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Precast concrete frames have been widely used, though little is known about their fragility under the combined influence of seismic excitation and corrosion. In this study, one four-story p...

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 ...

This paper focuses on the maintenance decision of vulnerable parts that need rehabilitating within the design service period under repetitive vehicular loads in steel bridges based on the t...

A novel self-centering cable brace (SCCB) with friction devices was developed to improve the seismic performance of existing frame structures. To investigate the enhancing effect of the SCC...

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 ...

Expansion joints of bridge superstructures generally suffer deterioration more severely than their main structures, and their actual service life is generally shorter than their design serv...

Rib-to-deck joints in orthotropic steel decks (OSDs) are among the most fatigue-prone details of steel bridges. To improve the fatigue performance of existing bridges with OSDs, a strengthe...

Suspenders are critical force transmission components in suspension and arch bridges, which connect the girder to the main cable/arch. Field inspection indicates that short suspenders at th...

In order to adapt to a new site planning of the Porcelain Tower of Nanjing, China, two two-story and one three-story historical masonry building built in the 1930s were translocated. Becaus...

The Beijing Olympic Watchtower (BOW) is a landmark building with irregular shape and complex structural configuration; however, excessive human-induced vibrations of the sightseeing platfor...

Recent large earthquakes in China (e.g., Wenchuan earthquake and Yushu earthquake) resulted in enormous damage to school buildings and took many students’ lives. Recognizing the seismic vulnerability of existing school buildings, the Chinese government started a nationwide mission in 2009, aiming at increasing the seismic capacity of school buildings through inspection and retrofit activities. This paper presents the experiences of the authors in the retrofits of school buildings in which seismic isolation by using rubber and/or sliding bearings was adopted as a new and efficient retrofit technique, as compared with conventional ones. The retrofitted school buildings include masonry buildings, RC frame buildings, and a mixture of both. Design methods and the corresponding requirements in the modified seismic design code are presented, and typical construction procedures of the seismic retrofit are summarized from an engineer’s point of view. Procedures regarding the contract and review of the retr...

This case study presents the horizontal translocation of the Hongxing Mansion, a high-rise building in China, which was moved transversally for 26 m because of modifications in urban planning. The 13-story RC frame-wall structure was built in 2002 with a total height of 63.2 m and a total weight of 109,881 kN, making the project unique as compared with other similar cases. The executive process of this project is introduced, including the initial planning, design, and construction procedures. A load underpinning system was proposed that can transfer the vertical loads uniformly to the rails and distribute the propelling loads from the loaded end to the other end of the building. Anchor-jacked piles were used at the original foundation from the limited indoor clear height so that rails in the original basement can be well supported without the need of large piling machines. A special moving system was proposed and successfully applied, which combined the advantages of pull and push, so that the eff...

For long-span prestressed concrete (PSC) box-girder bridges, excessive midspan deflection because of uncertain concrete shrinkage and creep undermines driving comfort and structural safety. In this paper, a deflection control strategy is proposed on the basis of field monitoring and probabilistic finite element analysis (FEA). The time-dependent behavior of the bridge was predicted using a three-dimensional finite element model with integrated time-dependent models for creep and shrinkage. The FE model was validated or updated according to field monitored data to predict future bridge performance. Using probability density functions of variables and probabilistic analyses, uncertainties in long-term deflections were described. Finally, according to the probabilistic analysis results and the allowable deflection, the amount for deflection control was determined, and the control was conducted using backup prestressing tendons. A case study on the Jinghang Canal Bridge, a three-span continuous PSC bo...

This paper presents the integral lifting and seismic isolation retrofit of the great hall of Nanjing Museum, a 78-year-old cultural and historical building. Due to the need for extension, the great hall of the Nanjing Museum needed to be lifted 3.0 m. The total building area for lifting was 4,830 m2, with a total of 161 lifting points, which made this project quite challenging and also the largest done to date. Moreover, seismic isolation retrofit was utilized to improve the seismic performance of the translocated building. Details of the integral lifting and the seismic retrofit are presented in this paper, which include (1) the load underpinning system, (2) the spatial strengthening truss system, (3) the lifting control system, and (4) the base isolation using laminated rubber isolators. The entire lifting system performed well, and the main construction was finished within 5 months. Seismic time-history analyses were further performed to evaluate the effect of the seismic isolation. It was obse...

Field inspections on long-span steel suspension bridges in China reveal that the pavements undergo a fast deterioration process attributed to the flexibility of suspension bridges and the heavy traffic loads. Such extensive damage and enormous repair costs call for a cost-effective rehabilitation strategy for these bridges. In this paper, the pavement rehabilitation strategy is investigated for the Runyang Suspension Bridge in China with the aid of the life-cycle cost analysis (LCCA). Three alternatives are compared for their economic efficiency, and both agency costs and user costs are taken into account. To consider the uncertainties that abound in the LCCA, probabilistic analyses are made in which the Latin hypercube method is used to provide samples of random variables. According to the LCCA results, the user costs are a considerable proportion of the total costs so that the selection of rehabilitation strategies is significantly influenced by the user costs. In this regard, the second alternative, the double-layer pavement (guss asphalt plus stone matrix asphalt) is the most cost-effective rehabilitation strategy for the bridge. Additionally, sensitivity analyses show that the traffic growth rates, the discount rate, the work zone duration, and the delay cost rate for passenger cars are the most sensitive variables in the user costs. The methodologies and approaches introduced herein can be easily implemented by practitioners and would be of benefit to pavement rehabilitations for steel suspension bridges.

A probabilistic procedure for the assessment of the time-dependent reliability of existing prestressed concrete (PSC) box-girder bridges is presented. These bridges are subject to increased traffic loads and an aggressive environment, which result in structural deterioration such as cracking and corrosion. In this paper, a multiple-peak vehicle load model is proposed based on acquired traffic load data, which cannot be properly described by previous single-peak probability distributions. With the proposed vehicle load model, the maximal vehicle loads during the remaining life of bridges are obtained for evaluating the influence of the increase in traffic loads on bridge reliability. Time-dependent corrosion models are adopted to account for pitting corrosion because of chloride attack as well as uniform corrosion because of concrete carbonation. A degenerated shell element is used for accurate and efficient modeling of the PSC box-girder. Postcracking behaviors of reinforced concrete box-girders, simulated by using different crack models and elements, are compared with laboratory test results. To increase the efficiency of probabilistic analyses, an adaptive importance sampling method in conjunction with the truncated Latin hypercube sampling is used. Application of the proposed methodologies is demonstrated by a case study, in which the time-dependent reliabilities of a deteriorating PSC box-girder bridge are obtained.

Existing structures may be in need of seismic upgrading owing to structural deterioration, change in function or use, increased performance requirements, or modified seismic codes. In recent years, fluid viscous (FV) dampers have received increasing attention because of their notable seismic-reduction capacity and easy installation. This paper outlines the design procedure of seismic upgrading of existing buildings using FV dampers. Discussions are made on some key issues for seismic upgrading using FV dampers, including the analytical damper-brace model under large earthquakes and strategies for damper layout. A case study is made, in which a 21-story hotel built in 1991 was seismic upgraded. One special feature of this project is that only the first six stories can be structurally modified, resulting in limitations on the damper layout. According to the proposed design procedure, 56 FV dampers are suggested for this project, which provide a supplemental damping ratio of 5.3%. As a result, the se...