Journal of Performance of Constructed Facilities

Existing research studies have primarily examined the progressive collapse of frame structures under an inner column removal scenario. However, progressive collapse risk is much higher when penultimate columns close to the structural periphery are damaged due to weaker horizontal constraints. A static progressive collapse test was thus conducted in this study on two single-story beam-column planar substructures with flange slabs, in which a penultimate and an inner column were removed respectively. Compared to the specimen with an inner column removal, the specimen with a penultimate column removal exhibited a larger vertical displacement under the small deformation stage, which further reduced the contribution of the compressive arch action to the collapse resistance. Under the large deformation stage, the resistance of the specimen with an inner column removal increased significantly, while that with a penultimate column removal was not enhanced notably because the horizontal movement of its edge column resulted in a smaller rise of steel strains under the catenary action. The internal forces were calculated using the measured strain data at the key sections of the slab-flange beams. The calculated results also confirm that the compressive arch action and catenary action were unable to be fully developed in the specimen with a missing penultimate column. Finally, the outcome of the vulnerability assessment of the prototype reinforced concrete frame reveals that there might be a potential risk of progressive collapse to the structure under large deformations when a penultimate column on the ground floor is damaged and the risk is higher when a penultimate column on the top floor is damaged.

Structural renovation is an economic choice to expand the space of existing frame buildings. To this end, removing a column and strengthening the adjacent beams and columns are required. The renovation should not only redistribute gravity loads but also sustain horizontal seismic actions in seismic regions. Therefore, in this paper, the seismic behavior of a 2-story 2-bay RC frame and a corresponding renovated RC frame after a column removal at the ground story, retrofitted by steel X-bracing at the second story with strengthened beams and columns at the renovated story, is experimentally investigated under cyclic loading. The results demonstrate that the lateral stiffness and peak capacity of the renovated frame are substantially larger than those of the original frame, but the ultimate deformation capacity of the renovated frame is smaller and the energy-dissipation capacity is similar to the original frame. Moreover, macro-based finite-element numerical models of the renovated frame are built, validated, and used for parametric studies. The numerical results suggest that this renovation should be used with the axial compression ratio of side columns in the braced story not greater than 0.5. Finally, this renovation is likely to introduce a soft lower story for a planar 2-bay 2-story frame. Consequently, it is necessary to control the dimensions of strengthened columns, and it is suggested that the elastic lateral stiffness ratio of the renovated story (i.e., with a larger space) to the braced story should be greater than 0.5.

This paper investigated the behavior of three-dimensional (3D) steel-concrete building under external explosion considering the slab and connection rigidity. Most of the work carried out so far in the progressive collapse area followed the threat-independent alternate load path (ALP) methodology as a design guide. This study presents a simplified two-stage nonlinear dynamic analysis using Abaqus FE. The number of columns likely to be removed in progressive collapse due to blast is determined using a three-step restart analysis in the first stage. Collapse analysis of the entire building is carried out in the second stage, and the results were compared with nonlinear dynamic analysis of the ALP. The numerical model was validated with the data obtained from experimental works and the results showed good agreement. It was concluded that the ALP usually is not conservative; more columns may be eliminated under heavy explosion, and collapse analysis is required to capture the real behavior. The well-known failure criteria for yielding, fracture, and stability are not efficient enough, and the damage index criterion which basically depends on the global column behavior and its remaining axial capacity should be used.

To predict the hazard-induced risks of buildings and infrastructures and assess the losses caused by hazards, the fragility curve method is a common quantitative risk assessment procedure for civil structures. It has been popularly used for decades for different hazards including earthquakes, hazardous winds, tsunamis, and fires. However, there are limited reports regarding blast risk assessment of buildings using the fragility curve method. This study developed empirical blast fragility curves for wood residential buildings using the real 2013 West fertilizer plant explosion data. The development processes included five key steps: (1) selecting and calculating the blast hazard intensity measure and the air-blast incident overpressure; (2) selecting the damage states rating systems and classifying the damage state of each damaged building; (3) determining the frequency distribution of damaged buildings for each damage state; (4) proving the cumulative lognormal distribution function to describe the fragility relationship between the blast damage states and the blast hazard intensity measure; and (5) constructing the empirical fragility curves by fitting the building damage information to the selected fragility relationship distribution function. The resulted blast fragility curves of this study can be used by government officials to predict blast-induced damages of residential buildings, to plan the optimal locations and operational capacities of emergency facilities, to estimate total economic losses due to potential explosions, and to plan the social, physical and economic resilience of communities.

Solar energy is expected to provide between 15% and 30% of US electricity by 2050. Photovoltaic solar plant infrastructure includes the photovoltaic modules, structure, and balance of components. Decisions regarding the future integrity of a solar plant depend in part on an accurate assessment of the site environment and conditions affecting its corrosion and hence its rate of degradation. This paper presents a framework that improves the performance evaluation of corrosion rates and estimated service lives of steel posts supporting tracker and fixed-tilt solar energy infrastructure systems. The authors developed new statistical models and integrated them with current existing models to identify individualized optimal corrosion-assessment approaches for constructed posts, and assess their performance, depending on each plant’s unique site environment. Applying the new and existing underground corrosion models to data from 62 solar infrastructure sites demonstrated the superiority of the newly developed approach in predicting steel structures’ underground corrosion rates in highly corrosive environments. The findings of this paper will inform and support decision makers in infrastructure facility design, maintenance, and reliability applications.

Given the premise that a communication tower is a vital infrastructure that may collapse when encountering a wind disaster, this paper focused on investigating the collapse mechanism and collapse fragility of a communication tower subjected to wind loads. In this paper, a finite-element (FE) model of a 60-m-tall communication tower that collapsed under wind loads was created in ABAQUS (version 6.10). The wind-induced response was studied considering member buckling, and the Tian-Ma-Qu material model was used. Based on the dynamic explicit method, collapse simulations of the tower were performed with different wind attack angles using the incremental dynamic analysis (IDA) method. Subsequently, the weak position and the collapse mechanism of the tower were summarized. The results indicated that the Tian-Ma-Qu material model was effective in simulating the collapse of communication towers; the buckling of the main members was the governing reason for the progressive collapse of the tower. Thus, the main members should be strengthened in the design. Furthermore, the collapse fragility analysis of the tower was investigated, and the influence of the wind attack angle was discussed. The results demonstrated that the wind attack angle had a significant impact on the collapse fragility curve and the ultimate capacity.

A finite-element modeling study on the progressive collapse of steel moment-resisting frames under column removal scenarios is presented. Different parameters, such as location of initial local failure, number of story, material strain-rate effects, and column removal time (CRT), are considered. The model structures are analyzed using static- and dynamic-incremental analyses. The former being the well-known pushdown simulations, and the latter performed through dynamic column removal at various gravitational load levels. The progressive collapse potential is mainly related to location of initial failure and size (height) of the models, which determine the affected area after initial local failure. To compare the results, the displacement-based dynamic amplification factor (DAF) is also adopted. It is observed that above a certain gravitational load, the dynamic simulations accounting for material strain rate show displacements smaller than the ones predicted by the static analysis. With the decrease of CRT, the progressive collapse capacity decreases, but DAF tends to be independent from CRT when the systems experience large plastic displacements.

In this paper, experiments and finite-element analyses are used to investigate the wind-induced vibration in high-tech factories. The experimental results during the Megi typhoon on September 27, 2016, indicated that wind-induced vibration cannot be ignored in high-tech factories, while horizontal vibration is much larger than the vertical one, and the vibration at the first natural frequency of the building is obviously dominant for the wind-induced vibration. Moreover, a reinforced concrete level can meet the vibration criteria at more severe wind conditions than a steel level is able to. In the finite-element analysis, the TurbSim version 1.06.00 software package is used to generate the time-dependent turbulence wind speed field, and the finite-element results are calibrated with the experimental measurements. The finite-element parametric study then indicates that a reduction in the floor vibration of a high-tech factory is feasible due to the shade of adjacent buildings. However, this reduction is negligible when the height of the shading building is not more than 60% of the factory height. For high-tech factories with long span trusses, increasing the member sizes to reduce wind-induced vibration, including the bracing, wall, and column members, may not be efficient and should be considered conservatively.

The utilization of continuously reinforced concrete pavement (CRCP) has been widely used throughout the United States during the construction of interstate highways since the 1930s. The essential design criterion of CRCP is to manage the crack type, size, and spacing that forms to reduce the distress; thus, identification of the factors affecting the location and extent of the cracks and distresses provides a prediction for the service life of CRCP pavements. In this paper, the influence that reinforcement placement and concrete cover has on the distresses of CRCPs is investigated using ground penetrating radar (GPR) and eddy current technology at six major interstate and state highway locations in Georgia. It was concluded that pavement having inefficient concrete cover depth and pavement thickness results in increased clusters of single transverse cracks and/or punchouts. A result of this study is the recommendation that longitudinal reinforcement be placed at one-third of the depth of the slab from the top surface of the pavement. Furthermore, a distress factor (DF) was established as a good indicator of the performances of pavements relative to each other. Ideal pavement with no crack acquires a DF of 0. In this study, pavements in good, fair, and poor conditions received DFs of “0.03 and 0.05,” “0.97 and 0.98,” and “3.23 and 3.33,” respectively.

Objective and scientific risk assessment is of great significance for tunnel construction. The intrinsic link between risk level and influencing factors are poorly understood, and our ability to assess the risks of tunnel construction remains limited. In this study, we improved the normal cloud model to combine fuzziness and randomness into risk assessment to make the result more accurate. First, we constructed the risk index system for tunnel construction; second, we calculated the weight of the risk index by using the AHP method. Then we determined the improved cloud model eigenvalue through investigation and analysis and put the risk index data into a forward cloud generator to obtain the fuzzy comprehensive evaluation matrix. Following this, we combined weights with the matrix to receive the membership degree of different risk levels. Finally, the final risk level was obtained by analyzing the purposely designed membership radar chart. We applied this assessment model to evaluate the construction risk of the Tiger Mountain tunnel in section $\mathrm{ZK}3+280–\mathrm{ZK}3+300$. The study shows that the improved cloud model delivers a more scientific and reasonable risk assessment by using the fuzzy random theory, which introduces a new concept for risk assessment in tunnel construction.

Truck platooning is a futuristic transportation system that is being explored by many countries and several states in the United States in a collaborative environment among stakeholders through on-road pilot testing and actual platooning. However, there are hundreds of thousands of bridges in the United States alone that have not been designed for this new loading. Per AASHTO methodology, bridge design is based on a notional live load model comprised of one or two trucks per lane in conjunction with or separate from an applied uniform load. Platoons with $3+$ multibrand trucks per platoon are proposed to be the norm in the year 2025. An extensive literature search indicated a lack of published work that deals with the effect of truck platooning on the integrity of the superstructure–substructure system. This paper attempts to elucidate and illustrate the impact of truck platooning on the performance and integrity of existing bridges. Based on examples for continuous and simple-beam (stringer or girder) bridges, it is demonstrated that the live load of truck platoons would subject the components of the superstructure and foundation to straining actions that are several times higher than allowed by their current load rating. A case study representing a typical scenario for truck platooning is provided to shed light on the impact of platooning on the foundation of an existing bridge. The results clearly demonstrate that a reduced integrated bridge load rating should be anticipated for truck platoons compared with the conventional single or two truck patterns commonly used in practice. The data presented in this paper provide guidance and a preliminary tool for practicing engineers assessing the impact of truck platooning on existing beam (stringer or girder) bridges. It shows that truck platooning will necessitate new policies, regulations, and standards for both new and existing bridges. If preservation and reuse are to be considered preferable to replacement, implementation of new approaches regarding existing structures will be particularly important. The use of an integrated bridge load rating approach is recommended. Whereas the methods of superstructure load rating will vary with the bridge type, the concepts related to the substructure load rating as outlined in the paper remain valid for other types of bridges. However, additional work is needed to substantiate implementation to other bridge types. To streamline all facets of structure maintenance, and to ensure quality control/quality assurance, the authors also advocate the creation of a holistic type of maintenance contract called maintenance engineering and inspection, rather than the push-button contracts more commonly used in the asset management arena.

An alternative approach to predicting seismic performance evaluation of buildings is presented in this study. The procedure is based on an evaluation of the Column Index (CI) that is defined by taking into account parameters such as the weight of the building and bending rigidity in two directions of the columns. The procedure is calibrated, and the threshold values of the CI is evaluated by considering seismic performance of several model buildings designed with the following requirements and by using the advanced nonlinear techniques regarding the Turkish Earthquake Code. According to the proposed procedure, a building satisfies life safety performance level when the CI of the building is smaller than the corresponding threshold value. To determine the threshold values of the CI of the proposed procedure and its sensitivity on the parameters considered, a large number of residential buildings having various structural configurations, story heights, span numbers in two directions, concrete strength, and steel yield stress are selected and designed so that they satisfy the requirements at a minimum level. The accuracy of the proposed procedure is examined on the existing buildings, and it is found that the procedure has a predictive power of 82% and 94% depending on material quality.

Tunnel fires often cause huge damage to the lining structure. In order to avoid cracking and spalling of the lining in the case of large-scale tunnel fires and thus ensure the safety of the tunnel, a new tunnel-fire-resistance approach was proposed based on the ${\mathrm{SiO}}_2$ aerogel material. Numerical simulation models of a tunnel were established and the internal temperature distribution of the lining was studied to verify the feasibility of this new approach. The thermal insulation effect between the ${\mathrm{SiO}}_2$-aerogel-coated lining and the conventional lining under simulating fire was comparatively analyzed. After 1 h of simulating fire, the temperature of the 50-mm-thick concrete on the surface layer of the conventional lining exceeded 600°C. This temperature was enough to cause serious cracking, spalling, and even bursting of the tunnel lining. For the ${\mathrm{SiO}}_2$-aerogel-coated lining, the internal temperature of the lining was kept below 200°C, and most of the area was even below 100°C. The results indicated that the fire-resistance performance of the tunnel lining can be significantly enhanced by using the ${\mathrm{SiO}}_2$ aerogel coating. In the future, it will have excellent application potential in the field of tunnel-fire protection.

This paper presents an investigation on the rotational behaviors of fork-column Dou-Gong. Five scaled specimens in different construction forms were manufactured and tested by low reversed cyclic loading under three different vertical loads. The failure modes, envelope curve, strength degradation, deformability ratio, stiffness degeneration, and energy dissipation were assessed and compared. The results indicated that the increment of the rotational stiffness gradually decreases with increased vertical load. The relationship between rotational stiffness and vertical load can be simplicity expressed by a logarithmic function. The length, construction form, and number of linking beams are the main parameters affecting the rotational behaviors of single Dou-Gong. Reducing the length or enhancing the combined effect of the linking beams can effectively improve the bearing capacity and deformation capacity of the Dou-Gong, as well as energy dissipation capacity. The rotational behaviors of single Dou-Gong with one linking beam are worse than those of Dou-Gong linked by two beams. In addition, the double Dou-Gong exhibits better symmetry and plumper area than the single Dou-Gong, thus resulting in 109%, 78%, and 163% increment in bearing capacity, rotational stiffness, and energy dissipation, respectively. The moment-rotation curve of fork-column Dou-Gong is nearly trilinear and based on the appropriate mechanical parameters from the test results, the nonlinear hysteresis characteristics of the fork-column Dou-Gong can be simulated by an improved double-target model.

The objective of enterprise building infrastructure management is to provide optimal allocation of maintenance, rehabilitation, and repair (MR&R) resources and to preserve the condition of building components over a planning horizon. While most approaches in the literature have studied it as a finite resource allocation problem, the presence of an underlying building network configuration has not been fully explored. The development of a network model encompassing interrelated building components introduces challenges as well as opportunities for MR&R decision making and optimized building preservation, which cannot adequately be managed using the existing decision-making frameworks. One challenge to enterprise building portfolio management is lack of understanding of the effect of one component’s condition state on another. Building component network-level optimization is not available as in other infrastructure domains, which makes calculating the benefit of component work activities on other building components very difficult to determine. This research focuses on using structured query language (SQL) based association rule mining to find frequent patterns of observed condition deterioration among different component types. This work introduces a new metric, negative effective deterioration, which is based on actual deterioration observed from inspection data relative to expected condition states. Frequent patterns of antecedent and consequent component pairs having negative effective deterioration states are discovered, and support and confidence factors indicate the strength of these network-level connections. The building component network model can improve enterprise work planning by considering the effects of negative effective deterioration on other components. This work uses case studies and data from the US Department of Defense (DoD), which owns and operates over 275,000 buildings totaling nearly 2.2 billion gross square feet (GSF) and $705 billion in plant replacement value. This paper presents a conceptual model to support building system condition assessment and MR&R decision making. This process can decrease the long-term deferred deficiency backlog by focusing limited MR&R resources not only on the components in the worst condition, but on those that would have the most adverse effect on the condition of associated components.

Acoustic emission (AE) data were investigated to better understand damage conditions in a three-span prestressed concrete girder bridge during a load test. The innovation lies in classification of crack extensions (stable or unstable) during the loading and holding processes. The gap in current literature addressed is a shortage of data and findings on bridges in operation and having inclined cracks. This manuscript addresses processing of AE signals recorded by piezoelectric sensors attached on two interior girders toward the obtuse corner of the bridge while under loading. Results showed indications of crack propagation beyond the existing cracks during both loading and load holds. Damage classification procedures based on AE data recorded during one loading and holding step are discussed. Shear strength analysis using modified compression field theory (MCFT) was performed to place the results in the context of potential overloads.

A triple friction pendulum bearing (TFPB) as an isolator has been considered more competitive than conventional bearings such as rubber bearings or single friction pendulum bearings due to its versatile behaviors under different levels of earthquakes. However, as the seismic responses are reduced, the wind-induced responses of the building may increase simultaneously, and this phenomenon is more common for isolated high-rise buildings compared with midrise and low-rise structures. In this paper, an analytical model for an isolated high-rise building with TFPB and a magnetorheological (MR) damper is proposed. An optimal fuzzy logic controller (FLC) is further proposed based on the multiobjective method, so as to reduce the wind responses without diminishing the base-isolation effect. To evaluate the proposed controller, seismic and wind-induced responses of the building controlled by the optimal FLC are compared with those of the building using the human-designed FLC and the building without control. According to the numerical analyses, it is found that although wind-induced responses can be reduced by both controllers, the human-designed FLC may reduce the wind-induced responses at the expense of increased seismic responses (increased by 12% in average of maximum absolute accelerations), whereas the optimal FLC can reduce both the wind and seismic responses (the reduction of maximum absolute accelerations is no less than 48% and 9%, respectively).

Missing building attributes are problematic for development of data-based fragility models. Relative to other disciplines, the application of imputation techniques is limited in the field of engineering. Current imputation techniques to replace missing building attributes lack evaluations of imputation model performance, which ensure accuracy and validity of the imputed data. This paper presents two imputation approaches, along with imputation diagnostic and comparison approaches, for binary building attribute data with missing observations. Predictive mean matching (PMM) and multiple imputation (MI) are used to impute foundation type and number of stories attributes. The diagnostic approach, based on the logistic regression goodness-of-fit test, is used to evaluate the imputation model fit. The comparison approach, based on the percentage of correctly imputed observations, is used to evaluate the imputation model performance. A data set of single-family homes damaged by the 2005 Hurricane Katrina is used to demonstrate implementation of the methodology. Based on the comparison approach, PMM models showed 9% and 2% greater accuracy than MI models in imputing foundation type and number of stories, respectively.

Deck unseating at abutments and in-span hinges can be a major cause of collapse, especially for older multiframe bridges that are not in compliance with the latest code provisions for seat lengths. This study investigated the effectiveness and implications of using two common retrofit measures to reduce or eliminate deck unseating risks: restrainer cables, and shear keys. A combination of restrainer cables and shear keys at the abutments and the in-span hinge was proposed and investigated as a potential retrofit measure to limit excessive movement of decks and eliminate unseating risks of older multiframe RC bridges with regular and irregular geometry. Six four-span multiframe bridge configurations were considered: straight, skewed, and curved bridges, with equal and unequal pier heights. Detailed finite-element models for all configurations were developed to conduct nonlinear time history analysis (NTHA) under five different ground motions representing weak, moderate, and strong earthquake scenarios. The average of the NTHA results showed that the combination of restrainer cables and shear keys is more effective than using individual measures to reduce displacement demands for irregular bridge configurations, in which coupling between the response in the longitudinal and transverse directions is more pronounced.

This paper analyzes measured triaxial vibrations of road and rail traffic on and around a typical residential masonry building in İstanbul and its response to adjacent ground-born vibrations through numerical modeling. Therefore, to determine the dynamic behavior and resultant internal forces within the building, which stands between a road and a railway line, a numerical model was created, updated, and validated through the measured vibrations. The results show that train-induced vibrations caused the walls of the building to experience tensile stresses up to 23% of the masonry tensile strength. Additionally, the measured maximum vibration level on the building is well above the limit for complaints in residential environments and very close to the damage limit for historic and sensitive structures. Furthermore, a nearby vibration amplification zone on the ground surface suggests potential amplified loadings. Therefore, human responses to these prolonged vibrations should be the controlling factor, entailing site-specific analyses by the codes of practice in cities with dense traffic.

In 2018, under service conditions, excessive deflections were observed in the long-span timber beams of the first floor of the former Sant’Elisabetta Monastery in Palermo (Italy). The building was constructed in the 16th century. Over the years, it underwent several modifications and, finally, in 1900, became a barrack. In the middle of the twentieth century, the monastery was submitted to maintenance works consisting of the reconstruction of the first floor with timber beams and the reconstruction of the roof with timber trusses. In the summer of 2018, anomalous and excessive deflections of the primary beams on the first floor approaching $1/50$th of the span were observed, raising concerns. Therefore, an experimental investigation was carried out to establish the causes of the damage and to identify a retrofitting design. In this work, extensive experimental research was carried out to characterize the timber materials and structural members through static and dynamic tests. The results obtained represent support of a strengthening design for the timber beams, and the design’s main execution phases are described in this paper. The lesson learned from the case study could help professional engineers be aware of the main peculiarities and deficiencies of structural systems affected by material degradation—in this case, mainly depending on construction mistakes—and the importance of in situ periodical checks during the useful life of structures.

Pipelines serve as critical infrastructure, and shutdowns of any duration can cause interruptions to sensitive supply chains. This paper develops a model using 789 incidents involving a hazardous liquid pipeline emergency shutdown with durations varying from a few minutes to months. A hazard-based duration analysis is used to understand the characteristics and mechanisms that influence how long a facility remained shut down. A parametric Weibull model with gamma heterogeneity is used to account for unobserved characteristics in the reported data. The insights gained from the duration analysis help to identify specific characteristics and areas that operators can address to decrease interruption durations. The findings address specific areas including response plans, incident locations, and maintenance programs where practices and policies could be implemented to reduce shutdown duration. Quantitative interpretation from marginal effects is presented, which can identify the improvement in duration rate for implemented changes. The model was applied to an historical incident in Marshall, Michigan, which confirmed the findings from the model.

The seismic behavior of Lushan Middle School gymnasium, whose grid structure was heavily damaged during the $M_{w}7.0$ Lushan earthquake in 2013, is simulated by three finite-element models. In field observations, 72 buckled members were found, but no tensile failure or obvious tensile yield was found. The results of each model are analyzed by comparing the simulated damage with field observations. The results suggest that Model A shows the best analysis results, followed by Model C, and finally Model B. Causes of seismic damage not only the uneven stiffness of the structure’s support columns caused by ring beams leads to redistribution of the internal forces, but the dynamic amplification effect of the lower frames also intensified the damage to the grid structure. Therefore, the authors recommend that the code should distinguish between pure grid structures and grid structures supported by RC frames and introduce design models that integrate the two structures and include a coupling effect between them. In addition, the integrated model should be used in a seismic check of grid structures with concrete supporting structures.

A community’s resilience relies on the resilience of its infrastructure systems and the many individual buildings that form the built environment. In evaluating the resilience of an individual building, it is fundamental to quantitatively define its functionality. In this paper, the functionality and its variation of a seismically based-isolated building after a rainstorm is quantitatively assessed using a component-based framework. The overall functionality of the building is taken as the weighted average of several primary functions, which are further divided into subfunctions. Each subfunction is related to a group of nonstructural components (NCs), many of which are supported by urban utilities. Hence, the quantitative functionality is correlated with the performance of specific NCs and utilities, the damage to which can be estimated through fragility analysis in a hazardous event. The observed damage to the NCs in the building of concern following a rainstorm and their realistic recovery process were recorded and used as input in the framework. The results show that a facility that is deemed to be highly resilient to a specific hazard could exhibit poor resilience to another type of hazard and that the resilience to a particular hazard could be readily enhanced if only the hazard were anticipated.

A pin connection is often used to join the hangers with the main cable and main girder in a suspension bridge. As the bridge moves under live or wind loads, the pin-connection components are subject to repetitive loading. The loading causes wear to connection components such as bushings; hence, they often have a shorter life span than other bridge components. In this paper, damage of a bushing in a pin connection between the suspender and deck in a suspension bridge is investigated, and laboratory tests are performed to find a more durable material for the bushing. First, damage of pin-connection components in a suspension bridge is introduced. Secondly, laboratory tests are conducted to determine a more durable bushing material. Finally, conclusions are given that could provide reference for maintenance of suspender connection components in similar suspension bridges.

Nondestructive methods have been extensively used to characterize unknown bridge foundations. Among various nondestructive methods, conventional and reverse parallel seismic (PS) methods are considered proper methods capable of determining the depth of piles made of common construction materials, such as wood, steel, and reinforced concrete. Previous studies have indicated that the PS tests results are influenced by the distance between the borehole and the tested pile, the pile length, the stiffness of the surrounding soil, and the defects of the pile. In the current study, the method of striking is identified and discussed as another influencing factor. Several conventional PS tests were conducted on wood piles of a highway bridge. The conventional PS results showed that vertical, inclined, and horizontal striking methods can produce results with various levels of reliability. However, the vertical and the inclined striking can produce more interpretable signals compared to the horizontal striking. In addition, the results of this study showed that the conditions and stiffness of the foundation may be another factor that can adversely affect the success of reverse PS tests.

Sediments transported by heavy rainfall result from frequent typhoons in the Tseng-Wen reservoir, which now comprise one-third of the capacity of the reservoir. Yearly increases of $6.56\text{million}{\mathrm{m}}^3$ deposits are planned for ejection via a newly operational desilting tunnel to extend the serving capacity of this reservoir, which is the most important reservoir in Taiwan. The first worldwide experimentation of cooperative underwater blasting to loosen compacted sediment within a reservoir, then dispelled by a desilting tunnel, is carried out for demonstrating the feasibility and efficiency. Precautionary measurements are very strict for managing underwater explosions in an operating reservoir without jeopardizing its mission and structure safety. When choosing the detonating locations, the sediment thickness is determined by a shot wave spectrum ratio method with a small amount dynamite test shot for avoiding the bed rock fracture affected by the blasting. Vibrations, turbidity, underwater life, and water content affected by the explosion have all been assessed. When applying counter measurements before the detonation, affecting the underwater life could be reduced; the influence of water quality by a water gel dynamite explosion was very minimum and vanished a few hours after the blasting. A distance of 50 m away from the dam is set as a safety perimeter for an underwater explosion, for which the specified amount of dynamite is determined with a consideration of distance and the applied method of blasting. The free drop method can use 10 times the amount of dynamite than in-hole blasting at the same location and where the affected deposit volume is around $10{\mathrm{m}}^3$ per kg via free drop blasting. In-hole blasting disturbs more compacted sediment than free drop methods, and the effect of an applied in-hole blasting in combination with a traditional mechanical dredge is shown to lead to a 250% improvement. To achieve the best desilting tunnel efficiency, a deep underwater groove via blasting is recommended. With proper design, half of the existing compact deposits in the Tseng-Wen reservoir could be removed, thus increasing the capacity of the largest reservoir in Taiwan as much as 15%, which is equivalent to $75\text{million}{\mathrm{m}}^3$. Recompacting the underwater blasting disturbed sediment still could be expelled via desilting tunnel water discharging six months after the blasting operation shown by this experiment. This finding supports the feasibility of operating the blasting work at the dry season and waiting for the rainfall the loosen sediment away via desilting tunnel discharging.