74,064 research outputs found
Seismic analyses of a R/C building: study of a retrofitting solution
No full textThe preliminary experimental results from the tests on a 4-storey R/C frame structure are presented and discussed. The full-scale model is representative of the common practice of 40~50 years ago in most south European countries. Special attention is devoted to the study of a retrofitting solution based on bracing and rubber dissipaters, which intends to increase stiffness and damping reducing consequently the earthquake deformation demands
Linear oscillations of axisymmetric viscous liquid bridges
No full textSmall amplitude free oscillations of axisymmetric capillary bridges are considered for varying values of the capillary Reynolds number C-1 and the slenderness of the bridge Λ . A semi-analytical method is presented that provides cheap and accurate results for arbitrary values of C-1 and Λ ; several asymptotic limits (namely, C>> 1, C>>1, Λ >> 1 \ {and} \ |π -Λ |>> 1 ) are considered in some detail, and the associated approximate results are checked. A fairly complete picture of the (fairly complex) spectrum of the linear problem is obtained for varying values of C and Λ . Two kinds of normal modes, called capillary and hydrodynamic respectively, are almost always clearly identified, the former being associated with free surface deformation and the latter, only with the internal flow field; when C is small the damping rate associated with both kind of modes is comparable, and the hydrodynamic ones explain the appearance of secondary (steady or slowly-varying) streaming flow
Structural modelling of suspension bridges with particular reference to the humber bridge
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The purpose of this research was to investigate the parameters that influence the structural behaviour of a specific suspension bridge, The Humber Bridge.
Three finite element computer models of increasing complexity were created for the analyses. They were validated against field measurements for both static and dynamic loading, and good correlation was obtained.
The programs were used to
a) Assess the integrity of the bridge as a whole were three failures of certain individual elements, such as a hanger falling under vehicle impact;
b) Determine the influence of the sizing of individual components, such as deck plate thickness or main cable diameter, on overall behaviour;
c) ascertain the capability of the structure to cope with loading (traffic, wind orthermal), above the original design values; and
d) consider the performance of the bridge had other configurations of hangers been adopted in the original design.
From the results of this work, recommendations are made which could influence the future design of long-span suspension bridges
The Influence of Correclation on the Extreme Traffic Loading of Bridges
No full textBridge Maintenance, Safety and Management (IABMAS'10) the Fifth International IABMAS Conference, Philadelphia, USA, 11-15 July 2010Accurate traffic loading models based on measured data are essential for the accurate assessment
of existing bridges. There are well-established methods for the Monte Carlo simulation of single lanes
of traffic, and this can easily be extended to model the loading on bridges with two independent streams of
traffic in opposing directions. However, a typical highway bridge will have multiple lanes in the same direction,
and various types of correlation are evident in measured traffic. This paper analyses traffic patterns using
multi-lane WIM data collected at two European sites. It describes an approach to the Monte Carlo simulation
of this traffic which applies variable bandwidth kernel density estimators to empirical traffic patterns of vehicle
weights, gaps and speeds. This method provides a good match with measured data for multi-truck bridge
loading events, and it is shown that correlation has a small but significant effect on lifetime maximum load effects.Deposited by bulk impor
Dynamic nonlinear analyses for the 4-storey infilled R/C frame: study of a retrofitting solution
No full textA research project on assessment and retrofitting of R/C frame structures is currently being developed under the research programme of the ICONS TMR-research network. This paper presents and discusses the preliminary experimental results from a 4-storey bare frame representative of the common practice of 40~50 years ago in most south European countries and devotes special attention to the study of a retrofitting solution based on bracing and rubber dissipaters, which intends to increase stiffness and damping reducing consequently the earthquake deformation demands.O estudo aqui apresentado concentra-se numa solução de reforço de um pórtico utilizando contraventamentos (k-bracing) com perfis de aço em conjunto com elementos elastoméricos de dissipação. Os resultados das análises não lineares da estrutura com e sem alvenaria e com reforço são apresentados e discutidos. Na segunda parte da comunicação apresentam-se os resultados experimentais já disponíveis e discute-se o problema da modelação recorrendo aos resultados experimentais e comparando os resultados obtidos com diferentes tipos de modelos
Maximum dynamic stress on bridges traversed by moving loads
No full textMost current research on dynamic effects due to traffic load on simply supported bridges focuses on the mid-span section of the bridge, since this location corresponds to the worst static bending moment. However, the maximum total moment allowing for dynamics, may differ considerably from the maximum moment at mid-span. This paper shows how the maximum can occur in a section relatively far from mid-span with a significant difference in magnitude.Other funderJournal websitewww.bridgesjournal.comEuropean 6th Framework Programme ARCHES (Assessment and Rehabilitation of Central European Highway Structures)Publisher requires the journal URL to appear on the record: www.bridgesjournal.com. Could use Description web link: Journal website as in http://hdl.handle.net/10197/2437? - AV 1/11/2010 au ke SB. 15/11/'1
STUDY OF THE SEXUAL MATURITY OF FEMALE BLUEFIN TUNA: PURIFICATION AND PARTIAL CHARACTERIZATION OF VITELLOGENIN AND ITS USE IN AN ENZYME-LINKED IMMUNOSORBENT ASSAY
No full textPlasma steroid levels of female bluefin tuna (BFT) Thunnus thynnus rose from c. 1.5 ng ml-1 during the quiescent period (March) to c. 7 ng ml-1 during the ripening period (May). Testosterone (T) increased further to c. 8 ng ml-1 during the pre-spawning period (June) while 17β-oestradiol (E2) began to decrease. In the post-spawning period (August) steroid levels decreased to <1 ng ml-1. Vitellogenin (Vtg) plasma levels seemed to follow changes in E2, showing an increase from the quiescent period to the ripening period of c. 18 mg ml-1, decreasing slightly before spawning, and then decreasing after spawning. The Vtg content in plasma showed a good correlation both with the plasma levels of E2 and T and with the percentage of vitellogenic oocytes at different periods of the reproductive cycle. Thus the ELISA could be taken as validated. Immunohistochemical staining of ovaries with anti BFT-Vtg serum demonstrated a high cross-reactivity with yolk proteins allowing the identification of vitellogenic oocytes
Non-Axisymmetric Effects on Long Liquid Bridges
No full textThe stability of long liquid bridges under non-axisymmetric disturbances like a microgravitational force acting perpendicular to the liquid bridge axis or a non-coaxiality of the disks is analyzed through an asymptotic method based on bifurcation techniques. Results obtained indicate that such non-axisymmetric effects are of higher order than those produced by axisymmetric perturbations
Feasibility Study of Strengthening Existing Single Span Steel Beam Concrete Deck Bridges; HR-214, June 1961
No full textIowa has the same problem that confronts most states in the United States: many bridges constructed more than 20 years ago either have deteriorated to the point that they are inadequate for original design loads or have been rendered inadequate by changes in design/maintenance standards or design loads. Inadequate bridges require either strengthening or posting for reduced loads. A sizeable number of single span, composite concrete deck - steel I beam bridges in Iowa currently cannot be rated to carry today's design loads. Various methods for strengthening the unsafe bridges have been proposed and some methods have been tried. No method appears to be as economical and promising as strengthening by post-tensioning of the steel beams. At the time this research study was begun, the feasibility of posttensioning existing composite bridges was unknown. As one would expect, the design of a bridge-strengthening scheme utilizing post-tensioning is
quite complex. The design involves composite construction stressed in an abnormal manner (possible tension in the deck slab), consideration of different sizes of exterior and interior beams, cover-plated beams already designed for maximum moment at midspan and at plate cut-off points, complex live load distribution, and distribution of post-tensioningforces and moments among the bridge beams. Although information is available on many of these topics, there is miminal information on several of them and no information available on the total design problem. This study, therefore, is an effort to gather some of the missing information, primarily through testing a half-size bridge model and
thus determining the feasibility of strengthening composite bridges by post-tensioning. Based on the results of this study, the authors anticipate that a second phase of the study will be undertaken and directed toward strengthening of one or more prototype bridges in Iowa
Comparative structural response of two steel bridges constructed 100 years apart
No full textThis paper presents a comparative numerical analysis of the structural behaviour and seismic performance of two existing steel bridges, the Infiernillo II Bridge and the Pinhao Bridge, one located in Mexico and the other in Portugal. The two bridges have similar general geometrical characteristics, but were constructed 100 years apart. Three-dimensional structural models of both bridges are developed and analysed for various load cases and several seismic conditions. The results of the comparative analysis between the two bridges are presented in terms of natural frequencies and corresponding vibration modes, maximum stresses in the structural elements and maximum displacements. The study is aimed at determining the influence of a 1 century period in material properties, transverse sections and expected behaviour of two quite similar bridges. In addition, the influence of the bearing conditions in the global response of the Pinhao Bridge was evaluated
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