Digital Commons Network^™

Development Of Kansas Guardrail To Bridgerail Transition Designs Using Barrier Vii, Christopher Tuan, Edward Post, Syed Atuallah, J. Brewer

Christopher Y. Tuan

BARRIER VII computer code was used to evaluate the dynamic performance of five Kansas guardrail-to-bridgerail transition designs. The simulation results were compared with those of two FHWA-approved transition designs. The test vehicle model was a 4,500-lb, 1977 Plymouth impacting the barriers at 60 mph with an approach angle of 25 deg. The vehicle-crushing properties and guardrail-post stiffness had been validated using full-scale vehicle crash test data before the simulations were conducted. A methodology for wheel-snagging prediction was also proposed and validated against available test data. It was shown that reliable simulation results could be obtained if the input parameters for …

Review Of Live Loads Due To Human Movements, William Saul, Christopher Tuan

Christopher Y. Tuan

Present U.S. structural engineering practice assumes that live load components due to human occupancy and human movements for the design of assembly structures, such as grandstands, can be represented as statically applied uniform or line loads. A review of code values and procedures reveals a history of theoretical, experimental, empirical, and practical developments and events that provide insight into their sources and meanings. The mechanisms by which they have been implemented should prove to be interesting and informative to the design engineer and others concerned with the modernization of codes. The designer is provided with a perspective of a complex …

Loads Due To Spectator Movements, Christopher Tuan, William Saul

Christopher Y. Tuan

Typical spectator movements were simulated by persons individually on a force platform with which dynamic force components were measured. Impulsive loadings are produced by movements such as rising, sitting, or jumping off the floor, while continuous loadings are generated in repetitive motion such as swaying, bending and straightening knees repetitively in place, jumping or dancing. Descriptive parameters derived from statistical and spectral studies of the load samples are presented. In particular, the vertical components of the impulsive loadings are modeled as random forcing functions, and a narrow‐band live load spectrum is proposed for checking potential resonant response of a structure …

Sympathetic Vibration Due To Co-Ordinated Crowd Jumping, Christopher Y. Tuan

Christopher Y. Tuan

In assembly structures or places where crowds may gather such as dance halls, theaters, gymnasia and stadia, the loading is almost entirely caused by human activities. Structural resonance or near resonance and the resulting vibrations causing discomfort of spectators have often been observed during a rock concert or a sporting event. Recent research efforts have focused on developing load models to quantify the dynamic loading effects induced by individuals and groups up to 40 people. The lack of coherence of motion from a large crowd, the so-called ‘‘group effect’’, has been quantified based on simulations. The simulation results and the …

Progressive Failure Simulation Of Security Cable Barriers, Christopher Tuan, Ratul Sarmah, Alexander Tuan, Ching-Sheng Kao, Q. Li

Christopher Y. Tuan

Perimeter security cable barriers are widely used by various agencies all over the world to defeat threat vehicle penetration. New barrier designs require crash test validation prior to implementation. Full-scale vehicular crash tests are costly, whereas designs via finite element simulations are time consuming and require specialized skills. Based on full-scale crash tests, an innovative and simple algorithm has been developed to model the progressive failure of security cable barriers. A multi-body approach based on the first principles of physics was developed to substantially reduce computer runtime. The solution algorithm uses a large number of small time steps. Nonlinear vehicle …

Conductive Concrete: A Shielding Constructurion Material, A. P. Krause, L. Nguyen, Christopher Y. Tuan, J. D. Blasey

Christopher Y. Tuan

Shielding against electromagnetic phenomenon is an increasingly important consideration on a global scale. Solar storms, privacy from electronic surveillance, and EMP weapons are just a few of the concerns that must be addressed. Current methods of protection are subject to high cost and often limited in scalability. Conductive concrete is a promising solution to both of these limitations. By adding several simple materials to traditional concrete, a new type of constructible electromagnetic shield can be produced. The following will discuss the design and testing of conductive concrete for EM shielding as well as the results of those tests.

Numerical Analysis Of Concrete-Filled Circular Steel Tubes, Yaohua Deng, Terri Norton, Christopher Tuan

Christopher Y. Tuan

Concrete-filled steel tubes have been widely used in building and bridge construction. In this paper, the flexural behaviour of concrete-filled steel tubes is investigated using finite-element analysis and theoretical sectional analysis. The numerical results from both analytical methods are validated against published experimental test results. It is shown that both methods are capable of predicting the elastic and the ultimate moment capacities of concrete-filled steel tubes. Due to its computational efficiency, theoretical sectional analysis is more suitable for the design of concrete-filled steel tubes than finite-element analysis.

Sources Of End Zone Cracking Of Pretensioned Concrete Girders, Christie J. Hasenkamp, Sameh S. Badie, Christopher Y. Tuan, Maher K. Tadros

Christopher Y. Tuan

Recent developments of high performance concrete, increasing amounts of prestressing, and increasing use of deep girders have resulted in increasing popularity of precast pretensioned concrete girders in bridge construction. These developments have increasingly contributed to end zone cracking. This paper summarizes the interim results of an ongoing research sponsored by the National Cooperative Highway Research Program (NCHRP) Project 18-14. The objectives of the research are: (1) to establish procedures for the acceptance, repair, or rejection of precast/prestressed concrete girders with longitudinal web cracking, and (2) to prepare a user's manual for the application of these procedures. The results from a …

Bridge Deck Deicing, Sherif A. Yehia, Christopher Y. Tuan

Christopher Y. Tuan

Concrete bridge decks are prone to ice accumulation. The use of road salts and chemicals for deicing is cost effective but causes damage to concrete and corrosion of reinforcing steel in concrete bridge decks. This problem is a major concern to transportation officials and public works due to rapid degradation of existing concrete pavements and bridge decks. The use of insulation materials for ice control and electric or thermal heating for deicing have been attempted and met limited success. Conductive concrete may be defined as a cementitious composite, which contains a certain amount of electronically conductive components to attain stable …

Ground Shock Resistance Of Mechanically Stabilized Earth Walls, Christopher Tuan

Christopher Y. Tuan

A simple analytical method has been developed that characterizes plane shock wave propagation through reinforced soil and the dynamic interaction between soil and retaining wall panels. The shock wave due to an explosion in the backfill was modeled as a velocity boundary condition at a standoff distance from the wall. The exact solution to this problem was obtained using the Laplace transform method. Full-scale explosive test data from 4.6-m high and 24-m wide reinforced soil walls were used to validate the analytical methodology. The accuracy of the analytical method has further been verified by finite element analysis. The method is …

Airfield Pavement Deicing With Conductive Concrete Overlay, Sherif Yehia, Christopher Tuan

Christopher Y. Tuan

Conductive concrete is a cementitious admixture containing a certain volumetric ratio of electrically conductive materials to attain high and stable electrical conductivity. Due to its electrical resistance, a thin overlay of conductive concrete can generate enough heat to prevent ice formation when energized by AC power. Under a research sponsored by Nebraska Department of Roads, Yehia and Tuan developed a mix specifically for concrete bridge deck deicing while meeting the ASTM and AASHTO strength specifications for overlay construction. An average thermal power of 591 W/m2 (55 W/ft2) with a heating rate of 0.56oC/min (1oF/min) was generated by a 1.2 m …

Implementation Of Conductive Concrete Overlay For Bridge Deck Deicing At Roca, Nebraska, Christopher Y. Tuan, Sherif A. Yehia

Christopher Y. Tuan

Conductive concrete is a relatively new material technology developed to achieve high electrical conductivity and high mechanical strength. In research sponsored by Nebraska Department of Roads, a conductive concrete mix specifically for bridge deck deicing was developed. In this application, a conductive concrete overlay is cast on top of a bridge deck for deicing and anti-icing.

This technology has been successfully implemented in a demonstration project at Roca, about 15 mi south of Lincoln, Nebraska. The Roca Spur Bridge has a 36-m (117-ft) long and 8.5- m (28-ft) wide conductive concrete inlay. Temperature sensors and a microprocessor-based controller system were …

Protective Construction With Reinforced Earth, Christopher Tuan

Christopher Y. Tuan

The objective of this research is to develop a simple analytical method that characterizes plane shock wave propagation through reinforced earth and the dynamic interaction with modular retaining wall panels. The shock wave was initiated as a velocity boundary condition. The exact solution was obtained by the Laplace transform method. A step-by-step design procedure based on the "limit state" concept is proposed. Because of the impulsive nature of ground shock. the maximum response of the wall panel and reinforced soil system depends mainly on the capacity and rate of energy absorption and dissipation of the system. Therefore, the connection between …

Steel Supported Masonry Walls, Lawrence Soltis, Christopher Tuan

Christopher Y. Tuan

Structural steel beams and columns are often used to support masonry walls subjected to transverse and axial loads. Warehouse and gymnasium type buildings often have large floor-to-ceiling heights, such that allowable masonry wall heights are exceeded. Steel framing, tied to the masonry wall by shear connections, tie bars or other devices, works compositely with the wall to resist flexural and compressive loads. Standard design practice considers the steel framing as a plane grid or as simply supported framing providing lateral support to the wall. The lateral load on the contributory wall area is assumed to be transmitted directly to the …

End Zone Reinforcement For Pretensioned Concrete Girders, Christopher Y. Tuan, Sherif A. Yehia, Nipon Jongpitaksseel, Maher K. Tadros

Christopher Y. Tuan

In this study, a literature review was conducted to establish the background of current specifications and to evaluate the applicability of various theories and methods for design of end zone reinforcement. Analytical methods reviewed in this paper include finite element analysis, strut-and-tie modeling, and the Gergely-Sozen equivalent beam method. Previous experimental work combined with work conducted as part of this study was used to correlate between various theoretical and experimental results. This paper illustrates that no single theoretical method adequately represents the complex behavior at the end of a pretensioned concrete member. A general semi-empirical design procedure is proposed here. …

Curved, Precast, Pretensioned Concrete I-Girder Bridges, Wilast Amorn, Christopher Y. Tuan, Maher K. Tadros

Christopher Y. Tuan

Modern highway construction frequently requires bridges with horizontally curved alignments. Such bridges can be created by superimposing a curved deck slab onto straight girders or by splicing segmental straight girders on the chords of a curved roadway. Of these two methods, a curved superstructure usually results in simpler construction and better appearance.

Bond Strength And Transfer Length Of Pre-Tensioned Bridge Girders Cast With Self-Consolidating Concrete, Amgad Girgis, Christopher Tuan

Christopher Y. Tuan

Self-consolidating concrete (SCC) is becoming increasingly popular in the precast/prestressed concrete industry in the United States. However, there have been concerns regarding the bond strength, transfer length, and development length of prestressing strands and mild steel reinforcement with SCC. Further, there are no design guidelines for using SCC. In this study, a literature survey on the bond strength of SCC was conducted. Moustafa pullout tests were performed to determine the bond strength of 0.6 in. (15.2 mm) pretensioning strands with sec. The transfer lengths of three pretensioned concrete bridge girders were measured using Demec points. Pullout tests were also performed …

Drop Weight Testing On Sandwich Panels With A Novel Thermoplastic Core Material, Christopher Y. Tuan

Christopher Y. Tuan

A series of drop weight tests were conducted to evaluate the dynamic flatwise compression strength and flexural strength of sandwich panels with a novel core structure. This sandwich core material, known as Norcore, consists of interconnected cells in a unique configuration of truncated pyramid with sloping cell walls. Core materials made of thermoplastic including virgin Lexan, polycarbonate, polycarbonate regrind, high-impact polystyrene, and acrylonitrile butadiene styrene were tested. The test results showed that these sandwich panels have good strength as well as energy absorption capacities.