Influence of Transient and Partial Footing Separation on the Seismic Response of Skewed Bridges with Soil Support

2021 ◽  
pp. 2150132
Author(s):  
Ziqi Yang ◽  
Chern Kun ◽  
Dongliang Meng ◽  
Nawawi Chouw
Keyword(s):  
Seismic Response ◽  
Large Scale ◽  
Bending Moment ◽  
Bridge Piers ◽  
Seismic Load ◽  
Skew Angle ◽  
Skewed Bridges ◽  
Design Spectrum ◽  
Bridge Structures ◽  
The Impact

Previous research has shown that the transient and partial footing separation is one of the effective methods to reduce the impact of earthquakes on bridge structures. The separation will not only temporarily stop the transfer of seismic load to structures, but also activate rigid-like body motions of the bridge piers. Most of current investigations involving footing uplift only focused on straight bridges. The influence of skew angle is rarely considered. Even though skewed bridges are common and more vulnerable to seismic load. This work reveals the simultaneous influence of skew angle and footing uplift on soil on seismic response of bridges. A bridge with a 30∘ or 45∘ skew angle, in addition to a straight bridge, was excited using a large-scale shake table. The ground excitations were stochastically simulated based on design spectrum of New Zealand standard. The result revealed that with increasing skew angle bridges will have frequent footing uplifts. In the case of a straight bridge, although allowing footing uplift is beneficial in reducing the bending moment at the pier support, it increases the longitudinal girder displacement. In contrast, in the case of 30∘ and 45∘ skewed bridges, uplifts increase the bending moments of piers and the displacements of the girder, especially in the transverse direction.

Seismic response of concentrically braced dual steel frames

1993 ◽  
Vol 20 (4) ◽  
pp. 672-687 ◽  
Author(s):  
A. K. Jain ◽  
R. G. Redwood ◽  
Feng Lu
Keyword(s):  
Seismic Response ◽  
Steel Frames ◽  
Dual System ◽  
Seismic Load ◽  
Braced Frame ◽  
Moment Resisting Frame ◽  
Inelastic Analysis ◽  
Concentrically Braced ◽  
Moment Resisting ◽  
The Impact

Concentrically braced steel frames are one of the most commonly used structural systems because of their structural efficiency, simplicity to analyze and design, and ease of construction and repair. Canadian design codes provide specifications for their design under seismic loading based on the large amount of knowledge related to their seismic response accumulated over the past two decades. This paper examines the impact of a dual system with a moment resisting frame acting in parallel with the concentrically braced frame. Four different frames were designed in accordance with the National Building Code of Canada and CSA-S16.1-M89, and their inelastic responses are studied under the action of both monotonically increasing load and seismic load. The relative strengths and stiffnesses of the frames comprising the dual systems were varied. The ductility demands on members, and overall building deflections and storey drifts, were examined under the action of ten earthquake records. It is concluded that improved performance such as reduced ductility demand and improved uniformity of the distribution of yield throughout the structure can be achieved. However, the stiffness and strength in the moment resisting frame necessary to provide marked improvement must be a significant proportion of those of the braced frame. Key words: structural engineering, earthquakes, inelastic analysis, concentric bracing, dual system, steel, buckling.

scholarly journals Impact of armour layer on the depth of scour hole around side-by-side bridge piers under ice-covered flow condition

2019 ◽  
Vol 67 (3) ◽  
pp. 240-251
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Grain Size ◽  
Froude Number ◽  
Large Scale ◽  
Bridge Piers ◽  
Scour Depth ◽  
Flow Conditions ◽  
Densimetric Froude Number ◽  
Open Flow ◽  
Scour Holes ◽  
The Impact

Abstract In the present study, experiments were conducted in a large-scale flume to investigate the issue of local scour around side-by-side bridge piers under both ice-covered and open flow conditions. Three non-uniform sediments were used in this experimental study. Analysis of armour layer in the scour holes around bridge piers was performed to inspect the grain size distribution curves and to study the impact of armour layer on scour depth. Assessments of grain size of deposition ridges at the downstream side of bridge piers have been conducted. Based on data collected in 108 experiments, the independent variables associated with maximum scour depth were assessed. Results indicate that the densi-metric Froude number was the most influential parameter on the maximum scour depth. With the increase in grain size of the armour layer, ice cover roughness and the densimetric Froude number, the maximum scour depth around bridge piers increases correspondingly. Equations have been developed to determine the maximum scour depth around bridge piers under both open flow and ice covered conditions.

scholarly journals Experimental Evaluation of the Seismic Response of Skewed Bridges with Emphasis on Poundings between Girder and Abutments

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Ziqi Yang ◽  
Chern Kun ◽  
Nawawi Chouw
Keyword(s):  
Seismic Response ◽  
Experimental Research ◽  
Experimental Evaluation ◽  
Shake Table ◽  
Skew Angle ◽  
Shake Table Tests ◽  
Skewed Bridges ◽  
Single Frame ◽  
Bridge Model ◽  
Skew Angles

Observations from past earthquake events indicate that skewed bridges are seismically vulnerable due to induced horizontal in-plane rotations of the girder. To date, however, very limited experimental research has been done on the pounding behaviour of skewed bridges. In this study, shake table tests were performed on a single-frame bridge model with adjacent abutments subjected to uniform ground excitations. Bridges with different skew angles, i.e., 0°, 30°, and 45°, were considered. The pounding behaviour was observed using a pair of pounding and measuring heads. The results reveal that poundings could indeed influence the responses of skewed bridges in the longitudinal and transverse directions differently and thus affect the development of the girder rotations. Ignoring pounding effects, the 30° skewed bridges could experience more girder rotations than the 45° skewed bridges. With pounding, the bridges with a large skew angle could suffer more opening girder displacements than straight bridges.

scholarly journals Effect of Skew Angles on Longitudinal Girder and Deck Slab of Prestressed Concrete T Beam Girder Bridges

2021 ◽  
Vol 9 (10) ◽  
pp. 414-420
Author(s):  
Ms. Ashwini Hanchate
Keyword(s):  
Prestressed Concrete ◽  
Bridge Decks ◽  
Bending Moment ◽  
Torsional Moment ◽  
Skew Angle ◽  
Skewed Bridges ◽  
Girder Bridges ◽  
Longitudinal Bending ◽  
Skew Angles ◽  
Deck Slab

Abstract: The present paper shows the effects of varying skew angles on pre-stressed concrete (PSC) bridges using finite elemental method. Studies are carried out on PSC bridge decks to understand the influence of skew angle and loading on behaviour of bridges. The results of skewed bridges are compared with straight bridges for IRC Class AA Tracked loading. Also, a comparative analysis of the response of skewed PSC Slab Bridge decks with that of equivalent straight bridge decks is made. The variation of maximum longitudinal bending moment (BM), maximum transverse moment, maximum torsional moment, and maximum longitudinal stresses deflection at obtuse corner, acute corner with skew angles are studied for bridge deck. It is found that Live load longitudinal bending moments decreases with an increase in skew angle, whereas a maximum transverse moment and maximum torsional moment increases with an increase in skew angle. The benefit of pre-stressing is reflected in considerable decrease in the longitudinal bending moment, transverse moment and longitudinal stresses. The models are analysed with the help of software CSI-Bridge V 20 Version. Keywords: Skew angle effect, Longitudinal moment, Transverse moment, CSI- Bridge software, Deck slab, Finite element method.

Measuring and estimating the impact pressure of debris flows on bridge piers based on large-scale laboratory experiments

Landslides ◽  
2018 ◽  
Vol 15 (7) ◽  
pp. 1331-1345 ◽  
Author(s):  
Dongpo Wang ◽  
Zheng Chen ◽  
Siming He ◽  
Yang Liu ◽  
Hao Tang
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Impact Pressure ◽  
Bridge Piers ◽  
The Impact

scholarly journals NHERI@UC San Diego 6-DOF Large High-Performance Outdoor Shake Table Facility

2021 ◽  
Vol 6 ◽  
Author(s):  
Lelli Van Den Einde ◽  
Joel P. Conte ◽  
José I. Restrepo ◽  
Ricardo Bustamante ◽  
Marty Halvorson ◽  
...  
Keyword(s):  
Seismic Response ◽  
Earthquake Engineering ◽  
San Diego ◽  
High Performance ◽  
Large Scale ◽  
Computational Models ◽  
Disaster Mitigation ◽  
Structural Systems ◽  
Shake Table ◽  
The Impact

Since its commissioning in 2004, the UC San Diego Large High-Performance Outdoor Shake Table (LHPOST) has enabled the seismic testing of large structural, geostructural and soil-foundation-structural systems, with its ability to accurately reproduce far- and near-field ground motions. Thirty-four (34) landmark projects were conducted on the LHPOST as a national shared-use equipment facility part of the National Science Foundation (NSF) Network for Earthquake Engineering Simulation (NEES) and currently Natural Hazards Engineering Research Infrastructure (NHERI) programs, and an ISO/IEC Standard 17025:2005 accredited facility. The tallest structures ever tested on a shake table were conducted on the LHPOST, free from height restrictions. Experiments using the LHPOST generate essential knowledge that has greatly advanced seismic design practice and response predictive capabilities for structural, geostructural, and non-structural systems, leading to improved earthquake safety in the community overall. Indeed, the ability to test full-size structures has made it possible to physically validate the seismic performance of various systems that previously could only be studied at reduced scale or with computer models. However, the LHPOST's limitation of 1-DOF (uni-directional) input motion prevented the investigation of important aspects of the seismic response of 3-D structural systems. The LHPOST was originally conceived as a six degrees-of-freedom (6-DOF) shake table but built as a single degree-of-freedom (1-DOF) system due to budget limitations. The LHPOST is currently being upgraded to 6-DOF capabilities. The 6-DOF upgraded LHPOST (LHPOST6) will create a unique, large-scale, high-performance, experimental research facility that will enable research for the advancement of the science, technology, and practice in earthquake engineering. Testing of infrastructure at large scale under realistic multi-DOF seismic excitation is essential to fully understand the seismic response behavior of civil infrastructure systems. The upgraded 6-DOF capabilities will enable the development, calibration, and validation of predictive high-fidelity mathematical/computational models, and verifying effective methods for earthquake disaster mitigation and prevention. Research conducted using the LHPOST6 will improve design codes and construction standards and develop accurate decision-making tools necessary to build and maintain sustainable and disaster-resilient communities. Moreover, it will support the advancement of new and innovative materials, manufacturing methods, detailing, earthquake protective systems, seismic retrofit methods, and construction methods. This paper will provide a brief overview of the 1-DOF LHPOST and the impact of some past landmark projects. It will also describe the upgrade to 6-DOF and the new seismic research and testing that the LHPOST6 facility will enable.

Impact of COVID-19 on Nuclear Medicine in Germany, Austria and Switzerland: An International Survey in April 2020

2020 ◽  
Vol 59 (04) ◽  
pp. 294-299 ◽  
Author(s):  
Lutz S. Freudenberg ◽  
Ulf Dittmer ◽  
Ken Herrmann
Keyword(s):  
Nuclear Medicine ◽  
Health Systems ◽  
Personal Protective Equipment ◽  
Large Scale ◽  
Diagnostic Procedures ◽  
Protective Equipment ◽  
Current Crisis ◽  
Web Based ◽  
Public Versus Private ◽  
The Impact

Abstract Introduction Preparations of health systems to accommodate large number of severely ill COVID-19 patients in March/April 2020 has a significant impact on nuclear medicine departments. Materials and Methods A web-based questionnaire was designed to differentiate the impact of the pandemic on inpatient and outpatient nuclear medicine operations and on public versus private health systems, respectively. Questions were addressing the following issues: impact on nuclear medicine diagnostics and therapy, use of recommendations, personal protective equipment, and organizational adaptations. The survey was available for 6 days and closed on April 20, 2020. Results 113 complete responses were recorded. Nearly all participants (97 %) report a decline of nuclear medicine diagnostic procedures. The mean reduction in the last three weeks for PET/CT, scintigraphies of bone, myocardium, lung thyroid, sentinel lymph-node are –14.4 %, –47.2 %, –47.5 %, –40.7 %, –58.4 %, and –25.2 % respectively. Furthermore, 76 % of the participants report a reduction in therapies especially for benign thyroid disease (-41.8 %) and radiosynoviorthesis (–53.8 %) while tumor therapies remained mainly stable. 48 % of the participants report a shortage of personal protective equipment. Conclusions Nuclear medicine services are notably reduced 3 weeks after the SARS-CoV-2 pandemic reached Germany, Austria and Switzerland on a large scale. We must be aware that the current crisis will also have a significant economic impact on the healthcare system. As the survey cannot adapt to daily dynamic changes in priorities, it serves as a first snapshot requiring follow-up studies and comparisons with other countries and regions.

HOME VISITS DURING THE FIRST MONTH OF DELIVERY FOR RECENTLY DELIVERED WOMEN IN UTTAR PRADESH, INDIA

2020 ◽  
Vol 6 (5) ◽  
pp. 1183-1189
Author(s):  
Dr. Tridibesh Tripathy ◽  
Dr. Umakant Prusty ◽  
Dr. Chintamani Nayak ◽  
Dr. Rakesh Dwivedi ◽  
Dr. Mohini Gautam
Keyword(s):  
Large Scale ◽  
National Level ◽  
Uttar Pradesh ◽  
Life Time ◽  
Structured Interview ◽  
The Other ◽  
Registration System ◽  
Action Group ◽  
Current Article ◽  
The Impact

The current article of Uttar Pradesh (UP) is about the ASHAs who are the daughters-in-law of a family that resides in the same community that they serve as the grassroots health worker since 2005 when the NRHM was introduced in the Empowered Action Group (EAG) states. UP is one such Empowered Action Group (EAG) state. The current study explores the actual responses of Recently Delivered Women (RDW) on their visits during the first month of their recent delivery. From the catchment area of each of the 250 ASHAs, two RDWs were selected who had a child in the age group of 3 to 6 months during the survey. The response profiles of the RDWs on the post- delivery first month visits are dwelled upon to evolve a picture representing the entire state of UP. The relevance of the study assumes significance as detailed data on the modalities of postnatal visits are available but not exclusively for the first month period of their recent delivery. The details of the post-delivery first month period related visits are not available even in large scale surveys like National Family Health Survey 4 done in 2015-16. The current study gives an insight in to these visits with a five-point approach i.e. type of personnel doing the visit, frequency of the visits, visits done in a particular week from among those four weeks separately for the three visits separately. The current study is basically regarding the summary of this Penta approach for the post- delivery one-month period.     The first month period after each delivery deals with 70% of the time of the postnatal period & the entire neonatal period. Therefore, it does impact the Maternal Mortality Rate & Ratio (MMR) & the Neonatal Mortality Rates (NMR) in India and especially in UP through the unsafe Maternal & Neonatal practices in the first month period after delivery. The current MM Rate of UP is 20.1 & MM Ratio is 216 whereas the MM ratio is 122 in India (SRS, 2019). The Sample Registration System (SRS) report also mentions that the Life Time Risk (LTR) of a woman in pregnancy is 0.7% which is the highest in the nation (SRS, 2019). This means it is very risky to give birth in UP in comparison to other regions in the country (SRS, 2019). This risk is at the peak in the first month period after each delivery. Similarly, the current NMR in India is 23 per 1000 livebirths (UNIGME,2018). As NMR data is not available separately for states, the national level data also hold good for the states and that’s how for the state of UP as well. These mortalities are the impact indicators and such indicators can be reduced through long drawn processes that includes effective and timely visits to RDWs especially in the first month period after delivery. This would help in making their post-natal & neonatal stage safe. This is the area of post-delivery first month visit profile detailing that the current article helps in popping out in relation to the recent delivery of the respondents.   A total of four districts of Uttar Pradesh were selected purposively for the study and the data collection was conducted in the villages of the respective districts with the help of a pre-tested structured interview schedule with both close-ended and open-ended questions.  The current article deals with five close ended questions with options, two for the type of personnel & frequency while the other three are for each of the three visits in the first month after the recent delivery of respondents. In addition, in-depth interviews were also conducted amongst the RDWs and a total 500 respondents had participated in the study.   Among the districts related to this article, the results showed that ASHA was the type of personnel who did the majority of visits in all the four districts. On the other hand, 25-40% of RDWs in all the 4 districts replied that they did not receive any visit within the first month of their recent delivery. Regarding frequency, most of the RDWs in all the 4 districts received 1-2 times visits by ASHAs.   Regarding the first visit, it was found that the ASHAs of Barabanki and Gonda visited less percentage of RDWs in the first week after delivery. Similarly, the second visit revealed that about 1.2% RDWs in Banda district could not recall about the visit. Further on the second visit, the RDWs responded that most of them in 3 districts except Gonda district did receive the second postnatal visit in 7-15 days after their recent delivery. Less than half of RDWs in Barabanki district & just more than half of RDWs in Gonda district received the third visit in 15-21 days period after delivery. For the same period, the majority of RDWs in the rest two districts responded that they had been entertained through a home visit.

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

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