Site-Structural LinkedIn Group

Are you on LinkedIn? There is now a LinkedIn group for Site-Structural Engineering that is intended as a forum for discussing problems, solutions and best practices for interfacing new construction to congested sites in the urban environment. If you are new to urban construction, it is a good place to ask questions, tap into the experience of others and get help with your own site-structural issues.

What’s Wrong with Your Monitoring Plan

Construction, particularly in the urban environment, often exposes nearby structures and facilities to hazards, some of which are difficult to predict precisely and manifest as the work progresses. Impacts of this nature are associated with excavations, tunneling and foundation construction methods, and often require monitoring of potentially impacted structures and facilities. A monitoring program may include a variety of means of observation and measurements, including periodic visual and photographic observations of the work and adjacent properties, survey readings and instrumentation to measure displacement, vibrations, groundwater levels and other phenomena.

Commonly used construction monitoring techniques have been available for over 50 years. Technology has reduced the cost and expanded the options for monitoring programs. In spite of this, the full benefit of construction monitoring is often not realized. Here are a few things that can be wrong with the monitoring program for your project:

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Site-Structural Engineering for the Urban Environment

Having projects in the urban environment representing a large proportion of my career experience, I am always a little surprised when I encounter design professionals and contractors who do not fully appreciate the challenges and constraints associated with building on urban sites. While a lot of design professionals, contractors and other stakeholders have urban project horror stories, they do not necessarily associate those adversities with choices that were made or not made during the project. It is almost as if they believe that nothing can be done.

Perhaps I should not be surprised. The fact is that most of the Architecture, Engineering and Construction (A/E/C) industry is focused outside of the urban cores. In a lot of major metropolitan areas, development has focused on low-density sprawl with large parking lots and generous setbacks. For these projects, consideration of the outside world may be limited to curb cuts and utility connections. Is it any wonder then that designers and constructors underestimate what it takes to build on a constrained urban lot. Continue reading “Site-Structural Engineering for the Urban Environment”

If Your New Neighbor is a Construction Site

Occasional inconvenience from construction is a fact of life, especially for those of us who live or work in an urban area. Depending on how close the construction is to your home or business, the potential impacts might be more significant than traffic delays or noise. Construction projects can cause damage to nearby buildings and infrastructure, requiring risk mitigation, protection and performance monitoring.

Most construction damage is caused by vibration, foundation movement or impacts from striking objects, material or equipment. When new construction and adjacent structures are both built up to the property lines, as is typical in many cities, these risks are increased and additional structural and building envelope issues can occur, especially if the adjacent building once shared a party wall with previous buildings on the construction site. Continue reading “If Your New Neighbor is a Construction Site”

Why the Design Team for Urban Projects Should Consider Support of Excavation

A while back, I looked at a small support of excavation project in a major city that illustrated some of the issues that can arise when excavation support and underpinning are not considered during the design process of an urban project, especially a small urban project.The project involved a horizontal addition to an attached single-family dwelling: a very typical project type in cities, and about as simple as new construction can get in the urban environment. However, the existing basement was to be extended below the addition, requiring several feet of excavation on a small site with impacted abutting properties on two sides. Consequently, support of excavation would be required, unless the neighbors would be willing to lose the use of their backyards during construction.

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Engineering Like a Historian

One of the fundamental ways that construction in the urban environment is different from building elsewhere is the potential to damage adjacent structures. This risk becomes significant when adjacent structures are older and abut the lot lines, especially if those structures shared party walls with demolished buildings formerly on the project site. This scenario often requires measures to protect the adjacent structure from foundation movement, moisture infiltration and falling objects, among other hazards. Managing the risk to these adjacent structures requires an understanding of how they were built and how they behave structurally. However, drawings of these building are usually not available, if they ever existed. Further, it is often not feasible to thoroughly investigate these structures due to the cost involved and the fact that adjacent owners typically will not permit invasive explorations. Continue reading “Engineering Like a Historian”

Pre-Construction Surveys Should Not be a Commodity

One of the most common tools for managing risk associated with construction adjacent to existing structures is the pre-construction condition survey. In some circumstances, pre-construction surveys are required by law under building codes and they are typically required by contract on most large projects. However, pre-construction condition surveys are often procured as a commodity service. Consequently, a lot of pre-construction condition surveys are executed poorly and fail to provide the intended risk management benefit. Continue reading “Pre-Construction Surveys Should Not be a Commodity”

What a Building Owner Should Know About Underpinning

An environmental consultant I know once showed me a photograph of a deep excavation he had visited on a site tour. The excavation had required underpinning of a couple of brick, bearing wall buildings on the lot lines. Underpinning is the term applied to a variety of methods used to resupport a structure’s foundation, usually to a deeper bearing depth. Generally, underpinning is performed if the foundation system for an existing structure is compromised or if foundation support needs to be transferred to a deeper level to allow work that would otherwise cause foundation movement and damage to the structure. The latter scenario is common when a new building is built adjacent to an existing one.  Owners of buildings that are to be underpinned as part of adjacent construction need to know what is involved. Underpinning by a third party constructor carries with it technical and legal implications and exposes the owner to risk that may not be managed by the adjacent construction project owner and their contractors and professionals in a manner optimal to the building owner.

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