2.3 Post Earthquake Awareness
AIJ Level-1 Seismic Screening of some RC Buildings Damaged by the Luzon 1990 Earthquake
A.W.C. Oreta
ABSTRACT: Civil and structural engineers must address the need of assessing the seismic safety of existing buildings. Given the large number of buildings in the metropolis, a brief method of seismic screening of buildings must be done to prioritize buildings which requiring detailed seismic evaluation and possible retrofitting. The level-1 seismic screening of the Architectural Institute of Japan (AIJ) uses a basic structural performance index (BSPI) to rank low-rise to medium-rise reinforced concrete buildings according to potential seismic hazards. How to use the index to judge which buildings are potentially hazardous need to be given further study especially in the Philippine setting. This study focuses on the evaluation of the BSPI of RC buildings damaged at Baguio City during the July 16, 1990 Luzon Earthquake. Through the documented photos of the buildings, sketches of building plans and descriptions of the damages found in the literature, an estimate was made on the BSPI of the damaged buildings at the ground floor. By knowing the index at the ground floor of the damaged buildings, a critical or cut-off value was determined. Based on the study, index values between 0.2 and 0.8 were obtained for severely damaged and collapsed buildings.
Post-Earthquake Physical Damage Assessment for Gas Networks
S. Esposito, I. Iervolino, L. Elefante & S. Giovinazzi
ABSTRACT: This paper describes the assessment of the damage that occurred to the local gas network following 6th April 2009 L’Aquila earthquake. The analysis accounts for all the components of the system including: 1) Metering/Pressure reduction stations (M/R stations); 2) medium-pressure distribution networks; 3) Reduction Groups; 4) low-pressure distribution networks; 5) demand nodes; 6) gas meters. The processing of the technical reports from Enel Rete GAS (the only gas network operator in the affected region), describing the repairs and replacements activities following L’Aquila earthquake, is presented in the paper and the resulting damage scenario is discussed.
The Dallington Cable and Foot Bridge: A Case Study Example of Successful Engineering Lifeline Mitigation
J.R. Mackenzie
ABSTRACT: Orion’s participation in the Christchurch Engineering Lifelines Project resulted in the identification of the Dallington Bridge as potentially being a “weak link” in their network. The bridge, as well as being a footbridge, supports a pair of 66 kV oil filled cables supplying the Dallington Zone Substation. The substation supplies electricity to approximately 13,000 dwellings, commercial premises and other customers.
The bridge was designed in 1967 and is a relatively slender cast insitu prestressed arch structure bearing on piles. Such a design is very reliant on appropriate horizontal and vertical restraint at each abutment. A detailed seismic and geotechnical analysis was undertaken in 1997/8 and indicated that the immediate area was potentially prone to liquefaction and lateral spreading and as a result the bridge was vulnerable to severe damage both transversely and longitudinally. The author presented a paper to the 1999 NZSEE Conference on the vulnerability of the bridge and the proposed mitigation work. The mitigation included additional heavy raking piles at each abutment, the encasement of the cables with heavily reinforced concrete and the creation of “cavities” to allow for lateral movement.
Following the Darfield Earthquake on the 4th of September, the bridge was inspected and found to be relatively undamaged and supply to the Dallington Substation was restored on the day of the earthquake. This was in spite of the south approach bulging as a result of the significant lateral spreading that had occurred in the area. Subsequent investigation has confirmed that the cables have sustained some degree of damage even though they have remained in service. Their replacement will take place in a timely fashion as a part of Orion’s overall programme of risk management.
It is considered that had the bridge not been strengthened 11 years ago, the bridge almost certainly would have failed and the cables be damaged beyond repair. It would also have resulted in electricity shortages and disruption for weeks following the earthquake
Darfield Earthquake 2010: Lateral Spreading Actions on the Dallington Pedestrian Bridge
M. Le Heux, A. Palermo, M. Cubrinovski & J.R. Mackenzie
ABSTRACT: Lateral spreading was the main cause of damage to bridges during the Darfield earthquake of September 4 2010. A case study bridge is chosen to explore in detail lateral spreading loads placed on a structure. Different methods for analysing ‘long’ piles in laterally spreading soil are used to analyse the bridge. A parametric study is also undertaken assessing design assumptions made in predicting lateral spreading forces on pile walls and pile caps. These methodologies and assumptions are validated against the observed forces placed on the case study bridge.
Case Studies of Observed Pounding Damage during the 2010 Darfield Earthquake
G.L. Cole, R.P. Dhakal, A.J. Carr & D.K. Bull
ABSTRACT: Five days after the 2010 Darfield earthquake, an external photo survey of pounding damaged structures was performed in Christchurch’s Central Business District (CBD). This paper presents three case studies with unique pounding damage characteristics identified during the survey. Typical building configurations where pounding was anticipated but not observed are also described and reasons for the apparent lack of damage are examined. This paper compliments a recent paper by the authors in the NZSEE bulletin, which examined the typical and extreme forms of pounding damage observed during the damage survey.
Field Measurements of Lateral Spreading following the 2010 Darfield Earthquake
K. Robinson, M. Cubrinovski, P. Kailey & R.P. Orense
ABSTRACT: A field investigation was launched following the 2010 Darfield Earthquake in order to measure permanent lateral ground displacements in areas significantly affected by liquefaction-induced lateral spreading. Ground surveying techniques were used to estimate total displacement along specific transects. Approximately 75 transects have been completed to date in the areas of Kaiapoi, Spencerville, and various suburbs within Christchurch City. Maximum lateral displacements measured in these areas ranged from about 0.5 m to up to 3.5 m, causing significant damage to nearby structures and lifelines. This paper presents the methods involved in our investigation, a summary of our results, and characteristics of the lateral spreading which occurred in South Kaiapoi.