CHAPTER 19 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS

Transcription

1 CHAPTER 19 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS 19.1 INTRODUCTION Chapter 18 of this book has presented a discussion of some regulations that are directly applicable to the geotechnical aspects of foundations. For example, Table 18.1 presents special inspection regulations for deep foundations. Likewise, for the sake of continuity, Sec has discussed regulations for foundations supported by expansive soil. This chapter will mainly deal with the other foundation regulations contained in Chapter 18 (Soils and Foundations) of the International Building Code. Topics will include general regulations for footings and foundations, foundations adjacent slopes, retaining walls, and geotechnical earthquake engineering GENERAL REGULATIONS FOR FOOTINGS AND FOUNDATIONS The main regulations for foundations in the International Building Code are located in Section 1808 (Foundations), Section 1809 (Shallow Foundations), and Section 1810 (Deep Foundations). Specific general regulations for foundations in the International Building Code are as follows: Design for capacity and settlement (Section ). This Code section states: Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. Design loads (Section ). This Code section requires that foundations be designed for the most unfavorable effects due to the combinations of loads. Vibratory loads (Section ). This Code section states: Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil. Shifting or moving soils (Section ). This Code section states: Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be carried to a sufficient depth to ensure stability Shallow Foundations The International Building Code requires that shallow foundations be built on undisturbed soil, compacted fill, or CLSM material (Section ). During construction, it is common for loose soil or 19.1

2 INTERNATIONAL BUILDING CODE debris to be knocked into the footing excavations during the construction process or during the installation of the steel reinforcement. It is important that prior to placing concrete, the footings be cleaned of loose debris so that the foundation will bear on undisturbed soil or compacted fill. In terms of the top and bottom surfaces of shallow foundations, the International Building Code states (Section ): The top surface of footings shall be level. The bottom surface of footings shall be permitted to have a slope not exceeding one unit vertical in 10 units horizontal (10-percent slope). Footings shall be stepped where it is necessary to change the elevation of the top surface of the footing or where the surface of the ground slopes more than one unit vertical in 10 units horizontal (10-percent slope). The International Building Code also states that the minimum depth of shallow footings below the undisturbed ground surface shall be 12 in. (305 mm) and that the foundations be protected from frost (Sections and ). Regulations for footings on granular soils are as follows: Location of footings. Footings on granular soil shall be so located that the line drawn between the lower edges of adjoining footings shall not have a slope steeper that 30 degrees (0.52 rad) with the horizontal, unless that material supporting the higher footing is braced or retained or otherwise laterally supported in an approved manner or a greater slope has been properly established by engineering analysis Deep Foundations Deep foundations have been covered in Secs. 5.4, 6.3, 6.4, 16.2, and 16.3 of this book. In terms of the general requirements for deep foundations, the International Building Code states: Section Deep foundations. Where deep foundations will be used, a geotechnical investigation shall be conducted and shall include all of the following, unless sufficient data upon which to base the design and installation is otherwise available: 1. Recommended deep foundation types and installed capacities. 2. Recommended center-to-center spacing of deep foundation elements. 3. Driving criteria. 4. Installation procedures. 5. Field inspection and reporting procedures (to include procedures for verification of the installed bearing capacity where required). 6. Load test requirements. 7. Suitability of deep foundation materials for the intended environment. 8. Designation of bearing stratum or strata. 9. Reductions for group action, where necessary. In terms of determining the allowable load, the International Building Code states in Section : The allowable axial and lateral loads on a deep foundation element shall be determined by an approved formula, load tests or method of analysis. For additional details on the design and construction of deep foundations, see Section 1810 of the International Building Code FOUNDATIONS ADJACENT SLOPES There are very few regulations in the International Building Code for slope stability. As discussed in Chap. 10 of this book, slope stability is an important part of geotechnical and foundation engineering. In order to assess the safety of a slope, the geotechnical engineer will need to perform a slope stability analysis. The slope stability analysis should include likely changes that will develop during and after the proposed construction, such as a rise in the groundwater table that would decrease the factor

3 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS 19.3 of safety of the slope. As discussed in Chap. 10, the minimum acceptable factor of safety for permanent slopes is 1.5. A lower factor of safety may be acceptable for temporary slopes. In general, the main regulation in the International Building Code (Section ) states that permanent fill slopes and permanent cut slopes shall not be steeper than one unit vertical in two units horizontal (50-percent slope). Another regulation applies to minimum foundation setback, which will be discussed later in this section. Simply having a maximum slope inclination of 50 percent with minimum foundation setbacks will not insure the safety of a site. The geotechnical engineer should perform slope stability analyses, such as those presented in Chap. 10 of this book, to determine the factor of safety of the slope and evaluate the potential for lateral movement. When subjected to seismic shaking, the stability of slopes is reduced; and geotechnical earthquake engineering analyses for slopes should be performed, as indicated in Sec of this book. Section of the International Building Code deals with foundation setbacks for slopes. This section of the International Building Code makes reference to Figure , which has been reproduced in this book as Figure Section of the International Building Code is reproduced below: Section Foundations on or adjacent to slopes. The placement of buildings and structures on or adjacent to slopes steeper than one unit vertical in three units horizontal (33.3-percent slope) shall comply to Sections through Section Building clearance from ascending slopes. In general, buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failures. Except as provided for in Section and Figure [see Figure 19.1], the following criteria will be assumed to provide this protection. Where the existing slope is steeper than one unit vertical in one unit horizontal (100-percent slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees (0.79 rad) to the horizontal. Where a retaining wall is constructed at the toe of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope. Section Foundation setback from descending slope surface. Foundations on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lateral support for the foundation without detrimental settlement. Except as provided for in Section and Figure [see Figure 19.1], the following setback is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope. Section Alternate setback and clearance. Alternate setbacks and clearances are permitted, subject to the approval of the building official. The building official shall be permitted to require a geo - technical investigation as set forth is Section Section Alternate setback and clearance. Where setbacks or clearances other than those required in Section are desired, the building official shall be permitted to require a geotechnical investigation by a registered design professional to demonstrate that the intent of Section would be satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material. FIGURE 19.1 Foundation clearances from slopes. (From the International Building Code.)

4 INTERNATIONAL BUILDING CODE As previously mentioned, the International Building Code requires that both fill and cut slopes have maximum inclinations of one unit vertical in two units horizontal (50 percent slope). Thus for most slopes, the discussion in Section and dealing with slopes steeper than 1 unit vertical in 1 unit horizontal (100-percent slope) will not be applicable. For the usual situation of a 2:1 (50-percent slope) or flatter slope, the setback requirements will be as shown in Figure (i.e. Figure 19.1 in this book). As shown in Figure 19.1, the setback for structures at the toe of the slope is easy to determine and simply consists of a horizontal distance at least the smaller of H/2 and 15 ft [4.6 m], where H = height of the slope. At the top of the slope, the required setback is more complicated. The horizontal setback is measured from the face of the footing to the face of the slope and must be at least the smaller of H/3 and 40 ft [12 m]. If, because of property size constraints, the building must be close to the top of slope, then the perimeter footing can be simply deepened in order to meet the requirements of Figure Note that as mentioned in the earlier discussion, there is no building code regulation for a minimum factor of safety for slope stability. Nevertheless, the geotechnical engineer should evaluate the stability of slopes that will potentially impact the proposed development RETAINING WALLS Retaining walls have been covered in Chap. 11 and Sec of this book. The main regulations in the International Building Code for retaining walls are Section 1610 (Soil Lateral Loads) and Section 1807 (Foundation Walls, Retaining Walls and Embedded Posts and Poles). Table 19.1 presents lateral soils loads for the design of foundation walls and retaining walls per the International Building Code. Concerning these lateral soil loads, the International Building Code states: Section General. Foundation walls and retaining walls shall be designed to resist lateral soil loads. Soil loads specified in Table [see Table 19.1] shall be used as the minimum design lateral soil loads unless determined otherwise by a geotechnical investigation in accordance with Section Foundation walls and other walls in which horizontal movement is restricted at the top shall be designed for at-rest pressures. Retaining walls free to move and rotate at the top shall be permitted to be designed for active pressure. Design lateral pressure from surcharge loads shall be added to the lateral earth pressure load. Design lateral pressure shall be increased if soils at the site are expansive. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections and Exception: Foundation walls extending not more than 8 feet (2438 mm) below grade and laterally supported at the top by flexible diaphragms shall be permitted to be designed for active pressure. Although the Code (see Table 19.1) allows the use of clayey soils (i.e. GC, SM-SC, SC, ML, ML- CL, and CL) as backfill materials, clayey soils should generally not be used as retaining wall backfill material because of the following reasons: Predictable behavior. Import granular backfill generally has a more predictable behavior in terms of the earth pressure exerted on the wall. Expansive soil forces. Expansive soil related forces would not be generated by clean granular soil. However, if clay backfill is used, the seepage of water into the backfill could cause swelling pressures well in excess of the at-rest values listed in Table Excessive rotation of the top of wall. As indicated in Table 11.1 of this book, the rotation Y/H (where Y = wall displacement and H = height of wall) to reach the active state for dense cohesionless soil is , while the value of Y/H is 0.02 for soft cohesive soil. Hence, given a wall of the same height, the top of the wall will need to move horizontally about 40 times more for soft cohesive backfill as compared to dense granular backfill in order to reach the active state.

5 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS 19.5 TABLE 19.1 Lateral Soil Load Description of backfill material c Unified soil classification Design lateral soil load a (pound per square foot per foot of depth) Active pressure At-rest pressure Well-graded, clean gravels; gravel-sand mixes GW Poorly graded clean gravels; gravel-sand mixes GP Silty gravels, poorly graded gravel-sand mixes GM Clayey gravels, poorly graded gravel-and-clay mixes GC Well-graded, clean sands; gravelly sand mixes SW Poorly graded clean sands; sand-gravel mixes SP Silty sands, poorly graded sand-silt mixes SM Sand-silt clay mix with plastic fines SM-SC Clayey sands, poorly graded sand-clay mixes SC Inorganic silts and clayey silts ML Mixture of inorganic silt and clay ML-CL Inorganic clays of low to medium plasticity CL Organic silts and silt clays, low plasticity OL Note b Note b Inorganic clayey silts, elastic silts MH Note b Note b Inorganic clays of high plasticity CH Note b Note b Organic clays and silty clays OH Note b Note b For SI: 1 pound per square foot per foot of depth = kpa/m. 1 foot = mm. a Design lateral soil loads are given for moist conditions for the specific soils at their optimum densities. Actual field conditions shall govern. Submerged or saturated soil pressures shall include the weight of the buoyant soil plus the hydrostatic loads. b Unsuitable as backfill material. c The definition and classification of soil materials shall be in accordance with ASTM D 2487 (Unified Soil Classification System). Source: Table of the International Building Code. Drainage system. Retaining walls usually are constructed with drainage systems to prevent the buildup of hydrostatic water pressure on the retaining wall. The drainage system will be more effective if highly permeable soil, such as clean granular soil, is used instead of clayey backfill. Frost action. If freezing temperatures prevail, the backfill soil can be susceptible to frost action, where ice lenses will form parallel to the wall. Backfill soil consisting of clean granular soil and the installation of a drainage system at the heel of the wall will be much more effective in preventing frost action then using clayey backfill. Additional regulations concerning retaining walls are presented in Section 1807 of the International Building Code. Concerning the design of retaining walls, the International Building Code states: Section General. Retaining walls shall be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift. Where a keyway is extended below the wall base with the intent to engage passive pressure and enhance sliding stability, lateral soil pressures on both sides of the keyway shall be considered in the sliding analysis. Section Design lateral soil loads. Retaining walls shall be designed for the lateral soil loads set forth in Section 1610 [see Table 19.1]. Section Safety factor. Retaining walls shall be designed to resist the lateral action of soil to produce sliding and overturning with a minimum safety factor of 1.5 in each case. The load combinations of Section 1605 shall not apply to this requirement. Instead, design shall be based on 0.7 times nominal earthquake loads, 1.0 times other nominal loads, and investigation with one or more variable loads set to zero. The safety factor against lateral sliding shall be taken as the available soil resistance at the base of

6 INTERNATIONAL BUILDING CODE the retaining wall foundation divided by the net lateral force applied to the retaining wall. Exception: Where earthquake loads are included, the minimum safety factor for retaining wall sliding and overturning shall be GEOTECHNICAL EARTHQUAKE ENGINEERING Introduction Geotechnical earthquake engineering has been covered in Chaps. 13 and 14 of this book. This last section presents a discussion of the role of building codes in geotechnical earthquake engineering. The geotechnical engineer should always review local building codes and other regulatory specifications that may govern the seismic design of the project. These local requirements may be more stringent than the regulations contained in the International Building Code. Types of information that could be included in the building code or other regulatory documents are as follows: 1. Earthquake Potential. Local building requirements may specify the earthquake potential for a given site. The seismic potential often changes as new earthquake data is evaluated. For example, as discussed in Sec , one of the main factors that contributed to the damage at the Port of Kobe during the Kobe Earthquake was that the area had been previously considered to have a relatively low seismic risk; hence the earthquake design criteria was less stringent than in other areas of Japan. 2. General Requirements. The building code could also specify general requirements that must be fulfilled by the geotechnical engineer. For example, the International Building Code states the geotechnical investigation shall include the following items (Section ): a. The determination of lateral pressures on foundation walls and retaining walls due to earthquake motions. b. The potential for liquefaction and soil strength loss evaluated for site peak ground accelerations, magnitudes and source characteristics consistent with the design earthquake ground motions. Peak ground acceleration shall be permitted to be determined based on a site- specific study taking into account soil amplification effects. c. An assessment of potential consequences of liquefaction and soil strength loss, including estimation of differential settlement, lateral movement, lateral loads on foundations, reduction in foundation soil-bearing capacity, increases in lateral pressures on retaining walls and flotation of buried structures. d. Discussion of mitigation measures such as, but not limited to, ground stabilization, selection of appropriate foundation type and depths, selection of appropriate structural systems to accommodate anticipated displacements and forces, or any combination of these measures and how they shall be considered in the design of the structure. 3. Detailed Analyses. The building code could also provide detailed seismic analyses. For example, Table 19.2 presents data that can be used to determine the site class definition per the International Building Code. The site class is based on the average condition of the material that exists at the site from ground surface to a depth of 100 ft (30 m). The best site class is class A, consisting of hard rock, and the worst site class is class F, where there are soil profiles that may liquefy during the earthquake or there are soft soils that can increase the peak ground acceleration (see Sec of this book). If the ground surface will be raised or lowered by grading operations, then the site class analysis should be based on the final as-built conditions. As indicated in Table 19.2, the selection of the site class is based on the material type and engineering properties, such as the shear wave velocity, standard penetration test values, and the undrained shear strength.

7 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS 19.7 Profiles containing distinctly different soil and/or rock layers should be subdivided into layers with the average conditions in the upper 100 feet (30 m) of the profile based on the thickness of the individual layers. Equations (16-40 to 16-43) in the International Building Code can be used to calculate average values when there are distinctly different soil and/or rock layers at the site. The procedure for determining the site class is as follows: 1. Site class F: Start with the four categories listed under site class F (see Table 19.2). If the site meets any one of these four categories, then the site is designated as site class F. 2. Site class E: If a site is not a site class F, then check to see if the site meets the criteria for the definition of site class E in Table 19.2, i.e. a soft clay layer of more that 10 feet in thickness meeting the plasticity index, moisture content, and undrained shear strength criteria. 3. Site classes C, D, and E: If a site does not conform to the two previous items, then determine the average shear wave velocity, standard penetration resistance, and/or the undrained shear strength. As indicated in Table 19.2, site class C has the best soil properties (i.e. very dense soil), while site class E has poor soil properties (i.e. soft soil profile). Engineering properties of the soil are used to evaluate the site class as follows: Shear Wave Velocity: The shear wave velocity can be measured in situ by using several different geophysical techniques, such as the uphole, down-hole, or cross-hole methods (see Sec. 2.7 of this book). When using the shear wave velocity, it is best to use V 1s, (ft/s), which is corrected for the overburden pressure (see Eq. 6.9, Day (2002), Geotechnical Earthquake Engineering Handbook). Standard Penetration Test (SPT): The International Building Code states that the standard penetration resistance (ASTM D 1586), as directly measured in the field without corrections, should be used for Table However, it is best to use the SPT values that are corrected for both sam- TABLE 19.2 Site Class Definitions Average Properties in Top 100 feet* Soil Shear wave velocity, Standard penetration Soil undrained shear Site Class Profile Name V 1s, (ft/s) resistance, (N 1 ) 60 strength, s u, (psf) A Hard rock V 1s > 5,000 N/A N/A B Rock 2,500 < V 1s 5,000 N/A N/A C Very dense soil and 1,200 < V 1s 2,500 (N 1 ) 60 > 50 s u > 2,000 soft rock D Stiff soil profile 600 V 1s 1, (N 1 ) ,000 s u 2,000 E Soft soil profile V 1s < 600 (N 1 ) 60 < 15 s u < 1,000 E F Any profile with more than 10 feet of soil having the following characteristics: plasticity index PI > 20, moisture content w 40%, and undrained shear strength s u < 500 psf Any profile containing soils having one or more of the following characteristics: 1. Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils, quick and highly sensitive clays, collapsible weakly cemented soils. 2. Peats and/or highly organic clays (H > 10 feet of peat and/or highly organic clay, where H = thickness of soil). 3. Very high plasticity clays (H > 25 feet with plasticity index PI > 75). 4. Very thick soft/medium stiff clays (H > 120 feet). Note: *See Section for further details. For SI: 1 foot = mm, 1 square foot = m 2, 1 pound per square foot = kpa. N/A = Not applicable Source: Table of the International Building Code.

8 INTERNATIONAL BUILDING CODE pling procedures and overburden pressure, i.e. (N 1 ) 60 values (see Eq. 2.5 in this book), because the (N 1 ) 60 value is a more reliable indicator of the density of granular soil than uncorrected SPT values. Undrained Shear Strength: The undrained shear strength has been discussed in Sec of this book. The International Building Code states that the undrained shear strength (s u ) is to be determined in accordance with ASTM D 2166 (unconfined compression test) or ASTM D 2850 (unconsolidated-undrained triaxial compression test). 4. Site classes A and B. The rock categories A and B should not be used if there are more than 10 feet (3 m) of soil between the rock surface and the bottom of the foundation. The International Building Code provides figures (e.g. Figure ) that delineate 0.2-second spectral acceleration values. These spectral accelerations are considered to be applicable for firm rock sites (i.e. site class B material). In the discussion printed on Figure of the International Building Code, there is information on how to obtain coefficients that allow the user to adjust the spectral response acceleration for different site classes. The structural engineer will use the spectral response acceleration in the seismic design of the building Code Development One of the most important methods of code development is to observe the performance of structures during earthquakes. There must be a desire to improve conditions and not simply accept the death and destruction from earthquakes as inevitable. Two examples of the impact of earthquakes on codes and regulations are as follows: 1. March 10, 1933 Long Beach earthquake in California. This earthquake brought an end to the practice of laying brick masonry without reinforcing steel. Prior to this earthquake, the exterior walls of building were often of brick, or in some cases hollow clay tile. Wood was used to construct the roofs and floors that were supported by the brick walls. This type of construction was used for schools and the destruction to these schools was some of the most spectacular damage during the 1933 Long Beach Earthquake. Fortunately, the earthquake occurred after school hours and a catastrophic loss of life was averted. However, the destruction was so extensive and had such dire consequences that the California legislature passed the Field Law on April 10, This law required that all new public schools be constructed so that they are highly resistant to earthquakes. The Field Law also required that there be field supervision during the construction of schools. 2. February 9, 1971 San Fernando Earthquake in California. Because of the damage caused by this earthquake, building codes were strengthened and the California legislature passed the Alquist Priolo Special Studies Zone Act in The purpose of this act is to prohibit the construction of structures for human occupancy across the traces of active faults. The goal of this legislation is to mitigate the hazards caused by fault rupture. There has also been a considerable amount of federal legislation in response to earthquake damage. For example, the Federal Emergency Management Agency (1994) states: At the federal level, there are two important pieces of legislation relating to local seismic hazard assessment. These are Public Law , amended in 1988 as the Stafford Act, which establishes basic rules for federal disaster assistance and relief, and the Earthquake Hazards Reduction Act of 1977, amended in 1990, which establishes the National Earthquake Hazards Reduction Program (NEHRP). The Stafford Act briefly mentions construction and land use as possible mitigation measures to be used after a disaster to forestall repetition of damage and destruction in subsequent events. However, the final rules promulgated by the Federal Emergency Management Agency (FEMA) to implement the Stafford Act (44 CFR Part 206, Subparts M and N) require post-disaster state-local hazard mitigation plans to be prepared as a prerequisite for local governments to receive disaster assistance funds to repair and restore damaged or destroyed public facilities. Under the regulations implementing Section 409 of the Stafford

9 INTERNATIONAL BUILDING CODE REGULATIONS FOR FOUNDATIONS 19.9 Act, a city or county must adopt a hazard mitigation plan acceptable to FEMA if it is to receive facilities restoration assistance authorized under Section 406. The overall purpose of the National Earthquake Hazards Reduction Act is to reduce risks to life and property from earthquakes. This is to be carried out through activities such as: hazard identification and vulnerability studies; development and dissemination of seismic design and construction standards; development of an earthquake prediction capability; preparation of national, state and local plans for mitigation, preparedness and response; conduct basic and applied research into causes and implications of earthquake hazards; and, education of the public about earthquakes. While this bears less directly on earthquake preparation for a particular local government, much of the growing body of earthquake-related scientific and engineering knowledge has been developed through NEHRP funded research, including this study Limitations of Building Codes Common limitations of building codes are that they may not be up to date or may underestimate the potential for earthquake shaking at a particular area. In addition, the building codes may not be technically sound or they may contain loopholes that can be exploited by developers. For example, in terms of the collapse of structures caused by the Chi-chi Earthquake in Taiwan on September 21, 1999, Hands (1999) states: Why then were so many of these collapses occurring in 12-story buildings? Was it, as the local media suggested, a result of seismic waves hitting just the right resonant frequency to take them out? Professor Chern dismisses this as bordering on superstition. Basically Taiwan has a lot of 12-story buildings, especially central Taiwan. You hardly see any 20-story high-rises in those areas hit by the quake. The reason for this is that buildings under 50 meters in height don t have to go to a special engineering committee to be approved, so 12 stories is just right. Approval of a structure by qualified structural engineers, and correct enforcement of the building codes, is the crux of the problem, Chern believes. Another example is the Kobe Earthquake in Japan on January 17, It was observed that a large number of 20-year and older high-rise buildings collapsed at the fifth floor. The cause of these building collapses was apparently an older version of the building code that allowed a weaker superstructure beginning at the fifth floor. Even with a technically sound building code without loopholes, there could be many other factors that are needed to produce earthquake-resistance structures, as follows: 1. Qualified engineers. There must be qualified structural and geotechnical engineers that can prepare seismic designs and building plans. However, the availability of a professional engineering group will not insure adequate designs. For example, concerning the collapse of structures caused by the Chi-chi Earthquake in Taiwan on September 21, 1999, Hands (1999) states: Professor Chern is particularly damning of some of his fellow engineers, and the professional associations to which they belong. In 1997 we had 6,300 registered civil engineers. Three hundred of them are working in their own consultancies, and 2,800 are employed by building contractors. That means that the other 3,300, or more than half, are possibly renting their licenses. Asked to explain further, Chern said that it was common practice for an engineer to rent his engineer s license to a building contractor, so that the contractor could then claim the architectural drawings had been approved by a qualified engineer, without the engineer even having seen the blueprints. Chern sees the problem as stemming from the way the engineers professional associations are run. When they elect a president of the association, the candidate who favors license-renting will get all the votes from those people and win the election, and then he won t be willing to do anything about the problem. 2. Permit process. After the engineers have prepared the structural plans and specifications, they must be reviewed and approved by the governing agency. The local jurisdiction should have qual-

10 INTERNATIONAL BUILDING CODE ified engineers that review the designs to ensure that proper actions are taken to mitigate the impact of seismic hazards, to evaluate structural and nonstructural seismic design and construction practices so that they minimize earthquake damage in critical facilities, and to prevent the total collapse of any structure designed for human occupancy. An important aspect of the permit process is that the governing agency has the power to deny construction of the project if it is deemed to be below the standard of practice. 3. Inspection during construction. Similar to the permit process, there must be adequate inspection during the construction of the project to ensure that the approved building plans and specifications are being followed. Any proposed changes to the approved building plans and specifications would have to be reviewed by the governing agency. The project engineers should issue final reports in order to certify that the structure was built in conformance with the approved building plans. 4. Construction industry. An experienced workforce that will follow the approved plans and specifications is needed during construction. In addition, there must be available materials that meet project requirements in terms of quality, strength, and the like. An example of lax construction is as follows (Hands, 1999): Professor Chern said the construction industry is riddled with problems from top to bottom. Even the concrete has problems. In Taiwan we have quite narrow columns with a lot of rebar in them. This makes it difficult to pour the concrete and get it through and into all the spaces between the bars. Just imagine it you usually have a small contractor doing the pouring, maybe five men with one pumping car, with two doing the vibrating. They pour 400 cubic meters in one day, and only make NT$5,000 for one morning s work. It s also a manpower quality problem, he said. You have low quality workers on low pay, so everything is done quickly. Very good concrete is viscous, so they add water to ready-mixed concrete to make it flow better. But then you get segregation of the cement and aggregate, and the bonding of the concrete and rebar is poor. We ve seen that in a lot of the collapsed buildings. Adding water is the usual practice, Chern said. They even bring along a water tank for the purpose. And although structural engineers are wont to criticize architects for designing pretty buildings that fall down in quakes, perhaps the opposite extreme should also be avoided. If I had my way all buildings would be squat concrete cubes with no windows, joked Vincent Borov, an engineer with the EQE team.

11 APPENDICES

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