Post Tensioned CFRP tubes for improved energy absorption

Thin-walled tubes made of CFRP (Carbon fiber reinforced Polymer) are being increasingly used as CC (Crush Cans) due to their higher specific energy absorption capacity in the automotive domain for absorbing impact energy during a frontal crash. Finite element analysis (FEA) based computational methods have matured over the years with increased accuracy and acceptable correlation with experimental results. FEA-based computational studies when used appropriately can reduce the number of physical tests and prototypes required besides accelerating the overall cycle design time. The present work proposes an FEA based design validation approach for the evaluation of post-tensioned crush can design that can absorb more impact energy compared to a normal CFRP thin tube. The FEM based method uses a combination of multiple simulation techniques to predict the behavior of a post-tensioned tube. The post-tensioning in the present work has been proposed in the form of internal pressure for the thin tube. It was found that a safe value of pressure, when applied as a post-tensioning load, can improve the energy absorption capacity without increasing the weight of the tube.

Analysis of Bearing Strength of Post-Tensioning Anchorage Zone with Respect to Relative Bearing Area and Lateral Confinement Design

This study aimed to evaluate the bearing strength of the post-tensioning anchorage zone with respect to the relative bearing area and lateral confinement design of spiral and stirrup rebars. Eleven specimens were fabricated and tested to fracture in accordance with EAD 160004-00-0301. Load-displacement curves and fracture modes were analyzed. Then, the conventional design equation for the bearing strength and previous findings on the relative bearing area was re-investigated in comparison with the test results. From the test, the representative findings are as follows: (1) A specimen with relatively small size and less lateral reinforcement is more likely to be affected by the wedge action of the anchorage device; however, a larger specimen is affected by both concrete crushing and/or spalling; (2) The behavior of the anchorage zone is markedly affected by the local behavior near the anchorage bearing plate, and the sectional efficiency is mostly determined by A/Ag; (3) For specimens with A/Ag = 9.52, the proportional limit of the load-displacement curve is determined by the yield of spiral rebar or fracture of the bearing plate, but the later part of the curve is determined by lateral confinement; (4) The maximum A/Ag that could produce 100% sectional efficiency is about 2.0 for the anchorage bearing plate used in the test; (5) For a fully confined specimen with a small-diameter spiral for minimum anchorage spacing, the stirrup rebar design mainly influences crack occurrence and patterns when the size of the specimen is equal to the minimum anchorage spacing; however, the area of the load-displacement curve after the proportional limit as well as crack occurrence and patterns are also influenced by stirrup rebar design when A/Ag is relatively large; (6) Finally, a revised design model is proposed to effectively estimate the ultimate bearing strength of the post-tensioning anchorage zone without respect to A/Ag. From the comparison of the design equations, it was concluded that the proposed equation provides a more reliable prediction with a 14.0% average error rate and 5.7% standard deviation of error rate.

Performance of a Ductile Hybrid Post-Tensioned Beam-to-Column Connection for Precast Concrete Frames under Seismic Loads: A Review

The performance of precast concrete frame structures against seismic loads mainly depends on the beam-to-column connection. A ductile hybrid connection consists of unbonded post-tensioning steel and bonded reinforcement bars, both of which provide overall moment resistance to the frame. Post-tensioning steel acts as a restoring force which brings the structure back to its initial position upon unloading. Mild steel acts as an energy dissipator which yields in tension and compression. To evaluate the performance of precast frame structures, the structural engineer requires extensive knowledge of the complex nonlinear behavior of the connection. Standardization to mass produce is one of the benefits of precast construction, but with standardization in design there is severe risk. All previous earthquakes have clearly shown that continuous repetition of accepted practice without proper engineering review can lead to disaster. It is important to understand how different parameters of the connection influence the behavior and performance of the frame against seismic loads. The present study helps structural engineers and researchers with a detailed review of hybrid post-tensioned connections. This review is focused mainly on precast beam-to-column connections, studies on the development of hybrid connections, performance evaluations of hybrid connections, and the performance evaluation of precast frames with hybrid connections.

Analysis of Multi-Storied Building with Prestressed Beam using ETABS

Concrete is good in compression and weak in tension and the steel is strong in tension. So the use of reinforced concrete to resist compression and to hold bars in position and to the steel resist tension. In India RCC structures are commonly used in residential as well as business buildings. Nowadays the Post Tensioning method is widely used due to its advantages. Post tensioning is a form of prestressing, that means the steel is stressed before the concrete has to support the service loads. In this paper is exposed to the assessment of execution of Reinforced concrete beam (RCC beam) and Post-Tensioning beam (PT beam) multistoried building structure framework with seismic load using ETABS software. And also evaluate the performance of PT beam under different seismic zone (zone I, zone II) evaluate the performance of PT beam under soil type (medium soil) and compare the performance of RCC deep beam and PT beam with multistory building system with seismic loading performance.

STUDI ALTERNATIF STRUKTUR ATAS JEMBATAN DENGAN BALOK GIRDER PRATEGANG TIPE I

Seiring dengan perkembangan jaman dan mengingat semakin meningkatnya volume lalu lintas kendaraan yang akan melewati Jembatan Langgaliru, maka perlu direncanakan alternatif struktur atas Jembatan Langgaliru dengan menggunakan balok girder prategang.Bentuk penampang balok girder yang digunakan pada perencanaan adalh balok girder tipe I. Pemberian tegangan dilakukan dengan metode Pasca Tarik (Post-Tensioning) dimana compressive force diinduksi ke dalam struktur beton dengan menggunakan high strength steel tendon yang dipasang dalam ducts embedded dalam beton. Tendon distressing setelah beton dicor dan dicuring sampai kuat tekan beton yang disyaratkan. Jumlah tendon yang digunakan 3 buah yang masing-masing tendon terdiri dari 15 untaian(strand).Tulangan Geser yang digunakan adalah D 19 – 250,penghubung geser yang digunakan adalah D 19 – 700,pulangan pecah ledak arah vertikal yang digunakan adalah D 10 – 550,tulangan pecah ledak arah horizontal yang digunakan adalah D 10 – 550, Tulangan Pecah Gumpal arah vertikal yang digunakan adalah D 36 – 60,tulangan pecah gumpal arah horizontal yang digunakan adalah D 36 – 240.