No description available.

No description available.

No description available.

No description available.

Reinforced concrete (RC) is extensively used in the construction industry. It is particularly used to guarantee that infrastructure assets around the world last for multiple years whilst ensuring that the structural integrity and serviceability of the structure is maintained. However, in practice countless RC constructions are failing prematurely due to a large number of factors of which the corrosion of steel embedded within concrete is the most significant (Matthews et al., 2003). Steel corrosion is particularly pernicious to concrete due to the expansive nature of the corrosion by-products formed, which commonly leads to cracking and spalling. One of the most common methods adopted in the rehabilitation of corrosion damaged concrete is the patch repair procedure. However, in practice this method has shown to often be unreliable as a consequence of the widespread occurrence of shrinkage cracking and poor substrate-patch adhesion leading to debonding of the patch repair. From a practical point of view, such failed repair systems essentially restore the repaired concrete back to a deteriorated state. The underlying cause of poor durability in patch repairs is attributed to a range of reasons including, the lack of understanding of the substrate-patch composite system and the limited availability of appropriate design standards. Furthermore, there is a lack of understanding in the repair industry on the critical material properties actually required for durable patch repairs. There is a common belief that repairing concrete with specialised proprietary repair materials would guarantee durability. However the widespread premature failure of patch repairs conducted using such materials has proven the contrary. A proper patch repair process includes treatment of the corroded steel, adequate substrate surface preparation, installing sacrificial anodes (at least for chloride contaminated concrete) and surface coating. In principle, if this process is correctly followed then the material requirements for a durable, non-structural repair would be to fill in the cavity created by removing contaminated concrete, resist shrinkage induced cracking and/or debonding and provide protection against chloride ingress (in chloride environments). The material used for patch repairs could be any appropriate repair material and it does not specifically need to be a specialised cementitious repair mortar. This dissertation presents an understanding of the materials and issues concerning the durability and serviceability of patch repairs, with the aim of identifying alternative non-structural patch repair materials for the durable repair of corrosion-damaged concrete structures. The potential patch repair materials studied in this dissertation were rubberised waterproofing bitumen, polymer (copolymer of vinyl acetate and ethylene) with 5% cement replacement and 60%, 80% and 100% fly ash (FA) mortar. Patch repairs were conducted on substrate moulds to test application and observe cracking/debonding occurrence. Furthermore, compressive strength, durability index, accelerated drying shrinkage, restrained shrinkage, workability and SEM tests were conducted. It was concluded that the 60% FA repair material had the best overall performance with the polymer-cement concrete exhibiting good bonding and crack resistance properties. This research established that innovative alternative repair materials such as a 60% FA or polymer-cement concrete material, can be developed for non-structural patch repairs with improved long-term performance relative to conventional materials. The research has further provided a foundation for the development and design of durable repair mortars by identifying the principal material performance properties required of such materials.

The objective of this study was to determine whether rigid inclusions are suitable for reinforcement of the foundation of a caisson quay wall functioning as a container terminal. Apart from their brittle behaviour under lateral loading, rigid inclusions are well suited to the large uniform loads and stringent post-construction deflection tolerances associated with container terminal structures. Their inherent strength and stiffness means they have certain advantages over other stiffening columns commonly used for ground reinforcement in port expansion projects. Their mechanical properties allow construction to unrestricted heights at any construction rate and, in theory, RIs can be applied to all soil types. Additionally the locations of many ports coincide with rivers, deltas and estuaries which are associated with poor soil conditions often requiring ground improvement. Their suitability is of practical significance to port planners and engineers who are faced with the challenge of providing satisfactory foundation performance that is cost effective. The addition of RI ground reinforcement for this structural application would allow for greater flexibility in meeting these challenges. The literature review for this study was broad in its scope with emphasis placed on describing the mechanics of the problem, analysis methods and suitable installation methods for execution in the marine environment. One of the key outcomes of the literature review was identifying the problem of lateral loading due to "free-field" lateral ground movements. In light of this, suitable strategies for limiting and accommodating lateral loading of the RIs were proposed. A numerical study of the proposed ground improvement scheme was undertaken using the 3D finite element method. The key model outputs were caisson deflections and RI forces, moments and stresses, for the various simulated construction phases up to operational conditions. The model results were assessed in terms of the key foundation performance criteria which were related to STS crane rail tolerances and limiting tensile stresses in the RIs. This study found that for a firm clay subsoil condition the proposed RI ground reinforcement scheme met the foundation performance criteria for this structural application provided (i) strategies to limit lateral loading were implemented and (ii) the RIs were reinforced over the length where they were not fully compressed. While this study provided insights into the behaviour of RIs for this structural application, ultimately suitability is a function of range of factors, in addition to the limited technical performance criteria derived for this study.

The focus on the condition and performance of existing structures has increased due to the growing number of structures approaching or exceeding their design life. The challenges associated with the assessment of existing structures include deterioration, changes in loading conditions, changes in the structures function or the structure reaching the latter portion of its designed service life. In order for authorities to better determine how to deal with existing structures, there must be a coherent means of determining, measuring and benchmarking the current condition and performance of the structure. The current study proposes and demonstrates the integration of a visual based condition assessment with vibration based assessment techniques for railway bridges. The methodology suggests a systematic visual assessment combined with the development of a finite element model which is calibrated by using modal parameters ascertained from vibration based testing. The bridge which was used as a case study was the Kalbaskraal Railway Bridge located in Malmesbury. The proposed methodology consists of the following steps: 1) Initial Assessment 2) Development of a Finite Element Model 3) Detailed assessment and Ambient Vibration Field Testing 4) Analysis of Modal Parameters 5) Calibration of FEM using Modal Parameters 6) Setting up Load Configurations 7) Assessment of structural response 8) Assessment of Serviceability limit state of bridge The overall outcome of the study yielded an effective result in that the conclusions drawn from the outcomes of the methodology correlated well with previous studies on the bridge. The structure under its current operational load of 16ton/axle wagons performed within the allowable serviceability limit state. A proposed increase to 22.5ton/axle loads identified that the bridge would be performing on the boundary or above the allowable serviceability limit state and that retrofitting may have to be considered for the bridge to effectively support the additional load. The results derived from this study can be extremely valuable in the bridge management process as the information on the condition of the bridge can aid bridge authorities in their decision making processes.

The process of pile driving has been a commonly used method for the installation of deep foundations in Central Florida due to the soil conditions that consist mainly of medium-dense silty sands. Pile driving can generate large vibration levels that might potentially trigger ground deformations in the surrounding soils and cause damage on nearby structures. Currently, design and construction standards provide guidance in terms of ground vibration levels expected during pile driving and establish vibration thresholds to avoid damage on important infrastructure. However, little insight has been given into the amount of ground deformations that soils experience due to pile driving induced vibrations. This phenomenon becomes important when repetitive and cumulative loading cycles are applied in sandy soils. The main goal of this thesis is to investigate numerical modeling alternatives capable of predicting ground deformations caused by pile driving performed in Central Florida soils. Field data obtained from different construction sites in Central Florida are used to understand the expected ground deformations and their relationships with ground vibration levels. Common construction practices in the area are also analyzed from the reported field data. Two numerical modeling approaches previously used in the literature are compared with data measured in the field to determine the most suitable alternative to numerically analyze and predict ground deformations. Subsequently, a numerical study of the effects of the different variables involved in this problem on expected ground vibrations and deformations is presented. These variables include the type of pile and its dimensions, the driving hammer and its transmitted energy to the pile, and the dynamic properties of the soils in terms of attenuation characteristics and densification potential. It is concluded that in cases where vibration levels comply with the thresholds defined by the Florida Department of Transportation (FDOT) large ground deformations can still occur depending on the above-mentioned site-specific variables. In terms of numerical modeling alternatives, a continuous modeling approach offered a better estimation of the stress field generated by pile driving than a discontinuous approach. This allows for better determination of the strains within the soil continuum leading to better ground deformation predictions.

Fine-grained soils are responsible for most site settlements through a time dependent process known as consolidation. The magnitude of consolidation is quantified with three terms: the recompression and compression indices, referred to as the soil's compressibility indices, and preconsolidation pressure. The ideal methods to estimate these parameters are direct measurements from lab or in-situ field tests, other method include estimation from experience or from correlations to soil parameters. This study refines correlations between compressibility indices and index properties as previously researchers and soil mechanics suggest a strong correlation exists. This study also suggests a correlation to CPT parameters as this test is commonly used and has the potential to provide continuous and repeatable compressibility profiles. It was found that compressibility is strongly related to the CPT pore pressure reading for soils with pronounced colloidal properties. It was also found that the correlation to moisture content performed better than all previous recommended models.

Stadiums, pedestrian bridges, dance floors, and concert halls are distinct from other civil engineering structures due to several challenges in their design and dynamic behavior. These challenges originate from the flexible inherent nature of these structures coupled with human interactions in the form of loading. The investigations in past literature on this topic clearly state that the design of flexible structures can be improved with better load modeling strategies acquired with reliable load quantification, a deeper understanding of structural response, generation of simple and efficient human-structure interaction models and new measurement and assessment criteria for acceptable vibration levels. In contribution to these possible improvements, this dissertation taps into three specific areas: the load quantification of lively individuals or crowds, the structural identification under non-stationary and narrowband disturbances and the measurement of excessive vibration levels for human comfort. For load quantification, a computer vision based approach capable of tracking both individual and crowd motion is used. For structural identification, a noise-assisted Multivariate Empirical Mode Decomposition (MEMD) algorithm is incorporated into the operational modal analysis. The measurement of excessive vibration levels and the assessment of human comfort are accomplished through computer vision based human and object tracking, which provides a more convenient means for measurement and computation. All the proposed methods are tested in the laboratory environment utilizing a grandstand simulator and in the field on a pedestrian bridge and on a football stadium. Findings and interpretations from the experimental results are presented. The dissertation is concluded by highlighting the critical findings and the possible future work that may be conducted.