Girder System Research Articles

방사광 가속기 PLS-II 저장링 거더 시스템 개발

The magnets and vacuum chambers, which are the main facilities of the Pohang light source are installed on the storage-ring girders. System safety and reliability should be taken into account for the precise operating of the main facilities, so vibration analysis is essential to do this. Static and seismic analyses were performed for the design of structure considering safety, and also frequency and response spectrum analyses were performed for the precise alignment. With these results, the effects of surrounding vibration were checked. This paper explains about the design and vibration analysis of girder systems.

SEISMIC BEHAVIOR OF STEEL MONORAIL BRIDGES UNDER TRAIN LOAD DURING STRONG EARTHQUAKES

This paper investigated dynamic responses of steel monorail bridges incorporating train-bridge interaction under strong earthquakes. Two types of steel monorail bridges were considered in the study: a conventional type with steel track-girder; an advanced type with composite track-girder and simplified lateral bracing system. During strong earthquakes, monorail train was assumed standing on the track-girder of monorail bridges. Observations through the analytical study showed that considering the monorail train as additional mass rather than a dynamic system in numerical modeling overestimated effect of the train load on seismic performance of monorail bridges. Earlier plastic deformations at the end bracing of the girder system absorbed seismic energy and reduced the stress at the pier base.

Efficient Prestressed Concrete-Steel Composite Girder for Medium-Span Bridges. I: System Description and Design

A new prestressed concrete-steel composite (PCSC) girder system is developed to provide a viable alternative for steel and prestressed concrete I-girders in bridges. The PCSC girder is composed of a lightweight W-shaped steel section with shear studs on its top and bottom flanges to achieve composite action with the pretensioned concrete bottom flange and the cast-in-place concrete deck. The PCSC girder is lightweight, economical, durable, and easy to fabricate. The proposed fabrication procedure is similar to those of prestressed concrete girders and does not need specialized equipment, materials, and forms. A service design procedure is proposed using the age-adjusted elasticity modulus method to evaluate the time-dependent stresses and strains in the PCSC girder caused by creep and shrinkage effects of concrete and relaxation of strands. The strength design method is proposed for the design of PCSC girders at prestress release. A design procedure is proposed to assist engineers to accomplish economic design and production of PCSC girders, and design examples are presented to illustrate the design procedure.

Development of performance assessment tools for a highway bridge resulting from controlled progressive monitoring

As highway bridges continue to deteriorate given the increased service life, increase in vehicle demand and exposure to harsh environmental climates, new methods of monitoring their in situ performance are of high priority. Damage within the structure can alter various load demand and capacity characteristics, affecting the overall integrity of the bridge. Discussed in this paper is the monitoring of a simple span bridge superstructure under various induced damage states. Strain measurements were recorded at the midspan and north abutment of each girder. Six levels of damage progression were implemented at a rocker bearing and various diaphragms to girder connections. Transverse load distribution factors (DFs) and neutral axis (NA) locations were measured for each damage case and evaluated against the baseline undamaged response. These measurements serve to provide a possible method of damage detection using load-testing parameters already employed by various transportation agencies. Next, a performance index (PI) is developed for this stringer/multi-girder bridge utilising the NA and DF response from the steel girder system and the allowable stress design load-rating data. The ratio of NA to DF was compared to the inventory load rating for each girder at each damaged state. The data were fitted with a power regression model to form the PI. Furthermore, a 95% prediction interval was used around the predicted response to capture all the data from the testing. The model was applied to the damaged structure as well as two additional stringer/multi-girder bridges. The objective of the PI is to complement existing qualitative assessment protocols with quantitative results for improving the condition assessment process.

Study on mechanical behaviors of FRP-to-steel adhesively-bonded joint under tensile loading

Due to various advantages of Fiber–Reinforced Polymer (FRP) decks, the FRP to steel composite girder system is being increasingly used in new bridge constructions as well as rehabilitation projects for old bridges. This paper focuses on the mechanical behavior and failure mode of the adhesively-bonded joins between FRP sandwich decks and steel girders. The adhesively-bonded joints were experimentally investigated under tensile loading. The average ultimate failure load of surface pretreated specimens was 17.62kN, which was 9.83% higher than that of un-pretreated specimens. Further comparison on failure modes confirmed that the surface pretreatment can improve the bonding quality between FRP composites and adhesive layer, and the failure load of the adhesive joint closely related to the FRP delamination area. Furthermore, a 3D numerical modeling was conducted using ABAQUS 6.8. The Finite Element Analysis (FEA) results were validated with experimental works focused on the deformational response of the adhesively bonded joints. The results of FEA highlight the three-dimensional nature of the stress distribution and stress concentrations at the interface between FRP sandwich deck and adhesive layer.

곡선 개구제형 거더의 곡률에 따른 매개변수 해석연구

A parametric study for varying the radii of curvature is performed with a curved tub girder bridge having three continuous spans. The bracing forces of top lateral bracings from the results of numerical equations are compared to those of 3-dimensional finite element analyses. New modifying factors applicable in computing the nominal member forces of top lateral bracings were suggested. The numerical equations were derived based on one girder system, and it is shown that the numerical equations exhibit some errors compared with 3D FEA results. The main reason for this phenomenon lies on the number of girders. The twin girder system has an external cross-beam between inner and outer girder. It also has larger lateral stiffness than the single girder system. Finally, the distributions by the torsion, bending, distortion, and lateral loading of the top lateral bracing forces were presented in this paper.

Performance of a scaled FRP deck-on-steel girder bridge model with partial degree of composite action

The applications of FRP decks have been increasingly implemented in the United States since the mid-1990s. Although extensive research has been conducted on stiffness and strength evaluations of various types of FRP decks, studies on FRP deck-on-steel girder systems are limited. The performance of the FRP deck-on-steel girder system depends substantially on the connectors used. Recently, a prototype shear connector was developed and its advantages were illustrated through both laboratory study and field applications, where partial degree of composite action could be achieved between the deck and stringers. This paper aims to study the effectiveness of the shear connector at bridge-system level, including the static and fatigue performance of the shear connector and the bridge system, the degree of composite action of the system; and more importantly, the influence of the partial degree of composite action on load distribution factor and effective flange width since no provision is provided in AASHTO Specifications. For this purpose, a 1:3 scaled FRP deck bridge model was tested, with an FRP sandwich honeycomb deck connected to steel girders using the prototype shear connector. The test program consisted of three phases: Phase I and Phase II included static and fatigue load tests on the scaled bridge model. In Phase III, a T-section was cut-out from the bridge model and then loaded under three-point bending until failure. A Finite Element model was constructed to simulate the tests. It was shown that the shear connection was able to provide partial composite action of about 25%, and sustain a cyclic fatigue loading equivalent to 75year bridge service life span. It is shown that AASHTO Specifications can still be applicable for load distribution factor, while the effective flange width needs to be re-defined for bridge-system with partial degree of composite action. The findings from this paper can be used for design purposes.

Effective Flange Width for Honeycomb FRP Sandwich Bridge Deck‐on‐Steel Girder System with a Mechanical Shear Connector Considering Degrees of Composite Action

Effective Flange Width for Honeycomb FRP Sandwich Bridge Deck‐on‐Steel Girder System with a Mechanical Shear Connector Considering Degrees of Composite Action

Numerical analysis of pultruded GFRP box girders supporting adhesively-bonded concrete deck in flexure

This paper presents the modeling of pultruded glass fiber reinforced polymer (GFRP) box girders consisting of built-up hat-shape sections and flat plates. The study addresses the effect of a thin concrete deck adhesively bonded to the top GFRP plate on flexural performance, as well as the behavior under positive and negative bending that simulates continuous girders. A three-dimensional finite element (FE) approach is proposed to predict the behavior of the GFRP system, including experimental validation. The efficacy of the girders is compared with other metallic box girders: carbon steel and corrosion-resistant metals, namely, stainless steel and aluminum. Failure is generally due to debonding of the concrete deck, and as such, the ultimate strength is not affected much by the girder material used. The study examines the single girder behavior as well as girder-group systems, to assess load distribution. It is shown that the AASHTO LRFD approach for load distribution can reasonably be used for the proposed girder systems. Design recommendations as to material selection are addressed to better use the girder system.

Determining the Characteristics of Composite Structure Laminae by Optical 3D Measurement of Deformation with Numerical Analysis

Experimental determination of the elastic constants of orthotropic composite materials and their bearing capacity (strength) for furniture intended for sitting, and numerical verification of the experiment results by analysing with the final elements, was performed on the basis of the theory of elasticity of orthotropic and anisotropic composite materials. The requisite and sufficient material constants were determined in the experiments: moduli of elasticity and Poisson’s coefficients (longitudinal and tangential) and skate modulus for plain stress. These constants, calculated by 3D measurements of deformation, are sufficient for determining the constitutive matrix of the lamina, and for reducing stiffness of the composite irrespective of the thickness of the layers, fibre orientation and choice of material. Experiments were conducted for the stiffness, shear and flexing of uniformly and complexly layered beech veneer sheets, while for new materials experiments for stiffness and shear in a uniform orientation were sufficient. Analysis of stiffness and deformations were conducted layer by layer, as well as by reduced volume stiffness for multi-layered orthotropic shells of chair systems by a method of final elements by application of a composite final element, where combined reduced membrane matrices and flexing matrices are used. Numerical verification of the experiments, including systems of furniture intended for sitting – chairs – was conducted using the KOMIPS software system, which contains in its library a composite final element of the sheet. Experiments with chairs were performed with the aim of determining the stiffness of such systems, and they were confirmed by analytical results and measurement of the real movements on selected models. The results of research provide the design, re-design, construction and determination of the dimensions of not just chairs, but also of any other girder or surface system based on laminates.

Design improvements and tests of a laser positioning system for the Taiwan Photon Source girder system

A precise laser positioning system had been preliminarily developed for the girder system of the Taiwan Photon Source. This laser positioning system, a part of a girder auto-alignment scheme, will be installed on the girders located at both sides of each straight section of the storage ring. The system is composed of a laser and four sets of a position sensing device (PSD). The laser, held on one girder, propagates 13 m along the girder and plays the role of a reference line of girders of the straight section. Based on the laser linear characteristics, the other girder can be adjusted and aligned by a cam mover according to PSD data. To achieve superior precision, the whole laser positioning system should be constructed stably. After making some improvements to eliminate the unstable terms, the precision of the laser positioning system can achieve 2 µm at 13 m propagating distance every 4 h.

Survey and alignment design for the Taiwan photon source

Taiwan Photon Source is a new 3-GeV ring with characteristics of great brightness and small emittance, at present under construction at National Synchrotron Radiation Research Center (NSRRC) site in Taiwan and due to be commissioned in 2013. The positioning of the magnets is highly sensitive to alignment errors, and the entire building will be constructed half underground at depth 12 m relative to Taiwan Light Source (TLS) for stability reasons; for these reasons the survey and alignment work is confined and difficult. To position magnets precisely and quickly, a highly accurate auto-tuning girder system combined with a survey network was designed to accomplish the alignment tasks. The survey network includes a preliminary Global Positioning System (GPS) network and a laser-tracking network. The position data from the survey network define a basis for the system of motorized girders to auto-tune and improve the accuracy. The detailed survey and alignment design, simulation and preliminary data are described in this paper.

Installation and diagnostics of a girder-system mockup for Taiwan Photon Source

Taiwan Photon Source (TPS), a new 3 GeV synchrotron ring, is under construction at National Synchrotron Radiation Research Center (NSRRC). To discover problems of design, manufacture and installation, a mockup of 1/24 section (one cell) of TPS was installed at NSRRC. A modified, precise, six-axis, prototype girder system of this mockup composed of three girders was fabricated. We discuss both the installation of the girder system and its diagnostics, and present the results including measurement of the dimensions of the components of the girder system and the vibration tests.

Free vibration characteristics of horizontally curved composite plate girder bridges

This paper is concerned with free vibration characteristics and natural frequency of horizontally curved composite plate girder bridges. Three-dimensional finite element models are developed for the girders using the software package LUSAS and analyses carried out on the models. The validity of the finite element models is first established through comparison with the corresponding results published by other researchers. Studies are then carried out to investigate the effects of total number of girders, number of cross-frames and curvature on the free vibration response of horizontally curved composite plate girder bridges. The results confirm the fact that bending modes are always coupled with torsional modes for horizontally curved bridge girder systems. The results show that the first bending mode is influenced by composite action between the concrete deck and steel beam at low subtended angle but, on the girders with larger subtended angle at the centre of curvature such influence is non-existence. The increase in the number of girders results in higher natural frequency but at a decreasing rate. The in-plane modes viz. longitudinal and arching modes are significantly influenced by composite action and number of girders. If no composite action is taken into account the number of girders has no significant effect for the in-plane modes.

Construction of the Cable-Stayed Bridge in the Commercial Port of Venice, Italy

This paper illustrates the final design development and the construction engineering of a cable-stayed bridge of recent construction, which crosses the commercial harbour of Venice.The bridge presents a curved deck, steel-concrete composite structure, single layer of stay cables displayed on a conical layout, and a slanted single lateral mast.The construction method was based on the erection of the deck structure by floating and lifting of large macro-elements. The girder system was designed according to the concept of deck structure protected by a stainless steel enclosure.

Effects of Cross-Frame on Stability of Double I-Girder System under Erection

Double-girder systems investigated here consist of two steel I-shaped straight girders connected by intermediate cross-frames. In the erection stage, loading on the girder system, consisting mainly of girder self-weight, may not be significant. However, the concrete deck typically is not present to provide continuous lateral support to girder flanges, and there may be fewer cross-frames than in the service condition, resulting in fewer discrete lateral constraints to girder flanges and torsional constraints to girder sections. Such conditions could contribute to significant lowering of lateral torsional buckling capacity of the girder system compared with the service condition, and the girder system may become unstable during construction if the girder span is too long or if cross-frames do not provide enough discrete lateral support. Thus, it is important to investigate the effects of cross-frames on the stability of double-girder systems during construction. The AASHTO load and resistance factor design code has no specific requirements for maximum allowable spacing of cross-frames. To identify the dominant parameters and quantify the effects of cross-frames on double-girder system stability, finite element analyses were conducted to investigate the effects of the area of the cross-frame braces and cross-frame spacing on lateral torsional buckling capacity of double-girder systems under self-weight. The area of cross-frame members had negligible effects, but cross-frame spacing above a certain value affects system capacity. A method is presented to determine maximum cross-frame spacing (i.e., minimum number of cross-frames) for double-girder systems during erection. The goal is to achieve construction safety and labor reduction at the same time.

Characterization of High Early-Strength, Self-Consolidating Concrete for Design of Pretensioned Bridge Elements

Self-consolidating concrete (SCC) is an innovative construction material that can be placed into forms without mechanical vibration. Precast, prestressed concrete plants require that the concrete used to fabricate their structural members attain high early strength. High early-strength SCC could provide significant value for precast plants. However, the high early-strength SCC mixture constituents, proportions, and construction may affect the hardened properties, and SCC may not provide the same performance as conventional concrete. SCC and conventional concrete mixture proportions designed for precast, prestressed bridge elements were evaluated to characterize the associated mechanical properties, shear characteristics, bond characteristics, and creep. To assess the applicability of SCC in prestressed girder systems, four full-scale girder–deck systems containing conventional concrete and SCC precast girders were fabricated and tested. Results from this research indicate that the AASHTO Load and Resistance Factor Design Specifications can be used to estimate the mechanical properties of high early-strength SCC. With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for SCC girders with a compressive strength greater than 10 ksi (69 MPa). Bridge girder–deck systems containing relatively small (Texas Type A) girders containing high early-strength SCC exhibited similar flexural performance as bridge girder–deck systems with girders containing conventional concrete. Results indicate that the AASHTO equations for computing the nominal moment capacity, strand transfer length, and strand development length may be used for SCC girder–deck systems similar to those tested in this study.

Design–Build Replacement of US-90 Bridge over Bay St. Louis, Mississippi

As part of the rebuilding efforts after Hurricane Katrina, the Mississippi Department of Transportation awarded a design–build contract for the replacement of the 2.1-mi-long US-90 bridge spanning Bay St. Louis. With a January 25, 2006, start date, the deadline for opening two lanes of traffic was May 16, 2007, followed by a February 15, 2008, deadline for opening the entire bridge. The bridge was constructed as two separate structures except for the navigation unit, where the deck and substructure are continuous between the eastbound and westbound structures. To allow for such an aggressive construction schedule, several concepts were used. Plans were delivered in stages to allow construction to proceed before the final submittal. The use of precast components including girders, piles, and capbeams was maximized. Pile bents to a height of 75 ft above fixity were used, with no battered piles. The pile and girder sections were varied to allow for utilization of more precast fabricators. Precast, prestressed piles, ranging in length from 50 to 164 ft, form the bridge foundations of the pile bents (24- and 36-in. piles) and waterline footings (30-in. piles). Typical superstructure elements consist of BT-78 girders (maximum span of 154 ft) and AASHTO Type IV girders (maximum span of 112 ft). A spliced haunch girder system with a 250-tt main span and 200-ft end spans was implemented at the navigational channel to satisfy the vertical and horizontal clearances.

Behavior of Hollow Tubular-Flange Girder Systems for Curved Bridges

This paper describes research results for an innovative curved highway bridge girder system, which uses I-shaped steel girders with hollow rectangular tubes as flanges. The increased torsional stiffness provided by the tubular flanges dramatically improves the structural behavior of the curved girders, resulting in substantially reduced deflection, cross section rotation, and stress compared to conventional curved I-shaped steel plate girders. In this paper, finite-element (FE) models for systems of curved tubular-flange girders are described. The models consider material inelasticity, second-order effects, initial geometric imperfection, and residual stresses. The girder systems are comprised of curved hollow tubular-flange girders (CHTFGs), cross frames between the CHTFGs, and a concrete deck. A parametric study is performed using the FE models to study the effects of web stiffeners, tube diaphragms, geometric imperfection, and residual stresses on the load capacity of three-girder systems with CHTFGs. Then, the results for the CHTFG systems are compared with results for corresponding conventional curved I-girder systems. The effects of the curvature, cross section dimensions, number of cross frames, and a concrete deck are investigated. The results indicate that the CHTFG systems are more structurally efficient than the corresponding curved I-girder systems.

Framework for Multiobjective Optimization of Launching Girder Bridges

A framework is presented for optimizing the construction of decks of bridges using launching girder systems. The framework assists contractors in performing a time-cost trade-off analysis to optimize the use of resources. The proposed framework consists of three main components which interact in a cyclic manner. These components are simulation, optimization, and reporting modules. Processes and tasks of launching girder systems are described in order to illustrate the mechanism of the simulation module which utilizes STROBOSCOPE as a general purpose simulation language. The developments made in the optimization module are extensively detailed. The optimization module uses ant colony optimization and it accounts for seven optimization variables; location of casting yard, time lag, number of casting forms, number of preparation platform, curing method, number of yard reinforcement crews, and number of stressing crews. Two optimization approaches are coded in the optimization module in two algorithms (ant colony multiobjective optimization I and II) to carry out multiobjective optimization. These are function-transformation and modified distance approaches. A numerical example is presented to illustrate the practical use of the developed framework.