Structures Congress 2017: Blast, Impact Loading, and Response of Structures

The research focuses on the dynamic performance of girder bridges and the applicability of cable-sliding friction bearing subjected to blast load and earthquake. In order to accomplish this, numerical simulation and scale model test are performed. In numerical simulation, two seismic waves combing with blast load of 450kg TNT are applied to the girder bridge separately by using software LS-DYNA. After analyzing the area of damage and longitudinal displacement, results show that the most remarkable displacement change of main girder appears when blast occurs at the time that seismic response arrives at the maximum value. Based on the existing research, cable-sliding friction bearing is suggested to be adapted. Next, scale model test is conducted considering two different damping bearing systems and three series of tests are performed to verify the effectiveness of the cable-sliding friction bearing system. The data collected from the test shows that the bearing could prevent beam falling and therefore improve the safety of girder bridges.

Multiple blast tests were conducted on RC slabs at the Science and Technology Aerospace Department in Brazil. This paper presents the description of the experimental test set-up, instrumentation and results from a sub-set of the tests conducted on four 60 MPa concrete slabs with reinforcement ratios of 0.25% in two-way. In addition, one of the four slabs was retrofitted with 50 mm thick foam to determine if the foam has the capacity to reduce the blast response of the slab. The slabs were simply supported on two sides and the explosive was detonated at 2 m stand-off distance. The explosive charge was non-confined C4 plastic explosive cylinder. The equivalent TNT mass of the explosive ranges by 2.6-2.76 kg. Accelerometers, displacement and pressure gages were used to measure blast wave parameters and global response of the slabs. A high-speed digital camera in conjunction with a rugged notebook was used to capture images. Both qualitative and quantitative results are included. The foam on slab 3 varied the pattern of pressure recorded by the sensors and induced higher displacement, acceleration and linear momentum.

The inland waterway system in the United States is fundamental to the transportation system as a whole and the success of the nation’s economy. Barge transportation in these waterways levitates congestion on the highway system and is beneficial when comparing barge transportation to the other modes of freight transportation in the measures of capacity, congestion, emissions, and safety. Unavoidably, the highway system intersects with the waterways, resulting in the risk of vessels collision into bridge structures. Particularly for barge impact, the interaction between barge and bridge pier is neglected in the AASTHO guidelines. In this study, the bridge-pier impact problem is investigated by performing a set of 3D finite-element simulations. For this purpose, a detailed model of a jumbo hopper barge is developed with the necessary details in the bow. The barge model is validated for its response to impact into rigid piers of different size and shape. Furthermore, the elasticity of the barge, a measure of the kinetic energy before and after the collision, is calculated to evaluate the strength and behavior of the barge model. The elasticity of the barge is expressed in terms of coefficients of restitution. Regression formulas are derived to estimate the coefficient of restitution as a function of the pier to barge width ratio and the initial kinetic energy. The analysis results, including the impact force and relationship between barge crush depth and kinetic energy, are compared with the AASHTO guidelines. This is expected to provide an evaluation of the sufficiency of the current design guidelines and performance requirements.

Alternative load path analysis (ALPA) is becoming the most common technique for performance based design of structures to resist disproportionate collapse. This has coincided with an increased ability of high fidelity numerical analysis tools validated by experimental work. This paper presents the results of analysis of reinforced concrete flat plate subsystems tested at the University of Missouri and modeled using the applied element method. The experiment analysis shows the importance of modeling membrane action of slabs when performing alternate load path analysis. The results also show that is important to take into consideration brittle failure modes such as the punching shear failure of slabs and the debonding of deformed steel bars.

A new methodology to design against disproportionate collapse is proposed for critical building that must be operational after a terrorist attack. The disproportionate collapse analysis uses the alternate path method where the structure has to be designed to support the applied loads when a column is removed from the building. In some cases when columns are close to each other, the blast pressure can damage more than one column. The new methodology can identify the number of columns or vertical load bearing components that should be removed in a disproportionate collapse analysis. Then, an alternate load path analysis is to be performed using the applied element method for the cases where one or more vertical load bearing components fail to match the actual risk level for critical structures and provide consistent design benchmarks. The applied element method is an optimized numerical technique which allows the analysis to be completed within a time-frame that is practical for design professionals. The method also allows the designer to choose the required resilience or the acceptable degree of risk based on the actual performance of the structure and the amount of acceptable damage under the effects of extreme loading events.

Vapor cloud explosions in industrial facilities are often followed by a fire event, which can expose surrounding structures to elevated thermal loads. In the chain of events: (1) a release of flammable gas engulfs a congested or confined area; (2) the cloud ignites generating overpressure loads on surrounding structures; and (3) the release continues burning and produces heat loads that can further compromise the structural integrity of surrounding structures. This paper presents an investigation on the effects of blast-induced permanent deflections on the behavior of load-bearing steel components subjected to thermal loading. A simple analytical model for steel columns subjected to axial loads forms the backbone of the study. In this model, temperature-dependent strength and stiffness of structural steel are defined using degradation factors specified in the AISC (2010) and Eurocode 3 (2006) standards. The analytical model is validated against finite element models of axially loaded steel columns having different heights, section properties, and temperature-dependent material properties. Using the analytical model, a parametric study is further performed assuming increasing levels of permanent deflections in the columns to assess how second order moments affect the critical buckling loads of steel columns at elevated temperatures. The parametric study shows how the choice of blast design response criteria for load bearing elements can be critical in determining the structural performance in the event of fire after the explosion.

The use of insulated precast/pre-stressed (PC/PS) concrete and insulated tilt-up concrete sandwich panels for exterior walls is common practice. The sandwich wall systems provide resistance over a large deformation range, making them useful for blast resistance. To develop blast design guidelines for these systems, it is first necessary to develop static resistance functions which are experimentally verified. In this paper, three sandwich panel systems were experimentally and numerically analyzed, including walls with symmetric concrete layers, un-symmetric concrete layers, and symmetric concrete layers with truss girder and pre-stressed strands. Nonlinear 3D FE models were created to analyze the static response of these wall systems for reliable dynamic response predictions. Material and geometric nonlinearities were modeled in this research for all the wall components. Foam-concrete interface and stud anchor load displacement behavior were in included in the FE models. The numerical models showed good correlation with the experimental results.

Progressive collapse performance of steel structure with unreinforced masonry wall and load-bearing wall structure with concrete masonry unit (CMU) have been investigated through field experiments and computational simulations. During the experiments, single or multiple first-story columns or load bearing walls were physically removed from the buildings, which were demolished immediately after the experiments. Due to lack of full-scale building test data, the data produced in this research has been a valuable addition to the state of knowledge on gravity collapse of buildings. The primary goal of field experiments was to simulate the structural dynamic and static response of buildings that may experience collapse after sudden loss of column(s) or wall(s). Another objective was to investigate how the internal forces were redistributed within the building after each wall or column was removed. In this study, finite element models of the buildings were developed and analyzed to simulate the building performance and collapse potential. Computational models and simulations were examined and compared to the experimental data from the field tests. The contribution and effects of infill walls to progressive collapse resistance of frame structures were investigated. This study showed the robustness of existing buildings and the contribution of different structural components to collapse resistance.

Records have shown that bridges designed in accordance to conventional standards are usually unable to resist blast loading. Bridges serve great importance in modern day transportation system as they also form part of the skylines of cities, but the increasing act of terrorism around the world has made these valuable assets vulnerable to attack. This research studies the response of a reinforced concrete bridge pier conventionally designed and subjected to blast loading. Non-linear finite element method using a commercial software LS-DYNA which is capable of simulating real blast scenario problems of large deformations with the aid of Arbitrary Lagrangian-Eulerian simulations and fluid-structure interaction is used. The conventionally designed pier was subjected to near ground blast loading by varying the charge weight and stand-off distance while keeping the axial load constant. The mode of failure of the pier is observed for peak displacement and residual displacement. The results obtained were used to propose methods of retrofitting and repairing the conventionally designed bridge piers to support combined gravity (axial) and blast loading.

Indoors explosive testing is carried out inside bunkers known as explosive test chambers. Typically, such facilities are constructed of thick, heavily reinforced concrete walls lined with steel plates. View ports are incorporated into the chamber structure for monitoring the blasting events. Damage to the steel liner plate occurs due to direct blast loading, impact by airborne fragments, and potential oxidation reactions. High speed airborne fragments might penetrate through the liner steel plates and into the outer concrete shell of the chamber. Damage of this type could compromise the structural integrity of the bunker. This article presents the methodology developed to design such facilities. This methodology is initiated by designing the test facility under direct blast loading. The second phase of the design will consider probabilistic fragmentation impact over the life of the facility. Fragmentation characteristics are identified using methodologies developed by U.S. Army TM 5-1300, NATO AASTP 1, and AC/258-D/258. The probabilistic fragmentation analysis identifies the potential fragment size distribution and impact velocity. Binomial distribution analysis is utilized to establish probabilities of multiple fragments hitting the same spot over the life span of the facility. Higher number of hits is associated with lower probabilities and more conservative design. Based on their risk management approach, facility operators might accept a lower risk by designing for higher number of hits or vice versa. The outcome of the probabilistic analyses was used to generate high-fidelity, physics-based, three-dimensional finite element models to simulate fragment impacts with the proposed structural design. For the analytical simulations, the performance of the structure is investigated when impacted by several projectiles as identified earlier.

In events of manmade or natural hazards, local structural members may be destroyed or removed and loads created by the failure structural members may be redistributed within the structure. If the capacity of structural components is exceeded by additional loads, the progressive collapse of the structure may occur. Infill walls behave as equivalent compressive struts and change the load redistribution path of frame buildings in progressive collapse scenarios. In this paper, progressive collapse mechanisms of frames with infill walls designed according to Chinese building codes are investigated by using nonlinear dynamic analyses. The deformation and internal forces under first story column removal scenarios are presented in this study. The implications and design schemes of frames with infill walls are discussed correspondingly.

ISO shipping containers and other conventional portable buildings (such as wood-framed trailers) are widely used in petroleum refining and chemical processing facilities. Given that these structures may be subjected to blast loading in the event of an accidental explosion at these facilities (amongst other hazards), their location is typically subject to industry guidelines. In order to better predict the response of example portable buildings to blast loading, full-scale blast load tests were performed. Full-scale structural response tests were performed on an ISO shipping container and a blast resistant wood building (BRWB), both subject to blast loading. The blast loading applied to the test articles was generated with a deflagration load generator (DLG) test rig. The DLG test rig can produce centrally-peaked blast waves that are representative of full-scale vapor cloud explosions (VCEs) in industrial settings. During a test, the DLG test rig is outfitted with congestion and filled with a near-stoichiometric fuel-air mixture which is ignited near the center of the rear wall. By controlling the congestion level and standoff distance between the test rig and the test article, the desired blast load on the target structure can be achieved. The ISO shipping container and BRWB were subjected to two tests with increasing overpressure and impulse. The first test had a target free-field blast overpressure of 2.0 psig (13.8 kPa), which was selected to cause an appreciably low level of damage to the structures. The damage observed in both structures following the first test was minor; however, significant displacement of internal items was observed. The second test was performed with a higher blast overpressure near 5.0 psig (34.5 kPa), in order to push the structures to a higher damage level to fully exercise their structural response. The damage observed in both structures following the second test was significant, including the generation of debris caused by rapid displacement of the internal items in both structures. This paper documents the testing performed, focuses on the response of the BRWB to the test blast loads, and also provides a comparison to standard single-degree-of-freedom structural component models, which are frequently used in the design and assessment of buildings that are subject to accidental blast loads.

Structural steel framing members subjected to blast loading respond initially in flexure followed by tension membrane as deflection increases. If member connections have been adequately designed and detailed, those members can achieve large deformations and achieve significantly greater load capacity in tension membrane than can be developed in flexure only. The applied load and large deformation of the member produce a tensile axial force that must be resisted by both the member and corresponding connections. With rigid connections, the normal-to-plane deformations cause elongation of the member. Even a small axial elongation along the component axis can produce significant tensile forces. If a portion of the axial deformation could be relieved by incorporating flexibility of the connections, the resulting axial force in the member and the force demand on the connections can be reduced. Moreover, similar concepts used while designing the component are required for the connection design such as: strength, stiffness, ductility, especially if a ductile failure mode in the component is expected. Ample research has been done to study semi-rigid connection behavior during conventional loading. However, there is limited research of connections for members subjected to blast and impact loading. Recently, the University of Alberta has performed research on the behavior of shear connections (SC) of structures subjected to progressive collapse loading. Although this research evaluated response with a lower strain rate effect than typically occurs with blast loading, the connection test data is valuable for model development. Currently, there is no comprehensive blast standard or guideline for design of connections in components subjected to blast load. This paper presents a multi-degree of freedom (MDOF) approach to compute the overall response of a steel member subjected to blast loading, including the component (with large deformation) and connections. Connection models proposed by the University of Alberta are incorporated in the MDOF tool. This MDOF approach can predict a more realistic response of the system subjected to blast loading than provided by typical single-degree-of-freedom (SDOF) approaches, which ignore connection flexibility.

Progressive collapse is global structure performance, which involves all the stories above a removed column. However, previous experimental research work is more concentrated on single-story sub-structures or assemblies, mainly due to the concerns of cost and safety issues. In engineering practice, how to translate the research results of single-story sub-structures into multi-story structures becomes more interesting and urgent for engineers to design or rehabilitate structures against progressive collapse. In this paper, a planar and a three-dimensional reinforced concrete (RC) frames are modeled with fiber-based plastic hinges for nonlinear static analysis. The numerical models are initially validated by the experimental results of RC framed sub-structures, and then are used to investigate whether the load transfer mechanism of each story in a multi-story building subjected to progressive collapse is the same, and identical to the one obtained from a single-story substructure test. The parameters to be studied include loading positions, boundary conditions, the number of spans, explicit modeling of slabs.

Steel bracing has proven to be one of the effective methods to upgrade lateral load resistance of reinforced concrete (RC) frames. However, little studies had been carried out on the efficiency of steel bracing for improving the behavior of RC frames in resisting progressive collapse. In this paper, the effects of steel bracing on the behavior of RC frames in mitigating progressive collapse are investigated experimentally. One bare frame without bracing and two braced frames with additional steel bracing in the third floor are tested. It is found that steel braces could increase the first peak load up by 126.9 % while the braces has little effects on the catenary action in large deformation stages. In general, the eccentric bracing system is performed better than the concentric one.

ASTM, FM, and UL provide standards for hail impact resistance of roofing systems, including equivalent projectile sizes, travel distances, and kinetic energies representing hail impact loads for testing of roofing materials. However, there currently is no standard method for design or evaluation of structural elements subjected to hailstorm loading. This case study presents a simple means of dynamic hail impact load analysis for precast concrete plank roof elements at a subject building. The frequency and magnitude of hail impacts were conservatively estimated using statistical methods, based on an observed level of roofing material damage following a specific hailstorm event. The precast concrete planks were modeled in CSI SAP2000 software, and the dynamic response of the planks was then evaluated through time history analysis. It was concluded that the loading experienced by the precast concrete planks subjected to hail impacts was marginal compared to their ultimate load carrying capacity.

Blast response limits have traditionally been used for predicting the level of protection that structural components provide to buildings susceptible to explosion effects. These limits are usually derived from a combination of post-incident damage indicators, test data, and supporting dynamic analysis. Such limits do not exist for load-bearing prestressed wall panels, largely due to the lack of available full-scale test data. This paper presents design response limits for load-bearing prestressed concrete wall panels based on a series of full-scale shock tube tests and dynamic analysis. The panels tested included 6-inch thick solid prestressed concrete panels and prestressed concrete insulated panels with 3-inch thick wythes separated with two inches of rigid insulation. Static axial loads were sustained on the top of the panels in the dynamic shock tube tests, ranging from 5 and 10 percent of the gross static axial capacity of each wall. The proposed limits are intended for use with non-linear single degree of freedom analysis methods.

The Defense Threat Reduction Agency (DTRA) has been developing software to investigate explosive effects on buildings and other assets for over twenty years in order to protect people and missions from terrorist effects. A modeler may have limited time and limited building information to determine the outcome of certain vulnerability scenarios; therefore, automated building design and fast-running engineering models (e.g. airblast and structural collapse) are essential. The need to model more complex buildings, as well as large urban environments, is rapidly growing. This trend has driven improvements to both automated building design as well as fast-running engineering modules that leverage the building model. This paper investigates the current state of automated building design and the engineering modules in vulnerability analyses, as well as suggested paths forward.

Alternative load path analysis is the primary approach for evaluating the potential for disproportionate collapse in structural design. In this approach, individual load-bearing elements are notionally removed from a structure, and the remaining structure is required to sustain the applicable gravity loads without collapse. Column loss in steel and reinforced concrete frame structures can result in large vertical deflections that subject the beams and their connections to significant axial deformations in addition to large rotations. Failure of members and connections in alternative load path analysis is evaluated by comparing the plastic rotations of these components to acceptance criteria, defined as rotation limits, based largely on data from seismic tests. Axial demands on members and connections, which are important in column loss scenarios, were not relevant in this seismic testing, and thus the corresponding rotation limits may not be appropriate for column loss. This paper compares current acceptance criteria for alternative load path analysis with experimental data reported in the literature under column loss scenarios for steel gravity frames with single-plate shear connections and for reinforced concrete moment frames. Significant variability is observed in the level of conservatism of these acceptance criteria, and factors contributing to this variability are discussed. A new approach for defining acceptance criteria is summarized, which provides improved risk-consistency by directly accounting for the interaction of axial and rotational demands on the connections under column loss scenarios.

This paper presents alternative load path analysis of a 5-bay by 5-bay, 10-story prototype reinforced concrete moment frame building under column loss scenarios. This prototype building is used for example analysis problems in the Alternative Load Path Analysis Guidelines, which are being developed by the Disproportionate Collapse Technical Committee of the Structural Engineering Institute, and the analyses presented in this paper have been submitted for inclusion in these guidelines as part of the chapter on advanced numerical modeling. The prototype building was designed for seismic design category C, for a location in Atlanta, GA. Intermediate moment frames were selected as the lateral force-resisting system and were designed in accordance with the requirements of the American Concrete Institute 318 Building Code. A two-way concrete slab was used at each floor level, including the roof. Using a reduced-order finite-element modeling approach, full-building analyses are presented under three different first-story column loss scenarios, including a corner column, an edge column, and an interior column. Results from nonlinear dynamic analysis (i.e., sudden column removal) are compared with results from nonlinear static analysis (i.e., push-down analysis) using an energy-based procedure to account for the dynamic effects of sudden column loss. The robustness index for the building is also evaluated based on its ultimate capacity under the same set of sudden column loss scenarios.

Conventional reinforced concrete (RC) structures have historically been the choice for blast and impact resistant structures. Experimentally validated equations to calculate the required wall thickness of RC walls to prevent scabbing and perforation exist and are included in NEI 07-13 and DOE-STD-3014-2006. Steel-plate composite (SC) walls consist of a concrete core sandwiched between two steel faceplates, and have recently been incorporated into power plant designs in several countries. The steel faceplates serve as reinforcement and formwork, which allows for modularization of the design and accelerated construction. SC walls inherently prevent scabbing and, based on the available experimental database, Bruhl et al. (2015) provided a three-step process to design SC walls to resist projectile perforation. This method was designed to be conservative based on a database of experimental and numerical investigations. This paper introduces an experimental program that was designed to further evaluate local impact behavior of SC walls, and confirm the design method. Several test have been planned to investigate the influence of parameters such as the faceplate thickness & strength, tie bar diameter & spacing, and projectile diameter, weight and velocity. This paper provides an overview of the experimental program and results from an initial set of tests. These preliminary results suggest that the experimental approach is promising.

Steel-plate composite (SC) walls can provide excellent resilience for impactive and impulsive loading. This is due to their design, which consists of a concrete core sandwiched between two steel faceplates. The perforation resistance of SC walls for missile impact can be evaluated using a three-step method available in the literature. If perforation is prevented, other failure modes such as punching shear failure, excessive deflections, and steel plate fracture failure due to extensive yielding must be checked. Currently, there are no methods or guidance available in the research or design literature for checking these failure modes. This paper presents the results of numerical investigations which evaluate the failure modes of SC walls. A total of 80 detailed numerical models were developed and analyzed to investigate the effects of wall design parameters and boundary conditions. This paper only includes a selection of the total study and is focused only on evaluating shear failure not the other possible failure modes. The numerical results indicate that there are three failure modes other than perforation: (i) brittle shear failure, (ii) ductile flexural yielding followed by fracture of ties, and (iii) highly ductile plastic mechanism formation. The minimum shear (tie bar) reinforcement ratios required to change the failure mode from punching shear to flexural yielding to plastic mechanism formation are discussed.

On Wednesday, April 1st, 2015, Utility Service Company, Inc. (USCI) received an email from the Town of Lovettsville, VA with a photo showing a vertical rupture in the north west column of the town’s 75,000 gallon elevated water tank and an urgent request for emergency service. To provide a comprehensive review of possible issues, USCI’s Engineering Department requested additional information including drawings, additional photos, etc. In the interim, the water tank was drained and taken out of service. On Friday, April 3rd, the Town of Lovettsville forwarded a structural inspection and analysis report completed by KCI Technologies in December 2008. With that information, USCI’s Engineering Department was able to better understand the tank’s structural integrity and narrow down the possible sources of the problem. On Tuesday, April 7th, a team led by Donnell Duncan, P.E., S.E., Professional Structural Engineer, visited the tank site and completed the forensic investigation. The investigation and resulting repair consisted of the following main steps: Step One: Identifying the Problem; Step Two: Diagnosing the Cause of the Problem; Step Three: Locating the Source of the Problem; Step Four: Emergency Repairs; and Step Five: Long Term Repair.

The failure of wood roof members in older buildings is a fairly common occurrence compared to systems built of steel or concrete. The slow-working detrimental effect of sustained loading at relatively high stress levels (i.e., “creep rupture” or “cumulative damage”) is typically viewed as the predominant failure mechanism, but this is not always the case. The following describes a case study of a glulam beam that failed for other reasons. The subject glulam beam that failed absent a significant atypical loading event was one of many in the roof structure of a large building. Each glulam beam was about five feet deep and 100 feet long. At the time of failure, the subject glulam beam was 41 years old. Through the course of the investigation, significant research was performed into multiple aspects of glulam beam behavior, including revisions to design stresses over time, fabrication technology, and time-dependent properties. Detailed field observations were performed to document the failed beam, the surrounding elements, and the assemblies supported by the roof framing. The cause of the failure was ultimately found to be a fabrication error.

This paper explores the question “What is the appropriate level of investigation when conducting a structural building condition review?” Certainly, the premise of the review is a factor - be it to assess the building prior to its purchase, to consider its repurposing or rehabilitation, or to address a concern about a symptom, such as wall cracks or other apparent structural distress. But in most cases an overarching purpose is to increase the level of confidence in a building’s future ability to structurally perform its intended function. What is our obligation to our clients to accomplish this end? The protocol for a condition review of a structure is frequently limited to a set of observations to determine if there is any visually apparent evidence of distress, damage, or deterioration. Yet some structures have hidden defects, created either in design or construction, that represent capacity limitations that analysis would show could be conditions of high overstress under service loads. Such hidden structural limitations have led to sudden collapses. When should further analysis be considered when conducting a condition review? The author proposes a decision matrix which takes into account more than visually apparent signs of structural deficiency in an existing building, in order to more reliably develop an opinion of future performance.

Following the record-breaking 2014–2015 winter snow events in the Greater-Boston and Southern New Hampshire area, the federal emergency management agency (FEMA) building science branch deployed an assessment team to assess building performance of four schools whose roofs had failed and developed conclusions and recommendations about the effects of this snow event based on their observations. This paper summarizes the team’s observations of building damage and structural performance problems caused by localized snow drift loading. FEMA concluded that the observed roof systems were under-designed in comparison to current snow load requirements, which include snow drift loads. The full report, Snow Study Summary Report, Observations of Snow Load Effects on Four School Buildings in New England, may be downloaded here: (http://www.fema.gov/media-library/assets/documents/124838).This paper compares the estimated roof snow loads to the corresponding design loads per American Society of Civil Engineers (ASCE) ASCE 7-10, Minimum Design Loads for Buildings and Other Structures, and recommends future activities such as developing high-level guidance for structural engineers and building owners/operators to mitigate losses resulting from snow loads.

It is important in damage investigations conducted after building failures that the expected resistance of the building system or component that failed be compared to the loading condition. When the resistance (R) is less than the load (L), then failure can occur. An investigator must be able to predict with some accuracy the load that exceeded the resistance and thus caused the failure. This effort is based largely on probability theory given the unknowns that exist for both the resistance and the loads. One of the important unknowns is how much resistance may have been lost due to age and/or deterioration and how much was lost during initial construction. Basing the resistance levels for existing buildings on new materials and high quality installation does not represent a real set of conditions, so investigators need a way to consider construction quality, age and deterioration. In load and resistance factor design, both loads and resistances are modified with factors. These factors are intended to represent the likelihood that loads will not occur at their maximum value or continue at near maximum values for extended time frames and that resistance might be provided by under-strength members due to variations in material strengths and dimensions. The resistance factor varies with the purpose of the member or connection (i.e. tension, compression, bending). There are no known resistance modifiers that account for construction quality, age or deterioration. This paper will describe an elicitation method used to evaluate the expected reduction in resistance to a series of systems or components due to initial construction in the field, age, and deterioration. The reductions in resistance are compounded since the initial loss of resistance due to initial construction errors cannot ever be recovered, thus when age and/or deterioration occur, the resulting resistance reduction is the product of the reduced resistance caused by other factors. The elicitation method was used for a hurricane loss estimation model prepared by the expert panel appointed by the Texas Department of Insurance (TDI) for use by the Texas Windstorm Insurance Association. The paper will describe the seven elements considered in TDI’s model, the six factors considered for initial construction resistance reduction as well as age and deterioration resistance losses that could occur in four elements over 25 years in 5 year increments. This method could be used for any type of construction and for any set of expected resistance reduction factors based on the materials used, the construction type considered and the effects that both age and deterioration have on the material resistances. TDI’s study is the first of this type found by the author during an extensive literature search, and may help fill an important gap in what is known about the effect of initial construction quality, age and deterioration on resistance to loading conditions.