Mohammed A. Mousa

Flexural Behavior of Full-Scale Composite Structural Insulated Floor Panels

Panelized systems are prefabricated components that are brought to a construction site and assembled into the finished structure. Traditional constructions are often subjected to termite attack, mold buildups and have poor penetration resistance against wind-borne debris. To overcome these problems, a new type of composite structural insulated panel (CSIP) was developed and is analyzed in this study for structural floor applications. The concept of the panel is based on the theory of sandwich construction. The proposed composite panel is made of low cost orthotropic thermoplastic glass/polypropylene (glass–PP) laminate as a facesheet and expanded polystyrene foam (EPS) as a core. Full scale experimental testing was conducted to study the flexural behavior of the CSIP floor member. CSIP floor panels failed due to facesheet/core debonding. Analytical modeling was further presented to predict the interfacial tensile stress at the core/facesheet interface, critical wrinkling stress, flexural strength and deflections for structural CSIP floor panels. The experimental results were validated using the proposed models and were in good agreement.

Debonding of composites structural insulated sandwich panels

A new type of composites structural insulated panels (CSIPs) is presented in this article. These panels are proposed for structural floor and wall applications. The developed composite panels are made of low-cost orthotropic thermoplastic glass/polypropylene laminate as facesheets and expanded polystyrene foam as a core. CSIPs have a considerably high facesheet/core moduli ratio. The common mode of failure of these panels is facesheet/core debonding. Accordingly, this investigation presents models for interfacial tensile stress and critical wrinkling in-plane stress associated with debonding of CSIPs. The facesheet in compression was modeled as a beam on a Winkler foundation. The proposed models were validated using full-scale experimental testing for CSIPs floor and wall panels. Both type of panels failed by facesheet/ debonding with natural half-wavelength approximately equal to the core thickness.

Performance of Composite Structural Insulated Panels after Exposure to Floodwater

AbstractDegradation of structural material because of floodwater is one of the major damaging effects during flooding events. As a result, thousands of homes in coastal states, especially those that are constructed from wood-based materials, have been destroyed after each severe hurricane. This paper evaluates the performance a new type of composite structural insulated panel (CSIP) after exposure to floodwater. The proposed composite panel is made of low-cost orthotropic thermoplastic glass/polypropylene laminate as the facesheet and expanded polystyrene foam as the core. The proposed CSIP panel is intended to overcome problems of traditional structural insulated panels, especially those resulting from strength degradation. An extensive experimental program was conducted to investigate the flexural strength degradation of CSIPs after exposure to floodwater for various periods of time. The residual flexural strength following full submergence of CSIPs in simulated floodwater was evaluated using a four-poi...

Risk-Consistent Design Approach for Designing Innovative Hazard-Resistant Structures

This paper first introduces an innovative Composites Structural Insulated Panels (CSIPs) for structural wall and floor applications against multiple hazards, and then presents an innovative risk consistent design approach for designing such system. The proposed composite panel is made of low cost thermoplastic orthotropic glass/polypropylene (glass-PP) laminate as a facesheet and Expanded Polystyrene Foam (EPS) as a core with very high facesheet/core moduli ratio. The proposed CSIPs are intended to overcome problems of traditional wood panels against multiple natural hazards including earthquake, flood and windstorm to poor penetration resistance against wind borne debris, termite attack and mold buildups… etc. On the other hand, despite most of recent structures have been designed according to the desired code requirements, failure of those structures due to recent natural hazards such as hurricanes and earthquakes have shown the weakness of the current design methods. It has also raised the need for a new methodology for structural design that accounts for the risk due to natural hazards. Therefore, a comprehensive design approach for developing hazard-resistant structures was developed. The approach considers the life cycle cost (LCC) of the structure and safety indices for strength and drift. It accounts also for the uncertainty in both loading and strength. The variability in the strength, drift and load is expressed by mean values with their coefficient of variance (C.O.V) which is referred to aleatory uncertainty. The LCC was calculated based on the concept of quantitative risk assessment (QRA) that incorporates the damage cost due to a certain hazards and the probability of occurrence of those hazards. Based on the importance and the type of the structure, the structural engineer and the decision maker can determine or optimize the most appropriate building model. The method was demonstrated with case studies on two structures: one for traditional wood and another for CSIP. Seismic and wind hazard were considered in the analysis. Two locations were considered; Los Angeles, CA and Charleston, SC. These locations are critical for seismic and wind load; respectively. The results showed that CSIP building is cost effective and provides higher safety indices than traditional wood structure.

Response of CFRPAAC Sandwich Structures under Low- Velocity Impact

The low velocity impact response of plain autoclaved aerated concrete (AAC) and carbon fiber reinforced polymer (CFRP)AAC sandwich panels has been investigated. The structural sandwich panels composed of CFRPAAC combinations have shown excel¬lent characteristics in terms of high strength and high stiffness-to-weight ratios. In addition to having adequate flexural and shear properties, the behavior of CFRPAAC sandwich panels needs to be investigated when subjected to impact loading. During service, the structural members in building structures are subject to impact loading that varies from object-caused impacts, blasts due to explosions, and high-velocity impact of debris during tornadoes, hurricanes, and storms. Low-velocity impact (LVI) testing serves as a means to quantify the allowable impact energy the structure can withstand, and to assess the typical failure modes encountered during this type of loading. The objectives of this paper are: to study the response of plain AAC and CFRPAAC sandwich structures to low-velocity impact and to assess the damage performance of the panels; to study the effect of CFRP laminates on the impact response of CFRPAAC panels; and to study the effect of the processing method (hand lay-up versus vacuum assisted resin transfer molding) and panels’ stiffness on the impact response of hybrid panels. Impact testing was conducted using an Instron drop-tower testing machine. Experimental results showed a significant influence of CFRP laminates on energy absorption and peak loads of CFRPAAC panels. A theoretical analysis was conducted to predict the energy absorbed by CFRPAAC sandwich panels using the energy balance model. Results found were in good accordance with the experimental data.

Use of Quantitative Risk Assessment in Structural Design

Civil engineers, in particular, have the primary responsibility for the design and planning of civil structures, including protective systems to minimize losses of lives and economies during extreme hazard events. Structural failures in recent earthquakes and hurricanes have exposed the weakness of current design procedures and shown the need for new concepts and methodologies for building performance evaluation and design. Although the uncertainty of seismic load has been well recognized by the profession, the incorporation of uncertainty in most building code procedures have been limited to the selection of design loads based on return period. To strike a balance between the possible high initial cost and potential large losses over the structure’s lifetime, the life-cycle cost and the uncertainty in the hazards and system capacity need to be carefully considered. Moreover, to strictly enforce performance goals, the target probabilities need to be set directly for the limit states rather than for the design earthquake or hurricane etc. Therefore, the total cost over the life time of the structure should be considered when optimizing the design for natural hazard. The future or damage cost of the structure due to natural hazard is calculated based on quantitative risk assessment (QRA). This paper presents a methodology for the design optimization based on the QRA. A case study for a three story residential wood building is presented in order to demonstrate the concept.