El presenta trabajo consistió en la evaluación de los indicadores de comportamiento sísmico: sobre resistencia y ductilidad para edificios aporticados de concreto armado a través del método estático no lineal con un software estructural. Para esto se sometió a evaluación edificios de 3, 6, 9,12 ,15 y 18 pisos. Los resultados de esta investigación mostraron que a medida que el periodo fundamental de una estructura aumenta, la sobre resistencia aumenta también, más no se puede plantear una tendencia clara. En el caso de la ductilidad hay una tendencia polinómica clara para cada eje del edificio: a medida que el periodo fundamental aumenta la ductilidad disminuye. Por otro lado la capacidad real de la estructura es superior al cortante de diseño que se muestra en la norma E-030. The present work consisted of the evaluation of the indicators of seismic behavior: over strength and ductility for reinforced concrete buildings moments frames with the static non - linear method using a structural software. For this, 3, 6, 9, 12, 15 and 18-story buildings have been evaluated. The results of this research showed that as the fundamental period of a structure increases, over strength also increases, but a clear trend can not be given. In the case of ductility there is a clear polynomial tendency for each axis of the building: as the fundamental period increases the ductility decreases. On the other hand, the actual capacity of the structure is superior to the design shear shown in Standars of E-030.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22066号 / 工博第4647号 / 新制||工||1725(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 辻 伸泰, 教授 安田 秀幸, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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The purpose of this work is to understand the reasons for varied mechanical properties among three polymer Powder Bed Fusion (PBF) Additive Manufacturing (AM) processes. Parts for this work were manufactured from Polyamide 12 (PA12) using the Laser Powder Bed Fusion (L-PBF), Multi-Jet Fusion (MJF), and the recently developed Large Area Projection Sintering (LAPS) processes. Previous works have shown that LAPS parts demonstrate significantly higher density, ductility, and toughness than parts from the L-PBF and MJF processes. A hot isostatic pressing (HIP) treatment was developed to reduce porosity in L-PBF and MJF parts and determine if increasing part density would improve ductility for these processes. It is found that density is not strongly correlated with mechanical properties for high density parts (ρ > 0.98 g/cm3) for the L-PBF and MJF processes, and a following study confirms that this is the case for the LAPS process as well. Differential Scanning Calorimetry (DSC) and microtome sectioning are performed on parts from all three processes, and it is found that neither percent crystallinity nor crystalline morphology are strongly correlated with mechanical properties. A heat treatment at temperatures well over the melting point for the material is developed and is shown to improve ductility and toughness for all three processes. It is concluded that the improved ductility observed in the LAPS process stems from long exposure to high temperature, rather than increased density or a specific crystalline structure, and is associated with post-condensation reactions increasing polymer chain length. Work is also presented on the development of a production-scale LAPS system at Ascend Manufacturing. This research focuses on the results of "tiling" and "scanning" methods for producing larger parts than previously possible with prototype LAPS systems. Tensile testing showed that the methods both produced parts with similar properties, though with lower ductility than previous LAPS parts. Analysis of thermal data identifies areas for improvement of the system to attain high strength and high ductility parts. Preliminary work is done to demonstrate avenues for process improvement. Analysis of data from across the entire powder bed shows that process defects can be observed from the thermal data available in the LAPS process, and that weak spots in parts may be related to this data. Finally, the potential for process improvement through a multiple-input, multiple-output (MIMO) control scheme is discussed.

In recent earthquakes, structures have not performed as well as expected resulting in a need for better means of retrofitting and improvements in seismic design. Fiber Reinforced Polymers (FRP), as a material with potential to increase strength and ductility of columns in conjunction with capacity design methodology, has promise for seismic design. By investigating the displacement, ductility, and flexural strength properties of FRP confined reinforced concrete circular cross sections, this study analyzes the seismic applications of FRP confinement. The study is performed by incorporating an FRP confined concrete stress-strain model into a developed Moment-Curvature and PM Interaction software. This software conducts a comparison between traditional steel and FRP confined sections while performing parameter studies on the 28-day unconfined concrete compressive strength, longitudinal reinforcing ratio, cross section diameter, FRP confinement jacket thickness-cross section diameter ratio, and FRP confinement system design variables. These studies validate FRP’s performance for seismic applications resulting in several design recommendations to increase displacement capacity, ductility, and flexural strength and, thus, seismic performance.

The research presented in this thesis is to evaluate the feasibility of demountable shear connectors as an alternative to welded shear connectors in composite structures through push off tests and composite beam tests. Push off tests were conducted to examine the shear strength, stiffness and ductility of demountable shear connectors in composite structures. The experimental results showed that demountable shear connectors in composite structures have very similar shear capacity to welded shear connectors. The shear capacity was compared against the prediction methods used for the welded shear connections given in Eurocode 4 and AISC 360-10 and the methods used for bolted connections in Eurocode 3 and ACI 318-08. It was found that the AISC 360-10 and ACI 318-08 methods overestimated the shear capacity in some cases. The Eurocode method is conservative and can be utilised to predict the shear capacity of demountable connectors in composite structures. The experimental studies of two identical composite beams using demountable shear connectors and welded shear connectors showed very similar moment capacity. However, the specimen with demountable shear connectors was more ductile compared to the welded specimen. The experimental study suggests that the methods available in Eurocode 4 and BS 5950 for predicting moment capacity and mid span deflection can be adopted for composite beam with demountable shear connectors. In addition, a finite element analysis of push off test and beam test with demountable shear connectors was also conducted for parametric studies and results are used to evaluate the behaviour of composite structures. / EPSRC and the University of Bradford

No / This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC. / National Natural Science Foundation of China (51678514, 51308490), the Natural Science Foundation of Jiangsu Province, China (BK20130450), Six Talent Peaks Project of Jiangsu Province (JZ-038, 2016), Graduate Practice Innovation Project of Jiangsu Province (SJCX17-0625) and the Jiangsu Government Scholarship for Overseas Studies.

<p> Small scale tests were utilized in order to obtain characteristic fracture mechanics parameters such as the crack opening displacement (C.O.D.) and the J-integral. Two main types of steels were used (H.S.L.A. and AISI 4340) in obtaining data over a wide range of yield strengths and ductilities. Tests were done to see the effect of both notch geometry and sample geometry·in one of the H.S.L.A. steels, and it is verified that the minimum value of C.O.D., at crack initiation in plane strain, is independent of the geometry and plastic zone size. Further the development of a simple single specimen J-integral test method is done during this work. In terms of the data obtained both the minimum C.O.D.i values and the Jlc values increase with increasing ductility of the materials tested. In the attempt to relate the magnitude of the fracture toughness with microstructural parameters and the limiting processes occuring at the crack tip prior to fracture, the concept of the process zone is discussed. For this study a simple plain carbon steel spheroidized with different carbon contents was examined in addition to the H.S.L.A. and 4340 steels. From the data obtained the minimum C.O.D.i at crack initiation was found to be approximately equal to the product of the materials plain strain ductility and a characteristic distance scaling with the spacing between large non metallic inclusions or the spacing between the bands of the sulphides. </p> / Thesis / Master of Engineering (MEngr)

The use of fiber reinforced plastics (FRP) in repairing and strengthening bridges has been researched in recent years. In particular, attaching unidirectional FRP to the tension face of reinforced concrete beams has provided an increase in stiffness and load capacity of the structure. However, due to the brittle nature of the unidirectional FRP, the ductility of the beam decreases. One possible solution to this problem is the use of cross-ply or off-axis FRP laminates. This thesis focuses on the investigation of the flexural behavior of reinforced concrete beams strengthened with one of two different FRP orientations (0°/90° and ±45°). More particularly, the change in strength and ductility of the beams as the number of FRP layers are altered is investigated. Seven under-reinforced concrete beams were constructed and tested to failure. With the exception of the control beam, each specimen was applied with two, three, or four layers of either 0°/90° and ±45° FRP orientations. To predict the flexural behavior of the specimens, a theoretical model was derived using basic concepts, past research, and the tested properties of the concrete, steel reinforcement, and FRP. Also, two methods were used to analyze the ductility of the tested beams. Along with the test details of each specimen; the moment, deflection, CFRP strain, crack patterns, and mode of failure are discussed. The results included an increase in load capacity with respect for the number of CFRP layers applied for both orientations. Also, the ductility of the beams were reduced by adding CFRP orientations. / Master of Science