Poston R.W.,WDP and Associates |
Dolan C.W.,University of Wyoming
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2012
The structure of the current ACI Building Code has remained essentially unchanged since 1963 when ultimate strength was added. Knowledge has expanded with time through practice and research. In structural engineering, knowledge is also gained from the behavior of structures in extreme events. The Code reflects changes brought about by the addition of new materials and construction techniques, insights into behavior and development of technology. In the 318 Code, new provisions refl ecting these advances in knowledge have been added to each subsequent edition of the Code. Given that the fundamental structure of the Code that has remained unchanged for almost 50 years, ACI Committee 318 has taken a fresh perspective and reorganized the Code to provide a more user-friendly back bone for design. With this structure, it is believed that changes made to future versions of the Code will be more transparent and obvious such that designers do not miss new requirements. This new framework for the 318 Code will be instituted for the 2014 edition.
Freytag D.,American Concrete Institute |
Kesner K.,WDP and Associates |
Poston R.W.,WDP and Associates |
Poston R.W.,American Concrete Institute |
Bondy K.,American Concrete Institute
American Concrete Institute, ACI Special Publication | Year: 2012
The title of this paper borrows from the 1981 book by Harold Kushner entitled "When Bad Things Happen to Good People". In his book, Kushner attempts to explain why a universe created by a deity who is of a good and loving nature still holds so much pain and suffering for good people. In the context of this paper, the title is meant to be an epigraph that suggests that although a building may be meeting its intended structural purpose, bad things, at least as they are perceived, can happen during design, construction and service of the building that bring its safety into question. One of the main circumstances that can bring into question the integrity of an unbonded post-tensioned building is corrosion of the strands and anchorage components. This paper will highlight the unnecessary demise of a modern high-rise post-tensioned structure due to corrosion, and contrast that outcome to several existing unbonded post-tensioned buildings that experienced corrosion and were successfully repaired and continue to function.
Varney J.C.,Huitt Zollars Inc. |
Brown M.D.,WDP and Associates |
Bayrak O.,Environmental and Architectural engineering |
Poston R.W.,WDP and Associates
ACI Structural Journal | Year: 2011
The performance of improperly constructed beams is of particular concern in the repair of concrete structures. Not only is there uncertainty about the actual as-built strength and what measures may improve capacity, but also the presence of improper structural details may lead to litigation concerning what structural repairs are really necessary to restore perceived loss of strength. For the specific case of shear, there is value in knowing a reasonable and safe approximation of the shear capacity of improperly detailed beams. To study the effect of improperly anchored stirrups on the shear strength of reinforced concrete beams, four 13 × 24 in. (330 ×610 mm) reinforced concrete sections were fabricated with varying proper and improper shear reinforcement details and loaded to failure. Current ACI 318 and AASHTO LRFD code provisions were used to compare the resulting failure loads from tests with calculated nominal capacities. The experimental results suggest that reinforcement anchorage, as tested, has no significant effect on the shear capacity of a reinforced concrete section. © 2011, American Concrete Institute. All rights reserved.
Cyphers R.A.,WDP and Associates |
Whitlock A.R.,WDP and Associates
ASTM Special Technical Publication | Year: 2010
A testing program was conducted to compare the results of three different freeze/thaw test procedures on molded brick. The bricks were tested in accordance with ASTM C67-02a (performed continuously without weekend interruptions), Dutch Standard NEN 2872-89 (Nederlands Normalisatie-Instituut (Netherlands Standards Institute - NEN)), and a non-standardized test similar to tests performed by other researchers that included boiling the brick prior to freezing, referred to as the "Boil to Freeze" test. The effects of the tests were compared by assessing visual damage and measuring changes in ultrasonic pulse velocity measurements and 24 h cold water absorption values on each brick before and after freeze/thaw testing. In addition to the freeze/thaw tests, the bricks were also tested for basic physical properties including compressive strength and absorption. A statistical analysis was made of the test results to compare the effects (severity) of three different freeze/thaw tests. Copyright © 2010 by ASTM International.
Norvell J.,WDP and Associates |
Grill J.,WDP and Associates
Forensic Engineering, Proceedings of the Congress | Year: 2010
Settlement of subgrade resulting in poor performance of slabs-on-grade is a common problem in structures. On a recent project, significant amounts of soil slurry infiltrated the basement of a large manufacturing warehouse. The washout of the underlying soil and resulting settlement was sufficient to cause visible dynamic deflections when subjected to routine forklift traffic. These observed conditions indicated the void space beneath the slabs would be moderately deep and widespread. This paper discusses the application of surface penetrating radar (SPR) to identify the locations of subgrade voids and provides a comparison to other nondestructive test (NDT) methods. Impulse response and impact-echo can be used to locate these voids; however, these methods have inherent limitations and often require more destructive testing for confirmation of results. Due to its accuracy and ease of use, SPR is an ideal NDT method for this application.