Maffei Structural Engineering

Oakland, CA, United States

Maffei Structural Engineering

Oakland, CA, United States

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Maffei J.,Maffei Structural Engineering | Fathali S.,Rutherford Chekene Consulting Engineers | Telleen K.,Maffei Structural Engineering | Ward R.,SunLink Corporation | Schellenberg A.,6493 Farallon Way
Journal of Structural Engineering (United States) | Year: 2014

Currently, ASCE standards require that nonstructural components of a building be positively attached to the building in regions of moderate to high seismicity. However, for solar arrays that bear on low-slope roofs, friction between the array and roof surface limits or prevents sliding of the array in an earthquake. In many cases, the seismic performance of such arrays can be shown by analysis to meet the design intent of the building code without being fastened to the building structure. This paper presents a methodology for estimating the sliding displacement corresponding to ASCE standards for design-level earthquake shaking. The writers conducted nonlinear response-history analyses considering a range of different seismicity levels, roof slopes, and coefficients of friction, which lead to design values of sliding seismic displacement for solar arrays in different conditions. Important aspects of a broadly applicable analysis include performing testing to determine appropriate coefficients of friction, performing analysis with earthquake records spectrally matched to broadband response spectra, and considering the effect of vertical earthquake motion on frictional response. © 2014 American Society of Civil Engineers.


Zhang D.,Nazarbayev University | Fleischman R.,University of Arizona | Restrepo J.,University of California at San Diego | Sause R.,Lehigh University | And 3 more authors.
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

An innovative floor anchorage system is being developed through a multi-university NSF/NEES research project. The system, involving a ductile anchorage connector between the lateral force resisting system (LFRS) and the floor diaphragm, reduces inertial forces during major earthquakes. The system permits relative motion of the floor between the primary (vertical) elements of the LFRS and the gravity load resisting system at a predefined diaphragm force cut-off level. The system has the potential to reduce floor accelerations and inertial forces, thereby reducing the seismic demand on the LFRS. This paper presents the initial analytical studies and experimental work toward developing prototype configurations for the floor anchorage isolation system. The analytical studies identified the relationship between reduction in seismic demands and the amount of relative displacement between the LFRS and the floor diaphragm. This relative displacement is limited within practical limits to prevent too large of an increase in gravity column inter-story drifts. The product of these studies is a feasible design space and configuration for the anchorage system that optimizes the competing requirements of reducing structure seismic response while limiting relative displacement between the LFRS and the floor diaphragm. These optimized designs and configurations are being validated using physical experiments including large scale component tests at NEES@Lehigh and shake table testing at NEES@UCSD.


Telleen K.,Maffei Structural Engineering | Maffei J.,Maffei Structural Engineering | Heintz J.,Applied Technology Council
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

The 2010 Maule Chile Earthquake caused damage to several mid-rise and high-rise concrete wall buildings. Observed damage and potential lessons for the design of concrete wall buildings are addressed in the Applied Technology Council ATC-94 project, and include the following: Buckling of wall longitudinal reinforcement. Bar buckling occurs as a result of cyclic flexural tension and compression strain in the wall vertical reinforcement. This is an undesirable failure mode because it can lead to irreparable damage. To improve performance, walls need to have ties that restrain longitudinal bars from buckling. Typically the ties should engage each longitudinal bar where large tension strain is expected, and ties should be spaced vertically no further than six times the diameter of the longitudinal bar being restrained. The required horizontal extent of ties should consider tension neutral axis depth and strain, rather than just compression depth. Overall buckling of wall sections. This phenomenon consists of buckling of the wall section out-of-plane, resulting from cyclic tension and compression. Such buckling may be more likely to occur if adequate ties are provided to prevent buckling of individual bars. Like bar buckling this is an undesirable failure mode in regards to reparability of structures. To improve performance, recommendations include providing a minimum wall thickness at the compression boundary of a wall, as a function of the unsupported wall height in the region of potential plastic hinging. Unintended structural coupling. Coupling from slabs, beams, spandrels, stairs, and other outrigger-type elements can cause damage to these elements and can affect strain and damage patterns at the base of walls and increase wall shear demand. Potential practical improvements to design practices include accounting for these elements in the seismic analysis and design, even though they are not customarily designated as seismic force-resisting elements.


Maffei J.,Maffei Structural Engineering | Telleen K.,Maffei Structural Engineering | Ward R.,SunLink Corporation | Kopp G.A.,University of Western Ontario | Schellenberg A.,6493 Farallon Way
Journal of Structural Engineering (United States) | Year: 2014

Currently, ASCE standards do not provide specific guidance on wind loads for solar arrays of photovoltaic panels, in terms of either prescriptive design or requirements for wind tunnel testing. Guidance is needed, particularly for arrays of low-profile tilted panels on flat or low-slope roofs, because they are markedly different aerodynamically from structures currently addressed in the building code. This paper presents recommendations for the structural design of these solar arrays for wind-loading. Recommendations include (1) categorizing solar array support-systems according to their height above the building roof and how they distribute forces to the roof, (2) developing pressure coefficients that are applicable to structurally interconnected roof-bearing support systems, (3) considering load cases that include uniform wind pressure on the array and nonuniform (gust) patterns, (4) determining appropriate stiffness and boundary conditions for structural analysis, and (5) use of testing to verify behavior and calibrate analytical models. © 2013 American Society of Civil Engineers.


Schellenberg A.,6493 Farallon Way | Maffei J.,Maffei Structural Engineering | Telleen K.,Maffei Structural Engineering | Ward R.,SunLink Corporation
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2013

Evaluation of a solar array subjected to wind requires knowledge of the aerodynamics of the array as well as the structural response of the array to wind pressures that vary with time and location. Boundary layer wind tunnel testing using pressure-tap models is effective for measuring these pressures. However at the small scale necessary for such testing, particularly when modeling rooftop arrays, it is difficult to create aeroelastic models that can accurately capture the structural response. Nonlinear wind response-history analysis can account for dynamic effects in lieu of aeroelastic testing, with some advantages and limitations. Response-history analysis is a means for investigating the effects of structural dynamics on the behavior of solar arrays and the appropriateness of equivalent static analysis procedures. Key aspects in the implementation of response-history analysis include the effects of damping, nonlinear modeling assumptions, and initial conditions of the analysis. Findings from an investigation using response-history analysis indicate that a solar array support system that is flexible under uplift can resist code design-level winds provided there is adequate structural interconnection and sufficient ballast weight or attachments, particularly at the edges and corners of the array. © 2013 Elsevier Ltd.


Maffei J.,Maffei Structural Engineering | Burkett L.,Rutherford Chekene | Bazzurro P.,University of Pavia | Schellenberg A.,Oakland
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

The Health Sciences Instruction and Research facility is a 430,000 ft2 (40,000 m2) complex of two laboratory buildings and three adjoining tower structures that house stairs, elevators, and mechanical ducts. Built in 1963, the laboratory buildings are steel moment-frame structures made of large built-up sections. The authors evaluated the facility using seismic performance levels defined specifically for the project according to the client objective of minimizing research disruption following an earthquake. Nonlinear response-history analysis, at seven levels of hazard, is used to incrementally evaluate the structure. The evaluation uses a state-of-the-art probabilistic analysis with Monte Carlo simulation to define the seismic performance benefit of various retrofit schemes. Fragility curves specific to the building and its systems are developed, considering 16 engineering demand parameters including relative movement of separation joints and elongation of column splices after tension yielding (peak and residual). The demand parameters are chosen to represent both the peak severity and the extent (e.g., over several floors) of potential damage. The approach goes beyond current performance-based tools by incorporating issues such as intersecting rather than sequential performance states. The study provides the owner with a menu of retrofit measures that allows them to optimize the seismic performance of the facility under various given scenarios of construction funding and functional constraints.


Burkett L.,RutherfordChekene Consulting Engineers | Maffei J.,Maffei Structural Engineering | Schellenberg A.,Oakland
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

San Francisco International Airport's new air traffic control tower is a 67 m (220 ft) tall structure within 4 km (2.5 miles) of the San Andreas Fault, founded on an extremely soft soil profile. The site consists mostly of Bay Mud in the 36 m (120 ft) depth above Franciscan bedrock. The building is designed to meet the demanding functional constraints of a continuously occupied control tower, and to remain operational following a major earthquake. The structural system consists of a cylindrical reinforced concrete core wall over a pile foundation with a single main pile cap. The tower is surrounded by a three-story base building housing FAA and Airport functions. The core wall is designed to have nonlinear behavior occur in a plastic hinge region located just above the roof of the base building. Unbonded vertical post tensioning is placed over the height of the core wall to minimize residual earthquake deformation and to close flexural cracks that form in the plastic hinge region. Buckling-restrained braces, oriented horizontally, brace the tower into the roof diaphragm of the base building, providing backstay support without overloading the base structure. The design is analyzed using nonlinear response-history analyses and site-specific earthquake ground motions. Ground motions are selected probabilistically to produce a suite with appropriate dispersion around a conditional-mean spectrum. The authors carried out a nonlinear soil-structure interaction study to assess the ductility demands for deep foundation elements extending to bedrock. The analyses demonstrate that while the soft soil profile attenuates much of the bedrock motion before it reaches the ground surface, large displacements occur deep in the soil, which impose nonlinear deformation demands on the foundation piles.


Telleen K.,Maffei Structural Engineering | Maffei J.,Maffei Structural Engineering | Dias T.B.,Pyatok Architects | Baker J.A.,Bowles Hall Foundation
Improving the Seismic Performance of Existing Buildings and other Structures 2015 - Proceedings of the 2nd ATC and SEI Conference on Improving the Seismic Performance of Existing Buildings and Other Structures | Year: 2015

Bowles Hall is a reinforced concrete building of approximately 55,000 square feet on eight levels. The structure was designed in 1927 as the first residence hall in the University of California system. Designed by the architect George W. Kelham in the Collegiate Gothic style, the building is designated a landmark for the City of Berkeley and is listed in the National Register of Historic Places. A western trace of the Hayward earthquake fault passes underneath two corners of the building. In 2015, the renovation and restoration of the structure plus the construction of an addition was undertaken to revitalize the building's character and usefulness. The new work revises the dormitory room layout to include bathrooms within units, adds wheelchair accessibility, replaces or upgrades all building utilities, restores and protects historic features, corrects life safety deficiencies, restores dining, and adds conference capabilities. The renovation and retrofit are being carried out through a public-private partnership, and the dormitory will re-open as a coeducational "residential college." As described in a recent newspaper article, there will be "new keepers of the castle" (Whiting 2015). The remodel affords the opportunity to address remaining seismic deficiencies. Selective retrofit work had been done in 1977, and measures to accommodate earthquake fault-offset were constructed in 2009. Structural and seismic measures in the current construction include addressing discontinuous structural walls and constructing new building spaces, elevators, and stairways in a way that augments seismic resistance. Non-structural retrofit work includes developing secure attachment of historic tiles on the steeply pitched roofs and providing support for existing historic ceilings in the main dining and common rooms. Challenges of the project include a number of unique structural details, and development of an appropriate analysis strategy for a hillside structure in a location of extreme seismicity. © 2015 ASCE and ATC.


Fleischman R.B.,University of Arizona | Restrepo J.I.,University of California at San Diego | Pampanin S.,University of Canterbury | Maffei J.R.,Maffei Structural Engineering | And 2 more authors.
Earthquake Spectra | Year: 2014

The 2010-2011 Canterbury earthquake sequence provides a rare opportunity to study the performance of modern structures designed under well-enforced, evolving seismic code provisions and subjected to severe ground shaking. In particular, New Zealand makes widespread use of precast concrete seismic systems, including those that are designed to respond identically to cast-in-place concrete structures (emulative systems) and, in more recent years, those that take advantage of the unique jointed properties of precast construction. New Zealand building construction also makes extensive use of precast elements for gravity systems, floor systems, stairs, and cladding. Although not always classified as part of the primary seismic force-resisting system, these "secondary" elements must undergo the compatible displacements imposed in the earthquake. Damage evaluations for several of these structures subjected to strong shaking provide the ability to examine the differences in seismic performance for systems of distinct design intent and standards, including the performance of secondary elements. © 2014, Earthquake Engineering Research Institute.

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