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Autoclaved aerated concrete (AAC) is a lightweight cellular building material. In Spring 2008, an experimental study was conducted at The University of Texas at Austin to evaluate the load-deflection behavior and capacity of six different factory-reinforced AAC lintel groups. The results the test program are used to evaluate the shear design provisions of ACI 523.4R “Guide for Design and Construction with AAC Panels”. / text

The University of Aberdeen has conducted research into ground anchorage systems since the early 1980's. During this time, the non-destructive GRANIT system (GRound ANchorage Integrity Testing) has been developed for anchorages in rock. The system is based on observing the dynamic response from anchorages to which an impulse of a known intensity has been applied. This technique has been proven to be a reliable system to assess the integrity of rock anchorages, which is then used as a base to study the integrity of soil anchorages. This research aims to implement a non-destructive testing system at small scale size and full scale stress levels by means of centrifuge modelling at the University of Dundee. Accordingly, centrifuge modelling was undertaken to monitor and assess the dynamic response of soil anchorages installed in dry sand reinforcing a retaining wall in 3x3 anchorage array sets, subject to different post tension levels within different bonding ratios and different inclinations. In order to perform non-destructive testing, an In-flight Robotic Manipulator, previously developed, was used to apply a post tension load followed by an impact load to the anchorage head to obtain the dynamic response of the system. Anchor frequency response signatures were then evaluated in order to validate the consistency of results obtained. The practical importance of this research is that non-destructive testing may be usable to assess the soil anchors integrity to define the relationship between both anchor load and geometrical characteristics with frequency response accomplished using centrifuge modelling. This research presents a further development of the physical model in which additional instrumentation is included in order to obtain load/deflection information of the anchor head, which has been proven crucial for monitoring load on rock anchorage. Additionally, load distributions along scaled model soil anchors are measured and found to reduce gradually within the fixed length, similarly as it was reported for the fixed length of rock anchorages. Furthermore, a lumped parameter model for a single soil anchorage was adapted to investigate the dynamic response under the same physical and geometrical characteristics studied during centrifuge modelling. Mode shapes helped to understand the origin of some of the frequency modes present in the frequency response of the centrifuge results. The results from the numerical and centrifuge models were compared and good agreement was observed. Soil anchorage does not show as much frequency shift as was observed for rock anchorages under different post tension load, suggesting that the bonding strength of the fixed length with the surrounding ground plays an important role on the dynamic response of the system. The accomplishment of the assessment of soil anchorage can not be exclusively judged on its ability to diagnose controlled changes under centrifuge and numerical modelling. Therefore a preliminary phase to assess a soil anchorage under field conditions was carried out deploying the GRANIT system. This research showed that the GRANIT non-destructive testing technique has potential for use in soils, but that the results are not as well defined as in rock, necessitating more careful characterization of each anchorage signature response.

The Åreskutan nappe complex consists of the partly molten rock migmatite, which originates from the subduction formed by the collision of continents Baltica and Laurentia. It is a so-called hot nappe, which has been deeply buried in the subduction zone, based on findings of high-pressure minerals in the migmatitic gneiss. As the nappe returned to shallower depths the rock was partially molten during the subsequent exhumation as the lithostatic pressure decreased. Tectonic forces led to thrusting of the nappe towards the east and the building of mount Åreskutan. It is generally accepted that the shear zone between the migmatite of the Åreskutan Nappe and the underlying Lower Seve Nappe is a mylonitic shear zone, but the question of whether similar shear zones can be found at other sites in the migmatite complex has now been raised. In this project two major shear zones have been identified and shear direction has been determined after detailed geological mapping. Many small shear zones have also been identified, but their sense of shear direction was more difficult to determine. The two major shear zones identified have been labelled the Eastern Major Shear Zone and Western Major Shear Zone. In these shear zones the original migmatite appearing on Åreskutan is deformed and sheared with a top to the east sense of shear. The strongest evidence for determining the shear sense are garnets found mantled by micas in a sigma-type shear microstructures, found during microscope analysis. A grade of mylonitization can be seen in the mineral microstructures, with the most fine-grained matrix in the centre of the shear zones. It indicates that ductile deformation dominates, even though some minerals tend to break in a brittle manner.

The objective of this research is the evaluation of shear behavior of full-scale reinforced concrete T-beams strengthened with carbon fiber reinforced polymer (CFRP) sheets and CFRP anchors. Although the CRFP material has high tensile strength, premature failure due to debonding CFRP sheets prevents utilizing that strength. The use of CFRP anchors prevents this failure, so the CFRP sheets are able to reach ultimate strain. The current shear design is based on plasticity, which assumes that all steel (ductile material) stirrups, across the critical section yield at ultimate. However the strain in the CFRP (brittle material), is essential to estimate the shear contribution of CFRP. To evaluate the validity of CFRP strengthening for shear, 24 tests were conducted with several parameters including shear-span-to-depth ratio, depth of beams, different transverse reinforcement ratios, and the layout of CFRP strips. In addition, a simple shear behavior model was developed to explain the differences between ductile and brittle material. From test observation, the use of CFRP anchors resulted in U-wrap application to perform like continuous wrapping which implies that a CFRP strip reached rupture strain because the anchors prevented debonding failure. However, all FRP strips did not rupture simultaneously because the strain distribution across a critical crack was not uniform. The average strain across the critical crack was about 0.005. Therefore a conservative value of effective strain (0.004) was selected for design purposes. In addition, when a beam is strengthened with CFRP, interactions between the contributions of the CFRP, steel or concrete must be taken into account. Factors ka, ks, and kf were introduced in the proposed shear design equations. Factor ka reflects the change in the material contributions as the shear span to depth ratio (a/d ratio) changes in deep beams. Factors ks and kf account for the change in steel or CFRP shear contribution due to the change in the critical crack angle as well as the interactions between the steel and FRP transverse reinforcement. As the amount of either steel or FRP material increase, the efficiency of the other material decreases. / text

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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