A Nonlinear Analysis Method for Perfomance Based Seismic Design Download File
A Simple Seismic Desiogn Strategy Based on Displancement and Ductility Compatibility
Download File
Senin, 20 September 2010
Design Charts for Open - Channel Flow HDS 3 August 1961
Design of Highway Drainage Channels
The design of a highway drainage channel to carry a given discharge is accomplished in two
parts. The first part of the design involves the computation of a channel section which will carry
the design discharge on the available slope. This chapter briefly discusses the principles of flow
in open channels and the use of the Manning equation for computing the channel capacity.
The second part of the design is the determination of the degree of protection required to
prevent erosion in the drainage channel. This can be done by computing the velocity in the
channel at the design discharge, using the Manning equation, and comparing the calculated
velocity with that permissible for the type of channel lining used. (Permissible velocities are
shown in Table 2 and Table 3.) A change in the type of channel lining will require a change in
channel size unless both linings have the same roughness coefficient.
Types of Flow
Flow in open channels is classified as steady or unsteady. The flow is said to be steady when
the rate of discharge is not varying with time. In this chapter, the flow will be assumed to be
steady at the discharge rate for which the channel is to be designed. Steady flow is further
classified as uniform when the channel cross section, roughness, and slope are constant; and
as nonuniform or varied when the channel properties vary from section to section.
Depth of flow and the mean velocity will be constant for steady flow in a uniform channel.
Download File
The design of a highway drainage channel to carry a given discharge is accomplished in two
parts. The first part of the design involves the computation of a channel section which will carry
the design discharge on the available slope. This chapter briefly discusses the principles of flow
in open channels and the use of the Manning equation for computing the channel capacity.
The second part of the design is the determination of the degree of protection required to
prevent erosion in the drainage channel. This can be done by computing the velocity in the
channel at the design discharge, using the Manning equation, and comparing the calculated
velocity with that permissible for the type of channel lining used. (Permissible velocities are
shown in Table 2 and Table 3.) A change in the type of channel lining will require a change in
channel size unless both linings have the same roughness coefficient.
Types of Flow
Flow in open channels is classified as steady or unsteady. The flow is said to be steady when
the rate of discharge is not varying with time. In this chapter, the flow will be assumed to be
steady at the discharge rate for which the channel is to be designed. Steady flow is further
classified as uniform when the channel cross section, roughness, and slope are constant; and
as nonuniform or varied when the channel properties vary from section to section.
Depth of flow and the mean velocity will be constant for steady flow in a uniform channel.
Download File
HYDRAULICS IN CIVIL AND ENVIRONMENTAL ENGINEERNG
HYDRAULICS IN CIVIL AND ENVIRONMENTAL ENGINEERNG
This manual has been prepared for use in cojunction with the textbook
HYDRAULICS IN CIVIL AND ENVIRONMENTAL ENGINEERNG (4th editon).
The problems for solution in the book cover the material found in Chapters 1-11
The solutions manual is particularly inteded for use by course tutors.
It provides detailed method of solution for all of the problems in the 4th edition,
so that they can be integrated into the tutorial scheme for a hydraulics lecture programme.
Download File
This manual has been prepared for use in cojunction with the textbook
HYDRAULICS IN CIVIL AND ENVIRONMENTAL ENGINEERNG (4th editon).
The problems for solution in the book cover the material found in Chapters 1-11
The solutions manual is particularly inteded for use by course tutors.
It provides detailed method of solution for all of the problems in the 4th edition,
so that they can be integrated into the tutorial scheme for a hydraulics lecture programme.
Download File
RIVER ENGINEERING FOR HIGHWAY ENCROACHMENTS
The purpose of this chapter is to lay the groundwork for application of the concepts of
open-channel flow, fluvial geomorphology, sediment transport, and river mechanics to the
design, maintenance, and environmental problems associated with highway crossings and
encroachments.
This manual is a basic reference for related Federal Highway Administration (FHWA) hydraulic
publications and National Highway Institute (NHI) Hydraulics Courses. Some of these
publications are: "Hydraulics of Bridge Waterways" (Bradley 1978), "Design of Riprap
Revetment" (Brown and Clyde 1989), "Evaluating Scour at Bridges" (Richardson and Davis
2001), "Stream Stability at Highway Structures" (Lagasse et al. 2001), "Bridge Scour and
Stream Instability Countermeasures - Experience, Selection and Design Guidance" (Lagasse
et al. 2001). Related NHI courses include:
(1) River Engineering for Highway Encroachments,
(2) Stream Stability and Scour at Highway Bridges, and
(3) Finite Element Surface Water
Modeling System (FESWMS).
Basic definitions of terms and notations adopted for use in this document have been presented
in the preceding section (Glossary) for rapid reference. Additionally, these important terms and
variables are defined and explained as they are encountered.
Download File
open-channel flow, fluvial geomorphology, sediment transport, and river mechanics to the
design, maintenance, and environmental problems associated with highway crossings and
encroachments.
This manual is a basic reference for related Federal Highway Administration (FHWA) hydraulic
publications and National Highway Institute (NHI) Hydraulics Courses. Some of these
publications are: "Hydraulics of Bridge Waterways" (Bradley 1978), "Design of Riprap
Revetment" (Brown and Clyde 1989), "Evaluating Scour at Bridges" (Richardson and Davis
2001), "Stream Stability at Highway Structures" (Lagasse et al. 2001), "Bridge Scour and
Stream Instability Countermeasures - Experience, Selection and Design Guidance" (Lagasse
et al. 2001). Related NHI courses include:
(1) River Engineering for Highway Encroachments,
(2) Stream Stability and Scour at Highway Bridges, and
(3) Finite Element Surface Water
Modeling System (FESWMS).
Basic definitions of terms and notations adopted for use in this document have been presented
in the preceding section (Glossary) for rapid reference. Additionally, these important terms and
variables are defined and explained as they are encountered.
Download File
Minggu, 05 September 2010
Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance-Third Edition Volume 2
In this volume design guidelines are provided for a variety of stream instability and bridge
scour countermeasures. Most of these countermeasures have been applied successfully on
a state or regional basis, but, in several cases, only limited design references are available in
published handbooks, manuals, or reports. No attempt has been made to include in this
document design guidelines for all the countermeasures listed or referenced in Volume 1.
Countermeasure design guidelines formerly presented in HEC-20 (spurs, guide banks, drop
structures) and in HEC-18 (riprap at abutments and piers) are now consolidated in this
document. Since many bridge scour and stream instability countermeasures require riprap
revetment as an integral component of the countermeasure, riprap revetment design
guidance is summarized in Design Guideline 4. An appropriate granular or geotextile filter is
essential for any countermeasure requiring a protective armor layer (e.g., riprap, articulating
concrete blocks, etc.). Filter design guidance is provided in Design Guideline 16.
Design Guideline 8 – Articulating Concrete Block Systems, Design Guideline 9 –
Grout-Filled Mattresses, and Design Guideline 10 – Gabion Mattresses each contain
two countermeasure applications: (1) bankline revetment or bed armor, and (2) pier
scour protection. Consequently, these three design guidelines appear in Section 2,
but are referenced in Section 3 with a page citation to the pier protection application.
A number of highway agencies provided specifications, procedures, or design guidelines for
bridge scour and stream instability countermeasures that have been used successfully
locally, but for which only limited design guidance is available outside the agency. Several of
these are presented as design guidelines for the consideration of and possible adaptation to
the needs of other highway agencies (see for example, Design Guideline 6, Wire Enclosed
Riprap Mattress, and Design Guideline 13, Grout/Cement Filled Bags). These specifications,
procedures, or guidelines have not been evaluated, tested, or endorsed by the authors of
this document or by the FHWA. They are presented here in the interests of information
transfer on countermeasures that may have application in another state or region.
Since publication of the Second Edition of HEC-23 in 2001, both the Transportation
Research Board through the NCHRP Program and FHWA have sponsored a number of
research projects to improve the state of practice in bridge scour and stream instability
countermeasure technology and provide definitive guidance to bridge owners in
countermeasure design. Among the projects that represent advances in countermeasure
technology that have been incorporated into the Design Guidelines are:
• NCHRP Report 544 - Environmentally Sensitive Channel and Bank Protection Measures
• NCHRP Report 568 - Riprap Design Criteria, Specifications, and Quality Control
• NCHRP Report 587 - Countermeasures to Protect Bridge Abutments from Scour
• NCHRP Report 593 - Countermeasures to Protect Bridge Piers from Scour
Download File
scour countermeasures. Most of these countermeasures have been applied successfully on
a state or regional basis, but, in several cases, only limited design references are available in
published handbooks, manuals, or reports. No attempt has been made to include in this
document design guidelines for all the countermeasures listed or referenced in Volume 1.
Countermeasure design guidelines formerly presented in HEC-20 (spurs, guide banks, drop
structures) and in HEC-18 (riprap at abutments and piers) are now consolidated in this
document. Since many bridge scour and stream instability countermeasures require riprap
revetment as an integral component of the countermeasure, riprap revetment design
guidance is summarized in Design Guideline 4. An appropriate granular or geotextile filter is
essential for any countermeasure requiring a protective armor layer (e.g., riprap, articulating
concrete blocks, etc.). Filter design guidance is provided in Design Guideline 16.
Design Guideline 8 – Articulating Concrete Block Systems, Design Guideline 9 –
Grout-Filled Mattresses, and Design Guideline 10 – Gabion Mattresses each contain
two countermeasure applications: (1) bankline revetment or bed armor, and (2) pier
scour protection. Consequently, these three design guidelines appear in Section 2,
but are referenced in Section 3 with a page citation to the pier protection application.
A number of highway agencies provided specifications, procedures, or design guidelines for
bridge scour and stream instability countermeasures that have been used successfully
locally, but for which only limited design guidance is available outside the agency. Several of
these are presented as design guidelines for the consideration of and possible adaptation to
the needs of other highway agencies (see for example, Design Guideline 6, Wire Enclosed
Riprap Mattress, and Design Guideline 13, Grout/Cement Filled Bags). These specifications,
procedures, or guidelines have not been evaluated, tested, or endorsed by the authors of
this document or by the FHWA. They are presented here in the interests of information
transfer on countermeasures that may have application in another state or region.
Since publication of the Second Edition of HEC-23 in 2001, both the Transportation
Research Board through the NCHRP Program and FHWA have sponsored a number of
research projects to improve the state of practice in bridge scour and stream instability
countermeasure technology and provide definitive guidance to bridge owners in
countermeasure design. Among the projects that represent advances in countermeasure
technology that have been incorporated into the Design Guidelines are:
• NCHRP Report 544 - Environmentally Sensitive Channel and Bank Protection Measures
• NCHRP Report 568 - Riprap Design Criteria, Specifications, and Quality Control
• NCHRP Report 587 - Countermeasures to Protect Bridge Abutments from Scour
• NCHRP Report 593 - Countermeasures to Protect Bridge Piers from Scour
Download File
Sabtu, 04 September 2010
Refined 3D finite element modeling of partially restrained connections including slip
The effect of partially-restrained (PR) connections on the behavior of steel frames
and their potential economical benefits is well recognized [18]. However, many structural
analysis and design approaches still consider connections as either fixed or
pinned. This assumption is mainly due to convenience and the lack of common
analysis and design approaches that address PR connections. Despite many full-scale
experimental studies that have been conducted to date, there is still a need for a
better understanding of the mechanisms that effect the non-linear behavior of PR
connections [8].
Non-linear moment rotation response of connections was recognized in the early
1930s. Standardized functions have been developed starting from basic linear and
bilinear approximations to more sophisticated models based on polynomials, cubic
B-splines and power functions fitted to available experimental data. Sherbourne and
Bahaari [13] have recently presented a review of these functions. Frye and Morris
[9] were among the first to incorporate these standardized moment–rotation functions
in steel plane frame analysis to investigate the effect of the connections on the
frame behavior.
Moment rotation functions can be useful for designers in practice. These usually
include small number of parameters taken into account from limited test data. The
lack of a large and parametrized experimental database does not allow for generating
standardized functions. Thus, there is a need to be able to analytically generate a
reliable moment–rotation response of PR connections that can be used in analysis
and design.
Non-linear finite elements are an attractive tool for modeling connections. Early
attempts to use finite elements for analysis of PR connections was by Krishnamurthy
[11]. As in many early studies using finite elements, many simplifications are made
due to the limitations of computational power. More recent studies using finite
elements in modeling connections have focused on end plate connections
[6,7,10,13,14]. In these studies 2D and 3D models are used with various simplifications
in the geometry of members, the bolts, and contact conditions. The effect
of friction on the response of end plate connections is usually neglected in these
models [7,10].
Azizinamini [3–5] preformed an extensive and detailed experimental study for top
and bottom seat angle connections with double web angles along with pull tests. In
addition, simplified 3D FE models for the pull tests are also studied. One quarter of
the top angle in the connection is modeled with 3D elements to simulate a pull test.
The force–displacement relation was converted to a moment–rotation relation in
order to examine the role of the top angle on the behavior of the connection and
approximate the overall response of the connection with a pull test. Different assumptions
and simplifications are made in order to avoid detailed modeling and reduce
the computational effort.
Yang et al. [19] consider a double web angle connection where the angles are
bolted to the column flanges and welded to the beam web. The bolts and angle are
modeled using 3D finite elements and wedge elements are used to model the weld
region. Contact is included between the bolt head and angle. However, the contact
between the bolt shank and hole is ignored.
In the studies on end plate connections and the double web angle connection, the
bolts are transferring the loads axially, thus eliminating the need for combined contact
and friction modeling between the bolts and members. These models are therefore
limited to these types of PR connections. The bolted connections tested by
Azizinamini et al. [4,5] are investigated in this study. These top–bottom bolted seat
angle connections transfer the forces by friction by clamping the parts together with
the bolts. Modeling such a mechanism requires the inclusion of contact and slip
between the connection members.
In this study, a refined 3D modeling of PR bolted connections are performed
recognizing contact and friction effects. The modeling approach is general and capable
of modeling various types of geometries of PR connections by using parametric
meshing techniques. Therefore the time of generating detailed 3D geometries is
almost eliminated. A calibration method for the pretension of the bolts is presented.
In this method, parametric solutions are first generated separately for a single bolt
clamping semi-infinite plates. These solutions are used to specify initial pretension
values for the bolts in the full connection. The correct pretension values are then
examined and corrected in the full connection model to achieve accurate final values.
It is shown in this study that the response of the bolted PR connections are sensitive
to the pretension of the bolts, thus correctly modeling the pretension and slip is
important.
Download File
and their potential economical benefits is well recognized [18]. However, many structural
analysis and design approaches still consider connections as either fixed or
pinned. This assumption is mainly due to convenience and the lack of common
analysis and design approaches that address PR connections. Despite many full-scale
experimental studies that have been conducted to date, there is still a need for a
better understanding of the mechanisms that effect the non-linear behavior of PR
connections [8].
Non-linear moment rotation response of connections was recognized in the early
1930s. Standardized functions have been developed starting from basic linear and
bilinear approximations to more sophisticated models based on polynomials, cubic
B-splines and power functions fitted to available experimental data. Sherbourne and
Bahaari [13] have recently presented a review of these functions. Frye and Morris
[9] were among the first to incorporate these standardized moment–rotation functions
in steel plane frame analysis to investigate the effect of the connections on the
frame behavior.
Moment rotation functions can be useful for designers in practice. These usually
include small number of parameters taken into account from limited test data. The
lack of a large and parametrized experimental database does not allow for generating
standardized functions. Thus, there is a need to be able to analytically generate a
reliable moment–rotation response of PR connections that can be used in analysis
and design.
Non-linear finite elements are an attractive tool for modeling connections. Early
attempts to use finite elements for analysis of PR connections was by Krishnamurthy
[11]. As in many early studies using finite elements, many simplifications are made
due to the limitations of computational power. More recent studies using finite
elements in modeling connections have focused on end plate connections
[6,7,10,13,14]. In these studies 2D and 3D models are used with various simplifications
in the geometry of members, the bolts, and contact conditions. The effect
of friction on the response of end plate connections is usually neglected in these
models [7,10].
Azizinamini [3–5] preformed an extensive and detailed experimental study for top
and bottom seat angle connections with double web angles along with pull tests. In
addition, simplified 3D FE models for the pull tests are also studied. One quarter of
the top angle in the connection is modeled with 3D elements to simulate a pull test.
The force–displacement relation was converted to a moment–rotation relation in
order to examine the role of the top angle on the behavior of the connection and
approximate the overall response of the connection with a pull test. Different assumptions
and simplifications are made in order to avoid detailed modeling and reduce
the computational effort.
Yang et al. [19] consider a double web angle connection where the angles are
bolted to the column flanges and welded to the beam web. The bolts and angle are
modeled using 3D finite elements and wedge elements are used to model the weld
region. Contact is included between the bolt head and angle. However, the contact
between the bolt shank and hole is ignored.
In the studies on end plate connections and the double web angle connection, the
bolts are transferring the loads axially, thus eliminating the need for combined contact
and friction modeling between the bolts and members. These models are therefore
limited to these types of PR connections. The bolted connections tested by
Azizinamini et al. [4,5] are investigated in this study. These top–bottom bolted seat
angle connections transfer the forces by friction by clamping the parts together with
the bolts. Modeling such a mechanism requires the inclusion of contact and slip
between the connection members.
In this study, a refined 3D modeling of PR bolted connections are performed
recognizing contact and friction effects. The modeling approach is general and capable
of modeling various types of geometries of PR connections by using parametric
meshing techniques. Therefore the time of generating detailed 3D geometries is
almost eliminated. A calibration method for the pretension of the bolts is presented.
In this method, parametric solutions are first generated separately for a single bolt
clamping semi-infinite plates. These solutions are used to specify initial pretension
values for the bolts in the full connection. The correct pretension values are then
examined and corrected in the full connection model to achieve accurate final values.
It is shown in this study that the response of the bolted PR connections are sensitive
to the pretension of the bolts, thus correctly modeling the pretension and slip is
important.
Download File
A simple shear wall model taking into account stiffness degradation
Complex destructive phenomena take place in
reinforced concrete structures during earthquake excitations.
These include concrete cracking, interaction
effects between steel and concrete, steel yielding and
concrete crushing in compression. The damage generated
can be translated into a damage variable which takes
the local destructive effects into account in a global manner.
As damage increases within the reinforced concrete
structure, the alteration of the mechanical characteristics
yields modal characteristics changes. In this way, Chen
et al. [1] investigated the structural damage by means of
the identification method of modal changes. At a critical
damage level, they indicated that a decrease of the fundamental
frequency up to 10% can be expected for steel
beams. For reinforced concrete structures, the fundamen-
tal frequency reduction, related to the structural damage
can be significantly larger. Pseudodynamic tests carried
out at the European Laboratory for Structural Assessment
(JRC-Ispra) in fact showed fundamental frequency
reductions of more than 60% (Pegon et al. [2]). Such
fundamental frequency decrease strongly influences the
dynamic response of the structure subjected to a seismic
excitation.
In this paper, a simplified model for a particular lowrise
heavily reinforced shear wall is proposed. Its original
formulation is based explicitly on changes in fundamental
frequency according to a pertinent damage variable.
First of all, a detailed finite element analysis is
carried out with constitutive local models taking into
account the main destructive phenomena involved during
seismic excitation. The relevance of the modelling
is evaluated by comparing numerical results with experimental
available data. The following stage is devoted
to the identification of the decrease of the fundamental
frequency. This is realised by applying the finite element
modelling of the wall to a variety of ideal excitations
composed of sinusoidal cycles. The numerical results
allow to identify in a robust manner the decrease of the
fundamental frequency as a function of damage. Then,
this function is introduced in a simple dynamic uniaxial
model, expressed in terms of displacements at the top of
the wall. In the final stage, the validity of the proposed
simplified model is assessed by comparing numerical
results with experimental results in a first time, and, in
a second time, with the results issued from fine finite
element analyses for different types of seismic excitations.
Download File
reinforced concrete structures during earthquake excitations.
These include concrete cracking, interaction
effects between steel and concrete, steel yielding and
concrete crushing in compression. The damage generated
can be translated into a damage variable which takes
the local destructive effects into account in a global manner.
As damage increases within the reinforced concrete
structure, the alteration of the mechanical characteristics
yields modal characteristics changes. In this way, Chen
et al. [1] investigated the structural damage by means of
the identification method of modal changes. At a critical
damage level, they indicated that a decrease of the fundamental
frequency up to 10% can be expected for steel
beams. For reinforced concrete structures, the fundamen-
tal frequency reduction, related to the structural damage
can be significantly larger. Pseudodynamic tests carried
out at the European Laboratory for Structural Assessment
(JRC-Ispra) in fact showed fundamental frequency
reductions of more than 60% (Pegon et al. [2]). Such
fundamental frequency decrease strongly influences the
dynamic response of the structure subjected to a seismic
excitation.
In this paper, a simplified model for a particular lowrise
heavily reinforced shear wall is proposed. Its original
formulation is based explicitly on changes in fundamental
frequency according to a pertinent damage variable.
First of all, a detailed finite element analysis is
carried out with constitutive local models taking into
account the main destructive phenomena involved during
seismic excitation. The relevance of the modelling
is evaluated by comparing numerical results with experimental
available data. The following stage is devoted
to the identification of the decrease of the fundamental
frequency. This is realised by applying the finite element
modelling of the wall to a variety of ideal excitations
composed of sinusoidal cycles. The numerical results
allow to identify in a robust manner the decrease of the
fundamental frequency as a function of damage. Then,
this function is introduced in a simple dynamic uniaxial
model, expressed in terms of displacements at the top of
the wall. In the final stage, the validity of the proposed
simplified model is assessed by comparing numerical
results with experimental results in a first time, and, in
a second time, with the results issued from fine finite
element analyses for different types of seismic excitations.
Download File
Langganan:
Postingan (Atom)