Entity

Time filter

Source Type

Carlsbad, CA, United States

Curtis K.,Hampton Roads Sanitation District | Michael Trapp J.,Michael Baker International
Archives of Environmental Contamination and Toxicology | Year: 2016

It is widely understood that stormwater drainage has a significant impact on the health of tidal creek systems via regular inputs of runoff from the surrounding watershed. Due to this hydrologic connection, contamination of the upstream drainage basin will have a direct effect on estuaries and tidal creeks that often act as receiving waters. This study focuses on the importance of drainage basin sediments as they enhance the persistence and transport of the fecal indicator bacteria E. coli within a watershed. Experiments presented use microcosm environments with drainage basin sediments and stormwater to investigate E. coli colonization of stagnant waters and to examine the importance of host sources to bacterial survival. A novel method for establishing microcosms using environmental sediments with in situ bacterial populations and sterile overlying waters is used to examine E. coli colonization of the water column in the absence of flow. Colonization of sterile sediment environments also is examined using two common host sources (human and avian). Each experiment uses sediments of varying grain size and organic content to examine the influence of physical characteristics on bacterial prevalence. Results suggest host source of bacteria may be more important to initial bacterial colonization while physical characteristics of drainage basin sediments better explains extended E. coli persistence. Findings also suggest an indirect control of water column bacterial concentration by sediment type and erodibility. © 2016 Springer Science+Business Media New York Source


Brown D.N.,Michael Baker International | Parks J.E.,University of Utah | Ameli M.J.,University of Utah | Pantelides C.P.,University of Utah
Composite Structures | Year: 2016

Strut-and-tie models (STM) have been developed for original and repaired precast reinforced concrete (RC) bridge assemblies tested under quasi-static cyclic loads. The original assemblies, built using accelerated bridge construction techniques, are half-scale column-to-footing and column-to-pier cap specimens connected using grouted splice sleeves. The repaired assemblies are strengthened over the plastic hinge region using a unidirectional carbon fiber reinforced polymer (CFRP) shell, post-installed headed steel bars, and non-shrink concrete. The repair technique was successful and the load and displacement capacities of the damaged assemblies were restored. Generic modeling parameters are established for the STM procedure, enabling the models to be adapted to new repair applications. Special attention is focused on the struts within the CFRP shell. All assemblies are modeled using sectional analysis in conjunction with the predicted STM load to estimate a bilinear force-displacement response. The STM and bilinear force-displacement response envelopes obtained from the models show satisfactory agreement with the experiments of the original and repaired bridge assemblies in terms of initial stiffness, lateral load and displacement capacity. © 2015 Elsevier Ltd. Source


Kreisberg D.,Aurora University | Thomas D.S.K.,University of Colorado at Denver | Valley M.,Colorado State University | Newell S.,VA Eastern Colorado Health Care System | And 2 more authors.
Prehospital and Disaster Medicine | Year: 2016

Introduction As attention to emergency preparedness becomes a critical element of health care facility operations planning, efforts to recognize and integrate the needs of vulnerable populations in a comprehensive manner have lagged. This not only results in decreased levels of equitable service, but also affects the functioning of the health care system in disasters. While this report emphasizes the United States context, the concepts and approaches apply beyond this setting. Objective This report: (1) describes a conceptual framework that provides a model for the inclusion of vulnerable populations into integrated health care and public health preparedness; and (2) applies this model to a pilot study. Methods The framework is derived from literature, hospital regulatory policy, and health care standards, laying out the communication and relational interfaces that must occur at the systems, organizational, and community levels for a successful multi-level health care systems response that is inclusive of diverse populations explicitly. The pilot study illustrates the application of key elements of the framework, using a four-pronged approach that incorporates both quantitative and qualitative methods for deriving information that can inform hospital and health facility preparedness planning. Conclusions The conceptual framework and model, applied to a pilot project, guide expanded work that ultimately can result in methodologically robust approaches to comprehensively incorporating vulnerable populations into the fabric of hospital disaster preparedness at levels from local to national, thus supporting best practices for a community resilience approach to disaster preparedness. © World Association for Disaster and Emergency Medicine 2016. Source


Ameli M.J.,University of Utah | Parks J.E.,University of Utah | Brown D.N.,Michael Baker International | Pantelides C.P.,University of Utah
PCI Journal | Year: 2015

Connections between precast concrete elements must be able to withstand significant stresses and deformations in earthquakes. The grouted splice sleeve connector is being considered for use in accelerated bridge construction. Although grouted splice sleeve connectors facilitate the construction of precast concrete bridges and accelerate construction, seismic bridge design codes prohibit their use in column plastic hinges. Half-scale bridge column-to-cap beam assemblies were tested to investigate their response under cyclic quasi-static load. The grouted splice sleeve connectors were located in the column plastic hinge zone for the first alternative and in the cap beam for the second. A monolithic cast-in-place concrete specimen with identical details served as a control. Satisfactory drift capacity and displacement ductility were achieved when the grouted splice sleeve connectors were inside the cap beam joint. The research shows that precast concrete joints constructed with the specific type of grouted splice sleeve connectors in the cap beam should perform adequately in moderate to high seismic regions. Source


Parks J.E.,University of Utah | Brown D.N.,Michael Baker International | Ameli M.J.,University of Utah | Pantelides C.P.,University of Utah
ACI Structural Journal | Year: 2016

A repair technique for severely damaged precast reinforced concrete (RC) bridge columns with grouted splice sleeve (GSS) connections has been developed that uses a carbon fiber-reinforced polymer (CFRP) shell and epoxy-anchored headed bars to relocate the column plastic hinge. Four original specimens were built using an accelerated bridge construction (ABC) technique with two different GSS systems and were tested to failure using cyclic quasi-static loads. One GSS system was used to connect an RC bridge pier cap to a column and the second GSS system was used to connect an RC footing to a column. Failure of the four original specimens occurred at drift ratios between 5.6 and 8.0% with longitudinal bar fracture or pullout from the GSS connections. The repair method successfully relocated the plastic hinge to the original column section adjacent to the repair and was capable of restoring the diminished load and displacement capacity. The method is a viable and cost-effective technique for rapid seismic repair of severely damaged precast bridge assemblies. © Copyright 2016. American Concrete Institute. All rights reserved. Source

Discover hidden collaborations