Stability calculations of prefabricated concrete structures with help of FEM-tools demand knowledge about how the elements are related to each other. This thesis concerns how joints between building elements affect the results when modelling prefabricated concrete structures, with demarcation to joints between hollow core (HC) slabs and between solid wall elements. The thesis also covers how the properties of the floor can be adjusted to account for the effects of the joints without modelling every single element. The work started by measuring the deflection of 10 HC-slabs jointed together and loaded in-plane acting as a deep beam, in a FE-model made with Robot™, from Autodesk®. The joints between the HC-elements were modelled either rigid or elastic, and the cross-section and the length of the HC-elements were varied. The linear elastic stiffness between the HC-elements was obtained from the literature as 0.05 (GN/m)/m. The results showed that a changed cross-section geometry gave greater differences in deformation than a changed length. The in-plane shear modulus was then adjusted for the HC-elements in the rigid cases until the same deflection was achieved as for the elastic cases. The result showed that the shear modulus in average for the different cross-section geometries and lengths had to be reduced with a factor of 0.1 to account for the joints. Based on the geometry of a castellated joint between prefabricated solid concrete walls, a calculation model was developed for its linear elastic stiffness. The result was a stiffness of 1.86 (GN/m)/m. To verify the calculated stiffness, a FE-model was developed consisting of a 30m high wall, loaded horizontally in-plane and with one or two vertical joints where the stiffness was applied. The deflection and the reaction forces were noted and the result from the calculated stiffness was compared to other stiffnesses and assessed reasonable. The reaction forces were shown to depend on the stiffness of the joint. The reduced in-plane shear modulus of the HC-elements and the calculated stiffness of the wall joints were then used in a FE-model of a 10-storey building stabilised by two units. The vertical reaction forces were analysed and the results showed 0.02 % difference in the reaction forces in the stabilising units when consideration of the joints between the HC-elements were taken into account and 0.09 % when the vertical joints in the shear wall were taken into account. The results for the wall joint differed from the results when only the wall was modelled. This was thought to be a result of that the floors counteract the shear deformations in the wall joints. The influence of the floor joints was not significant for the building considered in this thesis, but for buildings with non-continuous configuration of the stiffness in the shear walls the outcome may be another, in these cases the reduction factor may be useful. / Vid stabilitetsberäkningar av prefabricerade betongstommar med hjälp av FEM-verktyg ställs krav på kunskap om hur elementen förhåller sig till varandra. Detta arbete berör hur fogar mellan byggnadselement påverkar modellering av prefabricerade betongstommar med avgränsning till fogar mellan håldäckselement och mellan solida väggelement. Arbetet berör även en studie i hur ett bjälklags egenskaper kan justeras så att fogarnas effekt kan tillvaratas utan att modellera varje enskilt håldäckselement. Arbetet inleddes med att utböjningen analyserades hos 10 st ihopskarvade håldäckselement, lastade i dess plan likt en hög balk, i en FE-modell skapad i programmet Robot™, från Autodesk®. Fogarna mellan håldäcken modellerades som antingen rigida eller elastiska och håldäckens tvärsnittsgeometri och längd varierades under testet. Den linjära styvheten mellan håldäcken togs från litteraturen som 0.05 (GN/m)/m. Resultatet visade att ändrad tvärsnittsgeometri gav större skillnader för deformationen än varierad längd på håldäcken. Håldäckens skjuvmodul justerades sedan i dess plan för de rigida testen tills dess att de uppnådde samma utböjning som de elastiska. Resultatet visade att skjuvmodulen behövdes reduceras med en faktor 0.1, i medeltal för de olika tvärsnittsgeometrierna och håldäckslängderna. Utefter geometrin på en fog med förtagningar mellan prefabricerade väggar togs en beräkningsmodell fram för den linjärelastiska styvheten i väggfogarna. Resultatet blev en styvhet på 1.86 (GN/m)/m. För att verifiera den beräknade styvheten togs en FE-modell fram bestående av en 30m hög vägg lastad horisontellt i dess plan med en eller två vertikala fogar där en linjär styvhet applicerades. Utböjningen samt reaktionskrafterna noterades, resultatet för den uträknade linjära styvheten jämfördes med andra styvheter och bedömdes utifrån detta vara rimlig. Reaktionskrafterna visade sig vara beroende av styvheten på fogen. Den sänkta skjuvmodulen för håldäcken och den beräknade linjära elasticiteten för väggarna användes sedan i en FE-modell av en 10-våningsbyggnad med två stabiliserande enheter där de vertikala reaktionskrafterna analyserades. Resultatet visade att endast 0.02 procentenheter skiljer reaktionskrafterna i de stabiliserande enheterna då hänsyn tas till fogarna mellan håldäcken och 0.09 procentenheter då hänsyn tas till fogarna mellan väggarna. Resultatet skiljer sig från när endast väggen modellerades, vilket tros bero på att bjälklaget hjälper till att motverka deformationer i väggfogarna. Fogen mellan bjälklagselementen tros kunna ha större inverkan på en byggnad med stabiliserande enheter som drastiskt ändrar styvhet från ett plan till ett annat, i dessa fall kan den framtagna reduktionsfaktorn vara av nytta.

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Adjacent voided slab bridges (AVSB) are economical systems for short spans. They provide the advantages of having low clearances due to their small section depths, accelerated construction times, and high torsional stiffness. The current longitudinal connection detail, a partial depth grouted shear key, has been known to fail in many of these bridges. The failure leads to reflective cracking in the wearing surface which allows chloride laden water to seep down through the joint, where it corrodes the reinforcement and prestressing strand. Ultimately, the failed keys lead to costly repairs and bridge replacements sooner than their proposed lifespan. This research project aimed to develop a more durable longitudinal connection detail by using sub-assemblages to test five alternate connections. The objective was to find a connection that abated all cracking in the shear key, thus removing the need for transverse post-tensioning. The tested connections employed alternate connection shapes and two different mix designs of fiber reinforced high strength concretes. The results showed that each tested connection outperformed the current detail. The findings of this research indicate that the longitudinal connection detail of adjacent member voided slab bridges should be modified. The modified version should be a blockout with lap splice connection detail utilizing a nonproprietary fiber reinforced high strength concrete. / Master of Science

Adjacent box beam bridges are economical bridge systems for accelerated bridge construction. The box beams are constructed at precast plants and are traditionally connected by a shear key filled with grout. This system is ideal for short spans with low clearance restrictions. However, due to the grout deteriorating and debonding from the precast concrete in the shear key, reflective cracking propogates through the deck allowing water and chemicals to leak down into the joints. This can lead to the prestressing steel inside the precast member and the transverse tie steel corroding. This necessitates the bridge being rehabilitated or replaced which shortens the life-span of the bridge system and negates the economical value it had to begin with. This research project aimed to design a rehabilitation plan for an adjacent box beam bridge with deteriorated joints using Very High Performance Concrete (VHPC). VHPC was chosen as an economical alternative to the proprietary Ultra High Performance Concrete (UHPC) and extensive material tests were performed. The results of the material testing of VHPC and grout revealed that VHPC had higher compressive and tensile strengths, a higher modulus of elasticity, gained strength faster, bonded better to precast concrete, was more durable over time, and shrank less than conventional grout. The results of this research project were applied to rehabilitate the Buffalo Branch Bridge and further testing will be completed to determine the effectiveness of the rehabilitation. / Master of Science

Large-dimensional wooden products are highly demanded within the construction sector. Theprimary motive of the thesis is to find a solution to connect small timber elements by meansof special steel devices. It is auspicable that the resulting hybrid structure could match theload-carrying capacity of a corresponding homogenous timber element with the same size.The focus in this thesis is to study one type of shear-key connection. Three types of beams(pure glulam beam, hybrid beam either with or without the splice connection at mid-span) arestudied regarding their structural behaviours by means of theoretical analysis, numericalmodelling and experimental tests.Hybrid beam without the splice connection shows higher bearing capacity and higher stiffnessthan pure glulam beam no matter which method is used. The structural behaviours for hybridbeam without the splice connection obtained from each method are more or less similarexcept the failure mode.Hybrid beam with the splice connection shows the bearing capacity higher than pure glulambeam but lower than hybrid beam without the splice connection. The stiffness for hybrid beamwith the splice connection is approximately the same as that of the pure glulam beam basedon analytical and numerical calculation. However, around 30% - 40% lower stiffness isachieved in experiment. Factors that might influence the result are discussed in the main text.Two analytical methods (Partial composite action (PCA) Method and Gamma Method) areutilized for hybrid beam without the splice connection. Although Gamma method is asimplified method, the results are similar with that from PCA method. Therefore, GammaMethod is reliable to be used for the hybrid beam without the splice connection in this thesisproject.In addition, it is found that the alignment of shear-key connectors, slip modulus betweenshear-key and notch, diameter of rod and the vertical distance between glulam and rod areconsidered as the main sensitivity parameters that would influence the structural behaviours for hybrid beams a lot.

This thesis investigates the in-plane shear performance of full-scale walls made from compressed earth blocks. Compressed earth blocks are a type of masonry where the blocks are composed of compressed soil and typically dry-stacked without mortar. Prior research has demonstrated that the in-plane shear strength of these blocks falls far short of capacities predicted by conventional masonry building codes, requiring new testing to develop effective and safe designs for seismic conditions. This thesis specifically studies the effects of block type and the use of grouted shear keys at the block head joints. Three full-scale walls were constructed and tested under in-plane, cyclic loading. To compare the effect of block type on shear strength, one wall was constructed from Rhino blocks as used by the Center for Vocational Building Technology, while another used V-Lock blocks designed by the Vermeer Corporation. Apart from differences in size and interlock mechanism, the standard Rhino blocks have shear keys at the head joints which are not present on the V-Lock blocks. To examine the effect of these shear keys, a third wall was built from Rhino blocks with the shear keys removed. The two standard block types displayed no major difference in strength that could not be attributed to grouted area or the presence/absence of the head joint shear keys. The Rhino block wall with shear keys reached a higher peak load relative to the grouted area but experienced a brittle drop in capacity after peaking, while the other two walls exhibited an extended loading plateau after the initial peak. All walls failed with cracking and block sliding along the main diagonals, a failure mode similar to conventional masonry. Proposals are made for modifying the equations for shear capacity from the Masonry Standards Joint Committee (MSJC) 2013 code for use in designing compressed earth block shear walls.

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Yes / To investigate the flexural performance of steel-UHPC (ultra-high performance concrete) composite beams with welded steel shear keys (SSK), eight specimens were experimental studied by four-point bending test. The finite element (FE) models were established based on the experimental results, then, the failure mode, load, deflection, strain and relative interface slip were parametric analyzed. The influences of strength, dimensions and configuration of upper concrete slab, steel beams as well as SSK on flexural performance, in terms of load-deflection response, ductility and ultimate energy dissipation, were studied. The experimental results show that steel-UHPC composite beams have superior bearing capacity, deformation capacity, ductility and energy dissipation ability when compared with steel-NSC (normal strength concrete) composite counterparts. Increasing the height of upper concrete slab has a significant effect on improving bending capacity and flexural stiffness, while increasing the width has a significant effect on enhancing deformation, ductility and ultimate energy dissipation. Increasing the yield strength, thickness of web and flange of steel beams has significant effect on improving bending capacity. Reducing the SSK spacing or increasing the yield strength of SSK, height and thickness slightly improve the cracking, yield and ultimate loads, reduce deflections, enhance the flexural stiffness, slightly weakens the ductility and ultimate energy dissipation. Besides, four types of failure modes were defined, based on reasonable assumptions, formulae for bearing capacity were proposed, and the predicted results fit well with experimental results. The results can be taken as reference for the design and application of steel-UHPC composite beams in long-span and heavy-load structures. / The authors would like to acknowledge the financial support to the work by the Natural Science Foundation of Jiangsu Province, China (BK20201436), High-End Foreign Experts Project of Ministry of Science and Technology, China (G2022014054L), Science and Technology Project of Jiangsu Construction System (2021ZD06, 2018ZD047), Science and Technology Cooperation Fund Project of Yangzhou City and Yangzhou University (YZU212105, YZ2022194), Science and Technology Project of Yangzhou Construction System (202309, 202312, 202204). / The full text of this article will be released for public view at the end of the publisher embargo on 11th Aug 2024.

The adjacent box beam bridges (ABBB) are considered as an ideal solution for short to medium span bridges and for routes with low to medium traffic volumes. The ABBB system has been utilized and is popular in several states in the United States. However, this bridge system has long term durability issues caused by shear key failure and reflective cracking in the topping. The means and methods to alleviate the problems in connections between members of the ABBB were researched and the development of new connection details was pursued. Diagnostic tests to study the in-service behavior of ABBBs was performed. Two bridges with varying magnitude of joint deterioration were investigated. Both bridges were instrumented extensively and were subjected to known loads in the form of tandem trucks. The response of these bridges was studied and conclusions were made about the state of the bridges and the behavior after shear key failure. A finite element (FE) model of one of the tested bridges was developed to study the response of an ABBB with sound joints. The results of the finite element analysis (FEA) were compared with the results of the bridge diagnostic test. Conclusions about the FE model were made on the basis of this comparison. Another FE model, referred as the full scale bridge (FSB) was developed. The FSB model was used to simulate the behavior of an ABBB with the proposed connection details. This FSB model was subjected to design truck loads and the response was studied. The behavior of FSB model was replicated through a three beam sub-assembly that was supported on elastic supports. The stiffness of the elastic supports was calibrated such that the state of stress in the joints and the relative displacements between adjacent box beams in the sub-assemblage matched those in the FSB. The three beam sub-assembly was constructed with the proposed connection details. Two new connection details were proposed in this research. A Kevlar and epoxy connection and a spliced connection with fiber reinforced self-consolidating concrete are proposed. A total of six specimens, with different connection details, were constructed and tested for strength and durability in the laboratory. The behavior of the proposed connections and the connection materials were studied in detail. Additional FEA was performed to study the effect of shrinkage and temperature on the proposed connection details. / Ph. D.