Journal of Performance of Constructed Facilities

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Tunnel distress occurs often. Tunnel leakage, segment dislocation, and section deformation seriously affect tunnel construction safety and normal operation. Currently, mainly the traditional monitoring technology is used in tunnel distress monitoring. This kind of technology has the problems of low monitoring efficiency, slow speed, inaccurate measuring points, and so on. With the development of science and technology, three-dimensional laser scanning monitoring technology (3D LSMT) has fast acquisition speed, a comprehensive monitoring range, and high acquisition accuracy. This review collected the world’s more advanced monitoring technologies, such as optical fiber sensing technology (OFST), photogrammetry (PT), and so on. Firstly, these technologies were introduced and compared with 3D LSMT. Then the theoretical basis of 3D LSMT was analyzed. Three-dimensional LSMT uses the captured high-density point cloud to extract the tunnel structure information and realizes the rapid processing of point cloud data through automated software. Finally, the use of 3D LSMT for segment dislocation, tunnel deformation, and seepage water was discussed and analyzed further to understand the status of 3D LSMT in tunnel monitoring and provide a reference for tunnel distress monitoring.

Prestressed concrete continuous beam bridges often experience increasing deflection during operation, affecting service performance. However, the evaluation method of continuous beam bridges with an excessive deflection in urban rail transit still needs to be improved. This paper carried out a structural and operational safety evaluation of a long-span continuous beam bridge with an excessive deflection in urban rail transit. Long-term deformation monitoring, static load tests, and natural frequency tests were conducted to evaluate the structural property development and response under the train loading. Based on the field data, a train–track–bridge coupled numerical model was established and calibrated to analyze the dynamic deflection, acceleration of the bridge, train safety, and comfort indexes. Subsequently, the deflection limits and maintenance schedule were discussed. The results show that the bridge exhibited a deformation curve with a large midspan deflection and a slight side-span camber. The cumulative static deflection of the midspan was 50.4 mm since the beginning of long-term deformation monitoring. The increasing deflection led to the gradual reduction of elasticity recovery capacity (ERC), but ERC remained at a high level and there was no significant attenuation of the structural stiffness. The evaluation methods proposed in this paper can provide useful references for the management of similar long-span continuous beam bridges in urban rail transit.

Abstract

Failures of drinking water systems in Flint, Michigan, and Jackson, Mississippi, were similar, other than their contextual situations. Each episode spurred media accounts and policy actions, but these may not address long-term systemic issues. Application of the Institutional Analysis and Development (IAD) framework can provide a repeatable approach to study such problems, and depending on its scope of application, can provide insights to patterns of interaction in critical action arenas where solutions must begin. The IAD framework evolved from work by policy scientists on a range of complex problems, and its use to analyze issues in Flint and Jackson explored its potential for addition to the tools of Integrated Water Resources Management. IAD can incorporate information from other methods and sources to enrich its knowledge base. For example, media attention highlights problems, and the case studies that follow can identify issues, action arenas, and players. Tools like systems analysis can be used to study the patterns of interaction in the action arenas and the feedback loops between them. Flint and Jackson require multiple solution approaches like these to address systemic issues. They should involve better utility management supported by political leadership and effective governance, as well as attention to equity issues involving human rights and responsibilities to pay for services. In shedding light on root causes of failures, IAD can help point the way to improving services despite formidable obstacles.

Practical Applications

The use of the IAD framework to analyze complex sociotechnical problems like systemic and repetitive failures in urban water systems can help managers explain and policymakers understand the need for long-term and sustainable solutions to replace hasty fixes. IAD provides a systematic but comprehensive method to study diverse action arenas whose connections would be too complex for systems analysis or single case studies. The method requires teams to implement, and it should be used over a time period that allows practitioners to study the dynamics and interconnections among action arenas. Use of the method by engineers and managers will require additional research to hone the procedures, and that work will help to illuminate unique attributes of the complex problems inherent in urban water services.

External prestressing technology has been widely applied to mitigate the cracking and deflection of variable cross-section continuous box-girder bridges. However, it remains a challenging task to establish a reliable safety monitoring and evaluation method in engineering applications. This paper takes a practical project as the research background and installs a sensing monitoring system on a bridge before strengthening. The evolutions of the strain at the characteristic sections, crack width, and deflection of bridges before and after strengthening were compared and analyzed. The construction process’s safety and strengthening measures’ effectiveness were monitored and evaluated. According to the construction process monitoring, the prestress tensioning process did not bring torsion to the bridge, and the strain at each monitoring point was within safe boundaries. After strengthening, the bridge appeared to camber with a value of $3–6\mathrm{mm}$. The typical cracks were mitigated to different extents, and the closure degree of the crack width was $(2.5–4)\times {10}^{-2}\mathrm{mm}$. The strain distribution of the bridge was more stable after strengthening, and the frequency of large strain was significantly reduced, which reflected the improvement of section stiffness. The study can provide meaningful references for the optimization design and strengthening strategies of similar projects.

Sudden failure of reinforced concrete (RC) or prestressed concrete (PC) Gerber saddles of bridges and viaducts has occurred all around in the word in the last few years due to corrosion of steel bars. The danger of sudden and brittle failure is often due to general and pitting corrosion of steel bars, concrete crushing, and loss of bond in steel bars. In this paper, the flexural response of reinforced concrete Gerber supports under their self-weight with or without service loads was investigated through determination of the load-deflection response of beams, with the focus on the consequences of pitting corrosion and loss of bond in steel bars. A simplified strut-and-tie model was developed to predict the flexural response of Gerber supports in terms of load-deflection curves, deduced analytically in a closed form. The model includes the effects of corrosion of steel bars, loss of bond, and concrete crushing due to the biaxial state of stresses. Several experimental laboratory studies regarding the flexural behavior of RC beams with Gerber supports were collected to validate the proposed model. In addition, numerical analyses were performed through a nonlinear finite-element code for comparison with the experimental and analytical results.

Fatigue failure of cantilevered highway sign structures has been recognized in many states due to sustained wind-loading events. AASHTO specifies that the structural component should be designed for infinite life by maintaining the wind-induced stress below their constant amplitude fatigue threshold (CAFT). However, for the existing structures that are typically not designed for fatigue, it is essential to evaluate the condition of all the critical and fatigue-prone components for safety considerations. The visual inspection consumes a lot of time and effort and may not detect unnoticed fatigue cracks. A need for analytical inspection tools to examine all the critical members and connections in terms of remaining fatigue life has received growing attention to ensure public safety. This paper introduces a simplified analytical inspection tool implemented into computer software to assess all the critical components according to AASHTO specifications for fatigue. A failed structure has been examined using this software, and the results showed a fatigue damage crack in the vertical weld of the mast-to-arm box connection at the upper chord level, reflecting the in-situ condition of the structure.

Vapor cloud explosions (VCEs) continually generate an extreme blast load and cause heavy casualties, property loss, and environmental pollution. It is therefore essential to evaluate and control the consequence of vapor cloud explosions. So far, the widely used models in vapor cloud explosions include the Trinitrotoluene (TNT) equivalency method (TNT EM), the Netherlands Organization for Applied Scientific Research (TNO) multienergy method (TNO MEM), the Baker-Strehlow-Tang (BST) method, and FLACS. In this paper, a review and comparative analysis of vapor cloud explosion models were carried out. Combined with a realistic petrochemical plant with different obstacle blockage ratio, the side-on overpressure and duration were evaluated and analyzed with different vapor cloud explosion models. Based on the predicted blast load, the structural response of RC columns, including nonseismic columns and seismic columns with different cross sections, were studied through computer simulation. Vapor cloud explosion models were compared with each other from the perspective of the structural response. It was found that the selection of vapor cloud explosion models has a great influence on the dynamic response of RC columns; the TNO multienergy method was the most conservative method in all vapor cloud explosion models, but its failure mode was quite different from FLACS in the scenario with a high blocking ratio. The predicted results from the Baker-Strehlow-Tang method were closest to that of FLACS. The structural response of the TNT equivalency method was close to that of the TNO multienergy method with the influence of the blast wave shape in Scenario 1. This work points out the applicable characteristics of each load model, which can provide some suggestions for the blast-load evaluation of vapor cloud explosions in the RC column design.

Precast prestressed concrete (PPC) deck girders are among the most common types of structural systems used for bridges with short-to-medium spans. Although this bridge system is known to experience longitudinal (reflective) cracking, there is little information on the impact of transverse cracking on the structural integrity of these bridges. Transverse cracking of PPC girders can significantly compromise the safety and serviceability of these girders. This study focuses on better understanding the impact of transverse cracks on the residual capacity and load rating analysis of in-service PPC deck girder bridges. To obtain a realistic assessment of the condition of in-service cracked girders, a PPC deck girder with transverse cracks is extracted from a bridge in the field and tested under four-point bending until failure. Finite element analysis is also performed to investigate the capacity of the as-built PPC girder. Finally, decompression stresses in the prestressing steel are predicted from the measured crack width using different crack width models that are recognized in the literature. A transverse crack is found to reduce the load rating capacity of the girder by almost 34% which subsequently reduced the capacity-based load rating factor by 22% under the HS-20 truck load. Although serviceability-based load rating from crack width conservatively provided a negative rating, the flexural testing indicated that the girder could carry over 50% of its nominal and residual capacities while remaining in the elastic range.

Semi-integral abutment bridges are integral abutment bridges with a flexible interface at the abutment to reduce the force transferred to the foundation. Past research has investigated the uplift forces from the drill shafts using finite-element analysis, while insufficient experimental data exist to validate this hypothesis. Therefore, a semi-integral abutment bridge in Ohio supported on drilled shafts was monitored for a long-term to investigate the performance of semi-integral abutment with drilled shafts and abutment walls under environmental conditions. During the construction of the bridge, vibrating wire strain gauges were placed in three drilled shafts, footing, and the abutment wall above. Strain and temperature were collected from the installed sensors. It was found that the seasonal and daily temperature changes significantly affect the changes in the strain in the substructure. The behavior of the abutment wall significantly affects the behavior of the footing and drilled shafts. The behavior of the abutment was irreversible, and the top of the abutment wall and the top of the drilled shaft induced higher strain than the bottom. Cracks were noticed at the front face of the abutment wall, and the extremely cold weather conditions induced tensile strain higher than the allowable strain at the top corner of the front face of the abutment wall. In addition, a three-dimensional finite-element model was created and calibrated with the field data. The FEM results were used to investigate the maximum stress magnitudes and locations under temperature variation.

This paper introduces an innovative technology based on an actual corrugated steel arch bridge project. The design of steel-concrete composite structure in which concrete arches are poured around the corrugated steel plate arch ring is proposed to improve its mechanical performance. Field tests and numerical simulations were conducted. In the field test, the load was applied to the structure by loading a heavy truck, and the strain and displacement of different positions of the corrugated steel arch ring section were tested. Two models of corrugated steel arch bridges with and without concrete arch protections were established through finite-element software to study the effect of concrete arch protections on the mechanical properties of corrugated steel arch bridges and verify the test results. The model calculation results showed that when a concrete arch protection was applied, the stress and displacement of each position of the corrugated steel plate arch ring were reduced to varying degrees. The calculated values of the numerical model were also compared with the measured values of the field trials, and it was found that the calculated value is generally slightly higher than the measured value. This study showed that the mechanical performance of corrugated steel arch bridges could be effectively improved by applying concrete arch protection on the corrugated steel arch ring.

A comprehensive experimental investigation was conducted on blast-resistant window anchors involving 46 tests of double-pane insulated glass units (IGUs) anchored to structural steel, reinforced concrete, concrete block masonry, and stone masonry substrates. The tests were conducted using a shock tube. The windows were glazed with security films of different thickness. Different number and spacing of steel anchors were used to secure the window frames to substrates. Each window was subjected to two levels of blast loads, consisting of 28 kPa, 207 kPa-ms, and 69 kPa, 621 kPa-ms reflected pressure–impulse combinations. The windows were instrumented to measure anchor forces. The anchors developed out-of-plane shear forces and in-plane axial tension associated with postbreak membrane action. The results indicate that anchor shear forces show variations with window stiffness, substrate type, and anchor arrangements, often developing lower forces than those computed based on the static application of blast loads, indicating significant inertia resistance. Rigid substrates produce higher anchor forces. In addition to the experimental results, the paper presents single-degree-of-freedom analysis results for anchor force computation, indicating good correlations with experimental data.

A combined experimental and analytical investigation was conducted at the University of Ottawa to assess the performance of blast-resistant window retention anchors to generate design information. The experimental phase of research involved 46 full-scale window tests with different parameters. The analytical investigation included numerical modeling and dynamic analysis of windows to expand the experimental results and to assess the significance of design parameters. Computer software LS-DYNA was selected for the analyses. Analytical models of selected test windows with aspect ratios of 1.0 and 3.0 anchored on structural steel, reinforced concrete, concrete block masonry, and stone masonry substrates were modeled. The models were validated against experimental data. Additional windows with aspect ratios of 1.5 and 2.0 were also modeled for investigation. The models were used to conduct a parametric investigation with the parameters consisting of substrate flexibility, anchor fixity conditions, window size and aspect ratio, frame rigidity, number and spacing of anchors, and the threat level as defined by reflected pressure-impulse combinations. The significance of each parameter is illustrated with emphasis placed on the magnitude of anchor shear and tension design forces. The distribution of anchor forces is obtained numerically. Anchor forces and distributions are compared with those observed experimentally. Design force distribution along the perimeter of window frames is recommended for use in design. The paper provides the results of numerical simulations illustrating the significance of design parameters on anchor design force levels and their distributions.

Eight low-profile arch corrugated metal culverts were recently annexed by the city of Anniston, Alabama. These structures are nearly 80 years old and have never been load rated. To satisfy federal requirements, load rating of the culverts was required. Attempts to rate these structures using methods developed by the corrugated steel pipe industry implied that the culverts require posting due to low soil cover, without any consideration for structural integrity. Guidance for load rating of steel and concrete bridges and cast-in-place concrete culverts is well established, while the guidance for corrugated metal culvert structures is limited. The objective of this study was to examine the contemporary practice of load rating corrugated metal culverts with shallow cover and use diagnostic load testing to demonstrate the capacity and overcome the shortfall of the current rating methods. To verify the load-carrying capacity of these structures and improve the load rating, diagnostic load tests were therefore carried out to assess the load response of two of the culverts using a $381.3\text{-}\mathrm{kN}$ ($85.7\text{-}\mathrm{kip}$) test truck. The load testing program featured a very simple instrumentation package that was easy to install, recover, and reuse. The instrumentation plan consisted of displacement transducers and electrical resistance strain gauges. Load, displacement, and strain data collected in the field load tests were analyzed, which showed satisfactory performance with a maximum deflection of less than 0.1% of the span length and a maximum strain that corresponds to approximately 24% of the estimated yield stress. Following standard procedures, the test response data were used to improve the analytically derived rating factors, and challenges associated with the approach are discussed.

The destructive failure of Shanghai Metro line 4 across underneath the Huangpu River on July 1, 2003, led to massive ground subsidence and collapse of pre-existing structures in the proximity; additionally, the failure generated large amounts of human-made rigid obstructions in the strata, which made rehabilitation of the collapsed metro line be very technically challenging. By extensive comparisons in terms of technical difficulties, economic costs, and construction durations, a plan of reconstruction of the collapsed metro line at its original location rather than relocation was selected finally for the postfailure rehabilitation. The majority of the failed metro line was replaced by a $262\text{-}\mathrm{m}\text{-}\mathrm{long}\times 23.7\text{-}\mathrm{m}\text{-}\mathrm{wide}\times 38.5–41.2\text{-}\mathrm{m}$-deep cut-and-cover tunnel bottoming out in the confined aquifer, whose two ends were connected with the existing intact metro line via two 10-m-long tunnels mined within the aquifer by the ground-freezing method. Excavation of the cut-and-cover tunnel was retained by 1.2-m-thick and 65-m-high perimeter diaphragm wall panels braced by 9–10 levels of steel-reinforced concrete struts. To ensure the project safety and mitigate potential adverse influences of field works on the urban environments, extensive innovative construction plans, measures, and techniques were designed and then implemented into the reconstruction, e.g., a lightweight cofferdam and pile-supported steel platform for diaphragm walling through the existing metro line underneath the river; unique protective solutions and construction techniques for execution of vertical and horizontal ground-freezing programs for diaphragm walling and mining; special procedures of cleaning up the existing tunnels previously filled with water, sand, and cement; innovative joints and grouting measures adopted between the reconstructed tunnel and the pre-existing intact metro line, and so on. Furthermore, the initial designs were optimized and adjusted with the progress of field construction works. Lastly, the long-term field performance data demonstrated the success of this rehabilitation project, which affected the urban environments rarely. The construction plans, measures, and techniques outlined in this paper are practical, useful references for professionals worldwide to deal with similar underground projects in the future.

Concrete-filled steel tubular (CFST) piers have been applied in bridge structures due to their high bearing capacity, good ductility, and light weight. During their service life, CFST piers may suffer vehicle collision. Nevertheless, there is still a lack of a performance evaluation method for CFST piers subjected to vehicle impact. Therefore, this paper presents a residual deformation-based method to evaluate the performance of CFST piers under truck impact. Before that, a numerical model was developed to simulate responses of CFST piers under truck collision and validated by reported impact tests. Then, the performance levels of 6- and 12-m high CFST piers under 20 and 40 ton and 60, 100, and $140\mathrm{km}/\mathrm{h}$ truck collisions were numerically investigated. Afterwards, a residual deformation-based performance evaluation method was proposed based on the numerical investigations. In this method, the ratio of the residual lateral deflection at the mid-height to half of the pier height was first selected as the evaluation index. Then, threshold values of the evaluation index at different performance levels were determined. Finally, an analytical model for the evaluation index was developed. Comparisons indicate that the analytical performance levels are in good agreement with the numerical results. The proposed residual deformation-based performance evaluation method can be used for design and accident analysis of CFST piers subjected to truck collision.

Progressive collapse alternate path scenarios are often characterized by restrained beam configurations that provide resistance to structural collapse after column removal. While various methods have been presented to model the behavior of restrained beams, opportunities exist for mechanics-based estimation of the complete static and dynamic load-deflection curves. This paper presents an axially restrained beam (ARB) model that incorporates axial–flexural interaction throughout the entire static load-deflection curve including the elastic material range, the plastic flexural dominant range, the range beyond plastic flexure with increasing catenary effect, and the full catenary range. Energy methods are applied to static load-deflection curves to determine dynamic load-deflection relationships. A parametric study was conducted to assess the accuracy of the ARB method compared to nonlinear, dynamic time history finite-element (FE) analyses. The model compares favorably to results of FE models with average estimates of dynamic deflection within 2.1% for ideal moment connections and 7.7% for configurations combining simple and moment resisting connections.

The vertical temperature gradient of steel box girders in cold regions is not stipulated in the relevant specifications of China. Therefore, a systematic and comprehensive study was necessary. The vertical temperature distribution characteristics of the web were analyzed on the basis of steel box girder temperature monitoring data for 1 year in a cold region to obtain a vertical temperature gradient model corresponding to the actual situations of cold regions, which was compared with the specification. The temperature field numerical model was verified using the measured data. The parameter sensitivity of the vertical temperature gradient was analyzed. Results show that the daily variation of the web temperature of a steel box girder in cold regions is similar to a sinusoidal curve. The temperature fluctuation range in summer is larger than that in winter. Moreover, the positive and negative temperature differences occur in summer and winter, respectively. The vertical positive and negative temperature gradients are in the forms of an exponential function and a broken line, respectively. The fitted vertical temperature gradient in this paper was basically greater than the specification. The span of boundary conditions of the numerical model was reasonable. The influence of parameters on the vertical temperature gradient ranks ranked as follows: bridge deck pavement thickness > radiation absorption rate > wind speed > coefficient of heat conductivity > specific heat capacity.

Even with the continuous development of coating technologies, coating systems are susceptible to corrosion-induced premature failures and unable to meet the anticipated service life. Coating premature failures will negatively impact the safety, integrity, and longevity of steel bridge structural elements. The advancement of the data analytics approach (e.g., machine learning) offers an opportunity to leverage the wealth of historical bridge inspection and maintenance data collected by Departments of Transportation to evaluate coating conditions of steel bridges effectively and efficiently. This paper focuses on presenting a data-driven study that analyzes the conditions of coating systems of steel bridges in the state of Florida. Three machine learning algorithms were used in developing models that can be used to analyze steel bridge coating conditions based on data collected from the Bridge Management System of the Florida Department of Transportation. The result showed that the machine learning–based models were able to effectively predict steel bridge coating conditions. The $k$-nearest neighbor (KNN) regression algorithm offered the best performance. Although the approach was currently applied to the steel bridges of Florida, it can be easily replicable for similar data sets from other states. The research contributes to the body of knowledge by offering a data-driven understanding of coating performance of steel bridge elements. The research has the potential to offer a valuable decision-making tool for transportation agencies to effectively and easily analyze or predict steel bridge coating conditions.

The serviceability limit of the foundation system plays an important role in the safe long-term performance of a building. Under governing load cases in service life, the building foundation system should satisfy the serviceability limit state, i.e., total and differential settlement criteria. This study investigated the distress of a building through foundation performance assessment incorporating the soil–foundation–structure interaction (SFSI) effects. A spatially variable soil model [zonewise, obtained from field observation and electrical resistivity tomography (ERT) study] was used to obtain the settlement of the foundation system. Engineering properties of the subsurface were estimated from the collected soil samples and field tests. ERT result shows the variability of the subsurface layer. A three-dimensional finite-element model of soil, foundations, and structures was developed to estimate the settlement demand of the foundation and structures. The numerical model includes the geometric variability of all the foundations of the building and subsurface variability. Settlement and bearing capacity demand of the foundations were estimated and compared with the standard provisions. Results obtained show that the building foundation system satisfies the serviceability limit of the foundation system under total settlement criteria. However, the differential settlement of the system exceeds the required limit despite considering the SFSI effects, and is one of the major causes of distress to the building. The main contributions of this study also include establishing the spatial variability of the soil layer through ERT and correlating it with the crack zone in the building.

For through tied-arch bridges, the corrosion and degradation of the cable’s load-bearing capacity are the main external causes of cable breakage and subsequent structural failure; nevertheless, the progressive collapse after cable breakage is primarily attributed to the weak structural robustness, which makes a huge potential risk of bridge operation and maintenance (O&M). Whereas, as the basis of O&M, current condition evaluation method has not yet taken into consideration the influence of different consequences of cable breakage, resulting in unscientific conclusions for O&M decisions frequently. In this study, a robustness-based condition evaluation framework for the overall structure of the through tied-arch bridge is presented, consisting of three stages: (1) structural robustness assessment associated with tie-bar and suspender failure respectively; (2) classification of evaluation process by the results of robustness assessment, within which the overall structure is either evaluated using the code method or evaluated directly as unqualified (Condition I and II), or the structural member weightings are adjusted according to the robustness weightings (Condition III); and (3) condition evaluation of entire bridge. The evaluation processes of three conditions are further presented in accordance with the tied-arch structure and suspended deck system. To establish the robustness weightings in Condition III, the safety redundancy indexes of through tied-arch structures as well as the suspended deck system are calculated separately, combined with robustness assessment result. Applying the proposed framework to evaluating the condition of a through tied-arch bridge with different structures, the analysis and comparison indicates that, due to the robustness of the through tied-arch structure and suspended deck system, the variation in the potential risk of accidents induced by cable failure is shown intuitively through the evaluation results, which better meets the needs of guiding bridge O&M decisions consequently.