Clay Naito

Performance and Characterization of Shear Ties for Use in Insulated Precast Concrete Sandwich Wall Panels

Insulated precast concrete sandwich wall panels are commonly used for exterior cladding on building structures. The insulation is sandwiched between exterior and interior concrete layers to reduce the heating and cooling costs for the structure. The panels can be designed as composite, partially composite, or noncomposite. Shear ties are used to achieve these varying degrees of composite action between the interior and exterior concrete layers. A variety of shear ties are available for domestic construction. An experimental study was conducted to assess the relative strength and response of these commercially available ties. Fourteen different shear tie types were examined, the failure modes and responses were quantified, and simplified engineer level multilinear strength curves were developed for each connection. The test results indicate that shear ties used in sandwich wall construction have considerable variation in strength, stiffness, and deformability. The maximum shear strength of the discrete tie...

Procedure for Site Assessment of the Potential for Tsunami Debris Impact

AbstractTsunami debris can place large demands on the structures it impacts. The types of potential debris and impact forces they generate are not well understood, and relatively little consideration is taken for the risk of tsunami debris strikes during structural design. A procedure is outlined to assess the site-specific potential for debris impact and its significance to structures. The procedure involves a categorization of potential debris based on fundamental characteristics. It includes an assessment of the ability and likelihood of debris transport, as constrained by the topography and the constructed environment. Data from aerial surveys and on-ground surveys after the March 2011 Tohoku tsunami are used to demonstrate and validate the considerations proposed for an assessment of debris and its transport. Instances of structural damage found during the site survey and that potentially resulted from debris strikes are reported. These cases are evaluated to correlate the proposed debris categories ...

Hydraulic Experiments on Impact Forces from Tsunami-Driven Debris

AbstractImpact on a column by an idealized 1:5-scale shipping container propelled by tsunami flow was modeled in a large-scale wave flume. Results from hydraulic experiments were compared with corresponding data from in-air impact experiments using the same experimental configuration to assess the hydrodynamic effects on impact force and duration. Experiments were conducted by varying flow conditions, velocity, and nonstructural mass. An aluminum specimen was tested empty and with the addition of nonstructural mass to simulate partially loaded shipping containers. The measured peak impact forces from the longitudinal test in water were observed to have an increase no greater than 17% of the corresponding measured peak impact forces from the longitudinal test in air. The impact duration measured from the in-air test provided a lower bound for the impact duration measured for the in-water tests. Hydraulic effects were shown to increase the impact duration by an average of 20%. The additional nonstructural m...

Full-Scale Experimental Study of Impact Demands Resulting from High Mass, Low Velocity Debris

AbstractTsunamis can generate a considerable amount of flow velocity on land. The associated hydrodynamic effects coupled with the plethora of unrestrained objects and frangible structures produce significant debris that can travel similar velocities as the flow. Design of structures to resist the tsunami-driven debris requires a conservative estimation of the forces generated at impact. To quantify the forces generated, an experimental study was conducted on a full-scale wood utility pole, steel tube, and ISO shipping container subjected to in-air axial impacts. The impact force is found to vary linearly with the impact velocity and the impact duration remains constant for elastic response of the debris. For inelastic axial impact of the debris, the duration of the impact event increases and the impact force demands reach a limit. The results are compared with a simplified method, which is found to provide an accurate estimate of the impact demands. The model presented in this paper is developed for use ...

Application of state-of-the-art in measurement and data analysis techniques for vibration evaluation of a tall building

Recent advancements in sensing and data acquisition technology have made monitoring of structures and infrastructure more affordable and, at the same time, more comprehensive. Examples of such advancements are application of wireless technology for communication, the utilisation of fully automated systems for long-term monitoring and the remote control of the sensing system over Internet. Although each of these technologies has been used in different structural health monitoring projects in the recent years, inclusion of an all-in-one sensing system represents the state-of-the-art in measurement techniques. This paper presents the integration of all of the above-mentioned advanced monitoring approaches in one sensing system for forensic quantification of an in-service tall building. The inclusive measurement and monitoring system along with advanced data analysis techniques enabled extraction of detailed information about dynamic characteristics of the building structure and development of reliable conclusions regarding its performance. It is shown that the performance of the investigated structural components is satisfactory in terms of strength demand. However, the level of vibration in some portions of the structure does not meet the limits of human comfort. In addition, wind-speed spectrum, acceleration response spectrum and the modes of lateral vibration are extracted to assist with evaluation of the structures performance.

Forensic Examination of a Noncomposite Adjacent Precast Prestressed Concrete Box Beam Bridge

On the evening of December 27, 2005 the fascia beam supporting the east side parapet wall of the third span of the Lake View Drive Bridge failed under the action of dead load. To gain insight into the potential causes of the failure a series of forensic analyses were conducted on the beams decommissioned from the bridge. The study correlates external observations of surface condition with internal chloride profile, depth of carbonation, and existing corrosion. The forensic investigation indicated that strand cover was reduced due to the construction methods of the time. The chloride level in the concrete at the lower layer of strands was high enough that corrosion would be expected. Chloride attack was identified to have come from the leakage of water between beams from the bridge deck surface above. Based on the research findings recommendations are made for visual inspection, and guidelines are provided for condition rating of noncomposite prestressed concrete box beam bridges.

Quasi-static, low-velocity impact and ballistic impact behavior of plain weave E-glass/phenolic composites:

Quasi-static, low-velocity impact (LVI) and ballistic impact loading conditions were used to find the material properties and dynamic responses of E-glass/phenolic composites. Standard American Society for Testing and Materials (ASTM) tests were used to find the density, Poisson’s ratio, tensile, compressive and shear strengths, and the elastic and shear moduli of the material. The quasi-static punch shear and crush strength tests were used to find the punch shear and crush strengths of the material. LVI tests were conducted to obtain force versus time curves for various loading conditions. Ballistic testing was conducted using a right circular cylinder (RCC) to find the V50 ballistic limit and the depth of penetration of the RCC at various impact velocities. The experimental results of this investigation can be used for structural design and to validate numerical solutions for both LVI and ballistic impact events.

Anchorage Strength and Behavior of Headed Bars in Exterior Beam-Column Joints

Headed bars can assist in alleviating steel congestion and are commonly used in areas where development hooks or traditional reinforcement development lengths cannot be achieved. In this study, 30 exterior beam-column joint specimens without transverse reinforcement were tested to measure anchorage strength with respect to anchorage configuration and embedment length. The anchorage behavior of bars terminated with a head and with a 90-degree hook was investigated and compared with each other and existing models. Tensile load was directly applied to the bar and the same amount of compressive load was applied to the compressive zone of an idealized beam. Findings show that existing models based on idealized failure modes do not properly predict the concrete contribution to anchorage strength of headed bars terminated in exterior joints. The anchorage strength of the headed bars consisted of a combination of head bearing and bond. A specific model complying with the given condition of the anchorage zone should be used since failure modes of headed bar anchorage are varied with given geometric and material conditions. A new model is proposed that conservatively estimates the anchorage strength of the headed bars terminated within exterior beam-column joints with sufficient side cover.

Integrated Analytical and Experimental Research to Develop a New Seismic Design Methodology for Precast Concrete Diaphragms

AbstractA new seismic diaphragm design methodology has been developed for precast concrete floor diaphragms. The knowledge required to create the design methodology was obtained through an integrated analytical and experimental research project using two Network for Earthquake Engineering Simulation (NEES) equipment sites. The activities of the project involved a sequence of integrated research tasks that systematically developed knowledge about diaphragm behavior from the reinforcement detail level to the structural system level. These tasks included the use of state-of-the-art experimental techniques made possible through the NEES facilities including hybrid simulation and large-scale shake table tests. Such techniques were crucial to the research as the complex behavior of precast diaphragms is not well described by simple analytical models or idealized experiments. Valuable industry oversight in the planning, execution, and technology transfer stages of the project guided the research activities, incl...

Water-Driven Debris Impact Forces on Structures: Experimental and Theoretical Program

Water-driven debris generated during tsunamis and hurricanes can impose substantial impact forces on structures that are often not designed for such loads. This paper presents the design and results of an experimental and theoretical program to quantify these potential impact forces. Two types of prototypical debris are considered: a wood log and a shipping container.Full-scale impact tests at Lehigh University were carried out with a wooden utility pole and a shipping container. The tests were carried out in-air, and were designed to provide baseline, full-scale results. A 1:5 scale shipping container model was used for in-water tests in the Oregon State University large wave flume. These tests were used to quantify the effect of the fluid on the impact forces.Results from both experimental programs are presented and compared with theoretical predictions. The analytical predictions are found to be in sufficient agreement such that they can be used for design. A fundamental takeaway is that the impact forces are dominated by the structural impact, with a secondary affect provided by the fluid. Both forces are quantified in the paper.Copyright