Ali M. Memari

Full-scale dynamic testing of a steel frame building during construction

Abstract Full-scale testing of a six-story steel frame building with infill walls made primarily of autoclaved cellular concrete and curtain walls made of hollow core clay bricks using ambient and forced vibration methods are described in detail. The ambient vibration test took place in two stages of the construction—stage one, when only the frames and slabs where constructed, and stage two when all the walls were put in place. The forced vibration was carried out when some of the walls were constructed. The results from the two test methods are compared with each other and also with computer analysis results based on conventional design office assumptions for modeling. Dynamic characteristics of the structure including natural frequencies, damping ratios and mode shapes determined from the tests are presented. The effect of Autoclaved Cellular Concrete (ACC) block infill and partition walls on the dynamic properties and stiffness of the building are discussed in detail. The advantages of using ACC block walls as infill wall material for seismic regions are concluded.

Architectural Glass Panels with Rounded Corners to Mitigate Earthquake Damage

The concept of employing architectural glass panels with modified corner geometries and edge finish conditions to improve their resistance to earthquake damage has been developed recently. To accomplish this, material is removed at glass panel corners (e.g., by rounding the glass corners) and glass edges are finished in the modified corner regions to minimize protrusions and edge surface roughness. The concept is applicable to a wide variety of architectural glass types and glazing frame types. Full-scale dynamic racking tests have shown that corner radius and glass edge finish conditions near the reshaped corner regions have significant influences on glass cracking and glass fallout drift resistances of monolithic architectural glass panels used in curtain walls.

Seismic Performance of Two-Side Structural Silicone Glazing Systems

This paper presents the results of the first phase of an experimental research program on simulated seismic performance of structural silicone glazed (SSG) curtain wall systems. Full-scale, two-side SSG mockups made up of three side-by-side glass panels were tested under cyclic racking displacements to determine serviceability and ultimate behavior responses. Variables were glass type (annealed and fully tempered) and panel configuration (monolithic, laminated, and insulating glass). In the experiments carried out, damage states such as gasket deformation/pullout, sealant failure (e.g., adhesion/cohesion, etc.), glass cracking glass and fallout were identified and their corresponding drift levels were determined. The extent of damage to silicone sealant was determined through air leakage tests.

Dynamic Racking Performance of an Earthquake‐Isolated Curtain Wall System

Dynamic racking tests, coupled with air leakage tests, were performed on fullsize specimens of a new, Earthquake-Isolated Curtain Wall System and a widely used, conventional curtain wall system (used as an experimental control). Dynamic racking tests simulated seismic movements that could be imposed upon a curtain wall system as a result of interstory drifts. Air leakage tests were performed as an indicator of serviceability performance of both curtain wall systems during the dynamic racking tests. The Earthquake-Isolated Curtain Wall System demonstrated strongly superior performance in terms of both serviceability (glass cracking and air leakage) and life safety (glass fallout). The conventional system exhibited vulnerability to annealed monolithic glass cracking and glass fallout at dynamic racking drift indices of 1.9% and 3.1%, respectively. No glass damage was observed in the earthquake-isolated system up to the dynamic racking displacement limit of the test facility, which corresponded to a drift index of 4.9%. Air leakage rates through vision panels in the conventional system remained constant up to a drift index of 1.9%, after which the air leakage rates increased rapidly. In contrast, air leakage rates through vision panels in the earthquake-isolated system remained unchanged up to the 4.9% drift index capacity of the test facility.

Seismic response of a new type of masonry tie used in brick veneer walls

Abstract One of the concerns with the conventional metal anchors that are used to tie the brick veneer to the backup portion of enclosure walls (e.g. masonry block) is the potential for corrosion. Corrosion reduces the load carrying capacity of such ties and this could lead to brittle failure especially in the event of an earthquake. In this paper, the forces in lateral ties in a typical brick veneer wall system are evaluated when the building is subjected to some earthquake records. Distribution of tie forces resulting from the dynamic analysis of a finite element model of the brick veneer-masonry block wall system are determined and compared to the conventional assumption. The performance of a corrosion resistant stainless steel helical tie is compared with that of conventional masonry ties. The potential advantages of this relatively new type of masonry tie are discussed with respect to its use in seismic regions.

Product Architecture Model for Multistory Modular Buildings

AbstractThe modular building construction method is the industry’s effort for industrialization of building construction. Similar to other types of production, a product information model is required for lifecycle information management of modular buildings. In this research, the mutual hierarchy of typical multistory modular systems is identified and represented in a product architecture model (PAM). This provides the industry with an information model required for industrial design of this type of construction. Since modular construction is neither as heavily project-based as conventional construction methods nor as significantly mass-produced as manufactured products, none of the current information management frameworks in manufacturing and construction industries are necessarily capable of addressing the needs of such projects. In the research reported here, this need is addressed by development of a product PAM for the most conventional modular systems. The PAM represents the hierarchy of modular bu...

Seismic Racking Test Evaluation of Silicone Used in a Four-Sided Structural Sealant Glazed Curtain Wall System

This paper presents the results of a study in which four-sided structural sealant glazing (SSG) insulating glass curtain wall units were subjected to cyclic racking test methods in accordance with AAMA 501.6 testing protocols. The test configuration included three side-by-side primary units and a corner unit. High-resolution cameras were utilized to capture instantaneous images during the racking test so that the displacement within the sealant joint could be captured and isolated from the displacement of the entire glazed unit. Drift capacity of the system in terms of glass attachment and sealant performance is reported in detail for different levels of racking displacements and boundary conditions. The overall behavior of the system is characterized, and specifically the sealant performance at a corner condition during racking drift is discussed. Additionally, expected strains in the sealant were calculated using a linear-elastic finite element model and were then compared with the strains the actual structural sealant joint underwent during system testing. Silicone sealant damage was evaluated using visual observation before and after cyclic racking. The paper discusses proposed acceptable sealant stress levels for seismic design and the durability of silicone used in the SSG system as compared to dry-glazed systems based on glass performance.

Seismic Performance of Stick-Built Four-Side Structural Sealant Glazing Systems and Comparison With Two-Side Structural Sealant Glazing and Dry-Glazed Systems

A research project was undertaken to study the simulated seismic performance of mock-ups of a full-scale, four-side structural sealant glazing (SSG) system. “Stick-built” mock-ups were subjected to cyclic racking displacements in accordance with the American Architectural Manufacturers Association (AAMA) 501.6 test method. Although the test method focuses on glass fallout, drifts associated with serviceability damage states, such as sealant adhesive or cohesive failure, and glass cracking were also identified during the conduct of the tests. Damage to sealant joints was tracked as a function of drift level using visual and video inspections of weather-seals and structural-seals and air-leakage tests. Data from this study are compared with data collected from similar studies on comparable two-side SSG and dry-glazed mock-ups. Contact with panels diagonally above and below a given glass panel at panel corners was found to be the likely cause of initial sealant damage, glass cracking, and glass fallout as opposed to glass-to-frame interactions for two-side SSG and dry-glazed curtain-wall constructions. Thus, modified corner geometries and/or joint dimensions can be used to delay (i.e., shift limit states to higher drift levels) or avoid these damaging panel interactions. Mock-up specimens were also instrumented extensively so that real-time glass-panel translation and rotation, and weather-seal deformation measurements could be recorded. A summary of these measurements is presented and discussed in the context of their follow-up use for informing the development of damage prediction models for SSG curtain walls during seismic loadings. The study shows that stick-built curtain walls with four-side SSG configuration are expected to have higher drift capacity compared to two-side SSG and both are expected to have higher drift capacity compared to dry-glazed configurations.

Information Exchange Standardization for BIM Application to Multi-Story Modular Residential Buildings

Proper information exchange and integration of different project phases are the two fundamental needs of the construction industry. Building Information Modeling (BIM) has had a significant effect on the construction industry during the past decade. Modular building industry can potentially take advantage of BIM at least as much as site-built construction where most of the BIM application is. However, currently there is no specific standard or BIM platform for modular constructions. As a result, the integration level of information in this industry is relatively low, and this increases the project costs and complexity. This article will present a method to standardize the information exchanges for this type of construction. In the proposed methodology, first the product information will be organized; this will be done by developing the Product Architecture Model (PAM) for modular buildings. Then, a hierarchy of the physical assemblies and sub-assemblies of the building and corresponding modules will be developed, followed by assignment of nonphysical properties and attributes of each element. Next, an Information Delivery Manual (IDM) will be developed based on the National BIM Standard (NBIMS) method and the proposed PAM. The last step would involve development of Model View Definitions (MVDs) for different information exchanges at different phases of the project and between different disciplines based on the IFC file format data structure. Use of the IFC data structure for standardization of information exchanges will result in a highly interoperable BIM platform that could be used in a wide range of BIM software.

Seismic evaluation of an existing reinforced concrete framed tube building based on inelastic dynamic analysis

A seismic assessment of an existing 32-story reinforced concrete framed tube building is performed using inelastic dynamic time-history analysis to obtain force and deformation response of the structure subjected to three ground motion records. Details of the modeling based on the DRAIN-2D program, plastic rotation, rotation and curvature ductility demands and capacity evaluation of members are discussed. Recent recommendations for plastic hinge rotation and plastic hinge length modifications are discussed and the results of the application of some of these recommendations are evaluated. Some observations with regard to shear lag effect are presented and some of the difficulties in using the direct results of inelastic dynamic time history analysis in seismic assessment for practical applications are demonstrated.