Predicting Probability of Liquefaction Susceptibility based on a wide range of CPT data

In the present study, three efficient soft computing techniques i.e. GP, RVM, and MARS are utilized to predict the probabilistic liquefaction susceptibility of soils based on reliability analysis. For this, a sum of 253 Cone Penetration Test (CPT) data of nineteen major earthquakes occurred between 1964 and 2011 has been collected from the literature. Six liquefaction parameters such as corrected cone penetration resistance, total vertical stress, total effective stress, maximum horizontal acceleration, magnitude moment, and depth of penetration. To evaluate the overall performance of the proposed models, rank analysis has been carried out. Based on the values of performance indices, the GP model outperforms the other two models in terms of RMSE=0.15, R2 =0.77, and VAF=76.86 in the training stage while the same has been found 0.14, 0.81, and 80.46 in the testing phase. Also, the Rank Analysis confirms the superiority of the GP model in predicting the probability of liquefaction susceptibility of soils at all stages.

What can we learn from the January 2012 northern Italy earthquakes?

<p>This note focuses on the ground motion recorded during the recent moderate earthquakes that occurred in the central part of northern Italy (Panel 1), a region that is characterized by low seismicity. For this area, the Italian seismic hazard map [Stucchi et al. 2011] assigns a maximum horizontal acceleration (rock site) of up to 0.2 g (10% probability of being exceeded in 50 yr). In the last 4 yr, this region has been struck by 9 earthquakes in the magnitude range 4 <span>≤</span>M<span>w </span><span>≤</span> 5.0, with the three largest located in the Northern Apennines (the M<span>w </span>4.9 and 5.0 Parma events, in December 2008 and January 2012) and on the Po Plain (the M<span>w </span>4.9 Reggio Emila event, in January 2012). We have analyzed the strong-motion data (distance &lt;300 km) from these events as recorded by stations belonging to the Istituto Nazionale di Geofisica e Vulcanologia (RAIS, http://rais.mi.ingv.it; RSNC, http://iside.rm.ingv.it) and the Department of Civil Protection (RAN, www.protezionecivile.it; http://itaca.mi.ingv.it). […]</p>

3D Dynamic Analysis of a 270m Concrete Faced Rockfill Dam

3D finite element mesh for a 270m high CFRD was generated with advanced grid discretion technology. Adopting EI-Centro seismic wave with maximum horizontal acceleration 0.277g, dynamic response of this 270m high concrete faced rockfill dam was obtained by equivalent linearization method. Using residual strain model, the permanent deformation of the dam was obtained. Calculation results showed that the maximum acceleration and displacement of dam body, dynamic stress of face slab and deformation of joints are all within normal range. Therefore, the safety of dam would be guaranteed when it is subjected to 7 degree earthquake.

Seismic Response Analysis for Pier in Considering of Uplift Effect

In earthquake engineering, researchers have found that many structures were not damaged after strong ground motions because of the rocking effect. In order to reveal the potential application value of the uplift effect on seismic isolation, it will be using numerical simulation software OpenSees to research the seismic response of pier considering uplift. Building the pier’s finite element model and considering the plasticity and nonlinear of the pier and soil spring, the ground motion from El Centro and TCU101 are taken as the input respectively. Through analyzing the result, it is shown that at the base of the pier the maximum bending moment is reduced by 36.93% and 46.70%, and the maximum curvature is also reduced by 78.42% and 87.12% respectively. Meanwhile, the maximum horizontal acceleration at the top of the pier is decreased 12.60% and 16.90%. The uplift effect significantly reduces the plastic deformation and plays a base-isolated role according to the results. It has also found that the earthquakes with velocity pulse effect are dangerous to the structures.

Engineering implications of ground motions from the Northridge earthquake

The magnitude, duration, and frequency content of ground motions from the Northridge earthquake are analyzed and compared to predictive relationships typically used in engineering design and to the 1994 Uniform Building Code (UBC). A relationship between maximum horizontal acceleration on soil versus maximum horizontal acceleration on rock is presented based on strong-motion recordings at free-field sites. The effect of geologic conditions on localized damage patterns is shown to be important for this earthquake, although many of the sites within the affected region are stiff soil sites classified as S1 or S2 sites by the UBC. The results of preliminary seismic site response analyses performed at two deep alluvial sites indicate that much of the observed site amplification can be captured by one-dimensional wave propagation analyses.

Motions of rigid bodies and criteria for overturning by earthquake excitations

This investigation deals with motions of rigid bodies on a rigid floor subjected to sinusoidal and earthquake excitations, and overturning of the bodies. Experiments and simulations of frequency sweep tests were conducted, and it is concluded that the horizontal velocity as well as the acceleration must be taken into account as criteria for overturning. Simulations by earthquake excitations show that the criteria are also applicable to the earthquake excitations. Therefore it is possible to estimate the lower limits of the maximum horizontal acceleration and velocity of the input excitations, from the overturning of bodies.