Punching shear strength of UHPFRC-RC composite flat plates

Wu, Xiangguo,Yu, Shiyan,Xue, Shicheng,Kang, Thomas H.-K.,Hwang, Hyeon-Jong Elsevier 2019 Engineering structures Vol.184 No.-

<P><B>Abstract</B></P> <P>Reinforced concrete (RC) flat plates are vulnerable to punching shear failure due to small effective area for shear resistance. To strengthen the behavior of existing flat plates, use of ultra high performance fiber reinforced concrete (UHPFRC) as a laminate has been pursued. This study focuses on punching shear behavior of RC flat plates retrofitted with UHPFRC overlay (i.e., UHPFRC-RC composite flat plates). To model the axisymmetric UHPFRC-RC composite flat plate, use of the unified strength theory-based punching shear strength model was proposed. Predictions using the proposed model, when compared to existing test results of UHPFRC-RC composite flat plates under concentric load and nonlinear analysis results using ABAQUS, agreed well with the results. Additionally, from the parametric analysis results using the proposed model and nonlinear analysis, the effects of UHPFRC overlay thickness and tensile strength on the punching shear strength were identified.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A punching shear strength model was proposed for UHPFRC-RC composite flat plates. </LI> <LI> UHPFRC overlay increases the load-carrying capacity, but it is limited at a certain point. </LI> <LI> The punching shear strength can be defined as a function of the thickness and strength of UHPFRC overlay. </LI> </UL> </P>

Design and behavior of 160 m-tall post-tensioned precast concrete-steel hybrid wind turbine tower

Xiangguo Wu,Xuesen Zhang,Qingtan Zhang,Dong Zhang,Xiaojing Yang,Faqiang Qiu,Suhyun Park,Thomas H.-K. Kang 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.3

Prefabricated hybrid wind turbine towers (WTTs) are promising due to height increase. This study proposes the use of ultra-high performance concrete (UHPC) to develop a new type of WTT without the need to use reinforcement. It is demonstrated that the UHPC WTT structure without reinforcing bars could achieve performance similar to that of reinforced concrete WTTs. To simplify the design of WTT, a design approach for the calculation of stresses at the horizontal joints of a WTT is proposed. The stress distribution near the region of the horizontal joint of the WTT structure under normal operating conditions and different load actions is studied using the proposed approach, which is validated by the finite element method. A further parametric study shows that the degree of prestressing and the bending moment both significantly affect the principal stress. The shear-to-torsion ratio also shows a significant influence on the principal tensile stress.

Mechanical behavior test and analysis of HEH sandwich external wall panel

Wu, Xiangguo,Zhang, Xuesen,Tao, Xiaokun,Yang, Ming,Yu, Qun,Qiu, Faqiang Techno-Press 2022 Advances in concrete construction Vol.13 No.2

Prefabricated exterior wall panel is the main non-load-bearing component of assembly building, which affects the comprehensive performance of thermal insulation and durability of the building. It is of great significance to develop new prefabricated exterior wall panel with durable and lightweight characteristics for the development of energy-saving and assembly building. In the prefabricated sandwich insulation hanging wall panel, the selection of material for the outer layer and the arrangement of the connector of the inner and outer wall layers affect the mechanical performance and durability of the wall panels. In this paper, high performance cement-based composites (HPFRC) are used in the outer layer of the new type wall panel. FRP bars are used as the interface connector. Through experiments and analysis, the influence of the arrangement of connectors on the mechanical behaviors of thin-walled composite wall panel and the panel with window openings under two working conditions are investigated. The failure modes and the role of connectors of thin-walled composite wallboard are analyzed. The influence of the thickness of the wall layer and their combination on the strain growth of the control section, the initial crack resistance, the ultimate bearing capacity and the deformation of the wall panels are analyzed. The research work provides a technical reference for the engineering design of the light-weight thin-walled and durable composite sandwich wall panel.

First Diagonal Cracking and Ultimate Shear of I-Shaped Reinforced Girders of Ultra High Performance Fiber Reinforced Concrete without Stirrup

Xiangguo Wu,Sang-Mook Han 한국콘크리트학회 2009 International Journal of Concrete Structures and M Vol.3 No.1

The first diagonal cracking and ultimate shear load of reinforced girder made of ultra high performance fiber reinforced concrete (UHPFRC) were investigated in this paper. Eleven girders were tested in which eight girders failed in shear. A simplified formulation for the first diagonal cracking load was proposed. An analytical model to predict the ultimate shear load was formulated based on the two bounds theory. A fiber reinforcing parameter was constituted based on the random assumption of steel fiber uniform distribution. The predicted values were compared with the conventional predictions and the test results. The proposed equation can be used for the first cracking status analysis, while the proposed equations for computing the ultimate shear strength can be used for the ultimate failure status analysis, which can also be utilized for numerical limit analysis of reinforced UHPFRC girder. The established fiber reinforcing theoretical model can also be a reference for micro-mechanics analysis of UHPFRC.

Preliminary design and structural responses of typical hybrid wind tower made of ultra high performance cementitious composites

Xiangguo Wu,Jing Yang,Issa B. Mpalla 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.6

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.

Multiple Cracking Model of Fiber Reinforced High Performance Cementitious Composites under Uniaxial Tension

Wu, Xiangguo,Han, Sang-Mook Korea Concrete Institute 2009 International Journal of Concrete Structures and M Vol.3 No.1

A theoretical model of multiple cracking failure mechanism is proposed herein for fiber reinforced high performance Cementitious composites. By introducing partial debonding energy dissipation on non-first cracking plane and fiber reinforcing parameter, the failure mechanism model of multiple cracking is established based on the equilibrium assumption of total energy dissipation on the first crack plane and non-first cracking plane. Based on the assumption of the first crack to be the final failure crack, energy dissipation terms including complete debonding energy, partial debonding energy, strain energy of steel fiber, frictional energy, and matrix fracture energy have been modified and simplified. By comparing multiple cracking number and energy dissipations with experiment results of the reference's data, it indicates that this model can describe the multiple cracking behavior of fiber reinforced high performance cementitious composites and the influence of the partial debonding term on energy dissipation is significant. The model proposed may lay a foundation for the predictions of the first cracking capacity and post cracking capacity of fiber reinforced high performance cementitious composites and also can be a reference for optimal mixture for construction cost.

Behavior of UHPC-RW-RC wall panel under various temperature and humidity conditions

Wu, Xiangguo,Yu, Shiyuan,Tao, Xiaokun,Chen, Baochun,Liu, Hui,Yang, Ming,Kang, Thomas H.K. Techno-Press 2020 Advances in concrete construction Vol.9 No.5

Mechanical and thermal properties of composite sandwich wall panels are affected by changes in their external environment. Humidity and temperature changes induce stress on wall panels and their core connectors. Under the action of ambient temperature, temperature on the outer layer of the wall panel changes greatly, while that on the inner layer only changes slightly. As a result, stress concentration exists at the intersection of the connector and the wall blade. In this paper, temperature field and stress field distribution of UHPC-RW-RC (Ultra-High Performance Concrete - Rock Wool - Reinforced Concrete) wall panel under high temperature-sprinkling and heating-freezing conditions were investigated by using the general finite element software ABAQUS. Additionally, design of the connection between the wall panel and the main structure is proposed. Findings may serve as a scientific reference for design of high performance composite sandwich wall panels.

Axial Load Testing of Hybrid Concrete Columns Consisting of UHPFRC Tube and Normal-Strength Concrete Core

Xiangguo Wu,Thomas H.-K. Kang,Issa Brown Mpalla,Chang-Soo Kim 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.4

To investigate the axial load behavior of hybrid concrete columns consisting of an ultra-high performance fiber-reinforced concrete tube (20 mm thick, 92.6 MPa or 143.3 MPa) and normal-strength concrete core (28.2 MPa), concentric axial load tests were performed for five column specimens. The UHPFRC tube can function as a form during core-filling and as a cover having high performance at service and ultimate load conditions. Axial loading was applied to the core only, and the tube was indirectly loaded by bearing of transverse threaded bars. Test parameters included the volume fraction of steel fibers, volumetric ratio of transverse bars, and usage of wire-mesh in the tube. Test results showed that structural performance such as initial stiffness, peak load, displacement ductility, and energy absorption capacity varied greatly according to each test parameter. During the course of axial loading applied on the core only, the axial load behavior of the hybrid concrete columns generally corresponded to the full composite action at the initial loading stage and then changed to that of non-composite action (core only) after the failure of the threaded bars.

Multiple Cracking Model of Fiber Reinforced High Performance Cementitious Composites under Uniaxial Tension

Xiangguo Wu,Sang-Mook Han 한국콘크리트학회 2009 International Journal of Concrete Structures and M Vol.3 No.1

A theoretical model of multiple cracking failure mechanism is proposed herein for fiber reinforced high performance Cementitious composites. By introducing partial debonding energy dissipation on non-first cracking plane and fiber reinforcing parameter, the failure mechanism model of multiple cracking is established based on the equilibrium assumption of total energy dissipation on the first crack plane and non-first cracking plane. Based on the assumption of the first crack to be the final failure crack, energy dissipation terms including complete debonding energy, partial debonding energy, strain energy of steel fiber, frictional energy, and matrix fracture energy have been modified and simplified. By comparing multiple cracking number and energy dissipations with experiment results of the reference’s data, it indicates that this model can describe the multiple cracking behavior of fiber reinforced high performance cementitious composites and the influence of the partial debonding term on energy dissipation is significant. The model proposed may lay a foundation for the predictions of the first cracking capacity and post cracking capacity of fiber reinforced high performance cementitious composites and also can be a reference for optimal mixture for construction cost.

Preliminary design and structural responses of typical hybrid wind tower made of ultra high performance cementitious composites

Wu, Xiangguo,Yang, Jing,Mpalla, Issa B. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.6

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.