• Title, Summary, Keyword: lateral load

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Optimal lateral load pattern for pushover analysis of building structures

  • Habibi, Alireza;Saffari, Hooman;Izadpanah, Mehdi
    • Steel and Composite Structures
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    • v.32 no.1
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    • pp.67-77
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    • 2019
  • Pushover analysis captures the behavior of a structure from fully elastic to collapse. In this analysis, the structure is subjected to increasing lateral load with constant gravity one. Neglecting the effects of the higher modes and the changes in the vibration characteristics during the nonlinear analysis are the main obstacles of the proposed lateral load patterns. To overcome these drawbacks, whereas some methods have been presented to achieve updated lateral load distribution, these methods are not precisely capable to predict the response of structures, precisely. In this study, a new method based on optimization procedure is developed to obtain a lateral load pattern for which the difference between the floor displacements of pushover and Nonlinear Dynamic Analyses (NDA) is minimal. For this purpose, an optimization problem is considered and the genetic algorithm is applied to calculate optimal lateral load pattern. Three special moment resisting steel frames with different dynamic characteristics are simulated and their optimal load patterns are derived. The floor displacements of these frames subjected to the proposed and conventional load patterns are acquired and the accuracy of them is evaluated via comparing with NDA responses. The outcomes reveal that the proposed lateral load distribution is more accurate than the previous ones.

Back-Calculated P-y curves from Lateral Load Tests for Railway Bridge Foundation (수평재하시험을 이용한 철도교 기초의 P-y 곡선에 관한 연구)

  • Kim, Jong-Chil;SaKong, Myung;Cho, Kook-Hwan
    • Proceedings of the KSR Conference
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    • pp.821-828
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    • 2011
  • A significantly larger lateral load and moment are applied on a high speed railway bridge foundation than other bridge foundations. Therefore most of bridge foundations on Honam high speed railway project were designed by high strength steel pipe piles to resist lateral load and moment, which caused the increase of construction costs. In order to perform optimum design, it is important to estimate accurate lateral resistance when designing this type of structure. Lateral load tests were carried out based on the field design data with the purpose of examining the lateral behavioral characteristics of a railway bridge foundation. The standard load test method(ASTM D 3966) was used for field tests by applying twice of design load. Total four load tests were performed on high speed railway bridge foundations with strain gages installed by every 1m along piles to measure load-resistance characteristics under applied lateral loads. The back-calculated P-y curves from strain gages were compared with estimated P-y curves using theoretical methods based on geotechnical investment data. Back-calculated P-y curves from field tests for sand and clay ground conditions were presented in this paper, which are different from theoretical P-y curves. By using the research results of this study, more accurate estimations of pile design under lateral loads can be available for similar geotechnical conditions.

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Lateral Earth Pressures on Buried Pipes due to Lateral Flow of Soft Grounds (연약지반의 측방유동으로 인하여 매설관에 작용하는 측방토압)

  • Hong, Byungsik;Kim, Jaehong
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.9
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    • pp.27-38
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    • 2010
  • A series of model test as well as numerical analysis by FEM was performed to investigate lateral earth pressure acting on a buried pipe in soft ground undergoing horizontal soil movement. A model test apparatus was manufactured so as to simulate horizontal soil movement in model soft ground, in which a model rigid buried pipe was installed. The velocity of soil deformation could be controlled as wanted during testing. The model test was performed on buried pipes with various diameters and shapes to investigate major factors affected the lateral earth pressure. The result of model tests showed that the larger lateral earth pressure acted on the buried pipes under the faster velocity of soil movement. The result of numerical analysis, which was performed under immediate loading condition, showed a similar behavior with the result of model tests under 0.3mm/min to 1.0mm/min velocity of soil deformation. Most of model tests showed the soil deformation-lateral load behavior, in which the first yielding load developed at small soil deformation and elastic behavior was observed by the yielding load. Then, lateral load was kept constant by the second yielding load, in which plastic behavior was observed between the first yielding load and the second yielding one. Beyond the second yielding load, the compression behavior zone was observed. When the velocity was too fast, however, the lateral load was increased with soil deformation beyond the first yielding load without showing the second yielding load. The buried pipes with the larger diameter was subjected to the larger lateral load and the larger increasing rate of lateral load. At small soil deformation, the influence of diameter and shape of buried pipes on lateral load was small. However, when soil deformation was increased considerably, the influence became more and more.

Seismic Performance Evaluation of Multi-Span Bridges considering Effect of Lateral Load Distributions and Equivalent SDOF methods (횡하중 분포와 등가단자유도 방법의 영향을 고려한 다경간 교량의 내진성능 평가)

  • Song, Jong-Keol;Nam, Wang-Hyun;Chung, Yeong-Hwa
    • Journal of Industrial Technology
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    • v.26 no.A
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    • pp.163-171
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    • 2006
  • To evaluate inelastic seismic responses of multi-span-bridge, the equivalent single-degree-of-freedom (ESDOF) methods and the lateral load distributions are applied to the capacity spectrum method(CSM). From the pushover analysis results using the four ESDOF methods and the six types lateral load distributions, the ESDOF method more than lateral load distribution is found to have an important influence upon the pushover analysis. The effects of the higher mode on the bridge seismic behaviors are also increased as the number of pier increase. Therefore, it can be concluded that lateral load distributions and ESDOF methods for reflection of higher mode effects should be considered in the seismic analysis of the bridge structural.

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An Effects of Lateral Reinforcement of High-Strength R/C Columns Subjected to Reversed Cyclic and High-Axail Force (고축력과 반복횡력을 받는 고강도 R/C기둥의 횡보강근 효과)

  • 신성우;안종문
    • Journal of the Korea Concrete Institute
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    • v.11 no.5
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    • pp.3-10
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    • 1999
  • Earthquake resistant R/C frame structures are generally designed to prevent the columns from plastic hinging. R/C columns under higher axial load or strong earthquake showed a brittle behavior due to the deterioration of strength and stiffness degradation. An experimental study was conducted to examine the behavior and to find the relationship between amounts of lateral reinforcements and compressive strength of ten R/C column specimens subjected to reversed cyclic lateral load and higher axial load. Test results are follows : An increase in the amount of lateral reinforcement results in a significant improvement in both ductility and energy dissipation capacities of columns. R/C columns with sub-tie provide the improved ductility capacity than those with closely spaced lateral reinforcement only. While the load resisting capacity of the high strength R/C columns is higher than the normal strength concrete columns under both an identical ratio of lateral reinforcement, however the ductility capacity of high strength R/C columns is decreased considerably. Therefore, the amounts of lateral reinforcement must be designed carefully to secure the sufficient ductility and economic design of HSC columns under higher axial load.

Lateral Load Distribution for Prestressed Concrete Girder Bridge (PSC 거더교의 하중횡분배에 관한 연구)

  • Park, Moon-Ho;Park, Jung- Hwal;Kim, Jin- Kyu
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.2
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    • pp.157-166
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    • 2001
  • The purpose of this study is to examine the accuracy of the code provisions on lateral load distribution factors of prestressed concrete girder bridges. Most designers in Korea use the lever method or lateral load distribution formula in the existing design codes. However, the methods do not account for the effect of bridge skew or direction of diaphragm. Therefore, this study analysed the prestressed concrete girder bridge with grillage model for various girder spacings, directions of diaphragms, span lengths, and skews, and compared the results with those of existing design code. It has been found that lateral load distribution factors were proportional to the girder spacing while they were not significantly affected by the change of span length, direction of diaphragm, and skew. For bending moments, lateral load distribution factors from the grillage analysis were 60%~68% of those from Korean bridge design code. Therefore, the code provisions result in very conservative design. For support reactions, however, lateral load distribution factors from the grillage analysis were slightly greater than those from Korean bridge design code. Therefore, the capacity of bearings of the bridge with a large skew should be determined by grillage analysis.

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Effect of loading rate on mechanical behavior of SRC shearwalls

  • Esaki, Fumiya;Ono, Masayuki
    • Steel and Composite Structures
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    • v.1 no.2
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    • pp.201-212
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    • 2001
  • In order to investigate the effect of the loading rate on the mechanical behavior of SRC shearwalls, we conducted the lateral loading tests on the 1/3 scale model shearwalls whose edge columns were reinforced by H-shaped steel. The specimens were subjected to the reversed cyclic lateral load under a variable axial load. The two types of loading rate, 0.01 cm/sec for the static loading and 1 cm/sec for the dynamic loading were adopted. The failure mode in all specimens was the sliding shear of the in-filled wall panel. The edge columns did not fail in shear. The initial lateral stiffness and lateral load carrying capacity of the shearwalls subjected to the dynamic loading were about 10% larger than those subjected to the static loading. The effects of the arrangement of the H-shaped steel on the lateral load carrying capacity and the lateral load-displacement hysteresis response were not significant.

A lateral load pattern based on energy evaluation for eccentrically braced frames

  • Fakhraddini, Ali;Fadaee, Mohammad Javad;Saffari, Hamed
    • Steel and Composite Structures
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    • v.27 no.5
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    • pp.623-632
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    • 2018
  • Performance-Based Plastic Design (PBPD) method has been recently developed to evaluate the behavior of structures in different performance levels. The PBPD method utilizes a base shear force and a lateral load pattern that are estimated based on energy and yielding mechanism concepts. Using of current lateral force pattern results in weak structural members in upper stories of a structure so that the values of the story drift in these stories are larger than the target drift, particularly in high-rise buildings. Therefore, such distribution requires modifications to overcome this drawback. This paper proposes a modified lateral load pattern for steel Eccentrically Braced Frames (EBFs) based on parametric study. In order to achieve the modified load pattern, a group of 26 EBFs has been analyzed under a set of 20 earthquake ground motions. Additionally, results of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to derive the new load pattern. To prove the efficiency of present study, three EBFs as examples were designed by modified pattern and current PBPD distribution. Inelastic dynamic analyses results showed that the story drifts using modified lateral load pattern were well within the target values in comparison with current pattern in PBPD, particularly where the effect of the height is significant. The modified load pattern reduces the possibility of underdesigning in upper levels and overdesigning in lower levels of the frames.

Experiment of Lateral Load Resistance of Dori-Directional Frame in Traditional Wood Structure System (전통목구조 시스템의 도리방향 골조의 횡저항 성능에 대한 실험)

  • Lee, Young-Wook;Hong, Sung-Gul;Kim, Nam-Hee;Jung, Sung-Jin;Hwang, Jong-Kook;Bae, Boung-Sun
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.241-246
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    • 2007
  • The capacity of a lateral load resistance of a joint with Jangbu-connection of Dori-directional frame in traditional wood structure system was studied, through experiments of 1/2 scaled and T-shaped 7 subassemblies of joint of Dori-directional frame for Deawoongjeon of Bongjungsa. From the experiment, it was shown that the capacity of a lateral load resistance was influenced by the vertical load confining joint and not influenced by the number of Chok and the depth of Changbang, And lateral load resistance mechanism is developed by the restraint between the vertical load and the contacting edge of column; if structure is pushed to the left, the top-right end of Pyeongju contacts with Changbang and left Changbang loses the contacts with Pyeongju and therefore only right Changbang can resist to lateral load.

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Enhancement of the buckling strength of glass beams by means of lateral restraints

  • Belis, J.;Impe, R. Van;Lagae, G.;Vanlaere, W.
    • Structural Engineering and Mechanics
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    • v.15 no.5
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    • pp.495-511
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    • 2003
  • New material applications and transparency are desired by contemporary architects. Its superb transparency and high strength make glass a very suitable building material -in spite of its brittleness- even for primary load bearing structures. Currently we will focus on load bearing glass beams, subjected to different loading types. Since glass beams have a very slender, rectangular cross section, they are sensitive to lateral torsional buckling. Glass beams fail under a critical buckling load at stresses that lie far below the theoretical simple bending strength, due to the complex combination of torsion and out-of-plane bending, which characterises the instability phenomenon. The critical load can be increased considerably by preventing the upper rim from moving out of the beam's plane. Different boundary conditions are examined for different loading types. The load carrying capacity of glass beams can be increased three times and more using relatively simple, cheap lateral restraints.