• Computers and Concrete
• /
• v.24 no.5
• /
• pp.423-436
• /
• 2019

Design equations to evaluate the bursting force in a post-tensioned anchorage zone have been introduced in many design codes, and one equation in AASHTO LRFD is widely used. However, this equation may not determine the bursting force exactly because it was designed on the basis of two-dimensional numerical analyses without considering various design parameters such as the duct hole and shape of the bearing plate. To improve the design equation, modification of the AASHTO LRFD design equation was considered. The behavior of the anchorage zone was investigated using three-dimensional linear elastic finite element analysis with design parameters such as bearing plate size and diameter of sheath hole. Upon the suggestion of a modified design equation for evaluating the bursting force in an anchorage block with a rectangular anchorage plate (Kim and Kwak 2018), additional influences of design parameters that could affect the evaluation of bursting force were investigated. An improved equation was introduced for determining the bursting force in an anchorage block with a circular anchorage plate, using the same procedure introduced in the design equation for an anchorage block with a rectangular anchorage plate. The validity of the introduced design equation was confirmed by comparison with AASHTO LRFD.

• Structural Engineering and Mechanics
• /
• v.68 no.5
• /
• pp.621-632
• /
• 2018

Soft-story buildings have bottom stories much less rigid than the top stories and are susceptible to earthquake damage. Therefore, the seismic design specifications need strict design considerations in such cases. In this paper, a four-story building was investigated as a case study and the effects of X-braces elimination in its lower stories studied. In addition, the possibility of replacement of the X-braces in soft-stories with equivalent moment resisting frame inspected in two different phases. In first phase, the stiffness of X-braces and equivalent moment-resisting frames evaluated using classic equations. In final phase, diagonals removed from the lowest story to develop a soft-story and replaced with moment resisting frames. Then, the seismic stiffness variation of moment-resisting frame evaluated using nonlinear static and dynamic analyses. The results show that substitution of braced frames with an equivalent moment-resisting frame of the same stiffness increases story drift and reduces energy absorption capacity. However, it is enough to consider the needs of building codes, even using equivalent moment resisting frame instead of X-Braces, to avoid soft-story stiffness irregularity in seismic design of buildings. Besides, soft-story development in the second story may be more critical under strong ground excitations, because of interaction of adjacent stories.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.11
• /
• pp.64-69
• /
• 2020

To determine the effective factors for microparticle blasting with precise sequence position control in the x-axis and y-axis directions, we conducted a statistical experimental analysis of blasted square shapes by considering five condition factors. The control input and output were operated simultaneously by rotation-linear motion conversion and fine particles were blasted onto the aluminum specimen by precise position control driving using multiple execution codes. The micro-driving device used for processing was capable of microparticle blasting and of controlling the system through contact with a limit sensor at high speed and a two-degree-of-freedom driving mechanism. Our experiments were conducted on 1,050 specimens of pure aluminum (containing <1% of other elements). The effects of several factors (e.g., particle and nozzle diameters, blasting pressure, and federate and blasting cycle numbers) on the surface roughness and blasted surface's depth were verified through a statistical experimental analysis by applying the dispersion analysis method. This statistical analysis revealed that the nozzle diameter, the blasting pressure, and the blasting cycle number were the dominant factors.

• Journal of KIBIM
• /
• v.11 no.4
• /
• pp.42-52
• /
• 2021

Paneling building facades is one of the essential procedures in building construction. Traditionally, it has been an easy task of simply projecting paneling patterns drawn in drawing boards onto 3d building facades. However, as many organic or curved building shapes are designed and constructed in modern architectural practices, the traditional one-to-one projection is becoming obsolete for the building types of the kind. That is primarily because of the geometrical discrepancies between 2d drawing boards and 3d curved building surfaces. In addition, curved compound surfaces are often utilized to accommodate the complicated spatial programs, building codes, and zoning regulations or to achieve harmonious geometrical relationships with neighboring buildings in highly developed urban contexts. The use of the compound surface apparently makes the traditional paneling pattern projection more challenging. Various mapping technics have been introduced to deal with the inabilities of the projection methods for curved facades. The mapping methods translate geometries on a 2d surface into a 3d building façade at the same topological locations rather than relying on Euclidean or Affine projection. However, due to the intrinsic differences of the planar 2d and curved 3d surfaces, the mapping often comes with noticeable distortions of the paneling patterns. Thus, this paper proposes a practical method of drawing paneling patterns directly on a curved compound surface utilizing Geodesic, which is faithful to any curved surface, to minimize unnecessary distortions.

• Journal of the Korea Concrete Institute
• /
• v.21 no.4
• /
• pp.401-408
• /
• 2009

A compression lap splice becomes an important issue due to development of ultra-high strength concrete. Current design codes regarding compression lap splice do not utilize merits of the improved strength of ultra-high strength concrete. Especially, a compression lap splice can be calculated longer than a tension lap splice according to the codes because they do not consider effects of compressive strength of concrete and transverse reinforcement. This anomaly confuses engineers in practice. Design equation is proposed for compression lap splice in 40 to 70 MPa of compressive strength of concrete. The proposed equation is based on 51 specimens conducted by authors. Basic form of the equation includes main parameters which are derived from investigating test results. Through two-variable non-linear regression analysis of measured splice strengths, a strength equation of compression lap splices is then derived. A specified splice strength is defined using a 5% fractile coefficient and a lap length equation is constructed. By the proposed equation, the anomaly of lap lengths in tension and compression is got rid of. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.4
• /
• pp.15-22
• /
• 2003

Seismic design codes developed taking into account the strong earthquakes may result in unnecessary economical loss in the low seismic area, and the importance of the performance based design considering the soil-structure interaction is recognized for the reasonable seismic design. In this study. elastic and inelastic seismic response analyses of a single degree of freedom system on the soft soil layer were performed considering the nonlinearity of the soil for the 1 weak earthquakes scaled to the nominal peak accelerations of 0.07g and 0.11g. The seismic response analyses were performed in one step applying the earthquake motions to the bedrock, utilizing a pseudo 3-D dynamic analysis software of the soil-structure system. The study results indicated that seismic response spectra of a system assuming the rigid base or the linear soil layer does not represent the true behavior of a structure-soil system, and it is necessary to take into account the nonlinear soil-structure interaction effects and to perform the performance based seismic design for the various soil layers, having different characteristics, rather than to follow the routine design procedures specified in the design codes for the reasonable seismic design. The nonlinearity of the soft soil excited with the weak seismic motions also affected significantly on the elastic and inelastic seismic response spectra of a system due to the nonlinear soil amplification of the earthquake motions, and it was pronounced especially for the elastic response spectra.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.5A
• /
• pp.443-462
• /
• 2010

The strut-tie model approach has proven to be effective in the ultimate analysis and design of structural concrete with disturbed regions. For the reliable analysis and design by the approach, however, the effective strength of concrete struts must be determined accurately. In this study, the validity of the effective strength of concrete struts, presented by the several design codes and many researchers including the author, was examined through the ultimate strength analysis of 24 reinforced concrete panels, 275 reinforced concrete deep beams, and 218 reinforced concrete corbels by using the conventional linear strut-tie model approach of current codes. The present study shows that the author's approach, resulting in an accurate and consistent evaluation of the ultimate strength of the panels, deep beams, and corbels, may reflect rationally the effects of primary variables including the types of strut-tie model and structural concrete, the conditions of load and geometry, and the strength of concrete in the strut-tie model analysis and design of structural concrete.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.1
• /
• pp.25-34
• /
• 2009

RC flat plate, which has no large flexural stiffness by boundary beams, may be governed by serviceability as well as strength condition. A construction sequence and its impact on distributions of construction loads among slabs tied by shores are decisive factors on immediate and long term performances of flat plate. The over-loading and tensile cracking in early-aged slabs significantly increase the deflection of flat plate system. In this study, for slab deflections, the practical analysis scheme using a linear analysis program is formulated with considering construction sequence and concrete cracking effects. The concept of the effective moment of inertia in calculating deflections of one-way bending member, that is presented in structural design codes, is extended to the finite element analysis of the two-way slab system of flat plates. Effects of over-loads during construction on deflections of flat plate system are analyzed by applying the proposed practical analysis scheme into the critical construction load conditions calculated from the simplified method.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.1
• /
• pp.55-60
• /
• 2011

In the present work, isogeometric analysis in linear elasticity problem is conducted using the basis functions from NURBS. The objectives of isogeometric analysis introduced is to integrate both geometric modeling(CAD) and computational analysis(CAE), and this can be accomplished from direct usage of geometric modeling by NURBS as the computational mesh. The merit of the isogeometry analysis is that NURBS surface are able to represent exact geometry from the control points and knot vectors, and also subsequent refinement is relatively simple relatively. In order to verify the computer codes developed in this study, it has been applied to two structural models of which geometry are simple ; 1) circular cylinder subjected to the constant internal pressure loading, 2) square plate with circular hole at center subjected to uniform tension. The exact solutions of these two models are available. Convergence of the approximate solutions by the present code for the isogeometry analysis are investigated by mesh refinement with inserting knots (h-refinement) and by mesh refinement with order elevation of the basis functions (p-refinement).

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.7
• /
• pp.601-608
• /
• 2015

The static aeroelastic analysis and optimization of flexible wings are conducted for steady state conditions while both aerodynamic and structural parameters can be used as optimization variables. The system of multidisciplinary design optimization as a robust methodology to couple commercial codes for a static aeroelastic optimization purpose to yield a convenient adaptation to engineering applications is developed. Aspect ratio, taper ratio, sweepback angle are chosen as optimization variables and the skin thickness of the wing. The real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was used to control the optimization process. The support vector regression(SVR) is applied for optimization, in order to reduce the time of computation. For this multi-objective design optimization problem, numerical results show that several useful Pareto optimal designs exist for the flexible wing.