• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.922-927
• /
• 2006

There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. The advantages of fibre reinforced plastic(FRP) composites over conventional materials motivate their use in highway bridges for replacement of structures. Recently, an FRP deck has been installed on a state highway, located in New York State, as an experimental project. In this paper, a systematic approach for analysis of this FRP deck bridge is presented. Multi-step linear numerical analyses have been performed using the finite element method to study the structural behavior and the possible failure mechanism of the FRP deck-superstructure system Deck's self-weight and ply orientations at the interface between steel girders and FRP deck are considered in this study. From this research, the results of the numerical analyses were corroborated with field test results. Analytical results reveal several potential failure mechanism for the FRP deck and truss bridge system The results presented in this study may be used to propose engineering design guideline for new and replacement FRP bridge deck structure.

• Strategy21
• /
• s.36
• /
• pp.150-179
• /
• 2015

This thesis analyzes Somali piracy as a non-traditional threat to the Sea Lines of Communication (SLOC) and international countermeasures to the piracy. In an era of globally interdependent economies, the protection of sea lines and freedom of navigation are prerequisites for the development of states. Since the post-Cold War began in the early 1990s, ocean piracy has emerged as a significant threat to international trade. For instance, in the Malacca Strait which carries 30 percent of the world's trade volume, losses from failed shipping, insurance, plus other subsequent damages were enormous. Until the mid-2000s, navies and coast guards from Malaysia, Indonesia, Singapore, together with the International Maritime Organization (IMO), conducted anti-piracy operations in the Strait of Malacca. The combined efforts of these three maritime states, through information sharing and with reinforced assets including warships and patrol aircrafts, have successfully made a dent to lower incidents of piracy. Likewise, the United Nations' authorization of multinational forces to operate in Somali waters has pushed interdiction efforts including patrol and escort flotilla support. This along with self-reinforced security measures has successfully helped lower piracy from 75 incidents in 2012 to 15 in 2013. As illustrated, Somali piracy is a direct security threat to the international community and the SLOC which calls for global peacekeeping as a countermeasure. Reconstructing the economy and society to support public safety and stability should be the priority solution. Emphasis should be placed on restoring public peace and jurisdiction for control of piracy as a primary countermeasure.

• Steel and Composite Structures
• /
• v.18 no.2
• /
• pp.375-394
• /
• 2015

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck $HP^{(R)}$ steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design.

• Steel and Composite Structures
• /
• v.48 no.5
• /
• pp.565-582
• /
• 2023

The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (>5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift >3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.28 no.1
• /
• pp.41-46
• /
• 2024

The current study investigates the seismic performance of shear-dominant RC columns retrofitted with iron-based shape memory alloy (Fe SMA). Three RC columns with insufficient transverse reinforcement were designed and fabricated for lateral cyclic loading tests. Before testing, two specimens were externally confined with carbon fiber-reinforced polymer (CFRP) sheets and self-prestressed Fe SMA strips. The test results showed that both CFRP and Fe SMA performed well in preventing severe shear failure exhibited by the unretrofitted control specimen. Furthermore, the two retrofitted specimens showed ductile flexural responses up to the drift ratios of ±8%. In terms of damage control, however, the Fe SMA confinement was superior to CFRP confinement in that the spalling of concrete was much less and that the rupture of confinement did not occur.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.3
• /
• pp.65-77
• /
• 2005

This paper investigates the failure mechanism of geosynthetic-reinforced segmental retaining walls with tiered configuration using reduced-scale model tests. The reduced scale model test set-up was established to simulate a 5 m high full-scale wall. The geometry and material properties used in the model test were determined based on the Similitude Laws. The wall failures in the model tests were successfully generated by their self weight without any surface loading and analyzed examining the digital video recordings. The failure mechanisms was examined with respect to the various offsets between the lower and upper teres and the reinforcement length. Based on the results the appropriateness of the current design guideline was discussed.

• International Journal of Highway Engineering
• /
• v.16 no.6
• /
• pp.95-104
• /
• 2014

PURPOSES : The purpose of this study is to evaluate the degree of restraint (DOR) of longitudinal steel at continuously reinforced concrete pavement (CRCP) against environmental loadings. METHODS : To measure the longitudinal steel strain, 3-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10 min. intervals during 259 days. In order to properly analyze the steel strains first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into 12 phases with different events such as before paving, during concrete hardening, and after first cracking, etc. RESULTS : Thermal strain rate (TSR) concept is defined as the linear strain variations with temperature changes and restraints rate of longitudinal steel against environmental loadings (especially thermal loading) with different cases is defined as degree of restraint(DOR). New concept of DOR could be indirect indicator of crack width behaviors of CRCP. CONCLUSIONS : Before paving, DOR of longitudinal steel is almost same at the coefficient of thermal expansion of steel ($12.44m/m/^{\circ}C$) because of no restraint boundary condition. After concrete pouring, DOR is gradually changed into -1 due to concrete stiffness developing with hydration. After first cracking at crack induced area, values of DOR are around -3~-5. The negative DOR stands for the crack width behavior instead of steel strain behavior. During winter season, DOR reached to -5.77 as the highest, but spring this values gradually reduced as -1.7 as the lowest. Based on this observation, we can presume crack width decreased over time within the time frame of this study. This finding is not consistent with the current theory on crack width variations over time, so further study is necessary to identify the causes of crack width reducing. One of the reasons could be related to concrete stress re-distribution and stress relaxation.

• International Journal of Highway Engineering
• /
• v.16 no.6
• /
• pp.59-67
• /
• 2014

PURPOSES : The purpose of this study is to analyse the longitudinal steel strain and stress of continuously reinforced concrete pavement(CRCP) with longitudinal and transverse direction at early age using stress dependent strain analysis method. METHODS : To measure the longitudinal steel strain, 9-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10min. intervals during 30days. In order to properly analyze the steel stress first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into stress dependent strain (elastic strain) and stress independent strain (thermal strain) and then stress dependent strain was applied to stress calculation of longitudinal steels. RESULTS : Steel strains were successfully measured during 30days. To verify the accuracy of temperature compensation process, measured coefficient of thermal expansion(COTE,$11.46{\times}10^{-6}m/m/^{\circ}C$) of longitudinal steel before paving was compared with that of unrestrained steel. Max. steel stress in the transverse direction shows about 266MPa at 23days after placement. CONCLUSIONS : Steel stresses in the longitudinal and transverse direction have been evaluated. In longitudinal direction, steel stress from the crack was rapidly reduced from 183MPa at crack to 18MPa from 600mm apart the crack. From this observation, stress effective length can be identified as within 600mm apart from the crack. In transverse direction, max. stress point was located near the center of pavement width and stress level(266MPa) is about 66% of yield stress of steel.

• Journal of Veterinary Clinics
• /
• v.35 no.4
• /
• pp.137-140
• /
• 2018

A five-month-old toy poodle was referred for treatment of bilateral mandibular fractures. Preoperative skull and dental radiographs showed rostral mandibular fractures and permanent teeth that had not yet erupted. In addition to providing stability for the healing of fractures, it is very important to focus on restoring normal occlusion. The mandibular fractures were repaired using interdental wiring in a dentate area where the deciduous canines and fourth premolars were stable and could be used to anchor the interdental fixation. In the absence of an erupted permanent mandibular first molar, the modified Risdon wiring was performed using the deciduous mandibular fourth premolars as anchor teeth. An intraoral splint was placed on the mandibular teeth using self-curing composite resin. Five months after surgery, the patient had experienced no complications, and the permanent teeth had erupted normally. In this case, which involves a small-breed puppy with deciduous dentition, treatment with a wire-reinforced interdental splint using intact deciduous fourth premolar teeth as anchor teeth can be considered as a suitable method for rostral mandibular fracture restoration.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.4
• /
• pp.417-425
• /
• 2000

This paper describes the application of discretized continuum-type optimality criteria(DCOC) and the development of optimum design program for the reinforced concrete continuous beams with rectangular cross-section. The cost of construction as objective function which includes the costs of concrete, reinforcing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, and steel ratio. The self-weight of the beam is included in the equilibrium equation of the real system. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of reinforced concrete continuous beams are presented to show the applicability and efficiency of the DCOC-based technique.