David C. Weggel

Recycled brick masonry aggregate concrete

Purpose – Reuse of construction and demolition (C&D) waste as aggregates is becoming increasingly popular for a number of environmental and economic reasons. The purpose of this paper is to explore this topic.Design/methodology/approach – In this study, structural‐ and pavement‐grade portland cement concrete (PCC) mixtures were developed using crushed recycled brick masonry from a demolition site as a replacement for conventional coarse aggregate. Prior to developing concrete mixtures, testing was performed to determine properties of whole clay brick and tile, as well as the crushed recycled brick masonry aggregate (RBMA), and a database of material properties was developed.Findings – Concrete mixtures exhibiting acceptable workability and other fresh concrete properties were obtained, and tests were performed to assess mechanical properties and durability performance of the hardened concrete. Results indicated that recycled brick masonry aggregate concrete (RBMAC) mixtures can exhibit mechanical properti...

Crash analysis and evaluation of cable median barriers on sloped medians using an efficient finite element model

Abstract Perpetual high traffic volumes on U.S. highways have raised more public concern than ever about transportation safety. Over the years, various traffic barrier systems, including cable median barriers (CMBs), have been developed to reduce the number and severity of vehicle crashes. Despite their general effectiveness, there remains room for improvement, especially when CMBs are installed on unlevelled terrains such as sloped medians. The destructive nature of crashes imposes significant challenges to barrier design using full-scale physical testing; numerical simulations thus become a viable means to support crash analysis, performance evaluation, and barrier designs. In this study, validated vehicle and CMB models were used to perform full-scale simulations of vehicle-CMB impacts. Several CMB designs, including the currently used one, were evaluated under vehicular impacts at different velocities and angles. To address the challenge of modeling slender members such as cables and hook-bolts in contact analyses, an efficient beam-element contact model was employed in the analysis. Different design options of cable height and spacing under various impact velocities and angles were investigated in this study.

Structural Identification and Damage Characterization of a Masonry Infill Wall in a Full-Scale Building Subjected to Internal Blast Load

AbstractStructural identification continues to develop an expanding role within performance-based civil engineering by offering a means to construct high-fidelity analytical models of in-service structures calibrated to experimental field measurements. Although continued advances and case studies are needed to foster the transition of this technique from exploration to practice, potential applications are diverse and range from design validation, construction quality control, assessment of retrofit effectiveness, damage detection, and lifecycle assessment for long-term performance evaluation and structural health monitoring systems. Existing case studies have been primarily focused on large civil structures, specifically bridges, large buildings, and towers, and the limited studies exploring application to damaged structures have been primarily associated with seismic events or other conventional hazards. The current paper produces the first experimental application of structural identification to a compo...

Use of Recycled Brick Masonry Aggregate and Recycled Brick Masonry Aggregate Concrete in Sustainable Construction

Use of recycled aggregates in portland cement concrete (PCC) construction can offer benefits associated with both economy and sustainability. Testing performed to date indicates that recycled brick masonry aggregate (RBMA) can be used as a 100% replacement for conventional coarse aggregate in concrete that exhibits acceptable mechanical properties for use in structural and pavement elements, including satisfactory performance in some durability tests. Recycled brick masonry aggregate concrete (RBMAC) is currently not used in any type of construction in the United States. However, use of RBMAC could become a viable construction strategy as sustainable building practices become the norm. This paper explores the feasibility of use of RBMAC in several types of sustainable construction initiatives, based upon the findings of previous work with RBMAC that incorporates RBMA produced from construction and demolition waste from a case study site. A summary of material properties of RBMAC that will be useful to construction professionals are presented, along with a discussion of advantages and impediments to use. Several quality assurance and quality control techniques that could be incorporated into specifications are identified.

Blast Testing of Cold-Formed Steel-Stud Wall Panels

AbstractCold-formed steel-stud walls have been utilized as an attractive option for blast-resistant design due to the combination of high strength and ductility that enable them to absorb and dissipate blast energy through large deformation kinematics. However, achieving the available ductility of the steel studs requires special attention to the stud-to-track connection details, which has remained an active area of research and development. While much of the existing literature has described specialized ideal boundaries to ensure that the full tensile membrane response of the studs would be achieved prior to connection failure, the research reported in this paper examines the blast performance of cold-formed steel-stud walls with commercially available connections and bridging. Experimental results from a series of three open-arena blast tests of identical cold-formed steel-stud wall panels are presented. Distortional buckling of the studs around unstiffened punchouts in the web as well as web crippling ...

Experimental Modal Analysis of a Prestressed Concrete Double-Tee Joist Roof Subject to Blast

Prestressed concrete has received increased attention as a structural system for blast resistance and protection. However, prestressed concrete members not intentionally designed to resist blast loads, as well as connections to such members, may be especially susceptible to blast initiated damage. Full-scale testing of a prestressed double-tee joist roof in an industrial building was conducted both prior to and after internal detonation of a modestly sized explosive charge located approximately six feet below the base elevation of the double-tee joists. The testing included experimental modal analysis of the roof using a pair of long stroke electrodynamic shakers and a distributed network of 60 accelerometers. A large set of modal parameter estimates are extracted from the measurement data using a combined stochastic-deterministic subspace identification algorithm. Comparisons are made to a numerical model of the roof, developed using properties obtained from supplemental nondestructive evaluation and local historic design handbooks, to assess the plausibility of the modes. Differences in the natural frequencies and mode shapes are highlighted to qualitatively draw conclusions on plausible damage to the roof system alongside physical observations from the site.

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF GLASS CURTAIN WALLS SUBJECTED TO LOW- LEVEL BLAST LOADS

A series of three full-scale, nearly-conventional, curtain wall specimens were blast tested in the open arena of the Infrastructure Security and Emergency Responder Research and Training (ISERRT) Facility in Gastonia, NC. The specimens were subjected to low-level blast loads produced from the detonation of high explosives. Low-level blast loads, similar to those produced during the tests, are typical of small charge weights (i.e. satchel charges) at short-to-moderate standoffs. A simple finite element (FE) model that effectively represents the nonlinear dynamic response of glass curtain walls subjected to blast loads was developed, and simulation results were compared with the test results. It was shown that, with the judicious choice of modeling parameters, the FE model effectively represents the response of glass curtain walls subjected to blast loads while being computationally economical. The calibrated FE model was used to evaluate the efficacy of a nonlinear single-degree-of-freedom (NSDOF) design expression for analytically approximating the blast resistance of curtain wall systems. The design expression is based on a procedure in which a nonlinear resistance function of the system is input to an energy expression that models the maximum nonlinear dynamic deflection due to an ‘impulsive’ loading. It was shown that the maximum impulse predicted by the design expression, when the expression was used in conjunction with a satisfactory resistance function, compared reasonably well with the FE simulation results. The expression could be used as a starting point for design or to supplement more advanced models of curtain walls subjected to blast loads.

Structural Identification Using the Applied Element Method: Advantages and Case Study Application

Structural identification has continued to develop into a versatile tool for developing high fidelity analytical models of large civil structures that accurately reflect the measured in-service response. The results of successful structural identification have been applied to validate the performance of innovative systems and improve assessments of response analysis for operational and extreme loads. Furthermore, the developing field of vibration-based damage detection has sought to employ structural identification for long-term performance monitoring and condition assessment of aged structures. Overwhelmingly, the finite element method has served as the analytical framework for such models. However, alternative physics engines, such as the Applied Element Method, offer distinct advantages over the finite element method both with respect to the computational considerations in the identification process and with respect to the use of the calibrated model for assessment of structural response to extreme loads. A general framework for structural identification with applied elements is discussed, and advantages are contrasted with traditional finite element approaches. A case study application, a prestressed concrete double-tee joist roof tested in a full-scale building, is presented to demonstrate the approach and emphasize these advantages.

Closed-Form Solution for a Cantilevered Sectorial Plate Subjected to a Tip Bending Moment

AbstractA closed-form solution is presented for a cantilevered sectorial plate subjected to a tip bending moment. Deflections from this solution are compared with those from a finite-element analysis and are found to be in excellent agreement. Closed-form normalized deflections and slopes at the fixed support resulting from an approximate enforcement of the boundary conditions there deviated from zero by less than 0.04%.

EXPERIMENTAL PROGRAM AND SIMPLIFIED NONLINEAR DESIGN EXPRESSION FOR GLASS CURTAIN WALLS WITH LOW-LEVEL BLAST RESISTANCE

A series of fi full-scale, nearly conventional, curtain wall specimens was tested in the UNC Charlotte Structures Laboratory. Specimens were subjected to quasi-static, uniform, out-of-plane loading to failure under displacement control. The tests were performed to obtain complete resistance curves, including the nonlinear behavior of the specimens up to ‘ultimate failure’. Ultimate failure was defi ned as mullion fracture or signifi cant breach of the curtain wall system when viewed as the protective barrier between building occupants and the external blast load. Representative load-defl ection and loadstrain resistance curves are presented. The energy absorbed by the curtain wall system up to three different limit states ‐ fi rst cracking of glass, fi rst yield of mullions, and fracture/breach of the system (ultimate failure) ‐ and maximum mullion end rotations are computed from the experimental results. Ultimate energy absorption capacity ‐ the recoverable linear strain energy plus the nonlinear energy due to formation of damage mechanisms ‐ and maximum mullion end rotations are essential for reliable and economical design of blast resistant curtain walls. To this end, a simplifi ed methodology is presented for analytically approximating curtain wall resistance functions that can be input to an energy expression that models nonlinear structural dynamic behavior due to an ‘impulsive’ loading. The blast resistance of a curtain wall can then be approximated using this procedure. It is shown that a nearly conventional curtain wall, a conventional system with two modifi cations ‐ use of laminated glass lites that are structurally glazed (wet-glazed) to a conventional framing system with structural silicone sealant ‐ had nearly 14 times the ultimate energy absorption capacity and nearly four times the blast resistance as the fully conventional system.