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Strength and stiffness reduction factors for infilled frames with openings

Earthquake Engineering and Engineering Vibration 2014年第3期13卷 437-454页

作者： Luis D.Decanini Laura Liberatore Fabrizio Mollaioli Department of Structural Engineering and Geothecnics "Sapienza" University of Rome

Framed structures are usually infilled with masonry walls. They may cause a significant increase in both stiffness and strength, reducing the deformation demand and increasing the energy dissipation capacity of the system. On the other hand, irregular arrangements of the masonry panels may lead to the concentration of damage in some regions, with negative effects; for example soft story mechanisms and shear failures in short columns. Therefore, the presence ofinfill walls should not be neglected, especially in regions of moderate and high seismicity. To this aim, simple models are available for solid infills walls, such as the diagonal no-tension strut model, while infilled frames with openings have not been adequately investigated. In this study, the effect of openings on the strength and stiffness of infilled frames is investigated by means of about 150 experimental and numerical tests. The main parameters involved are identified and a simple model to take into account the openings in the infills is developed and compared with other models proposed by different researchers. The model, which is based on the use of strength and stiffness reduction factors, takes into account the opening dimensions and presence of reinforcing elements around the opening. An example of an application of the proposed reduction factors is also presented.

关键词： infilled frames openings strength stiffness reduction factor

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Strength reduction factors for structural rubbercrete

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Frontiers of Structural and Civil Engineering 2014年第3期8卷 270-281页

作者： Bashar S. MOHAMMED N. J. AZMI Department of Civil Engineering Universiti Teknologi PETRONAS Tronoh Perak 31750 Malaysia Department of Civil Engineering Universiti Tenaga Nasional Putra Jaya 43000 Malaysia

Many researches have been carried out to study the fresh and hardened properties of concrete containing crumb rubber as replacement to fine aggregate by volume, yet there is no specific guideline has been developed on the mix design of the rubbercrete. The experimental program, which has been developed and reported in this paper, is designed and executed to provide such mix design guidelines. A total of 45 concrete mixes with three different water to cement ratio （0.41, 0.57 and 0.68） were cast and tested for fresh and mechanical properties of rubbercrete such as slump, air content, unit weight, compressive strength, flexural strength, splitting tensile strength and modulus of elasticity. Influence of mix design parameters such as percentage of crumb rubber replacement, cement content, water content, fine aggregate content, and coarse aggregate content were investigated. Three levels of slump value （for conventional concrete mixes） has been selected; low, medium and high slump. In each slump level, water content was kept constant. Equations for the reduction factors （RFs） for compressive strength, flexural strength, splitting tensile strength and modulus of elasticity have been developed. These RFs can be used to design rubbercrete mixes based on the conventional mix （0% crumb rubber content）

关键词： crumb rubber recycled tire mix design reduction factor strength modulus elasticity

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Model-scale tests to examine water pressures acting on potentially buoyant underground structures in clay strata

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 861-872页

作者： Zhisheng Ren Qixian Lu Kaiwen Liu Pengpeng Ni Guoxiong Mei School of Civil Engineering Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Guangdong Key Laboratory of Oceanic Civil EngineeringGuangdong Research Center for Underground Space Exploitation TechnologySun Yat-sen UniversityGuangzhou510275China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education College of Civil Engineering and ArchitectureGuangxi UniversityNanning530004China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China Key Laboratory of High-speed Railway Engineering(MOE) School of Civil EngineeringSouthwest Jiaotong UniversityChengdu610031China

Throughout the service life, underground structures are subjected to transient and sustained hydrostatic pressures. The reservoir impoundment results in an increase in water level, as well as hydraulic gradient,which can endanger the uplift performance of infrastructure. In uplift design, a reduction factor is often suggested for buoyant force acting on underground structures in clays due to the time lag ***, the mechanism of pore pressure generation in clays is not fully understood. This investigation presents a novel U-shaped test chamber to assess the pore pressure generation with time in the horizontal branch subjected to an increase in reservoir level in the left vertical branch. A mathematical model is developed to explain the time lag effect of pore pressure generation. The test program also involves the evaluation of uplift pressure acting on foundation model in the right vertical branch due to adjacent reservoir impoundment. It is found that the time lag effect of pore pressure generation in clays can be observed irrespective of hydraulic gradient, but a higher hydraulic gradient can lead to a faster response in pore pressure sensors. A reduction factor of 0.84-0.87 should be considered to reduce the conservatism of uplift design.

关键词： Buoyant force Reservoir impoundment Pore pressure generation reduction factor Uplift pressure Time lag effect

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Reliability analysis of anti-pull piles under excavation

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Journal of Southeast University(English Edition) 2012年第2期28卷 203-208页

作者：徐志军郑俊杰边晓亚刘勇华中科技大学土木工程与力学学院武汉430074 河南工业大学土木建筑学院郑州450052 新加坡国立大学土木系新加坡119223

The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS） and reliability of system （SYS） are studied. The reduction factor of the pile capacity is used to calculate the reliability indices for the three cases. The ratio ξ of the pile capacity of SLS to the pile capacity of ULS has a significant influence on the reliability indices of SLS and SYS. The mean value μξ of the ratio ξ： is considered as a random variable to study the reliability indices of SLS and SYS. The numerical example demonstrates that the excavation depth and the excavation diameter are proved to have significant influences on the reduction factor of the pile capacity and the reliability indices. The reliability indices decrease with the increase in the excavation depth, and the excavation diameter has a considerable influence on the reliability index when the excavation is relatively deep. In addition, μξ has a significant influence on the reliability indices of SLS and SYS. For a more accurate estimation of μξ, further research should be conducted to study μξ.

关键词： excavation reliability anti-pull piles reduction factor excavation depth excavation diameter

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Experimental Study on Mechanical Properties of Q690 High-Strength Steel after High Cycle Fatigue Damage

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Open Journal of Applied Sciences 2022年第2期12卷 243-255页

作者： Ran Luo School of Civil Engineering and Architecture Southwest University of Science and Technology Mianyang China

Through the static tensile test of Q690 high-strength steel, the relevant mechanical parameters are obtained and the maximum fatigue load is determined. The fatigue life is measured by the fatigue test under the load. According to the fatigue cumulative damage method, the number of fatigue pre-damage vibration is designed in proportion. Then the fatigue pre-damage test is carried out on the high-strength steel, the stress-strain curve and the variation of residual mechanical property reduction coefficient with fatigue damage were drawn. The results show that: compared with the undamaged specimens, the yield strength and tensile strength of Q690 steel are less affected by fatigue damage, but the elongation changes more significantly, and the elastic modulus is not significantly affected. Finally, through the change of mechanical properties of Q690 high-strength steel with different fatigue damage, it provides a scientific basis for the performance evaluation of existing Q690 high-strength steel structure after fatigue damage.

关键词： Q690 High-Strength Steel Fatigue Damage Mechanical Property Stress-Strain Curve reduction factor

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波浪入射角度对不规则波波浪爬高与越浪量的影响

波浪入射角度对不规则波波浪爬高与越浪量的影响

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作者：季文文（Kyi Kyi Lwin）河海大学

学位级别：硕士

In the paper results of basic investigations on irregular wave run-up and overtopping with special regard to oblique wave approach was analyzed. To investigate the influence of angle of wave attack on irregular wave run- up and overtopping, physical model experiments had been performed in the wave basin at Jiangning campus of Hohai University. In all tests a smooth slope of 1:0, 1:1.5 and 1:3 with water depth of 0.5 m and 0.4 m was used. The wave heights H s = 0.06 m, 0.08m, 0.12m and wave period Ts =1.5s: were adopted for the generated spectra. The angle of wave attack β. ranged from 0° to 80° . More than 250 groups of experiment had been carried out. Based on the measurements, a function for the reduction factor γβ describing the influence of wave angle attack on wave run-up and overtopping was created for long crested sea, which was reasonable through comparison. A simple formula for mean wave overtopping discharge was derived based on the test data.Moreover for overtopping the test results from the three models were presented and compared with particular attention to the average overtopping rates.Due to various research tools and methods, different scholars got different calculation methods of wave run-up, but most of research had been oriented at perpendicular wave attack, little on obliquely incoming waves which in- fact are common in nature. Therefore, an investigation concerning about influence of wave angle attack was necessary.In this paper, results of investigation were described into wave run-up and overtopping where the influence of obliquely incoming waves and directional spreading was studied and summarized the results of the investigation.

关键词： irregular wave wave run up wave overtopping incident wave angle reduction factor

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