Halil Sezen

Reinforcement Slip in Reinforced Concrete Columns

Reinforcement slip in footings and beam-column joint regions can make a significant contribution to the total lateral displacement of a reinforced concrete structure. In this paper, a model for the prediction of lateral deformation of a column due to reinforcement slip in the anchorage zone is presented. The model employs a stepped bond stress along the embedded length of the reinforcing bar that allows for efficient computation of displacements due to slip. A method for computing slip when a reinforcing bar is stressed to its unloaded end and a corresponding failure criterion are presented. Procedures for calculating slip in hooked bars are also outlined. The proposed model is compared with five other commonly-used models found in the literature against three independent sets of test data. Considering its simplicity and computational efficiency, the proposed model predicts slip displacements reasonably well.

Seismic Tests of Concrete Columns with Light Transverse Reinforcement

Earthquakes and laboratory experience show that columns with inadequate transverse reinforcement are vulnerable to damage including shear and axial load failure. To study this behavior, four full-scale columns with light transverse reinforcement were tested quasistatically under unidirectional lateral load with either constant or varying axial loads. Test results show that responses of columns with nominally identical properties vary considerably with magnitude and history of axial and lateral loads. Observed behavior is compared with expected behavior based on available analytical models. The FEMA 356 assessment model predicted the column strengths well, but underestimated the displacements.

Model for the Lateral Behavior of Reinforced Concrete Columns Including Shear Deformations

This research is focused on modeling the behavior of reinforced concrete columns subjected to lateral loads. Deformations due to flexure, reinforcement slip, and shear are modeled individually using existing and new models. Columns are classified into five categories based on a comparison of their predicted shear and flexural strengths, and rules for combining the three deformation components are established based on the expected behavior of columns in each category. Shear failure in columns initially dominated by flexural response is considered through the use of a shear capacity model. The proposed model was tested on 37 columns from various experimental studies. In general, the model predicted the lateral deformation response envelope reasonably well.

GRAVITY LOAD COLLAPSE OF BUILDING FRAMES DURING EARTHQUAKES

Earthquake reconnaissance has identified failure of reinforced concrete columns as a primary cause of collapse of older existing reinforced concrete structural frames during earthquakes. Apparent column failure, however, does not always result in structural collapse. This paper describes a study of columns tested in the laboratory and examines loss of lateral and vertical load capacities. Correlations with geometric materials and loading characteristics are identified.

Sustainable Structural Design Methodologies

Modern society is demanding that the use of energy associated with construction and operation of structures be investigated during the planning and design phases. The engineering community has been striving to design more sustainable buildings in an attempt to reduce both raw material requirements and energy use during all phases of design. Structural engineers currently have very limited guidance on how to incorporate sustainability concepts in their designs. Innovative methods are needed to address the environmental impact, energy use, and other sustainability issues faced during planning and design of buildings. This paper investigates and discusses five sustainable structural design methodologies: Minimizing Material Use, Minimizing Material Production Energy, Minimizing Embodied Energy, Life-Cycle Analysis/Inventory/Assessment, and Maximizing Structural System Reuse. The goal of this paper is to describe and address issues associated with the proposed design methodologies to determine which, if any, ...

Seismic performance of masonry buildings during the 2007 Bala, Turkey earthquakes

A field investigation was conducted near the town of Bala after two strong earthquakes struck the region on December 20 and 27, 2007. The main objectives of this study are to present the results of the field investigation and examine the characteristics of the recorded ground motions and the corresponding response spectra. The focus of the research was on the causes of damage and failures commonly observed in masonry structures. This study classifies single family masonry dwellings in rural areas and investigates the seismic damage in unreinforced masonry structures. Turkish Earthquake Code requirements for masonry buildings are summarized and compared with the field observations. Our field investigation showed that there has been lack of quality control and regulation for the masonry construction. Diagonal shear cracking and out-of-plane failure were the two major factors that contributed to widespread damage in masonry structures.

EVALUATION AND COMPARISON OF SURFACE MACROTEXTURE AND FRICTION MEASUREMENT METHODS

Abstract Two- and three-dimensional macrotexture characteristics of various surfaces were measured using five different testing methods including sand patch method, laser profiler, laser texture scanner, circular texture meter, and x-ray computed tomography (CT) scanning. A dynamic friction tester was also used to measure the friction resistance of the same surfaces. Asphalt and Portland cement concrete samples of various mix designs and finishes and other commonly manufactured textured samples were used. Relationship between the macrotexture and friction was investigated. Mean texture depth (MTD) of 26 laboratory specimens was obtained from volumetric sand patch tests. Two-dimensional profiles and mean profile depth (MPD) of specimens were measured by a laser profiler. A laser texture scanner and a circular texture meter were also used to calculate the MPD of sample surfaces. Three-dimensional rendering of the surfaces were obtained from laser texture scanner and x-ray CT scans. Using the experimental da...

Load-Rating Procedures and Performance Evaluation of Metal Culverts

Load-rating factors are used to evaluate the service life or safety of culverts based on the culvert wall strength and soil cover depth over the culvert. Current culvert load-rating methods have deficiencies in identifying potential critical conditions of corrugated metal culverts. Current load-rating procedures do not provide explicit guidance to the engineer for load rating and evaluation of culvert condition. To ensure good performance over the design life, corrugated metal culverts must be designed and regularly evaluated using an effective load-rating method. The main objective of this study was to investigate the effectiveness of current load-rating procedures. Recommendations are made to improve the analysis and evaluation procedures for corrugated metal culverts. The proposed load-rating procedure is based on an extensive review of load-rating procedures and design practices, experimental data, and theoretical investigations. The proposed method does not include a rating factor for cover depth. However, the design cover depth is required to be checked during the initial design stage to ensure structural stability. New capacity reduction factors are introduced for culvert wall and seam, which require different appraisals for wall and seam during annual inspections. The effect of external live loads is not included in the proposed load-rating procedure for deep culverts and for culverts subjected to low live load stresses. Field data from 39 in-service culverts showed that the proposed load-rating procedure is effective in evaluation of the existing condition of culverts.

Evaluation of an Existing Steel Frame Building against Progressive Collapse

The internal forces increase in structural components neighbouring a member, usually a column, removed or destroyed as a result of manmade or natural hazards, such as an explosion. If the additional internal forces created by an initial small or local structural failure can not be efficiently redistributed within the structure, damage spreads and partial or total collapse (progressive collapse) of the building occurs. Progressive collapse has been of an increasing concern in the structural engineering community, especially since the collapse of the World Trade Center towers in 2001. The terrorist attacks showed that well-designed and robust modern buildings can be susceptible to progressive collapse. The Ronan Point collapse of 1968 in London, and the bombing of the Alfred P. Murrah building in Oklahoma City in 1996 are the most publicized examples of progressive collapse [1]. Therefore, it is necessary to design of buildings to resist progressive collapse. In this study, progressive collapse performance of an actual building was investigated. The Ohio Student Union building, located on the Ohio State University campus, was also tested by physically removing four first story columns from one of the long perimeter frames prior to buildings scheduled demolition. Our field experiments and analytical studies provide both practical and fundamental information on the collapse response of an existing building with a regular structural configuration. A commercially available computer program, SAP2000 was used to model and analyze the building following the General Services Administration (GSA, 2003) guidelines. The elastic static and nonlinear dynamic analysis results are presented and their implications are discussed.

Traditional Turkish Masonry Monumental Structures and their Earthquake Response

Many historical and new masonry minarets were damaged or collapsed during the 1999 earthquakes in Kocaeli and Duzce, Turkey. These and other recent earthquakes not only caused loss of property but also loss of many lives. The structural failures and resulting casualties have led to discussion and investigation of potential reasons for poor seismic performance of masonry minarets. The primary goal of this study is to review the construction practices for historical and new masonry minarets in Turkey and to discuss the seismic damage observed in those structures. The architectural and structural properties of contemporary and historical Ottoman minarets and their components are presented. For example, a very old special technique for reinforcing and linking adjacent stone blocks with iron pieces in the vertical and horizontal directions is discussed. The structural damage examples are used to better understand the reasons for the observed failure mechanisms. It is concluded that the transition region between the square minaret boot and cylindrical body was most vulnerable to damage, and the iron clamps used in historical minarets effectively prevented structural damage.