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RISS 인기검색어
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- 저자 : Wenzhong Zheng (검색결과 4 건)
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Chongchi Hou,Wenzhong Zheng 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.2
The use of lateral reinforcement in confined concrete columns can improve bearing capacity and deformability. The lateral responses of lateral reinforcement significantly influence the effective confining pressure on core concrete. However, lateral strain-axial strain model of concrete columns confined by lateral reinforcement has not received enough attention. In this paper, based on experimental results of 85 concrete columns confined by lateral reinforcement under axial compression, the effect of unconfined concrete compressive strength, volumetric ratio, lateral reinforcement yield strength, and confinement type on lateral strain-axial strain curves was investigated. Through parameter analysis, it indicated that with the same level of axial strain, the lateral strain slightly increased with the increase in the unconfined concrete compressive strength, but decreased with the increase in volumetric ratio significantly. The lateral reinforcement yield strength had slight influence on lateral strain-axial strain curves. At the same level of lateral strain, the axial strain of specimen with spiral was larger than that of specimen with stirrup. Furthermore, a lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression was proposed by introducing the effects of unconfined concrete compressive strength, volumetric ratio, confinement type and effective confining pressure, which showed good agreement with the experimental results.
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Ling Li,Wenzhong Zheng,Ying Wang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.3
This paper presents experimental and analytical investigations on additional fixed-end rotations resulting from the strain penetration of high-strength reinforcement in reinforced concrete (RC) beam-column connections under monotonic loading. The experimental part included the test of 18 interior beam-column connections with straight long steel bars and 24 exterior beam-column connections with hooked and headed steel bars. Rebar strains along the anchorage length were recorded at the yielding and ultimate states. Furthermore, a numerical program was developed to study the effect of strain penetration in beam-column connections. The numerical results showed good agreement with the test results. Finally, 87 simulated specimens were designed with various parameters based on the test specimens. The effect of concrete compressive strength (fc), yield strength (fy), diameter (db), and anchorage length (lah) of the reinforcement in the beam-column connection was examined through a parametric study. The results indicated that additional fixed-end rotations increased with a decrease in fc and an increase in fy, db and lah. Moreover, the growth rate of additional fixed-end rotations at the yielding state was faster than that at the ultimate state when high-strength steel bars were used.
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General Prediction Models for Local Bearing Capacity of Concrete
Sheng Li,Wenzhong Zheng,Wei Zhou,Ying Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.11
The local bearing capacity is a basic mechanical property, which is crucial in the post-tensioned anchorage zone design. However, it is challenging to accurately predict local bearing capacity due to the disordered and complex stress conditions in anchorage zone. The existing prediction models have limited application scope, which are difficult to meet the application requirements of novel materials. In this study, the objective is to develop the general prediction models for evaluating concrete local bearing capacity. A reliable database was established based on the test result datasets collected from this study and previous studies. Then, the influence of concrete strength, local area aspect ratio and duct was analyzed. The calculation model was obtained based on fitting analysis (FA) and artificial neural network (ANN) technology. Besides, both the FA model and ANN model were proven to accurately predict concrete local bearing capacity, according to the prediction performance comparisons with existing typical prediction models.
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Xiaomeng Hou,Muhammad Abid,Wenzhong Zheng,Raja Rizwan Hussain 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.6
Reactive powder concrete (RPC) is an advanced cementitious material with ultra-high strength, remarkable durabil-ity and excellent toughness. However, temperature dependent creep is a major concern as very little work has been reported in the literature. Therefore, systematic investigations are still missing in state of the art. This paper focuses on the impact of Polypropylene (PP) and hybrid (steel and PP) fibers on creep behavior of RPC at elevated tempera-ture. Temperature-dependent creep is further characterized into free thermal strain (FTS), short-term creep (STC) and transient strain (TS), based on different thermo-mechanical regimes. Varying heating and loading schemes were considered such as steady-state and transient thermo-mechanical conditions. The target temperatures considered for steady-state thermal conditions and transient case are 120, 300, 500, 700 and 900 °C. Compressive strength was considered up to 60% load ratio of ambient and temperature dependency. The result shows that STC increases with increasing stress level and higher target temperature. The increase in STC becomes obvious above the transition stage of quartz aggregate. Furthermore, HRPC have significantly higher STC than PRPC and other traditional types of concretes. The evolution of FTS and TS was quite slow below 250 °C. However, at high temperature significant increase in FTS and TS were observed. Furthermore, increasing stress level and the addition of steel fibers results in high TS. Overall, the performance of PP fiber was better than the hybrid fibers on the creep behaviour of RPC. Finally, constitutive relationships were proposed for FTS, STC and TS, which will be used as input data in numerical models of fire resistance calculations.
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