JOURNAL OF SCHOOL OF ENGINEERING
Year:2005 | Volume:17 | Issue:1|Papers Count:6

Bridges are potentially one of the most seismically vulnerable structures in the highway system during earthquake. It is known that the seismic performance of transportation systems plays key role for the post earthquake emergency management. Probabilistic seismic demand curves are one of the new methods for study on seismic behavior of structures. The Probabilistic Seismic Demand Curves (PSDC hereafter) is the outcome from a Probabilistic Seismic Demand Analysis (PSDA) or in other word, from an Incremental Dynamic Analysis (IDA). A PSDC relates ground motion Intensity Measures (IM), such as PGA and PGv, to Engineering Demand Parameters (EDM), such as girder drift ductility. In this paper the probabilistic seismic demand curves are developed. The seismic performance of a railway prestress concrete bridge is assessed using PSDC derived from dynamic nonlinear finite element analysis. Study on nonlinear behavior of prestress girders under vertical motions, study on structural response to various seismic records and reliability of results depend on intensity measures are parts of this research area. A software package provide in MATLAB for study on results. Modeling of the bridge using 3D nonlinear models and modeling of abutments, bearings, effect of falling of girder on its bearings and nonlinear interaction of soil-structure are some of advantages of this research.

In this paper, a variety of time approximations for discretization of smeary flow in porous media have been presented. Following the introduction of the required approximations, the range of performance for each approximation has been defined using numerical experiments. In order to apply each approximation for discretization of the equations, its behavior has to be defined Performance of various time approximations for discretization of smeary flow in porous media using finite volume method has been demonstrated in most of the numerical experiments. Euler upwind approximation method for time discretization of equations has long stability periods. This method demonstrates weak performance in first-degree convergence. Sdrik method performs much faster than Cranck-Nicolson method with respect to convection. This approximation also shows less fluctuation. Application of Frace approximation regarding convection is appropriate. This approximation also has weak fluctuations. Vosoughifar approximation regarding convection and diffusion demonstrates satisfying performance. For numerical investigation regarding convection and diffusion of pollution in porous media, this approximation is recommended.

Application of in-situ testings such as SPT and CPT is a common practice for determining vertical ultimate capacity of deep foundations as supplement of static analysis. Based on N value from SPT and/or N - qc equivalent from CPT a proposed method is presented and compared with current methods. In addition to simplification, data processing, failure zone extension and limit load of piles has been emphasized in proposed approach. Fifty three case histories have been collected including full scale pile load tests in which 8PT and/or CPT were performed close to pile locations. Using 19 cases the interpretation methods of P - ∆ results from pile load tests, have been verified to evaluate plunging criteria. Comparison of errors for pile capacity prediction has been done with graphical, numerical and cumulative probability approaches. The results demonstrate less error and more accuracy for proposed method than others for pile capacity estimation. Moreover, all of six methods predict pile capacity with more precision using SPT-CPT equivalent data than only when SPT data used.

The object of this paper was to develop some Correlations in order to predict CRR of the base and subbase materials used in Iran. Therefore would be able to determine CRR of the materials, based on save analysis and density results. In order to acheive such Correlations 367 CRR tests were conducted on 29 types of base and subbase materials with various compaction energies as well as percent of fine materials. These tests resulted in developing Correlations with high accuracy. Furthermore. apart from developing the models, some other interesting results were obtained which will be discussed in the paper.

The present research describes the variations of the intermediate principal stress, σ2, in plane strain condition which occurs in many earth structures, such as embankment dams, retaining walls and strip footings. For this purpose a series of drained monotonic plane strain tests on Leighton Buzzard sand under different initial magnitudes of σ2 were performed. The sand samples were initially packed to dense and loose samples. The Biaxial Tester, which is able to simulate the plane strain condition and also to measure the variation of σ2 during the test, was employed in the research. It is shown that the stress-strain response of sand and its shear strength at failure do not vary significantly and almost independent of the initial magnitudes of σ2, but are dependent on its initial void ratio. This implies that if different initial values of σ2 create various directional anisotropic structures, they play no part in the plane strain tests. Also a numerical model, which is capable of including σ2, is proposed to predict particularly stress-strain response of sand and magnitude of σ2 at failure. The variations of stress ratio σ2/(σ1 + σ3) were monitored during shearing to clarify the significance of intermediate principal stress.

To find out the optimum percentage of Sirjan's and Ghaodar sefied's pozzolans (two cities which are located in Kerman province) az cement replacement, first by two methods, their strength activity index were determined and then for different mixes with different ages were tested Based on 28 day ages of compressive strength, the percentage of pozzolans which was assumed to be suitable as the cement replacement was selected as the optimum percentage of different mixes. For the selected mixes, the different long term tests were carried out to measure the mechanical properties. The results were also compared with the same non pozzolanic oncrete mix of each similar group. Also considering the important role of concrete durability, the pozzolanic and non pozzolanic concrete specimens of different cement and curing types were prepared and evaluated with each other.