Seismic Behavior and Detailing of High-Performance Fiber-Reinforced Concrete Coupling Beams and Coupled Wall Systems

The seismic behavior of coupling beams and walls constructed with tensile strain-hardening, high-performance fiber-reinforced concrete (HPFRC) was studied through tests of large-scale precast coupling beams and coupled walls. A precast coupling beam design was developed to speed up construction and minimize interference with wall reinforcement. Three isolated precast coupling beam specimens with a span-to-depth ratio of 1.75 were tested under large displacement reversals. Test results indicate the use of HPFRC allows a reduction of the reinforcement required to achieve a stable coupling beam response by providing confinement and contributing to beam shear strength. A concrete design shear stress capacity of 0.41√fc’, [MPa] (5√fc’, [psi]), where fc’ is the compressive strength of the concrete, was found to be appropriate. In addition to the coupling beam tests, two four-story coupled wall specimens with precast HPFRC and regular concrete coupling beams were tested under lateral displacement reversals. Besides allowing the evaluation of seismic behavior of coupled walls with HPFRC coupling beams, the use of HPFRC in the plastic hinge regions of the walls as a means of relaxing transverse wall reinforcement was evaluated. The two coupled wall specimens exhibited drift capacities of at least 2.5%. The HPFRC coupling beams were more ductile and damage tolerant than the regular concrete beams. The incorporation of an HPFRC material in the wall allowed the use of a concrete design shear stress capacity of 0.33√fc’, [MPa] (4√fc’, [psi]) and a wider spacing of transverse reinforcement confining the wall boundary regions

Seismic Response of Fiber-Reinforced Concrete Coupled Walls

The behavior of coupled T-shaped structural walls was studied through tests of two large-scale four-story specimens under reversed cyclic lateral displacements. The use of tensile strainhardening, high-performance fiber-reinforced concrete (HPFRC) in coupling beams and walls was evaluated as a means to reduce diagonal and confinement reinforcement. The Specimen CW-1 walls were constructed with reinforced concrete (RC) designed to satisfy ACI Building Code (ACI 318-08) seismic provisions. The walls in Specimen CW-2 were constructed with HPFRC and reduced shear and confinement reinforcement. Each specimen included one RC and three HPFRC precast coupling beams with span-depth ratios of 1.75. Both specimens sustained 80% of the peak lateral strength through loading cycles to at least 2.5% drift. Inelastic flexural deformations were more concentrated near the foundation in the HPFRC walls than in the RC walls, which led to a higher curvature demand at the base of the HPFRC walls. Although the walls in both specimens exhibited a flexuraldominated behavior, shear distortions in the first story of the walls reached 0.01 rad. Detailed data are presented regarding specimen behavior, including wall and coupling beam deformations

Field Investigation of Damage to Islamic Monuments Caused by the Egyptian Earthquake of October 12, 1992

https://deepblue.lib.umich.edu/bitstream/2027.42/154130/1/39015094007583.pd

Test of a Coupled Wall with High Performance Fiber Reinforced Concrete Coupling Beams

Results from the test of a large-scale coupled-wall specimen consisting of two T-shaped reinforced concrete structural walls joined at four levels by precast coupling beams are presented. Each coupling beam had a span length-depth ratio (ln/h) of 1.7, and was designed to carry a shear stress of 7vfc' [psi], (0.59vfc' [MPa]). One reinforced concrete coupling beam was included along with three strain-hardening, high-performance fiber-reinforced concrete (HPFRC) coupling beams to allow a comparison of their behavior. When subjected to reversing lateral displacements, the system behaved in a highly ductile manner characterized by excellent strength retention to drifts of 3% without appreciable pinching of the lateral load versus drift hysteresis loops. The reinforced concrete structural walls showed an excellent damage tolerance in response to peak average base shear stresses of 4.4vfc' [psi], (0.34vfc' [MPa]). This paper presents the observed damage patterns in the coupling beams and the structural walls. The restraining effect provided by the structural walls to damage-induced lengthening of the coupling beams is discussed and compared with that observed in component tests. Finally, the end rotations measured in the coupling beams relative to the drift of the coupled-wall system are also presented

Experimental Evaluation of Design Procedures for Shear Strength of Deep Reinfoced Concrete Beams

In this paper, results from the monotonic testing of four reinforced concrete deep beams are presented. The behavior of the deep beams is described in terms of cracking pattern, load-versus-deflection response, failure mode, and strains in steel reinforcement and concrete. Despite different failure modes, the failure loads and corresponding ultimate deflections were similar in all four specimens. Yielding of both longitudinal and transverse reinforcement occurred prior to failure. Based on the test results, the shear design procedures contained in the ACI 318-99 Code and Appendix A of the ACI 318-02 Code were evaluated. Both design procedures yielded conservative predictions of the shear strength of the single-span deep beams

Earthquake-Resistant Fiber Reinforced Concrete Coupling Beams Without Diagonal Bars

Results from large-scale tests on fibre-reinforced concrete coupling beams subjected to large displacement reversals are reported. The main goal of using fibre reinforcement was to eliminate the need for diagonal bars and reduce the amount of confinement reinforcement required for adequate seismic performance. Experimental results indicate that the use of 30 mm long, 0.38 mm diameter hooked steel fibres with a 2300 MPa minimum tensile strength and in a volume fraction of 1.5% allows elimination of diagonal bars in coupling beams with span-todepth ratios greater than or equal to 2.2. Further, no special confinement reinforcement is required except at the ends of the coupling beams. The fibre-reinforced concrete coupling beam design was implemented in a high-rise building in the city of Seattle, WA, USA. A brief description of the coupling beam design used for this building, and construction process followed in the field, is provided

Implementation of High-Performance Fiber Reinforced Concrete Coupling Beams in High-Rise Core-Wall Structures in the Seattle Area

Experimental and analytical studies that led to the incorporation of strain-hardening, high-performance fiber reinforced concrete (HPFRC) coupling beams in the design of a high-rise core-wall structure in Seattle, WA, are described. A total of eight HPFRC coupling beams with span-to-depth ratios ranging between 1.75 and 3.3 were tested under large displacement reversals. The tension and compression ductility of HPFRC materials allowed an approximately 70% reduction in diagonal reinforcement, relative to an ACI Building Code (318-08) compliant coupling beam design, in beams with a 1.75 span-to-depth aspect ratio and a total elimination of diagonal bars in beams with a 2.75 and 3.3 aspect ratio. Further, special column-type confinement reinforcement was not required except at the ends of the beams. When subjected to shear stress demands close to the upper limit in the 2008 ACI Building Code (0.83 f’c [MPa] (10 f’c [psi])), the coupling beams with aspect ratios of 1.75, 2.75 and 3.3 exhibited drift capacities of approximately 5%, 6% and 7%, respectively. The large drift and shear capacity exhibited by the HPFRC coupling beams, combined with the substantial reductions in reinforcement and associated improved constructability, led Cary Kopczynski & Co. to consider their use in a 134 m (440 ft) tall reinforced concrete tower. Results from inelastic dynamic analyses indicated adequate structural response with coupling beam drift demands below the observed drift capacities. Also, cost analyses indicated 20-30% savings in material costs, in addition to much easier constructability and reduced construction time

Spatial variation in direct and indirect contact rates at the wildlife-livestock interface for informing disease management

Little is known about disease transmission relevant contact rates at the wildlife-livestock interface and the factors shaping them. Indirect contact via shared resources is thought to be important but remains unquantified in most systems, making it challenging to evaluate the impact of livestock management practices on contact networks. Free-ranging wild pigs (Sus scrofa) in North America are an invasive, socially-structured species with an expanding distribution that pose a threat to livestock health given their potential to transmit numerous livestock diseases, such as pseudorabies, brucellosis, trichinellosis, and echinococcosis, among many others. Our objective in this study was to quantify the spatial variations in direct and indirect contact rates among wild pigs and cattle on a commercial cow-calf operation in Florida, USA. Using GPS data from 20 wild pigs and 11 cattle and a continuous-time movement model, we extracted three types of spatial contacts between wild pigs and cattle, including direct contact, indirect contact in the pastoral environment (unknown naturally occurring resources), and indirect contact via anthropogenic cattle resources (feed supplements and water supply troughs). We examined the effects of sex, spatial proximity, and cattle supplement availability on contact rates at the species level and characterized wild pig usage of cattle supplements. Our results suggested daily pig-cattle direct contacts occurred only occasionally, while a significant number of pig-cattle indirect contacts occurred via natural resources distributed heterogeneously across the landscape. At cattle supplements, more indirect contacts occurred at liquid molasses than water troughs or molasses-mineral block tubs due to higher visitation rates by wild pigs. Our results can be directly used for parameterizing epidemiological models to inform risk assessment and optimal control strategies for controlling transmission of shared diseases

Psychosocial impact of the summer 2007 floods in England

Background The summer of 2007 was the wettest in the UK since records began in 1914 and resulted in severe flooding in several regions. We carried out a health impact assessment using population-based surveys to assess the prevalence of and risk factors for the psychosocial consequences of this flooding in the United Kingdom. Methods Surveys were conducted in two regions using postal, online, telephone questionnaires and face-to-face interviews. Exposure variables included the presence of flood water in the home, evacuation and disruption to essential services (incident management variables), perceived impact of the floods on finances, house values and perceived health concerns. Validated tools were used to assess psychosocial outcome (mental health symptoms): psychological distress (GHQ-12), anxiety (GAD-7), depression (PHQ-9) and probable post-traumatic stress disorder (PTSD checklist-shortform). Multivariable logistic regression was used to describe the association between water level in the home, psychological exposure variables and incident management variables, and each mental health symptom, adjusted for age, sex, presence of an existing medical condition, employment status, area and data collection method. Results The prevalence of all mental health symptoms was two to five-fold higher among individuals affected by flood water in the home. People who perceived negative impact on finances were more likely to report psychological distress (OR 2.5, 1.8-3.4), probable anxiety (OR 1.8, 1.3-2.7) probable depression (OR 2.0, 1.3-2.9) and probable PTSD (OR 3.2, 2.0-5.2). Disruption to essential services increased adverse psychological outcomes by two to three-fold. Evacuation was associated with some increase in psychological distress but not significantly for the other three measures. Conclusion The psychosocial and mental health impact of flooding is a growing public health concern and improved strategies for minimising disruption to essential services and financial worries need to be built in to emergency preparedness and response systems. Public Health Agencies should address the underlying predictors of adverse psychosocial and mental health when providing information and advice to people who are or are likely to be affected by flooding

Establishing a large prospective clinical cohort in people with head and neck cancer as a biomedical resource: head and neck 5000

BACKGROUND: Head and neck cancer is an important cause of ill health. Survival appears to be improving but the reasons for this are unclear. They could include evolving aetiology, modifications in care, improvements in treatment or changes in lifestyle behaviour. Observational studies are required to explore survival trends and identify outcome predictors. METHODS: We are identifying people with a new diagnosis of head and neck cancer. We obtain consent that includes agreement to collect longitudinal data, store samples and record linkage. Prior to treatment we give participants three questionnaires on health and lifestyle, quality of life and sexual history. We collect blood and saliva samples, complete a clinical data capture form and request a formalin fixed tissue sample. At four and twelve months we complete further data capture forms and send participants further quality of life questionnaires. DISCUSSION: This large clinical cohort of people with head and neck cancer brings together clinical data, patient-reported outcomes and biological samples in a single co-ordinated resource for translational and prognostic research