Browsing by Subject "Reinforced concrete"
Now showing 1 - 19 of 19
Results Per Page
Sort Options
Item Alternate vertical steel reinforcement in prestressed concrete beams(Texas Tech University, 2001-08) Cedeno-Rosete, RafaelThe Texas Department of Transportation (TxDOT) widely uses prestressed concrete I-beams for constructing bridges. Currently, TxDOT prestressed concrete I-beam standard permits the substitution of an equal area of Welded Wire Fabric (WWF) for the traditional standard steel bars used as the vertical steel reinforcement. However, no details are provided to insure the standardization of this allowed substitution. The common practice is to simply make a one-for-one substitution using deformed wire for each conventional deformed bar. A research project was conducted at Texas Tech University (TTU) to study the behavior of the WWF as a vertical steel reinforcement, specifically the anchorage capacity of the WWF. In addition, alternate vertical steel reinforcement details were proposed using a simplified steel area and an equivalent strength steel area of WWF. The results of this study are reported in this work. WWF consists in deformed wire bars in the transverse direction and plain wires in the longitudinal direction welded at each intersection using an electrical resistance welding procedure to form flat sheets of WWF. These flat sheets of WWF are bent into the desired shapes and placed into position as units. The vertical shear reinforcement must be properly anchored at its ends in order to be capable of developing its fiiU shear design strength. Two longitudinal plain wires welded to each vertical leg on the WWF detail and spaced vertically two inches apart are provided to develop this anchorage behavior. This detail requires that the two longitudinal wires and their welds be capable of properly anchoring the vertical wires. This two cross-wire anchoring detail in the WWF has been used in several other similar applications. However, there are some differences between these similar applications and Texas prestressed I-beam details. One of the main objectives of this research work has been to study the effectiveness of this anchorage detail. The current TxDOT vertical reinforcement detail for I-beams at the ends consists of bars with diameter 1/2 inches (No. 4) spaced at 4 inches, called "R" bars, and bars with diameter 5/8 inches (No. 5) spaced at 4 inches, named "S" bars. Both of these sets of bars must be Grade 60. This project also studied a simplified WWF alternative of reinforcement consisting of using an equivalent wire diameter providing the same steel area. This simplified approach has the advantage of reducing the production cost of the WWF cages, due to the fact that only one wire diameter is needed to be fed during the production process. In addition to this alternative vertical steel reinforcement, another reinforcement proposal was studied. An equal strength substitution was proposed using Grade 80 wires with a smaller area in such a way that the total strength developed by the vertical WWF reinforcement will be the same of the traditional reinforcement using No. 5 and No. 4 bars of Grade 60. This change in policy would allow the use of the higher yield strength common in WWF material, leading to reduced areas of steel and an associated reduction in cost. Finally, with the onset of High Performance Concrete, the strength of concrete possibly used in the TxDOT I-beams has increased from 5,000 psi to 10,000 psL Because of this shift, concrete strength was also another study parameter consider in this research. In order to study the performance of the WWF steel substitution in the particular use of vertical steel reinforcement in the TxDOT I-beams, 14 full-scale tests were conducted at the Texas Tech University (TTU) structural testing laboratory. The concrete strength ranges used were 5,000-7,000 psi for normal concrete strength and 10,000-12,000 psi for high strength concrete. The beams were tested to observe their performance failure load. The results of this study were used to state recommendations about the current TxDOT policies of using WWF as vertical shear reinforcement.Item Analysis of reinforced concrete floor slabs for storm shelters(Texas Tech University, 2005-08) Galani, Navin K.; Kiesling, Ernst W.; Budek, AndrewOn-grade concrete floor slabs are very important structural components of above ground storm shelters. A structurally sound floor slab is required to ensure sufficient support for the shelter during an extreme wind event. In this research an analytical approach has been followed to understand the flexural behavior of the floor slab during an F5-tornado. The slab is assumed to support a storm shelter (8’x 4’x 8’ and 8’x 8’x 8’) that is subjected to wind having 250 mph 3-sec gust ground level wind speed. ALGOR finite element analysis package was used to model the concrete floor slab and simulate the required field conditions. Moment-carrying capacity of uncracked reinforced concrete slab and its reserve flexural strength after cracking were used to monitor the stress levels in the slab. Based on this analysis, design provisions (slab thickness and steel reinforcement) are suggested for the selected slab-shelter configurations. Also, the slab material at the slab-shelter connection was checked for strength against the maximum pullout force transferred by the anchor bolt. It can be concluded that this analytical procedure provides a useful tool in designing floor slabs for storm shelters.Item Analysis of the shear behavior of prestressed concrete spliced girders(2016-08) Al-Tarafany, Dhiaa Mustafa T.; Jirsa, J. O. (James Otis); Bayrak, Oguzhan; Tassoulas, John; Hrynyk, Trevor; Ghannoum, Wassim; Wheat, HarovelImplementation of the spliced girder technology in bridges has been growing in recent years. Increased girder lengths can now be realized by splicing shorter precast segments to produce a long span. The research conducted in this dissertation is focused on an evaluation of spliced girders using a three dimensional finite element analysis. The project consisted of a series of tests that were conducted in two phases. In Phase I, the effect of post-tensioning ducts on the shear behavior and strength of prestressed concrete girders was evaluated. In Phase II, the focus was on the behavior of cast-in-place splice regions between precast segments. Since a limited number of full scale beams could be tested, a three-dimensional advanced finite element program is an effective alternative to expensive tests. The parameters considered were grout to girder concrete strength ratio, splice to girder concrete strength ratio, concrete shear key detailing, coupler diameter, duct to web width ratio, shear span to depth ratio, and concrete shrinkage losses. The findings are described in detail. Using the experimental and analytical results, it was found that the grout to concrete strength ratio for grouted ducts should not to be less than 0.3. The effect of increasing the duct diameter to web width ratio from 0.43 to 0.57 was minimal. Splice to girder concrete strength ratio should be greater than 0.6. The addition of a shear key had no effect on the shear capacity of the girder. The coupler diameter in the splice region had no effect on the behavior of the spliced girder for coupler diameter to web width ratio up to 0.55. Including concrete shrinkage in the analysis slightly improved the correlation with observed response.Item Behavior of slender beams without stirrups: effects of load distribution and member depth(2015-12) Klein, Joseph Robert; Bayrak, Oguzhan, 1969-; Hrynyk, Trevor DThough uniform loading is common in structures, the vast majority of all shear strength tests on slender reinforced concrete members without stirrups have been performed using concentrated loading. Furthermore, the uniform load tests that have been conducted typically involve members with smaller specimen depths (d) and larger reinforcement ratios (ρ) than are commonly used in practice. Previous studies usually agree that a noticeable increase in shear strength can be expected when a specimen is subjected to uniform loading as opposed to concentrated loading. Six shear tests were performed on four slender beams without stirrups at The University of Texas at Austin. Two of the specimens had approximately double the effective depth (d) as the other two. For a given depth, two concentrated load tests were carried out on either end of one specimen, and one uniform load test was carried out on the second specimen. Thus, four reinforced concrete beams were used to perform a total of four concentrated load tests and two uniform load tests, with the objective of determining the influence of load distribution as member depth (d) increases. To ensure that a direct comparison could be made between each load distribution, the ratio between maximum bending moment and maximum shear force was maintained for all tests. Additionally, to provide consistency with typical design practice, the reinforcement ratio (ρ) was selected to match that of a typical beam. The experimental results presented an influence of load distribution opposite to that of previous studies, with a range of increase in shear strength at first diagonal cracking of concentrated load tests of -16 to 50 percent, with an average increase of 18 percent, over uniform load tests. Additionally, the tests with smaller effective depths (d) saw a percent increase in shear strength of 31 to 68 percent, with an average increase of 50 percent, over tests with larger effective depths (d).Item Collapse investigation of the TU Delft faculty of architecture building : preliminary evaluation of member capacities(2010-08) Kirk, Adam Jess; Engelhardt, Michael D.; Ghannoum, Wassim M.On May 13, 2008, the Faculty of Architecture Building, or ‘Bouwkunde’, at the Delft University of Technology, Netherlands suffered a fire that resulted in the collapse of the northwest wing of the 13 story building. No one was injured but the building was a complete loss. Collapse of concrete buildings in fire is rare; this report aims to provide a preliminary evaluation of the structure and point to key areas that may be of interest to future analyses and investigations. To this end, a large database of information was collected, including original and renovation construction documents, original structural calculations, and over 3000 photographs of the structure during and after the fire. This data has been organized and reviewed to provide a clearer understanding of the building and fire. Preliminary models of the fire are developed and applied to selected structural elements in the FOA to the temperature distributions within the members. Also provided is an overview of available methods for calculating the ultimate strength of reinforced concrete members at elevated temperatures and a computer application, UT Fire: Reinforced Concrete Analysis, which can be used to estimate member capacities through a given fire event, based on their internal temperature distributions.Item Design for shear in reinforced concrete using strut-and-tie and sectional models(2005) Brown, Michael Douglas; Bayrak, OguzhanItem Design of reinforced concrete inverted-T beams for strength and serviceability(2013-05) Larson, Nancy Anne, 1986-; Bayrak, Oguzhan, 1969-Significant diagonal cracking in reinforced concrete inverted-T straddle bent caps has been reported throughout the State of Texas. Many of the distressed structures were recently constructed and all have been in service for less than two decades. The unique nature of the problem prompted a more detailed look into the design and behavior of such structural components. Strut-and-tie modeling is currently recommended for design of deep (rectangular) beams, but its application to more complex structures has not been fully explored. Due to concerns with current design provisions the application of strut-and-tie modeling to inverted-T beams was investigated along with serviceability-related considerations in this dissertation. An experimental study was conducted in which thirty-three reinforced concrete inverted-T beam tests were conducted. The effects of the following variables were evaluated: ledge depth and length, quantity of web reinforcement, number of point loads, member depth, and shear span-to-depth ratio. A strut-and-tie design method proposed by Birrcher et. al (2009), initially calibrated for compression-chord loaded deep beams, was investigated. It was concluded that the strut-and-tie method was a simple and accurate design method, and it was recommended for use in inverted-T beam design. A vi recommendation was also made for the amount of minimum web reinforcement needed for strength and serviceability considerations. A simple service-load check was proposed for the purpose of limiting diagonal cracking under service loads. Finally, a chart was created to aid in the evaluation of distressed, diagonally-cracked inverted-T bent caps in the field.Item Development of non-contact passive wireless sensors for detection of corrosion in reinforced concrete bridge decks(2013-12) Abu-Yosef, Ali Emad; Wood, Sharon L.Corrosion of embedded reinforcement is the leading form of deterioration affecting the integrity of reinforced and prestressed concrete bridge members around the world. If undetected, corrosion can limit the service life of the bridge and lead to expensive repairs. The research team at the University of Texas at Austin has developed a new class of passive wireless corrosion sensors. The noncontact (NC) sensor platform provides an economical and nondestructive means for detecting corrosion initiation within concrete. The sensor is powered through the inductive coupling to an external mobile reader that can be handheld or mounted on a vehicle. It is envisioned that the four-dollar sensor will be embedded in concrete during construction and interrogated sporadically over the service life of the structure. The sensor output can be used to detect corrosion initiation within concrete and is expected to enhance the quality information collected during qualitative routine bridge inspections. The NC sensor prototype consists of a resonant circuit that is inductively coupled to a sacrificial transducer. Corrosion of the sacrificial element alters the measured sensor response and is used to detect corrosion within concrete. Electrochemical evaluations were conducted to ensure that the sacrificial element exhibited identical response as the reinforcement steel. In addition, the results of extensive experimental parametric studies were used in conjunction with circuit and electromagnetic finite element models to optimize the NC sensor design. Long-term exposure tests were used to evaluate the reliability of the passive noncontact sensors. Sensors were embedded in reinforced concrete specimens and successfully detected the onset of corrosion in the adjacent reinforcement. Unlike the traditional corrosion evaluation methods, such as half-cell potentials, the sensors output was insensitive to environmental variations.Item Effect of uniform load on the shear strength of slender beams without shear reinforcement(2014-08) Dassow, Nicholas Alan; Bayrak, Oguzhan, 1969-; Hrynyk, TrevorPrevious studies have shown that a uniform distribution of load may increase the shear strength of a slender member by as much as 40 percent (Leonhardt and Walther 1964). The increase of shear strength is potentially due to clamping stresses induced from the uniform load, although a mathematical equation to quantify the effect of clamping stress in slender uniformly loaded members has yet to be derived (Acevedo et al. 2009). Only a small percentage of all shear tests on slender specimens without shear reinforcement were completed with uniform load. Additionally, the majority of uniform load data consists of specimens with small specimen depths (d) and large longitudinal reinforcement ratios (ρ). Six shear tests on specimens without shear reinforcement were completed at the University of Texas at Austin. Three of the six specimens were subjected to concentrated load, and the remaining three companion specimens were loaded uniformly. These specimens are among the deepest slender members without shear reinforcement that have ever been tested under a uniform load distribution. Importantly, the ratio of maximum shear to maximum moment was maintained between concentrated and uniform load tests which ensures directly comparable tests results. The experimental results were shown to be influenced by load distribution. Uniformly loaded specimens had an average increase in first diagonal cracking shear capacity of 17 percent with a range of increase between 10 and 23 percent when compared with specimens subjected to concentrated loads.Item Rehabilitation of poorly detailed RC structures using CFRP materials(2006-05) Kim, InSung; Jirsa, J. O. (James Otis)In many reinforced concrete structures built in the 1970's and earlier, bottom beam reinforcement is not continuous and if a column support is lost due to terrorist attack or other unexpected action, the structure could be vulnerable to progressive collapse. The use of CFRP material may provide a solution for rehabilitating such structures. CFRP materials cannot develop full tensile capacity unless they are properly anchored to the reinforced concrete structure. The intent of this study is to find an effective method of anchoring CFRP material to a reinforced concrete beam so that the ultimate tensile strength of the CFRP is realized. In this study, ten reinforced concrete beams rehabilitated using different configurations of anchors were tested to assess the effectiveness of the anchors. Both CFRP anchors and CFRP U-wraps were investigated. The rehabilitated beams were loaded until failure of the CFRP material or anchor occurred. Different failure modes, strengths and deformation capacities of the rehabilitated beams were observed depending on the configurations of anchors. The maximum capacity was obtained using a combination of CFRP anchors and U-wraps.Item Retrofit of deficient lap splice with post-installed anchors(2015-12) Beiter, Katelyn Sean; Bayrak, Oguzhan, 1969-; Hrynyk, Trevor DAs concrete infrastructure ages or is re-purposed, there is an increasing need for efficient retrofit solutions, with deficient lap splices being one of many research areas. A possible method to increase the capacity of deficient lap splices is to use post-installed undercut anchors. These anchors function as active confinement in the splice region, potentially allowing members with inadequate lap splice lengths to reach the required design capacity. The solution presented in this thesis requires access to only one face of the reinforced concrete specimen, which could facilitate implementation on existing structures. However, limited research has been done on the use of post-installed anchors as a retrofit strategy for lap splices, and previous research on the retrofit of deficient lap splices has focused primarily on the use of either carbon fiber or metal jackets. To evaluate the capabilities of this retrofit solution, four large-scale tests on beam specimens have been completed at The University of Texas at Austin. The first specimen tested contained the full lap splice length as required by ACI 318-71 provisions, while in the other three, only half of that lap splice length was provided. The specimen with the full lap splice length was tested as a control specimen and one of the specimens with half the lap splice length was tested without a retrofit to determine baseline behavior. These tests formed the basis to evaluate the effectiveness of the retrofit techniques implemented on the other two specimens. Results from these tests indicated that post-installed anchors could enhance both the strength and ductility of members with deficient lap splices, but the enhanced members demonstrated limited ductility.Item Shear behavior of reinforced concrete bridge pile cap girders strengthened with carbon fiber reinforced polymer (CFRP) strips and CFRP anchors(2016-08) Shekarchi, William Asad; Ghannoum, Wassim M.; Jirsa, J. O. (James Otis); Hrynyk, Trevor D; Juenger, Maria C.G.; Wheat, Harovel GExternally bonded CFRP strips are ideal for rehabilitating existing members due to their high tensile strength-to-weight ratio, relatively low cost, formability, and expedited installation times. However, without proper anchorage, CFRP strips debond from the concrete surface before the strength of the CFRP can be mobilized. Consequently, CFRP spike anchors are used to delay debonding and develop the fracture strength of the CFRP strips. Previous research conducted on large-scale T-beams have shown that uni-directional (vertical) and bi-directional (vertical and horizontal) applications of CFRP strips and anchors increased the cracking load and ultimate shear capacity of members with transverse steel reinforcement, thin webs, and span-to-depth ratios above three (i.e., sectional behavior). However, the ability of the CFRP to strengthen wide-webbed members remained unknown. The objective of this research was to investigate the feasibility of strengthening wide-webbed reinforced concrete pile cap girders in shear using CFRP strips and CFRP anchors and to develop comprehensive design and detailing recommendations for CFRP shear strengthening. An experimental test program, consisting of nine tests, was created to investigate: 1) the effects of loading conditions, 2) retrofitting uncracked and cracked sections, 3) placing anchors in tension zones, and 4) uni- and bi-directional CFRP layouts on the shear performance of 32-in. deep by 32-in. wide reinforced concrete pile cap girders. The test results indicated that the uni-directional CFRP layouts were able to increase the shear capacity by as much as 56% while the bi-directional layouts increased the cracking shear load by as much as 22%. Anchored CFRP layouts were found to be as efficient as fully wrapped layouts despite anchors being placed in tension zones. Moreover, at the onset of the loss of shear strength, the measured lower bound average CFRP fracture strain was 0.007, which is significantly larger than the permitted effective strain in current ACI 440.2R-08 design guidelines (i.e., 0.004). A database of test results from relevant CFRP strengthened specimens was collected, in addition to using the pile cap girder experimental results, to develop a rational design approach and detailing recommendations for CFRP shear strengthening.Item Shear cracking in inverted-T straddle bents(2011-08) Garber, David Benjamin; Bayrak, Oguzhan, 1969-; Ghannoum, WassimSignificant 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.Item Shear strength and effects of HDPE plastic post-tensioning duct on a prestressed girder(2013-05) Felan, James Oscar; Bayrak, Oguzhan, 1969-The goal of the splice girder research project 0-6652 funded by the Texas Department of Transportation is to utilize the full potential of splicing prestressed TX girders continuously. The TX girder family of beams is cost effective alone due to their simple, repetitive fabrication, but to truly optimize their potential would be to span several beams together as one continuous unit. The weight and length restrictions allowed by trucks or barges limit the prestressed beam lengths. Therefore, splicing together prestressed beams becomes the solution to the transporting obstacle. As a result, the prestressed girders will be more competitive to other bridge types such as steel I-girders, steel trapezoidal girders, cable-stayed bridges, and concrete segmental bridges. In fact, a prestressed/post-tensioned concrete bridge is preferred over steel designs in highly corrosive environments such as the coast or in snow regions where de-icing chemicals are used. In comparison, to a segmental box girder bridge, the post-tensioned prestressed bridge has reduced complexity due to fewer segments and the number of reduced joints susceptible to corrosion. The issue that arises with splicing prestressed beams is that in the process of connecting them together an opening must be made to install the post-tensioning (PT) steel strands. The openings are created by installing several steel or plastic circular ducts into the web region. Since the post-tensioning results in a reduction of the concrete web region, a modification is necessary to the shear capacity equation. The experimental study performed at the Ferguson Structural Engineering Laboratory consisted of fabricating and testing two full-scale prestressed Tx46 girders. One girder contained a plastic post-tensioning duct with grout and steel strands installed in the web region. The other beam was a standard Tx46 beam fabricated without a duct. Both beams had a reinforced concrete deck installed with an overhang to model an actual bridge section. Furthermore, the purpose of the standard beam was to serve as a direct comparison to the beam with a duct and determine the actual reduction in shear capacity. The research and findings will include the impact of the plastic duct in the Tx46 compared to the control beam. The failure loads of the test specimens will be compared to the current 2012 AASHTO code predictions for shear design. Also, revisions to the AASHTO code will be recommended if necessary. The primary goal of this research was to improve the design and detailing of the skewed end-blocks commonly used in these beams. As U-beams had been in service for several decades without incident, it was anticipated that there would be little need for change in the design, and the findings of the research would involve a slight tweaking to improve the overall performance.Item Shear strengthening of reinforced concrete beams with carbon fiber reinforced polymer (CFRP) under fatigue and sustained loading applications(2011-08) Satrom, Christopher Neil; Ghannoum, Wassim M.; Jirsa, J. O. (James Otis)Four specimens were tested to evaluate the shear performance of beams with carbon fiber reinforced polymer (CFRP) laminates and CFRP anchors under fatigue and sustained loading applications. The specimens consisted of 24-in. deep T-beams that were constructed and tested at Phil M. Ferguson Structural Engineering Laboratory at the University of Texas at Austin. The specimens were strengthened in shear with CFRP laminates anchored with CFRP anchors. One end of each specimen was strengthened using bonded CFRP laminates while the other end was strengthened using unbonded CFRP laminates. Two specimens were used for fatigue testing and two were used for sustained load testing. For each set of tests, one specimen was strengthened using CFRP laminates prior to cracking and one specimen was strengthened using CFRP laminates following the initial cracking of the specimen. The CFRP laminates showed no signs of deteriorations in strength during fatigue testing, with only small increases in strain occurring in the CFRP laminates during testing. After fatigue loading was completed, the specimens were monotonically loaded to failure. The failure loads were 5 to 15% lower than beams that were not subjected to fatigue loading. Sustained load tests were subjected to a constant midpoint load based on service load requirements for a period of 217 days. CFRP laminates performed well during sustained loading. CFRP strains increased slightly throughout testing, but no signs of deterioration were observed. For both types of tests, specimens strengthened using bonded CFRP laminates demonstrated an increased stiffness resulting in smaller crack widths and lower strains in the internal steel. These benefits were not as great in specimens strengthened after the initial cracking of the specimen.Item Strength, stiffness, and damage of reinforced concrete buildings subjected to seismic motions(2016-05) Kwon, Jinhan; Ghannoum, Wassim M.; Jirsa, James O.; Bayrak, Oguzhan; Hrynyk, Trevor; Sen, Mrinal K.Current analytical tools were calibrated mainly using pseudo-static experimental investigations of individual structural components. Relatively few tests have been performed on reinforced concrete structural systems under realistic boundary conditions and even fewer exist that were conducted dynamically due to the high costs and experimental challenges. Thus, the structural engineering field has resorted to a number of extrapolations from limited test data to form analytical models of structural systems they design. It is therefore no surprise that blind prediction contest results for structural strength and deformation are typically several times higher and lower than those from experiments. A complete system of a full-scale, four-story, reinforced concrete structure was tested under increasing seismic excitations, to near collapse damage states, one the National Research Institute for Earth Science and Disaster Prevention (NIED)/E-Defense shaking table in Japan. A moment frame system was adopted in one direction and a pair of shear walls incorporated in the exterior frames in the other direction. Wherever possible, minor adjustments to the designs were made to bring the final structures closer to U.S. seismic design provisions. No other tests currently exist that provide behavioral data about a complete, seismically detailed, reinforced concrete structural system tested under such realistic boundary conditions. Comprehensive and in-depth analyses were performed in light of the NIED/E-Defense test data to 1) assess the validity of current behavioral knowledge and design codes; 2) to assess the accuracy of current analytical methods for this common type of structure; 3) to recommend improvements and ways forward on both fronts. Implications of test results to U.S. seismic provisions and recommendations for estimating structural strength and stiffness of reinforced concrete buildings were made based on comparison between the estimates from the current analytical methods and the actual seismic behavior of the NIED/E-Defense test data.Item Strut-and-tie model design examples for bridge(2011-12) Williams, Christopher Scott; Bayrak, Oguzhan, 1969-; Ghannoum, Wassim M.Strut-and-tie modeling (STM) is a versatile, lower-bound (i.e. conservative) design method for reinforced concrete structural components. Uncertainty expressed by engineers related to the implementation of existing STM code specifications as well as a growing inventory of distressed in-service bent caps exhibiting diagonal cracking was the impetus for the Texas Department of Transportation (TxDOT) to fund research project 0-5253, D-Region Strength and Serviceability Design, and the current implementation project (5-5253-01). As part of these projects, simple, accurate STM specifications were developed. This thesis acts as a guidebook for application of the proposed specifications and is intended to clarify any remaining uncertainties associated with strut-and-tie modeling. A series of five detailed design examples feature the application of the STM specifications. A brief overview of each design example is provided below. The examples are prefaced with a review of the theoretical background and fundamental design process of STM (Chapter 2). • Example 1: Five-Column Bent Cap of a Skewed Bridge - This design example serves as an introduction to the application of STM. Challenges are introduced by the bridge’s skew and complicated loading pattern. A clear procedure for defining relatively complex nodal geometries is presented. • Example 2: Cantilever Bent Cap - A strut-and-tie model is developed to represent the flow of forces around a frame corner subjected to closing loads. The design and detailing of a curved-bar node at the outside of the frame corner is described. • Example 3a: Inverted-T Straddle Bent Cap (Moment Frame) - An inverted-T straddle bent cap is modeled as a component within a moment frame. Bottom-chord (ledge) loading of the inverted-T necessitates the use of local STMs to model the flow of forces through the bent cap’s cross section. • Example 3b: Inverted-T Straddle Bent Cap (Simply Supported) - The inverted-T bent cap of Example 3a is designed as a member that is simply supported at the columns. • Example 4: Drilled-Shaft Footing - Three-dimensional STMs are developed to properly model the flow of forces through a deep drilled-shaft footing. Two unique load cases are considered to familiarize the designer with the development of such models.Item A study of shear behavior of reinforced concrete deep beams(2013-12) Nguyen, Phu Trong, active 21st century; Jirsa, James O. (James Otis)Reinforced concrete deep beams are vital structural members serving as load transferring elements. The behavior of reinforced concrete deep beams is complex. Nonlinear distribution of strain and stress must be considered. Prior to 1999, ACI 318 Codes included an empirical design equation for reinforced concrete deep beams. Since 2002, the strut and tie model and nonlinear analysis have been required. However, both methods have disadvantages of complexity or lack of transparency. The objective of this study is to produce a simple, reliable design equation for reinforced concrete deep beams. A nonlinear finite element program, ATENA, was used for analyzing and predicting the behavior of concrete and reinforced concrete structures. First, applicability of ATENA was verified by developing the computer models of simply supported and two span continuous deep beams based on Birrcher’s tests of simply supported deep beams. Tests by Rogowsky and Macgregor and by Ashour are the basis for the models of continuous two span deep beams. Those tests were selected because the researchers reported adequate details of the experimental program and on specimen behavior. Then a series of simply supported and two span continuous deep beam models were developed based on the details and geometry of Birrcher's beams. The computer models were used to investigate the following parameters: the compressive strength of concrete, shear span to depth ratios, longitudinal reinforcement ratios, web reinforcement, effect of member depth, and loading conditions. Finally, a proposed design equation for shear strength of reinforced concrete deep beams was derived based on the observed the behavior of reinforced concrete deep beam tests, the results of the analytical study, and a plastic truss model. The proposed equations were in good agreement with test values and provide an alternate approach to current design procedures for deep beams.Item Undercut and grouted anchors as post-installed shear reinforcement(2014-12) Dondrea III, Anthony Louis; Bayrak, Oguzhan, 1969-; Hrynyyk, TrevorThe need for conservation in engineering has become apparent in the past several decades as a result of resource depletion, aging infrastructures, and diminishing real estate. In addition, many structures see increased loads due to building re-purposing; others simply do not meet the demands of modern code provisions. As a result, techniques to retrofit existing buildings are becoming increasingly important. This thesis investigates the use of post-installed undercut and grouted (rods grouted in place) anchors for strengthening reinforced concrete beams in shear. These techniques are especially useful when access to members requiring retrofit is limited. Experimental results are compared to the ACI-DAfStb shear database19,20 and to American Structural Design Code provisions. The results indicate that high strength anchors can effectively strengthen beams and achieve equivalent or greater deformation and load capacity as traditionally reinforced elements. However, precautions should be taken to avoid alternate anchor failure modes; a designer should validate that anchor yield can be achieved, or account for the possibility that post-installed anchors will not yield.