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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.
1

Performance-Based Analysis of Steel Buildings: Special Concentric Braced Frame

Adams, Scott Michael 01 September 2010 (has links)
The performance-based analysis methods and evaluation criteria in ASCE 41-06 were used to evaluate a special concentric braced frame building based on the design standards in ASCE 7-05. A rectangular, six-story office building was evaluated using linear static, linear dynamic, nonlinear static, and nonlinear dynamic procedures. The results showed that the linear procedures underestimated damage compared to the nonlinear procedures, with the building performing to Life Safety for the linear procedures, and the nonlinear procedures indicating component damage beyond the intended Life Safety limit for the 2/3 maximum considered earthquake (MCE) hazard. This trend continued to the maximum considered earthquake hazard as well, under which the overall building performance for the linear procedures did not reach the Collapse Prevention level, which occurred in the nonlinear procedures.
2

The development of Hong Kong structural engineering standards after the Second World War and before 1997 Zhan hou dao hui gui qian Xianggang jie gou gong cheng gui fan fa zhan de tan tao /

Ma, Koon-yiu. January 2007 (has links)
Thesis (M. A.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.
3

Lateral load analysis of shear wall-frame structures

Akış, Tolga. January 2004 (has links) (PDF)
Thesis (Ph. D.)--Middle East Technical University, 2004. / Keywords: Shear Wall, Shear Wall-Frame Structures, Wide Column Analogy.
4

State-of-the-art review: Seismic response analysis of Operational and Functional Components (OFCs) in buildings

Asgarian, Amin 2013 June 1900 (has links)
A building is composed of two main types of components: structural components (see Figure 1) and non-structural components (NSCs) also called operational and functional components (OFCs) (see Figure 2). OFCs are those components or systems housed or mounted in the buildings which are not part of the main or intended load-resisting system of the structure. Therefore, the building structure is commonly called “primary structure” or “supporting structure” and OFCs are also known by alternative names such as "non-structural elements", "building attachments", "architectural, mechanical, and electrical elements", "secondary systems", and "secondary structural elements".
5

P-DELTA EFFECTS ON STEEL MOMENT FRAMES WITH REDUCED BEAM SECTION CONNECTION

Shakya, Anuj Man 01 August 2011 (has links)
The P-delta effect is a second order effect experienced by any structure when subjected to lateral loads like earthquake or wind loads, and is originated by an additional destabilizing moment generated due to the gravity acting on the laterally deflected member further displacing it. For the purpose of this research, displacement is considered as the study parameter to analyze the second order P-Delta effects. The main objective of this study is to investigate effects of forces causing P-Delta effects on Single Story Single Bay Steel Moment Frames with Reduced Beam Section Connection (RBS). FEMA-350 and AISC Seismic Design Manual suggest that, if the specified conditions are satisfied, there is no need to provide additional panel zone reinforcements as continuity and doubler plates. This study makes an effort to observe the effects of panel zone strength in formation of plastic hinges and in shifting fracture zone away from the column face on frames with RBS connections under P-Delta effects and find whether further increasing the stiffness of panel zone will have beneficial outcome or not.
6

Parametric study of stiffened steel containment shell structures

Masendeke, Rugare B January 2008 (has links)
Includes bibliographical references. . / A FEM-based parametric study is undertaken to investigate the buckling behavior of meridionally and circumferentially stiffened steel cylindrical and conical shell frustum subjected to different load cases. This situation arises in different steel shell applications such as storage vessels (liquid, solid and gas) and in certain configurations of industrial process facilities. The stiffeners are flat strips of rectangular section welded on to the outer surface of the shell, either over the whole length of the shell meridian or around the circumference of the shell. It is required to establish how the elastic buckling load and mode shapes vary with respect to certain key parameters of the problem. The parameters of interest in the study include the number of stiffeners around the shell circumference and along the meridian, the stiffener-depth to shell-thickness ratio, and the stiffener depth-to-width ratio. This thesis reports the findings of the parametric study and also presents some results of experimental tests on laboratory small-scale models of stiffened cylindrical and conical frusta.
7

A Proper Orthogonal Decomposition-based inverse material parameter optimization method with applications to cardiac mechanics

Moodley, Kamlin January 2016 (has links)
We are currently witnessing the advent of a revolutionary new tool for biomedical research. Complex mathematical models of "living cells" are being arranged into representative tissue assemblies and utilized to produce models of integrated tissue and organ function. This enables more sophisticated simulation tools that allows for greater insight into disease and guide the development of modern therapies. The development of realistic computer models of mechanical behaviour for soft biological tissues, such as cardiac tissue, is dependent on the formulation of appropriate constitutive laws and accurate identification of their material parameters. The main focus of this contribution is to investigate a Proper Orthogonal Decomposition with Interpolation (PODI) based method for inverse material parameter optimization in the field of cardiac mechanics. Material parameters are calibrated for a left ventricular and bi-ventricular human heart model during the diastolic filling phase. The calibration method combines a MATLAB-based Levenberg Marquardt algorithm with the in-house PODIbased software ORION. The calibration results are then compared against the full-order solution which is obtained using an in-house code based on the element-free Galerkin method, which is assumed to be the exact solution. The results obtained from this novel calibration method demonstrate that PODI provides the means to drastically reduce computation time but at the same time maintain a similar level of accuracy as provided by the conventional approach.
8

The Use of The Sectorial Coordinate Approach to Demonstrate Unique Shear Centre Properties of Nonstandard Monosymmetric Steel Sections

Muukua, Mervin Mbakekua 16 February 2021 (has links)
The study looks at how the sectorial coordinate approach can be used to solve the problem of unique shear centre property of non-standard monosymmetric sections. In solving the unique shear centres, the behaviour of the shear centre with reference to the centroid is carefully studied as the geometry of the section is changed. The study shows investigations of the sections which are 152x152x30 UC H-section, the same H-section with 2/3 as well as 1/3 of the bottom flange width and a 203x178x30 T-section. Vertical plates of 8mm thickness are added to the ends of the upper flanges of the sections instigating increments of 12.5mm from 0 to 100mm height. From the computations done, the following is observed: • The difference between the sectorial coordinate approach results and those from Prokon is at most 3.1%. Also, as the end plate heights are increased, the difference in the results increases. • Shear centres change in position with reference to the centroids as a result of the change in geometry of the sections. • For the H-section the shear centre is initially with the centroid at zero plate height. It then moves upward (higher than the centroid) to a certain peak point, then decreases steadily, intersecting the centroid again and eventually ending up being lower than the centroid with upstanding plate height increases. • A similar pattern follows the H-sections with reduced bottom flange widths, with the only difference being that the shear centre is initially higher than the centroid. It slightly increases to a peak then gradually decreases, intersecting the centroid at a certain point and ending up lower than the centroid. • As for the T-section, the shear centre is initially at the highest point (furthest from the centroid) and decreases gradually, intersecting the centroid and ending up lower than the centroid. • The H-section with upstanding plates offers itself as a section that has an envelope (gap) between the shear centre and centroid when the shear centre is above the centroid which is much lesser than the other sections. With the usage of excel spreadsheets, the sectorial coordinate approach is an efficient and accurate method to find shear centres and related section properties.
9

An investigation into the effects of early propping removal on the deflection of reinforced concrete beams

Rockstroh, Benjamin Andreas 31 January 2019 (has links)
In today’s fast paced construction industry, there is an ever present need to increase productivity and to complete projects as quickly as possible. Reinforced concrete is a popular and widely used construction material. However it has the unfortunate drawback in that the concrete requires time to set and gain sufficient strength before loads may be applied and the formwork and props can be removed. It is therefore desirable to keep propping times to a minimum. If the propping is removed too early, there is a risk of the member deflecting excessively and exceeding the maximum allowable limits, or in severe cases it could even lead to a structural failure or collapse. The SANS 2001 code provides recommended propping times for beams and slabs, which can be used as a guideline by building contractors and structural designers. These propping times present a universal approach, which does not consider all the factors that affect deflection. This simplified approach may be considered to be conservative as shorter propping durations could be possible without a loss in performance. The aim of this dissertation is to look into the effects of early propping removal on the longterm deflections of concrete members. This was done by modelling the deflection of a typical reinforced concrete beam at different ages of loading, using three code-based deflection calculation methods. The codes that were used are the South African National Standard (SANS), Eurocode (EC2) and American Concrete Institute code (ACI 318). A detailed literature-based investigation was conducted to determine the factors which affect deflection in reinforced concrete members, as well as the theory behind the code-based deflection calculation procedures. This was followed by the modelling of deflections using the abovementioned methods. Three case studies were performed to determine the effects of early propping removal under different scenarios. The first case study only deals with the effects of early age loading on long-term deflection. As an added point of interest, two different concrete mixes were used, made with two different types of cement. The second case study compares the effect that different levels of relative humidity have on the long term deflection at early ages of loading. Lastly, the effects of concrete strength on long-term deflections at early ages of loading was modelled. The results of the first case study indicated that a reduction in propping time is possible without causing excessive deflections. In the second and third case study is was observed that both the relative humidity and concrete strength respectively have an effect on the long term deflection and therefore also influence the propping time. The study concluded that based on the obtained estimated deflection values using the codebased methods, the propping times provided in the SANS 2001 code may in certain applications be conservative. According to the results obtained from the code-based deflection calculation procedures, it is possible to reduce the propping duration. It was suggested that an alternative method should be developed which would allow structural designers to determine the required propping time more accurately.
10

Fatigue Behaviour of CFRP Strengthened Reinforced Concrete Beams

James, Valontino Ruwhellon 15 September 2020 (has links)
The performance of reinforced concrete (RC) structures, such as bridges in the heavy haul industry, may be severely impacted by fatigue when subjected to repeated cyclic loading. Fatigue not only reduces load carrying capacity and serviceability limit states (SLS), but it can cause structural failure even when the components are subjected to low stress range cyclic loading. Corrosion damage exacerbates fatigue related problems as chloride induced pitting corrosion facilitates the formation and gradual propagation of cracks under cyclic loading. A common rehabilitation and retrofitting approach that involves patch repairing and fibre reinforced polymer (FRP) strengthening has proven effective to not only restore structural capacity, but also to enhance infrastructure service life. The structural repair process involves the replacement of deteriorated cover concrete with a less permeable patch repair mortar. The patch repair only restores durability of the structure; to restore or enhance structural capacity the repair process further involves bonding of FRP laminates. Particularly in the case of FRP's with a low elastic modulus, the design is often guided by serviceability limit states as opposed to ultimate limit states (ULS), resulting in an over-reinforced structural member. In addition, the reinforcement area of commercially available FRP strengthening may exceed the design requirements, especially at low levels of corrosion damage. In both the abovementioned considerations the design may result in an over-reinforced section. At the time when this researched was proposed, the effect of increasing damage extent on fatigue behaviour of over-reinforced RC beams was not clear and merited further investigation. A scientific experimental approach was developed to investigate the long-term performance of fifteen (15) full-scale 40MPa RC beams with dimensions 155x254x2000mm and ultimate capacity of 62.3kNm. Accelerated corrosion damage was induced in varied extents which included 450mm, 800mm, 1300mm and 1800mm length to a constant degree of 10% on all specimens. Specimens from each damage extent were patch repaired using SikaCrete214 and subsequently strengthened with externally bonded with SikaCarboDurS512 carbon fibre reinforced polymer (CFRP) laminates. Four-point bending monotonic loading tests were conducted on one (1) specimen from each damage extent. The results obtained from the quasi-static tests were used to determine two (2) cyclic loading stress ranges at which the remaining 2 specimens from each damage extent would be tested under. Under the 40% and 60% stress ranges four-point bending cyclic loading tests were carried out at a test frequency of 4Hz. Information was acquired on key performance indicators that included fatigue life, crack development, failure mode and stiffness degradation, where stiffness was assessed in terms of midspan deflection, composite material strains and neutral axis shift. Information on these parameters were collected using strain gauges, linear variable differential transducers (LVDT), DEMEC strain targets and digital image correlation (DIC). Ultimate failure loads under monotonic loading showed that despite having the highest degree of corrosion, the 450mm damage extent specimen had the highest failure load of 325kN. The failure load gradually reduced to 290kN as the damage extent was increased to 1800mm and the 0mm (control) specimen failed at the lowest load of 274kN. In contrast to the static behaviour, the specimen fatigue life enhanced by 106.3% as the damage extent was increased from 450mm to 1800mm. As expected, the 40% stress range tests yielded much longer fatigue lives than their 60% stress range counterparts. Furthermore, the experimentally obtained fatigue lives were compared to three fatigue life prediction models and the Helgason and Hanson model yielded the closest correlation with the experimental results. IV ABSTRACT Crack densities were found to increase with a longer fatigue life. An increase in damage extent was found to positively affect crack development and overall stiffness of the specimen during longterm fatigue testing. This finding was further substantiated by an assessment of midspan deflection, compression concrete strain and carbon fibre strain results, which all suggested a lower neutral axis and a lower stiffness reduction rate under fatigue loading as the damage extent was increased from 450mm to 1800mm. Furthermore, the tension concrete cracks propagated gradually during longer fatigue tests periods, while the tension steel and carbon fibre were comparably less affected by the resultant internal forces. Unfortunately, the neutral axis strain measurements using DEMEC targets were unable to assess the relative effect of an increase in damage extent as well as the compression concrete and carbon fibre strains were able to. During this experimental period, it was established that the laboratory layout was not conducive for carrying out the DIC process of long-term cyclic loading tests. The area in which testing took place did not adequately protect the camera against the environment and therefore required daily storage of the equipment. Regular movement of the camera for storage purposes introduced measurement inaccuracies which accumulated over longer test periods of up 20 days. However, for the short-term tests that did not require movement of the camera, the DIC process yielded favourable results. It was possible to capture the crack patterns early in the test period when the crack growth rate and development of new cracks was high using DIC. It was found that the high strain cracks coincided with the points of maximum vertical deflection (obtained through DIC) and eventual failure location of the specimen. The points of maximum deflection obtained from the DIC process were often not at midspan, which in the absence of the DIC process, would not have been possible to predict accurately. The results have shown that the specimens with the longer damage extents exhibit improved fatigue performance than their shorter counterparts. This revealed a stark contrast to their monotonic loading performance which favoured shorter damage extents. Furthermore, DIC holds potential to predict failure location more accurately than conventional approaches used for structural health monitoring (SHS).

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