Basic Principle of Prestressing

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The classic everyday example of prestressing is this:  A row of books can be lifted by squeezing the ends together: The structural explanation is that the row of books has zero tensile capacity. Therefore the ‘beam’ of books cannot even carry its self weight. To overcome this we provide an external initial stress (the prestress) which compresses the books together. Now they can only separate if the tensile stress induced by the self weight … Read more

Advantages of Prestressed Concrete

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The main advantages of prestressed concrete (PSC) are: Smaller Section Sizes Since PSC uses the whole concrete section, the second moment of area is bigger and so the section is stiffer:     Smaller Deflections The larger second moment of area greatly reduces deflections for a given section size.   Increased Spans The smaller section size reduces self weight. Hence a given section can span  further with prestressed concrete than it can with ordinary reinforced concrete.   Durability Since the entire section remains in compression, no cracking of the concrete can occur and  hence there is little penetration of the cover. This greatly improves the long-term durability  of structures, especially bridges and also means that concrete tanks can be made as watertight  as steel tanks, with far greater durability.

New Orleans Condo Kitchen Renovation

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Since the kitchen cabinets fit exactly in the space available (with no soffit, trim molding, nor fillers) the rough framing and drywall had to be square, level and plumb. Hal Collums Construction implemented designer John Chrestia’s vision for the renovation of a New Orleans warehouse district condo. A kitchen renovation was included in the project, … Read more

Foamed Concrete Application and specification

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Which this paper aims to summarise.Although foamed concrete was used some 2000 years ago it wasn’t until recently that modern foamed concrete began to be developed. In 1987 a full scale trial on the use of foamed concrete for trench reinstatement was conducted in the UK, which led to a further increase in use in … Read more

Highrise Building Failure

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House of CardsOn 16th May, 1968, Mrs Ivy Hodge, a council tenant in a block of flats called Ronan Point in east London, wandered into the kitchen of her 18th floor flat. She leaned over her cooker and struck a match. Instantly, an explosion blew out the pre-cast concrete panels which formed the side of … Read more

2040 Market Street in Philadelphia

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The existing building at 2040 Market Street in Philadelphia, formerly the headquarters for the American Automobile Association (AAA), sat vacant through the “Great Recession” of 2008–2009, providing a constant reminder of the dismal economy. Several developers reviewed the possibility of adapting the building for new use, and eventually PMC Property Group of Philadelphia decided to … Read more

City of Hamilton

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The Hamilton Downtown Multi-Residential Property Investment Program (HDMRPIP) application for the redevelopment of 150 Main Street West was submitted by 150 Main West Holdings Inc. (Darko Vranich), the registered owner of the property. The applicant proposes to develop 142 condominium units with commercial space at the first and second levels of the existing seven (7) … Read more

The Avalon West Chelsea Update

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The Avalon West Chelsea has risen very quickly over the past month, though the project’s 30-story ‘tower’ is not yet obvious. The building is somewhat imposing when viewed from the High Line, but—fortunately—the ‘high-rise’ component will be adjacent to Eleventh Avenue. Judging the project’s lone rendering, it does seem that the mid-rise portion has topped-out.  529 West … Read more

Family House in Village

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The family house is located in Český ráj, an 18,000-hectare nature reserve also known as Bohemian Paradise, and the house nestles against a hillside blanketed with grass. Stempel & Tesar tunneled down into the landscape to make room for a sauna that had been requested by the client. “We decided to add a basement rather than … Read more

DECK STABILITY

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The requirement for diagonal bracing when a deck is greater than 2 feet above grade is applicable to both free- standing decks and decks supported by a ledger. If the deck is attached to the house an alternative to knee braces for deck stability is installation of decking at a 45 degree angle to the deck joists. Decks are stiffer … Read more