The present study focuses on the evaluation of the static and dynamic behavior of cementitious sandwich panels with parallel steel wire shear connectors. The study is divided into two parts: (i) large-scale experimental evaluation of different structural sandwich members subjected to different types of loading regimes, and (ii) analytical procedures to predict the behavior of such panels. However, and due to the lack of experimental data on the behavior of such sandwich panels, the emphasis of this study is on full-scale experimental evaluation. In the analytical part of the study, modified procedures, based on the experimental observations, following the general guidelines of the American Concrete Institute (ACI 318-11) were adopted. Also, the experimental program focused on assessing the out-of-plane flexural behavior of floor/roof sandwich slabs. Both simply supported and two-span continuous large-scale floor/roof slabs, with different boundary conditions and details, were evaluated. The experimental results were compared to the analytical predictions and well agreement between the results was achieved. The study also included several large-scale element experiments that were conducted on walls subjected to axial, shear, eccentric and flexural loadings conditions as well as exterior and interior corner connections. These tests are considered to be a pioneering research work that are not available to-date in published literature. A summary of the test setup, test procedures and experimental results that included quasi-static and cyclic load-displacement (P-δ) and Stress- Strain (σ−ε) curves are presented and discussed herein.

The comprehensive experimental program provided much needed information to the structural engineers that lack the knowledge on the service and ultimate performance of this type of sandwich structural elements. For example, the experimental results provided important information on the suitability of the sandwich panels with parallel wire connectors for the use as floors and roof slabs. In addition, the experimental results identified the different failure modes that are not similar to those for solid concrete elements.

The simplified analytical procedures that followed, in general, the requirements of ACI 318-11 with justifiable modifications succeeded to provide conservative estimates to the capacity of each structural sandwich element evaluated in this study. Numerical design examples for typical residential buildings that were performed using the proposed analytical procedures are also presented.

Conclusions drawn from this pioneering study is summarized and recommendations for future research work is presented in this thesis.

ABSTRACT OF THE THESIS

Experimental Evaluation of Two-Way Sandwich

Paneled Slabs

By

Surbhi Dadlani

Master of Science in Civil Engineering

University of California, Irvine, 2015

Professor Dr. Ayman S. Mosallam, Chair

This research focuses on the experimental evaluation of the flexural behavior of light-weight two-way slabs made of three-dimensional (3D) sandwich panels subjected to out-of-plane loading. The sandwich panels evaluated in this study were composed of two exterior faces made of high-strength mortar reinforced with bidirectional cold-rolled steel wires. The sandwiched core consists of fire retardant Expanded PolyStyrene (EPS) foam core. In this study, three square large-scale sandwich slab specimens with different dimensions and spans were subjected to mid-span loads up to failure. All specimens were instrumented with electrical strain gages and string potentiometers to monitor steel and mortar strain variations and deflections. During each experiment, loads, strains, and vertical deflections were monitored and the results were analyzed. Load-deflection (P/) and stress-strain () curves were also developed for each specimen at different locations. Cracks initiation and propagation were monitored throughout each test and crack mapping was performed for each slab specimen. Peak load, ultimate strain, and maximum vertical displacement were observed and the failure load for each specimen was identified and recorded. A simplified analytical procedure that followed the requirements of ACI 318-14 was developed to provide conservative estimates of the capacity of each structural sandwich slab evaluated in this study. Experimental results were compared with the predicted capacity and deflection of each sandwich slab specimen and a good agreement was achieved in the linear range.

With millions of poor and homeless people in the world and the presence of extensive bamboo resources in many regions, a part of the affordable housing problem can be solved by providing structural design for bamboo houses. In this study, structural evaluation of a bamboo arch was performed. In addition, a numerical finite element model using ANSYS software was developed to simulate the behavior of the bamboo structure. The study included a literature review of relevant published technical papers, books and reports. Experimental tests were conducted on the full-scale bamboo structure to verify the scissor action of joints to transfer load and to study the short-term creep behavior for controlling the deflection limits to satisfy the building standards as per CBC 2013. The finite element model was used to understand the expected behavior of the bamboo arch structure under gravity loading. The finite element model results were used to determine the possible improvement to stiffen the structural joints by using steel cables. This study is just a step towards providing an alternative for feasible housing design using bamboo as a structural material.

The thesis focuses on the experimental, analytical and finite element modeling results of structural evaluation of hybrid LDPE/FRP composite beams. Two composite reinforcement details were evaluated in this investigation. In addition, results of axial tensile and compression coupon tests to characterize the short-term mechanical properties of LDPE/FRP matrix are presented and discussed. Test results of two large-scale beam specimens subjected to quasi-static four-point loading are discussed. Results obtained from the experimental tests showed that due to the hybrid nature of the beam specimens and the viscoelastic/elastoplastic behavior of the LDPE matrix, flexural stiffness of the two beams were dependent on the stress level as well as on the loading rate as expected. The change in the stiffness can also be attributed to the initial cyclic loading that was performed up to 10 kips (44.5 kN) which typically will result in a slight permanent set similar to the typical behavior of other construction materials including similar reinforced concrete members. Due to the absence of ASTM and Caltrans procedures for experimentally calculating the flexural stiffness of these hybrid beams, the flexural stiffness was calculated at different loading level. The behavior of the specimen was linear up to about 80% of the ultimate load, after which the behavior became non-linear up to the ultimate load. In all tests, no failure or cracks were observed in the plastic matrix, and the governing mode of local damage could be observed in the form of relative slippage of the FRP rebars at the ends, especially the top compressive reinforcements that resulted in stiffness degradation. The maximum load for the tests was limited by the maximum actuator stroke. An analytical model developed by Mosallam (2005) is described and verified with the experimental results. In addition finite element models were developed for different beam geometry and results are discussed. Conclusions and recommendations for future research in this area are also presented.

The main goal of this research study is to evaluate the structural behavior of symmetric and asymmetric built-up composite columns subjected to lateral loading. The composite columns were made up of two outer layers of high-strength structural mortar with three-dimensional welded-wire space truss incorporating diagonal cross wires welded to welded wire reinforcement (WWR) on each side of a fire retardant Expanded Polystyrene (EPS) foam inner core. This study deals with the experimental investigation and methodology carried out for the fabrication and testing of these built-up columns with the EPS sandwich panels. The peak load, maximum strains and horizontal displacements of each of the specimens were obtained and the different failure modes were identified and recorded.

This thesis also presents the detailed output of the nonlinear 3-D finite element analysis of the composite columns modeled using ANSYS. The numerical analysis results were comparable with the experimental results and were conservative. The conclusions from the experimental test results were drawn and the scope for future research work is also discussed.

This dissertation presents the details of the findings of a study focused on evaluating the structural behavior of three-dimensional (3D) cementitious sandwich panels with Expanded Polystyrene (EPS) foam core for two-way slab applications. In this study, both theoretical and finite element numerical analysis procedures were adopted to predict the performance of such slabs under out-of-plane loading conditions. The results from theoretical and finite element analysis were verified by comparison with full-scale laboratory tests conducted at the Structural Engineering Test Hall (SETH). The sandwich panels evaluated in this study comprise of expanded polystyrene foam sandwiched between high-strength mortar faces reinforced with cold-rolled steel wires in two directions. Two analytical methods were utilized in characterizing the flexural behavior of the sandwich slabs; mainly (i) Yield Line Theory, and (ii)finite element modeling using MARC-MENTAT software. In the finite element (FE) model, the concrete facings of the panel modeled using quadrilateral plate elements, whereas steel wire mesh is represented by beam elements. The FE model was analyzed by nonlinear static analysis. Numerical FE results are compared with experimental data to validate the numerical approach used. Based on the results of this research, it was concluded ix that a simple MARC finite element model can be used to analyze the flexural behavior of these sandwich panels for two-way slab applications. Analytical results using FEA show good correlation with the experimental results. Furthermore, recommendations for future research in this area are presented.