The need for a simple but rigorous seismic assessment procedure to predict damage to reinforced concrete buildings during a seismic event has been highlighted following the Canterbury Earthquake sequence. Such simplified assessment procedure, applied to individual structure or large building inventory, should not only have low requirement in terms of input information and involve straightforward analyses, but also should be capable to provide reliable predictive results within short timeframe. This research provides a general overview and critical comparison of alternative simplified assessment procedures adopted in NZSEE 2006 Guidelines (Assessment and Improvement of the Structural Performance of Buildings in Earthquakes), ASCE 41-13 (Seismic Evaluation and Retrofit of Existing Buildings), and EN: 1998-3: 2005 (Assessment and Retrofitting of Buildings). Particular focus is given to the evaluation of the capability of Simplified Lateral Mechanism Analysis (SLaMa), which is an analytical pushover method adopted in NZSEE 2006 Guidelines. The predictive results from SLaMa are compared to damages observed for a set of reinforced concrete buildings in Christchurch, as well as the results from more detailed assessment procedure based on numerical modelling. This research also suggests improvements to SLaMa, together with validation of the improvements, to include assessment of local mechanism by strength hierarchy evaluation, as well as to develop assessment of global mechanism including post-yield mechanism sequence based on local mechanism.
During the recent devastating earthquakes in Christchurch, many residential houses were damaged due to widespread liquefaction of the ground. In-situ testing is widely used as a convenient method for evaluating liquefaction potential of soils. Cone penetration test (CPT) and standard penetration test (SPT) are the two popular in situ tests which are widely used in New Zealand for site characterization. The Screw Driving Sounding (SDS) method is a relatively new operating system developed in Japan consisting of a machine that drills a rod into the ground by applying torque at seven steps of axial loading. This machine can continuously measure the required torque, load, speed of penetration and rod friction during the test, and therefore can give a clear overview of the soil profile along the depth of penetration. In this paper, based on a number of SDS tests conducted in Christchurch, a correlation was developed between tip resistance of CPT test and SDS parameters for layers consisting of different fines contents. Moreover, using the obtained correlation, a chart was proposed which relates the cyclic resistance ratio to the appropriate SDS parameter. Using the proposed chart, liquefaction potential of soil can be estimated directly using SDS data. As SDS method is simpler, faster and more economical test than CPT and SPT, it can be a reliable alternative in-situ test for soil characterization, especially in residential house constructions.
Access to clean and safe drinking water is a fundamental human requirement. However, in many areas of the world natural water sources have been impacted by a variety of biological and chemical contaminants. The ingestion of these contaminants may cause acute or chronic health problems. To prevent such illnesses, many technologies have been developed to treat, disinfect and supply safe drinking water quality. However, despite these advancements, water supply distribution systems can adversely affect the drinking water quality before it is delivered to consumers. The primary aim of this research was to investigate the effect that water distribution systems may have on household drinking water quality in Christchurch, New Zealand and Addis Ababa, Ethiopia. Water samples were collected from the source water and household taps in both cities. The samples were then tested for various physical, chemical and biological water quality parameters. The data collected was also used to determine if water samples complied with national drinking water quality standards in both countries. Independent samples t-test statistical analyses were also performed to determine if water quality measured in the samples collected from the source and household taps was significantly different. Water quality did not vary considerably between the source and tap water samples collected in Christchurch City. No bacteria were detected in any sample. However, the pH and total iron concentrations measured in source and tap water samples were found to be significantly different. The lower pH values measured in tap water samples suggests that corrosion may be taking place in the distribution system. No water samples transgressed the Drinking Water Standards for New Zealand (DWSNZ) MAVs. Monitoring data collected by the Christchurch City Council (CCC) was also used for comparison. A number of pH, turbidity and total iron concentration measurements collected by the CCC in 2011 were found to exceed the guideline values. This is likely due to structural damage to the source wells and pump-stations that occurred during the 2011 earthquake events. Overall, it was concluded that the distribution system does not adversely affect the quality of Christchurch City’s household drinking water. The water quality measured in samples collected from the source (LTP) and household taps in Addis Ababa was found to vary considerably. The water collected from the source complied with the Ethiopian (WHO) drinking water quality standards. However, tap water samples were often found to have degraded water quality for the physical and chemical parameters tested. This was especially the case after supply interruption and reinstatement events. Bacteria were also often detected in household tap water samples. The results from this study indicate that water supply disruptions may result in degraded water quality. This may be due to a drop in pipeline pressure and the intrusion of contaminants through the leaky and cross-connected pipes in the distribution network. This adversely affects the drinking water quality in Addis Ababa.
The effects of soil-foundation-structure interaction (SFSI) have been a topic of discussion amongst the structural and geotechnical community for many decades. The complexity of the mechanisms, as well as the need for inter-disciplinary knowledge of geotechnical and structural dynamics has plagued the advancement and the consequent inclusion of SFSI effects in design. A rigorous performance-based design methodology should not just consider the performance of the superstructure but the supporting foundation system as well. Case studies throughout history (eg. Kobe 1995, Kocaeli 1999 and Christchurch earthquakes 2010-2011) have demonstrated that a poor performance at the foundation level can result in a full demolition of the structure and, in general terms, that the extent of damage to, and repairability of, the building system as a whole, is given by the combination of the damage to the soil, foundation and superstructure. The lack of consideration of the modifying factors of SFSI and an absence of intuitive performance levels for controlling foundation and soil behaviour under seismic loads has resulted in inadequate designs for buildings sited on soft soil. For engineers to be satisfied that their designs meet the given performance levels they must first, understand how SFSI affects the overall system performance and secondly have tools available to adequately account for it in their design/assessment. This dissertation presents an integrated performance-based design procedure for buildingfoundation systems that considers all of the major mechanisms of SFSI. A new soil-foundation macro-element model was implemented into a nonlinear finite element software and validated against several experimental tests. The numerical model was used to provide insights in to the mechanisms of SFSI and statistical analysis on the results yielded simple expressions that allow the behaviour to be quantified. Particular attention was paid to the effects of shear force on the foundation response and the quantification of the rocking mode of response. The residual deformations of the superstructure and distribution of forces up the structure were also investigated. All of the major SFSI mechanisms are discussed in detail and targeted numerical studies are used to explain and demonstrate concepts. The design procedure was validated through the design and assessment of a series of concrete buildings that were designed to account for the effects of SFSI.
