Collapse Behavior of an 18-Story Steel Moment Frame during a Shaking Table Test

Suita, Keiichiro,Suzuki, Yoshitaka,Takahashi, Motomi Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.3

A shaking table test was conducted at the E-Defense shaking table facility to investigate the damage and collapse behavior of a steel high-rise building under exceedingly large ground motions. The specimen is a one-third scale 18-story steel moment frame designed and constructed according to design specifications and practices used in the 1980s and 1990s. The shaking table tests used a long-duration, long-period ground motion simulated for a sequential Tokai, Nankai, and Nankai earthquake scenario. The building specimen was subjected to a series of progressively increasing scaled motions until it completely collapsed. The damage to the steel frame began through the yielding of beams along lower stories and column bases of the first story. After several excitations by increasing scaled motions, cracks initiated at the welded moment connections and fractures in the beam flanges spread to the lower stories. As the shear strength of each story decreased, the drifts of lower stories increased and the frame finally collapsed and settled on the supporting frame. From the test, a typical progression of collapse for a tall steel moment frame was obtained, and the hysteretic behavior of steel structural members including deterioration due to local buckling and fracture were observed. The results provide important information for further understanding and an accurate numerical simulation of collapse behavior.

Engineering Properties of Compacted Loesses as Construction Materials

김대현,강성승 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.2

Loess often causes some problems when they are naturally deposited, or when they are used as fill materials in the construction of embankments. In the case of constructing the embankment on a thick, naturally deposited loess layer, the collapsibility, or consolidation will be a critical issue to be considered. In contrast, when a loess is used as a fill material, compactability, stiffness (resilient modulus), and pumping problem induced by repeated traffic loadings should be accounted for. In this study, in order to evaluate the mechanical characteristics of Indiana loess for constructing embankments, the following laboratory tests were conducted on four loesses having different clay contents (10%, 20%, 25%, and 30%): the standard compaction test, the collapse potential test,the CRS consolidation test, the direct shear test, the resilient modulus test, as well as the soil index test. Test results show that the collapsible potential can be significantly improved by well-compacting the loess when it is used as a fill material. Based on the results of collapsible tests on four loesses having different clay contents (10%, 20%, 25%, and 30%), it has been found that the higher the silt content, the higher the collapse potential at the given density corresponding to the naturally-deposited condition. This implies that the amount of silt in Indiana loess is the most influential factor in terms of collapsibility. The results of direct shear tests show that the effect of clay contents does not have much influence on the friction angle and cohesion of the compacted loess materials used in embankments. Unlike the shear behavior, the resilient behavior of compacted loess materials is considerably affected by the clay content such that the loess with the largest silt content shows the lowest resilient modulus due to the pumping-like phenomenon induced by the repeated loading.

고종횡비 비대칭 구조물의 발파붕괴 거동에 관한 연구

송영석 ( Young Suk Song ),정민수 ( Min Su Jung ),정동월 ( Dong Wol Jung ),허원호 ( Won Ho Hur ) 대한화약발파공학회 2013 화약발파 Vol.31 No.1

In blasting demolition, a method would be chosen among many depends on shape and system of a structure and its surround. To demolish using explosives a structure, which is asymmetric and with high aspect ratio, pre-weakening, explosive locations, detonating delay, and surround conditions are needed to be considered in front to design blasting demolition plan. In this study, to over turn asymmetric and high aspect ratio structure in safe, a simulation using a software named Extreme Loadings for Structures, ELS, had performed. In results, it is achieved optimized pre-weakening shapes and locations, which prevent kick back motion of the structure when it collapse, by analyzing moment distribution caused by pre-weakening. And of structural collapse and by minimizing asymmetric structure`s torsional moment. Also, after the demolition, simulation results are also compared with actual collapse behavior. In results, it is confirmed the accuracy of collapse behaviour simulation results, and in blasting demolition, kick back motion can be controled by adjusting pre-weakening shape and location, and the torsional moment of an asymmetric structure also can be solved by optimizing detonation locations and its time intervals.

전도공법에 의한 축소모형 철근콘크리트 구조물의 붕괴거동

박훈(Hoon Park),이희광(Hee-Gwang Lee),유지완(Ji-Wan Yoo),송정언(Jeung-Un Song),김승곤(Seung-Kon Kim) 한국암반공학회 2007 터널과지하공간 Vol.17 No.5

발파해체 되는 철근콘크리트 구조물은 교대하중에 의해 정형구조에서 비정형구조로 변환되며 붕괴거동은 비선형적인 대변위 거동을 한다. 철근콘크리트 구조물의 붕괴거동에 대한 많은 수치 모델링 연구가 수행되었지만, 비선형적인 대변위 거동을 해석하기에는 아직 부족한 수준이다. 본 연구에서는 실제 철근콘크리트 구조물을 1/5로 축소한 축소모형 구조물을 제작하였다. 전도공법으로 1층, 3층, 5층 축소모형 구조물을 발파하여 상부자중에 의한 구조물의 붕괴 가능성을 고찰하였으며, 구조물의 붕괴거동을 X방향(수평방향)의 변위, Y방향(수직방향)의 변위, 상대 변위각으로 분석하였다. 실험결과 자중에 의한 구조물의 붕괴를 유도하기 위한 상부 자중의 크기를 확인할 수 있었다. 또한 구조물의 붕괴에 따른 X방향의 변위와 Z방향의 변위는 발파 후 67ms, 300ms부터 서서히 증가하였고, 교대하중에 의해 3층 구조물의 초기 붕괴 속도가 5층 구조물보다 크게 발생하는 것을 확인하였다. The regular RC structures have been transformed into irregular RC structures by alternate load of RC structures during explosive demolition. Numerical simulation programs have contributed to a better understanding of large displacement collapse behavior during explosive demolition, but there remain a number of problems which need to be solved. In this study, the 1/5 scaled 1, 3 and 5 stories RC structures were designed and fabricated. To consider the collapse possibility of upper dead load, fabricated RC structures were demolished by means of felling method. To observe the collapse behavior of the RC structures during felling, displacement of X-direction (or horizontal), displacement of Z-direction (or vertical) and relative displacement angle from respective RC structures were analyzed. Finally explosive demolition on the scaled RC structures using felling method are carried out, collapse behavior by felling method is affected by upper dead load of scaled RC structures. Displacement of X and Z direction increases gradually to respective 67ms and 300ms after blasting. It is confirmed that initial collapse velocity due to alternate load has a higher 3 stories RC structures than 5 stories.

Collapse Behavior of Reduced-Scale Frames by the Inverted Shaking Table Method under Dynamic Seismic Loading

Yuko Shimada,Kenta Takahashi,Satoshi Yamada 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6

The shaking table test, which is generally conducted using reduced-scale frames to investigate the collapse behavior of structures during underground motion, is an eff ective method in the seismic engineering fi eld. However, unlike the shaking table test with full-scale frames, those with reduced-scale frames possess several problems owing to the scaling eff ect. This paper proposes a novel experimental method for performing the shaking table test with reduced-scale frames to overcome these problems; this method is known as the “inverted shaking table.” Through a series of experiments using this method and two earthquake records as inputs without modifying the time axis, the elastoplastic behaviors of reduced-scale steel frames are obtained up to their collapse owing to the P-Δ eff ect. Additionally, the changes in the collapse process are studied by changing the vertical load on the test specimens. The test results obtained in this study are validated using the response analysis of a single degree-of-freedom system, which reveals that the hysteresis and acceleration multiplier of the input wave obtained using the response analysis and test for each specimen are approximately the same. This indicates that the proposed method is eff ective for reproducing the frame behavior up to collapse for specimens with portable components and using general experimental apparatus.

Collapse Behavior of Single-Layer Space Barrel Vaults under Non-Uniform Support Settlements

M. R. Sheidaii,S. Bayrami,M. Babaei 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.4

Single-layer space barrel vaults are appropriate structures for covering extensive spaces with large spans for which nonuniformsupport settlement is considered as a great concern. This can affect the stability and collapse behavior of thesestructures. Accordingly, in this paper, the collapse behavior of the barrel vaults with different slope angles is investigated undervarious types of the non-uniform support settlement. Both material and geometrical nonlinearity are taken into account whilestudying the effects of the settlements on the collapse progression in barrel vaults. Finally, the optimum slope angles of thestructures are determined so that it minimizes the destructive effects of the support settlement. Moreover, the allowable valuesof the non-uniform support settlements provided by several code provisions have been investigated in detail.

Numerical Procedure for the Three-Dimensional Nonlinear Modelling of Composite Steel–Concrete Beams

Karim Benyahi,Youcef Bouafia,Marc Oudjene,Salma Barboura,Mohand Said Kachi 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.3

Composite steel–concrete structures are commonly used in the fi eld of bridges, where the steel frame provides great ease of installation, and concrete provides useful strength at low cost. This construction system makes it possible to seek to use each material to the best of its ability, so as to provide the entire construction system with greater savings. The purpose of this article is to be able to perform the simulation and the non-linear elastic calculation of composite steel–concrete beams through a calculation approach based on a matrix method of displacements. The numerical calculation model developed is based on taking into account the non-linearity of materials, or a set of laws allowing the modeling of the nonlinear behaviors of materials under an instantaneous and monotonous loading increasing until the ruin; the concrete is represented in its post-elastic part by a softening branch in compression and the contribution of the concrete stretched between two successive cracks is taken into account. Steel is represented by a perfect elastoplastic law or an elastoplastic law with fi rming. The proposed approach has been implemented on the Fortran programming language, where our procedure of numerical modeling of the mechanical behavior seems capable of correctly simulating the three-dimensional nonlinear behavior of isostatic and hyperstatic composite steel–concrete beams, under monotonous (increasing) static loading until ruin. It was validated by comparing the results of our calculations to experimental results or to analytical solutions.

Impact Collapse Behavior of CFRP Structural Members according to the Variation of Section Shapes and Stacking Angles

황우채,양용준,차천석,정종안,김지훈,임광희,김선규,양인영 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

The design of car body structural member aimed to develop members with the optimum impact characteristics to ensure a protectedspace for passengers in the case of automobile collisions. Accordingly, these members were fabricated to provide sufficient rigidityand safety to the passenger room structure and to absorb large amounts of energy during collision. CFRP(Carbon Fiber ReinforcedPlastics) of the advanced composite materials as structure materials for vehicles, has a widely application in lightweight structuralmaterials of air planes, ships and automobiles because of high strength and stiffness. In this study, impact collapse characteristicsand collapse modes were quantitatively analyzed according to the changes in section shape(square, single and double-hat shapedsection) and stacking angles([+15°/-15°]4,[+45°/-45°]4, and [90°/0°]4). This analysis was performed to obtain design data that canbe applied in the development of optimum lightweight members for automobiles.

Ultimate behavior of composite beams with shallow I-sections

Selçuk Emre Görkem,Metin Hüsem 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.5

Bending behavior of reinforced concrete slabs encased over shallow I-sections at different levels of compression heads were investigated in present study. 1500 mm long I-sections were used to create composite slabs. Compression heads of monolithic experimental members were encased at different levels into the concrete slabs. Shear connections were welded over some of the I-sections. The testing was carried out in accordance with the principles of four-point loading. Results revealed decreasing load bearing and deflection capacities of composite beams with increasing encasement depths into concrete. Mechanical properties of concrete and reinforcing steel were also examined. Resultant stresses calculated for composite beams at failure were found to be less than the yield strength of steel beams. Test results were discussed with regard to shear and slip effect.

감육 엘보우의 붕괴거동에 미치는 굽힘각의 영향

김진원(Jin-Weon Kim),나연수(Yeon-Soo Na) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The purpose of this study is to investigate the effect of bend angle on the collapse behavior of locally wall thinned elbows. For this purpose, the present study performs three-dimensional finite element analysis on the 30-, 60-, and 90-degree elbows with local wall thinning at intrados, extrados, and crown, and evaluates the collapse moment under various thinning shapes and loading conditions. Combined internal pressure and in-plane bending load are considered. The results showed that the reduction in collapse moment by local wall thinning increases with decrease in bend angle of elbow. This tendency was more significant for a wall thinned elbow with higher bend radius under opening mode bending with internal pressure, and the effect of bend angle increased with increasing depth, length, and circumferential angle of wall thinning.