Relationship of drought frequency and severity with range of annual temperature variation

The frequency and severity of occurrence of meteorological droughts in different climatic regions depend on regional climatic factors. This study has made an effort to explore the relationship of range of annual temperature variation at a given place with the frequency of occurrence of drought and the maximum magnitude of seasonal rainfall deficit (i.e., severity). The seasonal rainfall refers to sum of monsoon season (rainy season) rainfall in India. The monthly precipitation data of 113 years (1901–2013) for 256 stations in different parts of India have been used to estimate the return period of meteorological drought at different stations. The daily normal values of observed maximum and minimum temperatures from 40 years of records have been utilized to estimate range of temperature variation (θ_R) during the year at each stations. In various parts of India, the θ_R ranges from 10 °C in humid regions to 40 °C in arid regions. The various climatic regions have been experiencing maximum deficiency of annual rainfall ranging from 30% (humid) to 90% (arid). The results reveal that places exhibiting θ_R values between 40 to 30 °C face more frequent droughts with average frequency of once in 3 to once in 6 years. The occurrence of extreme and severe drought events is more frequent in the regions with higher values of θ_R compare to that in lesser values of θ_R. The regions with θ_R values between 30 to 25 °C mostly face severe and moderate events having the average drought return period of 6–9 years, and the occurrence of extreme droughts in these regions is rare. Furthermore, regions with θ_R?<?20 °C face moderate droughts only with an average return period of 14 years. This study divulges that the average return period and magnitude of deficiency of drought events have notable relationship with the range of temperature variation during the year at a given place.

     

Some applications of the linear programming within gravimetry

Summary The paper presents some mathematic patterns by using the linear programming. These patterns are making up a simple method of gravimetric data transformation, solvable with the help of digital computers. Some methods of differentiating the regional and local anomalies, of effectuating the calculus of some gravity derivatives and of establishing the shape of bidimensional bodies, are shown. This work was aimed to enlarge the field of the linear programming appliableness within geophysics. Former studies on the scope were undertaken byShalaev [7]³), [8], as well as byDougerty andSmith [3].     

La séparation des signaux utiles gravimétriques du fond des perturbations

Summary The paper is dealing with the separation problem of weak intensity anomalies from the perturbation background. By means of the Shannon's form and based on the values estabilished for a measured gravitational field, g, the mean quantity of information sent forth at the source — perturbating body — is calculated in order to intercept the g set. This quantity takes a maximum value above the perturbating body, while for the remainder a deadening of the perturbations is obtained.     

Evaluation of efficiency of ALSC floating-sliding base-isolation system based on shake table test and floor response spectra

The ALSC base isolation system was investigated by testing a church model to the scale 1/3.5 on the two-component shaking table at the IZIIS’ Laboratory, Skopje, Macedonia. The investigation was performed within the frames of the European FP6 project PROHITECH, related to seismic protection of historical buildings by innovative and reversible mixed technology systems. This system was originally developed in 2001 and applied on a model of a steel reservoir. The church model was tested twice: with an active base-isolation system and fixed to the base. The effectiveness of the base-isolation system was investigated by the transfer function/floor response spectra technique. Special software for calculation of the transfer functions and floor response spectra based on experimental data, referred as “SPECTRA”, was developed by the authors of this paper. The main objective of the investigations presented in this paper was evaluation of the effectiveness of the ALSC floating sliding base-isolation system by using the Response Spectra approach. Comparison of the Floor Response Spectra was done for two cases a fixed base model and a base-isolated model. The base response spectrum was calculated from the input time history of the Montenegro earthquake compressed 3.5 times (geometry scale of the model). The Transfer Functions and the Floor response Spectra at a particular level were calculated from the Cross Power Spectra (CPS) and the Auto-Power Spectra. The obtained results showed that the effect of the base-isolation system was considerable, with a low transmissibility of energy from shake table to the model.     

Centralized semi‐active control of post‐tensioned steel frames

Centralized semi‐active control is a technique for controlling the whole structure using one main computer. Centralized control systems introduce better control for relatively short to medium high structures where the response of any story cannot be separated from the adjacent ones. In this paper, two centralized control approaches are proposed for controlling the seismic response of post‐tensioned (PT) steel frames. The first approach, the stiffness control approach, aims to alter the stiffness of the PT frame so that it avoids large dynamic amplifications due to earthquake excitations. The second approach, deformation regulation control approach, aims at redistributing the demand/strength ratio in order to provide a more uniform distribution of deformations over the height of the structure. The two control approaches were assessed through simulations of the earthquake response of semi‐actively and passively controlled six‐story post‐tensioned steel frames. The results showed that the stiffness control approach is efficient in reducing the frame deformations and internal forces. The deformation regulation control approach was found to be efficient in reducing the frame displacements and generating a more uniform distribution of the inter‐story drifts. These results indicate that centralized semi‐active control can be used to improve the seismic performance of post‐tensioned steel frames. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental and analytical investigation of seismic stability of masonry walls at Beauharnois powerhouse

The seismic stability of the facade brick-masonry walls of the machinery building of the Beauharnois powerhouse near Montreal, Quebec, Canada were investigated numerically by use of non-linear models and applying experimental methods on site and on the IZIIS’ seismic shake-table. The dynamic properties of the machinery building were obtained by ambient vibration measurements. Based on these results, a model of a representative part of the building, consisting of steel frames and brick masonry wall, was designed and constructed to the reduced scale at the IZIIS’ Dynamic Testing Laboratory and then tested on the two-component shake-table. The geometry of the original structure was completely scaled to 1/3, consisting of many realistically simulated details such us: brick layers, steel columns, openings, window frames, steel connectors between brick layers, number of layers, brick dimensions, etc. The material used for the model was: original steel for the frame structure and bricks of reduced mechanical properties for the masonry wall, close to the similitude requirements according to the Backingham’s theorem, valuable for adequate artificial—mass simulation model as well as true replica simulation model. More than 50 seismic tests were performed considering the design earthquake Nahanni NWT, H1, with a time scaling factor of 3^1/2, and acceleration scaling factor 1, according to the model design rules. The intensity of the applied input earthquake excitation was from 0.05 to 1.2 g. The design peak acceleration of Nahanni earthquake was 0.2 g. The cracks development was stated at 0.7 g input acceleration. These were concentrated around the openings. No collapse happened even under the strongest earthquake input. The numerical part of this paper deals with formulation/application of the critical plane approach to seismic analysis of masonry structures. Starting with the constituents, i.e. mortar and bricks, the macroscopic strength properties of masonry were established based on numerical homogenization. Generally, based on all the performed experimental tests, considering some simplifications and assumptions in the constructing details, as well as in the design of the model, the global conclusion is that the existing wall is very well incorporated in the steel structure of the powerhouse. The complementary stiffness of the steel frame and the brick masonry wall produces interactive deformation of the system. Only local cracking and relative displacement between the wall and the steel frames could be expected in the case of a strong earthquake.