03 00 00 Concrete

Category Archives: 03 00 00 Concrete

Using UHPC to improve box-beam bridge performance

Pouring ultra-high-performance concrete (UHPC) for longitudinal joints—the material could offer new benefits in box-beam bridge design and construction. Images courtesy Ohio University’s Russ College of Engineering and Technology

Out of the many types of bridges used across the country, adjacent prestressed, concrete box-beams have become popular for short and medium spans. Since these bridges are cost-effective, fast to construct, and easy to design, they are preferred by many state and local agencies. Currently used in about two-thirds of the country, many of these bridges are now approaching the end of their life span. Ultra-high-performance concrete (UHPC) could offer game-changing advances for this type of structure.

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Specifying Structural Framing Systems

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Many factors come into play when designers specify structural framing. There are so many criteria, sometimes there is no absolute answer as to which framing system would perform best. At the same time, the interests of various parties must be served, meaning the final selection does not always rest with the structural engineer.

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Epoxy types: A guide for specifiers

Ideally, a bonded anchor should be installed into concrete of known compressive strength. Engineers who specify epoxy anchors also specify the compressive strength to ensure the epoxy can achieve its published bond strength.  If the compressive strength or overall integrity is unknown, they sometimes require field testing of the embedded anchor to determine if the concrete is good enough. Photos courtesy MiTek Builder Products

by Martin Ruch and Jim Collins, PhD, PE

Epoxy types vary widely, and specifiers need to note such attributes as nozzle time, gel time, load time, sag, cure time, and chemical resistance—each property will affect what makes the product ideal for the intended application. When searching for the proper epoxy to specify, it is important to note there are three general classes—pure epoxy, polyester resins, and epoxy acrylates—that break out in different ways with respect to properties and performance.

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Bearing Pad Durability in Precast Concrete Garages

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Bearing pads are used widely in precast concrete parking garages. They function as buffers between the separate concrete members to prevent damage and facilitate movement (much like cartilage between bones at joints). Bearing pads should last for the design life of the structure, but need to be replaced when they are not sufficiently durable. The ‘surgery’ to replace the pads properly is a complex operation, with few published guidelines.

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Specifying More Resilient Buildings

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Resisting natural disasters and reducing environmental impacts are major challenges in the United States. During an average year, there are 10 tropical storms (six of which become hurricanes) and more than 1200 tornadoes touching down. In South Florida, Hurricane Andrew left a wake of destruction in 1992 that totaled more than $25 billion in property damage and resulted in 44 fatalities.

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