Journal of Numerical Methods in Civil Engineering
Volume:2 Issue: 2, Dec 2017

This paper presents numerical modeling technique for Dhajji-Dewari structures (timber-braced rubble stone masonry), and its application for the evaluation of in-plane force-deformation capacity of Dhajji wall panels of different configuration of bracings. Dhajji structures are mainly composed of vertical and horizontal timber posts and braced using diagonal bracings and horizontal studs. Wall openings are filled with random rubble masonry in week mortar. These types of structures are known for their high lateral deformability and are mostly found in Kashmir and its surrounding areas both in Pakistan and India, locally named as “Dhajji-Dewari”. A numerical model of Dhajji wall was developed using a finite element based structural seismic analysis program SeismoStruct, based on the experimental study carried out at the Earthquake Engineering Center of UET Peshawar. In-plane force-deformation response of Dhajji wall was evaluated through static pushover analysis, and validated with the measured response. The numerical model was extended to evaluate and compare the lateral strengths of Dhajji walls of three different configurations of bracings. This can enable structural designer to select Dhajji wall with a particular bracing configuration keeping in view the required lateral strength and deformability with least possible quantity of timber for construction, which might be helpful to economize the construction of these structures.

In buildings with triangular plan, the center of mass and rigidity cannot geometrically match all possible directions of the earthquake. This will result in torsional moments in the stories causing the building to rotate around the center of rigidity. In this paper, via response spectrum analysis (RSA) and nonlinear static analysis, the seismic behavior of 5-, 10- and 15-story steel structures with a triangular plan is investigated by proposing 7 types of bracing arrangements in the plan. According to the analysis results, the most appropriate bracing arrangements in these seven proposed models in the triangular planes is the arrangement of braces in the middle of the triangle sides and continuous. This causes the center of mass to get closer to the center of rigidity, as a result of which, torsional moments and additional rotational displacements at the stories are decreased. The continuous braces reduces the lateral displacement of the structure about 38% and increases the displacement ductility ratio about 12%. Also, in structures whose braces cross each other at one point, the torsional strength of the system has been zeroed and in accordance with the ASCE7-16, they are considered to possess extreme torsional irregularity and the structures are therefore unstable

This article presents combination method of h-refinement and node movement in finite element method to solve elasticity problems. Colliding bodies optimization algorithm (CBO), which is a meta-heuristic algorithm, is used to move nodes and in case of inaccurate answers h-refinement could be used to increase the number of nodes in the regions which have too many mistakes. Error estimate, used in both node movement and h-refinement, is made by L2-norm which is appropriate to triangle elements and another use of it is to build cost function that is used in CBO. The proposed method is suitable for finite element meshing procedure because it can solve problems in areas with high stress concentration. Two benchmark example results in linear elasticity problems with respect to other techniques, show the efficiency and acceptable accuracy of the proposed method

The seismic soil-pile-superstructure interaction (SSPSI) is one of the most important sources of nonlinear dynamic response of any pile supported structure such as jacket type offshore platforms (JTOP). In recent years, some researchers have studied experimental and real cases of JTOP response under earthquake or cyclic loading using OpenSees software. Throughout a parametric study, the main goal of this paper is to provide designers of pile supported structures supplemental insight into the amount of importance of different parameters included in the SSPSI response. To this end, a beam on nonlinear Winkler foundation numerical model of a single pile embedded in layers of soft clay and dense sand tested in a geotechnical centrifuge was created using OpenSees. The created numerical model was able to successfully capture the response in elastic and intermediate range of nonlinear response. However, the rate of excess pore pressure generation in the model was observed to be faster than the real test results in highly nonlinear events. Subsequently, the sensitivity of the analyzed response to soil shear strength and stiffness parameters was evaluated. The response sensitivity to various input parameters used for definition of pressure sensitive material constitutive behavior - especially the influence of parameters on pore pressure generation – was also investigated. The effects of degradation of p-y behavior after liquefaction on ARS of superstructure and moment distribution of pile were investigated. Moreover, a sensitivity analysis has been carried out to explore the systematic effects of various parameters of clay soil layer on dynamic pile analysis results

Seismic isolation is an effective approach used in controlling the seismic responses and retrofitting of structures. The construction and installation of such systems are expanded nowadays due to modern improvements in technology. In this research, the seismic performance of steel moment resisting frames isolated by Lead Rubber Bearing (LRB) is assessed, and the seismic demand hazard curves of the frames are developed using Probabilistic Seismic Demand Analysis (PSDA). In addition, the effects of LRB on overstrength, ductility and response modification factor of the frames are studied. To achieve this, Incremental Dynamic Analyses (IDA) are conducted using 10 records of near field earthquake ground motions on the intermediate steel moment resisting fixed base frames with 3, 6 and 9 storeys retrofitted by LRB according to ASCE 41. The results show that in the case of isolated frames, the values of ductility and response modification factor are decreased in comparison with those of fixed base frames. Moreover, based on the developed fragility curves, seismic isolation is more effective in improving structural performance in extensive and complete damage states compared to slight and moderate damage states. However, increasing the height of both structural groups (i.e. fixed base and base isolated) results in reduction in performance level. Besides, the probability of occurrence of a certain demand is reduced by base isolation.

Bending responses are the important characteristics of structures. In this paper, the bending solution of the thin and thick beams which are elastically restrained against rotation and translation are presented using various theories. Hence, accurate and direct modeling technique is offered for modeling of the thin and thick beams. The effect of the values of the span-to-depth ratio and type of the beam supports are assessed to state accurate comparison of various theories. Finally, the numerical examples are shown in order to present the evaluation of the efficiency and simplicity of the various theories. The results of the theories are compared with the results of the finite element method (ABAQUS). Based on the results, using the Timoshenko beam theory, the obtained values are in good agreement with the Finite Element modeling for the values of the span-to-depth ratio (L/h) less than 3. On the other hands, due to ignoring the shear deformation effect, the Euler–Bernoulli theory underestimates the deflection of the moderately deep beams (L/h=5).