Forell Elsesser Engineers Inc.

San Francisco, CA, United States

Forell Elsesser Engineers Inc.

San Francisco, CA, United States
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Cooke R.J.,Forell Elsesser Engineers Inc. | Kanvinde A.M.,University of California at Davis
Journal of Constructional Steel Research | Year: 2015

Finite element (FE) simulations used to characterize extreme limit states in steel structures require the calibration of numerous parameters. Calibration of these models for large strains (greater than 0.3 or so) cannot be performed using stress-strain curves on standard tests, since the stress state in these tests becomes non-homogenous due to necking or buckling which occur at lower strains. As a result, calibration is often performed by matching load-displacement curves of calibration specimens to those obtained through complementary FE simulations. In these situations, multiple parameter sets produce strain fields that match the measured load-displacement response, resulting in non-unique parameter fits. A series of 2400 FE simulations with 4 specimen geometries, 300 material parameters sets, and 2 loading histories indicates that multiple trial parameter sets produce excellent load-displacement match with the true material response, implying that the method is highly susceptible to non-unique fitting. All simulations use the Armstrong and Frederick constitutive model with a von Mises yield surface. The impact of non-unique fitting is assessed through FE simulations based on parameter sets that show excellent load-displacement match with calibration specimens. It is determined that the non-uniqueness does not significantly affect the prediction of peak force. However, it severely impacts the accuracy in prediction of internal plastic strains, with errors as large as 50% with respect to the true material. This has serious implications for FE simulation used to characterize extreme, strain-based limit states such as fracture. Strategies for mitigation of this inaccuracy are presented, along with limitations of the study. © 2015 Elsevier Ltd. All rights reserved.

Kanvinde A.M.,University of California at Davis | Marshall K.S.,Structural Integrity Associates | Grilli D.A.,University of California at Davis | Bomba G.,Forell Elsesser Engineers Inc.
Journal of Structural Engineering (United States) | Year: 2015

The earthquake on February 22, 2011, in Christchurch, New Zealand, resulted in the first documented field fractures of links in eccentrically braced frames (EBFs). A comprehensive forensic analysis of these fractures, which occurred in the parking garage of the Christchurch Hospital, is presented. The analysis is based on mechanical and spectrochemical testing and three-dimensional (3D) scanning of procured physical samples of the fractured links. The analysis features nonlinear time history simulations to characterize deformation demands and continuum finite-element simulations to determine the capacities based on a sophisticated fracture mechanics model. The exercise represents a multiscale end-to-end simulation of the system and provides insight regarding the observed fractures. The analysis reveals the inherent challenges in determining the proximate cause of the fractures because the fractures occurred because of a confluence of several interacting factors, primarily the intensity of shaking (several times the intensity that was expected during a design-level event) and the frame geometry, which severely amplified the imposed demands. In addition, the fractured links also suffered from an erection (fit-up) error, in which the link stiffener was not located (as specified) directly above the brace flange, producing a severe strain concentration. This flaw significantly reduced the deformation capacity; however, the simulation of hypothetical scenarios indicates that, even with this flaw, the links would (with high likelihood) have survived a design-level event. Strategies for mitigation include stricter tolerances for stiffener location, consideration of frame geometry to reduce amplification of rotation, and enhancement of the seismic hazard used for design. The limitations of the study are outlined. © 2014 American Society of Civil Engineers.

Rodriguez-Nikl T.,California State University, Los Angeles | Comber M.,Project Frog | Foo S.,Public Works and Government Services Canada | Carter S.J.G.,Structural Engineering Design Professional | And 5 more authors.
ICSI 2014: Creating Infrastructure for a Sustainable World - Proceedings of the 2014 International Conference on Sustainable Infrastructure | Year: 2014

Structural engineers often limit their involvement in sustainability to material selection and recycling. Few structural engineers recognize the relationship between sustainability and disaster resilience. In response, the Sustainability Committee of the Structural Engineering Institute wrote a committee report to raise awareness of and provide guidance on the pertinent issues. This paper highlights the salient parts of the committee report. The introduction explains the relationship between sustainability and resilience and reviews the impacts of natural disasters. The following sections discuss general consideration for resilient design and summarize efforts to promote resilience and guidance for resilient design. Next are discussed current efforts to quantify the connection between disaster resilience and sustainability. The paper concludes with suggestions for structural engineers who are interested in supporting disaster resilience and sustainability. © 2014 American Society of Civil Engineers.

Kanvinde A.M.,University of California at Davis | Higgins P.,Peter S. Higgins and Associates | Cooke R.J.,Forell Elsesser Engineers Inc. | Perez J.,University of California at Davis | Higgins J.,Peter S. Higgins and Associates
Journal of Structural Engineering (United States) | Year: 2015

The seismic response of exposed hollow steel section columns to base plate connections is examined through a series of eight experiments. The prototype-scale tests investigate a range of variables including base plate size and thickness, column size, and anchor rod layout (four rods in two rows, and eight rods in three rows). The specimens were subjected to cyclic flexural loading and instrumented to provide direct (rather than inferred) measurement of tension forces in the anchor rods. All the specimens showed excellent deformation capacity, with a stable hysteretic response for base rotations as large as 0.057-0.13 rad. Three specimens failed by fracture of the weld between the column and the plate, whereas five did not fracture. Evaluation of the test data against the current design approach prevalent in the United States suggests that (1) the design approach is reasonably conservative but (2) does not address the effect of the third (i.e., central) row of anchor rods; as a result, it cannot be used to design them. A new design method is presented that explicitly incorporates the third row of rods. The new approach is evaluated against the test data and it is determined that the new approach reflects the internal mechanics of the connections in an improved way while providing more accurate estimates of forces in the rods. Recommendations for the design of the connections are outlined, along with ongoing work that leverages the deformation capacity of these connections for displacement-based design. The limitations of the study are summarized, especially in terms of challenges to the generalization of its findings. © 2014 American Society of Civil Engineers.

Maclise L.,Forell Elsesser Engineers Inc. | Nelson T.,Degenkolb Engineers | Kyler M.,Holmes Culley | Kang G.,Forell Elsesser Engineers Inc. | And 3 more authors.
Structures Congress 2013: Bridging Your Passion with Your Profession - Proceedings of the 2013 Structures Congress | Year: 2013

The Futures Without Violence headquarters building (Presidio Building #100), the Walt Disney Family Museum building (Presidio Building #104) and Presidio 101 and 103 (Presidio Buildings #101 and #103) are all former barracks buildings on the main parade grounds of the historic Presidio of San Francisco. They are constructed of unreinforced masonry brick walls with heavy timber framing and were built in the late 19th and early 20th centuries. All are fine examples of adaptive re-use and sustainable design practices. San Francisco's location, with its proximity to major earthquake faults, presents a heightened risk to these types of historical buildings. Therefore it is critical to seismically upgrade and preserve these historic structures for future generations. While seismic events are a regional issue, natural hazards occur throughout our national and global community and the importance of preserving historical structures as well as preparing resilient and sustainable communities is of global importance. All of the buildings in this case study have recently been retrofitted, renovated and repurposed to serve the community for many years to come. In this paper, the different approaches utilized in the adaptive re-use of these nearly identical buildings will be described. Retrofit and renovation is one of the most impactful things that can be done to achieve sustainable design goals. By extending a building's life-span, the embodied energy in the building is preserved and the need for new building materials and construction waste is decreased. This unique set of buildings creates a real-life study of how designers, building owners and contractors can re-purpose the same type of building in different ways. All of the buildings feature exposed structure and tasteful additions to maximize square footage while maintaining the character visible from the main parade ground elevations. This paper will discuss the sustainable impacts of retrofit and renovation, review several building retrofit strategies available to designers, and the various adaptive re-use strategies that designers can use. © 2013 American Society of Civil Engineers.

Sabouri-Ghomi S.,K. N. Toosi University of Technology | Ahouri E.,K. N. Toosi University of Technology | Sajadi R.,K. N. Toosi University of Technology | Alavi M.,Finele Consulting Engineers | And 2 more authors.
Journal of Constructional Steel Research | Year: 2012

Openings in steel plate shear walls (SPSWs) in buildings are provided for architectural reasons as well as for access requirements. Despite the reduction of stiffness and strength in panels with an opening being well-understood, further studies are essential in order to determine both the mechanism and the degree of this degradation, as well as its dependency on the location and the size of the opening. To accomplish this aim, a non-linear finite element analysis is used in this paper to study the behaviour of both stiffened and unstiffened SPSWs with a single rectangular opening. The size and location of the opening are varied from model to model in order to determine their influences on the stiffness and strength of the system. Based on the results obtained, the strength and stiffness degradation of unstiffened panels are affected adversely by the location of the opening. In contrast, the re-location of an opening of a specific size within the panel area in stiffened panels does not appear to influence this degradation, so that the stiffness and strength deterioration are not a function of the location of the opening. As expected, both stiffened and unstiffened panels experience a progressive reduction in their stiffness and strength with an increase of the size of the opening. It is demonstrated further that with an increase in the opening ratio (width to height), the energy absorbed by the system arising from seismic loading considerations in both stiffened and unstiffened SPSWs show a linearly decreasing trend; this trend being less stiff for stiffened panels. Unstiffened SPSWs with a central opening experience the least energy absorption. It is also shown that the absorption of energy is substantially higher in stiffened panels when compared with their otherwise identical, but unstiffened, counterparts. © 2012 Elsevier Ltd. All rights reserved.

Zareian F.,University of California at Irvine | Sampere C.,Forell Elsesser Engineers Inc. | Sandoval V.,Engineering Simulation and Scientific Software | McCormick D.L.,Simpson Gumpertz and Heger | And 2 more authors.
Earthquake Spectra | Year: 2012

This paper summarizes the EERI reconnaissance team findings on damage to the Chilean wine industry after the 27 February 2010 Offshore Maule Earthquake. Wine production is one of the major industries in Chile, with an annual production of approximately one million metric tons. It is estimated that the total loss to the wine industry is over 125 million liters, with infrastructure damage estimated as high as US$430. Most of the damage was concentrated in older wineries with collapse of adobe walls and timber roofs or ribbed brick vaults. Damage to steel fermentation tanks was widespread among all wineries visited with the severity of such damage depending on the type of tank anchorage. Local buckling of legs in legged tanks or excessive movement followed by the tank falling off the support pad led to toppling that ruptured piping or valves. Stacked barrels, stored bottles of wine, and production lines were also damaged. © 2012, Earthquake Engineering Research Institute.

Lee W.K.,Forell Elsesser Engineers Inc. | Billington S.L.,Stanford University
Earthquake Engineering and Structural Dynamics | Year: 2011

Highway bridges in highly seismic regions can sustain considerable residual displacements in their columns following large earthquakes. These residual displacements are an important measure of post-earthquake functionality, and often determine whether or not a bridge remains usable following an earthquake. In this study, a self-centering system is considered that makes use of unbonded, post-tensioned steel tendons to provide a restoring force to bridge columns to mitigate the problem of residual displacements. To evaluate the proposed system, a code-conforming, case-study bridge structure is analyzed both with conventional reinforced concrete columns and with self-centering, post-tensioned columns using a formalized performance-based earthquake engineering (PBEE) framework. The PBEE analysis allows for a quantitative comparison of the relative performance of the two systems in terms of engineering parameters such as peak drift ratio as well as more readily understood metrics such as expected repair costs and downtime. The self-centering column system is found to undergo similar peak displacements to the conventional system, but sustains lower residual displacements under large earthquakes, resulting in similar expected repair costs but significantly lower expected downtimes. © 2010 John Wiley & Sons, Ltd.

Friedman D.A.,Forell Elsesser Engineers Inc. | Vignos R.,Forell Elsesser Engineers Inc. | Walters M.T.,Forell Elsesser Engineers Inc. | Petteys C.,Forell Elsesser Engineers Inc. | Bomba G.,Forell Elsesser Engineers Inc.
Structural Design of Tall and Special Buildings | Year: 2012

This paper addresses the seismic retrofit of the University of California at Berkeley's California Memorial Stadium (CMS) to accommodate surface fault rupture movements as well as intense seismic shaking from the Hayward fault. For the surface fault rupture aspect of the project, the project team took a multidisciplinary approach that involved structural engineers, geotechnical engineers, seismologists and geologists collaborating to establish design criteria and possible surface rupture scenarios. The mechanics of surface fault rupture are discussed relative to the structural design approach that mitigates the effects of surface deformations caused by the fault during an earthquake. The effects of the surface fault rupture were studied using small scale physical models and nonlinear finite element models of the building and rupturing ground surface. The retrofit scheme accommodates the concentrated ground deformations of an estimated 6ft of horizontal movement and 2ft of vertical offset caused by a surface fault rupture. Segments of the CMS that overlay the regions of possible surface fault rupture were decoupled from the main structure via movement gaps to accommodate relative displacements of the building segments, including tilting in the event of earthquake-produced fault rupture. The results of the analyses are discussed along with the design decisions and challenges of retrofitting a historic structure that resides on an active fault. While a large portion of the engineering effort was devoted to solving the issue of accommodating surface rupture, another large engineering challenge also dominated the design of the CMS. One of the signature architectural features of the stadium is a two-story, 375-ft long press box that hovers above the new west side of the seating bowl. Although designing the press box on limited supports to give the appearance of 'hovering' was a challenge, the real challenge came in safely bracing this structure for large potential ground motions at this site. The interface between the flexible support of the press box and the rigid seating bowl became a challenge, solved by providing a separation between the bowl and press box structures allowing them to move independently while linking them only with fluid viscous dampers. © 2012 John Wiley & Sons, Ltd.

Lee W.K.,Forell Elsesser Engineers Inc. | Billington S.L.,Stanford University
Journal of Bridge Engineering | Year: 2010

Nonlinear dynamic analysis with fiber-element models is now widely used to assess the seismic response of bridge structures. The ability of such models to accurately simulate response parameters for characterizing the postearthquake condition of bridges, namely residual displacements, is assessed by comparison of analyses of dynamically loaded reinforced concrete bridge columns to experimental data. The models are unable to capture residual displacements, and the cause of the inability to capture residual displacements is investigated through dynamic analysis of fiber-element and single-degree-of-freedom (SDOF) models. A certain type of pinching present in the numerical hysteretic response shape is found to lead to poor residual displacement simulation both in the SDOF models and in fiber-element models. When eliminating this pinching, improvements to residual displacement simulation are found. A modified concrete constitutive model representing damage accumulation from cyclic loading is implemented for the fiber-element analysis that incorporates changes to reloading behavior when moving from high tensile strain back to compression. Analysis using the modified concrete constitutive model leads to improvements in the ability of the fiber-element model to capture residual displacements. © 2010 ASCE.

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