Digitized by Kansas Correctional Industries

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

In 2011, the U.S. Bureau of Labor Statistics documented injury rates of musculoskeletal injuries requiring days away from work in the full-time firefighter work force at approximately 185/10,000 employees. This represents a staggering cost to municipalities in overtime salaries as well as departmental readiness to meet community needs. We propose, in year one of the project, to observationally determine the prospective association between physical performance measures at baseline and risk of future musculoskeletal injury in a cohort of municipal firefighters of the Austin Fire Department (AFD). We will implement an injury registry surveillance system as well as utilize the AFD Wellness Center physical fitness evaluation of all firefighters within AFD. The prospective association between changes in physical performance measures and risk of musculoskeletal injury within a cohort of AFD firefighters will allow determination of risk of occupational injury incidence and injury severity. To study the effect of musculoskeletal training on lowering the risk of occupationally-related injury, we will conduct a randomized cluster cross-over trial. The critical intervention will be a strength training intervention of six months duration, implemented in Year 2. There are a total of 43 fire stations in the AFD. We will randomize 50% of the fire stations in a strength training intervention for six months with the remaining 50% of fire station participating for the second six months. Changes in fitness, strength, and incidence of injury will be monitored for the 12 months of this design. Results from this study will be disseminated to firefighting agencies with strategies for occupationally-related musculoskeletal injury prevention. / text

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The present recommendations of the ACI-ASCE Committee 352 for the design of ductile moment resistant beam to column connections limit the joint shear stress to γ√f'(c), where the factor γ is a function of the joint geometric classification and the loading condition. The value of compressive strength f'(c) used in the above expression should not exceed 6000 psi. This limitation causes considerable difficulty in the design of high-strength concrete frames. An experimental study of twelve large-scale exterior beam to column subassemblies was completed at The University of Arizona. The specimens were subjected to cyclic inelastic loading. The variables studied were the concrete compressive strength (8.1, 10.7, and 13.6 ksi), the joint shear stress (1100 and 1400 psi), and the degree of joint confinement provided in the form of closed ties. Although high-strength concrete is more brittle than normal-strength concrete, the study showed that frames constructed of high-strength concrete can perform satisfactorily in earthquakes zones when attention is given to proper detailing of joints. The flexural strength ratio, degree of joint confinement, development length of bars, and joint shear stress are all very important factors to be considered in the design process. The maximum permissible joint shear stress suggested by ACI-ASCE Committee 352 was modified for frames constructed with high-strength concrete. The proposed joint shear stress drawn from test results does not affect the factor γ which depends on the joint type and its geometric classification. Therefore, in the absence of any further data about interior joints, the proposed joint shear limit for high-strength concrete can be used for all types and geometric classifications of joints. Furthermore, new requirements for joint confinement were presented to ensure ductile behavior of frames. It is important to note that current Recommendations for joint confinement, which were developed for normal-strength concrete, cannot be satisfied for high-strength concrete frames. The hysteresis response of specimens tested and other normal-strength concrete specimens tested by different investigators were compared in terms of their energy absorption capacity. This comparison was essential to alleviate concern about the lack of ductility of high-strength concrete. Favorable results were obtained. This research is important for practitioners to gain more confidence using high-strength concrete for structural design applications especially in seismic zones.

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No description available.