Solar Radiation Parameters for Assessing Temperature Distributions on Bridge Cross-Sections

Solar radiation is one of the most important factors influencing the temperature distribution on bridge girder cross-sections. The bridge temperature distribution can be estimated using estimation models that incorporate solar radiation data; however, such data could be cost- or time-prohibitive to obtain. A review of literature was carried out on estimation models for solar radiation parameters, including the global solar radiation, beam solar radiation and diffuse solar radiation. Solar radiation data from eight cities in Fujian Province in southeastern China were obtained on site. Solar radiation models applicable to Fujian, China were proposed and verified using the measured data. The linear Ångström–Page model (based on sunshine duration) can be used to estimate the daily global solar radiation. The Collares-Pereira and Rabl model and the Hottel model can be used to estimate the hourly global solar radiation and the beam solar radiation, respectively. Three bridges were chosen as case study, for which the temperature distribution on girder cross-sections were monitored on site. Finite element models (FEM) of cross-sections of bridge girders were implemented using the Midas program. The temperature–time curves obtained from FEM showed very close agreement with the measured values for summertime. Ignoring the solar radiation effect would result in lower and delayed temperature peaks. However, the influence of solar radiation on the temperature distribution in winter is negligible

Timber-concrete composite bridges: Three case studies

During the last years, timber-concrete composite (TCC) structures have been extensively used in Europe both in new and existing buildings. Generally speaking, a composite structure combines the advantages of both materials employed: the strength and stiffness of the concrete in compression and the tensile strength, lightweight, low embodied energy, and aesthetical appearance of the timber. The concrete slab provides protection of the timber beams from direct contact with water, which is crucial to ensure the durability of the timber beams, particularly when used for bridges. Different types of connectors can be used to provide force exchange between the concrete slab and the timber beam. The choice of a structurally effective yet cheap shear connection between the concrete topping and the timber joist is crucial to make the TCC structures a viable solution that can compete with reinforced concrete and steel structures. In this paper, the possibilities offered by TCC structures for short-span bridge decks are discussed. The technology of TCC structures and the general design rules are illustrated. Three case studies are reported, including a short-span bridge tested in Colorado, USA, with the timber layer being constructed from recycled utility poles and notch connection; a TCC bridge with glulam beams and triangular notches with epoxy-glued rebar connectors built in Portugal; and a TCC bridge with glulam beams and rectangular notches built in Germany. All the solutions were found to be structurally effective and aesthetically pleasing. They can all provide a sustainable option for short-span bridges. Keywords: Timber-concrete composite, Bridge, Design, Connection syste

Analysis of the Joint Effects of Thermal Stresses and Corrosion on Integral Abutment Bridges

The corrosion of reinforced concrete structures in coastal areas turns out to be very severe and can extend significantly in windy zones. Additionally, frequent temperature changes and, above all, exposure to extreme temperatures might induce wider cracks and micro‐cracks in concrete structures which, in turn, might accelerate the diffusion of corrosive agents. Motivated by this evidence, the present study aims at verifying the sensitivity of integral abutment bridges to the combined effect of thermal stresses and corrosion. Preliminary results show that a high thermal stress may amplify the negative effects of corrosion but also that the bridge used for the case study is more sensitive to thermal stresses than to corrosion

Impact of gamma-glutamyl carboxylase gene polymorphisms on warfarin dose requirement: A systematic review and meta-analysis

AbstractBackgroundThe Gamma-glutamyl carboxylase (GGCX) gene, as with Vitamin K Epoxide Reductase Complex Subunit 1(VKORC1), CytochromeP450 Complex Subunit 14 F2 (CYP4F2) and CytochromeP450 Complex Subunit2C9 (CYP2C9), is a candidate predictor for appropriate maintenance warfarin dose. However, the association between GGCX gene polymorphisms and warfarin dose requirement is still controversial. To quantify the influence of GGCX polymorphisms on warfarin dose requirements, we performed a systematic review and meta-analysis.MethodsAccording to PRISRM statement (Preferred reporting items for systematic reviews and meta-analyses), a comprehensive literature search was undertaken through August 2014 looking for eligible studies in Embase, Pubmed,Web of Science and the Cochrane Library. The impact of GGCX polymorphisms on mean daily warfarin dose (MDWD) was counted by means of Z test. RevMan 5.2.7 software (developed by the Cochrane Collaboration) was applied to analyze the relationship between GGCX gene polymorphisms and warfarin dose requirements.ResultsNineteen articles including 21 studies with a total of 6957 patients were included in the meta-analysis. Among three investigated single nucleotide polymorphisms (SNPs), rs11676382 showed higher CC genotype frequencies in Asian than those in Caucasian(97.7% vs. 86.9%); patients who were “G carriers” (that is, carried the GGCX rs11676382 CG or GG genotypes) required 27% lower warfarin dose than CC genotype[95%Confidence Interval(CI)=17%-37%, P=0.000, I2%=82.0 and PQ=0.000], moreover, stratified analysis by ethnicity showed similar results in Caucasian(23% lower, 95%CI=12%-33%), but not in Asian. With respect to genetic variation of rs699664 and rs121714145 SNPs, no significant impact on warfarin dose requirements were demonstrated.ConclusionsThis meta-analysis suggested that GGCX rs11676382 polymorphism may be one of factors affecting the dose of warfarin requirement, and the effects are different in different ethnicities. Further studies about this topic in different ethnicities with larger samples are expected to be conducted to validate our results

Retrofit of Existing Bridges with Concept of Integral Abutment Bridge: Static and Dynamic Parametric Analysis

The integral abutment bridge (IAB) constituted by the superstructure and the substructure can achieve a composite action responding as a single structural unit by eliminating or reducing expansion joints and bearings. Accordingly, the construction and maintenance costs can be reduced. Therefore, the IAB concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also during refurbishment processes. The research topic concerns the retrofit of existing bridges with the IAB concept. In order to investigate the retrofitting technique with the IAB concept, the literature survey on the practical applications of this approach in worldwide was carried out firstly, including retrofitting motivations, detailed processes and structural performance after retrofitting. Besides, another literature review on the critical issues of analysis on the IAB, such as soil-structure interactions, modelling approaches and plastic hinge simulations, was conducted in order to find out the most suitable method in modelling. The case study of a simply supported prestressed concrete bridge (named Viadotto Serrone) with three spans constructed in 1972 was analyzed, which has some durability problems nowadays. The finite element model was built, involving soil-structure interactions, non-linear behaviors and retrofitting processes. The original and updated Italian design codes are compared through static analysis and seismic analysis. Another investigation was conducted to prove the necessity of considering soil-structure interactions in the IAB. Based on the appropriate finite element model, a large number of static sensitive analyses were carried out, taking thermal actions; bridge types; soil conditions and substructure heights as parameters. Through analysing the responses of girders, piers, abutment stems and piles, some important factors and the corresponding influence were found, which could be adopted to guide the retrofitting technique with the IAB concept. Then, the verification was conducted in order to check if the existing sections could be reused without any changes and point out the most critical components, which need to be repaired or replaced. Moreover, the dynamic performance of bridge before and after retrofitting was investigated preliminarily through modal analysis and response spectrum analysis

Semi static loads in an integral abutment bridge

In order to solve the durability problem of expansion joints and bearings, Integral Abutment Bridges (IAB) have become more and more popular. Soil Structure Interaction (SSI) is a factor that conditions the possibility of the construction of a new IAB, or the retrofitting of an existing from a simply supported bridge into an IAB. Under imposed actions, e.g., horizontal expansion and contraction induced by thermal variation and time-dependent effects (creep and shrinkage), the connection between a super- And substructure responding as a frame structure makes IABs different from other conventional bridges that introduce forces due to SSI. Therefore, the overall horizontal stiffness is mainly due to i) the piles' stiffness, which is usually flexible enough to allow for the deformation of the superstructure and strong enough to carry out the vertical loads, and ii) the type of soil behind the bridge abutment, which has a different stiffness depending on its compaction and composition. Several approaches have been proposed in the literature to consider these types of interaction. In this paper, the accuracy of different formulations commonly used in IABs' design and based on p-y curves and the cantilever method was evaluated. Formulations for piles and abutments were first introduced. Then, a fully integral abutment bridge built in China was considered as a case study. A finite element model of the bridge using SAP2000 software was implemented, and the influence of different methods and formulations was investigated. Finally, the obtained results for different types of soil and approaches were compared and discussed

A probabilistic evaluation of an integral abutment bridge

In last years, a new trend in the construction of short and medium span bridges has raised in some countries. The solution of an Integral Abutment Bridge (IAB), when possible to do, reduces the cost of construction and maintenance because expansion joints and bearings are not necessary. With the development of reliability approach, it is possible to develop a probabilistic analysis of a structure to study the behavior of the bridge in a more realistic way. A big effort has done in the present years to realize different reliability studies on bridges, but only focused on gravitational loads, without paying much attention to temperature, creep, shrinkage and the interaction of the soil and the structure by the stiffness of the soil around the infrastructure. This work will develop the state of art on literature for the study of this kind of variables in a probabilistic analysis of IAB

A repair and retrofitting intervention to improve plastic dissipation and shear strength of Chinese RC bridges

In this paper a rapid repair and retrofitting technique for reinforced concrete (rc) Chinese bridges damaged by a strong earthquake, is proposed and tested. This intervention is an upgrade of the one tested with very good results during a previous experimental research on bridges designed according to the old Italian code without proper seismic details. The improvement of the repair operation consists in the use of dissipation systems to substitute the damaged rebar parts at pier base guaranteeing the correct plastic distribution in plastic hinge only. Dissipation systems with different configurations were considered to optimize the intervention. The repaired and retrofitted Italian bridge already studied in the previous research, was designed according to Chinese codes but with insufficient transversal steel reinforcement. Some pier specimens (scale 1:6) of the most stressed pier of this bridge, with and without dissipation systems, were built. A C-FRP wrapping was applied to increase the insufficient shear strength and the ductility in plastic hinge. Cyclic tests were carried out on the scaled specimens at Fuzhou University lab (China) to evaluate the effectiveness of the proposed technique

The optimal shapes of piles in integral abutment bridges

Integral abutment bridges (IABs) can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possibilities were considered and compared: (a) a pile with two different diameters along the depth and (b) a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre-deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges (L = 500 m) with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization cases were considered with similar study criteria as the Isola della Scala Bridge: (a) a pinned pile head for semi-integral abutment, (b) a fixed pile head without a pre-hole, (c) a fixed pile head with a pre-hole of any depth, (d) a fixed pile head of a pre-hole with a depth limit (< 2 m) allowing for enough embedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abutment bridges