David Freed , GNCB Geotechnical department head, recently attended an informative one-day geotechnical workshop on the Connecticut Valley Varved Clay (CVVC). About 60 geotechnical professionals attended the workshop, sponsored by the Connecticut Society of Civil Engineers , which was held at the University of New Haven. Dr. Stanley Bemben - consultant, former UMASS professor, workshop organizer, and primary speaker - put together a team of seven speakers from the university and design professional environment to address topics on geologic aspects, characteristics and behavior, the “cementation” phenomenon, construction aspects. Several case studies were presented as well.
The CVVC deposit, which ranges up to about 100 ft. thick, is a direct result of the yearly deposition of alternating thin layers of silt and clay within the former Lake Hitchcock. This glacial lake, which is reduced in size and now approximately aligns with the Connecticut River, extends from about Hartford CT to the northern USA/Canada border. A clay and silt layer represent one year’s cycle of time; the number of cycles, much like the rings of a tree, are studied to provide a realistic estimate of the age of the deposit. The surface of the clay is stiff (desiccated crust), a result of exposure to drying once the lake was drained, however the majority of the deposit is very soft which exhibits large settlements when stressed above its maximum past pressure. In his presentation, Dr. Bemben states that “the silt/clay deposit has an inherent “cementing” due to precipitation of cementing agents and an ongoing time dependent aging process”. One net effect of the cementation process results in an under estimation of compressibility properties when interpreting one-dimensional consolidation tests using classical Terzaghi analysis.
The CVVC deposit is well-studied, however its compressibility and strength characteristics vary considerable between locations. One and two story structures can often be supported on shallow spread footing foundations, provided there is an upper alluvium sand or the surface of the CVVC has a desiccated crust. However taller structures often requires improvement of the CVVC by preloading that is aided by wick/sand drains, or by driving deep piles to the underlying dense glacial till or rock. Due to the variable despite characteristics, tall structures supported on top of the CVVC requires a program of laboratory index, compressibility, and strength testing to document conditions at a specific site.
Working within the CVVC deposit can also be challenging. The soils are generally sensitive, requiring careful field procedures to preserve its intact condition, bearing capacity and strength. Workmen can easily disturb soils to the extent that they can no longer support the specified soil bearing.
David Freed can be contacted at firstname.lastname@example.org .
GNCB attended the ribbon cutting ceremony for the Sayebrooke Village Elderly Housing Expansion project this month. The project broke ground earlier this year and now contributes an additional 15 units to the highly popular complex on Sheffield Street.
The buildings are a mixture of single- and two-story wood-framed structures on concrete slabs-on-grade. GNCB provide structural engineering and geotechnical engineering services for the project. The expansion was a Connecticut Housing Finance Authority (CHFA)-funded project.
Architect: Wiles + Architects
Contractor: Haynes Construction
Ms. Zoe Laird of Ohio has been hired as a Design Engineer at GNCB. Ms. Laird graduated from the University of New Haven (UNH) this May with a Bachelor’s of Science in Civil Engineering.
As a student, Ms. Laird was an active member of UNH’s student chapter of the American Society of Civil Engineers’ (ASCE) Concrete Canoe team, and was a member of the student chapter of the Society of Women Engineers (SWE).
Ms. Laird’s senior design project was to design a four-story steel-framed boutique hotel with an underground reinforced concrete parking garage for UNH’s Hospitality and Tourism department. She performed much of the structural analysis and structural design for the building, and performed hand calculations to verify the computer model.
Past work experience includes an internship with the Ashtabula County Engineer’s Office in Jefferson, OH; tutoring entry-level engineering courses at UNH; acting as counselor for Camp GEMS (Girls in Engineering, Math, and Science) at Ohio Northern University; and several summers at YMCA Camp Fitch holding various positions including Tech Focus Counselor.
Amy Jagaczewski , GNCB Engineer, attended this year’s Association for Preservation Technology International (APTi) Conference in Ottawa, Canada . This year’s conference, themed CAPITALizing on Heritage, was a joint conference between APTi and The National Trust of Canada in honor of Canada’s 150th Anniversary. Approximately 1100 delegates from over 20 countries attended, including engineers, architects, preservationists, owners, historians, students, craftspeople, and technicians.
The APTi Conference offered professional development opportunities sorted into seven tracks depending on attendees’ backgrounds and interests. Ms. Jagaczewski attended presentations on the investigation, analysis, planning, and design of heritage structures as well as case studies on successful implementation of structural and preservation engineering principles. Topics directly corresponding with current GNCB work included reversibility of retrofits for exposed structural framing, management and assessment of historic coastal structures, and practices for analyzing unreinforced masonry buildings in moderate seismic zones.
The Northampton Community Arts Trust began occupying their newly renovated building at 33 Hawley Street in Northampton, MA this fall. The prefabricated metal building was originally built in the late 1980s and required structural upgrades to support the new use and energy-efficient design. The 25,000 square foot building will be used by the Trust to support education, rehearsals, and performances for varying forms of art.
GNCB provided structural engineering and geotechnical engineering services for this project during the initial investigation, design phases, and construction phases. Structural work included supporting new design features as well as addressing deficiencies in the existing gravity and lateral framing systems for modern loads. Geotechnical investigations included interior soil excavations to confirm the layout of existing foundations and subsurface characteristics for the installation of a new elevator pit.
Improvements to the roof framing involved the addition of 50-foot long steel trusses supported on new steel columns at the centerline of the building. The new steel off-loads the original steel bent frames to meet modern building loads and allow the installation of solar panels and a future suspended catwalk system for the black box theater. Steel x-braces were installed between the new and existing perimeter building columns to improve the building’s lateral system. GNCB also provided structural designs for the monumental stair and mezzanine and the new front entrance vestibule.
Architect: Thomas Douglas Architects
Contractor: D.A Sulivan & Sons, Inc.
Steel Fabricator and Erector: Dublin Steel Corporation