Assessing the Scale Effect on Bearing Capacity of Undrained Subsoil: Implications for Seismic Resilience of Shallow Foundations

This research investigates the influence of the scale effect on the bearing capacity of fine-grained subsoil under undrained conditions. The analyses were conducted based on laboratory tests of silty clay. Uniformly compacted samples were subjected to an unconfined compression test. The research was performed on cylindrical specimens. Three different variants of the diameter D (38 mm, 70 mm, 100 mm) and the corresponding height H = 2D were analyzed. Based on the tests results, the unconfined compression strength qu was determined, and from this, the undrained shear strength cu was calculated. The obtained results showed a clear decrease in cu with increasing sample size. However, in the existing reference documents, there are no specific guidelines for calculations of bearing capacity with consideration of sample size effect on the soil shear strength. Therefore, this study utilized the laboratory soil test data to calculate the bearing capacity of undrained subsoil, taking into account the seismic impacts, with a particular focus on spread foundations.

Physical exam is not an accurate predictor of injury in geriatric patients with low-energy blunt trauma - A retrospective cohort study

Background

When evaluating trauma patients, many centers perform computed tomography of the head, cervical spine, chest, abdomen, and pelvis, the so-called “pan-scan.” Here, we evaluate the utility of physical exam against pan-scan in geriatric patients who sustained ground-level falls.

Methods

We performed a single-centered retrospective cohort review of consecutive patients from the trauma registry of a large, urban Level 1 trauma center. Inclusion criteria were registration during the 2019 calendar year, age ≥65, mechanism of fall from either sitting or standing, and performance of “pan-scan” at time of assessment. The sensitivity, specificity, positive and negative predictive values of the physical exam for significant injuries were calculated. The effect of such injuries on disposition from the emergency department and hospital were determined.

Results

An initial query for patients age ≥65 yielded 1280 patients. After exclusion of patients who did not undergo pan-scan or who had GCS <14, 751 patients were included in analysis. Median age was 84 years old. 351 patients had at least one injury identified on pan-scan. Physical exam was determined to have a sensitivity of 0.69 when compared to pan-scan as a gold standard. Patients with injury identified on CT scan had significantly more admissions, mortalities, and ICU and OR requirements.

Conclusion

Approximately half of all patients were found to have at least one injury on pan-scan. Physical examination was insensitive at identifying such injuries which ultimately altered patient management, disposition, and outcomes. Pan-scan is recommended in this vulnerable population.

•

A selective approach to CT scan may not be appropriate for elderly patients with low-energy blunt falls.

•

Approximately half of all elderly patients who fall from sitting or standing have at least one traumatic injury.

•

Traumatic injuries alter the hospital course and disposition of elderly fall patients.

•

Physical exam is neither sensitive nor specific enough to detect these injuries.

Testing Crack Resistance of Non-Load-Bearing Ceramic Walls with Door Openings

Cracking in non-load-bearing internal partition walls is a serious problem that frequently occurs in new buildings within the short term after putting them into service or even before completion of construction. Sometimes, it is so considerable that it cannot be accepted by the occupiers. The article presents tests of cracking in ceramic walls with a door opening connected in a rigid and flexible way along vertical edges. The first analyzes were conducted using the finite element method (FEM), and afterward, the measurements of deformations and stresses in walls on deflecting floors were performed on a full scale in the actual building structure. The measurements enabled to determine floor deformations leading to cracking of walls and to establish a dependency between the values of tensile stresses within the area of the door opening corners and their location along the length of walls and type of vertical connection with the structure.

Tests of Concrete Strength across the Thickness of Industrial Floor Using the Ultrasonic Method with Exponential Spot Heads

The accepted methods for testing concrete are not favorable for determining its heterogeneity. The interpretation of the compressive strength result as a product of destructive force and cross-section area is burdened with significant understatements. It is assumed erroneously that this is the lowest value of strength at the height of the tested sample. The top layer of concrete floors often crumble, and the strength tested using sclerometric methods does not confirm the concrete class determined using control samples. That is why it is important to test the distribution of compressive strength in a cross-section of concrete industrial floors with special attention to surface top layers. In this study, we present strength tests of borehole material taken from industrial floors using the ultrasonic method with exponential spot heads with a contact surface area of 0.8 mm² and a frequency of 40 kHz. The presented research project anticipated the determination of strength for samples in various cross-sections at the height of elements and destructive strength in the strength testing machine. It was confirmed that for standard and big borehole samples, it is not possible to test the strength of concrete in the top layer of the floor by destructive methods. This can be done using the ultrasonic method. After the analysis, certain types of distributions of strength across concrete floor thickness were chosen from the completed research program. The gradient and anti-gradient of strength were proposed as the new parameters for the evaluation of floor concrete quality.

Examining the Distribution of Strength across the Thickness of Reinforced Concrete Elements Subject to Sulphate Corrosion Using the Ultrasonic Method

Sulphate corrosion of concrete is a complex chemical and physical process that leads to the destruction of construction elements. Degradation of concrete results from the transportation of sulphate compounds through the pores of exposed elements and their chemical reactions with cementitious material. Sulphate corrosion can develop in all kind of structures exposed to the corrosive environment. The mechanism of the chemical reactions of sulphate ions with concrete compounds is well known and described. Furthermore, the dependence of the compressive strength of standard cubic samples on the duration of their exposure in the sulphate corrosion environment has been described. However, strength tests on standard samples presented in the scientific literature do not provide an answer to the question regarding the measurement methodology and actual distribution of compressive strength in cross-section of reinforced concrete structures exposed to sulphate ions. Since it is difficult to find any description of this type of test in the literature, the authors undertook to conduct them. The ultrasonic method using exponential heads with spot surface of contact with the material was chosen for the measurements of concrete strength in close cross-sections parallel to the corroded surface. The test was performed on samples taken from compartments of a reinforced concrete tank after five years of operation in a corrosive environment. Test measurements showed heterogeneity of strength across the entire thickness of the tested elements. It was determined that the strength of the elements in internal cross-sections of the structure was up to 80% higher than the initial strength. A drop in the mechanical properties of concrete was observed only in the close zone near the exposed surface.

FPF1 promotes flowering in Arabidopsis

We have characterized the gene flowering promoting factor1 (FPF1), which is expressed in apical meristems immediately after the photoperiodic induction of flowering in the long-day plants mustard and Arabidopsis. In early transition stages, expression is only detectable in the peripheral zone of apical meristems; however, later on, it can also be found in floral meristems and in axillary meristems that form secondary inflorescences. The FPF1 gene encodes a 12.6-kD protein that has no homology to any previously identified protein of known function. Constitutive expression of the gene in Arabidopsis under control of the cauliflower mosaic virus 35S promoter resulted in a dominant heritable trait of early flowering under both short- and long-day conditions. Treatments with gibberellin (GA) and paclobutrazol, a GA biosynthesis inhibitor, as well as crosses with GA-deficient mutants indicate that FPF1 is involved in a GA-dependent signaling pathway and modulates a GA response in apical meristems during the transition to flowering.