Blast-Retrofit of CMU Walls Using Steel Sheets

Abstract

Blast resistant design has come to the forefront of engineering concerns in the wake of recent terrorist threats to the United States. Safety and security are of utmost concern when designing structures, and there has been a significant rise in the demand of researching new methods of reinforcing and retrofitting structures to provide better resistance to blast loading. The focus of this research paper is on the use of steel sheathing as a method of such retrofit. Research is done to ascertain the steel strength, analyze the response of the steel to static pressure, explore strength and ductility limits, investigate connection details, and develop an analytical model of the static resistance function, which will be verified by experimental data. The analytical model for the resistance function will be used in a single-degree of freedom (SDOF) dynamic model to predict the response of steel sheathing blast-retrofitted wall systems.Coupon tests were performed to establish the stress-strain behavior of the steel material, and component beam tests were used to determine the response of the sheathing under static pressure. In addition, connection methods were analyzed and tested in an effort to determine the most suitable blast-retrofit design for a given blast, without exceeding strength or ductility limits for the steel sheets, and to develop the limit states for the retrofit system. The results of the experimental program and the analytical static and dynamic models were incorporated into a user-friendly wall analysis code for the design of steel sheathing for blast retrofit of CMU walls.

Blast resistance of membrane retrofit unreinforced masonry walls with flexible connections

“…This method starts by formulating the deflection using geometric properties and then correlating the change in length to strain and stress to determine the corresponding pressure loading. This method was compared to experimental results, including works by Lane (2003), Fitzmaurice et al (2006), Salim et al (2006), Johnson et al (2009), and Hoemann et al (2010). Assuming a parabolic shape, the general form of the deflection is represented by…”

“…The deflection at midspan corresponds to a cubic root relationship and was derived assuming that the membrane acts as a slender cable that develops tension due to transverse loading. Young's formula was implemented by Salim et al (2006) for the wall retrofit application. Seide (1977) presented a method for defining the resistance of elastic membranes supported on four edges that assumes that all edges are straight with negligible in-plane shear stress.…”

“…Lane assumed that steel studs subjected to lateral pressures deflect in a parabolic shape and developed a method to solve for the arc length of the stud. This method involves incrementing the deflection and calculating the new arc length of the retrofit and was subsequently used by Fitzmaurice et al (2006), Salim et al (2006), and Johnson et al (2009) and was referenced by Hoemann et al (2010) for the masonry retrofit application.…”

Resistance of Concrete Masonry Walls with Membrane Catcher Systems Subjected to Blast Loading

“…At the onset of crack (y = 0), the problem is reduced to two equations (Eqs. (11) and (12)) and two unknowns, D and p. As crack grows (y > 0), D is calculated using Eq. 5, and p is subsequently calculated using Eq.…”

“…With similar objectives as the work presented herein, Salim et al [12,13] presented resistance functions derived from static load experiments of several different membrane retrofit materials. The resistances included the flexibility of the anchors and connections used to connect membrane retrofit to the floor and roof of host structures.…”