• Title/Summary/Keyword: shear cracks

Search Result 418, Processing Time 0.02 seconds

Torsion strength of single-box multi-cell concrete box girder subjected to combined action of shear and torsion

  • Wang, Qian;Qiu, Wenliang;Zhang, Zhe
    • Structural Engineering and Mechanics
    • /
    • v.55 no.5
    • /
    • pp.953-964
    • /
    • 2015
  • A model has been proposed that can predict the ultimate torsional strength of single-box multi-cell reinforced concrete box girder under combined loading of bending, shear and torsion. Compared with the single-cell box girder, this model takes the influence of inner webs on the distribution of shear flow into account. According to the softening truss theory and thin walled tube theory, a failure criterion is presented and a ultimate torsional strength calculating procedure is established for single-box multi-cell reinforced concrete box girder under combined actions, which considers the effect of tensile stress among the concrete cracks, Mohr stress compatibility and the softened constitutive law of concrete. In this paper the computer program is also compiled to speed up the calculation. The model has been validated by comparing the predicted and experimental members loaded under torsion combined with different ratios of bending and shear. The theoretical torsional strength was in good agreement with the experimental results.

Fatigue analysis of crumble rubber concrete-steel composite beams based on XFEM

  • Han, Qing-Hua;Yang, Guang;Xu, Jie;Wang, Yi-Hong
    • Steel and Composite Structures
    • /
    • v.25 no.1
    • /
    • pp.57-65
    • /
    • 2017
  • The fatigue fracture of studs is the main reason for failure of composite beams based on massive engineering practices. Hence, studying the laws of cracks initiation and propagation are of great directive significance. eXtended Finite Element Method (XFEM) is an effective method in solving moving discontinuous problems in recent years. This paper extends our recent work on the fatigue damage analysis of stud shear connectors in the steel and crumble rubber concrete (RRFC) composite beams based on XFEM. The process of crack initiation to failure of the stud is simulated and an effective calculation criteria for the fatigue life of the composite beams is put forward. After the reliability of the numerical analysis is verified based on tests results, the extensive parametric study is conducted concerning effects of different rubber contents, shear connection degrees and the stress amplitudes. Results show that with the increasing rubber contents and shear connection degrees, the fatigue lives of composite beams increase obviously. Furthermore, the relationship between the fatigue life of the stud at the edge of the shear span and the whole composite beams is studied. Finally, the S-N curves of the single stud and the whole composite beams are put forward based on XFEM.

Effect of progressive shear punch of a foundation on a reinforced concrete building behavior

  • Naghipour, Morteza;Niak, Kia Moghaddas;Shariati, Mahdi;Toghroli, Ali
    • Steel and Composite Structures
    • /
    • v.35 no.2
    • /
    • pp.279-294
    • /
    • 2020
  • Foundation of a building is damaged under service loads during construction. First visit shows that the foundation has been punched at the 6 column's foot region led to building rotation. Foundation shear punching occurring has made some stresses and deflections in construction. In this study, progressing of damage caused by foundation shear punching and inverse loading in order to resolve the building rotation has been evaluated in the foundation and frame of building by finite element modeling in ABAQUS software. The stress values of bars in punched regions of foundation has been deeply exceeded from steel yielding strength and experienced large displacement based on software's results. On the other hand, the values of created stresses in the frame are not too big to make serious damage. In the beams and columns of ground floor, some partial cracks has been occurred and in other floors, the values of stresses are in the elastic zone of materials. Finally, by inverse loading to the frame, the horizontal displacement of floors has been resolved and the values of stresses in frame has been significantly reduced.

Nonlinear behavior of deep reinforced concrete coupling beams

  • Zhao, Z.Z.;Kwan, A.K.H.
    • Structural Engineering and Mechanics
    • /
    • v.15 no.2
    • /
    • pp.181-198
    • /
    • 2003
  • Six large scale models of conventionally reinforced concrete coupling beams with span/depth ratios ranging from 1.17 to 2.00 were tested under monotonically applied shear loads to study their nonlinear behavior using a newly developed test method that maintained equal rotations at the two ends of the coupling beam specimen and allowed for local deformations at the beam-wall joints. By conducting the tests under displacement control, the post-peak behavior and complete load-deflection curves of the coupling beams were obtained for investigation. It was found that after the appearance of flexural and shear cracks, a deep coupling beam would gradually transform itself from an ordinary beam to a truss composed of diagonal concrete struts and longitudinal and transverse steel reinforcement bars. Moreover, in a deep coupling beam, the local deformations at the beam-wall joints could contribute significantly (up to the order of 50%) to the total deflection of the coupling beam, especially at the post-peak stage. Finally, although a coupling beam failing in shear would have a relatively low ductility ratio of only 5 or even lower, a coupling beam failing in flexure could have a relatively high ductility ratio of 10 or higher.

Studying the effects of CFRP and GFRP sheets on the strengthening of self-compacting RC girders

  • Mazloom, Moosa;Mehrvand, Morteza;Pourhaji, Pardis;Savaripour, Azim
    • Structural Monitoring and Maintenance
    • /
    • v.6 no.1
    • /
    • pp.47-66
    • /
    • 2019
  • One method of retrofitting concrete structures is to use fiber reinforced polymers (FRP). In this research, the shear, torsional and flexural strengthening of self-compacting reinforced concrete (RC) girders are fulfilled with glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) materials. At first, for verification, the experimental results were compared with numerical modeling results obtained from ABAQUS software version 6.10. Then the reinforcing sheets were attached to concrete girders in one and two layers. Studying numerical results obtained from ABAQUS software showed that the girders stiffness decreased with the propagations of cracks in them, and then the extra stresses were tolerated by adhesive layers and GFRP and CFRP sheets, which resulted in increasing the bearing capacity of the studied girders. In fact, shear, torsion and bending strengths of the girders increased by reinforcing girders with adding GFRP and CFRP sheets. The samples including two layers of CFRP had the maximum efficiencies that were 90, 76 and 60 percent of improvement in shear, torsion and bending strengths, respectively. It is worth noting that the bearing capacity of concrete girders with adding one layer of CFRP was slightly higher than the ones having two layers of GFRP in all circumstances; therefore, despite the lower initial cost of GFRP, using CFRP can be more economical in some conditions.

Experimental and analytical study on continuous GFRP-concrete decks with steel bars

  • Tong, Zhaojie;Chen, Yiyan;Huang, Qiao;Song, Xiaodong;Luo, Bingqing;Xu, Xiang
    • Structural Engineering and Mechanics
    • /
    • v.76 no.6
    • /
    • pp.737-749
    • /
    • 2020
  • A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

Development and Shear Performance Evaluation of Vertical Joints between Precast Concrete Walls (PC 벽체 수직접합부의 개발 및 전단성능 평가)

  • Moon, Kyo Young;Kim, Sung Jig;Lee, Kihak;Kim, Yong Nam
    • Journal of Korean Association for Spatial Structures
    • /
    • v.22 no.4
    • /
    • pp.81-88
    • /
    • 2022
  • The paper introduces an experimental program for the newly developed vertical joints between Precast Concrete (PC) walls to improve their in-plane shear capacity. Compared to the existing vertical joints, two types of vertical joints were developed by increasing the transverse reinforcement ratio and improving frictional force at the joint interface. A total of four specimens including the Reinforced Concrete (RC) wall and PC walls with developed vertical joints were designed and constructed. The constructed specimens were experimentally investigated through monotonic shear tests. The observed damage, load-deformation relationship, strain and strength are investigated and compared with the cases of RC wall specimen. Experimental results indicate that the maximum force and initial stiffness of the PC wall with proposed vertical joints were decreased by comparing with those of RC wall. However, the ultimate displacement increased by up to 217.30% compared to the RC wall specimen. In addition, brittle failure did not occurred and relatively few cracks and damages occurred.

Effect of high-strength concrete on shear behavior of dry joints in precast concrete segmental bridges

  • Jiang, Haibo;Chen, Ying;Liu, Airong;Wang, Tianlong;Fang, Zhuangcheng
    • Steel and Composite Structures
    • /
    • v.22 no.5
    • /
    • pp.1019-1038
    • /
    • 2016
  • The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

Strength and failure characteristics of the rock-coal combined body with single joint in coal

  • Yin, Da W.;Chen, Shao J.;Chen, Bing;Liu, Xing Q.;Ma, Hong F.
    • Geomechanics and Engineering
    • /
    • v.15 no.5
    • /
    • pp.1113-1124
    • /
    • 2018
  • Geological dynamic hazards during deep coal mining are caused by the failure of a composite system consisting of the rock and coal layers, whereas the joint in coal affects the stability of the composite system. In this paper, the compression test simulations for the rock-coal combined body with single joint in coal were conducted using $PFC^{2D}$ software and especially the effects of joint length and joint angle on strength and failure characteristics in a rock-coal combined body were analyzed. The joint length and joint angle exhibit a deterioration effect on the strength and affect the failure modes. The deterioration effect of joint length of L on the strength can be neglected with a tiny variation at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ between the loading direction and joint direction. While, the deterioration effect of L on strength are relatively large at ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$. And the peak stress and peak strain decrease with the increase of L. Additionally, the deterioration effect of ${\alpha}$ on the strength becomes larger with the increase of L. With the increase of ${\alpha}$, the peak stress and peak strain first decrease and then increase, presenting "V-shaped" curves. And the peak stress and peak strain at ${\alpha}$ of $45^{\circ}$ are the smallest. Moreover, the failure mainly occurs within the coal and no apparent failure is observed for rock. At ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$, the secondary shear cracks generated in or close to the joint tips, cause the structural instability failure of the combined body. Therefore, their failure models present as a shear failure along partial joint plane direction and partially cutting across the coal body or a shear failure along the joint plane direction. However, at ${\alpha}$ of $60^{\circ}$ and L of 10 mm, the "V-shaped" shear cracks cutting across the coal body cause its final failure. While crack nucleations at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ are randomly distributed in the coal, the failure mode shows a V-shaped shear failure cutting across the coal body.

Dynamic Fracture Analysis with State-based Peridynamic Model: Crack Patterns on Stress Waves for Plane Stress Elastic Solid (상태 기반 페리다이나믹 모델에 의한 동적취성파괴 해석: 평면응력 탄성체의 응력 전파와 균열패턴 분석)

  • Ha, Youn Doh
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.28 no.3
    • /
    • pp.309-316
    • /
    • 2015
  • A state-based peridynamic model is able to describe a general constitutive model from the standard continuum theory. The response of a material at a point is dependent on the deformation of all bonds connected to the point within the nonlocal horizon region. Therefore, the state-based peridynamic model permits both the volume and shear changes of the material which is promising to reproduce the complicated dynamic brittle fracture phenomena, such as crack branching, secondary cracks, cascade cracks, crack coalescence, etc. In this paper, the two-dimensional state-based peridynamic model for a linear elastic plane stress solid is employed. The damage model incorporates the energy release rate and the peridynamic energy potential. For brittle glass materials, the impact of the crack-parallel compressive stress waves on the crack branching pattern is investigated. The peridynamic solution for this problem captures the main features, observed experimentally, of dynamic crack propagation and branching. Cascade cracks under strong tensile loading and secondary cracks are also well reproduced with the state-based peridynamic simulations.