Journal of Performance of Constructed Facilities

The Pentagon was constructed between September 1941 and January 1943. A substantial renovation of the entire $6.6\text{million}\mathrm{sq}\mathrm{ft}$ $\left(\mathrm{610,000}\mathrm{sq}\mathrm{m}\right)$ facility began in 1999 and is scheduled for completion in 2010. On September 11, 2001, a hijacked commercial airliner crashed into the building. One-hundred eighty-nine persons were killed and a portion of the building was damaged by the associated impact, deflagration, and fire.

On September 11, 2001, an airliner was intentionally crashed into the Pentagon. It struck at the first elevated slab on the west wall, and slid approximately $310\mathrm{ft}$ $\left(94.5\mathrm{m}\right)$ diagonally into the building. The force of the collision demolished numerous columns and the façade of the exterior wall, and induced damage to first-floor columns and the first elevated slab over an area approximately $90\mathrm{ft}$ $\left(27.4\mathrm{m}\right)$ wide and $310\mathrm{ft}$ $\left(94.5\mathrm{m}\right)$ long. None of the building collapsed immediately. The portion that remained standing, even after an intense fire, sustained substantial damage at the first-floor level.

On September 11, 2001, the reinforced concrete structure of the Pentagon Building was able to resist, without collapse, the impact of a large commercial airliner despite the total loss of 26 columns and severe damage to 15 columns at the ground level. The ensuing fire and related fire-fighting activities led to the collapse of a portion of the building approximately one-half hour after the impact. In this paper, the reasons for the demonstrated toughness of the reinforced concrete structure are examined and attributed to use of spiral columns, effective splicing of reinforcing bars, strong girders, and short span lengths.

An overview of fire damage sustained by the Pentagon structural elements in the September 11, 2001, terrorist attack is provided. The fire intensity in some compartments of the affected areas inside the Pentagon was approximated to be between those of the two standard fire exposures ASTM E119 and E1529, based on the observed fire damage and estimated fuel load. Thermal analyses of the structural columns and beams were performed using the standard fire exposures to demonstrate the increased vulnerability of these structural elements once the concrete cover was lost.

The devastation in the September 11, 2001 terrorist attack on the Pentagon was reduced by the building’s resilient structural system. The continuity, redundancy, and energy-absorbing capacity embodied in this system should be incorporated in structures whose resistance to progressive collapse is important. Research should be conducted in the practical implementation of these measures for mitigation.

Blasting is common in the coal industry to remove rock overburden so that the exposed coal can be mechanically excavated. The ground vibrations and air blast produced by blasting are often felt by residents surrounding the mines. There has been a trend for regulatory authorities, especially those concerned with the environment, to impose low limits on blast vibration levels in response to community pressure, based on human perception and response to vibration. This paper reports the findings of an extensive study on a house which was located adjacent to a coal mine. The house was monitored for over $1\text{year}$ and was subjected to ground peak particle velocity (PPV) ranging from $1.5\text{to}222\mathrm{mm}∕\mathrm{s}$ . The house was instrumented with accelerometers to measure its dynamic response due to blasting and it was also monitored for cracks before and after each blast. Based on this study, ground motion amplifications along the height of the structure have been established. A simplified methodology presented in this paper has been used to estimate the ground PPV at which cracking is likely.

A large number of specialty repair concrete products are currently marketed and new products are being continually introduced leaving clients, engineers, and designers bewildered. The paucity of information on the mechanical and thermal properties of a given product complicates material selection. These difficulties force designers to adopt materials that have properties close to those of the original concrete. In so doing they often reject advantages offered by polymer-based products now on the market. The challenge is to understand the properties of each material and select the appropriate one. To assure predictable performance, the designer must have a good knowledge and understanding of the properties of the repair material, how it will interact with the environment in service, and a clear description of maintenance procedures and intervals. Typical properties of currently used polymeric materials in relation to the important aspect of selection based on compatibility with in-service conditions and suitability with the application procedures of the job are discussed.

Good roof performance requires proper design and specification, quality materials, professional workmanship, and proactive maintenance. Shortcomings in any phase of roof asset management will compromise performance and shorten service life. The objective of this study was to identify relationships between roof asset management processes and performance problems identified in an inventory of United States Army low-slope membrane roofs. First a review of literature pertaining to roof asset management was conducted. Next, a large Army roof inspection database was analyzed to identify the types and relative frequencies of common defects, and their impacts on performance. The writers and experienced inspectors then applied both engineering and field experience to provide expert analysis of the data. Approximately 75% of the performance problems in the sampled inventory were attributable to deficiencies caused by factors other than natural degradation. The writers conclude that roof performance can be significantly improved by strengthening quality assurance processes during installation, particularly by ensuring that installers comply with contract specifications and utilize industry-accepted construction practices.

Observations, data, and analyses that were used to investigate the cause of distress to a single-family residence located adjacent to a major highway cutslope are presented herein. The investigation revealed that the distress in the single-family residence was caused by a deep, large excavation-induced landslide. The excavation, which was made to widen an existing highway, helped trigger the landslide by exposing geologic structures on the cutslope and by unloading the toe of the slope. This case history illustrates some of the ramifications of large highway excavations in natural slopes surrounded by urban areas, e.g., exposing significant geologic features such as shear zones, faults, and folds; the importance of investigating and explaining signs of movement at both the top and toe of a slope; the impact of rainfall on the movement of a large slide mass; and that large slide masses can undergo slow, episodic movement instead of sudden, large movement.

If the performance of a constructed facility fails to conform with what is intended or anticipated, the engineer-of-record for the facility can be charged with negligence and may bear the liability for damages arising from that failure. An engineer’s negligence is assessed by measuring the engineer’s actions relative to the “standard of care” of the profession. This paper briefly describes the meaning and application of the standard of care, and addresses the question, “What is ‘care’ with regard to engineering?” To examine that question, the paper introduces the five elements of the ethic of care as defined by Joan Tronto: attentiveness, responsibility, competence, responsiveness, and integrity, and builds on work by Marina Pantazidou and Indira Nair that identified care as an ethical framework suitable to provide guidance for engineering activities. The paper explores the applicability of the ethic of care to engineering practice by examining how the elements relate to the performance of engineers described in published case studies of engineering failures. The standard of care question raised in each case study is evaluated within the ethic of care framework, and an assessment is made of the engineer’s exercise of the elements of the ethic of care.