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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Applications of VFIFE method to the Timoshenko beam analysis

Lee, Yen-huei 31 August 2009 (has links)
In this study, a vector form intrinsic finite element (VFIFE) is derived and applied to study both the static and dynamic responses of deep short beams under dynamic loadings. It is already known that the application of classical beam theory known as Euler¡¦s beam theory to beams with large ratio of D/L (depth/span larger than 1/4), a short-deep beam, may not necessarily obtain satisfactory results for the stress analysis of the beam. One of the main presumptions from the classical Euler¡¦s beam theory is that the plane of the cross-section remains plane and normal to the neutral axis of the beam after deformation. This presumption is no more true when the beam subject to loadings is a short-deep beam because the bending stress is no longer a dominant stress while the other secondary effects may have more severe influences on the mechanical behavior of the beam. This study by utilizing the vector form intrinsic finite element method (VFIFE) to derive a new element for the Timoshenko beam provides an alternative method for the analysis of a short-deep beam, particularly, subject to dynamic loadings. By taking the advantage of the VFIFE that is a time-saving scheme for the dynamic analysis, the element of Timoshenko-beam is derived along with the dynamic solution procedure. The motions in transverse direction and the rotation at each node of the beam are calculated and presented into figures. The results from numerical analysis are also verified with theoretical solution (exact analytical solution) and further compared to the results obtained from traditional finite element method.

Shear behaviour of ferrocement deep beams

Tian, Shichuan January 2013 (has links)
This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate shear resistance of flanged ferrocement beams with vertical mesh reinforcements in the web. Two groups of full-scale testing were conducted comprising of three I beams and four U beams. The I beams had the same geometry and reinforcement arrangements, but differed in the matrix strength or shear span to depth ratio. The U beams differed in web and flange thickness, reinforcement arrangements, matrix strength and shear span to depth ratio. The experimental data were used for validation of finite element models which had been developed using the ABAQUS software. The validated models were subsequently employed to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of matrix strength, shear span to depth ratio, cross sectional area, length of clear span, volume fraction of meshes and amount of rebar. The main conclusion from the experiments and parametric studies were: shear failure may occur only when the shear span to depth ratio is smaller than 1.5; the shear strength may increase by increasing the matrix strength, volume fraction of meshes, cross sectional area and amount of rebar. The main type of shear failure for I beams was diagonal splitting while for U beams it was shear flexural. Based on the results from the experimental and numerical studies, a shear design guide for ferrocement beams was developed. A set of empirical equations for the two different failure types and an improved strut-and-tie were proposed. By comparison with the procedures currently in practice, it is demonstrated that the methodology proposed in this thesis is likely to give much better predictions for shear capacity of flanged ferrocement beams.

Experimental and analytical investigation of reinforced concrete bridge pier caps with an externally bonded stainless steel system

Kim, Sung Hu 07 January 2016 (has links)
This research is aimed at examining experimentally and analytically the behavior of reinforced concrete bridge pier caps strengthened with externally bonded reinforcement. In the experimental study, nine full-scale reinforced concrete bridge pier caps were built, externally strengthened with stainless steel reinforcement, and ten tested to failure. Load, deflection, and strain measurements were collected and two potential failure mechanisms were identified. In the analytical part of this work, mechanics-based equations were developed for calculating the shear strength of these types of structural elements when a diagonal shear crack is formed under loading. In addition, a combined strut-and-tie/truss model is proposed for determining the strength of reinforced concrete bridge caps with externally bonded reinforcement. Results from both experimental and analytical studies were compared and design recommendations are made for future adoption in bridge and building codes and specifications.

A comparison of design using strut-and-tie modeling and deep beam method for transfer girders in building structures

Skibbe, Eric January 1900 (has links)
Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / Strut-and-Tie models are useful in designing reinforced concrete structures with discontinuity regions where linear stress distribution is not valid. Deep beams are typically short girders with a large point load or multiple point loads. These point loads, in conjunction with the depth and length of the members, contribute to a member with primarily discontinuity regions. ACI 318-08 Building Code Requirements for Structural Concrete provides a method for designing deep beams using either Strut-and-Tie models (STM) or Deep Beam Method (DBM). This report compares dimension requirements, concrete quantities, steel quantities, and constructability of the two methods through the design of three different deep beams. The three designs consider the same single span deep beam with varying height and loading patterns. The first design is a single span deep beam with a large point load at the center girder. The second design is the deep beam with the same large point load at a quarter point of the girder. The last design is the deep beam with half the load at the midpoint and the other half at the quarter point. These three designs allow consideration of different shear and STM model geometry and design considerations. Comparing the two different designs shows the shear or cracking control reinforcement reduces by an average 13% because the STM considers the extra shear capacity through arching action. The tension steel used for either flexure or the tension tie increases by an average of 16% from deep beam in STM design. This is due to STM taking shear force through tension in the tension reinforcement through arching action. The main advantage of the STM is the ability to decreased member depth without decreasing shear reinforcement spacing. If the member depth is not a concern in the design, the preferred method is DBM unless the designer is familiar with STMs due to the similarity of deep beam and regular beam design theory.

Neural network modelling of RC deep beam shear strength

Yang, Keun-Hyeok, Ashour, Ashraf, Song, J-K., Lee, E-T. January 2008 (has links)
Yes / A 9 x 18 x 1 feed-forward neural network (NN) model trained using a resilient back-propagation algorithm and early stopping technique is constructed to predict the shear strength of deep reinforced concrete beams. The input layer covering geometrical and material properties of deep beams has nine neurons, and the corresponding output is the shear strength. Training, validation and testing of the developed neural network have been achieved using a comprehensive database compiled from 362 simple and 71 continuous deep beam specimens. The shear strength predictions of deep beams obtained from the developed NN are in better agreement with test results than those determined from strut-and-tie models. The mean and standard deviation of the ratio between predicted capacities using the NN and measured shear capacities are 1.028 and 0.154, respectively, for simple deep beams, and 1.0 and 0.122, respectively, for continuous deep beams. In addition, the trends ascertained from parametric study using the developed NN have a consistent agreement with those observed in other experimental and analytical investigations.

ASR/DEF-damaged bent caps: shear tests and field implications

Deschenes, Dean Joseph 08 September 2010 (has links)
Over the last decade, a number of reinforced concrete bent caps within Houston, Texas have exhibited premature concrete damage (cracking, spalling and a loss of material strength) due to alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF). The alarming nature of the severe surface cracking prompted the Houston District of the Texas Department of Transportation to initiate an investigation into the structural implications of the premature concrete damage. Specifically, an interagency contract with the University of Texas at Austin charged engineers at Ferguson Structural Engineering Laboratory to: 1. Establish the time-dependent relationship between ASR/DEF deterioration and the shear capacity of affected bridge bent caps. 2. Develop practical recommendations for structural evaluation of in-service bridge bent caps affected by ASR and/or DEF. To accomplish these objectives, six large-scale bent cap specimens were fabricated within the laboratory. Four of the specimens (containing reactive concrete exposed to high curing temperatures) represented the most severe circumstances of deterioration found in the field. The remaining two specimens (non-reactive) provided a basis for the comparison of long-term structural performance. All of the specimens were subjected to a conditioning regimen meant to foster the development of realistic ASR/DEF-related damage. Resulting expansions were characterized over the course of the study through a carefully-planned monitoring program. Following a prolonged exposure period, three of the six bent cap specimens (representing undamaged, mild, and moderate levels of deterioration) were tested in shear. Observations made over the course of each test captured the service and ultimate load effects of ASR/DEF-induced deterioration. Six shear-critical spans were tested prior to this publication: three deep beam and three sectional shear tests. The remaining six shear spans (contained within the remaining three specimens) were retained to establish the effects of severe deterioration through future shear testing. Subsequent analysis of the expansion monitoring and shear testing data provided much needed insight into the performance and evaluation of ASR/DEF damaged bent structures. The results ultimately formed a strong technical basis for the preliminary assessment of a damaged bent structure within Houston, Texas. / text

Strut-and-tie modeling of reinforced concrete deep beams : experiments and design provisions

Tuchscherer, Robin Garrett 05 May 2015 (has links)
Bridge bents (deep beams) in the State of Texas have experienced diagonal cracking problems with increasing frequency. These field related issues, taken in combination with discrepancies that exist between design provisions for strut and tie modeling (STM), were the impetus for the funding of the current project. The overall objective of the project was to develop safe and consistent design guidelines in regard to both the strength and serviceability of deep beams. In order to accomplish this research objective and related tasks, a database of 868 deep beam tests was assembled from previous research. Inadvertently, many of the beams in this database were considerably smaller, did not contain sufficient information, or contained very little shear reinforcement. As a result, filtering criteria were used to remove 724 tests from the database. The criteria were chosen to consider only beams that represent bent caps designed in the field. In addition to the 144 tests that remained in the database, 34 tests were conducted as part of the current experimental program resulting in 178 total tests available for evaluation purposes. Two additional tests were conducted on beams without shear reinforcement, thus they did not meet the filtering criteria. However, the results from these tests provided valuable information regarding deep beam behavior. Beams that were fabricated and tested as part of the current experimental program ranged in size from, 36"x48", 21"x75", 21"x42", and 21"x23". These tests represent some of the largest deep beam shear tests ever conducted. STM details that were investigated included: (i) the influence that triaxial confinement of the load or support plate has on strength and serviceability performance; and (ii) the influence that multiple stirrup legs distributed across the web has on strength and serviceability performance. Based on the findings of the experimental and analytical program, a new strut-and-tie modeling procedure was proposed for the design of deep beam regions. The procedure is based on an explicitly defined single-panel truss model with non-hydrostatic nodes. An important aspect of the new STM design methodology is that it was comprehensively derived based on all the stress checks that constitute an STM design. Thus, the new method considers every facet of a STM design. The newly proposed STM procedure is simple, more accurate, and more conservative in comparison with the ACI 318-08 and AASHTO LRFD (2008) STM design provisions. As such, the implementation of the new design provisions into ACI 318 and AASHTO LRFD is recommended. / text

Shear cracking in inverted-T straddle bents

Garber, David Benjamin 29 September 2011 (has links)
Significant diagonal cracking in reinforced concrete inverted-T (IT) straddle bent caps has been reported throughout the State of Texas. Many of the distressed structures were recently constructed and have generally been in service for less than two decades. The unique nature of the problem prompted a closer look into the design and behavior of such structural components. A preliminary investigation highlighted outdated design requirements and a scarcity of experimental investigations pertaining to inverted-T bent caps. This research project (TxDOT Project 0-6416, Shear Cracking in Inverted-T Straddle Bents) aims to improve current understanding of the behavior of inverted-T caps, while providing updated design provisions. In order to develop strength and serviceability guidelines for inverted-T beams, an extensive experimental program was developed. This series of large scale tests was used to evaluate the strength and serviceability of IT deep beams in relation to the following parameters – shear span-to-depth (a/d) ratio, web reinforcement ratio, ledge height, ledge length, number of point loads, and member depth. This report focuses mainly on results from a first series of tests conducted within this experimental program. / text


LI, ZHERUI 23 March 2022 (has links)
京都大学 / 新制・課程博士 / 博士(農学) / 甲第23938号 / 農博第2487号 / 新制||農||1089(附属図書館) / 学位論文||R4||N5373(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 五十田 博, 教授 藤井 義久, 教授 梅村 研二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Aggregate interlock in lightweight concrete continuous deep beams

Yang, Keun-Hyeok, Ashour, Ashraf 09 1900 (has links)
yes / There are very few, if any, available experimental investigations on aggregate interlock capacity along diagonal cracks in lightweight concrete deep beams. As a result, the shear design provisions including the modification factor of ACI 318-08 and EC 2 for lightweight concrete continuous deep beams are generally developed and validated using normal weight simple deep beam specimens. This paper presents the testing of 12 continuous beams made of all-lightweight, sand-lightweight and normal weight concrete having maximum aggregate sizes of 4, 8, 13 and 19 mm. The load capacities of beams tested are compared with the predictions of strut-and-tie models recommended in ACI 318-08 and EC 2 provisions including the modification factor for lightweight concrete. The beam load capacity increased with the increase of maximum aggregate size, though the aggregate interlock contribution to the load capacity of lightweight concrete deep beams was less than that of normal weight concrete deep beams. It was also shown that the lightweight concrete modification factor in EC 2 is generally unconservative, while that in ACI 318-08 is conservative for all-lightweight concrete but turns to be unconservative for sand-lightweight concrete with a maximum aggregate size above 13 mm. The conservatism of the strut-and-tie models specified in ACI 318-08 and EC 2 decreased with the decrease of maximum aggregate size, and was less in lightweight concrete deep beams than in normal weight concrete deep beams.

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