Stay-in-place (SIP) formwork has been used as an alternative to the conventional formwork system. The systems are mainly assembled on site, hence simplifying the construction process and reducing the construction time as the removal procedure has been eliminated. SIP formwork systems can be divided into two main categories; structural and non-structural formwork, based on their contribution to resist applied loads. The structural formwork provides the same advantages as the non-structural formwork, in addition to its contribution to resist the applied loads. As a result, the cross section and the reinforcement of the structural member can be reduced. Recently, polyvinyl chloride (PVC) has been used as a stay-in-place formwork because of its lower cost compared to other materials, durability, and ease to assemble. The PVC SIP formwork consists of interconnected elements; panels and connectors that serve as permanent formwork for the concrete walls. In this study, the behaviour of the PVC encased reinforced concrete walls under eccentric compression loading was investigated. The variables in this study were the type of the specimen (PVC encased or control), the longitudinal reinforcement (4-10M or 4-15M rebars) and the eccentricity of the applied compression load (33.87 mm, 67.73 mm and 101.6 mm). Generally, the control walls (without PVC encasement) failed by yielding of the steel followed by crushing of the concrete, or by crushing of the concrete without yielding of the steel. For the PVC encased walls, buckling of the PVC occurred after the concrete crushed. The PVC encased specimens showed a higher peak load than their peer control walls. The effect of the PVC on increasing the ultimate capacity at a given eccentricity was more significant for the walls reinforced with 4-10M than the walls reinforced with 4-15M. For the lowest reinforcement ratio (4-10M), the PVC encased specimens showed an increase in peak load by 37.2% and 17.1% at an eccentricity of 67.73 mm and 101.6 mm, respectively. When the reinforcement was increased to 4-15 M, the increase in the peak load dropped at all eccentricities to 10%. For the vertical and the mid-span deflection, the PVC encased specimens and the control specimens showed the same values. Also, the test results showed an increase in the energy absorption capacity for the PVC encased specimens compared to the controls specimens, where the effect for the walls reinforced with 4-10M was higher than the walls reinforced with 4-15M at a given eccentricity. An analytical model was developed to predict the ultimate load capacity of the specimens taking into consideration the effect of the PVC on the load carrying capacity of the walls. The provision was derived based on the moment magnification factor method in which the effect of secondary stresses associated with the column deformations was taken into consideration. The calculated capacities of the PVC encased specimens showed a conservative error of 5.9% on average.

Ten reinforced-concrete continuous deep beams with openings were tested to failure. The main variables investigated were the shear span-to-overall depth ratio, and the size and location of openings. Two failure modes influenced by the size and location of web openings regardless of the shear span-to-overall depth ratio were observed. The normalised load capacity of beams having a web opening area ratio of 0.025 within exterior shear spans was approximately similar to that of their companion solid beams. Continuous deep beams having web openings within interior shear spans exhibited a higher load capacity reduction with the increase of the opening size, similar to simply supported deep beams with web openings. Formulae based on the upper bound analysis of the plasticity theory were proposed to predict the load capacity of continuous deep beams with web openings. Comparisons between the measured and predicted load capacities showed a good agreement.

Experimental research was conducted to investigate the influence of axial load and prestress on the shear strength of web-shear critical reinforced concrete elements. The ability of two design codes, the ACI code and the CSA code, to accurately predict the shear strength of web-shear critical reinforced concrete elements was investigated through two sets of experiments performed for this thesis, the panel tests and the beam tests. The experimental results indicated that the CSA code provided better predictions for the shear strength of web-shear critical reinforced concrete members subjected to combined axial force and shear force than the ACI code. A total of six panels, reinforced almost identically, were tested under different combinations of uni-axial stress and shear stress. In addition to the panel tests, a total of eleven I-shaped beams, with the same web thickness, were tested under different combinations of axial force and shear force. The parameters for these beams were the amount of longitudinal reinforcement, the amount of transverse reinforcement, and the thickness of the flanges. The beams were simply supported, but the loading geometry was specially designed to simulate the loading conditions in continuous beams near points of inflection. The experimental results from the panel tests and the beam tests followed a similar trend of variations. Both the inclined cracking strength and the ultimate shear strength were increased by compression and were reduced by tension. The specimens subjected to very high compression failed explosively without developing many cracks. The inclined cracking strength could be predicted with good accuracy if the influence of the co-existing compression on the cracking strength of the concrete and the non-uniform distribution of the stresses over the depth of the cross-section were considered. The strength predictions using the ACI code for these tests were neither accurate nor consistent. The ACI code was unconservative for members subjected to compression and was excessively conservative for members subjected to tension. In contrast, the strength predictions using the CSA code for these tests were generally conservative and consistent. The CSA code accurately predicted the response of specimens subjected to compression and was somewhat conservative in predicting the shear strength of specimens subjected to tension.

Over the past decade, extensive research has been conducted on the strengthening of reinforced concrete (RC) structures using externally bonded fibre reinforced polymer (FRP). More recently, near-surface mounted (NSM) FRP reinforcement has attracted an increasing amount of research as well as practical applications. In the NSM method, grooves are first cut into the concrete cover of an RC element and the FRP reinforcement is bonded inside the groove with an appropriate filler (typically epoxy paste or cement grout). The FRP reinforcement is either prestressed or non-prestressed depending on the required level of strengthening. In all cases, the bond between an NSM bar and the substrate material plays a key role in ensuring the effectiveness of NSM strengthening. The present work investigated experimentally the bond behaviour of non-prestressed and prestressed beams reinforced with near surface mounted carbon fibre reinforced polymer (CFRP) bars under monotonic and fatigue loading. Forty concrete beams were cast and tested in seven groups. The test variables considered in this study were: presence of internal steel reinforcement or not, the type of CFRP rod (spirally wound or sand coated) and the prestressing force (non-prestressed or prestressed). Twenty eight beams were strengthened with non-prestressed CFRP rods; fifteen beams without internal steel reinforcement and thirteen beams with internal steel. Ten beams with internal steel were strengthened with prestressed CFRP rods. The beams were tested in four point bending. In each group, one beam was loaded monotonically. The remaining beams were loaded under different fatigue load levels. The minimum load was kept constant for all beams at 10% of their monotonic capacity and the peak load was varied from one beam to another (denoted as a percentage of the peak load level). Twenty eight beams were strengthened with non-prestressed CFRP rods. Bond failures for the beams with and without internal steel, strengthened with CFRP rods and tested under monotonic or fatigue loads was by debonding between the CFRP rod and the epoxy that started at the loading point and as the load was increased or cycled, the debonding spread towards the support until failure occurred. A comparison of the fatigue life curves for the beams with and without steel, strengthened with CFRP rods revealed that the sand coated rod had better bond characteristics than the spirally wound rod (at the same load range the beam strengthened with sand coated rod had a longer life than the beam strengthened with spirally wound rod). Beams with internal steel, strengthened with CFRP rods and tested under fatigue loading failed in bond at high load levels (short fatigue lives) and by rupture of the steel rebar at low load levels (long fatigue lives). Ten beams with internal steel were strengthened with prestressed CFRP rods. The CFRP rods were prestressed to a force of 62 kN which corresponds to 45% and 40% of the monotonic capacity of the spirally wounded and sand coated rods, respectively. Almost all the beams with internal steel that were strengthened with prestressed CFRP rods failed by slipping between the CFRP rod and the epoxy that started at the support and propagated inwards towards the loading point. The exception to this was the beam strengthened with prestressed sand coated rod and tested under monotonic loading that failed by debonding between the CFRP rod and the epoxy that started at the loading point and propagated towards the support. Comparing the load range (kN) versus life curve for the beams with steel, strengthened with prestressed spirally wound and sand coated rods that failed in bond, shows that the beam strengthened with sand coated rod has longer fatigue lives than beam strengthened with spirally wound rod. A model was used to describe the progress of the debonding crack until excessive slipping occurred. The model predicted the number of cycles until excessive slipping between the CFRP rod and the epoxy occurred and the forces in the CFRP rod at all locations in the shear span at the onset of failure with reasonable accuracy.

This research study examined the effect of corrosion of web reinforcement (stirrups) on the shear behaviour of slender reinforced concrete (RC) beams. The experimental program consisted of seventeen slender shear-critical RC beams: five uncorroded and twelve corroded beams. The test variables included: 1) corrosion level (0%, 7.5% and 15%); 2) type of stirrups (smooth and deformed); 3) stirrup diameter (D6, D12 and 10M); 4) stirrups spacing (100mm and 200mm); and 5) the presence of CFRP repair. The corroded beams had their stirrups subjected to corrosion using an accelerated corrosion technique and the mass loss in the stirrups was estimated based on Faraday’s law. All of the beams were monotonically tested to failure in three point bending. The corrosion cracks formed were parallel to the locations of stirrups as evidence of the corrosion damage in the corroded beams. The maximum decrease in the ultimate shear strength ranged from 11% to 14.4% for beams with high corrosion level of 15.6% mass loss. At a low corrosion level (4.39% mass loss), the shear strength of beams with smooth stirrups increased up to 35% due to the enhancement of shear friction at the concrete-corroded stirrups interface. The stiffness of the corroded beams was enhanced in comparison to the control beams. The ultimate deflection of the corroded beams was decreased up to 25% in comparison to the control beams. The CFRP repair increased the shear strength by 36% and improved the overall stiffness by 39% in comparison to the corroded unrepaired beams. All of the unrepaired beams failed in diagonal tension splitting, while the CFRP repaired corroded beams failed in diagonal tension splitting in addition to debonding of the FRP or concrete cover delamination. The actual corrosion mass loss results were in good correlation with Faraday’s law for the D12 and 10M stirrups. Poor correlation between actual and estimated mass loss was obtained for D6 smooth stirrups, possibly due to errors in the impressed corrosion. iv The analytical model used the modified compression field theory (MCFT) to predict the shear strength of uncorroded and corroded slender RC beams. In the corroded beams, two reduction factors were added to the MCFT model including the mass loss factor and the effective web width. Predictions based on the model revealed that the control beams gave a very good correlation with the ratio of experimental to predicted values that ranged from 0.94 to 1.02. On other hand, the ratio of experimental to predicted strength in the corroded beams ranged between1.06 to 1.4. The poor correlations were obtained for the beams with the D6 smooth stirrups. This study demonstrates that corrosion of web reinforcement can have a detrimental effect on the shear strength and ductility of slender shear-critical RC beams. The experimental results and analytical approach will be very useful for practicing engineers and researchers dealing with corrosion damage in slender RC members.

This thesis reports a research of the corrosion mechanism and corrosion rate of steel reinforcement in concrete. Experimental results are presented to compare the corrosion behaviours of steel reinforcement in two blended-cement concretes in seawater. The experimental program included a study of the influence of crack width on macrocell corrosion, an investigation of the procedure for the determination of polarisation curves of steel in concrete and, an evaluation of the corrosion rate of steel in concrete and the influence of crack width as determined by a new polarisation curve analysis. A mechanism is proposed to interpret the different influences, in both the short and long term, of concrete crack width on the macrocell corrosion rate. This mechanism is based on the finding that the corrosion-spread phenomenon is caused by polarisation effects. An oxygen-depletion mechanism is also proposed to explain the much lower macrocell corrosion rate in the slag cement concrete than that in the flyash cement concrete. The procedure for polarisation testing of steel in concrete is found to be critical to obtaining correct polarisation curves. A twotest procedure is verified to be an appropriate procedure and used in this investigation. Experimental polarisation curves of steel in concrete are found to be very different to those expressed by the kinetic Butler-Volmer equation and, this is considered to be a result of the influence of the passive film on the steel surface in concrete. An empirical polarisation formula is developed and its interpretation is based on the postulation of two parallel kinetic processes occurring at the steel/passive-film/concrete interface; one is the active corrosion process and the other is the film growth/dissolution process. The formula is used to model experimental polarisation curves of steel in concrete through curvefitting analyses. Good curve-fitting results are obtained between the polarisation test curves and model curves. The results are used for evaluation of the corrosion rate and Tafel behaviours of steel in the two concretes and for assessment of the influence of crack width on the corrosion rate within the crack zone.

Errata inserted / Bibliography: leaves 336-358 / xxiii, 358 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1990

Current codes of practice for the design of tall concrete chimneys provide conservative aseismic design guidelines in high seismic regions. A lack of experimental data related to the cyclic behaviour of chimney structures to severe earthquake excitation has resulted in the assumption that such structures are brittle and must be designed in the elastic range. This design approach results in expensive structures and is not consistent with the design philosophy commonly adopted for general structure which permits some inelastic response at the ultimate limit state event. A research program funded by the CICIND organisation has been undertaken to investigate the inelastic cyclic behaviour of tall reinforce concrete chimneys using both experimental and analytical techniques to determine whether the behaviour is brittle or ductile. The research has been divided into three parts; (a) overview of earthquake ground motions, review of the earthquake response of structures and review of chimney design code provisions, (b) detailed description of experimental research examining the cyclic behaviour of chimney sections and (c) development of an aseismic design and analysis procedure for reinforced concrete chimneys including code recommendations. (For complete synopsis open document)

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 25, 2008) Includes bibliographical references (p. 52-54).

Thesis (M.S.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 31, 2008) Includes bibliographical references (p. 48-49).