Several reinforced concrete bent caps (deep beams) in Texas have developed significant diagonal cracks in service. The cracking in two bent caps was so extensive that costly retrofits were implemented to strengthen the structures. Strut-and-tie modeling is currently recommended in most U.S. design specifications for the design of reinforced concrete bent caps and deep beams. Designers have expressed concerns with the lack of clarity and serviceability-related considerations in strut-and-tie model design provisions. Due to concerns with strut-and-tie modeling design provisions and field problems of in-service bent caps, TxDOT Project 5253 was funded. Several tasks conducted within Project 5253 are addressed in this dissertation. The effects of minimum web reinforcement and member depth on the strength and serviceability behavior of deep beams are presented. The transition between deep beam shear capacity and sectional shear capacity near a shear-span-to-depth (a/d) ratio of 2 is addressed. A service-load shear check to limit diagonal cracking in service is outlined. Lastly, a simple chart that correlates the maximum width of diagonal cracks in a deep beam to its residual capacity is developed. To accomplish the objectives of Project 5253, thirty-seven tests were conducted on reinforced concrete beams with the following cross-sectional dimensions: 21”x23”, 21”x42”, 21”x44”, 21”x75”, and 36”x48.” The specimens were loaded with a/d ratios of 1.2, 1.85, and 2.5. The test specimens are among the largest reinforced concrete deep beams in the literature. To supplement the findings of the experimental program, a database of deep beam test results was compiled. Entries in the database that lacked sufficient information and that did not meet established cross-sectional size or web reinforcement criteria were filtered from the database. The use of the database in conjunction with the experimental program enabled each objective to be addressed from both broad and specific viewpoints. Several recommendations for improving the strength and serviceability design of deep beams are presented including a minimum web reinforcement requirement, provisions to ease the transition between calculated deep beam and sectional shear capacity, and a design check to limit diagonal cracking in service. / text

Purpose: Throughout the years numerous studies have been made that concludes thatcombining steel and wood results in improved strength. Under optimal conditions woodis an effective structural material, as it’s both cheap and durable. Steel on the other handunder right circumstances has considerably higher strength than wood. To combinewood and steel has over the last years gathered more attention. Studies shows thathybrid structures can lead to an economical advantage when building multiple storeybuildings, as it can replace or complete pure steel frames. The purpose of this paper isto increase the knowledge and understanding of how steel and wood cooperate and tofind out the advantages and disadvantages of using a flitched beam, as well as compareit’s strength to structural wood and glulam.Method: The paper comprises a quantitative study with two different kinds of datacollection methods, Literature studies and calculations. The literature study consists ofscientific papers and papers published by known institutions and will help the paperanswer the first issue. The calculations has been made with the help of Tekla Tedds,which follows the Eurocode design principles. Which will help the authors answer bothof the papers issues.Findings: The paper has found that the flitch beam has improved strength overstructural wood and glulam, but a significantly higher price. The flitch beam also has amuch higher self weight than structural wood and glulam. The flitch beam can also spanlonger than structural wood and glulam with the same applied load.Implications: The study have concluded that it’s hard to motivate the usage of flitchedbeams in floor designs as they have such high price. The flitch beam has higher strengththan both structural wood and glulam. Which makes the flitch beam a good option asload bearing beam that requires slim dimensions. The added strength of the flitch beamcan motivate the high price under the right circumstances.Limitations: The paper has limited the calculations to an enclosed environment andwill not take moisture or any other type of exposure in to account, As a dry indoorenvironment is optimal for both steel and wood. The calculations the paper uses arebased on Eurocode and all other forms of dimension principles will not be taken intoaccount. / Syfte: Genom åren har forskning gjorts som tyder på att när man kombinerar stål ochträ kommer det bidra till en ökad hållfasthet. Under optimala förhållande är trä ettotroligt effektivt och bra alternativ inom byggande då det är billigt och tåligt. Närstålbalkar däremot placeras i optimala förhållande kan de bibehåll betydligt mer ochstörre krafter än vad trävirke kan göra. Att kombinera stål och trä har de senaste årethaft ett ökat intresse. Studier visar att hybridbalkar kan vara till stor ekonomisk fördelvid byggnation av flervåningshus, då det kan ersätta eller komplettera rena stålstommar.Syftet med arbete är att öka kunskapen och förståelsen för hur stål och trä samverkarsamt ta reda på för och nackdelar hos de stålförstärkta träbalkarna samt jämföra deraslastkapacitet med konstruktionsträ- och limträbalkar.Metod: Arbetet omfattar en kvantitativ studie där två typer av datainsamlingsmetoderhar använts. Dessa två typer är beräkningar samt litteraturstudier. Litteraturstudienbestår av vetenskapliga artiklar som har hjälpt besvara en av frågeställningarna.Beräkningarna har använts för att besvara båda frågeställningarna, de har gjorts idimensioneringsprogrammet Tekla tedds som följer alla Eurocodes beräknings- ochdimensioneringsregler.Resultat: Resultaten visar på att den stålförstärkta träbalken har högre kapacitet änlimträ och konstruktionsvirke, både med hänsyn till nedböjning och brott men betydligthögre pris och egentyngd. Den stålförstärkta träbalken klarar även av längrespännvidder vid samma belastning.Konsekvenser: Utifrån de resultat rapporten kommit fram till är det svårmotiverat attanvända sig av de stålförstärkta balkarna i bjälklag på grund av det höga priset Denstålförstärkta träbalken klarar dock av högre laster än vad konstruktionsvirke och limträgör, vilket kan göra balken användbar som avväxlingsbalk. Att använda denstålförstärkta träbalken som avväxlingsbalk kan motivera det höga priset då den kanhålla mindre dimensioner än limträ och konstruktionsvirke vilket kan vara önskvärt iolika sammanhang.Begränsningar: De begränsningar som sattes för rapporten var att utesluta alla typerav miljörisker på balkarna som tillexempel fukt och solljus vid beräkningarna, då entorrmiljö är en optimal miljö för både trä och stål. Beräkningarna som arbetet baseraspå grundar sig på Eurocodes dimensioneringsregler. Andra typer av dimensioneringsprinciper har uteslutits.

An investigation into the load-settlement behavior of two drilled shafts, founded in shale, is presented. The motivation for this research is to advance the understanding on how drilled shafts react under loading in stiff clays and shales. The objectives of the study are to measure the strengths within the subsurface material at the test site, estimate the unit side shear and unit end bearing of the shale-shaft interaction by running two axial load tests, and compare the results to the current design methods that are used to predict the axial capacity of drilled shafts. A comprehensive field investigation, performed by Fugro Consultants, provided strength profiles of the subsurface material at the test site. Through the cooperation of the Texas Department of Transportation (TxDOT), the Association of Drilled Shaft Contractors, and McKinney Drilling Company, two drilled shafts were installed at a highway construction site in Austin, Texas. The load tests were performed by Loadtest, Inc.; using the patented Osterberg-Cell™ loading technique to axially displace the shafts. Ensoft, Inc. installed strain gauges at multiple levels within the shafts, making it possible to analyze the shaft mobilization during loading. Ultimate end bearing values of about 100- and 120-ksf were measured for Test Shafts #1 and #2, respectively. The current methods for estimating unit end bearing, developed by TxDOT and the Federal Highway Administration, provide fairly accurate predictions when compared to the measured information. The ultimate side resistance obtained near the O-Cell™ in each test was about 20-ksf, however, the measured ultimate side resistance steadily decreased nearing the tip of the shaft. For the zones where the side resistance was believed to be fully mobilized, the TxDOT design method accurately predicts the side resistance. A limited amount of information is currently available for load tests performed in soils with TCP values harder than 2-in per 100 blows. Additional load test information should allow for a stronger correlation between TCP tests and unit resistances for very hard clay-shales, as well as, allowing for further evaluation of the shale-shaft interaction near the shaft tip. The results presented herein demonstrate the effectiveness of the current design methods for drilled shafts and the non-uniformity of side resistance within one- to two-diameters of the shaft tip. / text

Textile Reinforced Concrete (TRC) with a small thickness, high tensile and compressive strength has been combined with lightweight materials to create sandwich elements. Due to the low strength of the core materials in the sandwich elements, the additional shear connector devices were suggested to improve the load capacity. However, it raised an idea of using a higher strength material core, Expanded Polystyrene Concrete (EPC), without any connector devices to create a new type of lightweight sandwich element, which can be an answer for not only developing lightweight structures but also solving environmental problems. In this thesis, this novel idea was gradually realized with a study on TRC-EPC sandwich beams. Firstly, experimental material tests on EPC showed the possibility to recycle EPS waste for EPC with a density of around 950 kg/m3. Thus, an EPC with a density of 920 kg/m3 and a compressive strength of 5.2 N/mm2 was chosen for the core to realize the concept for TRC-EPC sandwich with 18 experimental beams. Bending tests of six series with shear-to-depth-ratio (a/d) from 1.5 to 5.2 were implemented to study load responses of this type of sandwich beam. The failure moments of all the specimens were smaller than the nominal moment strength of the cross section. The load capacities of the specimens depend strongly on the ratio a/d. The calculations for the shear capacity according to standards as well as shear calculation approaches were implemented. Due to their generalized form, ACI 318-05 and EC2 offer conservative results for a/d<5.2. The dependence of the shear capacity on a/d could be better described with CEB-FIB Model Code 1990. For the beams with 1.5<a/d and a/d<2.1, Strut and Tie Model gave the most suitable results. In case a/d>2.1, ZINK’s model offered better results than the others. Besides, a new proposed equation for the shear capacity of TRC-EPC sandwich beams depending on the a/d was also suggested. In order to model the load response of the six experimental series, FEM models with ATENA developed. The models with and without a consideration of the bond between the textile and fine HSC in the TRC layer underestimated the load capacity with tolerance 26% and 28 % respectively. The tolerances for the deflections in the models with a/d>2.5 were around 22 % and 23%. Finally, an engineering model originally based on sandwich theory was developed to model the load-deflection response of this type of sandwich beams. The model could predict the displacement with tolerances from -24 % to 12 %. The load capacity of TRC-EPC sandwich beams was underestimated with a tolerance in the range of 15- 34 %. / In dieser Arbeit wurde eine neue Sandwichkonstruktion untersucht, für die Textilbeton, ein Werkstoff mit geringer Dicke und gleichzeitig hoher Zug- und Druckfestigkeit, mit leichten Kernmaterialien kombiniert wurde. Aufgrund der geringen Festigkeit der Kernmaterialien werden in vielen Sandwichkonstruktionen zusätzliche Schubverbinder benötigt, um eine ausreichende Tragfähigkeit zu erreichen. Dies führte zu der Idee, Expanded Polystyrene Concrete (EPC) als höherfestes Kernmaterial zu verwenden, das keine zusätzlichen Verbindungsmittel benötigt. Damit entsteht eine neuartige Sandwichkonstruktion, die nicht nur eine Lösung für die Entwicklung neuer leichter Strukturen ist, sondern auch für Umweltprobleme. Diese Idee wurde in dieser Arbeit durch theoretische und experimentelle Untersuchungen an Textilbeton-EPC-Sandwichbalken umgesetzt. Zunächst wurden Materialuntersuchungen an EPC durchgeführt, um nachzuweisen, dass es möglich ist, EPC mit einer Dichte von rund 950 kg/m³ mit recyceltem EPS herzustellen. Für die anschließenden Untersuchungen an 18 Sandwichbalken wurde dann ein EPC mit einer Dichte von 920 kg/m³ und einer Druckfestigkeit von 5,2 N/mm² ausgewählt. In 6 Serien von Sandwichbalken wurden 4-Punkt-Biegeversuche mit Schubschlankheiten von 1,5 bis 5,2 durchgeführt. Die Bruchmomente aller Balken waren geringer als die rechnerische Momententragfähigkeit des Querschnitts und die Tragfähigkeit war stark von der Schubschlankheit abhängig. Es wurden Berechnungen zur Schubtragfähigkeit nach den verschiedenen internationalen Normen durchgeführt. Aufgrund ihrer allgemeingültigen Form ergaben ACI 318-05 und EC2 sehr konservative Ergebnisse für Schubschlankheiten kleiner als 5,2. Die Formulierung des CEB-FIB Model Code 1990 war besser geeignet, die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit abzubilden. Für die Balken mit Schubschlankheiten a/d=1,5 bis 2,1 brachten Stabwerkmodelle ausreichend gute Ergebnisse. In Fällen mit a/d>2,1 ergab das Modell von Zink die besten Übereinstimmungen. Um die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit besser erfassen zu können, wurde eine neue Berechnungsgleichung für Textilbeton-EPC-Balken vorgeschlagen. Um das Last-Verformungsverhalten der experimentellen Untersuchungen beschreiben zu können, wurden FEM-Modelle mit der Software ATENA entwickelt. Es wurden verschiedene Modelle untersucht, die den Verbund zwischen dem textilen Gelege und dem Feinbeton unterschiedlich stark berücksichtigten. Die Tragfähigkeit der untersuchten Balken wurde mit den FEM-Modellen um ca. 26% bis 28% unterschätzt. Die Abweichungen in den berechneten Durchbiegungen betrugen für die Balken mit a/d>2,5 ca. 22% bis 23%. Abschließend wurde ein Ingenieurmodell auf Grundlage der Sandwichtheorie entwickelt, mit dem das Last-Verformungsverhalten dieser Sandwichkonstruktion gut beschrieben werden kann. Mit dem Modell ergaben sich Abweichungen von -24% bis +12% zwischen experimentellen und theoretisch ermittelten Verformungen. Die Tragfähigkeit wurde mit einer Abweichung von 15% bis 34% unterschätzt.

Textile Reinforced Concrete (TRC) with a small thickness, high tensile and compressive strength has been combined with lightweight materials to create sandwich elements. Due to the low strength of the core materials in the sandwich elements, the additional shear connector devices were suggested to improve the load capacity. However, it raised an idea of using a higher strength material core, Expanded Polystyrene Concrete (EPC), without any connector devices to create a new type of lightweight sandwich element, which can be an answer for not only developing lightweight structures but also solving environmental problems. In this thesis, this novel idea was gradually realized with a study on TRC-EPC sandwich beams. Firstly, experimental material tests on EPC showed the possibility to recycle EPS waste for EPC with a density of around 950 kg/m3. Thus, an EPC with a density of 920 kg/m3 and a compressive strength of 5.2 N/mm2 was chosen for the core to realize the concept for TRC-EPC sandwich with 18 experimental beams. Bending tests of six series with shear-to-depth-ratio (a/d) from 1.5 to 5.2 were implemented to study load responses of this type of sandwich beam. The failure moments of all the specimens were smaller than the nominal moment strength of the cross section. The load capacities of the specimens depend strongly on the ratio a/d. The calculations for the shear capacity according to standards as well as shear calculation approaches were implemented. Due to their generalized form, ACI 318-05 and EC2 offer conservative results for a/d<5.2. The dependence of the shear capacity on a/d could be better described with CEB-FIB Model Code 1990. For the beams with 1.5<a/d and a/d<2.1, Strut and Tie Model gave the most suitable results. In case a/d>2.1, ZINK’s model offered better results than the others. Besides, a new proposed equation for the shear capacity of TRC-EPC sandwich beams depending on the a/d was also suggested. In order to model the load response of the six experimental series, FEM models with ATENA developed. The models with and without a consideration of the bond between the textile and fine HSC in the TRC layer underestimated the load capacity with tolerance 26% and 28 % respectively. The tolerances for the deflections in the models with a/d>2.5 were around 22 % and 23%. Finally, an engineering model originally based on sandwich theory was developed to model the load-deflection response of this type of sandwich beams. The model could predict the displacement with tolerances from -24 % to 12 %. The load capacity of TRC-EPC sandwich beams was underestimated with a tolerance in the range of 15- 34 %. / In dieser Arbeit wurde eine neue Sandwichkonstruktion untersucht, für die Textilbeton, ein Werkstoff mit geringer Dicke und gleichzeitig hoher Zug- und Druckfestigkeit, mit leichten Kernmaterialien kombiniert wurde. Aufgrund der geringen Festigkeit der Kernmaterialien werden in vielen Sandwichkonstruktionen zusätzliche Schubverbinder benötigt, um eine ausreichende Tragfähigkeit zu erreichen. Dies führte zu der Idee, Expanded Polystyrene Concrete (EPC) als höherfestes Kernmaterial zu verwenden, das keine zusätzlichen Verbindungsmittel benötigt. Damit entsteht eine neuartige Sandwichkonstruktion, die nicht nur eine Lösung für die Entwicklung neuer leichter Strukturen ist, sondern auch für Umweltprobleme. Diese Idee wurde in dieser Arbeit durch theoretische und experimentelle Untersuchungen an Textilbeton-EPC-Sandwichbalken umgesetzt. Zunächst wurden Materialuntersuchungen an EPC durchgeführt, um nachzuweisen, dass es möglich ist, EPC mit einer Dichte von rund 950 kg/m³ mit recyceltem EPS herzustellen. Für die anschließenden Untersuchungen an 18 Sandwichbalken wurde dann ein EPC mit einer Dichte von 920 kg/m³ und einer Druckfestigkeit von 5,2 N/mm² ausgewählt. In 6 Serien von Sandwichbalken wurden 4-Punkt-Biegeversuche mit Schubschlankheiten von 1,5 bis 5,2 durchgeführt. Die Bruchmomente aller Balken waren geringer als die rechnerische Momententragfähigkeit des Querschnitts und die Tragfähigkeit war stark von der Schubschlankheit abhängig. Es wurden Berechnungen zur Schubtragfähigkeit nach den verschiedenen internationalen Normen durchgeführt. Aufgrund ihrer allgemeingültigen Form ergaben ACI 318-05 und EC2 sehr konservative Ergebnisse für Schubschlankheiten kleiner als 5,2. Die Formulierung des CEB-FIB Model Code 1990 war besser geeignet, die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit abzubilden. Für die Balken mit Schubschlankheiten a/d=1,5 bis 2,1 brachten Stabwerkmodelle ausreichend gute Ergebnisse. In Fällen mit a/d>2,1 ergab das Modell von Zink die besten Übereinstimmungen. Um die Abhängigkeit der Schubtragfähigkeit von der Schubschlankheit besser erfassen zu können, wurde eine neue Berechnungsgleichung für Textilbeton-EPC-Balken vorgeschlagen. Um das Last-Verformungsverhalten der experimentellen Untersuchungen beschreiben zu können, wurden FEM-Modelle mit der Software ATENA entwickelt. Es wurden verschiedene Modelle untersucht, die den Verbund zwischen dem textilen Gelege und dem Feinbeton unterschiedlich stark berücksichtigten. Die Tragfähigkeit der untersuchten Balken wurde mit den FEM-Modellen um ca. 26% bis 28% unterschätzt. Die Abweichungen in den berechneten Durchbiegungen betrugen für die Balken mit a/d>2,5 ca. 22% bis 23%. Abschließend wurde ein Ingenieurmodell auf Grundlage der Sandwichtheorie entwickelt, mit dem das Last-Verformungsverhalten dieser Sandwichkonstruktion gut beschrieben werden kann. Mit dem Modell ergaben sich Abweichungen von -24% bis +12% zwischen experimentellen und theoretisch ermittelten Verformungen. Die Tragfähigkeit wurde mit einer Abweichung von 15% bis 34% unterschätzt.

No description available.

Shear strength of precast/prestressed hollow-core (PHC) slabs subjected to concentrated or line loads, especially near supports, may be critical and usually is the governing criteria in the design. This study presents the second phase of a research program, undergoing at the University of Manitoba, to calibrate the shear equations in the Canadian code for predicting the shear capacity of PHC slabs. This phase includes both experimental and numerical investigations using a finite element analysis (FEA) software package. The length of bearing, void shape and size, level of prestressing and shear span-to-depth ratio were investigated. The experimental results were compared to the predictions of the Canadian, American and European codes. It was concluded that the Canadian code is unduly conservative. However, the special European code for PHC slabs resulted in better and more consistent predictions. The FEA suggested that the adequate prestressing reinforcement ratio to obtain highest shear capacity ranges between 0.7% and 1.1%.

Shear strength of precast/prestressed hollow-core (PHC) slabs subjected to concentrated or line loads, especially near supports, may be critical and usually is the governing criteria in the design. This study presents the second phase of a research program, undergoing at the University of Manitoba, to calibrate the shear equations in the Canadian code for predicting the shear capacity of PHC slabs. This phase includes both experimental and numerical investigations using a finite element analysis (FEA) software package. The length of bearing, void shape and size, level of prestressing and shear span-to-depth ratio were investigated. The experimental results were compared to the predictions of the Canadian, American and European codes. It was concluded that the Canadian code is unduly conservative. However, the special European code for PHC slabs resulted in better and more consistent predictions. The FEA suggested that the adequate prestressing reinforcement ratio to obtain highest shear capacity ranges between 0.7% and 1.1%.