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.

In 2017, Hurricane Harvey, highlighted the vulnerability of floating roof storage tanks to severe rainfall events. Several floating roofs failed due to rainwater accumulating on them, causing the release of hundreds of tons of pollutants in the atmosphere. Despite the vulnerability of floating roofs, tools currently are lacking to evaluate their anticipated performance during rainstorms. This paper presents the development and application of fragility models to assess the vulnerability of floating roofs subjected to rainwater loads and help prevent future failures. First, a finite-element model of floating roofs and a load-updating method are presented to assess the potential for failure. By coupling the finite-element model with a statistical sampling method, fragility models were derived for two damage mechanisms: sinking of the roof, and excessive stresses due to the rainwater weight. Fragility models were developed for undamaged roofs and roofs with pre-existing damage (i.e., punctured pontoons). To allow their use for future or historic rainfall events, a framework is presented to estimate the maximum amount of rainwater standing on a roof and the probability of failure during a rainstorm. Lastly, forensic investigations of a floating roof failure that occurred during Hurricane Harvey were performed to illustrate the viability of the fragility models to understand the conditions leading to failures and to propose mitigation measures. Insights from the fragility analysis indicate that small floating roofs are more vulnerable to rainwater loads than are large roofs, whereas insights from the failure investigation reveal the importance of efficient roof drainage, as well as terrain drainage to prevent water accumulation around the storage tank, which can lead to inefficient roof drains. Results also indicate that in preparation for a rainstorm, storage tanks should be filled with product to improve floating roof drainage.

Coastal residential buildings have suffered significant damage during recent hurricanes, which illustrates the poor performance of coastal structures. This paper reviews the performance of coastal residential buildings with respect to direct and indirect damage, and subsequent mitigation techniques are discussed according to hurricane wind and flood-related hazards. The results show that building systems other than conventional wood frames have better performance during strong hurricanes. Regardless of building materials and systems, envelope systems and roofs are more susceptible to wind-induced damage compared to structural components. Therefore, selecting adequate connection systems, suitable wind-resistant materials, and appropriate installation methods for wall/roof coverings can significantly reduce the level of wind-induced damage. Regarding flood-related hazards, surge and subsequent wave heights cause inevitable damage to nonelevated or low elevated buildings once a flood reaches the first-floor level. Furthermore, many elevated buildings surviving a flood can still be vulnerable to wind-induced damage, particularly envelope systems due to the fact that the house would be exposed to higher wind pressures. As a result, selecting the appropriate foundation system and using flood-resistant materials below the base flood elevation can reduce flood-induced damage to residential buildings in coastal regions.

When urban subway lines pass under buildings, it is often necessary to carry out corresponding pile foundation detection work to ensure construction safety. However, detecting the distribution of piles with conventional surface geophysical techniques is not an easy task because of space constraints. The cross-hole resistivity computed tomography (CT) method only needs two drill holes to implement the detection, which can overcome the difficulty in arranging the survey line above the pile foundation. Moreover, this method is suitable for low-resistance body detection, with the advantages of high detection accuracy and less influence from ground interference. In this paper, six types of geoelectric models are constructed for numerical simulation analysis due to two major factors that affect the detection effect of cross-hole resistivity CT: model parameters and measurement parameters. The results show that cross-hole resistivity CT provides an accurate imaging of the shape and distribution of the pile foundation between the holes. Furthermore, the technique provides a good detection of the bottom interface of the pile. The detection effect is best when the electrode spacing is 1 m, the pile is located in the detection center domain, the borehole spacing control is not more than 20 m, and the pile drill hole spacing is not less than 5 m. The research results have effectively guided practical engineering applications and obtained good detection results. The theory and practice show that the cross-hole resistivity CT is a more feasible method for detecting pile foundations on subway lines.

The focus of this research is the resistance deterioration behavior of existing concrete bridge components under the influences of environmental, material, and loading factors. To derive a more accurate resistance mathematical deterioration model of existing concrete bridge components, the Gamma process is firstly introduced to establish the original mathematical model by mathematical derivation according to the deterioration properties of concrete components. The updating procedure of the original mathematical model is then provided by incorporating the actual deterioration conditions, in which the key point is the determination of deterioration conditions at a specific moment. Based on the physical data measured from field inspection, a fuzzy evaluation method of the deterioration coefficient is developed by combining a nondeterministic analytic hierarchy process (AHP) and real-coded–based genetic algorithm (RGA). The accuracy of the developed fuzzy evaluation method is validated through loading tests of experimental beams. The results show that the developed fuzzy evaluation method is accurate and the calculated deterioration coefficients can be used in the updating of the original mathematical model. In the former, an existing concrete bridge is taken as the prototype bridge to conduct a case study. It is found that the proposed framework can be successfully used in the establishment and updating of resistance deterioration model of existing concrete bridge component. The updated mathematical model is more accurate than the original mathematical model in the description of the resistance deterioration process considering the incorporation of the actual deterioration conditions in recent years.

To accurately predict the flexural capacity of postfire RC beams is imperative for fire safety design. In this paper, the residual flexural capacity of postfire RC beams is predicted based on a back-propagation (BP) neural network (NN) optimized by a genetic algorithm (GA). First, the temperature distribution of the beams was determined using the finite-element analysis software ABAQUS version 6.14-4, and the strength reduction factor of materials was determined. The flexural capacity of the RC beams after fire was calculated by the flexural strength reduction calculation model. The model was used to generate the training data for the NN. To enable machine learning, 480 data sets were produced, of which 360 were used to train the network; the remaining 120 were used to test the network. The predictive models were constructed using BPNN and GA-BPNN. The prediction accuracy was evaluated by comparing the predicted and target values. The comparison showed that the GA-BPNN has a faster convergence speed and higher stability and can reach the goal more times, reducing the possibility of BPNN falling into the local optimum and achieving the global optimum. The proposed GA-BPNN model for predicting the flexural capacity of postfire RC beams provides a new approach for design practice.

Dynamic response of shallow buried tunnel with three different cross sections subjected to surface blast loading using LS-DYNA version R10.1.0 is investigated. Multimaterial arbitrary Lagrangian Eulerian (MM-ALE) is employed for this study. Strain softening of concrete is incorporated in terms of tensile cracking. Whereas, strain rate dependent behavior of reinforcement is defined using visco-plastic formulation. The main objective is to investigate the nonlinear behavior of reinforced concrete that constitutes the tunnel lining under a surface blast. Extensive parametric analysis has been performed to determine the effects of change in explosive charge weight, lining thickness, and cover depth on the behavior of tunnel under blast loading. Further, a comparative study based on the degree of blast resistance has been carried out considering three tunnel cross sections, namely, horseshoe, box, and circular. Finally, the blast damage assessment of tunnel with varying geometry, explosive charge weight, and cover depth has been investigated to arrive at the most vulnerable blast scenario.

Based on advanced numerical simulation technology, a complex finite-element model of a fragment and slab is constructed using software LS-DYNA version 971. A series of numerical simulation analyses are conducted on this model to estimate the basic characteristics of high-speed fragments on the perforation of the reinforced concrete slab. First, the process by which the fragments penetrate the slab is analyzed in detail. Subsequently, the effects of a few parameters, such as floor load, compressive strength of concrete, and fragment shape, on the penetration depth of the fragment are further investigated. Moreover, the relation between the residual and striking velocities of the fragment is improved considering the fragment shape. Finally, the basic steps to predict the residual kinetic energy of the fragment are presented. Results show that penetration depth and residual velocity are significantly affected by fragment end shape, and increase significantly with fragment end shape coefficient. The analysis is rigorous and comprehensive, and the results are true and reliable; furthermore, it indicates that the proposed method can accurately and effectively predict the residual kinetic energy.

ASTM A1010 (A709 Gr50CR) is a dual-phase stainless steel that is gaining popularity in the US bridge market due to its corrosion resistance and potential for life cycle cost savings. Several recent research studies and pilot bridge construction projects have been initiated across several different states and agencies. Recent research has primarily focused on corrosion resistance and galvanic corrosion when in contact with dissimilar metals commonly used in the steel bridge industry. Ongoing research is investigating the structural behavior of connections such as pretensioned bolted joints and welds. Six bridges have been constructed in the US using A1010 material in five different states. Several other agencies are considering or have initiated discussions on the use of this new material to reduce maintenance costs, particularly in highly corrosive environments where other common bridge materials and coating systems require costly corrosion-protection maintenance.

Hydraulic failure, which encompasses scour, flooding, and overtopping, accounts for most bridge failures in the United States. The research reported herein aimed to evaluate the current practice of bridge hydraulic vulnerability assessment, and to identify characteristics of bridges most prone to hydraulic failure using a historical bridge failure database. Using an inductive, data-driven approach, a bridge failure population was created by synthesizing the National Bridge Inventory (NBI), United States Geological Survey (USGS) station streamflow, and available bridge failure data. Many failures that occurred before mid-2000 had incomplete assessments; this reflected the low share of structures with completed assessments in NBI. In subsequent years, state bridge inventories had completed assessments and hydraulic failures had significantly lower scour critical ratings, which indicated an improvement in identifying structures most vulnerable to failure. The most common bridge types within the overall inventory were generally overrepresented within the bridge failure population (especially those used before the Interstate Era). Differences in structure age, geometry, and condition ratings were most noticeable between failures and the overall waterway bridge inventory. Bridge deck width was narrower for failures and might explain a mechanistic cause of hydraulic failure. Waterway bridges built prior to the Interstate Era resemble those that have historically failed in that era. However, failures of bridges constructed within the Interstate Era did not resemble current waterway structures built in the same time period.

This research investigates the potential for ultrasonic stress measurement (USM) to be used to evaluate the total stress in wide-flange steel sections (W-section) for a postevent condition assessment of buildings. The research utilizes acoustic birefringence measurements that are proportional to stress in the material to assess stress based on the velocities of orthogonally polarized shear waves. The nondestructive measurement of stress in the material provides a means to determine the force carried in the member and a potential solution to limitations of structural evaluations based on theoretical modeling and design assumptions. The objectives of this research were to evaluate the acoustoelastic properties for a common structural steel material, assess the accuracy of the stress measurement under axial compression, and assess the in situ birefringence and residual stress distribution in a W-section. The research found a variation of the in situ birefringence at different locations on a typical W-section as a result of residual stress distribution and texture of the material. Axial compression tests showed there were differences in the acoustic constants that relate stress to the birefringence measurement for materials from different sources and at different locations within a single wide-flange section. The birefringence profiles showed a linear variation with a compressive load and could be used to determine the stress in a steel member. The research found birefringence USM could be used to determine stress accurately to approximately ±46 MPa ($\pm 6.7\mathrm{ksi}$) or 12% $f_y$ for a scenario in which generalized acoustic constants were used and about ±7 MPa ($\pm 1\mathrm{ksi}$) or 2% $f_y$ for a scenario in which location-specific constants were used in calculating the stress present in the member.

Under long-term service, shield tunnel linings are prone to diseases such as bolt corrosion, reinforcement corrosion, and cracks; therefore reliability analysis of tunnel linings is significant for overall tunnel stability. This study aimed at developing a reliability analysis method for the bearing capacity of shield tunnel linings in service. Six failure modes of tunnel linings, related to the concrete structure, reinforcement structure, concrete joints, and joint bolts (inner-row bolts and outer-row bolts), are highlighted, and the performance functions of tunnel linings are established according to the failure modes. In this study, the joint structure was treated as a continuous heterogeneous beam in order to simplify the calculation of bolt tension and concrete stress of joints connected with double-row bolts by satisfying the equilibrium of internal force and coordination of deformation. In addition, a field inspection method for lining structure deterioration parameters and a method for calculating the mechanical parameters of deteriorated concrete and reinforcement are elaborated. Because shield tunnel linings suffer from eccentric loads, a Monte Carlo sampling method was used to calculate the probability of a full and partial section compressed condition. The first order reliability method (FORM) (JC method) program was compiled by MATLAB version R2018b to calculate the reliability index of tunnel lining structures; furthermore, sensitivity analysis of random variables was included. The proposed method was verified using inspection data from the Shanghai Dapulu Tunnel. The results showed that the minimum comprehensive reliability index was 2.46 (section 90°) and the maximum comprehensive reliability index was 8.33 (section 40°). The reliability of joint sections was more sensitive to $f_c$, $k_0$, $A_{b2}$, $\gamma$, whereas structure sections were more sensitive to $k_0$, $f_y$, $f_c$, $A_s$, $A_s^{\prime }$, $\gamma$.

In Brazil’s public university sector, there is a lack of information regarding the building inspection activity; besides, there is a normative gap in this area. This paper’s objective was to develop and validate an inspection management method focused on the management of building maintenance in universities. Design science research was adopted to develop the artifact called the inspection method for maintenance management, which was evaluated in a university in Brazil. This method consists of scope, planning, inspection, verification, prioritization, and recommendation steps. It was found that the application of the inspection method in the case study provided a maintenance inspection guided by scope and prioritization. However, it is necessary to align design information, especially for new buildings, with the maintenance strategies to meet the required performance criteria. The inspection method for maintenance management could be experimented in other commercial buildings, as long as the design needs were adjusted.

This paper aims to summarize central findings from a literature review and technical survey on unmanned aerial vehicle (UAV) techniques for bridge inspection and damage quantification. This literature review includes a detailed compilation of different algorithms on high-quality image selection, image-based damage detection and quantification, and various UAV applications for bridge inspections. To gather current bridge inspection practices in the United States, a technical survey referring to UAV-enabled bridge inspections was also conducted for state DOTs and USDA Forest Service (USDA FS) regions. Responses to the survey were assembled from 17 state DOTs (e.g., Nevada DOT, South Dakota DOT, and Texas DOT) and two USDA FS regions such as Region 8 (Southern). From both the review and survey, it was revealed that researchers, state DOTs, and USDA FS regions have interest in using a UAV for bridge inspections, but they have struggled to use it for bridge damage quantification. Specifically, it was found from the review that some recent studies using different algorithms such as deep learning and pattern recognition have been carried out to quantify different types of damage. Key findings from the survey are that over 56% of respondents have used or are planning to use UAVs for bridge inspections, but only 19% of respondents have begun to quantify damage using images captured from UAVs.

In large infrastructures, the nonintrusive evaluation of structural fitness at the local scale can be time-consuming using the conventional P-wave-based ultrasonic tests. Adopting a multisensor approach to examine the surface waves propagating in a structure, on the other hand, can provide a section-by-section assessment while reducing the inspection time. Once such a configuration is established, the phase velocities of surface waves can be measured to extract diagnostic features indicating the deterioration. Hereby, the concrete roof of an anaerobic digester tank is inspected by conducting surface wave tests at 10 different sections. The recorded signals via multiple sensors are processed to extract a new diagnostic feature named the dispersion index (DI), which represents the cumulative dispersion in the phase velocity with respect to the reference dispersion curve obtained from a numerical model. The index DI is then used to categorize the tested regions into three classes of condition named: good, moderate, and deteriorated. It is found that the assessment based on the DI is in good agreement with the visual inspection for 80% of the tested sections. In addition, the crack depth is estimated using the measured cutoff frequency in the dispersion curve; the results confirm the deepest cracks located in those regions characterized as the most deteriorated by the proposed DI index.

This paper presents experimental and numerical research carried out on low-rise reinforced concrete (RC) frames that have weaker beam-column joints, which are retrofitted with steel haunches to avoid joint shear hinging, allowing beam-column members to deform inelastically and dissipate energy under seismic excitation. Shake table tests were conducted on four $1:3$ reduced scale two-story reinforced concrete frames, having construction deficiencies that are common in developing countries, which were retrofitted with steel haunches to understand their seismic behavior and retrieve the seismic response parameters. A representative numerical model was prepared in finite-element (FE)-based software SeismoStruct, calibrated against the experiments in simulating the structures’ roof displacement time history response and predicting the peak roof displacement and peak base shear force, which showed promising performance. Further, FE based models were subjected to a suite of spectrum compatible natural accelerograms, which were linearly scaled to multiple intensity levels, to perform an incremental dynamic analysis. The structure capacity curve (base shear versus roof displacement) and response curve (seismic intensity versus roof displacement) were retrieved, which were analyzed to calculate the structure-overstrength-based and ductility-based response modification factors. The derived response modification factor can be employed in a force-based design and assessment of haunch-retrofitted reinforced-concrete frame structures. An example case study is presented for the performance assessment of as-built and retrofitted reinforced concrete frames in various seismic zones.

The stability discrimination method of surrounding rock in vertical shaft construction and the safety technology of shaft construction under the geological condition of a super-thick crush belt were studied. Through the establishment of a shaft surrounding rock mechanical model, quantitative analysis was conducted on the displacement of broken surrounding rock during shaft construction under the coupling action of ground pressure and super-thick crush belt strata. A method for the stability determination of surrounding rock in shaft construction was put forward. Combined with the adjustment of supporting materials and construction technology for shaft construction, the methods of effective control of the displacement velocity of surrounding rock and cyclic time control of shaft construction technology were put forward. Through the construction time per unit cycle and time control required for the maximum allowable displacement of shaft surrounding rock, the safety technology method of vertical shaft construction through super-thick crush belt penetration in the thousand-meter scale large fault was obtained. Through technological innovation, this provided a scheme for the safe and efficient construction of a vertical shaft under special geological conditions. It laid a solid foundation for the achievement of zero accidents in vertical shaft construction.

A large number of cracks were observed in a bridge seal structure during an underwater inspection. The seal is $13.2\mathrm{m}$ long, $5.9\mathrm{m}$ wide, and $6.8\mathrm{m}$ deep and thus is considered mass concrete. The concrete mixture contains a 45% cement replacement with Class F fly ash. The seal is evaluated to identify the causes of cracking. The heat of hydration (HoH) and temperature rise are experimentally evaluated. Subsequently, a finite-element analysis model is developed using input from the experimental study. The modeling approach is validated with results from sizeable specimens. A coupled thermal-structural analysis is performed to evaluate the temperature-time history and extent of cracking. The results indicate internal temperature in the seal slightly exceeds the allowable temperature of 70°C, which is known for exposing concrete to the risk of delayed ettringite formation. The gradient temperature exceeds the allowable limit of 19.4°C, leading to increased tensile strain. A sensitivity analysis indicates that two mixtures that contain a 70% cement replacement with slag, metakaolin, and/or fly ash are recommended for reducing the internal temperature below 70°C. However, it is concluded that the differential temperature requirement (19.4°C) cannot be met by altering material designs alone. Therefore, active cooling is necessary to control temperature when placing underwater seal structures with a volume-to-surface-area ratio greater than 4.0.

Displacement due to the deformation of civil structures such as bridges and buildings (caused by different external loads: e.g., vehicle, wind, and temperature) is an important factor for structure safety evaluation. The effectiveness of structure maintenance is highly dependent on the accuracy and reliability of the structural displacement measurement. An accelerometer is a tool that indirectly measures displacement and has gained widespread interest. However, the accuracy is questionable because noise exists in acceleration measurements and also can be undermined by accumulated errors during the double integration of the acceleration process. In this paper, a new displacement measurement algorithm based on data fusion technique was studied. In this algorithm, the Kalman filter was used as the fusion technique. The acceleration was taken as the primary measurement, and rotation measurement was used as the second measurement to minimize the effect of the error in the displacement prediction during the double integration of the acceleration process. To validate the performance and reliability of the algorithm, two lab tests were conducted: cantilever beam test and simply supported beam test. The results show that the proposed algorithm could minimize the effect of the accumulated error on the double integration of acceleration, thus providing a reliable estimation of the vertical displacement of a cantilever beam and simply supported beam.

A deep understanding of the cause-effect relationship of bridge damages provides an opportunity to design, construct, and maintain bridge structures more effectively. The damage factors (i.e., bridge element, damage, and cause) and their complex relationships can be extracted from bridge inspection reports; however, it is not practical to manually read a considerable number of inspection documents and extract such valuable information. Although existing studies attempted to automatically analyze inspection reports, they require a large amount of human effort for data labeling and model development. To overcome the limitations, the authors propose an efficient information acquisition approach that extracts damage factors and causal relationships from bridge inspection reports. The named entity recognition (NER) model was developed based on a recurrent neural network (RNN) and was trained with the active learning method. In the experiments performed with 1,650 sentences (i.e., 1,300 for training and 350 for testing), the developed model successfully classified categories of text words (i.e., damage factors) and captured their causal relationship with 0.927 accuracy and 0.860 F1 score. Besides, the active learning method could significantly reduce the human effort required for data labeling and model development. The developed model achieved 0.778 F1 score only using 140 sentences, requiring less than an hour for manual labeling. These results meant that the model was able to successfully extract major damage factors and their cause-effect relationships from a set of text sentences with little effort. Consequently, the findings of this study can help field engineers to design, construct, and maintain bridge structures.

The aim of this paper is to present the field investigation and performance assessment of the mosques and minarets constructed around the cities of Elaziğ and Malatya and their surrounding districts shortly after the earthquake (magnitude of ${\mathrm{M}}_{\mathrm{W}}=6.5–6.8$ according to different institutions) that occurred at 8:55 p.m. local time on Friday January 24, 2020, in the Sivrice township of Elazığ, located in the southwest of the Eastern Anatolia region of Turkey. Mosques and minarets are special structures affected by earthquakes as other buildings too. Two types of mosques and minarets constructed using masonry and reinforced concrete constructional materials and technologies were investigated. A total of 20 mosques with minarets having either a masonry or reinforced concrete carrier system were extensively examined. It is concluded that a significant part of the collapsed and damaged mosques and minarets did not receive adequate engineering services and/or were constructed without following national guidelines. Also, it is thought that the absence of any codes or guidelines for these special structures is a major deficiency and leaves engineers in a difficult position during the design phase.

Tunnels are critical links within modern transportation networks and are susceptible to accidental explosion from vehicle fuel and cargo. They also present a target for terrorism due to unscreened public access. Roadway tunnels constructed with circular, oval, or horseshoe cross sections in the United States within the last $100\mathrm{years}$ have typically consisted of a road surface, tunnel liner, and drop ceiling. The tunnel liner was the main structural component that resists any over-tunnel loads as well as preventing substrate intrusion and cave-ins. The drop ceiling is hung from the liner and creates a plenum above the roadway for ventilation of vehicle exhaust as well as throughput for electrical conduits, utilities, fire alarms, and fire suppression systems. The typical design of a tunnel drop ceiling only considers gravity loading and forces exerted by pressure within the ventilation plenum—severe impulsive uplift loading from a blast on the roadway below therefore presents significant risk of ceiling panel damage or collapse. This study evaluates the likelihood of significant damage and collapse of tunnel drop ceilings under blast loading. Six scenarios consisting of three trinitrotoluene (TNT) equivalent charge sizes in two representative tunnels were analyzed using computational fluid dynamics (CFD) to generate blast demands on the drop ceiling, followed by a blast vulnerability assessment of the drop ceiling panel elements. Dynamic single-degree-of-freedom (SDOF) analyses were verified against finite-element (FE) solutions and used to evaluate the damage for a wide range of blast demands. The results indicate that modestly sized explosive hazards can induce significant damage to the drop ceiling, ranging from permanent deformation up to widespread collapse. Hardening options include flexural enhancement with fiber-reinforced polymer (FRP) as well as retrofit of the hangers. As an alternative, removing the ceiling and reconfiguring the ventilation system with modern jet fans can be a more cost-effective option for blast mitigation depending on the tunnel owner’s operational and/or financial constraints.

Parallel Seismic (PS) method is a straightforward Nondestructive Testing (NDT) method capable of providing valuable information of unknown bridge foundations made of various common construction materials such as wood, steel, and reinforced concrete. Although numerous investigations on various aspects of the method have been previously carried out, factors affecting the success of PS tests on steel H-piles still need to be investigated in more details. In the current study, PS tests were performed on steel H-piles of a highway bridge to study the selected factors affecting the signals obtained from sensors. It was revealed that factors such as striking method, presence of background noise, layered soils, and the distance between the borehole and the piles can affect the PS test data in steel H-piles. The findings of this study can help engineers in performing field tests as well as interpreting the results. The results of this experimental study could also validate a part of the conclusions of a recent theoretical study on the performance of PS tests in layered soils.