Civil and Environmental Engineering electronic theses and dissertations (MU)
Permanent URI for this collection
The items in this collection are the theses and dissertations written by students of the Department of Civil and Environmental Engineering. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
Browse
Recent Submissions
Item Improvement of glass curtain wall connections subjected to quasistatic and dynamic loading(University of Missouri--Columbia, 2024) White, Donald Andrew; Salim, Hani[EMBARGOED UNTIL 12/01/2025] Extreme events, such as explosions, can significantly compromise the structural integrity of buildings. Currently, glass curtain wall (CW) systems are widely used as façade solutions in government, educational, medical, and commercial structures. However, advancements in manufactured and improvised explosive devices (IEDs) have resulted in a rise in explosive incidents and related injuries in recent years. Despite their widespread use, there has been limited experimental research on full-scale CW system connections. This study aims to address this gap by developing blast design and retrofit connection recommendations for modern curtain walls through quasi-static and dynamic testing of curtain wall mullions and connections. Several studies were conducted to assess the conventional design of glass curtain wall connection and explore ways to enhance the connections for improved mechanical properties. The initial test involved a quasi-static evaluation of a 1219.2 mm (48 in) long mullion specimen. The widely used conventional T anchor connection was tested first, followed by five additional strengthening techniques. These techniques included: a through bolt connecting the mullion and T anchor, a steel C channel insert, a steel C channel insert with through bolts, aluminum and steel bearing angles, and a closed T anchor stem design. Each of these designs was compared to the conventional model to evaluate the mechanical advantages provided by the strengthening techniques. Preliminary experimental work for dynamic loading was initiated on both the conventional and strengthened connections. A drop weight machine was used to apply dynamic loads to the 1219.2 mm (48 in) long mullion specimens, utilizing piezoelectric load cells to measure the reactions at each end and the load applied at the midspan of the mullion. These results were used to help develop a dynamic increase factor (DIF) to help correlate the responses from the quasistatic testing to the dynamic testing in terms of peak load. Finally, experimental work was conducted on full-scale mullion specimens subjected to quasi-static loads. These samples demonstrated the behavioral differences between flexural failure and shear failure in the mullion specimens. The results from these tests varied from those of the 1219.2 mm (48 in) long mullion specimens. Load and deflection data were collected for all tests, which are detailed in the results section below. Understanding how strengthening the connections in a full-scale glass curtain wall system can improve energy absorption is crucial for designing against catastrophic events like blast explosions. This paper discusses these key characteristics and offers practical insights for achieving better performance than conventional designs.Item Elastoplastic buckling of doubly curved unstiffened shells(University of Missouri--Columbia, 1965) Todd, William W."The calculation of reliable values for the buckling pressure of thin shells has become very Important in recent years. The increased necessity and usage of lighter weight components in missile propulsion systems has required more precise calculations to avoid stability problems and to increase economic feasibility. Modern architectural forms are likewise pointing to the need for more exact design formulae. Many solutions to the problem of stability of unstiffened shells from the purely elastic standpoint have been proffered."--Introduction.Item The pseudo-elastic criterion for buckling of spherical shells(University of Missouri--Columbia, 1967) Todd, William Warren; Buchert, Kenneth P."The thin shell has long been recognized as a structurally efficient means of resisting applied external loads owing to the translation of these loads into direct stresses. Flexural stresses in such structural elements often become significant only after axial strains are of considerable magnitude. The unstiffened thin shell has found wide applicability in various areas, particularly in the aircraft, missile, heavy plate, and atomic energy industries. In fact, whenever a structure or structural element is required either to provide load resistance over relatively large clear areas or whenever the dead weight of the element is of primary concern, the thin shell has been found to be most desirable. General construction has Incorporated the shell into a multitude of long-span, low-obstruction designs such as auditoriums, sports complexes and wind tunnels. The use of shells in ship and submarine hulls is well known. Likewise, in recent times, the missile industry, requiring the lightest possible structural elements able to resist extremely high pressure and temperature differentials, has used the thin shell in many cases. Extensive work has been done in the general area of shell theory and particularly the stability of thin shells. However, recent catastrophic failures of domes at Budapest, 2 Bucharest, Fargo, and the collapse of space boosters have Indicated a basic deficiency in the theoretical work which has been done. As pressure and temperature differentials become larger and longer spans are required, the need to Improve the developed theories becomes obvious. The stability of thin shells is of a very perplexing nature. The theory of elasticity, from which the basic relations for the treatment of rod, plate, and shell stability are derived, yields very good agreement between theory and experiment for columns and plates; but not for spherical shells. Theoretical buckling pressures for these shells may be as much as three or four times larger than the experimentally obtained value. In fact, experimental results for seemingly Identical shells may be found to differ over a broad range. The buckling phenomenon associated with thin shells also differs quite radically from that of short columns and plates. The latter elements often demonstrate a gradual failure and are able to support the critical buckling load after buckling and even resist additional load. On the contrary, thin shells demonstrate a very sudden failure and the load carrying capacity drops sharply to a fraction of the critical load after this critical value is reached. Previous investigation into the nature of spherical shell stability has necessarily been divided into two broad areas: (a) deep spherical shells for which the rise 3 to span ratio is considered large and (b) shallow spherical caps for which this ratio is relatively small. Most investigators arbitrarily designate a rise to span ratio of one-eighth as the dividing line between deep and shallow spherical shells. However, much confusion has arisen when the theoretical relations obtained for so-called deep shells have been used in the investigation of shallow spherical caps. A brief historical resume is presented herein and illustrates the necessity of radically different treatment for the two very broad categories of spherical shells."--Introduction.Item Toward automated sidewalk pavement condition elevaluation utilizing bike mounted camera(University of Missouri--Columbia, 2024) Dodge, Jacob Aaron; Adu-Gyamfi, YawThis study proposes a methodology to expedite sidewalk condition assessments and develops a numerical rating system for ranking concrete sidewalk conditions. The goal is to identify hazardous and distressed areas within sidewalk networks to better address maintenance needs and accessibility concerns. The methodology introduces an automated Concrete Sidewalk Condition Index (CSCI) based on observable surface distresses and detects other hazards based on compliance with standards. Surface distresses are captured by an off-the-shelf camera mounted on a bicycle to collect video data of the sidewalks of interest. Images extracted from these videos fine-tune a lightweight deep learning object detection model (YOLOv8m) to detect and categorize various concrete sidewalk pavement distresses (shattered slab, transverse cracks, scaling, heavy scaling, and corner breaks) solely from RGB images. Inertial sensors within the camera are used to detect vertical faults, quantify their severity, and flag tripping hazards. Additionally, cross slopes and running slopes can be captured using the inertial sensors within the camera. The sidewalk pavement conditions extracted from the low-cost camera are weighted and fused to develop a numerical rating for the CSCI. Sidewalk sections CSCI scores and other factors of compliance can then be used to produce visual aids of sidewalk conditions (such as heatmaps) and help make maintenance related decisions. The results demonstrate the effectiveness of the proposed methodology with the object detection model achieving a mean average precision at 50 percent intersection over union (mAP50) of 97.6 percent on the validation data, a detection accuracy of 87.7 percent for flagging tripping hazards, an accuracy of nearly 97 percent for detecting running slopes, and an accuracy of 97.5 percent for detecting cross slopes. A case study utilizing the methods is provided.Item Variability of the horizontal-to-vertical spectral ration (hvsr) method in urban areas(University of Missouri--Columbia, 2024) Smith, Braydon Andrew; Rosenblad, BrentThe Horizontal-to-Vertical Spectral Ratio (HVSR) method is widely employed in geotechnical investigations due to its non-intrusive approach for determining subsurface characteristics such as sediment thickness, bedrock depth, and seismic site response. The primary objective of this paper is to provide both quantitative and qualitative assessments of four potential factors influencing HVSR variability in urban environments: (1) in-situ instrumentation surface coupling (concrete vs. grass), (2) the effect of strong, nearby noise sources on in-situ instrumentation, (3) proximity to buildings, and (4) the influence of time- of-day with respect to building proximity. A total of 126 HVSR measurements across 16 locations at the University of Missouri-Columbia were analyzed, with an emphasis on influences on HVSR variability in urban environments. The results show minimal variability between HVSR measurements conducted simultaneously on concrete and grass surfaces. This finding was in agreement with commonly used HVSR acquisition guidelines but contradicted more recent guidelines provided by an HVSR equipment manufacturer. Furthermore, data indicated that concrete surfaces exhibited greater variability in noisy environments, such as construction zones, possibly due to reduced attenuation of construction vibrations, whereas grass surfaces yielded more consistent measurements. Proximity to buildings was identified as a significant factor contributing to variability, with measurements taken within 50 feet of buildings typically producing low-quality HVSR results, likely due to building-induced vibrations. Time-of-day effects were found to be less significant, with ambient noise levels having a greater impact on measurement quality than noise from building occupancy itself. HVSR frequency peaks identified from manual inspection methods improved result accuracy when compared to automated picking of the highest HVSR peak. The study highlights the importance of considering site-specific conditions and incorporating human oversight in HVSR analysis, particularly in urban environments. Key findings include: (1) concrete is a reliable surface for HVSR measurements, indicating that data acquisition does not need to be exclusively conducted on grass, (2) acquisition near strong construction noise sources can yield accurate HVSR results, and does not necessarily need to be avoided, (3) maintaining a sufficient distance from buildings (preferably >50 ft) will reduce variability in HVSR results (4) manual identification of HVSR peaks can provide improved results over automated picks in difficult environments, and (5) measurements near building sites are best conducted during times when ambient noise levels are high. These insights contribute to the refinement of HVSR guidelines and enhance its application in urban geotechnical and geophysical investigations. This study also contributes to the refinement of HVSR guidelines, offering recommendations for mitigating variability caused by urban factors and suggesting avenues for future research, including exploring the effects of building height, subsurface complexity, and azimuthal variability on HVSR measurements.