An Economical Solution for Non-Ductile Frames

Many older buildings include columns that require strengthening. Several scenarios could cause this. In coastal regions and aggressive environments, for example, the corrosion of reinforcing steel results in loss of capacity of the columns. In other cases, the poor quality control during the original construction may have resulted in low compressive strength in the concrete. The author has been personally involved with the retrofit of two such buildings in Florida, where the concrete compressive strength has been below 1500 psi, only a fraction of the strength specified in the design documents. Some of the collapsed Champlain Tower investigations in Surfside, Florida, have also mentioned the “powder-like” concrete in the columns as a potential contributing factor to that failure.

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Building codes and standards are typically enacted in response to hazardous situations that threaten public health, safety, and welfare, or to natural disasters such as floods, fires, and earthquakes. Fire protection was the first major issue leading to the establishment of early building codes in the United States. In 1896, the National Fire Protection Agency (NFPA) was founded to establish uniform sprinkler standards for the mills and warehouses in the Northeast. First published in 1897, NFPA standards were used until the 1950s. Modern structural related building codes were first introduced in the United States around 1900 in cities such as New York and Chicago.

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Part 2

This is the second of two articles discussing high-level design considerations of prestressed concrete girders. Part 1 (STRUCTURE, January 2021) provided an overview of the post-tensioning and pretensioning processes, described the common materials used in constructing prestressed bridge girders and discussed the time-dependent prestress losses inherent in their design. The discussion continues in Part 2 with fundamental design considerations for internal stress distributions within prestressed concrete girders and the methodology for application.

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Part 1

The ability to premanufacture elements helped to proliferate concrete as an essential building material. Rectangular blocks, for example, could be manufactured rapidly and easily transported to make many types of structures, from steps, sheds, and buildings to intricate tunnels, aqueduct systems, and bridges. These emerging technologies and the infrastructure they enabled have continually reshaped the way communities are organized through more efficient transportation of people and goods. The next step in the evolution of precasting concrete is prestressed concrete. This article discusses some of the technologies and materials that make modern prestressing techniques achievable. …

Part 4: Demolition Special Inspection and Post Demolition Assessment

This four-part series (Part 1, STRUCTURE, November 2019, Part 2, January 2020, Part 3, April 2020) discusses how the collapse of a building during a demolition operation in Philadelphia in 2013, which resulted in several fatalities, led to the enactment of a City Ordinance to prevent similar future calamities. …

It is common in Florida to elevate homes on wood piles in coastal zones A and V. Many of those homes are adjacent to the Atlantic Ocean, the Gulf of Mexico, bays, estuaries, and other bodies containing saltwater. Most of the piles are sheltered under habitable space. Reacting to its environment, the wood has a fuzzy appearance. Why would a wood pile, driven on land or near a body of water, deteriorate at the protected and dry top and not at ground level or the waterline? To understand the cause of “fuzzy wood” and to provide an appropriate repair, we need go back to high school biology and chemistry classes. …

Part 3: Adaptive Reuse Feasibility Analysis

This four-part series (Part 1, STRUCTURE, November 2019, Part 2, January 2020)  discusses how the collapse of a building during a demolition operation in Philadelphia in 2013, which resulted in several fatalities, led to the enactment of a City Ordinance to prevent similar calamities. As a result of the Ordinance, the author became involved with the structural investigation, review of the Site Safety Demolition Plan, and Demolition Special Inspections associated with the adaptive reuse of the Apex Hosiery Company Building located in Philadelphia. …

When Reroofing Requires a Lateral Analysis

Since its inception in 2003, the International Existing Building Code (IEBC) has contained a provision that triggers the evaluation and possible retrofit of roof diaphragms when certain buildings are reroofed. This provision has gradually evolved within the Work Area Method, unnoticed by some practitioners and readily avoided by others by reverting to the International Building Code (IBC) Chapter 34, Existing Buildings and Structures, or by using the Prescriptive or Performance Methods within the IEBC. …

Man has been building timber structures throughout Europe and Asia for over 4,000 years. In North America, timber structures have been built since the first Europeans arrived 400 years ago. Consequently, there are thousands of old timber structures still in service. …