Strap System Research Articles

Tentacle Mesh for Fixation-Free Spigelian Hernia Repair: Mini-Invasive Approach Granting Broad Defect Overlap.

Compared to other types of abdominal protrusions, Spigelian hernias are not very common. In prosthetic repair of abdominal protrusions, mesh fixation and defect overlap are an open issue, as they are a source of complications. A newly developed tentacle-shaped mesh has been used to ensure a fixation-free repair with a broader defect overlap in the repair of abdominal hernias. This study describes the long-term results of a fixation-free repair of Spigelian hernias carried out with a tentacle mesh. A proprietary mesh composed of a central body with integrated radiating arms was used for repairing Spigelian hernias in 54 patients. The implant was positioned in preperitoneal sublay, and the straps were delivered across the abdominal musculature with a needle passer, and then, after fascia closure, cut short in the subcutaneous layer. The friction of the straps passing through the abdominal wall served to hold the mesh in place, guaranteeing a wide overlap over the defect without fixation. In a long-term follow-up of 6 to 84 months (mean 64 months), a very low rate of complications occurred, but no recurrence was reported. The tentacle strap system of the prosthesis allowed for an easy, fast and safe fixation-free placement granting a wide overlap, avoiding intraoperative complications. Greatly reduced pain and a negligible amount of postoperative complications characterized the postoperative outcome.

Anthropometrics, Exercise Duration Associated With Force And Rate Of Force Development During A Suspended Plank

Suspension training is used in rehabilitation and fitness training settings due to its ability to challenge various muscle groups. Suspended planks require an individual to support their body weight and are mostly used as an advanced core endurance exercise. PURPOSE: To determine how force and rate of force development (RFD) during a suspended plank relate to total hold time and participant body size and activity level. METHODS: Forty physically active, asymptomatic individuals (Age: 23.6 ± 4.9 years, Height: 169.7 ± 6.9 cm, Weight: 151.0 ± 22.4lbs, 20 males, 20 females) participated in this study. Prior to exercise, individuals completed the International Physical Activity Questionnaire (IPAQ: 5850.6 ± 3746.6mets). Participants performed a prone plank holding onto the suspension strap system attached to a closed door, with arms in full extension and feet fixed on the floor. A load cell sensor was attached to the suspension strap above the participant’s right hand and measured force (lbs) and RFD (lbs/s). Plank time (s) started when the participant raised into the appropriate plank position and stopped when they could no longer maintain proper form. Mean and standard deviation were calculated for force, RFD, plank time, height, and weight. Pearson’s r correlation was used for force and participant characteristics, and Spearman’s ρ correlation was calculated for all RFD relationships. RESULTS: Participants held the suspended plank for 25.5 ± 14.8 s and exhibited an average force of 110.1 ± 20.4lbs (RFD min -25.2lbs/sec, max 1.96lbs/sec). Plank time revealed a strong positive relationship with RFD (ρ = .81, p < .001). Height (r = .58, p < .001) and weight (weight r = .83, p < .001) showed a significant positive relationship with force. Weight was also indirectly associated with days (ρ = -.37, p = .02) and minutes/week (ρ = -.33, p = .04) spent walking from the IPAQ. CONCLUSIONS: Body size was directly related to force production during the suspended plank exercise. Individuals who walked more frequently may have had less body weight to control, thus reducing the force required to maintain the plank position. Understanding how various body sizes and activity levels impact body weight stabilization exercise is important for clinicians and practitioners in sports medicine and fitness settings who may utilize suspension training.

Assessing the Fit of N95 Filtering Facepiece Respirators Fitted with an Ear Loop Strap System: A Pilot Study.

Throughout the COVID-19 pandemic, hundreds of millions of people worldwide have become new users of respiratory protective devices. Facemasks and KN95 respirators utilizing an ear loop straps system (ELSS) have recently become popular among occupational and non-occupational populations. Part of this popularity is due to the ease of wearability as compared with traditional devices utilizing two headbands, one worn over the head and the other behind the neck—a universal strap system used in NIOSH-certified N95 filtering facepiece respirators (FFRs). Some users convert the two-strap configuration to an adjustable ELSS. The first objective of this pilot study was to quantitatively characterize how such a conversion impacts the respirator fit. Additionally, a novel faceseal (NFS) technology, which has been previously demonstrated to enhance the fit of N95 FFRs, was deployed to modify the ELSS-converted N95 FFRs. The second objective of this study was to quantify the fit improvement that results from adding the NFS to the ELSS. The study was conducted by performing the Occupational Safety and Health Administration (OSHA)-approved quantitative fit testing (QNFT) on 16 human subjects featuring different facial shapes and dimensions. Three models of cup-shaped N95 FFRs were tested in three versions: the standard version with manufacturer’s strap system, the ELSS-converted, and the ELSS-converted version modified by adding the NFS. QNFT demonstrated that the fit of an N95 FFR featuring the traditional/standard headbands strap system is negatively impacted when this system is converted to an ELSS. The fit of an ELSS-converted respirator can be significantly improved by the addition of the NFS. We found that the FFR model and the strap system version are significant factors affecting the QNFT-determined respirator fit factor (FF), as well as the OSHA QNFT pass rate (FF ≥100). The findings suggest that the current NFS, if further improved, has a potential for developing a ‘universally fitting’ ELSS-equipped N95 FFR that can be used by the general public, the vast majority of whom do not have access to OSHA fit requirements.

Prescription practices for rigid ankle-foot orthoses among UK orthotists.

The purpose of this study was to investigate rigid ankle-foot orthosis (AFO) prescription practices for adult men among UK orthotists. A cross-sectional study using a survey was distributed online to UK orthotists by the British Association of Prosthetists and Orthotists to its members and through social media and orthotic networks. The survey was completed between November 1, 2020, and November 29, 2020. Descriptive statistics of survey results include information related to the material used, the thickness of the material, positive cast rectification, AFO reinforcement, footplate design, padding, strapping system, and height of AFO. One hundred participants completed the survey, which equates to a response rate of 30.5% of the British Association of Prosthetists and Orthotists members targeted. A clear consensus emerged on the design of a bespoke rigid AFO for the hypothetical patient in this study, which is detailed as follows: 1) 4.5 mm copolymer polypropylene, 2) no additional reinforcement, 3) full-length footplate with mediolateral trimlines terminating behind the metatarsal heads, 4) 3-point correction with parallel sides, 5) padded VELCRO straps with D-rings at the calf and heel, 6) no forefoot or other additional strapping, 7) 3-mm PORON (international Ltd) padding at the malleoli, and 8) AFO height that finishes 2 cm below the fibular head. This study has highlighted a consensus on AFO prescription/design among UK orthotists surveyed, based on the hypothetical patient described in this study.

Combined effect of orthotic intervention and conventional exercise training on balance and gait performance in cerebral palsy: a randomized controlled trial

BackgroundThis study aimed to examine the combined effect of orthotic intervention and conventional therapeutic exercise training on balance and gait performance in children with cerebral palsy. This study was a randomized control trial. Forty children with dyskinetic cerebral palsy of both genders with ages ranged from 12 to 16 years were included. Participants in the control and study groups received a conventional therapeutic exercise training program for two 2 h ours per session. The treatment program was conducted three sessions per week, for twelve 12 successive weeks. Children in the study group additionally wore TheraTogs orthotic undergarment with the strapping system. Pediatric Balance Scale score and postural stability indices (overall, anteroposterior , and mediolateral) evaluated by the Biodex Balance System were assessed (in both groups) at baseline and after 12 weeks of treatment. The changes of step length, gait cycle time, cadence, and velocity were also measured by an electronic walkway.ResultsChildren in the study group showed significant improvements in the scores of all the measured variables post-treatment compared to the control group (P < 0.05). The P -values for overall, anteroposterior and mediolateral postural stability indices were 0.011, 0.014, and 0.021, respectively. The P -values for Pediatric Balance Scale score, step length, gait cycle time, cadence, and velocity were 0.001, 0.023, 0.041, 0.011, and 0.013 respectively.ConclusionsConventional therapeutic exercise training combined with orthotic intervention were more effective in improving balance and gait performance in children with dyskinetic cerebral palsy.Trial registrationThe ClinicalTrial.gov PRS (NCT04990193).Registered 4 August 2021 - Retrospectively registered.

Rethinking Ankle-Foot Orthosis Design: Feasibility Study of a Flexible AFO

ABSTRACT Introduction Ankle-foot orthoses (AFOs) are devices used to control the position and motion of the ankle and foot, so a safe and more efficient gait pattern results for people with lower-limb dysfunction. To provide the ankle and foot control, an AFO is typically made of hard plastic material. Research has shown that discomfort, difficulty using the device, or perceived lack of walking improvement results in low adherence to AFO use. The purpose of this study was to investigate an AFO made of a more flexible material to see if these drawbacks are improved. Methods Participants with a wide range of neurologic and musculoskeletal pathologies were issued a flexible AFO (FAFO). Performance and satisfaction data were collected at baseline, 2-week, and 3-month time points. Data collection included measures of balance (Berg Balance Scale) and temporal and spatial gait parameters (collected via the GAITRite Walkway System). Walking endurance was measured with the 6-minute walk test. Patient satisfaction was investigated using the Orthotic and Prosthetic User Satisfaction Survey (OPUS). Wearing adherence was measured as a percentage of the number of hours of wearing the FAFO per day. Results Statistical analysis using a paired t-test showed improvement was found from baseline to 2 weeks for balance and gait parameters of normalized velocity, double-limb support, and the Functional Ambulation Profile. These improvements were maintained at the 3-month follow-up. No improvement was found in patient satisfaction or walking endurance. Wearing adherence (number of hours per day) was found to be at the highest level of traditional AFO adherence-reported prior research. Conclusions This study found sufficient evidence to indicate the FAFO may be a feasible alternative to traditional hard material AFOs. Experimental trials comparing the FAFO to known gait improvements of currently accepted/traditional AFOs are needed. Clinical Relevance The FAFO investigated in this study provides beginning support for the feasibility of using ethylene-vinyl acetate thermoplastic as the sole material (coupled with the FAFO strapping system) for manufacturing an AFO. If further investigation confirms our findings, the FAFO can provide patients and orthotists another option to materials currently used in the manufacturing of an AFO.

The impact of conservative soft orthotic intervention with strapping on thoracic kyphotic posture and spinal mobility in children with cerebral palsy: a randomized control trial

BackgroundThis study mainly aimed to evaluate the influences of Thera Togs orthotic undergarment with its strapping system on dorsal kyphotic posture and spinal mobility in children with spastic diplegic cerebral palsy. The study also investigated the impact of the modulation of thoracic kyphosis on balance and risk of falls in these children.Study designThis study was a randomized control trial.ParticipantsForty children with diplegic cerebral palsy, aged from 8 to 10 years were met the inclusion criteria and participated in this study. Only 38 children completed the study.MethodsThe children in the control group received 2 h of conventional exercise protocol aiming for modulating thoracic kyphotic posture. The treatment program was conducted 3 times/week, for 12 successive weeks. Children in the study group wore TheraTogs orthoses with the strapping system for 8 h every day in combination with the conventional exercise program.Outcome measuresFor both groups, the primary outcome measures (thoracic kyphotic angle, and thoracic flexion and extension range of motion), and the secondary outcomes (the overall stability index of fall risk test, and the pediatric balance scale score) were recorded at baseline and after completion of the treatment. T test was used to compare the changes within-and between-groups in all measured variables, at baseline and immediately after 12 weeks of treatment.ResultsChildren in the study group showed significant improvements in the scores of all primary and secondary measures post-treatment compared to the control group (P < 0.05).ConclusionConservative treatment composed of TheraTogs orthotic system with conventional exercise treatment is effective in modulating thoracic kyphosis and improving dorsal range of motion in children with spastic diplegic cerebral palsy. This improvement has a positive influence on postural balance performance and reduces the risk of fall in these children.Trial registrationThe ClinicalTrial.gov PRS (NCT05063175). 30 September 2021—retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05063175

Effect of functional electrical stimulation versus TheraTogs on gait and balance in children with hemiplegic cerebral palsy: a randomized controlled trial

BackgroundChildren with cerebral palsy exhibit postural restrictions and gait problems as a result of both primary and secondary brain damage impairments. One of the main goals of cerebral palsy rehabilitation is to improve gait and balance. As a result, the purpose of this study was to compare the effects of FES and TheraTogs on gait and balance in children with hemiplegic CP. A randomized controlled study was conducted on 30 children with hemiplegic CP (18 boys and 12 girls) between the ages of 8 and 12 years. The children were divided into two equal groups. In addition to the traditional physical treatment program, the FES group received functional electrical stimulation (pulse width 300 μs, frequency 33 Hz, 2 h/day, 3 days/week, 3 months). The TheraTogs group, on the other hand, received the TheraTogs strapping system as well as the same traditional program for the same time period. The 3-D motion analysis and the Biodex balance system were used to analyze gait parameters and postural stability at baseline and 3 months after the intervention.ResultsWhen comparing the mean values of the gait parameters and postural stability indices of children in both groups before and after treatment, a significant improvement was reported. Furthermore, the FES group showed a greater improvement in all of the measured outcomes (P < 0.001).ConclusionFunctional electrical stimulation improves gait pattern and postural stability in children with hemiplegic cerebral palsy significantly more than TheraTogs strapping systems.Clinical trial registrationThis study was registered in the ClinicalTrial.gov PRS (NCT05020834).

Component-Level Finite Element Model and Validation for a Modern American Football Helmet

Epidemiological data and measurement of biomechanical data collected through physical experiments have contributed to the understanding of potential head injury risk in contact sports such as football. Further improvement of protective helmets requires repeatable conditions and detailed parametric studies that may be addressed in part using the Finite Element (FE) method. However, such an approach requires thorough experimentation and validation of the helmet materials and subcomponents, which previous studies do not fully address, prior to implementing these subcomponents in a full helmet model. Development of a modern football helmet FE model requires a bottom-up approach, focusing on material testing, constitutive models and subcomponent-level validation, which has not been fully addressed in the literature to date. Material samples were extracted from a modern football helmet including the helmet shell, energy-absorbing structures, comfort foam, and strap system. The subcomponents were tested across a range of quasi-static and high deformation rates relevant to football impact scenarios. FE models of the subcomponents were developed and validated, focusing on verification of material behaviour, representative loading conditions, and mesh convergence to achieve realistic responses and increase computational efficiency. Evaluation of the FE models comparing experimental with simulated responses, yielded good to excellent CORrelation and Analysis (CORA) ratings of 0.954–0.985, 0.931, 0.937–0.974, and 0.847–0.958 for the helmet shell, facemask, energy-absorbing structures, and comfort pads, respectively. The resulting validated subcomponent-level models provide an important foundation for integration into a full helmet model to ultimately optimize performance and reduce head injury.

Recent evidence on early mobilization in critical-Ill patients.

To examine the benefits of early mobilization and summarize the results of most recent clinical studies examining early mobilization in critically ill patients followed by a presentation of recent developments in the field. Early mobilization of ICU patients, defined as mobilization within 72 h of ICU admission, is still uncommon. In medical and surgical critically ill patients, mobilization is well tolerated even in intubated patients. In neurocritical care, evidence to support early mobilization is either lacking (aneurysmal subarachnoid hemorrhage), or the results are inconsistent (e.g. stroke). Successful implementation of early mobilization requires a cultural change; preferably based on an interprofessional approach with clearly defined responsibilities and including a mobilization scoring system. Although the evidence for the majority of the technical tools is still limited, the use of a bed cycle ergometer and a treadmill with strap system has been promising in smaller trials. Early mobilization is well tolerated and feasible, resulting in improved outcomes in surgical and medical ICU patients. Implementation of early mobilization can be challenging and may need a cultural change anchored in an interprofessional approach and integrated in a patient-centered bundle. Scoring systems should be integrated to define daily goals and used to verify patients' achievements or identify barriers immediately.

Patient Litter System Response in a Full-Scale CH-46 Crash Test.

U.S. Military aeromedical patient litter systems are currently required to meet minimal static strength performance requirements at the component level. Operationally, these components must function as a system and are subjected to the dynamics of turbulent flight and potentially crash events. The first of two full-scale CH-46 crash tests was conducted at NASA's Langley Research Center and included an experiment to assess patient and litter system response during a severe but survivable crash event. A three-tiered strap and pole litter system was mounted into the airframe and occupied by three anthropomorphic test devices (ATDs). During the crash event, the litter system failed to maintain structural integrity and collapsed. Component structural failures were recorded from the litter support system and the litters. The upper ATD was displaced laterally into the cabin, while the middle ATD was displaced longitudinally into the cabin. Acceleration, force, and bending moment data from the instrumented middle ATD were analyzed using available injury criteria. Results indicated that a patient might sustain a neck injury. The current test illustrates that a litter system, with components designed and tested to static requirements only, experiences multiple component structural failures during a dynamic crash event and does not maintain restraint control of its patients. It is unknown if a modern litter system, with components tested to the same static criteria, would perform differently. A systems level dynamic performance requirement needs to be developed so that patients can be provided with protection levels equivalent to that provided to seated aircraft occupants.

A Look Inside the Apple Watch: Intellectual Property Rights and Future Legal Battles

It is not just a watch. It is a masterpiece of intellectual property (IP) rights. It is not just a revolutionary product. It is the next chapter in Apple Inc.’s story.Apple believes in technology designed for the wrist (such as a smartwatch), but also in a strong design patent protection strategy. To protect this wearable, as a result of their investment, Apple applied for and received several design patents. Every detail is protected: the drawer where the watches are shown, the bracelet, the “slide-in” interchangeable strap system mechanism, the digital crown, the display, the charger, the retail box, etc. Future innovations will however continue to copy this kind of consumer products and challenge the Courts.In this context, developing and/or acquiring intellectual property rights may create a solid foundation for growth and success. Indeed, a winning exploitation of IP assets, including but not limited to know-how, patents, trademarks, aligned with your passion for innovation and your business strategy, may contribute to increase protection and enforcement measures against infringers and competitors.This Note examines how a maker of wearable devices, such as Apple, can use different forms of intellectual property rights in Europe, China, and the United States, as well as other intangible assets, to protect a business product.

Fixation-free incisional hernia repair in the elderly: our experience with a tentacle-shaped implant.

Incisional hernia in aged patients represents a challenge even for experienced surgeons. Besides increased risk of complications due to comorbidities, mesh fixation and assuring a sufficient mesh overlap of the defect are the main issues in carrying out the repair. In order to assure broader coverage of the abdominal wall and a tension- and fixation-free repair, a specifically designed prosthesis was developed for the surgical treatment of incisional hernias. The results of a fixation-free incisional hernia repair carried out in elderly patients using a tentacle-shaped implant are reported herewith. A tentacle-shaped flat mesh with a large central body and integrated arms was used to repair incisional hernia in 23 elderly patients. The mesh was placed fixation-free and secured in place through the friction exerted by the tentacles. All tentacle straps were positioned with a special passer needle. Implant placement was preperitoneal in 18 patients and retromuscular sublay in five. In a follow-up of 18 to 59months (mean 36months), four seromas occurred. Postoperative fast track helped avoid the typical complications affecting this patient subset. No infection, hematoma, chronic pain, mesh dislocation or recurrence have been reported to date. The tentacle strap system allowed for reduced skin incision thus minimizing surgical trauma and ensuring easier and faster implant placement. The tentacle arms of the implant ensured mesh stability and broad defect overlap. Besides a very low complication rate, none of the typical postoperative complications of aged patients occurred.

Seismic Retrofitting Techniques for Historic Adobe Buildings

This article presents a comprehensive overview of the techniques available for the seismic retrofitting of adobe buildings. It analyzes these techniques’ viability from a structural engineering standpoint and evaluates their suitability in the context of historic preservation. Analysis was based on an exhaustive review of studies addressing retrofitting techniques of earthen structures, as well as consultation with field experts. The guiding principles of conservation relating to the structural reinforcement of monuments were taken into account. Traditional techniques that enhance the stability of the building, such as wooden ring beams, wooden ties interconnecting parallel walls, corner keys, and the addition of buttresses were found to be effective solutions since they employ compatible and low-cost materials such as earth and wood. When these techniques prove insufficient, minimally invasive measures such as introducing a plywood diaphragm, horizontal steel rods, a geomesh covered with mud rendering or a strapping system can be appropriate.

The clinical impact of orthotic correction of lower limb rotational deformities in children with cerebral palsy: a randomized controlled trial

Objective: This study aimed to evaluate the effectiveness of a static ground reaction ankle foot orthosis and strapping system on improving gait parameters in children with spastic diplegic cerebral palsy. Setting: The current study was conducted at the physical therapy faculty of Cairo University, Egypt. Subjects: This study included 57 children of both sexes, aged 6 to 8 years. Study design: Three-armed randomized control trial. Intervention: Participants in all groups received a traditional neuro-developmental physical therapy program that included standing and gait training exercises. Children in group A performed the training program without any orthotic management, in group B with the TheraTogs™ strapping system, and in group C with the TheraTogs™ strapping system and static ground reaction ankle foot orthoses. Children underwent treatment for two hours daily, except on weekends, for twelve successive weeks. Main measure: Gait speed, cadence, stride length, and hip and knee flexion angles in the mid-stance phase were evaluated pre-and post-treatment using a three-dimensional motion analysis system (pre-reflex system). Results: Statistically significant differences were recorded among the three groups post-treatment in gait speed, cadences, and stride length. The P-values for these variable differences were 0.03, 0.011, and 0.001 respectively. Significant post-treatment differences were also recorded for bilateral hip-and knee-flexion angles. For all measured parameters, better significant results were registered for group C than for the other groups. Conclusion: Orthotic intervention composed of a static ground reaction ankle foot orthosis combined with the TheraTogs™ strapping system improves gait more than conventional treatment with or without TheraTogs™ in children with spastic diplegic cerebral palsy.

Design of Control System in Strapping Machine for Paper Bills

The strapping machine for Paper Bills typically was designed to reduce labor intensity and enhance production automation level. The machines structure and working principle were described. There are three work posts in this equipment, they work continuously. This approach makes it very easy to split up a complex transformation into a series of simple transformations arranged in a loop line. The machine includes currency count/counterfeit distinguishing system, conveying system and strapping system. In the same time, the machine control system that adopts the PLC programmable controller can simplify the control system, and its reliability strengthens further. Practices show that the strapping machine has the advantages of simple structure, high efficiency, low cost and small vibrating noise.

Rectangular Reinforced Concrete Beams Strengthened with CFRP Straps

AbstractShear-deficient reinforced concrete (RC) structures can be effectively strengthened using external prestressed carbon fiber–reinforced polymer (CFRP) straps. Due to the presence of the external elastic straps, a strengthened beam can continue to carry significant load beyond the stages of crack plane slipping and internal-shear stirrup yielding, and the concrete is subjected to high tensile strain levels. As a consequence, the concrete material models play a significant role in the context of modeling such behavior. The modified compression field theory (MCFT), which is a widely accepted shear theory for unstrengthened RC structures, incorporates the details of the stress-strain behavior of concrete. The MCFT also considers compatibility as a governing factor, which facilitates the inclusion of the strap system into the MCFT formulation. In the current study, modifications were investigated to model CFRP strap retrofitted RC beams associated with either uniform or nonuniform strap spacings. An exp...

Bioimpedance-Based Wearable Measurement Instrumentation for Studying the Autonomic Nerve System Response to Stressful Working Conditions

The assessment of mental stress on workers under hard and stressful conditions is critical to identify which workers are not ready to undertake a mission that might put in risk their own life and the life of others. The ATREC project aims to enable Real Time Assessment of Mental Stress of the Spanish Armed Forces during military activities. Integrating sensors with garments and using wearable measurement devices, the following physiological measurements were recorded: heart and respiration rate, skin galvanic response as well as peripheral temperature. The measuring garments are the following: a sensorized glove, an upper-arm strap and a repositionable textrode chest strap system with 6 textrodes. The implemented textile-enabled instrumentation contains: one skin galvanometer, two temperature sensors, for skin and environmental, and an Impedance Cardiographer/Pneumographer containing a 1 channel ECG amplifier to record cardiogenic biopotentials. The implemented wearable systems operated accordingly to the specifications and are ready to be used for the mental stress experiments that will be executed in the coming phases of the project in healthy volunteers.

Precracked Reinforced Concrete T-Beams Repaired in Shear with Prestressed Carbon Fiber-Reinforced Polymer Straps

The results of an experimental and numerical investigation involving unstrengthened reinforced concrete (RC) T-beams and precracked RC T-beams strengthened in shear with prestressed carbon fiber-reinforced polymer (CFRP) straps are presented and discussed. The results provide insights into the influence of load history and beam depth on the structural behavior of both unstrengthened and strengthened beams. The strengthened beams exhibited capacity enhancements of 21.6 to 46% compared to the equivalent unstrengthened beams, demonstrating the potential effectiveness of the prestressed CFRP strap system. Nonlinear finite element (FE) predictions, which incorporated the load history, reproduced the observed experimental behavior but either underestimated or overestimated the post-cracking stiffness of the beams and strap strain at higher load levels. These limitations were attributed to the concrete shear models used in the FE analyses.

Carbon Fiber-Reinforced Polymer Punching Reinforcement and Strengthening of Concrete Flat Slabs

Three different carbon fiber-reinforced polymer (CFRP) systems were used to reinforce new or strengthen existing concrete slabs against punching. Untensioned CFRP plates or only very low prestressed CFRP straps could not prevent brittle punching failure. Strap prestressing of at least 15% of the tensile strength led to a ductile two-peak slab response although the CFRP material systems were brittle. The ultimate load of the unreinforced slabs could be increased by 77 to 118% via a redistribution of forces from the concrete to the strap system. An empirical model was established that is able to estimate the first peak load of all the applied CFRP systems. It takes into account the parameters CFRP plate or strap strength, CFRP geometry, CFRP prestressing level, and punching load of the unreinforced slab. A cantilever strut-and-tie model was established to estimate the second peak load. Both models provide acceptable accuracy.