The Shear Behavior of Precast Concrete Sandwich Panels with W-shaped SGFRP Shear Connectors

Huanzhi Jiang,Zhengxing Guo,Jiabin Liu,Hui Liu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

This paper presents a horizontal direct shear push-out test program to evaluate the shear behavior of Precast Concrete Sandwich Panel (PCSP) systems with W-shaped Steel Glass Fiber-reinforced Polymer (SGFRP) shear connectors. The experimental program is composed of twelve PCSPs reinforced with W-shaped SGFRP connectors and six PCSPs for comparison that were panels using pure W-shaped GFRP connectors, GFRP pin connectors and stainless-steel truss connectors. The peak shear load, the relationships of shear force-average relative slip, the shear performance of each connector, and the effects of different height, angle and diameter of the SGFRP connector were investigated in this paper. The test results indicate that all specimens with the W-shaped SGFRP shear connectors in this study exhibited an elastic-brittle response caused by pull-out of certain connectors before the ultimate strength was utilized fully and the ductility of the SGFRP material did not play out. Nevertheless, the shear capacity of panels with SGFRP connectors was approximately 2 times that with pure W-shaped GFRP connectors in the case of all parameters being the same, approximately 2 times that with stainless-steel truss connectors for which diameter was reduced by a half, and approximately 2.5 times that with GFRP pin connectors. A reasonable design of connector diameter, spacing and measure of strengthened anchorage is required to ensure the ductile failure of panels.

Experimental Evaluation of Precast Concrete Beam-Column Connections with High-strength Steel Rebars

Dongzhi Guan,Zhengxing Guo,Cheng Jiang,Sen Yang,Hui Yang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

A novel precast concrete beam-column connection partially reinforced with high-strength steel rebars of a yield strength greater than 630 MPa was introduced to avoid reinforcement obstruction in connection zones. Reversed cyclic loadings were applied to fullscale specimens to evaluate their seismic performance. For the first precast specimen, high-strength steel rebars acted as bottom longitudinal bars of the beams. For the second precast specimen, high-strength steel rebars were used as both bottom longitudinal bars and embedded bars that were anchored into the joint. The results show that the new precast connection exhibits a satisfactory seismic resistance. The anchored embedded bars are not necessary in the new system for a limited improvement in the structural performance. The mechanical equilibrium of the rectangular stress block method can be applied to estimate the strength of the new connection using the design philosophy of strong column-weak beam.

In-Plane Quasi-Static Cyclic Tests on Emulative Precast Concrete Walls

Zhu Zhangfeng,Guo Zhengxing 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

This paper presents two types of emulative precast concrete walls with dry horizontal connection and semi-dry horizontalconnection. As for dry connection, vertical continuity reinforcing bars are grouted in metal bellows embedded in the precast wallpanel. As for semi-dry connection, the web reinforcing bars are still grouted in embedded metal bellows while the reinforcing barswithin boundary elements are overlapped and anchored in cast-in-place concrete. To assess the seismic performance of the twoconnections, three full-scale specimens, including one reference monolithic specimen and two precast specimens for eachconnection, were prefabricated and tested under in-plane quasi-static cyclic loading. The strength, stiffness, displacement ductility,and energy dissipation of the specimens were measured and compared. The experimental results demonstrated that, compared withthe monolithic specimen, both precast specimens exhibited satisfactory behavior and the semi-dry precast specimen performed betterthan the dry precast specimen in terms of ductility and energy dissipation. In addition, the analytical results showed that precastspecimens exhibited reliable seismic performance with high bearing capacity and large deformation capacity.

Effect of Grout Properties on Bond Behavior of Grouted Pipe Splice

Yongfeng Zheng,Zhengxing Guo,Xin Zhang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

The effect of compressive strength and expansion rate of filler grout on bond behavior of grouted pipe splice is discussed. Threetypes of grout were designed and utilized to prepare coupler specimens as filler material. The compressive strength ranged from 67.5to 91.8 MPa. The volume expansion rate changed from -0.023% to -0.037% under airtight curing condition, and from 0.027% to0.057% under water curing condition, respectively. Based on pullout test, it was found that the bond strength and stiffness of groutedsplice both improve with the increment of the expansion rate due to the increased initial confinement. By experimentally measuringthe exterior surface transverse strain of grouted sleeve in curing stage, the confinement and its influencing factor on bondperformance were derived. The confinement increases nonlinearly with the increment of grout shell thickness and sleeve radialstiffness other than grout expansion rate. The diameter-thickness ratio of sleeve should not exceed 13 to avoid a possible debondingfailure at bar-grout interface. Utilizing the calculated confining pressures, the bond strength of the grouted splice was determined andcompared with pullout test result, which shows a good agreement.

Composite Behavior of Sandwich Panels with W-Shaped SGFRP Connectors

Huanzhi Jiang,Zhengxing Guo,Jiabin Liu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5

The composite behavior and structural behavior of four full-scale precast concrete sandwich panels (PCSPs) with different numberand distribution of W-shaped steel glass fiber reinforced polymer (SGFRP) shear connectors were investigated both experimentallyand theoretically in this paper. Test results showed that the number of W-shaped SGFRP connectors in the panel ends a third ratherthan in the middle section has a significant impact on the flexural capacity and the composite action of PCSPs. The ultimate loadincreased in proportion to the number of W-Connectors in both panel ends a third approximately. The shear connectors could transfera large level of shear from one wythe to the other to enable the two concrete wythes to exhibit partially composite behavior. Thedegree of partially composite action of the tested PCSPs achieved obviously different depending on the number of connectors in theends a third. Good correlation was found between experimental obtained results and the theoretical calculation results of the degreeof composite action.

Experimental Study on Emulative Hybrid Precast Concrete Shear Walls

Zhu Zhangfeng,Guo Zhengxing 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

The reversed cyclic lateral loading experiments were conducted on three, full scale, emulative hybrid precast concrete shear wall specimens with different post-tensioned forces and one reference monolithic RC shear wall specimen, and the measured results were then discussed in this paper. The emulative hybrid wall combined grouted vertical reinforcements with unbonded post-tensioned high-strength multi-strand tendons for lateral resistance, attempting to emulate the cast-in-place RC wall. Because of the presence of the unbonded post-tensioned tendon, by contrast to the monolithic wall specimen, the emulative hybrid wall specimens possessed higher strength, higher stiffness, and smaller residual displacement. The opening gap, resulted from the discontinuity of concrete and the locally debonding of vertical connecting reinforcements, was limited mainly due to the vertical connecting reinforcements across the joint distributed over total cross-section. Meanwhile, the emulative hybrid wall specimens were capable of providing energy dissipation and ductility capacity comparable to that of the monolithic specimen, and the negative effect of the post-tensioned force on energy dissipation was more obvious than on ductility. Moreover, the post-tensioned tendon remained elastic throughout the test and the yielding of the connecting reinforcements was delayed.

Reversed Cyclic Loading Test on Emulative Hybrid Precast Concrete Shear Walls under Different Vertical Loads

Zhu Zhangfeng,Guo Zhengxing 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

An experiment was carried out to investigate the seismic performance of hybrid precast concrete shear walls, which aimed to emulate the monolithic RC wall by incorporating unbonded post-tensioned high-strength strands and vertically connected reinforcing bars by grouting across the horizontal joint for lateral resistance. The unbonded tendons provided the pre-compression and the recentering force. The grouted reinforcing bars were used to provide the bending strength, reduce the gap opening size, and eliminate the horizontal slippage along the joint. Three full-scale emulative hybrid wall specimens under different vertical loads and one monolithic RC wall specimen for reference were subjected to reversed cyclic loading. The test results showed that, the emulative hybrid specimens, with vertical load less than or equal to that of the monolithic specimen, exhibited good lateral performance and the seismic properties, including strength, stiffness, ductility and energy dissipation, were comparable to that of the monolithic specimen. As the vertical load increased, the strength and stiffness were enhanced, however, the energy absorbing capacity was obviously decreased.

Seismic Behavior of Precast Concrete Shear Walls with Different Confined Boundary Elements

Zhangfeng Zhu,Zhengxing Guo 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2

To ensure the mechanical property of lapped spliced reinforcement and concrete confinement of boundary elements for precast concrete shears, two kinds of constraints, local constraint by additional spiral stirrups placed around each reinforcement splicing and overall constraint by lapped welding closed stirrups replacing traditional stirrups and ties, were proposed in this paper. Low-cyclic reversed loading tests were conducted on three full scale specimens, including one reference cast-in-situ specimen, one precast concrete specimen with local constraint and one precast concrete specimen with overall constraint. By comparing the aspects of strength, stiffness, ductility and energy-dissipation capacity with that of cast-in-situ specimen, it is found that local constraint and overall constraint can be considered equivalent. However, due to the over restraint by local constraint detail, the specimen with local constraint exhibited earlier yielding, poorer energy-dissipation capacity and better ductility than that with overall constraint. Coupled with the consideration of steel usage and construction simplicity, overall constraint detail should be preferred in practical engineering.

Accumulative Traction Construction Analysis of the FAST Cable-net Structure

Bin Luo,Mingmin Ding,Guorui Xie,Zhengxing Guo 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.10

Considering the distinctive structural features and complex construction aspects of the five-hundred-meter aperture spherical radio telescope (FAST), this paper proposes the accumulative traction of serial cable construction technology (ATSC). This method makes full use of the guiding function and load-bearing capacity of guide ropes, which are simple and inexpensive, and the setting of catwalks is avoided. The entire ATSC process is divided into several static cases, and the NDFEM form-finding method is introduced to obtain the structural response of each case. Based on the principle of the constant total unstressed length of guide-rope elements, two strategies and a varying multiplication coefficient, λ, are introduced, and the “element length recursive multiplication” strategy is found to excel in terms of the analysis efficiency. Additionally, the total unstressed length of the guide-rope elements is set to three different values to determine the configuration trends. The results show that the most unfavorable configuration of guide ropes exists in initial cases and that the optimal unstressed length of the guide rope lies at an intermediate value between the total unstressed length of the serial main cables and the straight-line distance between the two endpoints of the guide rope for FAST.

Development of miniature bar-type structural fuses with cold formed bolted connections

Dongzhi Guan,Sen Yang,Liang-Jiu Jia,Zhengxing Guo 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.1

A novel all-steel miniature bar-type structural fuse (MBSF) with cold formed bolted connections is developed in this study, which consists of a central energy dissipation core cut from a smooth round bar, an external confining tube and nuts. Three types of cross sections for the central energy dissipation core, i.e., triple-cut, double-cut and single-cut cross sections, were studied. Totally 18 specimens were axially tested under either symmetric or asymmetric cyclic loading histories, where the parameters such as cut cross sectional area ratio, length of the yielding portion and cross sectional type were investigated. Numerical simulation of 2 representative specimens were also conducted. An analytical model to evaluate the bending failure at the elastic portion was proposed, and a design method to avoid this failure mode was also presented. The experimental results show that the proposed MBSFs exhibit satisfactory hysteretic performance under both the two cyclic loading histories. Average strain values of 8% and 4% are found to be respectively suitable for designing the new MBSFs as the ultimate strain under the symmetric and asymmetric cyclic loadings.