Sharif Digital Repository

A comprehensive non-linear finite element (FE) model of integral abutment bridges (IABs) is presented to facilitate the analysis of such bridges using commercial software, especially under seismic loading. The presented model is capable of capturing non-linearity in both the structure and soil, in addition to considering far-field soil response. The model is simple enough to be used for practical purposes. On the other hand, many aspects of seismic behaviour of IABs are unclear, due to complicated soil–structure interaction. Using the presented model, a parametric study is performed to identify the effects of bridge length, abutment type and soil type on seismic behaviour of IABs. Non-linear... 

A comprehensive non-linear finite element (FE) model of integral abutment bridges (IABs) is presented to facilitate the analysis of such bridges using commercial software, especially under seismic loading. The presented model is capable of capturing non-linearity in both the structure and soil, in addition to considering far-field soil response. The model is simple enough to be used for practical purposes. On the other hand, many aspects of seismic behaviour of IABs are unclear, due to complicated soil–structure interaction. Using the presented model, a parametric study is performed to identify the effects of bridge length, abutment type and soil type on seismic behaviour of IABs. Non-linear... 

During an earthquake, pounding of bridge superstructure into abutments is potentially destructive to structural elements and may cause unseating failure and collapse. By using energy dissipative devices such as passive dampers, the harmful pounding force may be prevented. One of the most economical passive dampers for structural applications is the pipe damper, recently introduced by the authors. In this paper, computer models of a two-span 60-m long conventional overpass bridge are equipped with different lengths of two types of pipe dampers, namely the dual-pipe (DPD) and infilled-pipe (IPD) dampers. A simplified lumped-mass model for the bridge considering soil stiffness is proposed and... 

Karun Bridge is part of a national highway project underway in southern Iran. The bridge is a 336 m steel arch structure that weighs more than 2500 tons and crosses the Karun River 270 meters above the river valley. The bridge will be the largest suspended bridge in the Middle East. Cantilever construction is to be used to construct the bridge from both sides simultaneously. The weight of the bridge is to be carried by two abutments and four piers that are anchored to exposed weathered rock mass. Loads on the abutments and piers include significant cantilever loads and moments during bridge erection and wind loads. Daily rapid temperature changes also will impart significant thermal loads on... 

Integral abutment bridges have many advantages over bridges with expansion joints in terms of economy and maintenance costs. However, in the design of abutments of integral bridges temperature loads play a crucial role. In addition, seismic loads are readily transferred to the substructure and affect the design of these components significantly. Currently, the European and American bridge design codes consider these two load cases separately in their recommended design load combinations. In this paper, the importance and necessity of combining the thermal and seismic loads is investigated for integral bridges. A 2D finite element combined pile-soil-structure interactive model is used in this... 

A novel and robust approach is proposed to find the optimum shape of concrete arch dams located on any unsymmetrical shape of a valley. The approach is capable of finding the optimum shape for any given valley type in suitable time, based on abutment stability analysis, against thrust forces from an arch dam. The behavior and stability of a concrete arch dam is strongly dependent on the bedrock on which the dam rests. The stability of the abutment is considered a constraint in the proposed approach. In addition, a new objective function is introduced to decrease the final volume of the arch dam. Furthermore, a computer program was developed, which takes the effect of the dam foundation... 

Seepage analysis serves as one of the most significant stages in the design process of an embankment dam. In two-dimensional (2D) seepage analysis of embankment dams, little or no attention is paid to the widthwise flows from side abutments. Moreover, the role of grout curtain extensions into the side abutments and abutment material properties are inevitably neglected when performing seepage analyses in 2D plane. In this paper, two and three-dimensional (3D) models of a rock-fill dam are generated and several unsteady and steady state seepage analyses are performed using finite element method (FEM). The results obtained from 2D and 3D seepage analyses were compared with measurements from the... 

Objectives: The aim of this study was to investigate the effects of implant design on the apex area and on stress and stress patterns within surrounding bone. Methods: Three commercially available implants with the same diameter (3.5 mm), same length (10-11 mm), and same complement abutment were selected for modeling as follows: (1) flat apical design with light tapering degree, (2) dome-shaped apical design with light tapering, and (3) flat apical design with intense tapering in one-third of the apical area. According to human cone-beam computed tomography (CBCT), the bone was modeled using a cortical thickness of 2 mm and cancellous bone. Forces of 100 N and 300 N in the vertical and 15°... 

In this paper, a simple finite element model for seismic analysis of retaining walls is introduced. The model incorporates nonlinearity in the behavior of near wall soil, wall flexibility and elastic free field soil response. This model can be employed in nonlinear modeling of retaining walls and bridge abutments. The advantages of this model are simplicity and flexibility in addition to acceptable precision. Using this finite element model, an analytical study is conducted on several soil-wall systems using nonlinear time-history analysis by applying real earthquake records. Based on the results of these analyses, new seismic soil pressure distributions are proposed for different soil and... 

Seepage analysis serves as one of the most significant stages in the design process of an embankment dam. In two-dimensional (2D) seepage analysis of embankment dams, little or no attention is paid to the seepage through side abutments. Moreover the role of grout curtain extensions into the side abutments and abutment material properties are inevitably neglected when performing a 2D seepage analysis. In this paper, two and three-dimensional (3D) models of a rockfill dam during operation state are generated and several unsteady and steady state seepage analyses are performed using finite element method (FEM). The results obtained from 2D and 3D seepage analyses were compared with measurements... 

Abutments of concrete arch dams are usually crossed by several joints, which may create some rock wedges. Abutment stability analysis and controlling the probable wedge movements is one of the main concerns in the design procedure of arch dams that should be investigated. For decades, the quasi-static method, due to its simple approach, has been used by most of dam designers. In this study, the dynamic method is presented and the obtained time history of sliding safety factors is compared with the quasi-static results. For this purpose, all three components of Kobe (1979) and Imperial Valley (1940) earthquakes are applied to the wedge, simultaneously, and the magnitude and direction of wedge...