Sam X. Yao |Senior Principal
Samhas more than 25 years of experience in construction engineering of heavy civil works in marine and underground environments. His expertise includes in-the-wet construction, deep foundation, marine engineering, and concrete technology; and he has authored several publications on the topics. With an international reputation in heavy civil engineering design and consultation, Sam has led and successfully completed design of various civil works, including bridges and tunnels, locks and dams, piers and wharves, seawall and shoreline protection, and excavation shoring. He has also served as an investigator and/or an expert witness for many construction failure cases involving concrete defects, drilled shafts, prestressed concrete piles, jet grouting, slurry walls, bridges, and tunnels. 

Peter M. Babaian | Principal

Peter is the Building Technology Division Head for our Chicago office and leads the Building Enclosure Commissioning Practice at SGH. He has more than 14 years of engineering experience, including designing, investigating, and rehabilitating a variety of building enclosures and structures. His specialties include exterior enclosure consulting on new construction, rehabilitation of existing structures, historic preservation, and building enclosure commissioning. Peter is an active member of many professional industry groups, including the Technical Activities Committee of The Masonry Institute. 

Amy L. Hackney| Principal

Amy is head of SGH’s Building Technology division in Los Angeles and has more than 11 years of engineering experience. Her primary emphasis is on new design building envelope consultation. Her work addresses issues related to the integrity of curtain walls, exterior walls, roofs, plaza deck, and below-grade systems. She has experience working with architects, contractors, and developers on a wide range of structures, including high-rise condominiums, hotels, healthcare facilities, museums, and commercial and mixed-use projects. Her experience also includes investigating existing building envelopes and waterproofing systems and repair and rehabilitation design of those components.  Amy is on the Board of Governors for the Architectural Engineering Institute of the American Society of Civil Engineers (ASCE).

Aaron R. Lewis| Principal

Aaron has been involved in diverse applications of civil, geotechnical, and structural engineering and consulting for more than 13 years. His experience includes engineering for heavy civil infrastructure, excavation support design, flood risk evaluation and mitigation, marine engineering, precision movement monitoring, and constructability and construction cost analysis. He has contributed substantially to the ASCE 7 Rain and Snow Load Subcommittee, particularly in the area of ponded rain loads on roofs. Aaron has authored papers on his activities and made presentations to industry groups and at public hearings. 

Paul E. Kassabian| Associate Principal

Paul has more than 15 years of experience in structural design and investigation on a wide range of structural systems, from buildings for architects to projects on the cutting edge of both structural systems and materials. He focuses on developing innovative methods of design and construction using SGH’s in-house materials lab, computational design approaches, and digital fabrication techniques. Paul was a lecturer at Massachusetts Institute of Technology to graduate structural engineering students for ten years and at Harvard Graduate School of Design to graduate architecture students.  

James A. McDonald| Associate Principal

Jim has 20 years of engineering experience, including five years with SGH. His practice includes structural design of education, healthcare, residential, and commercial buildings; seismic evaluation and upgrade; structural investigations; condition assessments; and concrete investigation and repair. Jim’s evaluation specialization includes deflection of concrete slabs, seismic risk assessments, nuclear seismic probabilistic risk assessments, and bridge assessments for beyond design loads and damage. Jim’s rehabilitation specialization includes modification, strengthening, or repair of damaged steel structures and concrete repair. 

Jeffrey D. Kerr| Associate Principal

Jeff’s 17 years of project management and engineering experience includes building enclosure projects ranging from new design consulting to investigating and repairing existing buildings for a variety of clients, including public and private building owners, architects, and contractors. His work includes design consultation for new construction; facade modernization, including condition assessment, feasibility analysis, preparation of design documents, and construction administration; and building enclosure commissioning.  He has experience with evaluating and designing natural stone cladding and paving and is a member of ASTM International's Committee C18 on Dimension Stone. Prior to joining SGH, Jeff worked for a commercial general contractor on public and private developments, including on-site project management and preconstruction budgeting services. 

Nathaniel B. Smith | Associate Principal

Nate has more than 15 years of engineering experience, including ten years at SGH. His experience includes structural design, investigating building damage and collapses, repair and rehabilitation projects, and monitoring foundation installations. His background in geotechnical engineering provides him with knowledge of soil and foundation types that aids him in performing structural evaluations of existing buildings and investigations of structural damage and collapses. He has more than five years of full-time field engineering experience, which he uses in his design and investigation projects. Nate is the secretary of the ASCE Metropolitan Section Forensic Engineering Group, and he has also given numerous presentations on the effects of adjacent construction on existing structures.