scholarly journals Protective and Blast Resistive Design of Posttensioned Box Girders Using Computational Geometry

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Majid Aleyaasin
Keyword(s):  
Computational Geometry ◽  
Cross Section ◽  
Cross Sections ◽  
Computational Algorithm ◽  
Optimal Shape ◽  
Box Girders ◽  
Cross Point ◽  
Box Girder ◽  
Numerical Example ◽  
Duct Geometry

The optimal tendon profile and its associated duct geometry for posttensioned box girders are investigated. A computational algorithm has been developed to determine an ideal shape for the tendon and duct. The algorithm is based on a diagonal cross point in the Magnel quadrilateral and uses computational geometry instead of graphical drawing. Thereafter, an ideal parabolic and linear tendon profiles can be calculated from which the covering duct could be shaped. To check the optimality of the results, an automatic examination of Magnel diagrams in various cross sections is incorporated in the algorithm. This enables a unique prestress level to be selected that suits all sections. Then, the mideccentricity of the two crossing points with a common prestress line is chosen as a design eccentricity in each cross section. The optimal duct shape is determined based on such automatic inspections. In a numerical example, the linear, parabolic, and optimal duct geometries are compared and drawn. It is concluded that both linear and parabolic duct shapes can be very close to an optimal shape. In a numerical example, an optimal, box girder with linear open access-type tendons is designed that can withstand extra blast load when explosion occurs.

scholarly journals Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Marya Bagherifaez ◽  
Arash Behnia ◽  
Abeer Aqeel Majeed ◽  
Chai Hwa Kian
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Cross Sections ◽  
Analysis Data ◽  
Damage Localization ◽  
Box Girders ◽  
Box Girder ◽  
Value Analysis ◽  
Damage Propagation ◽  
Torsion Fracture

Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothedb-value analysis.

Estimation of Ultimate Longitudinal Bending Moment of Ships and Box Girders

1996 ◽  
Vol 40 (03) ◽  
pp. 244-257 ◽  
Author(s):  
M. K. Rahman ◽  
M. Chowdhury
Keyword(s):  
Cross Section ◽  
Bending Moment ◽  
Fortran Program ◽  
Box Girders ◽  
Limit States ◽  
Box Girder ◽  
Stiffened Panels ◽  
Complete Procedure ◽  
Longitudinal Bending ◽  
Collapse Behavior

The paper describes a methodology of computing the ultimate value of the longitudinal bending moment at any cross section of a ship or box girder. The cross section has been discretized into stiffened panels (one stiffener with its associated effective plating). The limit states for these panels, both tensile and compressive, are modeled in an appropriate manner. Since the ultimate strength of the girder section is largely governed by the behavior of the panels under compression, the authors have paid special attention in modeling the collapse as well as post-collapse behavior of these panels. A new stress-strain relationship is also introduced. The complete procedure has been coded into a FORTRAN program and tested against a number of box girder models and an actual ship for which the true behavior was known. The results obtained from the proposed program appear to be quite satisfactory. Good correlation was also found when compared with the results obtained by more complex and rigorous analytical methods.

Fatigue Evaluation of Flat Steel Box Girders with Closed Stiffeners of Large-Span Suspension Bridges under Different Heavy Trucks

2011 ◽  
Vol 147 ◽  
pp. 157-160 ◽  
Author(s):  
Yong Zeng ◽  
Hong Mei Tan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cross Section ◽  
Suspension Bridges ◽  
Box Girders ◽  
Element Analysis ◽  
Box Girder ◽  
Fatigue Assessment ◽  
Steel Box Girder ◽  
Flat Steel

Due to its outstanding aerodynamic shape and light weight, the trapezoidal cross-section flat steel box girder with orthotropic decks and thin-walled longitudinal stiffeners of trapezoidal cross section are widely used in long-span suspension bridges in the world. However, because of the geometrical characteristics and the relative flexibility of their components, these structures may be quite susceptible to traffic loadings that fatigue cracks tend to appear in these structures. In this paper, Jiangyin Bridge is used as a case study to investigate the fatigue performance of the steel girders of suspension bridge Jiangyin Bridge is the second longest bridge in China, which has the main span of 1385m. The stress analysis of steel box girders is firstly carried out based on the analysis of fatigue life. Fatigue assessment method is proposed on the basis of in-situ measurement data combined with finite element analysis. A complete fatigue assessment is made in this paper. Key words: flat steel box girder; orthotropic decks; finite element analysis; fatigue assessment

Research on Skew Coefficient for Stresses of Skewly Supported Three-Span Continuous Box Girders

2014 ◽  
Vol 587-589 ◽  
pp. 1483-1487
Author(s):  
Liang Liu
Keyword(s):  
Cross Section ◽  
Shell Element ◽  
Skew Angle ◽  
Box Girders ◽  
Concentrated Load ◽  
Box Girder ◽  
Lag Effect ◽  
The Cross ◽  
Skew Angles ◽  
Bottom Slab

Skewly supported continuous box girders have special mechanical properties compared with common continuous box girders. Skew coefficient for stress of skewly supported three-span continuous box girder is introduced to reflect the decrease degree of the normal stresses at the cross section of the middle span of the box girder. The finite element models of the skewly supported three-span continuous box girders with different skew angles are established by applying the SHELL63 shell element in software ANSYS. The variation of the skew coefficient for stress at different calculation points of middle span cross section under concentrated load is analyzed and the corresponding influence law is revealed. Research results show that the skew coefficient for stress of top slab is different from that of bottom slab at the cross section of the skewly supported three-span continuous box girder. The skew coefficient for stress of top slab is smaller than that of bottom slab. Skew coefficient for stress decreases with the increasing of the skew angle. Because of the shear lag effect, the minimal skew coefficient for stress of flanges occurs at the free tip of cantilever slab while the maximal skew coefficient occurs at the intersection of web and flange slabs.

scholarly journals Effect of Construction Method on Shear Lag in Prestressed Concrete Box Girders

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Shi-Jun Zhou
Keyword(s):  
Cross Sections ◽  
Prestressed Concrete ◽  
Construction Process ◽  
Shear Lag ◽  
Box Girders ◽  
Box Girder ◽  
Construction Methods ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges ◽  
Girder Bridge

Most of the previous researches conducted on shear lag of box girders were only concerned about simple types of structures, such as simply supported and cantilever beams. The structural systems concerned in these previous researches were considered as determined and unchangeable. In this paper, a finite element method considering shear lag and creep of concrete was presented to analyze the effect of dynamic construction process on shear lag in different types of concrete box-girder bridges. The shear lag effect of the three types of a two-span continuous concrete beam classified by construction methods was analyzed in detail according to construction process. Also, a three-span prestressed concrete box-girder bridge was analyzed according to the actual construction process. The shear lag coefficients and stresses on cross sections along the beam including shear lag were obtained. The different construction methods, the changes of structural system with the construction process, the changes of loading and boundary conditions with the construction process and time, the prestressing, and creep were all imitated in the calculations. From comparisons between the results for beams using different construction methods, useful conclusions were made.

scholarly journals Closed form solution in buckling optimization problem of twisted rod

2021 ◽  
Author(s):  
Vladimir Kobelev
Keyword(s):  
Closed Form ◽  
Cross Section ◽  
Cross Sections ◽  
Optimization Problem ◽  
Closed Form Solution ◽  
Form Solution ◽  
Optimal Shape ◽  
Actual Problem ◽  
The Cross ◽  
Simply Connected

Abstract The applications of this method for stability problems are illustrated in this manuscript. In the context of twisted rods, the counterpart for Euler’s buckling problem is Greenhill's problem, which studies the forming of a loop in an elastic bar under torsion (Greenhill, 1883). We search the optimal shape of the rod along its axis. A priori form of the cross-section remains unknown. For the solution of the actual problem the stability equations take into account all possible convex, simply connected shapes of the cross-section. Thus, we drop the assumption about the equality of principle moments of inertia for the cross-section. The cross-sections are similar geometric figures related by a homothetic transformation with respect to a homothetic center on the axis of the rod and vary along its axis. The distribution of material along the length of a twisted rod is optimized so that the rod is of the constant volume T and will support the maximal moment without spatial buckling. The cross section that delivers the maximum or the minimum for the critical eigenvalue must be determined among all convex, simply connected domains. We demonstrate at the beginning the validity of static Euler’s approach for simply supported rod (hinged), twisted by the conservative moment. The applied method for integration of the optimization criteria delivers different length and volumes of the optimal twisted rods. Instead of the seeking for the twisted rods of the fixed length and volume, we directly compare the twisted rods with the different lengths and cross-sections using the invariant factors. The solution of optimization problem for twisted rod is stated in closed form in terms of the higher transcendental functions. In the torsion stability problem, the optimal shape of cross-section is the equilateral triangle.

Analysis of Eccentric Load Causing Torsion Effects of Variable Cross-Section Continuous Box Girder during Cantilevered Casting

2012 ◽  
Vol 446-449 ◽  
pp. 1194-1198
Author(s):  
Min Xiang ◽  
Cong Juan Yang
Keyword(s):  
Cross Section ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Construction Process ◽  
Analysis Model ◽  
Box Girders ◽  
Eccentric Load ◽  
Box Girder ◽  
Continuous Beam Bridge ◽  
Beam Bridge

The construction with hanging basket eccentric loading was studied for the cantilever casting of a 32m +48 m +32 m continuous box girder. The calculation of center deflecting angles of cantilever box girders with variable cross-section due to pure torsion was derived, and correspondingly a program was developed to calculate this formula. An analysis model of cantilever casting continuous beam bridge with hanging basket eccentric loading was established based on finite elements software, and the shear stress, the longitudinal normal stress and the combined stress of different section were analyzed under different construction process. The torsional effect due to hanging basket eccentric loading was studied and the results are helpful to guide the construction in practice.

Transverse Shearing Strain Energy Calculation of Single Cell Box Girder

2010 ◽  
Vol 163-167 ◽  
pp. 1044-1052
Author(s):  
Jia Jian Zhao ◽  
De Min Wei
Keyword(s):  
Single Cell ◽  
Cross Section ◽  
Cross Sections ◽  
Calculation Method ◽  
Strain Energy ◽  
Energy Calculation ◽  
Box Girder ◽  
Calculation Results ◽  
Side Walls ◽  
Shearing Strain

Both the increasingly-thin walls of box girder cross-sections and the super-loads from trains or track vehicles make the behavior research on diaphragms and side walls become particularly important. According to the deformation of single cell box girder cross-section, the displacement parameters were designed, and the displacement modes of cross-section distortion angles were deduced. The schematic plans of diaphragms and side walls were simulated by rigid frames or plates. Both the shearing strain energy and the shearing stiffness of diaphragms and side walls were deduced on the basis of the principles of mechanics and finite element. The results show that the shearing strain energy increases with the displacement by a power function. And the method calculation results are close to the commercial FE software calculation results, which show that the calculation method of single cell box girder presented in this paper is correct and reliable. The calculation method is simpler than the commercial FE software calculation method. In the calculation method, whether diaphragms and side walls are calculated separately or calculated as some parts of the box girder or the vehicle - bridge system, the calculation precision of diaphragms and side walls remains unchanged.

Evaluating Section Loss in Corroded Steel Strands

2019 ◽  
Author(s):  
Yeun Chul Park ◽  
Chul-Hwan Yoo ◽  
Ho-Kyung Kim
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Box Girder ◽  
Corrosion Depth ◽  
Steel Wires ◽  
Corrosion Evaluation ◽  
Steel Strand ◽  
Corrosion Model ◽  
Typical Shape ◽  
Girder Bridge

<p>Since corrosion in prestressing tendon reduces the cross-section and strength of steel strand, it is critical for the safety of structures. Corrosion model in steel wires and a technique for evaluating section loss in steel strands were developed based on the measurement of corroded strands obtained from a concrete box girder bridge in Korea. The strands were corroded due to chloride and moisture attack. Cross-sections of corroded wires were measured for section loss, corrosion depth and perimeter. The measurement showed that corrosion rapidly progressed along the perimeter in earlier stage of corrosion, so that the shapes of remaining cross-sections were convex rather than concave which is typical shape of pitting corrosion. Evaluation of section loss in corroded steel strands were conducted using the wire corrosion model. If a strand can be approached from any direction around the strand, section loss could be evaluated within 5% of error.</p>

The significance of warping torsion in the design of straight concrete box-girder bridges

1988 ◽  
Vol 15 (5) ◽  
pp. 879-889 ◽  
Author(s):  
Peter Waldron
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Design Stage ◽  
Assessment Procedure ◽  
Box Girder Bridges ◽  
Cross Sectional ◽  
Box Girder ◽  
Girder Bridges ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges

Out-of-plane warping, resulting from torsional loading, is an important feature of box-girder bridges of thin-walled cross section. This may be of some consequence in girders where warping is restrained, since it may alter the level of stress both around the cross section and along the entire length of the beam. It is well known that some girders with very thin walls are not susceptible to warping, whereas others, with thicker walls, warp significantly when twisted. It is shown that the degree of warping is not governed by wall thickness alone; cross-sectional geometry, girder configuration, and loading must also be considered. The significance of these various factors in estimating the effects of warping restraint is assessed. In many cases this will permit the selection of box-girder cross sections at the conceptual design stage for which torsional warping effects are negligible. A simply supported concrete box girder is used as an example to demonstrate the importance of cross-sectional geometry, girder configuration, and loading in the assessment procedure. This is extended to the more general case of multi-span girders subjected to realistic patterns of loading. Key words: torsion, warping, box-girders, bridges, concrete, design.

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