Blog Archives

Mathematicians and inventors of Alexandria and the Hellenistic world

Posted by on 16/ 11/ 15

In 335 – 331 BC, Alexander the Great conquered the totality of Greece and the Persian Empire, including Egypt and Mesopotamia. The spirits of analysis and hydraulic know­how now were brought together in the same crucible, fueled by the need to innovate – in order to ensure survival in a world whose boundaries were suddenly pushed enlarged, and to increase agricultural productivity to meet the needs of the new ruling classes. This crucible has a name: Alexandria.

Mathematicians and inventors of Alexandria and the Hellenistic world

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Reliability Analysis Considering Load-Resistance Interference

Posted by on 16/ 11/ 15

4.1 Basic Concept

The design of a hydrosystem involves analyses of flow processes in hydrology and hydraulics. In a multitude of hydrosystems engineering problems, uncer­tainties in data and in theory, including design and analysis procedures, war­rant a probabilistic treatment of the problems. The risk associated with the potential failure of a hydrosystem is the result of the combined effects of in­herent randomness of external loads and various uncertainties involved in the analysis, design, construction, and operational procedures. Hence, to evaluate the probability that a hydrosystem will function as designed requires uncer­tainty and reliability analyses.

As discussed in Sec. 1...

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Techniques LOCKING WALLS TOGETHER

Posted by on 16/ 11/ 15

TO TIE JOINING walls together, the double top plate must overlap the top plate at each wall intersection.

1. If you’re nimble, you can perch on top of the framing to hammer overlapping joints together.

2• Otherwise, do the job on a ladder.

3. It’s good practice to drive a toenail (or two) into the overlapping plate. A toenail pulls the joining walls together before the top is nailed off.

Techniques LOCKING WALLS TOGETHER

STEP7 Plumb and Line the Walls

Theword “plumbing,” when used in the con – text of framing a house, means making sure that the walls are standing straight up and down.“Lining’’ means straightening the top plate along the length of each wall. It’s impor­tant that all the walls are plumbed and lined accurately. Anything else is unacceptable.

Badly plumbed or crooked walls cause sig­nificant proble...

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THE EMPIRES OF THE BUILDERS

Posted by on 16/ 11/ 15

For thousands of years, the hydraulic know-how of the East was no more than an oral tradition. But with the conquests of Alexander the Great, this oral tradition comes into contact with the Greek spirit of observation and analysis. The city of Alexandria, at the maritime front door of Egypt, for several centuries serves as the scientific center of the known world. The understanding and know-how of the scientists of the Alexandrian school remain unequalled during the following millenium, both in the East and the West, until the advent of the Renaissance.

Roman engineers, the inheritors of Etruscan and eastern techniques, influenced by the Greeks and endowed with a strong practical sense, leave the influence of their hydraulic achievements around the entire Mediterranean perimeter.

The fall ...

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Pesticide-Treated Lumber

Posted by on 16/ 11/ 15

Although Germany has been a leader in the Bau – Biologie and healthy housing movement, it was only two decades ago that the general public there became aware of multiple chemical sensitiv­ity disorder. This awareness followed the experi­ences of thousands of people who were exposed to lumber treated with both the preservative pentachlorophenol and the pesticide lindane. Hundreds of people developed chronic neurologi­cal complaints, chronic fatigue, and an unusually heightened sensitivity to chemicals that were pre­viously tolerated. Lindane has subsequently been banned in Germany as a wood treatment.

dipped in pesticides that are now banned in the US...

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Health Concerns with Wood Frame Construction

Posted by on 16/ 11/ 15

Wood has historically been used as a compo­nent of a breathing wall system, whether it be the half-timber, wattle-and-daub construc­tions of medieval Europe or the log cabins of our ancestors in North America. (See Divi­sion 4 for an explanation of the breathing wall concept.) Wood is an advantageous material in a healthy home because it has the property of hygroscopicity. This means it has the ability to absorb and release moisture, thus helping to balance humidity levels and the electrocli­mate. However, for many chemically sensi­tive individuals the natural terpenes found in wood, especially soft or aromatic woods such as pine or cedar, are intolerable. Certain woods may need to be eliminated from, or sealed when used in, a home for a chemically sensi­tive person.

In standard home...

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FIREWALLS

Posted by on 16/ 11/ 15

Growing pressures on land availability and housing affordability are resulting in an increase in demand for attached homes. Zero-lot-line configurations are becoming more popular for detached homes because of more innovative use of small lots. The principal added code consideration for attached and zero-lot-line homes is the requirement for fire barriers.

Requirements of the major model codes are not always clear and are often subject to local interpretation and/or amendment. It is important to under­stand that all major model codes have an "Alternate Materials and Systems" section and that local code officials have the discretion to approve alternate construction. Appropriate documentation is, of course, usually necessary.

To be acceptable, firewall construc­tions must be rated by a reco...

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Shoring

Posted by on 16/ 11/ 15

Shoring temporarily supports loads carried by bearing walls while you modify them—say, to add a window or a door opening. Typically, shoring is installed after removing finish surfaces and rerouting pipes and wires but before cutting into a bearing wall. If you’re not sure if the wall is bearing or whether it can be safely modified, have a structural engineer inspect the house and review your remodel­ing plans. This is hard-hat work.

For first – and second-floor walls, two types of shoring are common: screw jacks used with top and bottom plates, and temporary stud walls built from 2x4s. In either case, position shoring back 2 ft. to 3 ft. from the wall you’re working on so you’ll have room to move tools and materials.

► If you’re using screw jacks, doubled 2×6 top plates will distribute...

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SUPPORTING FLOOR JOISTS

Posted by on 16/ 11/ 15

It’s common in many regions to build houses directly on a concrete slab. When this is the case, wall building can begin once the sill plates are down. Other builders use a system of posts and girders to support joists so that a floor can be nailed to them. Still others use manufac­tured joists (called I-joists) that span a basement from sill plate to sill plate without any interior support, leaving a room large enough for a dance hall. [7]
length of the building. Houses fre­quently have an exterior stemwall foundation with girders supported by piers set on concrete footings (see the drawing above).

Post length

Posts in a basement will be quite long, while posts in a crawl space will be shorter—only about 1 ft. to 2 ft...

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