Asian journal of civil engineering
Volume:11 Issue: 5, Oct 2010

Endurance Time (ET) method is a time history based analysis procedure that applies special intensifying acceleration functions for estimating the seismic performance of structures at different excitation levels in each single analysis. One of the extensions of the ET method is in the seismic assessment of buildings considering multi-component excitation. In this paper, a procedure for three-directional seismic analysis of buildings is proposed and application of this method to several steel moment frames is investigated. Several Steel Moment Frames were designed according to INBC Code. These Frames were analyzed under ET acceleration functions in horizontal and vertical directions simultaneously and results were compared to Response History Analysis. It is observed that ET method can predict the results from multi-component analysis, including vertical excitation, with reasonable accuracy. Scattering and accuracy of the results are also investigated.

Polymer as admixture can improve the properties like higher strength and lower waterpermeability than the conventional concrete. Rheomix 141 is styrene-butadiene co–polymer latex, specifically designed for use with cement composites. It is used in mortar and concrete as an admixture to increase resistance to water penetration, improve abrasion resistance and durability. The objective of the present investigation is to study the behavior of polymer cement concrete in the hardened state. The variables studied include the grade of concrete and dosage of polymer. Five different grades of concrete M20 to M60 with polymer quantities starting from 5% to 10% were used in the present work. The various mechanical properties like compressive strength, splitting tensile strength, flexural strength, stress–strain characteristics, and modulus of elasticity and permeability characteristics of concrete have been studied. The results obtained thus are encouraging for partial addition of polymer with cement up to 10%.

This paper presents the dynamic stresses within the soil-foundation interface zone measured by an experimental process. The cubic foundation prototype is subjected to a cyclic loading directly generated by the testing machine at the foundation center. The stress enhancement induced by the dynamic loading may lead to a partial confinement with an eventuality of instability risks or resistance loss; showed by a particle rearrangement. The tests have been conducted on two soil samples namely dense and medium dense sand. Experimental displacements, measured at the soil foundation interface are represented, as a function of the number of cycles, for a constant stress level. The dynamic behaviors of used sample soils are analyzed and some concluded remarks are presented.

In this paper, the investigation is carried out to study the structural responses of two adjacent structures connected with Maxwell dampers under various earthquake excitations. The specific objective of this study is to evaluate the optimum damper parameter and its importance in response reduction of adjacent structures coupled by Maxwell dampers. The optimum damper parameter is investigated for the adjacent coupled structures subjected to four different types of earthquake ground motions. A formulation of the equations of motion for the two adjacent multi-degree-of-freedom (MDOF) structures connected with Maxwell dampers is presented. The numerical study is carried out for two adjacent MDOF structures connected with Maxwell dampers having same damper parameter in all dampers as well as, having different damper parameter in the dampers. The investigation is also carried out for effectiveness of the damper in terms of the structural response reduction, namely, displacement, acceleration and shear forces of adjacent connected structures. In addition, to minimize the cost of the dampers, the optimal location of the dampers, rather than providing the dampers at all floor levels is also investigated. Results show that using Maxwell dampers of appropriate parameter to connect the adjacent structures of different fundamental frequencies can effectively reduce earthquake-induced responses of either structure. Further,lesser dampers at appropriate locations can significantly reduce the earthquake response of connected system, there by reducing cost of damper significantly.

In this paper, three-dimensional amplification of plane harmonic SH, SV, and P waves inmultilayered alluvial valleys is investigated by using a boundary element method infrequency domain. It is shown that in order to achieve real responses, the problem must be analyzed and modeled three-dimensionally. Also, for exact evaluation of surface groundmotions in alluvial valleys all key parameters such as layering, material and geometricalcharacteristics of each layer, stimulation frequency, wave type, plus angle and azimuth ofincidence must be taken into account altogether.The accuracy and efficiency of the proposed formulations for the computation of thesurface displacement field amplification is verified by solving a number of problems.

The skeptical part of building regulations for durability-design process might be attributed to the ambiguities arising from the qualitative and linguistic definitions of the relevantparameters when dealing with the service life and durability of reinforced concrete (RC)structures. Handling of these parameters with traditional methods is not a straightforwardmatter but fuzzy systems as an advanced tool for processing the linguistic knowledge could be easily utilized to address this issue. Accordingly this paper introduces a support system assisted by rule-based genetic fuzzy system to quantify the environmental aggressiveness and subsequently infer a minimum cover thickness for durable reinforced concrete members in the corrosive environments.

Assessment of the seismic performance of a structure often requires conducting nonlineardynamic analyses under a set of ground motion records scaled to a specific level of intensity using an appropriate scaling method. In this study to reduce the variability in the seismic demands, a seismic-intensity scaling index is developed through studying weaknesses and strengths of different scaling methods. Results of the incremental nonlinear dynamic analyses of generic frames with 3, 6, 9, 12 and 15 storey under 40 near-fault ground motions show that using root-mean-square value of pseudo spectral accelerations over effective period range of structures can considerably reduce the scatter in the dynamic responses particularly once higher modes and period elongation effects dominate the response. By using this scaling method, the amount of dispersion is nearly independent of the ductility demand level and the number of stories.

Iran Strong Motion Network (ISMN) started its activities in 1973. Iran Strong MotionNetwork had 1087 digital (1082 SSA-2 and 5CMG-5TD) and 13 analog (SMA-1)accelerographs in operation in 2007. The accelerograms of different earthquake, aredownloaded, controlled, processed, and then added to the comprehensive data bank, which is very useful for scientists and engineers in the field of engineering seismology andearthquake engineering. In the second half of the year 2007, 124 accelerograms (with PGA greater than the trigger level of 0.01g) were recorded by 91 accelerographs, which were triggered by 69 different earthquakes. The maximum PGA of about 0.148g was occurred in Tabriz station (Eastern Azerbaijan Province).