"Estimation of the flexural moment capacity of externally prestressed concrete members considering internal indeterminacy"

  The approximate empirical formula which is adopted to internally prestressed concrete beams calculation procedure to calculate the flexural strength of externally prestressed concrete members considering internal indeterminacy. By nonlinear analysis, material analysis can be applied. A test is carried out to clarify the theoretical background with two specimens, one is a prestressed concrete composite beam with internal bonded prestressed reinforcements and the other is prestressed concrete composite same properties in material and geometrical conditions, except having externally unbonded prestressed reinforcements. The comparison of test results in flexural strength, deflection, tendon stress with our proposal, some design specification, and empirical formulas are carried out. Our proposal shows good agreement with test results both in strength and deflection. Since this procedure can be applied for the externally prestressed concrete with various tendon profile and structural system, it can be used as a general method of strength calculation.

"An examination of applying the design provisions of punching shear strength for the multi-girder bridge deck slabs"

  Since a design provision of punching shear strength is induced from the flat slab's test data, which have different stress state from the punching failure state of multi-girder bridge deck slab by wheel loads, it is questioned whether the design provisions can be used for the bridge deck. We compare the test data of flat slabs and bridge deck slabs with punching two times larger scatter compared with that of flat slab. We find that the scatter comes from the effective depth d and shear span ratio a/d, where the former is related with size effect and the latter with restraint effect. Since the test data of small scale model test of bridge deck, which have very small slab depth, show large scatter, we can conclude it inappropriate to use the test data for the estimation of punching shear strength of bridge deck. On the contrary, the test data of prototype bridge deck model show almost the same scatter as flat slab's, the design provisions can be used for bridge deck design.

"A study on improving the design of hybrid stress-ribbon bridges and their aerodynamic stability"

  Preliminary designs were for the proposals for the 'stress-ribbon cable-stayed suspension' and the 'stress-ribbon suspension' bridges with an open-grating deck plate for pedestrian use. The findings of this study revealed the followings: That the horizontal component of tensile force in the cables can be reduced up to 1/23 of the conventional concrete stress-ribbon bridges; the maximum deflection of the girder under asymmetrical live load can be well controlled by installing central clamps; the critical flutter speed is sufficiently high; and  that vortex-induced oscillation does net occur. The application of the proposals for hybrid structures to vehicle bridges was also examined.

"A construction aspect on the hybrid stress ribbon highway bridges"

  Based on the previous proposals of 'hybrid stress-ribbon suspension' bridge, some terms of the problems related with construction. Among them, the end anchorage system for horizontal forces, static and dynamic problems during construction, temperature change and cable connection related problems are included. Because of a reduced horizontal anchorage force, the steel stress ribbon - suspension pedestrian bridge can resist without needs of rock anchor. Effect of temperature changes of two cable system of elementary case is presented. The cable connection related problems are pointed out. Further discussion needs for highway bridge application is recommended.

"Load-Strain response of reinforced concrete plate member under service load state"

  This paper proposes a mechanical model to describe the load-strain response of the reinforced concrete plate member in the orthogonal reinforcement with arbitrary direction under service load state. An analytical method is introduced on the basis of the rotating crack model which considers equilibrium, compatibility conditions, load-strain relationship of cracked member, and constitutive law for materials. The tension stiffening effect in reinforced concrete structures is taken into account by the average tensile stress-strain relationship from the load-strain relationship for the cracked member and the constitutive law for material. The strain compatibility is used to find out the crack direction because the crack direction is an unknown variable in the equilibrium and compatibility conditions. The p개posed theory is verified by the numerous experimental data such as the crack direction, load-steel strain relationship. The present paper can provide some basis for the provision of the definition of serviceability for plate structures of which reinforcements are deviated from the principal loads, because the present code defines the serviceability for the skeletal members. The proposed theory is applicable to predict the responses of service load state for a variety of reinforced concrete plate structures such as skew slab bridge, the upper and lower flange of curved box girder brides and the deck of skew girder bridge.