A system identification technique by modal data is simple in principle and adequate for the damage assessment of infrastructures such as bridges, where the dynamic force is difficult to be applied. However, since the localized damage of a structure greatly affects higher modes, for an accurate damage assessment, the inclusion of higher modes is essential. In that case, the increased number of constraints and their nonlinearity may cause inefficient optimization. to overcome these difficulties, sensitivity analysis for modal data is performed. Through sensitivity analysis, constraints for some degree of freedom and vibration mode that have high sensitivity for damage are selected, MFD(modified method of feasible direction) optimization technique is applied. Damage Assessment has performed various case as varing the number of vibration modes, elements and damage properties. And its effects on accuracy of damage assessment are analyzed. As a result, sensitivity analysis for modal data improves the efficiency of optimization, and results in exact estimation for damage location and extent.

In this paper, a versatile flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. This element possesses six degrees-of-freedom (DOF) per node which permit an easy connection to other types of finite elements with six DOF per node and improve the element behavior as well. Particularly the new element is useful for the analyses of folded plate structure. In plate bending part, an improved Mindlin plate element has been established by the combined use of the addition of non-conforming modes and the substitute shear strain fields. In membrane part, the non-conforming displacement modes are added to the displacement fields to improve the basic behavior of membrane element with drilling DOF. The flat shell element proposed in this study passes the patch tests, does not show any spurious mechanism, and does not produce shear locking phenomena. This element yielded reliable solutions even for the distorted meshes for some selected benchmark problems.

In designing the PSC box-girder bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of the time-dependent characteristics. In this study, the creep test was carried out for four curing ages of concrete which were applied to the prestressed concrete structure at a construction site, and the results of test were compared to the values of creep prediction by the design code. Also the creep test of step-wise incremental stresses were performed and were compared to analytical models.

The eigenvalue analysis for the nonproportionally damped system should be necessarily performed in case of the soil-structure interaction problem and the structural control problem. However, the most eigenvalue analysis methods such as the subspace iteration method and the Lanczos method may miss some eigenpairs in the required ones. Therefore, the eigenvalue analysis method must include a technique to check the missed eigenpairs for the practical tools. In case of the undamped or proportionally damped structures, the missed eigenpairs can be checked by using the Sturm sequence property, while in case of the nonproportionally damped structures, a checking technique has not been developed yet. In this paper, the mathematical properties such as the extension of the Sturm sequence property, the Routh-Hurwitz criterion and the argument principle have been first reviewed thoroughly, and then the technique that can check the missed eigenpairs in case of the nonproportionally damped structures by applying the argument principle is proposed. To show the effectiveness of the proposed method, a numerical example is considered.

In high tension bolted joints, the corrosion of bolts reduces the clamping force, which causes the reduction of slip resistance. of the joints; and become the cause of disfiguring the scenery due to paint films off. Therefore, in order to prevent the corrosion of high-tension bolted joints and satisfy the mechanical characteristics, the need of coated bolt is being discussed, not only on the faying surface. In this study, relaxation and static tension tests on coated joints have been performed to evaluate the reduction of clamping force and the slip coefficient. The results of relaxation test prove that there are not any significant differences with the coated and non-coated cases and both does not exceed 10%, which agrees with the specification criteria. Also, the slip coefficient of the joints exceeded 0.4, therefore joints using coated bolt have similar quality compared to the non-coated bolt joints.

Dam concrete should have sufficient durability in wet and dry repetition, fatigue resistance and abrasion due to water-level variance and also in freezing and thawing resistance as well as water repellence capacity. This study presents various experimental performance to enhance the durability of face slab concrete in concrete faced rockfill dam by varying the fly-ash substitution of 0%, 10%, 15% and 20% in cement quantity. The effect on durability corresponding to the increasing amount of fly-ash was evaluated and the optimum quantity of fly-ash substitution was finally recommended. The results show that 15% fly-ash substitution was turned out to be an optimum quantity and demonstrated an excellent performances in durability.

A two-dimensional Lagrangian finite-difference computer program is developed for the wave propagation analysis of the impact phenomena. The numerical scheme is the standard method originally proposed by Von Neuman and Ritchtmyer, using artificial viscosity to smooth shock fronts. A test configuration consisted of a target and a projectile were calculated with the various speed, the width, and the length of the projectiles to find the characteristics of the impact load at the interface. Also a damage criterion for the structures was established with the impact loads characterized by the peak-load and the impulse, area under the load-time curve. Among several possible failure modes during the impact process the spatting mode due to the tensile stresses developed in the target is chosen to be the failure mode in this study to show that the peak-load and the impulse are the potential variables to establish the damage criteria for the structures.

In This paper, an efficient analysis method is presented for design of suspension bridges. The suggested approach can satisfy the design conditions for the initial equilibrium state (such as sag of the main cable and camber of the stiffening girder) without any nonlinear iterations, hence it can lead to efficient design processes for suspension bridges. Example analyses are performed for the Namhae and Yong-Jong suspension bridges to verify the applicability of the present method.

The main objective of this study is to develop the rational mix design system of high-strength concrete which is adjusted in the domestic circumstances. For this purpose; 1) Collect a lot of data in order to introduce the relationship between the material variables which influence the properties of high-strength concrete and the multi-variate statistical analysis was done by using computer program Statistical Analysis System (SAS). 2) Select the important material variables for mix design of high-strength concrete by major component analysis and propose the standard range of each material variables. As the results, it was proposed the proper range of material variables, which are water-combine rate, fine aggregate ratio, air content, and dosage of admixture, etc., at the target strength of for Plain and Flyash concrete. And the relationship between the different variables are formulated into equations. A computer program was developed for proportioning the different ingredients of concrete using the derived equations.

The thermal loading due to temperature gradient along with the cross section in the box girder bridge is generally known as the major cause of longitudinal crack. The temperature gradient in the cross section is resulted from the complex heat exchange phenomena between the structure and surrounding environment. For more precise thermal analysis of prestressed concrete box girder bridges, it is necessary to model the solar beam insolation, the time of sunset and sunrise and the length of overhanging shade, etc. varying during the year round. In this paper, the factors affecting thermal response of prestressed concrete box girder bridge are investigated. The finite element code BTAP(Bridge Thermal Analysis Program) is developed on the basis of the theoretical background described in this paper. Parametric study is performed in order to find temperature distribution developed in the bridge cross section under various thermal coefficient values. The validation of BTAP is tested through the comparison of the observed data and analytical thermal responses.

Recently, the externally prestressed unbonded concrete bridges are increasingly built. The mechanical behavior of prestressed concrete beams with external unbonded tendon is different from that of normal bonded PSC beams in that the slip of tendons at deviators and the change of tendon eccentricity occurs as external loads are applied in external unbonded PSC beams. The purpose of the present paper is therefore to devise a realistic analysis method which can describe such behavior in external unbonded prestressed concrete bridges. The slip phenomena and change of eccentricity of tendons have been considered in the model formulation. The layered beam element has been introduced to include the nonlinear behavior of prestressed concrete beams. The proposed analytical model was proved through the comparison of other experimental test data. The PSC beam with unbonded tendon was explored by using the proposed formulation according to tendon profiles and number of deviators. The load-deflection behavior of external unbonded PSC beam is similar to that of internal bonded beam at initial elastic state. However, after cracking, the deflection was remarkably increased in the case of external unbonded beam due to the effect of eccentricity change and slip at deviators. The nominal moment strength decreases remarkably in the external unbonded beam when the deviator is not present at the maximum moment section. This paper will be efficiently used on the analysis of PSC bridges with external unbonded tendons.

Since it is impossible to explain the development of plastic zone near a crack tip by LEFM approach, the best available solution to predict the fatigue life of structural steels is the implementation of EPFM approach based on the principles and techniques of elasto plastic fracture mechanics. To predict the fatigue life, the conventional Paris law has been modified by substituting the range of J-value denoted by that is calculated by J-integral method. The proposed p-version finite element model is formulated by the incremental theory of plasticity that consists of the constitutive equation for elastic-perfectly plastic materials, Tresca/von-Mises yield criteria, and associated flow rule. The experimental fatigue test is conducted with five CCP (Center Cracked Panels) specimens to validate the accuracy of the p-version finite element model. Also, the results obtained by LEFM approach has been compared with those by EPFM approach. It is noted that the relationship between the crack length a and in LEFM analysis shows a strong linearity, on the other hand, the nonlinear relationship between a and is detected in EPFM analysis. Therefore, this trend will be deepened especially in the case of large scale yielding problems.

Plastic shrinkage cracking occurs at the exposed surfaces of freshly placed concrete due to consolidation of the concrete mass and rapid evaporation of water from the surface. This leads to the tensile stress and concrete surfaces may crack. This so-called shrinkage cracking is a major concern for concrete, especially for flat structural such as highway pavement, slabs for industrial factories and walls. One of the methods to reduce the adverse effects of shrinkage cracking is to reinforce concrete with randomly distributed fibers. The contribution of polypropylene fiber to the plastic shrinkage crack reduction potential of concrete and its evaluation are presented in this paper. Results indicated that polypropylene fiber reinforcement showed an ability to reduce the total crack area and maximum crack width significantly (as compared to plain concrete). The durability of polypropylene fiber reinforced concrete was also evaluated. Two types of test were used; chloride permeability and wetting-drying cycle. The chloride permeability test results showed that the addition of the polypropylene fiber reduced the permeability. Wetting-drying tests were performed to study the aging behavior of polypropylene fiber reinforced concrete. Compressive strength tests were performed on unaged (0 cycle) and aged concrete subjected to 25 cycles of wetting-drying. Results showed that after subjected to repeated wetting-drying cycling, the improvement compressive strength of polypropylene fiber reinforced concrete and plain concrete was observed.

In this study, a series of static and fatigue loading tests was conducted on a composite bridge constructed using full depth precast Panels. The model bridge consisted of 7 precast panels on two stringers. Each panel consisted of six· pocket holes to allow room for stud shear connectors and has a groove at both transverse sides to form a shear key joint between two adjacent panels. The pocket holes and the shear key joints were filed with nonshrink-mortar. A series of static loads was applied, along with 2 million cycles of fatigue loading. A water pool was provided at the transverse joint to check for water leakage during the fatigue loading. The results indicate that the performance of the transverse joints meets all requirements for a precast concrete bridge deck system, including serviceability, ability to transfer loads, and no water leakage.

In recent, an unfaithfull construction brings about many social problems. The bidding process considering bidding price firstly is one of the reasons raising an unfaithfull construction work. Thus, we should consider many other criteria including bidding price in the bidder selection process. This paper suggests an analytic hierarchy process (AHP) model for selecting the best bidder of a large construction project. A questionnaire was used to obtain domain experts' opinion about criteria to be considered in the bidding process. A hierarchical structure of the AHP model is formed using criteria obtained in the survey. The relative importance of bidders are judged by pairwise comparison or absolute measurement. An illustrative example is given to show the process selecting the best bidder using the suggested AHP model.

Recently construction industry involves more risks occurred with increasing in size and complexity of construction projects. Risk has been recognized as one of the most serious problems through the construction performance control. Successful performance of construction projects depends on managing and estimating of exact construction cost, but most of contractors have failed to systematically identify and evaluate the effect of internal and external risk elements related with construction projects. Also they don't have any methods or procedures to quantify the impact of risk on project time and cost. Therefore this study suggests a contingency estimating model to quantify the risks by using influence diagram, decision tree, and Monte Carlo simulation. The adequacy of proposed model are verified through case study.

Recently, the Government published the legal basis of construction CALS for improving the applicability in the construction industry. Construction CALS is expected to greatly improve the efficiency of cost, time and quality management in construction project. This study was performed as a basic study to connect construction CALS with CM. In this study the construction CALS was defined by the general CALS concept and connected with the CM processes. Management information system(MIS) for the construction phase was organized with AS-IS and TO-BE formats by IDEF0 method. Each construction process to connect with CM under CALS environment consisted of input, output, control, and mechanism systems based on CALS standards. The MIS between construction CALS and CM was classified by the standard documents, specifications and construction supervision regulations. A prototype of CALS system for the construction phase was developed to be used on the web page through the Internet.