What We Need is a Light Trailer

In 1967 Vulcan opened a fabricating facility in West Palm Beach, Florida. Across the street from our new plant was “U and Me Transfer and Storage,” (see photo above) which we hired to move a lot of our machinery. We sent one of our supervisors to Florida to help set the shop up. The shop foreman in Florida told the Tennessee man that “U and Me would move this in,” and “U and Me will deliver this tomorrow,” and so on. Finally the Tennessee man threw his hands up in exasperation and asked, “When’s You and Me going to have to time to do all this?”

The plant was formally called the “Special Products Division;” one of those special products was a light trailer, also shown above. This is useful if you want to do construction work at night; just set it up, turn on the generator, turn on the lights and work. In the U.S., with the problems of doing road construction during the day, these handy devices get a workout while crews attempt to repair or rebuild our roads at night.

560-stack-outsideBack in Chattanooga, the company’s main product line went on, which was building pile drivers, many for the offshore oil industry. These machines are most easily put together vertically; you put the base on the ground, stack the ram and the columns on top, then the cylinder, tie the hammer together, lay it down on a flat bed truck and ship it (the stacking is shown at the right.) Because the hammers got so big, we did a lot of this outside, using truck cranes.

One evening we were stacking yet another hammer for shipment. It got dark; the truck was waiting for us, there was no question of waiting until the morning. The supervisor got the light trailer out, fired it up and turned it on so the men could see what they were doing and finish up. Unfortunately the plant was in a residential area. When we turned the lights on, the residents didn’t like it, so they started shooting at the plant. Needless to say, our employees and the poor truck driver found it hard to work with bullets whizzing past them.

Most residential areas like some additional light, but there are always exceptions, and obviously this was one of them. Unfortunately many people and areas don’t like the light being shined on them–any kind of light.

“…though the Light has come into the world, men preferred the darkness to the Light, because their actions were wicked. For he who lives an evil life hates the light, and will not come to it, for fear that his actions should be exposed…” (John 3:19-20)

In a world where privacy is evaporating, people still don’t like their deeds to be known. In some cases this is due to the shifting sands of our legal systems; what is okay one day is punishable by life imprisonment the next. But much of our aversion to the light is because we know that what we are doing is wrong, legal or not. We make excuses like “I’m not a bad person,” not really understanding what that means or how it might be fixed if we are in fact a bad person. We know we are hurting others–we know we are hurting ourselves–but our main motivation is not to get caught, not to have the light shined on our deeds.

“But he who acts up to the truth comes to the light, that his actions may be shown to have been done in dependence upon God.” (John 3:21)

Our God doesn’t need to turn on his light trailer to find out what’s going on in our lives and in our selves; he has “night vision” so to speak, and he knows what we are doing even if no one else does. But he doesn’t want us to just go on in the darkness until we stumble and break our neck. “Jesus again addressed the people. ‘I am the Light of the World,’ he said. ‘He who follows me shall not walk in darkness, but shall have the Light of Life.’” (John 8:12) It is his desire that we walk in his light and live in his love. Just as we used a light trailer to do our work outside the plant, so if we have Jesus Christ in our lives we can live as God’s child even under less than ideal circumstances.

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Inverse Method for Pile Dynamics Using a Polytope Method: IFCEE 2018

vulcanhammer.net

This paper–which is part of the STADYN project–was presented at the IFCEE 2018 conference in Orlando, FL, 7 March 2018. The slide presentation for the paper is below.

The preprint for this paper can be found at ResearchGate.

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New Version of TAMWAVE Online Wave Equation Program Now Available

vulcanhammer.net

The completely revised TAMWAVE program is now available.  The goal of this project is to produce a free, online set of routines which analyse driven piles for axial and lateral load-deflection characteristics and drivability by the wave equation. The program is not intended for commercial use but for educational purposes, to introduce students to both the wave equation and methods for estimating load-deflection characteristics of piles in both axial and lateral loading.

We have a series of posts which detail the theory behind and workings of the program:

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TAMWAVE 7: Analysis for a Cohesive Soil

vulcanhammer.net

With the analysis of the concrete pile in cohesionless soils complete, we turn to an example in cohesive soils.

The analysis procedure is exactly the same.  We will first discuss the differences between the two, then consider an example.

Differences with Piles in Cohesive Soils

  • The unit weight is in put as a saturated unit weight, and the specific gravity of the soil particles is different (but not by much.)
  • Once the simulated CPT data was abandoned, the “traditional” Tomlinson formula for the unit toe resistance, namely $latex q_t = N_c c $, where $latex N_c = 9 $, was chosen.
  • The ultimate resistance along the shaft is done using the formula of Kolk and van der Velde (1996).  This was used as a beta method, for compatibility with the method used for cohesionless soils.  Unless the ratio of the cohesion to the effective stress is constant, the…

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TAMWAVE 6: Results of Wave Equation Analysis

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With the data entered for the wave equation analysis, we can now see the results.  There’s a lot of tabular data here but you need to read the notes between it to understand what the program is putting out.  If you are not familiar at all with the wave equation for piles, you need to review this as well.

General Output for Wave Equation Analysis
2018-01-06T10:13:03-05:00
Time Step, msec 0.04024
Pile Weight, lbs. 15,000
Pile Stiffness, lb/ft 600,000
Pile Impedance, lb-sec/ft 57,937.5
L/c, msec 8.04688
Pile Toe Element Number 102
Length of Pile Segments, ft. 1
Hammer Manufacturer and Size VULCAN O16
Hammer Rated Striking Energy, ft-lbs 48750
Hammer Efficiency, percent 67
Length of Hammer Cushion Stack, in. 16.5
Soil Resistance to Driving (SRD) for detailed results only, kips 572.7
Percent at Toe 35.39
Toe Quake, in. 0.220
Toe Damping, sec/ft 0.07

For those familiar with the…

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TAMWAVE 5: Wave Equation Analysis, Overview and Initial Entry

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With the static analysis complete, we turn to the wave equation analysis.  TAMWAVE (as with the previous version) was based indirectly on the TTI wave equation program.  Although the numerical method was not changed, many other aspects of the program were, and so we need to consider these.

Shaft and Toe Resistance

Most wave equation programs in commercial use still use the Smith model for shaft and toe resistance during impact.  Referencing specifically their use in inverse methods, Randolph (2003) makes the following comment:

Dynamic pile tests are arguably the most cost-effective of all pile-testing methods, although they rely on relatively sophisticated numerical modelling for back-analysis. Theoretical advances in modelling the dynamic pile-soil interaction have been available since the mid-1980s, but have been slow to be implemented by commercial codes, most of which still use the empirical parameters of the Smith (1960) model. In order to allow an appropriate…

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TAMWAVE 4: Shaft Resistance Profile, ALP and CLM2

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With the basic parameters established, we can turn to the static analysis of the pile, both axial and lateral.

Shaft Resistance Profile

Shaft Segment Properties
Depth at Centre of Layer, feet Soil Shear Modulus, ksf Beta Quake,inches Maximum Load Transfer, ksf Spring Constant for Wall Shear, ksf/in Smith-Type Damping Constant, sec/ft Maximum Load Transfer During Driving (SRD), ksf
0.50 48.4 0.163 0.0022 0.009 4.03 45.394 0.009
1.50 83.9 0.163 0.0038 0.027 6.99 19.911 0.027
2.50 108.3 0.163 0.0050 0.045 9.02 13.572 0.045
3.50 128.1 0.163 0.0059 0.063 10.68 10.543 0.063
4.50 145.3 0.163 0.0067 0.081 12.11 8.730 0.081
5.50 160.6 0.164 0.0074 0.098 13.38 7.509 0.098
6.50 174.6 0.164 0.0080 0.116 14.55 6.623 0.116
7.50 187.6 0.164 0.0086 0.134 15.63 5.948 0.134
8.50 199.7 0.164 0.0091 0.152 16.64 5.414 0.152
9.50 211.1 0.164 0.0097 0.170 17.59 4.980 0.170
10.50 222.0 0.164 0.0102 0.188 18.50 4.618 0.188
11.50 232.3 0.164

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TAMWAVE 3: Basic Results of Pile Capacity Analysis

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With the soil properties and lateral loads finalised, we can proceed to look at the program’s static results.  These are shown below.  We will concentrate on cohesionless soils in this post; a sample case with cohesive results will come later.

Pile Data
Pile Designation 12 In. Square
Pile Material Concrete
Penetration of Pile into the Soil, ft. 100
Basic “diameter” or size of the pile, ft. 1
Cross-sectional Area of the Pile, ft2 1.000
Pile Toe Area, ft2 1.000
Perimeter of the Pile, ft. 4.000
Soil Data
Type of Soil SW
Specific Gravity of Solids 2.65
Void Ratio 0.51
Dry Unit Weight, pcf 109.5
Saturated Unit Weight, pcf 130.5
Soil Internal Friction Angle phi, degrees 32
Cohesion c, psf
SPT N60, blows/foot 20
CPT qc, psf 211,600
Distance of Water Table from Soil Surface, ft. 50
Penetration of Pile into Water Table, ft. 50

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TAMWAVE 2: Modifying the Soil Properties

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With the first step out of the way, we can proceed to the second: allowing the user to modify the properties of the soil.  This option must be used with care since it is easily possible to put together a set of soil properties that is physically unrealistic if not impossible.

Also, if you have chosen a sand or clay, you have chosen the methodology you will use.  Adding cohesion to a sand or gravel, for example, will have no effect on the subsequent performance of the model.

Finally, depending upon the choice of a free or fixed head, you are given the option of entering lateral loads and/or moments for the pile head.  In this case we have opted to add a lateral load of 10 kips to the pile and no moment.  The default is zero for both load and moment; this will produce some coefficients but…

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TAMWAVE 1: Entering Basic Soil and Pile Properties

vulcanhammer.net

With a few preliminaries out of the way, we can proceed to discuss the new TAMWAVE routine, which can be found here.

What is TAMWAVE?

TAMWAVE stands for Texas A&M Wave Equation.  The TTI wave equation was developed at Texas A&M in the late 1960’s and early 1970’s, and was a successor to Smith’s original wave equation program.  In reality this is more than a wave equation program; it is a driven pile analyser which, in addition to the wave equation program, analyses the static performance of a driven pile for both axial and lateral loads.  It is not intended to be used on actual projects, but as an educational tool for students.  Most of the software in current use is expensive, and predecessors such as SPILE, WEAP87 or COM624 are hard to use (they’re DOS programs) or methodological obsolescence issues.  (With WEAP87, there are not as…

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