Seismic Retrofit of Steel Deck-Truss Bridges: Experimental Investigation

2002 ◽  
Vol 5 (3) ◽  
pp. 173-183
Author(s):  
Gokhan Pekcan ◽  
John B. Mander ◽  
Stuart S. Chen
Keyword(s):  
New York ◽  
Seismic Retrofit ◽  
Shaking Table ◽  
Scale Model ◽  
Load Path ◽  
Truss Bridges ◽  
Lateral Strength ◽  
Stiffness Characteristics ◽  
Strength And Stiffness ◽  
Steel Deck

Alternative seismic retrofit strategies for steel deck-truss bridges are investigated in this study. Various modified tension-only bracing configurations, which consist of tendon elements with or without supplemental systems are introduced within the end-sway frames. The effectiveness of the retrofit configurations is demonstrated experimentally and analytically on a one-third scale model of an existing steel end-sway frame tested on the shaking table at the State University of New York at Buffalo. It is concluded that proposed alternatives can efficiently improve the lateral strength and stiffness characteristics. Moreover, the load path within the end-sway frame is modified to bypass the existing nonductile steel bearings. A stable energy dissipation mechanism is provided by means of re-centering elastomeric spring dampers along with fuse elements, thus reducing the overall seismic demand on the structural systems.

Experimental Study on Non-Perpendicular Frame Structure of Tall Building

2008 ◽  
Vol 400-402 ◽  
pp. 593-598
Author(s):  
Wei Xing Shi ◽  
Cheng Qing Liu ◽  
Xi Lin Lu ◽  
Song Zhang ◽  
Ying Zhou
Keyword(s):  
Similarity Theory ◽  
Structural Type ◽  
Shaking Table ◽  
Frame Structure ◽  
Scale Model ◽  
Prototype Structure ◽  
Table Model ◽  
Practical Engineering ◽  
Whiplash Effect ◽  
Shaking Table Model Test

A shaking table model test is conducted for Guangzhou West Tower to study its seismic behavior in State Key Laboratory for Disaster Reduction in Civil Engineering at Tongji University. Guangzhou West Tower adopts a new structure system and the significant characteristic of this system is the non-perpendicular frame arranged around the building, acting both as columns and bracings. Based on the similarity theory and member equivalent principle，a 1/80 scale model of this building is made of polymethyl methacrylate(PMMA). The model’s dynamic characteristics, earthquake-resistant behavior, responses of acceleration and deformation under different wave peak values are investigated, then the seismic responses of the prototype structure are deduced and analyzed. The whiplash effect of the prototype structure is studied, and the weak position of the structure is found out. The experiment results demonstrate that it is feasible to apply this structural type to practical engineering. Finally, some suggestions for the engineering design of the prototype structure are put forward.

Earthquake induced floor accelerations on a high-rise building: Scale model tests on a shaking table

2021 ◽  
Author(s):  
Fabio Rizzo ◽  
Alessandro Pagliaroli ◽  
Giuseppe Maddaloni ◽  
Antonio Occhiuzzi ◽  
Andrea Prota
Keyword(s):  
Soil Structure ◽  
Shaking Table ◽  
Soil Structure Interaction ◽  
Scale Model ◽  
Structural Elements ◽  
Shaking Table Tests ◽  
Building Model ◽  
High Rise ◽  
High Rise Building ◽  
Story Building

<p>The paper discusses results of shaking table tests on an in-scale high-rise building model. The purpose was to calibrate a dynamic numerical model for multi-hazard analyses to investigate the effects of floor acceleration. Accelerations, because of vibration of non-structural elements, affect both the comfort and safety of people. The research investigates the acceleration effects of both seismic and wind forces on an aeroelastic in-scale model of a multi-story building. The paper discusses the first phase of experiments and gives results of floor accelerations induced by several different base seismic impulses. Structural analyses were first performed on the full-scale prototype to take soil-structure interaction into account. Subsequently the scale model was designed through aeroelastic scale laws. Shaking table experiments were then carried out under different base accelerations. The response of the model and, in particular, amplification of effects from base to top are discussed.</p>

scholarly journals Early detection of superspreaders by mass group pool testing can mitigate COVID-19 pandemic

2020 ◽  
Author(s):  
Maxim B Gongalsky
Keyword(s):  
New York ◽  
Early Detection ◽  
Group Testing ◽  
Scale Model ◽  
Rt Pcr ◽  
Infected People ◽  
Group Matrix ◽  
New Strategy ◽  
Mass Group ◽  
Log Normal

Background Most of epidemiological models applied for COVID-19 do not consider heterogeneity in infectiousness and impact of superspreaders, despite the broad viral loading distributions amongst COVID-19 positive people (1-1 000 000 per mL). Also, mass group testing is not used regardless to existing shortage of tests. I propose new strategy for early detection of superspreaders with reasonable number of RT-PCR tests, which can dramatically mitigate development COVID-19 pandemic and even turn it endemic. Methods I used stochastic social-epidemiological SEIAR model, where S-suspected, E-exposed, I-infectious, A-admitted (confirmed COVID-19 positive, who are admitted to hospital or completely isolated), R-recovered. The model was applied to real COVID-19 dynamics in London, Moscow and New York City. Findings Viral loading data measured by RT-PCR were fitted by broad log-normal distribution, which governed high importance of superspreaders. The proposed full scale model of a metropolis shows that top 10% spreaders (100+ higher viral loading than median infector) transmit 45% of new cases. Rapid isolation of superspreaders leads to 4-8 fold mitigation of pandemic depending on applied quarantine strength and amount of currently infected people. High viral loading allows efficient group matrix pool testing of population focused on detection of the superspreaders requiring remarkably small amount of tests. Interpretation The model and new testing strategy may prevent thousand or millions COVID-19 deaths requiring just about 5000 daily RT-PCR test for big 12 million city such as Moscow. Though applied to COVID-19 pandemic the results are universal and can be used for other infectious heterogenous epidemics. Funding No funding

scholarly journals Comparative Evaluation of Concentric Bracing Systems for Lateral Loads on Medium Rise Steel Building Structures

2020 ◽  
pp. 124-130
Author(s):  
Sisaynew Tesfaw Admassu
Keyword(s):  
Lateral Displacement ◽  
Level Structure ◽  
Lateral Load ◽  
Frame Structure ◽  
Lateral Stiffness ◽  
Building Structures ◽  
Steel Buildings ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Bracing System

To resistance, the lateral load from wind or an earthquake is that the reason for the evolution of varied structural systems. Because, when a medium or any multi-level structure is exposed to horizontal or torsional deflections under the action of seismic burdens. Lateral stiffness is a major consideration in the design of the buildings. In addition to this, many existing steel buildings and reinforced concrete buildings for which the weak lateral stiffness is the main problem; should be retrofitted to conquer the insufficiencies to resist the lateral loading. Lateral load resisting systems are structural elements providing basic lateral strength and stiffness, without which the structure would be laterally unstable. The unstable nature of the structure is solved by the fitting arrangement of bracings systems. A bracing system is that forms an integral part of the frame. Thus, such a structure has to be analyzed before arriving at the best type or effective arrangement of bracing. Bracing is a highly effective strategy of resisting lateral forces in a frame structure. In this document, a ten-story building with incorporated bracing systems is analysed using ETABS 2016 analysis software as per Eurocode and Ethiopian Building Code Standards (EBCS). Then, the lateral displacement is evaluated under each of the bracing types.

Seismic Isolation Retrofitting of Typical Multi-Span Steel Girder Bridges in New York State

2020 ◽  
Vol 2674 (8) ◽  
pp. 785-798 ◽  
Author(s):  
Dongming Feng ◽  
Fangyin Zhang
Keyword(s):  
New York ◽  
Seismic Isolation ◽  
Ground Motions ◽  
Limit State ◽  
New York State ◽  
Time History ◽  
Seismic Retrofit ◽  
Structural Members ◽  
York State ◽  
Simply Supported

Many of the existing multi-span simply supported bridges in New York State, U.S., are susceptible to earthquake damage and need to be retrofitted to reduce their seismic risk. In this study, seismic retrofit of a five-span simply supported bridge with typical high-type fixed and expansion steel rocker bearings is conducted. A refined three-dimensional (3D) finite element model of the bridge is developed in ANSYS by considering foundation impedances. Multi-support time history analyses have been implemented in the seismic retrofit design for two levels of ground motions: 1,000- and 2,500-year return period earthquakes. The site-specific ground motions with consideration of the spatial variation are generated based on the geotechnical information. Seismic retrofit by replacing existing steel bearings with lead-rubber bearing (LRB) isolators has been adopted. The parameters of the isolators are determined by considering factors such as the seismic performance and translational resistance during normal service. The vulnerability of structural members and seismic retrofit effectiveness are quantified by the demand-to-capacity (D/C) ratio for the combined demands at the extreme limit state. The analyses show that after seismic isolation retrofit the pervasive vulnerabilities in pier columns and cap beams are eliminated. Comparing with strengthening the vunerable structural members, seismic isolation is proved a cost-effective retrofit solution. The overall seismic isolation design and analysis procedures presented in this study can help guide future seismic retrofit of similar types of bridges.

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