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1
Paeglite, Ilze, Ainars Paeglitis, and Juris Smirnovs. "DYNAMIC AMPLIFICATION FACTOR FOR BRIDGES WITH SPAN LENGTH FROM 10 TO 35 METERS." Engineering Structures and Technologies 6, no. 4 (2015): 151–58. http://dx.doi.org/10.3846/2029882x.2014.996254.
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Heavy traffic on the bridge cause not only static effects, but also dynamic effects. These effects can be indicated by different dynamic parameters like – natural frequency, bridge logarithmical decrement, bridge acceleration and dynamic amplification factor (DAF). Dynamic amplification factor is the most widely used parameter, because it shows amplification of the static effects on the bridge structure. Results show that for bridges road surface condition is a very important factor. If road surface contains ice bumps or potholes then heavy traffic driving with low speed can decrease load carrying capacity of a bridge.
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Savard, Marc, Marc-André Careau, and Alain Drouin. "Experimental study on the dynamic effects caused by vehicular traffic on a ferry boarding ramp." Canadian Journal of Civil Engineering 29, no. 1 (2002): 27–36. http://dx.doi.org/10.1139/l01-069.
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This article presents some of the results obtained during a load test conducted on a ferry boarding ramp operated by the Société des traversiers du Québec. The measurements highlight the sensitivity of these structures to the dynamic effects caused by two heavy vehicles. Since the dynamic behaviour of highway bridges is affected by parameters different from those that affect ferry boarding ramps, the article presents a reflection on the dynamic load allowance suitable for the evaluation or design of this latter type of structure.Key words: boarding ramp, bridge, dynamic amplification factor, design codes.
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Ruiz, Manuel, Luis Ramírez, Fermín Navarrina, Mario Aymerich, and David López-Navarrete. "A Mathematical Model to Evaluate the Impact of the Maintenance Strategy on the Service Life of Flexible Pavements." Mathematical Problems in Engineering 2019 (May 30, 2019): 1–10. http://dx.doi.org/10.1155/2019/9480675.
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The structural failure of a flexible pavement occurs when the accumulated fatigue damage produced by all the vehicles that have passed over each section exceeds a certain threshold. For this reason, the service life of pavement can be predicted in terms of the damage caused by the passage of a single standard axle and the expected evolution of traffic intensity (measured in equivalent standard axles) over time. In turn, the damage caused by the passage of an axle depends on the vertical load exerted by the wheels on the pavement surface, as given by the technical standard in application, and the depths and mechanical characteristics of the layers that compose the pavement section. In all standards currently in application, the unevenness of the road surface is disregarded. Therefore, no dynamic effects are taken into consideration and the vertical load is simply given in terms of the static weight carried by the standard axle. However, it is obvious that the road profile deteriorates over time, and it has been shown that the increase in the pavement roughness, when considered, gives rise to important dynamic effects that may lead to a dramatic fall in the expected structural service life. In this paper, we present a mathematical formulation for the fatigue analysis of flexible pavements that includes the effects of dynamic axle loading. A pavement deterioration model simulates the sustained growth of the IRI (International Roughness Index) over time. Time is discretized in successive time steps. For each time step, a road surface generation model provides a profile that renders the adequate value of the IRI. A QHV (Quarter Heavy Vehicle) model provides the dynamic amplification function for the loads exerted on the road surface along a virtual ride. This function is conveniently averaged, what gives the value of the so-called effective dynamic load amplification factor (DLA); this is the ratio between the effective dynamic loading and the static loading at each time step. Finally, the damage caused by the passage of the standard axle can be evaluated in terms of the dynamic loading. The product of this damage times the number of equivalent standard axles gives the total fatigue damage produced in the time step. The accumulated fatigue damage at each moment is easily computed by just adding up the damage produced in all the previous time steps. The formulation has been implemented in the software DMSA (Dynamic & Maintenance Simulation App). This tool has been specifically developed for the evaluation of projects in applications for financing submitted to the European Investment Bank (EIB). DMSA allows for quantifying the expected structural service life of the pavement taking into account both the rise of the dynamic axle loads exerted by the traffic as the road profile deteriorates over time and the different preventive maintenance strategies to be taken into consideration.
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JUNGES, P., R. C. A. PINTO, and L. F. FADEL MIGUEL. "B-WIM systems application on reinforced concrete bridge structural assessment and highway traffic characterization." Revista IBRACON de Estruturas e Materiais 10, no. 6 (2017): 1338–65. http://dx.doi.org/10.1590/s1983-41952017000600010.
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Abstract The vehicles that travel on Brazilian highways have changed a lot in the last decades, with an increase in the traffic load and in the amount of trucks. This fact is not exclusive to our country, so much that in order to assess the structural safety of bridges, there was a great development in bridge weigh-in-motion systems (B-WIM) the last decade, especially in developed countries. Moses, in 1979, was the first one to introduce the B-WIM concept. This work presents the results of a B-WIM system applied on a bridge over the Lambari river, located at BR 153 in Uruaçu (Goiás). The weigh-in-motion technique used is based on Moses' Algorithm and uses influence lines obtained direct from traffic. Traffic characterization of that particular highway, as well as the effects introduced in the bridge structure and the experimental dynamic amplification factor are also discussed. At the end it is concluded that the system used is capable of detecting, with good precision, the axle spacing and the gross vehicle weight shows errors inferior to 3% when compared with the gross weight acquired with static scale.
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Yang, Jian Rong, Yu Bai, Xiao Dong Yang, and Yun Feng. "Dynamic Amplification Factor Measuring of T-Girder Bridges." Key Engineering Materials 540 (January 2013): 29–36. http://dx.doi.org/10.4028/www.scientific.net/kem.540.29.
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Field measurement was conducted on the evaluation of dynamic amplification factors (DAF) for four existing T-girder bridges. Both ambient vibration testing and vehicle impact testing were carried out on the bridges. Ambient vibration testing is relatively easier to conduct and can provide detailed vibrating information of the structure. However vehicle impact testing is indispensable to obtain the impact factor of the traffic load. The measured vibration frequencies matched well to those of calculated values. This means that the finite element model may enable good predictions of the actual behavior of the bridge. The measured DAF for these bridges located in the interval [1.05, 1.22].
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Caprani, Colin C. "Lifetime Highway Bridge Traffic Load Effect from a Combination of Traffic States Allowing for Dynamic Amplification." Journal of Bridge Engineering 18, no. 9 (2013): 901–9. http://dx.doi.org/10.1061/(asce)be.1943-5592.0000427.
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Ma, Haiying, Zhen Cao, Xuefei Shi, and Junyong Zhou. "Dynamic Amplification Factor of Shear Force on Bridge Columns under Impact Load." Shock and Vibration 2019 (March 10, 2019): 1–14. http://dx.doi.org/10.1155/2019/9483246.
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Shear failure is a common mode for bridge column collapse during a vehicle-column collision. In current design codes, an equivalent static load value is usually employed to specify the shear capacity of bridge columns subject to vehicle collisions. But how to consider the dynamic effect on bridge columns induced by impact load needs further research. The dynamic amplification factor (DAF) is generally used in the analysis and design to include the dynamic effect, which is usually determined using the equivalent single degree of freedom (SDOF) method. However, SDOF method neglects the effect of the higher-order modes, leading to big difference between the calculated results and the real induced forces. Therefore, a novel method to obtain dynamic response under concentrated impact load including the effect of higher-order modes is proposed in the paper, which is based on the modified Timoshenko beam theory (MTB) and the classical Timoshenko beam theory (CTB). Finite element models are conducted to validate the proposed method. The result comparisons show that the results from the proposed method have more accuracy compared with the results from the CTB theory. Additionally, the proposed method is employed to calculate the maximum DAF of shear forces for bridge columns under impact load. Parametric studies are conducted to investigate the effect on the DAF of shear forces including slenderness ratio, boundary condition, and shape and position of impact load. Finally, a simplified formula for calculating the maximum DAF of shear force is proposed for bridge column design.
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Rattigan, Paraic H., Arturo González, and Eugene J. OBrien. "Influence of pre-existing vibrations on the dynamic response of medium span bridges." Canadian Journal of Civil Engineering 36, no. 1 (2009): 73–84. http://dx.doi.org/10.1139/l08-104.
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Critical static bridge loading scenarios are often expressed in terms of the number of vehicles that are present on the bridge at the time of occurrence of maximum lifetime load effect. For example, 1-truck, 2-truck, 3-truck, or 4-truck events usually govern the critical static loading cases in short and medium span bridges. However, the dynamic increment of load effect associated with these maximum static events may be assessed inaccurately if it is calculated in isolation of the rest of the traffic flow. In other words, a heavy vehicle preceding a critical loading case causes the bridge initial conditions of displacement and acceleration to be nonzero when the critical combination of traffic arrives on the bridge. Failure to consider these pre-existing vibrations will result in inaccurate estimation of dynamic amplification. This paper explores these dynamic effects and, using statistical analyses, outlines the relative importance of pre-existing vibrations in the assessment of total traffic load effects.
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Li, Xin, Li Liang, and Fu Chun Wang. "Numerical Simulation of Vibration of Highway Cable-Stayed Bridge with Steel Arch Tower due to Moving Vehicle Loads." Advanced Materials Research 243-249 (May 2011): 1614–20. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1614.
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Recently, with the development of highway traffic cause and long-span bridges, the vibration performances of highway bridges due to moving vehicle loads have attracted more and more attention. The vibration of a cable-stayed bridge with steel arch tower subjected to vehicle loads was studied in this paper. Firstly, the dynamic model of vehicle and finite element model of bridge were built and the dynamic differential equations of vehicle model and vehicle-bridge coupled system were derived. Then road roughness was simulated using superposition method of trigonometric series. Finally, the bridge responses caused by vehicle loads were calculated numerically. Furthermore, the effects of road roughness, vehicle velocity and bridge damping on bridge responses and their dynamic amplification factors were studied. The results and conclusions of present study are expected to be useful for the future revision of bridge design codes and maintenance and management of bridge.
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Bui, Tuyen Van. "Effect of temperature and porosities on dynamic response of functionally graded beams carrying a moving load." Science and Technology Development Journal 20, K2 (2017): 24–33. http://dx.doi.org/10.32508/stdj.v20ik2.445.
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The effect of temperature and porosities on the dynamic response of functionally graded beams carrying a moving load is investigated. Uniform and nonlinear temperature distributions in the beam thickness are considered. The material properties are assumed to be temperature dependent and they are graded in the thickness direction by a power-law distribution. A modified rule of mixture, taking the porosities into consideration, is adopted to evaluate the effective material properties. Based on Euler-Bernoulli beam theory, equations of motion are derived and they are solved by a finite element formulation in combination with the Newmark method. Numerical results show that the dynamic amplification factor increases by the increase of the temperature rise and the porosity volume fraction. The increase of the dynamic amplification factor by the temperature rise is more significant by the uniform temperature rise and for the beam associated with a higher grading index.
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Han, Fei, Dan-hui Dan, and Hu Wang. "A Study on Dynamic Amplification Factor and Structure Parameter of Bridge Deck Pavement Based on Bridge Deck Pavement Roughness." Advances in Civil Engineering 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/9810461.
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In order to study the coupled influence of deck pavement roughness and velocity on dynamic amplification factor, a 2-DOF 1/4 vehicle model is employed to establish the vehicle-bridge-coupled vibration system. The random dynamic load of running vehicle simulated by software MATLAB is applied on bridge deck pavement (BDP) through ANSYS software. Besides, the influence of BDP parameters on control stress under static load and random vibration load is analyzed. The results show that if the surface of BDP is smooth, the dynamic magnification coefficient would first increase and then decrease with increasing of vehicle velocity and reach its maximum value when v = 20 m/s; if the surface of BDP is rough, the maximal and minimum values of the dynamic amplification coefficient (DAC) occur, respectively, when the velocity reaches 10 m/s and 15 m/s. For a composite bridge deck with the cushion layer, the thickness of asphalt pavement should be not too thick or thin and better to be controlled for about 10 cm; with the increasing of cushion layer thickness, the control stress of deck pavement is all decreased and show similar change regularity under effect of different loads. In view of self-weight of structure, the thickness of the cushion layer is recommended to be controlled for about 4 cm.
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Nowak, Andrzej S., Junsik Eom, and Ahmet Sanli. "Control of Live Load on Bridges." Transportation Research Record: Journal of the Transportation Research Board 1696, no. 1 (2000): 136–43. http://dx.doi.org/10.3141/1696-55.
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Application of field testing for an efficient evaluation and control of live-load effects on bridges is described. A system is considered that involves monitoring of various parameters, including vehicle weight, dynamic load component, and load effects (moment, shear force, stress, strain) in bridge components, and verification of the minimum load-carrying capacity of the bridge. Therefore, an important part of the study is development of a procedure for measuring live-load spectra on bridges. Truck weight, including gross vehicle weight, axle loads, and spacing, is measured to determine the statistical parameters of the actual live load. Strain and stress are measured in various components of girder bridges to determine component-specific load. Minimum load-carrying capacity is verified by proof load tests. It has been confirmed that live-load effects are strongly site specific and component specific. The measured strains were relatively low and considerably lower than predicted by analysis. Dynamic load factor decreases with increasing static load effect. For fully loaded trucks, it is lower than the code-specified value. Girder distribution factors observed in the tests are also lower than the values specified by the design code. The proof load test results indicated that the structural response is linear with the absolute value of measured strain considerably lower than expected. Field tests confirmed that the tested bridges are adequate to carry normal truck traffic.
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Zhou, Jia Mei, Qi Yan, and Guo Wang Meng. "Seismic Dynamic Model Tests on Tunnel Lining Passing through the Fault." Applied Mechanics and Materials 368-370 (August 2013): 1732–37. http://dx.doi.org/10.4028/www.scientific.net/amm.368-370.1732.
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The seismic behaviors of tunnel lining passing through the fault are studied by means of large-scale shaking table tests under the load of Wolong-seismic wave. The model tunnel is installed into a model box with a length of 3.65 m, width of 1.5 m and height of 1.8 m. The sizes of model and prototype tunnel are designed by using the similar principles with a scale factor of 1:30. As the result shows, under the seismic force load, the tunnel lining has a delay of responding the seismic force when it crosses the faults geological belt. The time is 0.085seconds. Model box amplified table acceleration, the farther the distance from shaking table is, the more obvious amplification is. The seismic force load is horizontal, but the resistance applied by the faults geological belt is weak, resulting relative motion, collision, extrusion etc. so, the tunnel lining appears cracks. It is in accord with investigation conclusions of Wenchuan earthquake. Article also aims at some problems in the experiment such as: boundary effect, model box stiffness etc, and gives some suggestions.
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Liu, Han Qing, and Gui Xian Wu. "Traffic Load of Pavement under the Action of the Finite Element Analysis Viscoelastic Fracture." Advanced Materials Research 446-449 (January 2012): 3311–17. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.3311.
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In the design of the asphalt pavement or asphalt overlay, consider about the viscoelastic fracture mechanics behavior of asphalt mixture is significant in researching the asphalt pavement craze or the extending behavior of reflective crack. This paper employs nonlinear finite element software ABAQUS to analysis about the viscoelastic of asphalt mixture in the basis of the vicoelastic breaking theory, analyze the Traffic dynamic loading different speeds, different grassroots modulus to contain crack pavement structure system of the displacement field and stress field of influence.The calculation results show that the curve of the stress intensity factor in the crack tip moves as the increase of the speed, but the maximum is virtually unchanged; and it is proportional to the grassroots modulus variations, that is the stress intensity factor increases as the increase of grassroots modulus. With the effect of partial load, the stress intensity factor is formed by KⅠ、KⅡ. It is mainly assumed by KⅡ when grassroots modulus is low, and as the grassroots modulus increases, the KⅠ is increases, But KⅡ changes little.
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Meinecke, Eberhard. "Effect of Carbon-Black Loading and Crosslink Density on the Heat Build-Up in Elastomers." Rubber Chemistry and Technology 64, no. 2 (1991): 269–84. http://dx.doi.org/10.5254/1.3538558.
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Abstract It has been shown that it is possible to predict the viscoelastic response of elastomers and elastomeric engineering components under both load- and position-control conditions if one assumes: a) that the modulus of the materials increases with the strain amplification factor as given by the Guth and Gold equation, b) that the occluded rubber is taken into account when using this equation, and c) that the energy loss per cycle and unit volume of material is increasing with the square of the strain-amplification factor. These calculations were applied to an assembly where one unfilled section is in series with a filled one. The overall filler loading was kept constant, and it was found that the equations derived show completely different heat-generation rates for load- and position-control conditions. While the losses are the same in both sections and equal to that of the assembly as a whole under position-control conditions, they are quite different under load-control conditions. They increase with both filler loading and values of α and abnormally high local overheating in the unfilled section occurs. These considerations indicate that a uniform mixing quality is important for compounds which will be used in dynamically deformed engineering components. Under position-control conditions, poor filler dispersion will give rise to a decrease in the dynamic modulus and the energy loss per cycle, i.e., variations in the quality of the mix will cause variability of the dynamic properties. Under load-control conditions, the situation is even worse, since the energy dissipation increases with poor mixing, and local overheating of the sections containing less than the average amount of carbon black takes place. The model is obviously too oversimplified for qualitative predictions. But it still gives good qualitative indications regarding the heat-generation rate in structures made from two elastomers having different filler loadings or for imperfectly mixed compounds.
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Ferraioli, Massimiliano, Alberto Maria Avossa, and Alberto Mandara. "Assessment of Progressive Collapse Capacity of Earthquake-Resistant Steel Moment Frames Using Pushdown Analysis." Open Construction and Building Technology Journal 8, no. 1 (2014): 324–36. http://dx.doi.org/10.2174/1874836801408010324.
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The study investigates the progressive collapse resisting capacity of earthquake-resistant steel moment-resisting frames subjected to column failure. The aim is to investigate whether these structures are able to resist progressive collapse after column removal, that may represent a situation where an extreme event may cause a critical column to suddenly lose its load bearing capacity. Since the response to this abnormal loading condition is most likely to be dynamic and nonlinear, both nonlinear static and nonlinear dynamic analyses are carried out. The vertical pushover analysis (also called pushdown) is applied with two different procedures. The first one is the traditional procedure generally accepted in current guidelines that increases the load incrementally to a specified level after column has been removed. The second procedure tries to reproduce the timing of progressive collapse and, for this reason, gravity loads are applied to the undamaged structure before column removal. The load-displacement relationships obtained from pushdown analyses are compared with the results of incremental nonlinear dynamic analyses. The effect of various design variables, such as number of stories, number of bays, level of seismic design load, is investigated. The results are eventually used to evaluate the dynamic amplification factor to be applied in pushdown analysis for a more accurate estimation of the collapse resistance.
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Žnidarič, Aleš, and Jan Kalin. "Using bridge weigh-in-motion systems to monitor single-span bridge influence lines." Journal of Civil Structural Health Monitoring 10, no. 5 (2020): 743–56. http://dx.doi.org/10.1007/s13349-020-00407-2.
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Abstract Bridge weigh-in-motion systems use instrumented bridges or culverts to weigh vehicles as they pass over the structures. They also provide data to allow the calculation of several bridge performance indicators. The article starts with the basics of a bridge weigh-in-motion system and briefly describes two key bridge performance indicators, girder distribution factor and dynamic amplification factor, which are also derived from B-WIM measurements. The central part of the article focuses on monitoring of influence lines, the third key parameter that characterises the bridge performance under traffic loads. First, the method of calculating the bending moment influence lines from random heavy traffic is described. A coefficient of rotational stiffness is introduced, which defines the shape of influence lines around the supports as a linear combination of the ideal simply supported and fixed supported influence lines, to allow quantifying the influence line changes. Then the long-term monitoring of influence lines is investigated on four different single-span test bridges. The initial focus is given on the examination of the effect of temperature on the shape of influence lines. Finally, two sets of influence lines are compared on one test bridge, one from before and the other from after replacing the expansion joints and bearings. The work done so far confirms that calculating of influence lines from random vehicles with a B-WIM system is entirely feasible and that differences in their shape can be detected on single-span bridges. What remains to be investigated is the comparison of these differences to the actual damages and under which circumstances the proposed procedure can compete with or better the routine bridge inspection and the conventional monitoring techniques.
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Ouchenane, Meriem, Rachid Lassoued, and Karima Ouchenane. "Vibration of Bridges under the Passage of Vehicles Simulated as Moving Loads." Advanced Materials Research 324 (August 2011): 396–99. http://dx.doi.org/10.4028/www.scientific.net/amr.324.396.
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The dynamic behavior of bridges under the effect of moving loads simulating the vehicle moving along the bridge structure idealized by an Euler beam is analyzed. We will present the dynamic behavior of beams under the stress of moving loads (or masses) by the analytical and semi-analytical approaches. When the mass of the bridge structure is comparable to that of the vehicle, the mobile source requesting the bridge is simulated by a mass. In most practical cases, the mobile force used is due to the effects of the gravitational moving masses: . When the moving mass is small compared to the beam mass, the obtained solution under the effect of moving force is approximately correct for the solution obtained with the moving mass. Otherwise, the problem of the moving mass is imperative. To do this, we wrote a program in Matlab language which reflects the dynamic behavior of beams under the effect of moving charges, which gives the following results "The frequencies and modes of vibration, the dynamics deflection of the beam requested by moving force, the dynamic response (DAF: dynamic amplification factor) of the beam requested by a moving force, over the whole length of the beam, for all times and for different speeds. The numerical example that we look to see for study the dynamic behavior of this type of bridge under moving loads is that of a thin beam unamortised on simple support and length of 50m, under the solicitation of moving force and mass at a constant speed and varies from 0 to 100 m / s (M. A. Foda, 1997), depending on the relationship between the vehicle mass and the mass of the bridge that will allow us to see the contribution of the choice of modelling type on the total response and then the vibration of bridge, also we will study the effect of type of simulation of the load by moving force or mass on the dynamic amplification factor and comparing our results with those from the literature.
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Liu, Yanhui, Khalil Al-Bukhaiti, Hussein Abas, and Zhao Shichun. "Effect of CFRP Shear Strengthening on the Flexural Performance of the RC Specimen under Unequal Impact Loading." Advances in Materials Science and Engineering 2020 (November 18, 2020): 1–18. http://dx.doi.org/10.1155/2020/5403835.
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Strengthening with externally bonded CFRP reinforcement is widely used in structural reinforcement and attractive to stakeholders and engineers because of ease and speed of construction, corrosion resistance, lightweight, high strength, and versatility stiffness which can be oriented according to the need. Numerous research studies were carried out to explore RC beams’ flexural and shear performance when subjected to dynamic impact loading. The results were auspicious in using such a technique of strengthening. Regular square section reinforced concrete frame members strengthened by CFRP material is taken as the research object. However, little attention to the impact behavior of CFRP-shear-strengthened square reinforced concrete (RC) specimens has been paid. The dynamic response of CFRP to reinforced concrete members under unequal cross-impact is discussed. This paper investigates the effectiveness of CFRP strengthening on the square RC specimen in preventing shear failure and evaluation of the flexural performance of the strengthened specimen under the impact load. The drop hammer impact test is firstly conducted on RC specimens with and without CFRP strengthening. The results show that using CFRP to strengthen the RC specimen in shear is very effective at preventing shear failure and leading the specimen’s response to flexural domination. This result is also the motivation for developing a numerical model supported by experimental tests to study the flexural performance of strengthened RC specimens. It is found that the strengthened specimen is prone to exhibit pure bending deformation under the impact load in terms of dynamic amplification factor (DAF) for section moment. Then, an extensive parameter study is carried out to evaluate further the influence of impact velocity, reinforcement ratio, and concrete strength on the flexural performance of the strengthened specimen and CFRP layers. Such a holistic study may provide preliminary research regarding the use of CFRP to strengthen RC specimens in shear under impact loads and will enhance the current state of knowledge in this area; also, the optimal value of the CFRP reinforcement layer was proposed.
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Sanni, R. A., D. Surry, and A. G. Davenport. "Wind loading on intermediate height buildings." Canadian Journal of Civil Engineering 19, no. 1 (1992): 148–63. http://dx.doi.org/10.1139/l92-015.
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The current gust factor approach in the detailed method of the National Building Code of Canada (NBCC) for the estimation of wind loads on buildings was developed from research work that was largely directed towards very tall and flexible buildings for which resonant responses are very significant; however, the dynamic responses of the majority of intermediate height buildings are dominated by quasi-steady gust loading with little resonant response. This study has been carried out to assess the applicability of the detailed approach of the NBCC to that class of fairly common intermediate height buildings, of which apartment buildings are good examples. For the purposes of this study, these buildings have been defined as buildings whose heights are between 20 and 120 m and whose ratio of height to minimum width is not more than 4. The responses estimated from the detailed approach of the NBCC have been compared with those from wind tunnel tests with a view to verifying and simplifying its application to such intermediate height buildings.Since intermediate height buildings are often arranged in groups, an experimental study of the interference effects between adjacent buildings was also undertaken to assess the effect of an upwind building on the wind-induced overall moments on a downwind building of a similar height. The influence of this interference effect on the member stresses or forces was investigated using the concept of joint action factors.General agreement between the test and the code-estimated responses was obtained in the comparisons. The small resonant responses observed provided a basis for deriving a simplified method for estimating the gust factor in the detailed method without the requirement of knowing the structure's dynamic properties.Significant interference effects were found, particularly for the across-wind and torsional moments on buildings in an open exposure; however, the amplification of the overall wind-induced moments does not necessarily translate into a similar amplification of member forces or stresses. For the buildings studied, the results have shown that for the majority of practical situations, interference effects are not likely to result in amplification of member stresses or forces. A set of additional factors of safety have been proposed, based on the limited experimental data set, to cover load amplification by interference effects for those members that are very sensitive to overall wind-induced torsional moments. Key words: codes, wind loads, wind engineering, intermediate height buildings, interference effects.
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Hao, Yane, Xingwen Liang, and Yongqiang Lan. "Numerical Simulation and Dynamic Analysis of Single-Hole Cliff-Side Loess Cave Dwelling under Seismic Actions." Geofluids 2021 (September 15, 2021): 1–13. http://dx.doi.org/10.1155/2021/6890445.
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Loess cave dwellings are the most typical style of regional architecture in northwest China; now, there are still tens of millions of people living in them. The northwest is an earthquake-prone area, and cave dwellings have suffered a lot of damage in previous moderate and strong earthquakes, so their earthquake resistance has attracted people’s attention. At present, the seismic analysis of aboveground building structures is relatively mature, while the seismic analysis of loess cave dwellings is less researched. To study the seismic response of loess cave dwellings, a single-hole cliff-side loess cave dwelling located in Yangjialing revolution former sites of Yan’an City of northwest China was investigated and surveyed; the three-dimensional numerical model was established by MIDAS/GTS NX. Combining the historic earthquake damage investigation, dynamic time-history analysis of the single-hole loess cliff-side cave dwelling subject to four horizontal earthquake actions was conducted to determine the weak positions, failure characteristics, and the corresponding displacement and stress of the loess cave dwelling under earthquake load. The results show that the loess has an amplification effect on the seismic waves, the arch vault is a key factor to the stability of the loess cave dwellings, the cliff-side loess cave dwellings in an 8-degree area cannot be used to continue living, and the entrance to loess cave dwellings is the most dangerous place when the earthquake happens.
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Zhou, Xiaojie, Qinghua Liang, Zhongxian Liu, and Ying He. "IBIEM Analysis of Dynamic Response of a Shallowly Buried Lined Tunnel Based on Viscous-Slip Interface Model." Advances in Civil Engineering 2019 (March 6, 2019): 1–14. http://dx.doi.org/10.1155/2019/1025483.
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A viscous-slip interface model is proposed to simulate the contact state between a tunnel lining structure and the surrounding rock. The boundary integral equation method is adopted to solve the scattering of the plane SV wave by a tunnel lining in an elastic half-space. We place special emphasis on the dynamic stress concentration of the lining and the amplification effect on the surface displacement near the tunnel. Scattered waves in the lining and half-space are constructed using the fictitious wave sources close to the lining surfaces based on Green’s functions of cylindrical expansion and the shear wave source. The magnitudes of the fictitious wave sources are determined by viscous-slip boundary conditions, and then the total response is obtained by superposition of the free and scattered fields. The slip stiffness and viscosity coefficients at the lining-surrounding rock interface have a significant influence on the dynamic stress distribution and the nearby surface displacement response in the tunnel lining. Their influence is controlled by the incident wave frequency and angle. The hoop stress increases gradually in the inner wall of the lining as sliding stiffness increases under a low-frequency incident wave. In the high-frequency resonance frequency band, where incident wave frequency is consistent with the natural frequency of the soil column above the tunnel, the dynamic stress concentration effect is more significant when it is smaller. The dynamic stress concentration factor inside the lining decreases gradually as the viscosity coefficient increases. The spatial distribution and the displacement amplitudes of surface displacement near the tunnel change as incident wave frequency and angle increase. The effective dynamic analysis of the underground structure under an actual strong dynamic load should consider the slip effect at the lining-surrounding rock interface.
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Liu, Yang, Qinyong Wang, and Naiwei Lu. "Probabilistic evaluation of maximum dynamic traffic load effects on cable-supported bridges under actual heavy traffic loads." Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, July 16, 2020, 1748006X2093849. http://dx.doi.org/10.1177/1748006x20938491.
Full textAbstract:
The traffic load has grown significantly in recent years, which might be a threat for the service safety of existing bridges. Thus, it is an urgent task to assess the actual traffic load effects on bridges, considering actual heavy traffic load instead of design traffic load. This study presents a framework for extrapolating maximum dynamic traffic load effects on large bridges using site-specific traffic monitoring data. The framework involves vehicle–bridge interaction analysis and probabilistic modelling of extreme values. The weigh-in-motion measurements of a busy highway in China were collected for stochastic traffic load modelling. Case studies of two long-span cable-supported bridge based on the weigh-in-motion measurements were conducted to demonstrate the effectiveness of the proposed framework. It is demonstrated that Rice’s level-crossing approach can capture both dynamic and probabilistic characteristics of the traffic load effects. The root-mean-square displacement of the cable-stayed bridge follows a C-type distribution, and the one for the suspension bridge follows an M-type distribution, which is associated with the first-order mode shapes of the two types of bridges. The amplification factors for the cable-stayed bridge and the suspension bridge are 5.9% and 3.6%, respectively. The numerical analysis indicates that the dynamic effect for extrapolation is weaker with the increase in bridge span length, but the effect of traffic volume growth will be more significant.
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Wu, Xue-Qian, Bo Zhong, Yang Lv, Zhong-Xian Li, and Nawawi Chouw. "Experimental Study on Dynamic Amplification Factor of Simple-Supported Reinforced Concrete Beams Under Impact Loading Generated by an Impulse Hammer." International Journal of Structural Stability and Dynamics, December 7, 2020, 2150036. http://dx.doi.org/10.1142/s021945542150036x.
Full textAbstract:
The empirical formulas of dynamic amplification factor (DAF) specified in current bridge codes only consider the span or fundamental frequency of reinforced concrete (RC) girders in highway. Although investigations have been carried out on different bridges with considering the road roughness, vehicle–bridge interactions and travelling velocity, but most of them have been done numerically. In this study, experimental study of DAF was carried out on three simple-supported RC beams with different fundamental frequencies and different damage stages, i.e. without damage, cracked and yielded. Impulse hammer with four hammer heads of different hardness, i.e. black, red, green and brown, were used to generate impact forces with increasing duration. The impact tests were first carried out on the RC beams without any damage by impact hammer with different hammer heads. Then the RC beams were loaded by a concentrated static force at the mid-span to crack. Impact tests with different hammer heads were repeated on the cracked RC beams. Finally, the cracked beams were further loaded by a concentrated static force to yield of the longitudinal reinforcement. The impact tests were repeated on the yielded beams again. Load cells installed at the supports of the RC beams were used to measure the reaction force generated by the hammer, then DAF was calculated directly by dividing the peak reaction force with the peak impact force. Data obtained from tests, theoretical analysis and specification in codes were compared to examine the DAFs. Results show that the ratio of duration of the impact force and the period of the beams performed a significant effect on the DAFs of the beams.