• Title/Summary/Keyword: high strength bolts

Search Result 142, Processing Time 0.023 seconds

Evaluation of the Bending Performance of a Modified Steel Grid Composite Deck Joint (격자형 강합성 바닥판의 수정된 이음부에 대한 휨성능 평가)

  • Shin, Hyun-Seop;Park, Ki-Tae
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.17 no.4
    • /
    • pp.38-47
    • /
    • 2013
  • For the joint connection of the precast steel grid composite decks, the prefabricated joint which is composed of concrete shear key and high-tension bolts was already proposed. In this study, for the purpose of increasing the bending stiffness and bending strength of the proposed prefabricated joint section details of the proposed joint are modified, and through experimental tests the bending performance, such as stiffness and strength of a modified joint, is compared with those of the proposed joint. Test and analysis results show that the shear cracks in the concrete shear key are clearly reduced by the strengthening of the shear key using shear studs and additional rebars. According to analysis results of the moment-curvature relationship, bending stiffness of the modified joint is about 47% greater than the stiffness of the proposed joint. Furthermore, the modified joint has about 32% greater bending strength than the proposed joint. Compared to specimens without the joint the modified joint has same or slightly higher bending strength, but about 37% lower bending stiffness.

Experimental Study on Behavior of High Strength Bolted Friction Joint with Oversized and Slotted Holes (과대구멍과 슬롯구멍을 갖는 고력볼트 마찰이음부의 거동에 관한 실험적 연구)

  • Kim, Yong Hwan;Roh, Won Kyoung;Lee, Seong Hui;Kim, Jin Ho;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
    • /
    • v.20 no.6
    • /
    • pp.683-690
    • /
    • 2008
  • When steel fabricators erect structural members in field, temporary tightening of fastener should be useful. However, if bolt holes are not aligned by production error or natural condition, additional effort andpain should be provided to align bolt holes. It lead to longer period than times of construction (a primarily day of construction) and more cost than originally cost. This problem will be overcomed by oversize or slotted holes. Early, AISC and Eurocode have included provision for design process such oversize or slotted holes. But, domestic design method is not refered about oversize and slotted holes. Meanwhile, domestic design method and construction environment are variance with Europe and the United States of America. Therefore, a suitable design method for oversize and slotted holes in domestic real condition is needed. In this study, we evaluated behavior of the joints and decided the friction coefficient on oversize and slotted holes of friction joints with high strength bolts.

A Study of Weldability for Pure Titanium by Nd:YAG Laser(III) - Weld Properties of Edge Welding - (순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(III) - 에지 용접 특성 -)

  • Kim, Jong-Do;Kil, Byung-Lea;Kwak, Myung-Sub;Song, Moo-Keun
    • Journal of Welding and Joining
    • /
    • v.27 no.6
    • /
    • pp.74-79
    • /
    • 2009
  • Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

Behavior of simple precast high-strength concrete beams connected in the maximum bending moment zone using steel extended endplate connections

  • Magdy I. Salama;Jong Wan Hu;Ahmed Almaadawy;Ahmed Hamoda;Basem O. Rageh;Galal Elsamak
    • Steel and Composite Structures
    • /
    • v.50 no.6
    • /
    • pp.627-641
    • /
    • 2024
  • This paper presents an experimental and numerical study to investigate the behavior of the precast segmental concrete beams (PSCBs) utilizing high-strength concrete (HSC) connected in the zone of the maximum bending moment using steel extended endplate connections (EECs). The experimental study consisted of five beams as follows: The first beam was the control beam for comparison, which was an unconnected one-piece beam made of HSC. The other four other beams consisted of two identical pieces of precast concrete. An important point to be noted is that at the end of each piece, a steel plate was used with a thickness of 10 mm. Moreover, this steel plate was welded to the lower and upper reinforcing bars of the beam. Furthermore, the steel plate was made to connect the two pieces using the technique of EECs. Several variables were taken in these four beams, whether from the shape of the connection or enhancing the behavior of the connection using the post-tensioning technique. EECs without stiffeners were used for some of the tested beams. The behavior of these connections was improved using stiffeners and shear bolts. To get accurate results, a comparison was made between the behaviors of the five beams. Another important point to be noted is that Abaqus and SAP2000 programs were used to investigate the behavior of PSCBs and to ensure the accuracy of the modeling process which showed a good agreement with the experimental results. Additionally, the simplified modeling using SAP2000 was able to model the nonlinear behavior of PSCBs connected using steel EECs. It was found that the steel pre-tensioned bolted EECs, reinforced with steel stiffeners and shear anchors, could be used to connect the precast HSC segmental beams via the internal pre-stressing technique.

The Case Study of High Strength Bolt Cadmium Embrittlement Failure (고강도 볼트 카드늄 취성파괴 사례연구)

  • Yoon, Young-In;Park, Chan-Wook;Sohn, Kyung-Suk
    • Proceedings of the KSME Conference
    • /
    • 2008.11a
    • /
    • pp.244-249
    • /
    • 2008
  • It happened a failure on special bolt which supported main landing gear actuator up-lock rod of 00 aircraft. Fracture was occurred at end of center drilled hole and thread machined on bolt. Metallographic, fractographic, and other characteristics of embrittlement analysis and experiments carried out on the failed bolt to find out the reason. Bolt surface was cadmium electroplated(EP) to give lubrication and provide excellent corrosion resistance. Resultly, Bolt was failed due to cadmium embrittlement occurred during baking treatment as well as center drilled hole. for the failure that are relevant to failure analysis and prevention. For their successful functional application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and is complete with no center drilled hole

  • PDF

An Experimental Study on Fatigue Life of Brace Mounting Joint (브레이스 마운팅 결합부의 피로 수명에 관한 실험적 연구)

  • 김동우
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.7 no.3
    • /
    • pp.104-109
    • /
    • 1998
  • This document is a experimental study on fatigue life of brace mounting weld joint. A brace is used to put sub-frame together on the main frame with high strength bolts. It has low fatigue life so a patch is in need for improving a fatigue characteristics of welded joint in brace mounting This paper presents the most pertinent patch size for truck. For this, a critical stress is computed at the point of fatigue crack occurred on truck frame by finite Element Analysis. Using by this critical stress. Designers are able to determin whether fatigue crack is occurred and are able to select a pertinent patch type. And then, with a selected patch type, structural joint stiffness was estimated to compare to the conventional and other patch type or brace mounting Finally, fatigue test were performed to prove a suitability of selected prototype compare with the conventional and other patch type or brace mounting.

Structural Response of Reinforced Concrete Beams Strengthened with CERP Rod

  • Moon Do-Young;Sim Jong-Sung;Oh Hong-Seob
    • Journal of the Korea Concrete Institute
    • /
    • v.17 no.6 s.90
    • /
    • pp.1085-1090
    • /
    • 2005
  • Rod-type fiber reinforced polymer plastics(FRPs) similar to reinforcing steel bars have rarely been considered. In this study, an experiment was performed using beams strengthened with rod-type CFRPs and high-strength mortar overlay. The test results show that the strengthened beams not only had improved endurance limits but also improved load carrying capacities, stiffness values, and cracking loads as compared to a non-strengthened beam. Strengthened beams anchored with bolts throughout their entire span had more efficient structural behaviors, including composite behavior on the interface between the concrete and mortar, and load carrying capacity, than a strengthened beam anchored only on the end block.

The Case Study on Cadmium Embrittlement Failure of High Strength Bolt (고강도 볼트 카드늄 취성파괴 사례연구)

  • Yoon, Young-In
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.13 no.5
    • /
    • pp.769-774
    • /
    • 2010
  • It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

A Experimental Study on the Structural Performance of Column Spliceswith Metal Touch Subjected to Axial Force and Bending Moment (압축력과 휨모멘트를 받는 메탈 터치된 기둥 이음부의 구조성능에 대한 실험적 연구)

  • Hong, Kap Pyo;Kim, Seok Koo;Lee, Joong Won
    • Journal of Korean Society of Steel Construction
    • /
    • v.20 no.5
    • /
    • pp.633-644
    • /
    • 2008
  • The structural framework design uses high-strength bolts and welding in column splices. However, for the column under high compression, the number of the required high-strength bolts can be excessive and the increase of welding results in difficulty of quality inspection, the transformation of the structural steels, and the increase of erection time. According to the AISC criteria, when columns have bearing plates, or they are finished to bear at splices, there shall be sufficient connections to hold all parts securely in place. The Korean standard sets the maximum 25% of the load as criteria. Using direct contact makes it possible to transfer all compressive force through it. The objective of this study is to examine the generally applied stress path mechanism of welded or bolted columns and to verify the bending moment and compression transfer mechanism of the column splice according to metal touch precision. For this study,22 specimens of various geometric shapes were constructed according to the change in the variables for each column splice type, which includes the splice method, gap width, gap axis, presence or absence of splice material, and connector type. The results show that the application of each splice can be improved through the examination of the stress path mechanism upon metal contact. Moreover, the revision of the relative local code on direct contact needs to be reviewed properly for the economics and efficiency of the splices.

Behavior of Concrete-Filled Square Steel Tubular Column to H-Beam Connections using Angles (앵글을 이용한 콘크리트충전 각형강관기둥-H형강보 접합부의 거동)

  • Lee, Jae Seung;Kim, Jae Keon;Shin, Kyung Jae;Moon, Tae Sup
    • Journal of Korean Society of Steel Construction
    • /
    • v.11 no.2 s.39
    • /
    • pp.191-199
    • /
    • 1999
  • This paper is the first step on the study of the industrialization of the mid-story steel building structures. The purpose of this study is to investigate the structural behavior of concrete-filled square steel tubular column to H-beam connections using angles and high tension bolts. The tests are carried out with five types of specimens under static loading and the main parameter is the thickness of angles. Yield-line theory which obtains connection strength by way of the lowest value based on upper-limit theory is applied to predict strength formulas.

  • PDF