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T形板肋对预制带肋底板混凝土叠合板弯曲疲劳性能的影响
Influence of T-type rib on flexural fatigue behavior of concrete composite slab with precast prestressed ribbed panel
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黄海林,祝明桥,曾垂军,吕伟荣
- , 2016, DOI: 10.11835/j.issn.1674-4764.2016.02.002
Abstract: 为研究T形板肋对预制带肋底板混凝土叠合板弯曲疲劳性能的影响,对3块T形肋底板叠合板和1块整浇板进行弯曲疲劳性能对比试验,主要考察T形板肋与疲劳荷载幅值对试件疲劳破坏形态及疲劳损伤程度的影响,得到了在不同疲劳循环加载次数下的跨中动位移、混凝土应变、预应力筋应变、残余变形等,分析了在不同疲劳循环加载次数下的刚度退化情况、荷载-应变分布规律、裂缝分布规律及剩余承载力等。研究结果表明,经历200万次疲劳循环加载后,T形肋底板叠合板明显的刚度和强度退化,增设T形板肋的叠合板能达到与整浇板相同的弯曲疲劳性能;T形肋底板叠合板正截面弯曲疲劳强度计算可采用普通预应力混凝土受弯构件正截面疲劳应力验算的4个假定,最终以此建立了其正截面弯曲疲劳强度验算方法。
In order to investigate influence of T-type rib on flexural fatigue behavior of concrete composite slab with precast prestressed ribbed panel, experiment is conducted to study the concrete composite slab with precast prestressed T-type rib panel and cast-in-place slab. The factors influencing the fatigue failure pattern and fatigue damage, such as T-type rib and fatigue load parameter, are studied by fatigue tests. The dynamic deflection, strains of concrete and prestressed tendons, and residual deflection are measured. Stiffness degradation, strain distribution, crack distribution and residual bearing capacity are analyzed. Results show that composite slabs with precast prestressed T-type rib panel can achieve the same flexural fatigue behavior as cast-in-place slabs. Design formulas for normal section bending fatigue strength of concrete composite slab with precast prestressed ribbed panel are put forward with reference to the four assumptions of traditional prestressed concrete flexural member.
Effect of Skew Angle on Distribution of Bending Moments in Bridge Slabs  [PDF]
Maher Shaker Qaqish
Journal of Applied Sciences , 2006,
Abstract: A finite element model was carried out for prestressed precast beams and cast in situ slab bridge. This structural model was subjected to 1.8 AASHTO truck loading, 1.8 AASHTO equivalent distributed loading and abnormal loading. The results for transverse and longitudinal moments were compared with the results obtained from AASHTO specifications. This comparison shows that applying AASHTO specification for slab bridge deck is safe and economical.
Precast Prestressed Concrete Truss-Girder for Roof Applications  [PDF]
Peter Samir,George Morcous
Journal of Structures , 2014, DOI: 10.1155/2014/524156
Abstract: Steel trusses are the most popular system for supporting long-span roofs in commercial buildings, such as warehouses and aircraft hangars. There are several advantages of steel trusses, such as lightweight, ease of handling and erection, and geometric flexibility. However, they have some drawbacks, such as high material and maintenance cost, and low fire resistance. In this paper, a precast concrete truss is proposed as an alternative to steel trusses for spans up to 48?m (160?ft) without intermediate supports. The proposed design is easy to produce and has lower construction and maintenance costs than steel trusses. The truss consists of two segments that are formed using standard bridge girder forms with block-outs in the web which result in having diagonals and vertical members and reduces girder weight. The two segments are then connected using a wet joint and post-tensioned longitudinally to form a crowned truss. The proposed design optimizes the truss-girder member locations, cross-sections, and material use. A 9?m (30?ft) long truss specimen is constructed using self-consolidated concrete to investigate the constructability and structural capacity of the proposed design. A finite element analysis of the specimen is conducted to investigate stresses at truss diagonals, verticals, and connections. Testing results indicate the production and structural efficiency of the developed system. 1. Introduction Structural steel is typically and widely used for long-span roof applications, such as warehouses, storage facilities, and airplanes hangars. Design considerations for roof support system include cost-effectiveness, speed of construction, structural capacity, aesthetic appearance, fire resistance, and structural integrity during construction and in service. Using structural steel has been the only option when it comes to long-span roofs due to ease of handling and erection, geometric flexibility, and lightweight. Concrete has not been a competitive alternative for roof applications due to the heavy weight and construction complexity of concrete components, which results in being less cost effective than steel. Despite the advantages of structural steel roof systems, they have the following disadvantages: low fire resistance, being prone to corrosion, high maintenance cost, long lag period in steel orders, and increasing prices of steel. Most of these disadvantages can be addressed by using precast concrete components as they have excellent fire and corrosion resistance, low production and maintenance cost, and short order period. However, existing
Study on Strengthening of RC Slabs with Different Innovative Techniques  [PDF]
Tarek Ali, Sameh Yehia
Open Journal of Civil Engineering (OJCE) , 2016, DOI: 10.4236/ojce.2016.64044
Abstract: This paper presents a focused study on using different methods to enhance the ultimate capacity of flexural behavior in RC slabs. Four RC specimens were casted with common compressive strength and reinforced with steel mesh. Specimens were strengthened with different methods such as usage of GFRP sheets, carbon fibers laminate strips and near surface mounted steel rebars. All specimens were subjected to two-point loading setup. Load was increased from zero to failure load. First crack was recorded and crack pattern was observed. The behavior of strengthened specimens was compared to that of the control specimen to judge the efficiency of the used techniques. Test results showed that the used techniques were effective in enhancing the behavior of the strengthened slabs by noteworthy values.
Traditional Solutions for Strengthening Reinforced Concrete Slabs  [cached]
Drago? Banu,N. ??ranu
Bulletin of the Polytechnic Institute of Jassy, Constructions, Architechture Section , 2010,
Abstract: Different strengthening techniques have been developed so far for the reinforced concrete slabs with or without cut-outs. The development of these methods was a necessity due to different causes, such as inadequate maintenance, overloading of the reinforced concrete member, corrosion of the steel reinforcement and other different situations that appeared in time. Each of the techniques that are presented in this paper is better suited for a given situation and come with their advantages and disadvantages. These techniques are considered to be traditional do to their long usage in time and that they involve only traditional construction materials such as concrete and steel. The five techniques from this paper have been and are the most effectively used, in the past and present days, worldwide and a short presentation of the methods and the way they are applied is presented in this paper. The selection of one of these methods is imposed by a sum of technological and economical factors.
预应力节段预制拼装桥墩抗震性能研究综述
Review of Seismic Performance of Prestressed Segmental Precast and Assembled Piers
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,,王景全
- , 2016,
Abstract: 为进一步推动预应力节段预制拼装桥墩在高烈度区桥梁工程中的应用,从自复位能力、耗能能力、底节段容许损伤能力和基于性能的抗震设计方法4个方面系统梳理和总结了各国学者开展的相关研究,并指出了当前研究存在的问题以及未来的发展方向。结果表明:无粘结预应力筋能提供更好的自复位能力,桥墩震后残余变形很小;相对于现浇桥墩,该形式桥墩耗能能力较差,需要设置专门的耗能装置,其中外置耗能装置震后可更换,更值得推广;预应力节段预制拼装桥墩鲁棒性差,必须注意提高底节段容许损伤能力;针对预应力节段预制拼装桥墩的基于性能抗震设计才刚刚起步,需要进一步发展。
In order to promote the application of prestressed segmental precast and assembled piers in high seismicity areas bridge engineering, the relevant researches were summarized systematically from four aspects, including self-centering, energy dissipation, damage tolerance of bottom segment and performance??based seismic design, and the existing problems and future research directions were pointed out. The results show that unbonded prestressed tendons can provide better self-centering, and the residual deformation of pier is very small after the earthquake. Compared with the cast-in-place pier, the prestressed segmental precast and assembled pier is poor in energy dissipation capacity and need to set up a special energy dissipation device, in which the external energy dissipation device can be replaced after the earthquake and is worth popularizing. The robust performance of prestressed segmental precast and assembled piers is poor, which should be paid attention to improve the allowable damage ability of the bottom section. The performance-based seismic design of prestressed segmental precast and assembled piers has just started and needs further development
既有预应力宽幅空心板受力性能的破坏性试验
Destructive test on mechanical behavior of existing??prestressed wide hollow slabs
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易汉斌,李传习,吴后选,江祥林
- , 2018,
Abstract: 为了准确评估宽幅空心板构件的承载能力,以昌樟(南昌―樟树)高速公路改扩建工程为依托,对肖江大桥拆除的2片服役20年的预应力混凝土宽幅空心板进行原型试验研究。试验采用2个1 500 kN千斤顶,对空心板进行分级加载直至试件破坏,分析构件的破坏模式及加载过程中挠度、应变随荷载变化的关系;基于退化分层壳元法编程考虑材料、几何非线性的有限元分析程序,并应用该程序对试验全过程进行数值模拟。结果表明:构件破坏模式为顶板混凝土压碎,跨中截面形成塑性铰的典型受弯结构破坏;加载至构件开裂时,1号、2号梁的开裂荷载分别为360、320 kN,对应的实测挠度值分别为22、16 mm,加载至破坏时,1号、2号梁对应的破坏荷载分别为880、??800 kN??,对应的实测挠度值分别为556、540 mm,构件具有较好的延性性能;数值模拟计算的开裂荷载和破坏荷载分别为360、920 kN,为1号梁试验值的1.00、1.05倍,为2号梁试验值的1.13、??1.15??倍,数值模拟计算值与试验结果吻合较好,编程的有限元程序能较好地模拟预应力钢筋混凝土空心板的破坏全过程;由试验结果及理论计算得出,1号、2号梁的活载因子??λ??分别为3.16、2.77,安全系数??S????f分别为1.57、1.43,构件具有较好的承载力性能。??
In order to accurately evaluate the bearing capacity performance of wide hollow slab, based on Changzhang Highway reconstruction and expansion project, a prototype test of two prestressed concrete wide hollow slabs in service for 20 years has been carried out with the opportunity of demolition and reconstruction of Xiaojiang Bridge. In this experiment, two ??1 500 kN?? jacks were used to load the hollow slabs until the specimens were damaged, the failure modes of the components and the relationship between the deflections and strains during the loading process were analyzed. Based on the degradation of layered shell element method, a finite element analysis program considering the consideration of material and geometric nonlinearity was compiled, and the program was used to simulate the whole process of the test. The results show that the failure mode of the component is crushed by the roof concrete, and the typical bending structure of the middle cross section is formed by the plastic hinge,the cracking load of No.1 and No.2 beam is 360 and 320 kN, the corresponding deflection is 22 and 16 mm respectively. While loading to failure, the failure load of No.1 and No.2 is 880 and 800 kN, the corresponding deflection is 556 and 540 mm respectively, which shows that the component has better ductility. The cracking and failure loads calculated by the numerical simulation are 360 and 920 kN, which is 1.00 and 1.05 times as much as that of the test value of No.1, 1.13 and ??1.15?? times as much as that of the test value of No.2. The numerical simulation results are in good agreement with the experimental results, which shows that the nonlinear finite element program developed by the authors can simulate the whole failure process of the prestressed reinforced concrete flexural members well, according to the test results and theoretical calculations, the live load factors of No.1 and No.2 beams are 3.16 and 2.77, and the safety factors are 1.57 and 1.43 respectively, indicating that the component has good
Strengthening of RC Slabs with Symmetric Openings Using GFRP Composite Beams  [PDF]
Yeol Choi,Ik Hyun Park,Sang Goo Kang,Chang-Geun Cho
Polymers , 2013, DOI: 10.3390/polym5041352
Abstract: This paper describes the results of experimental testing of glass fiber reinforced plastic (GFRP) composite beam strengthened reinforced concrete (RC) slabs with two symmetrical openings. Specimens, one-half scale, have been designed and fabricated to reflect the most common RC bathroom slab used in school buildings. The specimen had dimensions of 2000 mm (width) × 150 mm (thickness) × 3000 mm (length) were used with the two openings of 300 mm × 400 mm. The aim of this study is to investigate the most effective strengthening method using GFRP composite beams in slabs with openings for enhancing the load-carrying capacity and stiffness. Test results showed that the strengthened slabs seems to increase the load-carrying capacity by 29%, 21% and 12% over that of the control specimen for diagonal, parallel and surround strengthening respectively. Furthermore, test results showed that the diagonal-strengthened system is one of the most effective methods for strengthening an RC slab with openings in terms of load-carrying capacity, stiffness and crack patterns.
Shear-strengthening of reinforced & prestressed concrete beams using FRP: Part II — Experimental investigation
Thomas H. -K. Kang,Moustapha Ibrahim Ary
International Journal of Concrete Structures and Materials , 2012, DOI: 10.1007/s40069-012-0005-0
Abstract: The main objectives of this research were to experimentally evaluate the impact of Carbon Fiber-Reinforced Polymers (CFRP) amount and strip spacing on the shear behavior of prestressed concrete (PC) beams and to evaluate the applicability of existing analytical models of Fiber-Reinforced Polymer (FRP) shear capacity to PC beams shear-strengthened with CFRP. The Ushaped CFRP strips with different spacing were applied externally to the test specimens in order to observe the overall behavio r of the prestressed concrete I-beams and the mode of failure of the applied CFRP strips. Results obtained from the experimental program showed that the application of CFRP strips to prestressed concrete I-beams did in fact enhance the overall behavior of the specimens. The strengthened specimens responded with an increase in ductility and in shear capacity. However, it should be noted that the CFRP strips were not effective at all at spacing greater than half the effective depth of the specimen and that fracture of the strips was the dominant failure mechanism of CFRP. Further research is needed to confirm the conclusion derived from the experimental program.
高强钢丝绳悬吊加固预制空心楼板试验研究
Experimental Study on Precast Hollow Slab Strengthened by High-strength Steel Wire Rope Suspension
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王滋军,,,吴运伸,,,傅腾飞
- , 2017,
Abstract: 提出采用灌芯加固和悬吊加固相结合的方法提高预制空心楼板承载能力,重点讨论了灌浆加固注浆方法、悬吊加固锚固方式、钢丝绳数量不同对加固性能的影响以及钢丝绳的受力状态。进行7块试件在均布荷载作用下的静力试验,其中2块为对比试件,2块为灌浆加固试件,3块为钢丝绳悬吊加固试件。结果表明:钢丝绳悬吊加固使预制空心楼板极限承载力提高45%~74%,极限位移提高175%~195%;从经济性、施工作业量、承载力提高程度以及预应力钢筋的受力情况综合考虑,4根钢丝绳加固效果最佳,越靠近中间的钢丝绳所起作用越大;该方法加固效果显著,可为加固预制空心楼板的实际应用提供一定借鉴。
A method to improve the bearing capacity of precast hollow slab by the combination of grouting core reinforcement and suspension reinforcement was presented. The grouting method of grouting reinforcement, the anchoring mode of suspension reinforcement, the influence of different quantity of steel wire rope on the reinforcement performance and the stress state of steel wire rope were mainly discussed. The static tests of 7 specimens under uniform load were carried out, including 2 contrast specimens, 2 grouting reinforcement specimens, and 3 steel wire rope suspension reinforcement specimens. The results show that steel wire rope suspension reinforcement can improve the ultimate bearing capacity of precast hollow slab by 45%-74%, and improve the ultimate displacement by 175%-195%. Considering the economical efficiency, construction work quantity, improvement degree of bearing capacity and the stress of prestressed reinforcement, the reinforcement effect of 4 steel wire ropes is best. The reinforcement effect is greater when the steel wire rope is closer to the middle. The reinforcement effect of the method presented is remarkable, which can be used as reference for the practical application of precast hollow slab reinforcement
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