Journal of Performance of Constructed Facilities

A critical step in selecting the most appropriate repair strategy for a distressed concrete structure is to determine the corrosion status of reinforcing bars. Because of the complexity of the corrosion process, it is prudent to involve personnel who are experienced in the corrosion of steel in concrete. The corrosion engineer may employ a variety of tools to help make an assessment of the corrosion conditions. This paper provides an overview of the corrosion of steel in concrete and presents some nondestructive electrochemical tools that are commonly used in corrosion investigations. The objective is to provide the repair specialist with basic information to allow effective communication with the corrosion engineer. Electrochemical principles involved in the corrosion of steel in concrete are reviewed. Subsequently, the half-cell potential method, the concrete resistivity test, and the linear polarization method are discussed. The principles of operation and the inherent limitations of these methods are emphasized.

In 1993 after 9 years of use, one of the wooden blades of a windmill was struck by lightning. After demounting, the damaged blade was handed over to the Technical University of Denmark, Lyngby, for the investigation of potential fatigue damage. This paper presents an experimental determination of the residual strength of the glued-in bolts that served as the blade to rotor hub connection in the windmill. The load history of the bolts, the test method, the observed fracture modes, and the force displacement curves are presented along with the recorded residual strength of the bolts. The bolts with a length of 500 mm had a special hollow tapering giving them a higher load-bearing capacity than solid bolts of equal dimensions. An FEM analysis confirms the higher load-bearing capacity. The mean residual stength was found to be 362 kN with a standard deviation of 37 kN, which is 95% of the predicted strength based on short-term tests on similar bolts. At fracture, a displacement between 0.4 and 1.0 mm was observed. In the majority of failures, the bolts were pulled out like a cork from a bottle.

Boiling failure that results from drilling for installation of a new pneumatic piezometer in the final grade of a deep excavation in Taipei, Taiwan, is presented in this case study. The extent of the damage includes the boils of a mixture of soil and water entering the bottom of the excavation, heave of the center posts, inclination of internally horizontal struts, subsidence and excessive lateral inward deformation of the diaphragm wall, and significant ground settlement. The corresponding emergency efforts to minimize the loss are addressed. In addition, the paper focuses on two remedial schemes to resume excavation following the incident. One is the grouting measure adopted by the contractor, and the other is a dewatering scheme proposed by the writers. Constructibility, safety, schedule, and cost of the two schemes are compared. It is demonstrated that a dewatering scheme should be considered where applicable to mitigate against similar incidents in the Taipei metropolitan area in the future.

Various criteria have been suggested throughout the geotechnical and construction community for maximum allowable differential movement for foundation systems. However, the writers have found very few papers pertaining just to slab-on-grade systems. Furthermore, our literature review indicates that most of these criteria have been developed through studies of soil settlement, irrespective of other modes of soil movement, and do not necessarily pertain to residential slab-on-grade structures. There are many different soil/geologic processes that can operate at a given site, each of which can affect the performance of an overlying structure in a different manner. For example, at the same development a house founded on fill of varying depths (differential fill) may settle somewhat uniformly, producing little distortion, whereas a house founded on expansive bedrock may experience “heave” or “edge curl,” resulting in higher levels of foundation distortion. The house settling uniformly may experience an overall differential movement of 2.5 in. with only minor damage, whereas the house affected by expansive soil influence may experience greater levels of damage with an overall differential movement of only 1.50 in. This is because the angular distortion is much greater along the area of influence. Understanding various patterns of movement for different soil conditions is very important and should be considered when designing or reviewing residential slab-on-grade foundations.

The performance of cold in-place recycled asphalt roads in Iowa is systematically reviewed. Out of 97 recycled roads, a sample of 18 roads was selected that had various traffic counts, ages, geographic regions, subgrade conditions, and hot mix asphalt overlay characteristics. The performance was rated both quantitatively and qualitatively. The results indicate that the roads are performing well. It is apparent that cold in-place recycled asphalt is effective in mitigating reflection cracks, and few problems with rutting were observed. Subgrade instability is found to be the only cause of complete failure in a recycling project. The expected service life, based on the first 10 years of performance, is predicted to be 15–26 years.

A fire broke out in the lift control room of a new high-rise office tower block. The initiating source of the fire was traced to a lift group control panel and the area around the neutral incoming terminal of a circuit breaker. Laboratory inspection and metallographic examination also indicated that there was highly localized overheating at the neutral incoming terminal of a circuit breaker. The cause of the fire was attributed to the presence of a localized hot spot that was most likely due to a loose connection and/or the existence of a partially broken wire at the crimped end of the wire to the lug. Such factors are typically associated with poor workmanship during cable termination. Adherence to proper wire termination techniques and conducting a thermographic survey of the completed installation could have prevented the fire.