Mechanical Loading System Research Articles

Abstract PO2-27-02: Re-sensitizing the Refractory Breast Cancer Bone Metastasis to Endocrine Therapies

Abstract Approximately 90% of Breast Cancer (BrCa) related deaths are caused by metastasis and bone is the first and most frequent site of breast cancer metastatic expansion, which can lead to severe pain, immobility, fractures, and nerve damage, as well as the development of metastases in other organs, hence; a poor quality of life in patients. Currently, treatment options for these bone metastases (BoM) are limited because most patients with BoM shows reduced ER dependency which leads to resistance to standard endocrine or hormonal therapies for estrogen receptor-positive (ER+) BrCa. The long-term goal of the proposed research is to develop a strategy where metastatic cancer cells in bone can be dependent on ER signaling again thereby restoring their sensitivity to endocrine therapies. We observed a transient loss of ER expression in concert with enhanced activity of the transcriptional coactivators YAP/TAZ - the downstream effectors of the Hippo pathway (responsible for regulating cell proliferation and death) during bone colonization by BrCa cells. We hypothesize that the interaction between cancer cells and osteoblasts in the bone microenvironment leads to the activation of calcium signaling in cancer cells, resulting in the de-phosphorylation and nuclear localization of YAP/TAZ which subsequently suppresses the transcription of the estrogen receptor gene (ESR). Our research strategy is as presented below. First, we will employ a combination of 2D/3D co-culture models of BoM along with a mechanical loading system and determine the molecular mechanism driving the dynamical activation of YAP/TAZ in BrCa BoM. Using a unique ex vivo BM model called Bone In Culture Array (BICA) which replicates the in-vivo conditions, we will determine if verteporfin, a YAP/TAZ antagonist, can synergize and possibly enhance the effects of Fulvestrant, an ER antagonist in current use for certain types of BrCa in preventing BoM outgrowths and treating established BoM in mice. This research could ultimately lead to a favorable combination strategy to treat endocrine-resistant BoM in BrCa patients and prolong their survival. Citation Format: Anindita Das, Cheyenne Ernst. Re-sensitizing the Refractory Breast Cancer Bone Metastasis to Endocrine Therapies [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-27-02.

Spatial evolution of pore and fracture structures in coal under unloading confining pressure: A stratified nuclear magnetic resonance approach

The inherent spatial complexity and strong heterogeneity characterise the pore and fracture structures (PFS) in coal. Understanding the spatial evolution of PFS in coal under unloading confining pressure is crucial for ensuring the safety of coal mining operations. In this study, the stratified nuclear magnetic resonance (NMR) technique and a triaxial mechanical loading system were combined to realise real-time observation of the spatial evolution of PFS in coal during the unloading confining pressure process. A conceptual model depicting the spatial evolution of PFS in coal under unloading confining pressure was formulated. Based on our experimental findings, the mesoscopic mechanical behaviour of coal subjected to unloading confining pressure was simulated using PFC 2D. Our research reveals that throughout the unloading confining pressure process, the PFS within coal samples simultaneously exhibits characteristics of both compacted and fractured states, with mutual transformation occurring in the adsorption and seepage pores. A reduction in confining pressure results in a notable escalation of observed damage within the coal samples and intensified development of PFS. Furthermore, our numerical simulation results closely align with NMR test results, providing additional validation to our findings.

MIR-107/HMGB1/FGF-2 axis responds to excessive mechanical stretch to promote rapid repair of vascular endothelial cells

The increase of vascular wall tension can lead to endothelial injury during hypertension, but its potential mechanism remains to be studied. Our results of previous study showed that HUVECs could induce changes in HMGB1/RAGE to resist abnormal mechanical environments in pathological mechanical stretching. In this study, we applied two different kinds of mechanical tension to endothelial cells using the in vitro mechanical loading system FlexCell-5000T and focused on exploring the expression of miR-107 related pathways in HUVECs with excessive mechanical tension. The results showed that miR-107 negatively regulated the expression of the HMGB1/RAGE axis under excessive mechanical tension. Excessive mechanical stretching reduced the expression of miR-107 in HUVECs, and increased the expression of the HMGB1/RAGE axis. When miR-107 analog was transfected into HUVECs with lipo3000 reagent, the overexpression of miR-107 slowed down the increase of the HMGB1/RAGE axis caused by excessive mechanical stretching. At the same time, the overexpression of miR-107 inhibited the proliferation and migration of HUVECs to a certain extent. On the contrary, when miR-107 was silent, the proliferation and migration of HUVECs showed an upward trend. In addition, the study also showed that under excessive mechanical tension, miR-107 could regulate the expression of FGF-2 by HMGB1. In conclusion, these findings suggest that pathological mechanical stretching promote resistance to abnormal mechanical stimulation on HUVECs through miR-107/HMGB1/RAGE/FGF-2 pathway, thus promote vascular repair after endothelial injury. The suggest that miR-107 is a potential therapeutic target for hypertension.

Real-Time Monitoring of Pore-Fracture Structure Evolution during Coal Creep Based on NMR

Understanding the structural change of coals at micro- and mesoscales during the creep process is essential for exploring the time-dependent properties of deep coal and the long-term safe and effective operation of deep underground engineering. The conventional triaxial compression and creep tests on coal are carried out using a nuclear magnetic resonance (NMR) apparatus with a complete mechanical loading system at different confining pressures. The variations of parameters such as peak areas of various pore distributions, pore percentage, and porosity increment are quantitatively analyzed by real-time monitoring of T2 spectra during loading. Combined with nuclear magnetic resonance imaging (NMRI), accurate characterization and visualization of microscopic pore structures in coal are realized. The experimental results show that the adsorption pore proportion in the pore structure of the deep coal sample from Pingdingshan, Henan Province, is more than 80%. The changes in seepage pores and microfractures are most obvious in the triaxial compression and creep test. The creep deformation leads to the development of pore structure, and the creep porosity growth rate M increases gradually with increasing stress levels. M can accurately describe the rapid development of the pore structure and the damage accumulation due to time effects during creep. During creep, the most obvious changes in pore structure are the first and last levels of creep. The fractal dimension shows an “inverted V” trend during creep and is more sensitive to the inhibition of pore-fracture structure evolution due to increasing confining pressure. The creep strain increment and porosity increment during graded creep appear to be a similar behavior, indicating that the change of pore structure in the creep process based on the NMR system test can reveal the creep damage mechanism and indirectly characterize the deformation behavior of coal creep.

Aging Decreases the Ultimate Tensile Strength of Bone–Patellar Tendon–Bone Allografts

The purpose of this study was to determine whether aging imparts a clinically significant effect on the (1) mechanism of graft failure and (2) structural, material, and viscoelastic properties of patellar tendon allografts by evaluating these properties in younger donors (≤30 years of age) and older donors (>50 years of age). A total of 34 younger (≤30 years of age) and 34 older (>50 years of age) nonirradiated, whole bone-tendon-bone allografts were prepared for testing by isolating the central third of the patellar tendon using a double-bladed 10-mm width scalpel under a 10-N load to ensure uniformity of harvest. Bone blocks were potted in polymethylmethacrylate within custom molds. Tendon length and cross-sectional area were measured using an area micrometer. A mechanical loading system was used to precondition the grafts for 100 cycles with a load between 50 N and 250 N (1 Hz). A creep load (500 N) was then applied at a rate of 100 mm/min (10 minutes). Grafts were allowed to recover at 1 N (10 minutes), followed by pull-to-failure at a rate of 100% strain per second. Mechanisms of failure (midsubstance vs avulsion) were noted and the structural, material, and viscoelastic properties calculated and compared between groups. There were 33 (97%) midsubstance tears in the younger group and 28 (82%) in the older group (P= .034). Younger grafts showed greater ultimate load to failure (1,782 N [1,533, 2,032] vs 1,319 N [1,103, 1,533]) (P= .006) and ultimate tensile stress (37.4 MPa [32.4, 42.4] vs 27.5 MPa [22.9, 32.0]) (P= .006). There were no significant differences in displacement (P= .595), stiffness (P= .950), strain (P= .783), elastic modulus (P= .114), creep displacement (P= .881), and creep strain (P= .614). This invitro study suggests that aging weakens the bone-tendon junction and decreases the ultimate tensile strength of patellar tendon allografts. However, aging did not affect the displacement, strain, stiffness, elastic modulus, creep displacement, or creep strain of patellar tendon allografts. Surgeons should be aware that patellar tendon allografts from donors >50 years of age have a lower ultimate tensile stress than donors ≤30 years of age.

Performance Improvement by Upgrading of the Multi-Field Test Facility of Superconducting Wires/Tapes

A versatile test facility capable of providing cryogenic-electro-magnetic multifield was constructed for field-dependent and mechanical property measurements of superconducting wires/tapes at Lanzhou University of China. It firstly realized a continuous variation of cryogenic temperature from 4.2 K to 77 K (∼5 K/min) and a transport current from 0–1000 A (∼1 A/min) in a background magnetic field of 3.5 T. Aiming at improvements of samples in a larger scope, the facility was upgraded on several sub-systems, for example, the background superconducting magnet, variable-temperature cryogenic and mechanical loading and control system. This paper presents the latest upgrading of the multifield test facility. A semi-open split NbTi magnet with a combined cooling system was newly fabricated to generate a transverse background filed up to 5 T in a relatively larger test space of ∅100 mm × H800 mm. To improve the cryogenic system for refrigeration, a compact cryostat of cylinder-like vacuum Dewar vessel with a visible window, cooled by a Gifford–McMahon (GM) cryocoolers, was constructed. The continuous temperature variations from 4 to 353 K (∼10 K/min) and a high transport current application 0–1000 A (∼3 A/min) for testing superconducting wires/tapes were achieved. Additionally, a data acquisition system with accurate and synchronous measurements of multifield including current, temperature, strain, and AC losses was enhanced. Some tests illustrated that the upgrading of sub-systems and extend of operation range for the test facility were well improved. It will contribute to the progress in understanding design issues for superconducting wires/tapes under intense multiple fields.

A multi-throughput mechanical loading system for mouse intervertebral disc

Mechanical loading plays an important role in maintaining disc health and function, and in particular, excessive mechanical loading has been identified as one of major reasons of disc degeneration. Intervertebral disc organ culture serves as a valuable tool to study disc biology/pathology. In this study, we report the development and validation of a new mouse disc organ culture system by dynamically applying compression loading in a customized micro-culture device tailored for mouse lumbar discs. Precise axial compression force was delivered by a computer-controlled system consisting of a robust micromechanical linear actuator, a force sensitive resistor, and a precision micro-stepping machinery. Customized PDMS-based loading chambers allowed simultaneous loading of six discs per regimen, which streamlined the workflow to reach sufficient statistic power. The detrimental loading regimen of mouse lumbar discs (0.5 MPa of axial compression at 1Hz for 7 days) was demonstrated through live-dead assay, histology, and fluorescence probe based collagen staining. In addition, various mechanical compression profiles were simulated using different materials and geometry designs, potentiating for more sophisticated loading protocols. In summary, we developed a new mechanical loading system for dynamic axial compression of mouse discs, which created a unique avenue to study disc pathogenesis with enriched mouse species-related resources, and complemented the existing spectrum of bioreactor systems predominately for discs of human and large animals.

Direct Torque Control Scheme for a Four-Level-Inverter Fed Open-End-Winding Induction Motor

The main drawbacks of conventional direct torque control (DTC) drives are erratic switching frequency and high torque ripples. The multilevel inverter fed DTC drives are proved to be an alternative for eliminating these drawbacks. Apart from the commonly used three-level inverter fed drives, this paper presents an even-level inverter fed DTC drive. In this paper, a space vector modulated DTC algorithm for a four-level DTC drive is proposed and is implemented by feeding both ends of an open-end-winding induction motor with two-level inverters. The space vector modulation (SVM) algorithm uses a fractal based design for switching voltage vector generation and allied computations are performed in 60 degree co-ordinate system. Representation of vectors as integer values in 60 degree co-ordinate planes avoids fractional arithmetic, which simplifies the algorithmic computations. Detailed analyses of the drive performance under dissimilar operating modes are presented. The loading performance of the drive is experimentally verified on a 5-HP induction motor with a strain gauge type mechanical loading system. No-load experimental results were obtained from a laboratory model 2-HP induction motor drive operated in closed loop mode.

Lateral Response of a Single Pile under Combined Axial and Lateral Cyclic Loading in Sandy Soil

According to practical situation, there have been limited investigations on the response of piles subjected to combined loadings especially when subjected to cyclic lateral loads. Those few studies led to contradictory results with regard to the effects of vertical loads on the lateral response of piles. Therefore, a series of experimental investigation into piles in dense sand subjected to combination of static vertical and cyclic lateral loading were conducted with instrumented model piles. The effect of the slenderness ratio (L/D) was also considered in this study (i.e. L/D= 25 and 40). In addition, a variety of two-way cyclic lateral loading conditions were applied to model piles using a mechanical loading system. One hundred cycles were used in each test to represent environmental loading such as offshore structures. It was found that under combined vertical and cyclic lateral loads the lateral displacement of piles decreased with an increase in vertical load whereas it causes large vertical displacements at all slenderness ratios. In addition, for all loading conditions the lateral, vertical (settlement and upward) displacements and bending moments increased as either the magnitude of cyclic load or the number of cycles increases.

Cover Image, Volume 15, Issue 1

Cover Photograph: Photo of a close‐up view of flame impingement on test coupon inside the combustion chamber with a mechanical loading system. Abhendra Singh, et al. (Figure 3b) image

Simulated Wind Action on Photovoltaic Module by Non-uniform Dynamic Mechanical Load and Mean Extended Wind Load

Taiwan is centrally situated in the main path of typhoons generated in the Northwest Pacific Ocean (19-28° N, 117-125° E). On average in last one hundred years, three or four typhoons approach or make landfall in Taiwan yearly. This typhoon issue has received considerable attention, since the associated strong winds generally damage photovoltaic (PV) modules severely. Previous IEC standards have examined the effect of static (or dynamic) uniform loads for PV module, but did not consider the non-uniform loads due to wind effects on PV modules. In this paper, we develop an analytical model about a mean extended wind load (MEWL) test method, and a non-uniform dynamic mechanical load (NUDML) system, which can simulate the wind action on PV module by uneven mechanical loads. Results of this study revealed that the result of MEWL test strongly rely on the environmental condition of wind velocity, wind direction angle and the inclined angle of the PV module.

Design and operation of a new multifunctional wear apparatus for engine valve train components

The increasingly strict emission regulations in combustion engines are raising high requirements for the engine valve train system. In this paper, a novel multifunctional wear apparatus is designed to study the performance of engine valve train components. The apparatus employs a mechanical loading system, which consists of a special eccentric wheel and disc springs that apply the combustion loads, and the contact configurations and loading conditions of valve train components are simulated. It has three test functions for different components through specifically designed fixtures. The first function aims to evaluate the interaction between the valve seating face and the seat insert at high temperatures and loads. The second function is used to study the friction and wear properties of the valve stem and the valve guide. The third function is designed to evaluate the performance of the valve seals. At last, a verification test was carried out by the proposed experimental method. A pair of new exhaust valve and seat insert is tested for the performance evaluation of the first function. The wear mechanisms acting on the pairs interface are shown to be a combination of oxidative wear, adhesive wear, as well as fatigue flaking.

The establishment of mechanical loading system-induced HT-22 cell injury model

Objective To establish the cell injury model with the mechanical loading system in HT-22 cell lines. Methods HT-22 cell lines were seeded with Bioflex cell plate, and applied with tensile stress-induced cell injury at the degree of deformation of 13.4% and frequency of 1 Hz by FX-5000TFL mechanical loading system. HT-22 cells were divided into control, 6 h, 12 h, and 24 h group, respectively. The mean cell area and thickness were assessed by real-time digital holographic microscopy (DHM), and Trypan blue assay and lactate dehydrogenase (LDH) detected kit were then performed to determine the cell viability and the level of LDH, respectively. Finally, the change of cell cycle and Sub-G1 peak were measured by the flow cytometry (FCM). Results (1) Compared with the control, HT-22 cells showed a reduction in area (from 603.9±28.5 μm2 to 182.9±4.5 μm2,t=21.93, P<0.01) and an increase in thickness (from 4.0±0.2 μm to 8.3±0.3 μm, t=16.65, P<0.01) assessed using the digital holographic microscopy. (2) Cell viability test showed that the cell survival rate of 6 h group (59.7±4.5%) was significantly reduced than that of control group(95.0±1.6%) (t=10.44, P<0.01). Although the cell survival rates of 12 h and 24 h groups were higher than that of 6 h group (t=4.56, P<0.05; t=6.45, P<0.01, respectively), there was also significant difference in cell survival rate between 12 h, 24 h, and control groups (t=7.56, P<0.01; t=3.873, P<0.05, respectively). (3) LDH assay showed that the level of LDH in 6 h group (273.9±4.6 ng/L) was significantly increased than that of control (51.7±5.8 ng/L, t=42.48, P<0.01), while those in 12 h (255.2±4.4 ng/L) and 24 h groups (240.2±6.0 ng/L) were lower than that in 6 h (separately, t=4.14, P<0.05; t=6.28, P<0.01). (4) As demonstrated in flow cytometry (FCM) assay, tensile stress-induced cell injury caused an appreciable accumulation in Sub-G1 phase (6.5±0.6%) compared to that of the control group (0.6±0.3%, t=14.90, P<0.01). However, the Sub-G1 population was decreased with the extension of time, particularly the lowest in the 24 h group (2.1±0.5%) compared to that of the 6 h group (t=9.61, P<0.01). Conclusions In vitro models of traumatic brain injury could be successfully established with the mechanical loading system, and the novel cell injury model in HT-22 cells might serve as a novel useful, effective and controllable approach in developing models of traumatic brain injury. Key words: Craniocerebral trauma; Models; Animal; Mechanical loading system; HT-22 cell lines; Cell injury model

Cyclic tensile strain promotes the osteogenic differentiation of a bone marrow stromal cell and vascular endothelial cell co-culture system

Mechanical stimuli and neovascularization are closely coupled to osteogenic differentiation and new bone formation. The purpose of present study was to detect the effect of cyclic mechanical strain on a co-culture system of bone marrow stromal cells (BMSCs) and vascular endothelial cells (VECs) and to clarify the related mechanisms. Primary BMSCs and VECs were isolated from Sprague-Dawley rats and co-cultured at various ratios (1:0, 1:2, 1:4, 4:1, 2:1, 1:1, and 0:1). To determine optimized loading conditions, the cells were then subjected to various cyclic tensile strains (0%, 3%, 6% and 9%) using a Flexcell 5000 mechanical loading system. A protocol of 6% strain on the co-cultured cells at a 1:1 ratio was selected as the optimized culture conditions based on the best osteogenic effects, which included increased ALP activity, matrix mineralization and the expressions of VEGF, Runx-2 and Col-1. The VEGF-R inhibitor tivozanib was used to analyze the paracrine role of VEGF, and the osteogenesis-promoting effects of 6% tensile strain were abrogated in the co-cultured cells treated with tivozanib. These results demonstrate that cyclic tensile strain promotes osteogenic differentiation in BMSC/VEC co-culture systems, possibly via a VEC-mediated paracrine effect of VEGF on BMSCs.

Mechanical Loading System for Tests on Cross-Flow Turbines

Since large hydraulic turbines already have very good energy performance, nowadays the challenge is to study, improve and construct low power turbines. One important step in the design of a new type of turbine is the experimental study based on adequate equipment. In real-life applications, the turbine is loaded by the electricity consumers. Usually experiments try to reply such conditions, when it is possible and by consequence an electrical loading system seems to be adequate for tests on pico turbines. The present paper focuses on the analysis of an electrical loading system and a mechanic loading system to be used for laboratory experiments on pico turbines. The quality of experiments and the extension of graph area recommend without doubt the mechanic loading system to be used for tests on new pico hydro turbines.

Development of a rig to study model pile behaviour under repeating lateral loads

This paper deals with an important problem of the effect of repeating lateral loads on large-diameter monopile foundations for offshore wind turbine (OWT) structures. The cycles of typically low-amplitude repeating lateral loads and moments generated by various environmental factors are resisted by horizontal earth pressures mobilised in the soil surrounding the pile. Laboratory testing on reduced-scale piles is an efficient and economical way to investigate such pile–soil behaviour. This paper presents the development of a new mechanical loading system to apply many thousands of repeating cycles of lateral load in different forms to a 1g model, with full control provided over the loading direction (i.e. one-way or two-way lateral loading), amplitude, frequency and waveform shape (e.g. sinusoidal, square or haversine). Compared with equivalent setups employing pneumatic or hydraulic actuators, the new loading system is able to produce similar performance at lower cost and also provides more control over the waveform shape. A programme of lateral load tests, each involving many thousands of load cycles, was performed on a rigid model pile installed in dry sand beds to demonstrate some of the main capabilities of the new system.

Test System for Thermoelectric Modules and Materials

We present a design for a complex measuring device that enables its user to assess the parameters of power-generating thermoelectric modules (TEMs) (or bulk thermoelectric materials) under a wide range of temperatures (Tcold = 25°C to 90°C, Thot < 450°C) and mechanical loading (P = 0 N to 104 N). The proposed instrument is able to monitor the temperature and electrical output of the TEM, the actual heat flow through the module, and its mechanical load, which can be varied during the measurement. Key components of our testing setup are (i) a measuring chamber where the TEM/material is compressed between thermally shielded heating blocks equipped with a mechanical loading system and water-cooled copper-based cooler, (ii) an electrical load system, (iii) a type K thermocouple array connected to a data acquisition computer, and (iv) a thermostatic water-based cooling system with electronically controlled flow rate and temperature of cooling water. Our testing setup represents a useful tool able to assess, e.g., the thermoelectric parameters of newly developed TEMs and materials or to evaluate the thermoelectric parameters of commercially available modules and materials for comparison with values declared by the manufacturer.

The Effects of Mechanical Loading on Tendons - An In Vivo and In Vitro Model Study

Mechanical loading constantly acts on tendons, and a better understanding of its effects on the tendons is essential to gain more insights into tendon patho-physiology. This study aims to investigate tendon mechanobiological responses through the use of mouse treadmill running as an in vivo model and mechanical stretching of tendon cells as an in vitro model. In the in vivo study, mice underwent moderate treadmill running (MTR) and intensive treadmill running (ITR) regimens. Treadmill running elevated the expression of mechanical growth factors (MGF) and enhanced the proliferative potential of tendon stem cells (TSCs) in both patellar and Achilles tendons. In both tendons, MTR upregulated tenocyte-related genes: collagen type I (Coll. I ∼10 fold) and tenomodulin (∼3–4 fold), but did not affect non-tenocyte-related genes: LPL (adipocyte), Sox9 (chondrocyte), Runx2 and Osterix (both osteocyte). However, ITR upregulated both tenocyte (Coll. I ∼7–11 fold; tenomodulin ∼4–5 fold) and non-tenocyte-related genes (∼3–8 fold). In the in vitro study, TSCs and tenocytes were stretched to 4% and 8% using a custom made mechanical loading system. Low mechanical stretching (4%) of TSCs from both patellar and Achilles tendons increased the expression of only the tenocyte-related genes (Coll. I ∼5–6 fold; tenomodulin ∼6–13 fold), but high mechanical stretching (8%) increased the expression of both tenocyte (Coll. I ∼28–50 fold; tenomodulin ∼14–48 fold) and non-tenocyte-related genes (2–5-fold). However, in tenocytes, non-tenocyte related gene expression was not altered by the application of either low or high mechanical stretching. These findings indicate that appropriate mechanical loading could be beneficial to tendons because of their potential to induce anabolic changes in tendon cells. However, while excessive mechanical loading caused anabolic changes in tendons, it also induced differentiation of TSCs into non-tenocytes, which may lead to the development of degenerative tendinopathy frequently seen in clinical settings.

Development and application of an experimental system for the study of thin composites undergoing large deformations in combined bending–compression loading

To increase understanding of damage evolution in advanced composite material systems, stereo digital image correlation has been integrated with a compression–bending mechanical loading system to obtain full-field deformations on both compression and tension surfaces throughout the loading process. The integrated system is employed to simultaneously quantify full-field deformations along the length of the specimen. Specifically, the integrated system is employed to experimentally study the progressive failure behavior of thin, woven glass–epoxy composite specimens undergoing both cyclic and monotonic compression–bending loading resulting in large out-of-plane bending deformations with end conditions that allow free out-of-plane rotation. Experimental results obtained using the measurement system for specimens undergoing both linear and highly non-linear deformations during monotonic loading are presented. Results clearly show (a) the presence and magnitude of anticlastic (double) specimen curvature near mid-length for all fiber angles, (b) the distinct differences in the strain fields between the tension and compression surfaces at the critical location, (c) the corresponding disparity in local material failure mechanisms between the tension (e.g. matrix cracking) and compression (e.g. fiber buckling) surfaces in the critical regions and (d) the highly localized character of the strain fields, focused in regions of increased damage.

Design and performance of a skid-mounted portable compartment fire gas furnace and monitoring system

A custom, portable natural gas fire furnace was designed and constructed for use at the University of Notre Dame to experimentally investigate the out-of-plane behavior of full-scale reinforced concrete (RC) bearing walls under fire. The unique aspects of this furnace allowed the application of large mechanical loads and non-contact optical response monitoring to be done while subjecting the wall to elevated temperatures. The performance of the experimental furnace, mechanical loading, and response monitoring system is reported using the results from the first two RC wall test specimens.