Journal of Performance of Constructed Facilities

The behavior of the World Trade Center Tower 1 on September 11, 2001 is studied in light of experimental data on the effect of elevated temperature on mechanical properties of structural steel. It is concluded that the damage inflicted by aircraft impact on the insulation of the core framing was the dominant factor in the collapse of the structure.

This paper presents an innovative three-dimensional performance-based earthquake engineering assessment methodology for gated spillways. Several functionality and structural stability limit states are defined. The functionality of the gates is tackled by assessing seismic demand-to-capacity indices along a success path leading to postearthquake gate opening. As an application example, the proposed methodology is applied to an existing gated spillway built in 1927. Finite element incremental dynamic analyses are performed for six sets of spectrum compatible ground motions with return periods ranging from $200\text{to}\mathrm{10,000}\text{years}$ . Linear transient dynamic analyses are first performed to compute internal force resultants, displacements, and distortions in structural components. For the concrete structures, the forces from the analyses are input in a postprocessor to compute sliding safety factors using a three-dimensional extension of the gravity method accounting for concrete cracking. The assessment of the hoist supporting structure and gates is done using current steel member demand-to-capacity checks. The actual failure mode hierarchy is identified and found unsatisfactory as the concrete structures and steel lifting tower anchors are expected to fail prematurely. Specific performance criteria and related ground motion return periods are proposed (1) to maintain normal gate opening; (2) to maintain the load bearing capacity of the steel towers and bridge; (3) for life safety of personnel; and (4) to avoid an uncontrolled release of the reservoir.

Advancements in fiber-reinforced polymers (FRPs) have made this an attractive material for rehabilitation and strengthening of bridge superstructures. FRP has primarily been used with the intention of increasing the bending strength of bridge members. However, this paper investigates the use of externally placed FRP strips to increase shear capacity of short-span, $5.7\mathrm{m}$ $\left(19\mathrm{ft}\right)$ , precast concrete channel beam bridges. A statewide survey revealed that as many as 389 bridges in the state of Arkansas are comprised of these members. Notably, beams within these bridges were designed under provisions that did not require shear reinforcement. In this research, four sections were retrofitted using carbon fiber-reinforced polymer (CFRP) strips and load tested to failure to measure the repair effectiveness. The performance of the retrofitted sections far exceeded that of unretrofitted sections. It was concluded that the addition of the CFRP repair increased the deflection ductility at least 123%. In addition, beams retrofitted with the CFRP strips experienced at least 26% more deflection after the initiation of a shear crack; therefore reducing the risk of a catastrophic failure.

Conventional asphalt bridge expansion joints used in low-temperature regions generally show cracking within the first $2\text{years}$ . To improve the low-temperature performance of these joints, the commercial MEIJIA asphalt binder commonly used in bridge expansion joint construction was modified with two polymers: thermoplastic rubber and rubber. The goal is to find an optimum combination of polymers, binders, and aggregates to improve the performance of asphalt expansion joints in low-temperature regions. The polymer modified binders and mixtures were evaluated for their low-temperature properties using ductility, penetration, indirect tension, and bending tests. The study indicates that performance of these joints at low temperature can be enhanced significantly with the right combinations of polymers, binders, and aggregates. Four expansion joints made with the polymer modified asphalt mixtures were installed on two bridges in a cold region. A construction procedure was also developed to install these joints properly to minimize low-temperature cracking along the interface between the joint and bridge deck. After $7\text{years}$ of service, the four joints show good performance without any visible cracking or rutting.

Usually the status of a bridge is determined by its structural capability and material strength. Consequently a lot of researchers have studied the failure, the fatigue, and the deterioration of the structure in terms of the structural function of a bridge. However, the safety of a bridge may be affected simply by the damage of one of its components. Therefore this paper utilized a systematic classification and statistical analysis based on the thousands of sets of existing bridge inspection data collected in Taiwan to reach the following goals: (1) assess the deterioration rate for each component of a bridge; (2) determine the lifetime of each component based on the performance index; and (3) find out the preventive and essential maintenance strategy for each bridge component with an empirical method.

The use of rammed aggregate pier (RAP) foundations for support of retaining walls and earth fill embankments has increased in recent years to become a geotechnical solution for rapid construction of earth structures in soft ground conditions. A nominal $6\text{-}\mathrm{m}$ mechanically stabilized earth wall was constructed over piers installed in relatively compressible soil to investigate the performance of RAP foundation elements in terms of stress-deformation and settlement behaviors for such applications. Geotechnical instrumentation consisting of total earth pressure cells, settlement plates, and vibrating wire piezometers was installed within the pier elements and at the foundation surface for short- and long-term monitoring of pier response. Monitoring data indicate: (1) mobilization and concentration of vertical stress on pier elements and matrix soil; and (2) load transfer response for the boundary condition associated with support of geogrid-reinforced earth fill. The practical implications of the experimental research findings are briefly discussed.

The application of this study is to use helical anchors as a foundation system for small wind tower $(1–10\mathrm{kW})$ guyed cables. Helical anchors are currently used to anchor guyed cables of cell or transmission towers. However, the increased dynamic vibrations a wind turbine adds to the tower and foundation system under working loads, as well as extreme environmental conditions (e.g., straight line winds, ice load, or sudden furling shocks), require additional knowledge about the behavior of helical anchors. These field conditions were simulated in this study from tower-instrumented field data on wind speed and tower response. These tower responses were then transmitted to the helical anchors through an extensive, large-scale testing program that included monitoring the performance of the helical anchor foundation under dynamic loads, subject to natural variations in both wind regimes, precipitation (water level) and variations in helical anchor geometry. This paper compares the uplift prediction methods used in helical anchor design as well as discusses the effects of long-term dynamic loading and fluctuating water table on helical anchor performance.

In June of 2007, the Ohio University research team visited the $610\text{-}\mathrm{mm}$ $\left(24\text{-}\mathrm{in.}\right)$ diameter corrugated high density polyethylene (HDPE) pipeline structure located under $30.5\text{-}\mathrm{m}$ $\left(100.0\text{-}\mathrm{ft}\right)$ high embankment of Interstate Highway 279, near Pittsburgh. This visit marked the 20th year of the field research project. The team conducted visual inspections of the pipeline along with in-situ pipe drilling experiments. The in-situ pipe wall drilling experiments conducted at the site induced strains in the pipe wall. However, the strains dissipated completely within $5\mathrm{s}$ . This demonstrated the nature of the viscoelastic material and a lack of significant stress levels existing in the pipe wall. These in-situ pipe wall drilling experiments are an innovative procedure for showing the stress relaxation capability of HDPE. Localized cracking of the pipe end was observed at joints positioned under more than $21.3\mathrm{m}$ $\left(70.0\mathrm{ft}\right)$ soil fill and where two sections of Type C pipe were connected. The cracking observed in 2007 appeared to show insignificant changes from those observed during the 2002 inspections. No signs of structural distress were detected inside pipe sections that were under less than $21.3\mathrm{m}$ $\left(70.0\mathrm{ft}\right)$ of soil fill. The pipe deflections, which were measured under $30.5\mathrm{m}$ (100.0 ft) of fill, have been stable for a number of years. The horizontal deflection changed by only 0.3% over the past $17\text{years}$ . The vertical deflection has hardly changed over the past 18 years. The pipe circumferential shortening has increased by less than 0.2% over the last 18 years. Finally, the results of the laboratory tests showed that no noticeable changes took place in the basic engineering properties of the HDPE pipe material over the past 20 years.

Effective asset management strategy of civil infrastructure systems requires integration of technical and financial plans. This is particularly true in managing water mains, which requires knowledge of their current condition and their forecasted remaining useful life. This paper presents a model designed to forecast the remaining useful life of cast iron water mains. The model is easy to use and its generated results are utilized in determining condition rating of the water mains being considered. The model considers factors related to pipe properties, its operating conditions, and the external environment that surrounds the pipe. In addition, it overcomes limitations associated with existing models. Three different data-driven techniques are considered in the model development; each is used to study the relationship between remaining useful life and a set of deterioration factors, and to forecast remaining useful life of cast iron water mains. These techniques are multiple regression and two types of artificial neural networks: multilayer perceptron; and general regression neural network. The data used in model development were acquired from 16 municipalities in Canada and the United States. The results produced by the developed models correlate well with the actual conditions.

Potable water treatment is one of the most challenging and complex systems that municipalities need to deal with considering limited resources. A study from mid-90s showed that the continuously deteriorating Canadian water supply system would require $3.1 billion to bring the system at satisfactory level. Drinking water treatment plants (WTP) include several components, such as tanks, basin, and pumps. Operators are able to spend a small portion of the available resources or their plant’s infrastructure and equipment compared to water quality and day-to-day operational activities. The research presented in this technical paper aims at developing condition assessment model(s) for the WTP components. Essential condition parameters of WTP include technical, physical, environmental, and operational aspects. To determine the condition index of a WTP component, value additive multi-attribute theory has been used where average weights and scores are considered for the model parameters. Data on WTP conditions are collected from experts and consultants across Canada and the United States. It is concluded from the model results that the average condition index for settling basins, ranges from 9.6 (best scenarios) to 1.9 (worst scenarios) and from 9.6 to 3.4 for pumps. Analysis reveals that, for tank and basins, design and construction parameter is the most important parameter for WTP condition, while the operational parameter is the most important one for pumps. The developed models are expected to benefit academics and practitioners (municipal engineers, consultants, and contractors) to prioritize inspection and rehabilitation planning for existing water treatment plants.