Elstner Associates Inc.
Elstner Associates Inc.
News Article | May 16, 2017
Tom Marquardt has joined HOK’s Chicago office as vice president and director of interiors. Marquardt was formerly a design principal in HDR’s Chicago office. Prior to that, he established and led his own design studio, marquardt+, for nearly 30 years. Pat Askew has joined HKS’s Chicago office as principal and global director of aviation. He joins the firm from Gensler, where he was a principal and firmwide aviation and transportation practice area leader. Earlier in his career, Askew led global aviation practices for both Perkins+Will and HOK. Alan Stone has joined Wiss Janney Elstner Associates as a principal. Stone, who has 36 years of experience in the failure analysis of metal components, metallography, scanning electron microscopy and ferrous metallurgy heat treatment, previously founded Aston Metallurgical Services Co., which provided metallurgical, mechanical and chemical testing services. Chicago-based CannonDesign has named Hilda Espinal senior vice president and chief technology officer. She was previously CTO at HKS. Espinal has more than 16 years of related experience with global design firms. Jenny Miller also joined CannonDesign’s Chicago office as business development leader. Miller joins the firm with more than 10 years’ experience in the health care sector.
Beasley K.J.,Elstner Associates Inc.
Proceedings of the Institution of Civil Engineers: Forensic Engineering | Year: 2016
In the urban environment, building facades can be exposed to conditions that are not present in other environments. These include acid rain, higher atmospheric carbon dioxide and other agents that can deteriorate or attack the facades of city buildings or other urban structures. Sulfurous, sulfuric and nitric acids present in polluted air dissolve calcite minerals in marble and limestone facades or in concrete and mortar aggregates. Harsh cleaning chemicals or methods used to wash away city soil and soot can damage facades. Sealants can degrade and discolour from airborne deposits and contaminants. Facades may suffer impact and abuse from adjacent building construction activities. While failure of building facades or their connections can result from countless causes, the extent and consequences of such failures are often exacerbated by pollutants and chemicals that are commonly present in the urban environment. This paper addresses special considerations, conditions and risks that are associated with building facade failures in cities. The majority of urban facade failure descriptions and cases presented in this paper are based on the author’s experience in the USA. © ICE Publishing. All rights reserved.
Grilli D.,Elstner Associates Inc. |
Jones R.,AKT II Ltd. |
Kanvinde A.,University of California at Davis
Journal of Structural Engineering (United States) | Year: 2017
Embedded column base (ECB) connections are used in mid- to high-rise steel moment frames to transfer base moments and forces into the footing. These connections, which feature a steel column embedded into a concrete footing, are used when exposed base plate connections are unfeasible for providing the requisite strength or stiffness. Results from five full-scale tests on ECB connections are presented to examine their seismic response. The test specimens, representing prevalent construction practice, were subjected to cyclic lateral deformations in the presence of an axial (tensile or compressive) load. Test variables included embedment depth, axial load, and column size. Damage was observed in the form of concrete crushing in the bearing zones ahead of the column flanges, shear cracking in the joint panel region, and flexural cracking of the entire footing. Two types of failure were observed: (1) gradual loss of strength due to concrete crushing ahead of the flange and (2) upward pryout of concrete on the tension side of the connection. The former mode was dominant in the specimens with deeper (762 mm) embedments, whereas the latter was dominant in shallower (508 mm) embedments. These failure modes and experimental measurements suggest that the base moment is resisted through a combination of horizontal bearing stresses on the column flanges and vertical bearing stresses on the embedded base plate. All specimens sustained significant deformations (2-7% column drift) prior to load loss or failure. It is determined that even if designed as rotationally fixed, the specimens have significant flexibility, which must be considered in simulation and design. Limitations of the study are discussed, and suggestions are provided for the development of a strength model based on the experimental findings. © 2017 American Society of Civil Engineers.
Chen G.M.,Hong Kong Polytechnic University |
Teng J.G.,Hong Kong Polytechnic University |
Chen J.F.,University of Edinburgh |
Rosenboom O.A.,Elstner Associates Inc.
Journal of Composites for Construction | Year: 2010
RC beams shear strengthened with either fiber-reinforced polymer (FRP) U-jackets/U-strips or side strips commonly fail due to debonding of the bonded FRP shear reinforcement. As such debonding occurs in a brittle manner at relatively small shear crack widths, some of the internal steel stirrups may not have reached yielding. Consequently, the yield strength of internal steel stirrups in such a strengthened RC beam cannot be fully used. In this paper, a computational model for shear interaction between FRP strips and steel stirrups is first presented, in which a general parabolic crack shape function is employed to represent the widening process of a single major shear crack in an RC beam. In addition, appropriate bond-slip relationships are adopted to accurately depict the bond behavior of FRP strips and steel stirrups. Numerical results obtained using this computational model show that a substantial adverse effect of shear interaction generally exists between steel stirrups and FRP strips for RC beams shear strengthened with FRP side strips. For RC beams shear strengthened with FRP U-strips, shear interaction can still have a significant adverse effect when FRP strips with a high axial stiffness are used. Therefore, for accurate evaluation of the shear resistance of RC beams shear strengthened with FRP strips, this adverse effect of shear interaction should be properly considered in design. © 2010 ASCE.
Schmidt M.K.,Elstner Associates Inc.
Challenging Glass 2 - Conference on Architectural and Structural Applications of Glass, CGC 2010 | Year: 2010
Heat-strengthened glass with residual surface compressive stresses above those allowed by ASTM C1048 was installed in a curtain wall in the mid-Atlantic region of the United States. To address building ownership's concerns regarding postbreakage glass fallout, fragmentation tests were performed using a protocol adapted from EN 1863. Consistent with previous research, no significant difference in fragmentation was noted between samples with residual surface compressive stresses conforming to ASTM C1048 and those with residual surface compressive stresses well beyond the established ASTM limits. Simplistic analyses revealed that, under certain modes of failure, risk of glass fallout is comparable for conforming and nonconforming heat-strengthened glass. The completed testing also has implications for glass quality control processes. Copyright © with the authors. All rights reserved.
Duntemann J.,Elstner Associates Inc. |
Greve B.,Elstner Associates Inc.
IABSE Conference, Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges - Report | Year: 2015
The twin towers of Marina City were the tallest reinforced concrete buildings in the world when they were completed in 1962. The design and construction of Marina City was an important milestone during the evolution of concrete high-rise construction during the 20th century, and the unique modern design served as a model for mixed-use developments that is still used today. The construction of the towers utilized innovative design and construction techniques. Significant concrete deterioration was identified on the facade in the 1990's which presented challenges associated with performing concrete repairs on high-rise buildings. This paper reviews the history of the design, construction and restoration of these iconic towers.
Reins J.D.,Elstner Associates Inc.
Journal of Performance of Constructed Facilities | Year: 2016
This paper discusses the partial collapse of John Purdue Block, a historic masonry structure in Lafayette, Indiana. The collapse occurred while the structure was being renovated and modified to prepare it for a new occupancy and usage. Prior to the start of the project, masonry strengths were not assessed or even estimated, and the primary structural elements were not analyzed for the proposed changes in loading and geometry. Relatively modest loads on the masonry walls and columns, coupled with a long-term performance without distress, may have provided a false sense of confidence that the structure could safely withstand comparatively minor changes in geometry and loading. Subsequent testing and analysis revealed the cause of the failure to be localized compressive stresses that exceeded the ultimate capacity of the brick masonry. © 2014 American Society of Civil Engineers.
Horst M.,Elstner Associates Inc.
ASTM Special Technical Publication | Year: 2016
Exterior insulation and finish systems (EIFS) can provide a durable, waterresistant covering for a variety of building types. However, as with any cladding material, considerations during design and workmanship during construction are the primary factors in determining the success of an EIFS-clad building. Among the important factors to consider in the design of EIFS cladding is that the EIFS is only one component of the overall building enclosure system, which includes roofing, windows, sealants, possibly other cladding materials, and many other elements. During the design phase of a project, careful consideration must be given to the compatibility of other enclosure components with the EIFS. In addition, detailing of the interfaces between the EIFS and these components, typically referred to as integration details, is critical in achieving the expected building performance and durability of the exterior cladding assembly. During the construction phase, coordination of various trades, including the EIFS installer, is essential to ensuring successful installation of these integration details. Over the past 15 years, the author has had the opportunity to evaluate a variety of EIFS-clad buildings that exhibit successes and failures of these integration details. More recently, the author has performed peer reviews for design architects and has provided consulting services to assist contractors with potential compatibility issues and with developing integration details. In this paper, the author will discuss several common problematic interfaces between EIFS and adjacent construction. Design principles and other considerations for improving the function of the exterior building enclosure at these interfaces will be explored. Several case studies, including positive and negative examples of design and construction details, will be used to illustrate concerns with their integration. In addition, the paper will identify and discuss facets of several of the standards that have been developed by ASTM International (ASTM) to assist designers, consultants, and contractors in the development of integration details and the determination of their compatibility. © Copyright 2016 by ASTM International.
Kehoe B.E.,Elstner Associates Inc.
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014
Seismic design of nonstructural components using ASCE 7-10 considers the interaction between the response of the nonstructural component and the response of the building by means of a component amplification factor, ap, that accounts for the dynamic interaction between the nonstructural component and the response of the building. ASCE 7-10 provides tables of architectural, mechanical, and electrical components that specify values for ap. The values in the tables are either 1.0 or 2.5 for components considered rigid or flexible, respectively. ASCE 7-10 provides a definition for determining whether a component is rigid based on the component's period of vibration. The tabulated values of nonstructural amplification factors may not adequately characterize the actual seismic behavior of some nonstructural components since the values do not consider the actual properties of the nonstructural components and the effect of actual support and bracing. While ASCE 7-10 provides a formula for determining the actual period of mechanical and electrical components, this formula is seldom used in actual practice. Determining the period of vibration of a nonstructural component does not provide all of the information needed to assess how a nonstructural component will respond during an earthquake since it does not consider the predominant periods of vibration of the building. The vibrational periods for some common nonstructural components are tabulated based on considerations of material properties and dimensions. Data from component testing are also summarized and compared to calculated values. The influence of support conditions are also described. Recommendations for changes to building code requirements are presented.
Tide R.H.R.,Elstner Associates Inc.
Engineering Journal | Year: 2010
In this paper, bolt shear capacities are reviewed using the Load and Resistance Factor Design (LRFD) philosophy. Only bolt-shear limit states are addressed, although one aspect of slip critical limit states is addressed incidentally. This paper does not consider bolt bearing limit states. Test data used to justify the adoption of ASTM A325 and A490 high-strength bolts was obtained from previous research programs. The data also included various types of rivets and Huck bolts for general comparison. First, the test data are used to evaluate the current American Institute of Steel Construction (AISC, 2005) and Research Council on Structural Connections (RCSC, 2004) bolt shear provisions and to determine the current reliability, β, which is found to be conservative when based on a resistance factor, φ, of 0.75. The appropriateness of the ?-factor for bolt shear is addressed. Canadian (CSA S16-01) and Eurocode (EN 1993) provisions are also evaluated and shown not to be compatible with the test results. Two design equations are developed-one linear, one a step function-that result in a β value slightly greater than 3.0, appropriate for a manufactured product. The single-step function (with a step at 38 in.) is recommended for inclusion in updated design specifications. This design provision increases the design strength by 12.5% for short connections and by 17.2% for long connections. The test data indicate that there is no need for a bolt strength reduction due to the length of the connection, provided that the connection material gross and net section areas exceed certain ratios. That ratio is a function of the connection material yield and tensile strength, the total bolt shear area and the bolt tensile strength.