Publications

2023

1. Out-of-Plane Flexural Behavior of Insulated Wall Panels Constructed with Large Insulation Thicknesses

   Jacob Luebke, Fray F. Pozo-Lora, Salam Al-Rubaye, and 1 more author

   Materials, 2023

   Abs

   Insulated concrete sandwich wall panels (ICSWPs) are gaining popularity as energy regulations become stricter worldwide. ICSWPs are now being constructed with thinner wythes and thicker insulation to keep up with the changing market, which is reducing material costs and increasing thermal and structural efficiency. However, there is a need for adequate experimental testing to validate the current design methods for these new panels. This research aims to provide that validation by comparing the predictions of four different methods with experimental data obtained from six large-scale panels. The study found that while current design methods adequately predict the behavior of thin wythe and thick insulation ICSWPs within the elastic region, they do not accurately predict their ultimate capacity.

2022

1. Behavior of Hybrid Reinforced Concrete Bridge Decks under Static and Fatigue Loading

   Jared W. McRory, Fray F. Pozo-Lora, Zachary Benson, and 2 more authors

   Polymers, Nov 2022

   Abs

   This paper presents a new bridge deck reinforcement alternative using hybrid reinforced concrete (Hybrid) consisting of Glass Fiber Reinforced Polymer (GFRP) rebar and alkali-resistant fiberglass composite macrofibers added to the concrete mixture. Fiberglass composite macrofibers are a miniaturized GFRP reinforcing bar that is a composite of resin and glass fibers. An experimental testing program and analytical modeling were conducted to evaluate the structural performance at the service and ultimate limit states. Thirteen full-scale bridge deck specimens were constructed and tested under static and fatigue loading. The fatigue loading was applied up to two million cycles at a frequency of 4 Hz. Post-fatigue, the specimens were tested to failure to compare pre-and post-fatigue behavior. Simplified and moment-curvature analytical models were used to predict the specimens’ flexural strength at the ultimate level, and both were found to be accurate for predicting pre- and post-fatigue strength. Deflection and crack width were monitored throughout the fatigue loading, and these values were compared to the recommended AASHTO LRFD serviceability limits. Testing and analytical results showed that the Hybrid deck is a viable alternative to steel-reinforced and GFRP-reinforced bridge decks for flexural behavior. The service and ultimate level behavior of each bridge deck type was adequate as compared to the AASHTO LRFD service limits. The exceptional post-peak energy absorption demonstrated by the Hybrid adds ductility to previously elastic GFRP reinforced sections.

2. Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels

   Fray F. Pozo-Lora, and Marc Maguire

   JoVE, Nov 2022

   Abs

   This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete sandwich wall panels (ICSWPs). Such a standardized test does not exist, but several iterations of this and similar tests have been performed in the literature to varying degrees of success. Further, the tests in the literature are rarely-if ever-described in detail or discussed at length with respect to the testing, data analysis, or safety procedures. A test specimen configuration is recommended herein, and variations are discussed. Important mechanical properties are identified from the load versus displacement data, and their extraction is detailed. The use of test data for design, such as for determining the stiffness of the connectors, is briefly demonstrated to show how ICSWP deflection and cracking behavior may be calculated. The strength behavior of panels may be determined using the full load versus displacement curve or only the maximum connector strength. Shortcomings and unknowns are acknowledged, and significant future work is delineated.

2020

1. Partially Composite Concrete Sandwich Wall Panels

   Marc Maguire, and Fray F. Pozo-Lora

   Concrete International, Nov 2020

   Abs

   Design of insulated concrete wall panels (ICWPs) resides outside of the current building code provisions. The behavior of an ICWP is largely a function of the wythe connector stiffness and strength. Using the percent composite analogy, designers of partially composite ICWPs can follow the design process for a solid wall. However, they must be aware of the limitations of this approach and the various factors that affect the panel deflections and stresses when subjected to service and design loadings.

2. Thermal bowing of concrete sandwich panels with flexible shear connectors

   Fray Pozo-Lora, and Marc Maguire

   Journal of Building Engineering, May 2020

   Abs

   Thermal bowing, often referred to as bulging or out-of-plane wall deflection, is a common issue in sandwich panel walls caused by a temperature differential between a building’s interior temperature and the outside environment. This paper aims to better understand the thermal load response of concrete sandwich wall panels. Fundamental mechanics related to thermal bowing are developed and presented when using standard flexible shear connectors. A relatively simple set of equations are then presented for use in design and verified using full-scale models. Finite element analyses are also performed and compared to the developed sandwich beam theory. This study concludes that current design practices used for solid panels provide an inaccurate prediction of the bowing value because of the nature of force and deformation variations on panels subjected to thermal gradients. The concrete stresses, shear connector forces, and panel deformations result in a non-linear relationship with geometric properties and a linear one with properties of concrete and thermal force.

2019

1. Lumped GFRP star connector system for partial composite action in insulated precast concrete sandwich panels

   Brandon Cox, Parker Syndergaard, Salam Al-Rubaye, and 3 more authors

   Composite Structures, Dec 2019

   Abs

   This paper introduces a novel composite shear connectors system used to transfer interface shear forces in a precast concrete sandwich panel. The shear connectors consist of non-proprietary non-composite commercial glass fiber reinforced polymer (GFRP) pin connectors that are laid out in a star pattern and clustered at the top and bottom of the panels. The testing program consisted of thirty-four push-off, twenty-three pullout, and eight full-scale flexural specimens was conducted to evaluate the structural performance of the new shear connectors. The effect of concrete wythe thickness, insulation wythe thickness, and concrete compressive strength was investigated throughout these tests. Additionally, the effect of bond between insulation and concrete wythes was investigated using push-off tests. The flexural test results were compared with predicted fully composite, non-composite, and partially composite values to evaluate the overall panel performance. The comparison showed satisfactory performance with a lower bound of 90% composite action for specimens with 100 mm thick insulation wythe and full composite action for most panels with 50 mm thick insulation. Idealized shear load-slip curves were also developed that account for various parameters to assist design engineers in designing insulated sandwich wall panels with the proposed shear connectors system.