Horizontally curved bridges were investigated following a statistical
evaluation of typical detai... more Horizontally curved bridges were investigated following a statistical evaluation of typical details commonly used in the US. Both seismically and nonseismically designed bridges are considered where the primary differences are in column confinement, type of bearings and abutment support length. Columns and bearings were found to be the most seismically vulnerable components for both categories. Central angle was identified as an important factor that increases the demand on various components, particularly columns. Furthermore, larger angles lead to increased deformations at the supports which adversely affect the seismic vulnerability. Consistent with the fragility curves that account for the central angle explicitly, a second set of system fragility curves were introduced for cases when central angle is not specified such as the case in the National Bridge Inventory. Comparison of fragility parameters to those suggested by HAZUS-MH highlighted the need for revisions to account for current design practices and central angle.
Earthquake Engineering and Engineering Vibration, 2008
It is critical to ensure the functionality of highway bridges after earthquakes to provide access... more It is critical to ensure the functionality of highway bridges after earthquakes to provide access to important facilities. Since the 1971 San Fernando earthquake, there has been a better understanding of the seismic performance of bridges. Nonetheless, there are no detailed guidelines addressing the performance of skewed highway bridges. Several parameters affect the response of skewed highway bridges under both service and seismic loads which makes their behavior complex. Therefore, there is a need for more research to study the effect of skew angle and other related factors on the performance of highway bridges. This paper examines the seismic performance of a three-span continuous concrete box girder bridge with skew angles from 0 to 60 degrees, analytically. Finite element (FE) and simplified beam-stick (BS) models of the bridge were developed using SAP2000. Different types of analysis were considered on both models such as: nonlinear static pushover, and linear and nonlinear time history analyses. A comparison was conducted between FE and BS, different skew angles, abutment support conditions, and time history and pushover analysis. It is shown that the BS model has the capability to capture the coupling due to skew and the significant modes for moderate skew angles. Boundary conditions and pushover load profile are determined to have a major effect on pushover analysis. Pushover analysis may be used to predict the maximum deformation and hinge formation adequately.
... Therefore, economical and effective techniques for retrofitting existing steel bridges are ne... more ... Therefore, economical and effective techniques for retrofitting existing steel bridges are needed in accordance with a no ... Seismic Retrofit of Steel Deck-Truss Bridges: Experimental Investigation ... A wide-band (0 to 50 Hz) white-noise base excitation was used before and after ...
The Triangulated Learning Model is a framework for implementing the engineering analysis and desi... more The Triangulated Learning Model is a framework for implementing the engineering analysis and design process with middle school students in their science classrooms. The model is inquiry-based and integrates the components of simulation, construction, and connection. The model was piloted in eight middle school science classrooms using three teacher-developed modules that included web-based simulations, a construction phase, and specific activities designed to promote connections to underlying scientific and mathematical concepts. This paper describes early indicators of the effectiveness of the model from data collected through classroom observations of the eight teachers.
The Teachers Integrating Engineering into Science (TIES) Program is a collaborative project among... more The Teachers Integrating Engineering into Science (TIES) Program is a collaborative project among faculty from the College of Education and the College of Engineering at the University of Nevada, Reno. The TIES project paired university faculty with middle school science teachers to create three units that included engineering design using a variety of interactive learning activities in order to engage a wide range of students. The units included a Web-based simulation activity, lesson plans, a design project, and three types of assessments that were standardized across schools. Results of assessments were disaggregated by gender, ethnicity, special education, and socio-economic level. Mean scores for these student population groups were compared to mean scores for the same groups on the 2004 Nevada 8 th grade science criterion referenced test. These results indicate that engaging students in engineering curriculum activities may diminish achievement gaps in science for some student populations.
Recent field observations during bridge construction revealed excessive localized deformations in... more Recent field observations during bridge construction revealed excessive localized deformations in sill and cap beams that support falsework posts. Hence, possible limit states associated with flange and web deformations in W and HP sections subjected to patch loading are investigated in this paper. Critical limit states were found to be related to flange bending, post compression, and the interactions associated with patch loading between a beam flange and timber or steel post. Other limit states are associated with web deformations. Two alternative methods based on yield line analyses that establish upper-bound limiting loads for these limit states are proposed. The first method accounts for an interaction between flange bending and post compression strength, whereas the second method uses an effective bearing area of the post. The former method is most effective in characterizing flange-timber posts interactions, while the effective bearing area method was found to be more accurate for steel posts. For beams with relatively thick webs, such as those typically used in bridge falsework, the web was found to have a greater capacity than the flange and post, with the critical web limit state due to web yielding. It was shown that current recommended equations were appropriate with modifications to account for the patch loading condition.
An innovative concept using energy dissipating devices, such as buckling restrained braces (BRB),... more An innovative concept using energy dissipating devices, such as buckling restrained braces (BRB), is proposed for special truss moment frames (STMF). The configuration of the proposed system consists of pins introduced at the ends of the top and bottom chord elements of the special segments. Subsequently, energy dissipating devices are used in the form of diagonal braces inside the special segments. An energybased design methodology is adopted such that the BRBs are designed to provide sufficient energy dissipation capacity with respect to seismic input energy demand on the structure. This energy-based methodology is demonstrated to be accurate by means of a series of nonlinear time-history analyses. The overall seismic response of the proposed system is contrasted with the conventional STMF in terms of story displacements, interstory drifts, story shears and overturning moments, as well as observed damage to structural elements. The proposed system leads to more predictable seismic response and would potentially allow lighter construction and significant cost savings, due to significantly reduced member forces (up to 50% compared with conventional design). Furthermore, damage to structural elements is largely mitigated, hence allowing damage avoidance design of STMFs.
Horizontally curved bridges were investigated following a statistical
evaluation of typical detai... more Horizontally curved bridges were investigated following a statistical evaluation of typical details commonly used in the US. Both seismically and nonseismically designed bridges are considered where the primary differences are in column confinement, type of bearings and abutment support length. Columns and bearings were found to be the most seismically vulnerable components for both categories. Central angle was identified as an important factor that increases the demand on various components, particularly columns. Furthermore, larger angles lead to increased deformations at the supports which adversely affect the seismic vulnerability. Consistent with the fragility curves that account for the central angle explicitly, a second set of system fragility curves were introduced for cases when central angle is not specified such as the case in the National Bridge Inventory. Comparison of fragility parameters to those suggested by HAZUS-MH highlighted the need for revisions to account for current design practices and central angle.
Earthquake Engineering and Engineering Vibration, 2008
It is critical to ensure the functionality of highway bridges after earthquakes to provide access... more It is critical to ensure the functionality of highway bridges after earthquakes to provide access to important facilities. Since the 1971 San Fernando earthquake, there has been a better understanding of the seismic performance of bridges. Nonetheless, there are no detailed guidelines addressing the performance of skewed highway bridges. Several parameters affect the response of skewed highway bridges under both service and seismic loads which makes their behavior complex. Therefore, there is a need for more research to study the effect of skew angle and other related factors on the performance of highway bridges. This paper examines the seismic performance of a three-span continuous concrete box girder bridge with skew angles from 0 to 60 degrees, analytically. Finite element (FE) and simplified beam-stick (BS) models of the bridge were developed using SAP2000. Different types of analysis were considered on both models such as: nonlinear static pushover, and linear and nonlinear time history analyses. A comparison was conducted between FE and BS, different skew angles, abutment support conditions, and time history and pushover analysis. It is shown that the BS model has the capability to capture the coupling due to skew and the significant modes for moderate skew angles. Boundary conditions and pushover load profile are determined to have a major effect on pushover analysis. Pushover analysis may be used to predict the maximum deformation and hinge formation adequately.
... Therefore, economical and effective techniques for retrofitting existing steel bridges are ne... more ... Therefore, economical and effective techniques for retrofitting existing steel bridges are needed in accordance with a no ... Seismic Retrofit of Steel Deck-Truss Bridges: Experimental Investigation ... A wide-band (0 to 50 Hz) white-noise base excitation was used before and after ...
The Triangulated Learning Model is a framework for implementing the engineering analysis and desi... more The Triangulated Learning Model is a framework for implementing the engineering analysis and design process with middle school students in their science classrooms. The model is inquiry-based and integrates the components of simulation, construction, and connection. The model was piloted in eight middle school science classrooms using three teacher-developed modules that included web-based simulations, a construction phase, and specific activities designed to promote connections to underlying scientific and mathematical concepts. This paper describes early indicators of the effectiveness of the model from data collected through classroom observations of the eight teachers.
The Teachers Integrating Engineering into Science (TIES) Program is a collaborative project among... more The Teachers Integrating Engineering into Science (TIES) Program is a collaborative project among faculty from the College of Education and the College of Engineering at the University of Nevada, Reno. The TIES project paired university faculty with middle school science teachers to create three units that included engineering design using a variety of interactive learning activities in order to engage a wide range of students. The units included a Web-based simulation activity, lesson plans, a design project, and three types of assessments that were standardized across schools. Results of assessments were disaggregated by gender, ethnicity, special education, and socio-economic level. Mean scores for these student population groups were compared to mean scores for the same groups on the 2004 Nevada 8 th grade science criterion referenced test. These results indicate that engaging students in engineering curriculum activities may diminish achievement gaps in science for some student populations.
Recent field observations during bridge construction revealed excessive localized deformations in... more Recent field observations during bridge construction revealed excessive localized deformations in sill and cap beams that support falsework posts. Hence, possible limit states associated with flange and web deformations in W and HP sections subjected to patch loading are investigated in this paper. Critical limit states were found to be related to flange bending, post compression, and the interactions associated with patch loading between a beam flange and timber or steel post. Other limit states are associated with web deformations. Two alternative methods based on yield line analyses that establish upper-bound limiting loads for these limit states are proposed. The first method accounts for an interaction between flange bending and post compression strength, whereas the second method uses an effective bearing area of the post. The former method is most effective in characterizing flange-timber posts interactions, while the effective bearing area method was found to be more accurate for steel posts. For beams with relatively thick webs, such as those typically used in bridge falsework, the web was found to have a greater capacity than the flange and post, with the critical web limit state due to web yielding. It was shown that current recommended equations were appropriate with modifications to account for the patch loading condition.
An innovative concept using energy dissipating devices, such as buckling restrained braces (BRB),... more An innovative concept using energy dissipating devices, such as buckling restrained braces (BRB), is proposed for special truss moment frames (STMF). The configuration of the proposed system consists of pins introduced at the ends of the top and bottom chord elements of the special segments. Subsequently, energy dissipating devices are used in the form of diagonal braces inside the special segments. An energybased design methodology is adopted such that the BRBs are designed to provide sufficient energy dissipation capacity with respect to seismic input energy demand on the structure. This energy-based methodology is demonstrated to be accurate by means of a series of nonlinear time-history analyses. The overall seismic response of the proposed system is contrasted with the conventional STMF in terms of story displacements, interstory drifts, story shears and overturning moments, as well as observed damage to structural elements. The proposed system leads to more predictable seismic response and would potentially allow lighter construction and significant cost savings, due to significantly reduced member forces (up to 50% compared with conventional design). Furthermore, damage to structural elements is largely mitigated, hence allowing damage avoidance design of STMFs.
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Papers by Gokhan Pekcan
evaluation of typical details commonly used in the US. Both seismically and nonseismically
designed bridges are considered where the primary differences are in
column confinement, type of bearings and abutment support length. Columns and
bearings were found to be the most seismically vulnerable components for both
categories. Central angle was identified as an important factor that increases the
demand on various components, particularly columns. Furthermore, larger angles
lead to increased deformations at the supports which adversely affect the seismic
vulnerability. Consistent with the fragility curves that account for the central
angle explicitly, a second set of system fragility curves were introduced for cases
when central angle is not specified such as the case in the National Bridge
Inventory. Comparison of fragility parameters to those suggested by HAZUS-MH
highlighted the need for revisions to account for current design practices and
central angle.
evaluation of typical details commonly used in the US. Both seismically and nonseismically
designed bridges are considered where the primary differences are in
column confinement, type of bearings and abutment support length. Columns and
bearings were found to be the most seismically vulnerable components for both
categories. Central angle was identified as an important factor that increases the
demand on various components, particularly columns. Furthermore, larger angles
lead to increased deformations at the supports which adversely affect the seismic
vulnerability. Consistent with the fragility curves that account for the central
angle explicitly, a second set of system fragility curves were introduced for cases
when central angle is not specified such as the case in the National Bridge
Inventory. Comparison of fragility parameters to those suggested by HAZUS-MH
highlighted the need for revisions to account for current design practices and
central angle.