse mechanism." (Wikepedia.org)

3. Overstresses up to 3.0 on footings can be accepted but with risks involved. Damage can be rapairable. Also, diagonal braces can be placed throwing the column loads on nearby footings and release the column with diversion braces. Columns can also be assigned as "hinged" by making the existing column to baseplate connection as "hinged"

4. Overstresses up t0 1.25 on concrete columns and girders were accepted. Better use 1.2.

Nestle Pulilan Ice Cream Plant

It's been a long time since my last post. Well, I have been busy with the numerous revisions in my recent project - NPI Pulilan Ice Cream Plant. Now, it's almost finish and and I just need to revise few things and include the piperacks.

Things I've learned while doing the design:

1. Increase in roof height of 2.0m (from el. 6.4m to 8.4m) increases wind loading by about fifty percent. New roof trusses and truss retrofitting are smaller considering the 6.4m height than the 8.4m.

2. Retrofitting top chords without roof raising can be done by providing L-plates forming a box with the angular or wt top chord.

3. Use stitch welds for cover plating the whole length of top chord as continuous weld will cause warping of members. (50mm @ 150mm o.c.)

4. When using rafters instead of trusses, the edges can be tapered by maximum 600mm.

Retrofitting of Existing Building

It's been a while since my last post. I have been busy with a huge project which involves a lot of retrofitting works. It is

Determining the Quality of Backfill Compaction

This post is regarding "Determination of Quality of Backfill Compaction" underneath existing pavements/slabs on grade. The needed properties/parameters are as follows:

1. Subsurface Soil Exploration (SPT Nvalues of underlying soils)

2. Navfac 7.1 for correlation charts

3. Soils in Construction by W.L. Schroeder for correlation charts

4. Effective stress at level in question

To determine the quality of backfill compaction, the effective stress at level in question should be computed using the formula Po = γh (for unsaturated soil). Note that effective or submerged unit weight (γ-9.81kN/cu.m.) must be used if the water table is within the height or depth in question. γ is the unit weight of soil and h is the depth in question.

After obtaining the effective stress, refer to the example on the left for SPT=3 BPF and Effective stress = 36 kPa (0.751ksf) at -2.0M. The chart below is taken from Navfac 7.1 to determine Relative Density.

Relative Density are commonly used for cohesionless soils. It is defined as:

Relative density is a dimensionless ratio of the densities of two materials. The term specific gravity is similar, except that the reference material is water. A relative density can help quantify the buoyancy between two materials, or determine the density of one "unknown" material using the "known" density of another material. Mathematically, relative density is expressed as:

where G is the relative density, and ρ is the densities of the two materials in the same units (e.g., kg/m³, g/cm³). (http://www.wikopedia.org/)

It is shown in the figure above that the Relative Density is equal to 15 %. This value will be used in determining the Relative Compaction, RC using a correlation from "Soils in Construction" by W.L. Schroeder as shown on the right.

Projecting the value of relative density down to the line of relative compaction will give the value of relative compaction. In this expample, it is 84%. Thus, the very low RC represents little or no compactive effort.

Design of Reinforced Concrete Silo

Oh well, a new project assigned to me.. actually it was already assigned to me months earlier and right now we received the NTP. I am supposed to do it while I'm doing the Uniliver Bars Area Analysis.

Design of Reinforced Concrete Silo:

References:
ACI Manual of Concrete Practice Part 4
Structural Engineering Handbook

Resources:
Staad Pro 2003
Mathcad 2001 or Mathcad 13

I am currently on the "research" part of the project. I have just finished reading the section in ACI Manual regarding the design of concrete silos.

Few definition of terms (from ACI Manual of Concrete Practice:

1. SILO - Any upright container for storing bulk granular material
2. Hopper - Sloping-walled portion at the bottom of the silo; independent shallow silo (bunker) with sloping walls
3. Stave silos - Silos assembled from small precast concrete units called "staves", usually tounged & grooved, and held together by exterior, adjustable steel hoops

.. construction procedures ( I have never heard these terms before.. maybe because I am not a site engineer.. but of I am supposed to know these stuffs)..

4. SLIPFORMING - construction method in which the forms move continuously during the palcement of concrete; continuity in operation to minimize formation of construction joints; used in casting walls of great height
5. JUMPFORMING - construction method in which fixed forms are used to cast a short increment of height and are then loosened and raised to a higher position after the concrete has hardened; concrete placement not continuous

Others:
6. Homogenizing silos - Silos in which air pressure is used to mix dust-like materials

There are lot of formulas involved and I will not be posting it. It is all in the ACI concrete manual anyway.

So far, all I have are basic understanding on this Silo design. I do expect to know more..

Uniliver Bars Area

Unilver Bars Area Project - This project was handed over to me as the original engineer assigned to do the project left the company.

I am currently reviewing the drawing fiels provided by the client and the area is relatively "huge". I can say that this is the biggest (with reference to area) I have handled so far.

I do expect a lot of difficulties while doing this project. Oh, well, I am very optimistic that I will be able to push this through.

The area by the way is inside Unilever plant. Bars area - well it is where they manufacture the "Surf" bars that are being sold here in the Philippines. It is an existing building that was affected by a recent earthquake (Intensity 4.0) that happened here in Manila. I am not very particular yet with the other details but will posts as soon as I discussed it with my boss.