Arlington, TX, United States
Arlington, TX, United States

Time filter

Source Type

Richard M.J.,Simpson Gumpertz and Heger | Harries K.A.,University of Pittsburgh
Wood Science and Technology | Year: 2015

Bamboo materials are often characterized using standard tension coupon tests. However, due to the functionally graded nature of bamboo, the standard tension test geometry is inherently flawed and may result in additional non-uniform bending stresses being introduced across the breadth of the cross section during testing. An experimental programme highlighting issues with, and interferences present, in current methods and practices regarding the tensile strength of clear bamboo specimens cut from the culm wall is presented. The study investigates the influence of fibre gradation on the specimen behaviour using tensile specimens having different in situ orientation; these include ‘radial’ specimens engaging the full gradation of fibres through the culm wall thickness, and ‘tangential’ specimens taken from varying locations through the culm wall thickness perpendicular to the radial direction. The study also considered the end restraint condition provided by the testing machine—for which there is no guidance in applicable standards. Digital image correlation was used to measure variation in strain in the test specimens related to their native orientation in the bamboo culm. Fibre density across the culm wall thickness and the end restraint conditions of the specimens were shown to have an influence on bamboo tensile test results and therefore must be considered in the development of improved standard test methods. It is recommended that tangential specimens are used since they possess a more uniform fibre density throughout their cross section and taken together can outline the fibre density and strength in the radial direction through the culm wall. Fixed end restraints result in marginally lower measured tensile strengths having marginally improved variation. © 2014, Springer-Verlag Berlin Heidelberg.

Phelps A.F.,Simpson Gumpertz and Heger | Horman M.J.,Pennsylvania State University
Journal of Construction Engineering and Management | Year: 2010

Traditional construction research methods have enabled focused but narrow advances in our understanding of industry phenomena. While contributing new insight, these methods are often not adequate to enable understanding of the complex interactions that lead to many of the industry's pervasive social and technical problems. One means of addressing these limitations is for the construction research community to complement prevalent quantitative and case study methodologies with qualitative theory-building methodologies, specifically ethnographic studies or those based on detailed and long-term observation of project environments. This paper identifies the critical need for theory-building methods and their methodological conventions, challenges, and opportunities. Specifically, the paper focuses on data collection in ethnographic studies and analysis of that data through the use of grounded theory. Through better understanding and more widespread use of theory-building methods, the construction research community can provide a needed complement to the current prevailing methods and greatly aid the maturation of our important field. © 2010 ASCE.

Catella N.D.,Simpson Gumpertz and Heger
Forensic Engineering 2015: Performance of the Built Environment - Proceedings of the 7th Congress on Forensic Engineering | Year: 2015

Finite element analysis can be a useful tool for structural failure investigation. It enables engineers to compare and quantify potential failure modes and it allows interested parties to visualize failure sequences. Finite element analysis is used less frequently for support of structural failure investigation than it is for design and there are several important differences. In design, it is typically sufficient to make conservative assumptions; in failure investigation, conservative assumptions may preclude potential failure modes. Therefore, it is important to characterize every aspect of the model as accurately as possible, thoroughly check assumptions, and understand the limitations of the model. This is especially true for nonlinear analyses, where models may be sensitive to small changes. For situations where the structure cannot be adequately characterized, finite element analysis may still prove useful by identifying trends resulting from variation in certain parameters that may have contributed to failure. Two case studies are presented to illustrate the advantages and pitfalls of finite element modeling in structural failure investigation: collapse of a mast-climbing scaffolding machine and deterioration of concrete railroad ties. © 2016 ASCE.

Morse-Fortier L.J.,Simpson Gumpertz and Heger
Forensic Engineering 2015: Performance of the Built Environment - Proceedings of the 7th Congress on Forensic Engineering | Year: 2015

At the first forensic engineering congress, shortly after investigating damage to residential structures from Hurricane Andrew, I presented a paper on the shortcomings of the prescriptive building code. Specifically, I argued that a prescriptive code is typically based upon past experience, that this experience is out of date as soon as it is acquired, and that prescriptions will always break down at the margins of design innovation. I concluded by proposing that all residential structures in areas of severe hazard be engineered to withstand the expected loads. As noted, Hurricane Andrew damaged houses throughout southern Dade County, Florida. Despite a strict building code, after a 31 year hiatus from major hurricane damage, the region's housing stock proved much more vulnerable than expected. However, setting aside the prevalence of lost roof covering, broken windows, and the complete destruction of mobile homes, relatively few wood-frame houses suffered severe structural damage. Consequently, those that did suffer damage became objects of intense investigation and engineering scrutiny. The results of that scrutiny included changes to the Building Code. While these changes are welcome and necessary, they repeat the historical pattern of codifying elements necessary to fix problems observed in the housing stock that suffered damage. Among these, damage to gable-end walls stands out among issues that led to Code revisions. Presently, with an additional 23 years of experience since Hurricane Andrew, and with more recent experiences from other storms, Florida retains a largely prescriptive Residential Building Code. However, for High Velocity Hurricane Zones, the Code directs the building designer to use the performance standards of the Florida Building Code for Buildings, based upon the International Building Code. Therefore, at least for those areas considered to be High Velocity Hurricane Zones, Florida does not allow for the use of the prescriptions contained within the Code. This paper reviews the Code evolution briefly, and revisits the question of whether and how well a prescriptive code can adequately insure the integrity of residential structures in Florida. © 2016 ASCE.

Bell G.R.,Simpson Gumpertz and Heger
IABSE Conference, Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges - Report | Year: 2015

Rapid changes in technology coupled with global societal developments and challenges require a new breed of structural engineer, more broadly capable than ever before. We must define a new set of structural engineering competencies and dramatically overhaul our approach to the engineer's education and development. This will require a massive collaboration among stakeholder organizations world-wide. The future of our profession depends on it.

Nelson P.E.,Simpson Gumpertz and Heger
ASTM Special Technical Publication | Year: 2016

This paper reviews some of the pressing issues and challenges presented in papers from the first two ASTM exterior insulation and finish systems (EIFS) symposiums (ASTM STP1187-September 1992 and ASTM STP1269-March 1995) and compares them to EIFS today. What has changed, and what has not, over the last two decades? What pressing problems from 20 years ago have been addressed (e.g., absence of many options for drainable systems)? What new problems have emerged (e.g., additional code-mandated restrictions and concerns with combustible foam plastics as part of exterior wall assemblies)? What additional benefits of EIFS have emerged or been more fully appreciated in recent years (e.g., code-mandated emphasis on continuous exterior insulation)? © Copyright 2016 by ASTM International.

Taylor A.J.,Simpson Gumpertz and Heger
ASTM Special Technical Publication | Year: 2016

A drainable exterior insulation and finish system (EIFS), which is lightweight and improves enclosure thermal performance at a relatively low cost, is a valid option for over-cladding existing underperforming facades. This article describes a process for evaluating the suitability of a drainable EIFS for over-cladding an existing facade and, if it is suitable, the steps for successful design and installation of drainable EIFS over-cladding. This article also describes steps for existing facade investigation, code validation, and the thermal improvement benefit of EIFS over-cladding; design, detailing, and specifying; and quality assurance/quality control (e.g., mock-ups and testing) before and during construction. The article will also touch on the important design considerations of fire resistivity, designing for drift and drainage, and missile impact resistance. © Copyright 2016 by ASTM International.

Zarghamee M.S.,Simpson Gumpertz and Heger
Pipelines 2016: Out of Sight, Out of Mind, Not Out of Risk - Proceedings of the Pipelines 2016 Conference | Year: 2016

This paper details the procedure for pressure-induced thrust restraint design of concrete pressure pipelines with tied joints at elbows, tees, and end-caps through several examples following the current AWWA manual of practice M9. The paper discusses the problems that led to the development of the procedure, the design philosophy, and the development of a simplified approach for thrust restraint design. It discusses the assumptions embedded in the simplified approach. It presents the calculation flow diagram and describes the steps in the calculation for three different examples. These examples are selected for discussion in the order of their complexity: an end cap, a simple bend with welded joints, and a bend with mechanically harnessed joints. Through the use of examples, the paper shows how the calculation for each step is performed. Applicability of the procedure developed in the current AWWA Manual of Practice M9 to thrust restraint design of other pipes is briefly discussed. © 2016 ASCE.

Patel A.K.,Simpson Gumpertz and Heger
ASTM Special Technical Publication | Year: 2015

Water-resistant barrier requirements (i.e., code and industry guidelines) within portland cement-based plaster (stucco) wall cladding systems have changed over the past decade. Various types of water-resistant barriers have been developed, and different configurations for their use within stucco wall cladding systems have been implemented successfully. However, improper use or lack of a proper water-resistant barrier can lead to deterioration or corrosion of exterior wall components, including sheathing, framing, and insulation, and can eventually result in water leakage into interior spaces. This paper will review the changes in water-resistant barrier requirements for exterior stucco wall cladding systems. It discusses the mechanisms for failure and water leakage paths through stucco cladding systems and water-resistance barriers, presented through various case studies. Laboratory testing of various types of water-resistant barrier materials will also be performed. Comparisons of the results are explored along with examples of actual in-service installations. Copyright © 2015 by ASTM International.

Hamburger R.O.,Simpson Gumpertz and Heger
AEI 2011: Building Integrated Solutions - Proceedings of the AEI 2011 Conference | Year: 2011

In 2001, the Applied Technology Council (ATC) initiated the ATC-58 Project under contract to the Federal Emergency Management Agency (FEMA). Under this project, ATC is developing next-generation performance-based seismic design criteria for new and existing buildings that will be published as FEMA P-58. Unlike present-generation performance-based design criteria, which characterize structural and nonstructural performance in terms of standardized damage states, the P-58 criteria characterize structural performance in terms of the consequences of earthquake damage including: casualties; repair and reconstruction costs, expressed both in monetary and energy/carbon expenditures; and occupancy interruption time. The performance of nonstructural building components including architectural, electrical and mechanical components and systems is integrally considered with that of the structure. Following a methodology originally developed by the Pacific Earthquake Engineering Research Center, the P-58 procedures revolve around a building performance model that includes fragility and consequence functions for each of the damageable components and systems of significance. Monte Carlo simulation procedures are used to assess potential losses for: individual earthquake shaking intensities; scenario earthquake events, considering uncertainty in ground motion intensity; and, over a period of time, considering uncertainty in the magnitude and distances of scenario events that will occur. Project completion is scheduled for late 2011.

Loading Simpson Gumpertz and Heger collaborators
Loading Simpson Gumpertz and Heger collaborators