Characterization of adobe wall structural systems for dynamic response
Authors:   , Robert Stephen Douglas 
Published: April 2021

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Adobe building construction exists around the world. Most of the adobe structures are located in active seismic zones, and a considerable amount of research has been conducted on the seismic response of adobe structures. Protocols and standards for adobe structural analysis, design, and construction has been established to ensure quality assurance and structural stability. The vulnerabilities to seismic loadings have been established, and research and design of seismic retrofits for existing and new adobe construction have been conducted. The type of retrofit utilized can depend on the availability of materials, impact on the aesthetics of the structure, and region of the world that the structure exists. Very limited research exists on the structural response of these structures when subjected to an external blast load. This dissertation evaluates current adobe wall designs for blast resistance and provides recommendations for their blast retrofits. Although limited research has been conducted on the effect of blast loadings on adobe structures, it is possible that some seismic retrofit designs can be extended to enhance the blast resistance of adobe structures. The result would provide a multi-hazard retrofit that includes resistance to blast and seismic loadings. Research has been conducted to evaluate adobe blocks, adobe block component specimens, and adobe block walls. The adobe block testing provides material properties such as block compressive strength, modulus of rupture, shear strength, and mortar strength. These properties are important when analyzing the component and conducting wall testing research. The static adobe block-mortar bond shear strength and flexural strength of a column of adobe blocks subjected to bending were determined through research on adobe block component specimens. Research efforts also investigated the strength and failure modes of unreinforced and reinforced full-scale adobe block walls. Slender walls, referred to as wallettes, are the same height and approximately one-third the width of the full size adobe walls that were tested. The wallettes were tested in a four-point bending setup to determine the load capacity, deflection, and failure mode. The effect of wall thickness was determined by testing three unretrofitted wallettes of varying wall thicknesses of 10, 20Â¾, and 31Â½ in. A retrofit concept, with two variations, was applied to the 20Â¾-in. wallettes to determine their performance in increasing the load capacity, change the failure mode, and increase the stability of adobe block walls. The unretrofitted 20Â¾-in. wallette served as the baseline to evaluate the retrofitted wallettes. This research effort was extended to investigate full-scale unretrofitted and retrofitted adobe walls statically tested in a vacuum chamber. The vacuum chamber applies a uniform loading on the adobe block walls. A pretest compressive load was applied to the top of the wall and maintained during the test. The dead load of the roof that adobe walls typically support is represented by this compressive load, which is achieved through five 4Ã—4 timber rafters that are connected to the top of the wall. Two unretrofitted and three retrofitted 10-in.-thick adobe block walls were tested. The loaddeflection curve and failure mode of the each wall were determined. Additionally, three unretrofitted 10-in.-thick adobe block walls were dynamically tested in a blast load simulator (BLS), located at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS, to determine the dynamic responses of adobe block walls to blast loadings. The walls were constructed with the same adobe blocks and mortar as in the static testing phase of the research, and a similar compressive load and system was used in the BLS tests. The experimental research will assist in developing blast resistant design methods for adobe walls and retrofits. The wallette tests results were analyzed to determine loaddeflection curves for the wallettes and if the curves could be used to assist in dynamic analyses of adobe walls of other thicknesses. The load-deflection curves gathered from the vacuum chamber provided experimental resistance functions for unretrofitted and retrofitted adobe block walls. Single-degree-of freedom (SDOF) analysis uses the resistance functions and can also be used to predict the responses of adobe walls to dynamic loads. The dynamic adobe block wall tests provide a reference of how well the SDOF analysis predicts the dynamic responses of adobe block walls. Additionally, the retrofit techniques provide guidance for retrofitting adobe block walls to sustain dynamic blast loads.