Journal of Performance of Constructed Facilities

An analysis of the levelness of three residential floor slabs constructed on-grade in the Phoenix, Arizona, metropolitan area is presented. The slabs were built using typical methods by a trade subcontractor for a large production builder in different subdivisions. Measurements of the elevation of the floor slabs were made at 0.3 m (1 ft) spacing across the entire surface of all three slabs within the first week after concrete placement. The resulting elevation data were then used as input in several different analytical techniques, including the maximum elevation difference, maximum slope, $F_L$ local, and $F_L\text{.}$ Special consideration was given to the sample size effects and the repeatability of the results for different samples. All of these methods were found to exhibit dependency on sample size or location, leading to undesirable characteristics. An analysis based on the three-standard-deviation range of the elevation measured from a sample of about 80 points widely spread across the surface of the slab is shown to provide an effective balance for the minimization of both sampling and nonsampling error terms.

In this case study, a number of gunite swimming pools exhibited extensive map or alligator cracking that caused rough and uneven surfaces. The nature of the cracking pointed to alkali-silica reaction (ASR) as the cause of the cracking. Four test methods, the uranyl acetate method, petrographic examination, chemical analysis by electron microprobe, and X-ray diffraction, were used to investigate the presence of ASR within the gunite. Results showed (1) some evidence of ASR gel within the gunite using uranyl acetate; (2) the potential existence of alkali silica gel throughout the cement and within the fractures of the sand grains based on petrographic examination; (3) elevated levels of total alkali, indicating a potential for ASR to occur based on chemical analysis; and (4) tiny inclusions of thermonatrite (commonly found in ASR gel) based on X-ray diffraction. Results from each of the four test methods suggest, albeit inconclusively, the existence of ASR in the gunite. Additionally, the results of all of the four test methods did not contradict each other. Accordingly, it can be stated with some certainty that the distress in the gunite was due to ASR.

The research presented in this paper resolves several measurement issues pertaining to the experimental modal analysis of lightweight steel floor systems. This investigation represents a first step toward collecting more extensive data on the dynamic behavior of steel floor systems. These data can then be used to improve design and analysis procedures for assessing the vibration serviceability of a floor system before construction. Some of the issues investigated herein are the selection considerations for the data acquisition system and transducers, the appropriate type and placement of excitation, and fast Fourier transform processing considerations.

Fourteen Texas SPS-3 test sites were studied to determine the effectiveness of preventative maintenance treatments. These sections were built on four highway classifications (IH, US, SH, and FM) in different climates and with different levels of traffic and subgrade support. Almost all 14 SPS-3 sites were given preventative maintenance treatments (thin overlay, slurry seal, crack seal, and chip seal) in Fall 1990. The distress score concept used by the Texas Department of Transportation (TxDOT) was adopted in this study to judge the effectiveness of preventative maintenance treatments. TxDOT has used this concept since the early 1980s, though the utility factors have been revised few times. The distress score quantifies the visible surface wear due to traffic and environmental influences. Only very few sections experienced premature failures on the SPS-3 sites in Texas. In many cases, superior underlying pavement conditions have been found. The chip seal has the most sites in which it is rated the best performer. The chip seals performed well on a wide range of pavement conditions. In fact, chip seals have the highest distress score for both high and low traffic areas. When initial cost is considered, crack seal provides the best alternative for low traffic routes that have a sound underlying pavement structure. For high traffic routes, chip seal is a better choice. However, a thin overlay is the most effective for rut resistance. Since the thin overlay has the highest initial cost, it is best used on high traffic routes where rutting is a major concern. If rutting is not a concern, chip seal is the best choice for a high traffic area. The treatments applied to US84 sections were too late and did not reach seven years of life as normally was expected, which reconfirms that the timing for preventive maintenance treatment is very important.

Over 500 failures of bridge structures in the United States between 1989 and 2000 were studied. The age of the failed bridges ranged from 1 year (during construction) to 157 years, with an average of 52.5 years. The most frequent causes of bridge failures were attributed to floods and collisions. Flood and scour, with the major flood disaster in 1993, contributed to the frequency peak of bridge failures (almost 53% of all failures). Bridge overload and lateral impact forces from trucks, barges/ships, and trains constitute 20% of the total bridge failures. Other frequent principal causes are design, detailing, construction, material, and maintenance. Comparison made among three periods of similar studies (1977–1981, 1982–1988, and 1989–2000) revealed almost similar trends, with most failures occurring during the bridge’s service life. Also, human-induced external events occurred frequently in all three periods, but were most dominant in the first and third periods. Technological advances in information systems have a great impact on data collection and analysis.

A total of 225 building failures in the United States from 1989 to 2000 were recorded in this study. The result shows that failures of low-rise buildings constitute about 63% of all cases, followed by multistory buildings as a distant second. In terms of their functions, apartments are the most frequent to fail. External events and construction and maintenance deficiencies have been identified as the most frequent principal causes. External events include rain, wind, snow, vehicular impact, and collision. Construction deficiencies encompass improper renovation, unplanned demolition, poor workmanship, and unsafe excavation operations. Maintenance deficiencies are associated with building deterioration that was overlooked and improperly maintained. A comparative analysis conducted between this study and two previous studies indicates an inclined trend of relative failure occurrences of low-rise and multistory buildings. The study also suggests that, despite the recent enhancement of information technology, current sources of information are still incomplete. The creation of new complete databases, further improvement of information sources, and their dissemination through the Internet are deemed essential to prevent building failures from recurring.