• Earthquakes and Structures
• /
• 제12권3호
• /
• pp.349-357
• /
• 2017

The design of reinforced concrete structures strongly depends on the value of the compression concrete strength used for the structural components. Given the uncertainties involved on the materials quality provided by concrete manufacturers, in the construction stage, these components may be either over or under-reinforced respect to the nominal condition. If the structure is under reinforced, and the deficit on safety level is not as large to require the structure demolition, someone should assume the consequences, and pay for the under standard condition by means of a penalty. If the structure is over reinforced, and other failure modes are not induced, the builder may receive a bonus, as a consequence of the higher, although unrequested, building resistance. The change on the building safety level is even more critical when the structure is under a seismic environment. In this research, a reliability-based criteria, including the consideration of expected losses, is proposed for bonification/penalization, when there are moderated differences between the supplied and specified reinforced concrete strength for the buildings. The formulation is applied to two hypothetical, with regular structural type, 3 and 10 levels reinforced concrete buildings, located on the soft soil zone of Mexico City. They were designed under the current Mexican code regulations, and their responses for typical spectral pseudoaccelerations, combined with their respective occurrence probabilities, are used to calculate the building failure probability. The results are aimed at providing objective basis to start a negotiation towards a satisfactory agreement between the involved parts. The main contribution resides on the explicit consideration of potential losses, including the building and contents losses and the business interruption due to the reconstruction period.

• 한국건설순환자원학회논문집
• /
• 제3권1호
• /
• pp.58-63
• /
• 2015

현재까지 알칼리 활성화제를 사용한 무시멘트 콘크리트의 연구는 슬럼프, 강도 및 내구성 등 기본적인 재료성질에 대해서 주로 수행되어져 왔다. 그러나 알칼리 활성화제를 사용한 무시멘트 콘크리트의 구조부재에의 적용을 위해서는 탄성계수, 응력-변형률 관계 및 구조 부재 거동 등에 대한 연구가 필수적이다. 본 논문에서는 50MPa급 알칼리 활성 슬래그 콘크리트를 사용한 철근콘크리트 보시험체 6개를 제작한 후, 전단실험을 수행하였다. 실험과 해석에 의해 얻은 공칭전단강도는 전단철근이 배치되어 있는 시험체에서는 최대 18% 정도의 차이를 보이나, 전단철근이 없는 시험체에서는 최대 31% 정도의 차이를 보였으며 또한 알칼리 활성 슬래그 콘크리트의 설계전단강도에 비하여 전단강도 실험값이 22~57% 정도 크게 나타나 전단설계식이 상당히 안전측임을 알 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권3호
• /
• pp.403-412
• /
• 2018

Medium-scale tests were conducted to measure and observe the strength and failure behavior of freshwater ice rubble. A custom box measuring $3.05m{\times}0.94m{\times}0.94m$, with Plexiglas walls was built so that failure mechanisms could be observed. Ice rubble beams of nominal thickness 50 cm were produced by placing randomly sized ice pieces into the box filled with water at its freezing temperature. After the specified consolidation time, ranging between 0.2 and 70.5 h, the ice rubble beam was deformed by pushing a platen vertically downwards though the center of the beam until failure. For consolidation times less than 4 h, the ice beam failed progressively and tended to fail by shearing on macroscopic scale. At times greater than 4 h the beam failed by bending. The change in failure behaviour has been attributed to the degree of bonding between ice blocks.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
• /
• pp.755-760
• /
• 1998

In the present, we have developed high strength concrete for the sleepers of high speed rail and verified its applicability by in-situ applications. Concrete for sleepers is manufactured by steam curing at low temperature(below 55$^{\circ}C$), and should be finished its manufacturing process such as placing, curing, demolding and prestressing in 24 hours. The sleepers need its compressive strength above 350kg/$\textrm{cm}^2$ in 15 hours, air-entrainment for durability and nominal design strength of 600kg/$\textrm{cm}^2$, considering its quality variation at factory. We performed the optimum mix design of concrete and verified the rightness of the use of TYPE III cement. Finally, we have confirmed the manufactured sleepers satisfy the required material properties through in-situ application.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 추계학술발표대회 논문집
• /
• pp.70-73
• /
• 2001

The layup optimization by genetic algorithm (GA) for the interlaminar strength of laminated composites with free edge is presented. For the calculation of interlaminar stresses of composite laminates with free edges, extended Kantorovich method is applied. In the formulation of GA, repair strategy is adopted for the satisfaction of given constraints. In order to consider the bounded uncertainty of material properties, convex modeling is used. Results of GA optimization with scattered properties are compared with those of optimization with nominal properties. The GA combined with convex modeling can work as a practical tool for maximum interlaminar strength design of laminated composite structures, since uncertainties are always encountered in composite materials and the optimal results can be changed.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.84-87
• /
• 2004

Nominal flexural strength of RC members strengthened with FRP sheets is generally based on the tensile strength of composite materials obtained from coupon tests. This method is based on the assumption that bond failure does not occur until the FRP sheet reaches its rupture strength. According to the previous researches, however, bond failure often occurs before the FRP sheet reaches its rupture strength. Some attempts were made to control debonding failure by increasing the bonded length of sheet or wrapping the section around their side of the member(U-wrap). In this study, the flexural failure mechanism of RC beams strengthened with AFRP sheets with different bond lengths is investigated. Their strengthening details to prevent the premature debonding failure are also suggested and its effectiveness is verified.

• 한국해양공학회지
• /
• 제10권3호
• /
• pp.24-33
• /
• 1996

Up to now, most of studies on mechanical properties in friction welded components are about tensile and bending strength. However the fatigue studies on the friction-welded components subjected to repeated stress are not available. The purposes of this study are the development of fundamental design and the development of in-process real-time weld quality evaluation technique by acoustic emission for the bar-to-bar dissimilar friction welding of hydraulic valve spool steels.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
• /
• pp.136-137
• /
• 2014

In this study, fundamental performances of high strength concrete with ERCO has been analysed according to mock-up test. The following results could be made as the conclusion. For the fresh concrete, flowability and air content decreased with the addition of ERCO, and all the specimens satisfied the target range. For the strength properties, all the specimens with different nominal strength showed higher compressive srength than Plain which with 0% dosage of ERCO.

• Journal of Welding and Joining
• /
• 제8권3호
• /
• pp.79-88
• /
• 1990

Welded joint often contains soft or softened regions such as the HAZ of TMCP steel welded with high heat input. In this study, the equivalent yield strength of plate structure containing softened region was predicted by FEM analysis, and its incremental behavior was explained with the results of the analysis. The calculated results of yield strength indicated the following for the plate structures. 1) As the softened region starts to yield, shear stress begins to build up along the boundary between base metal and softened region. This results in multi-axial stress condition which gives restraint on the softened region. 2) Restraint effect has a significant influence on the distribution of the shear stress, the nominal stress, and the strain. 3) The yielding behavior of softened region becomes the same as that of base metal when both ratios of length to width and thickness to width of softened region are larger than 30 and 13 respectively.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
• /
• pp.57-64
• /
• 1998

This paper presents the cyclic seismic performance of slip-critically designed, high-strength bolted-beam splice in steel moment frame. Before the moment connection reaching its plastic strength, unexpected premature slippage occurred at the slip-critically designed beam splice during the test. The experimentally observed frictional coefficients were as low as about 50% to 60% of nominal (code) value. Nevertheless, the bearing type behavior mobilized after the slippage transferred the increasing cyclic loads successfully, i.e., the consequence of slippage into bearing was not catastrophic to the connection behavior. The test result seems to indicate that the traditional beam splice design basing upon (bolt-hole deducted) effective flange area criterion may not be sufficient in developing the plastic strength of moment connections under severe earthquake loading. New procedure for achieving slip-critical beam splice design is proposed based on capacity design concept.